Field of the invention

The present invention relates to a method for profiling an outer surface of the outer ear. The present invention further relates to an ear profiler for profiling an outer surface of the outer ear.

Background of the invention

Sensorineural hearing loss often requires a hearing aid device for alleviation of its symptoms. Hearing aids can be customised to match the hearing loss, physical features and lifestyle of the patient. The amount of benefit a hearing aid delivers is in large part dependent on the fitting of the hearing aid in the outer ear of the patient. As the anatomy of an ear can vary to a great extent, the size and shape of the hearing aid is advantageously customised to the individual’s ear, to provide for a comfortable and secure fit therein, as wearing aids should not cause pain. Additionally, specific functionality of the hearing aid imposes varying requirements, for example regarding the sealing tightness of the hearing aid in an ear canal.

Customisation is especially important for hearing aids comprising earpieces that are to be placed in the central portion of the auricle of an ear, called the concha, and those that are partly or fully placed in the ear canal. The increasing popularity of invisible hearing aids (IIC), that are entirely positioned in the ear canal, emphasises the need for customisation.

Usually, a physical cast of the outer ear is created by injecting silicone material into an ear, waiting for the silicone to harden, after which the cast can be provided to a hearing aid manufacturer. This process is slow, as the silicone needs time to harden, expensive, as new material is required for each cast, inconsistent, as air bulbs and cerumen can influence the shape of the cast, potentially unpleasant for the patient, and injecting silicone risks affecting the ear drum and can cause infections.

OCT, or optical coherence tomography, is an imaging technique that uses low- coherence light to determine positions of light- reflecting media, such as tissue. US7949385B2 discloses an apparatus for creating a representation of a three-dimensional contour of an ear canal comprising an OCT device which can provide high-resolution cross-sectional imaging. The device is passed through a catheter that is inserted into the ear canal to be imaged, after which the device is moved along the surfaces of the ear canal for imaging. US8135453B2 discloses a similar OCT configuration.

However, a disadvantage of these techniques is that the shape of the catheter influences the measured contour. The device must be guided as accurately as possible, such that the actual scanning path conforms with a predetermined scanning path for image reconstruction from OCT data. In case the catheter is deformed, and/or if the actual scanning path does not conform with the predetermined scanning path, the measured contour may deviate from the actual ear part.

Further, while being moved through the catheter, the OCT device only images ear parts perpendicular to the catheter surface, such that the surface imaged by the OCT device from a certain point is limited. As a result, the device needs to be moved along the surface to be imaged to determine a contour of the ear part and, for example, for imaging the ear canal, the catheter needs to be placed in the ear canal. Similarly to a physical cast, the shape of the ear canal may be deformed due to the insertion of a catheter, such that the measurement does not represent the actual non-deformed shape of the outer surface of the outer ear.

The imaged surface is constrained by the shape of the catheter. For measuring parts of the outer ear, US7949385B2 requires a curved catheter such that the scan path closely follows the ear shape.

Further, for determining the exact position of the OCT device with respect to the ear, frequent calibration of the position of the catheter with respect to the ear and of the OCT device with respect to the catheter is necessary.

Movement of the device with respect to the ear may cause measurement imprecisions due to movements with respect to a calibrated position. This is especially important as the device is actuated at an outer end of the catheter, while the device may be located at an opposite outer end. Curvature of the catheter may cause uneven friction along the length of the catheter, such that the device moves unevenly.

Object of the invention

It is therefore an object of the present invention to provide an ear profiler that lacks one or more of the drawbacks mentioned above, or at least to provide an alternative ear profiler.

The present invention

The present invention provides a method for profiling an outer surface of the outer ear according to claim 1. Profiling, as used herein, is to be understood as determining a profile, in particular a structural profile.

The method relies on an OCT device that, with an objective, emits a measurement beam and receives a reflected part of the measurement beam to measure a measurement signal on the basis of interference between the reflected part of the measurement beam and a reference beam.

Profiling an outer surface of the outer ear can be performed with the OCT device by emitting a low-coherent light beam with a light source. The light beam may be split by a beam splitter in a reference beam and a measurement beam. The reference beam may be reflected by a reference reflector as a reflected reference beam. The reference beam and reflected reference beam together will be referred to hereinafter as reference arm.

The method further relies on at least two objectives comprising a first objective and a second objective that are configured to be positioned in a measurement position outside the ear. The term objective, as used herein, is to be understood as the optical arrangement closest to the surface of the outer ear that may comprise a single lens, mirror, and/or combinations of several optical elements.

The first objective is optically connectable to the OCT device and the second objective may be optically connectable to the OCT device such that the measurement beam may be emitted with the first objective as a first measurement beam when the first objective is optically connected to the OCT device and/or the measurement beam may be emitted with the second objective as a second measurement beam when the second objective is optically connected to the OCT device. The first measurement beam may be emitted towards a first portion, respectively the second measurement beam towards a second portion, of the outer surface of the outer ear, where a part of the respective measurement beam may be reflected. The reflected part of the first measurement beam, respectively the reflected part of second measurement beam, may then be received by the respective first objective or second objective to measure a respective first and/or second measurement signal.

Outer ear, as used herein, is to be understood as comprising the auricle and the ear canal. A measurement position outside the ear is to be understood as a position substantially outside of the ear canal, for example completely outside of the ear canal, such as at a distance from the ear canal of 0,5-100 mm, for example 1-25 mm.

By having a first and/or a second objective to emit the measurement beam, properties of the measurement beam may be influenced, such as a measurement direction, depth focus, resolution, and a maximum measurement area of the measurement beam. By the objective, the measurement beam may be guided more precisely towards measurement points in the respective portion of the outer ear from the respective measurement position. The first objective may have a numerical aperture adapted to the first portion, resulting in a desired depth focus and/or resolution of the first measurement beam. The second objective may have a numerical aperture adapted to the second portion, resulting in a desired depth focus and/or resolution of the second measurement beam. Therewith, the first objective may be configured to measure a measurement area adapted to the first portion of the outer surface of the outer ear and/or the second objective may be configured to measure a measurement area adapted to the second portion of the outer surface of the outer ear.

The respective measurement beam may be partially reflected by the outer surface of a single measurement point or multiple measurement points in the respective portion of the outer ear as a reflected measurement beam. The term reflected, as used herein, is to be understood as comprising backscattered. The measurement beam and the reflected measurement beam together will be referred to hereinafter as measurement arm.

The reflected measurement beam may then be received by the first and/or second objective and be guided back towards the OCT device.

The OCT device may comprise a detector configured to receive the reflected reference beam and the reflected part of the measurement beam, for example as a combined light beam to measure a measurement signal on the basis of interference between the reflected reference beam and the reflected part of the measurement beam, such that the measurement signal is representative for a profile of the outer surface of a portion of the outer ear. The OCT device may then output the detector data in raw or modified form as measurement signal.

The measurement signal may be measured as first measurement signal with the first objective and/or as second measurement signal with the second objective.

An optical path length of the reference arm may be known, for example on the basis of optical characteristics of the OCT device. The optical path length of the reference arm may be a distance travelled by the reference beam between the beam splitter splitting the light beam into a measurement beam and reference beam, and the reflector, and back to the beam splitter combining the reflected part of the measurement beam and the reflected reference beam. The optical path length of the reference arm may be adjustable, for example by adjusting a position of the reference reflector. As interference between the reflected reference beam and the reflected part of the measurement beam may occur only when their optical path lengths are similar, in particular when an optical path length difference between the reference arm and the measurement arm is less than a predetermined imaging depth of the OCT device, and as the optical path length of the reference arm and the imaging depth of the OCT device may be known before measuring, a structural profile of the outer ear can be determined reliably on the basis of the interference.

The outer ear has a complex structure, such that measuring a first measurement signal with the ear profiler using one objective may be insufficient to create a 3-dimensional model of the outer surface of the outer ear. In particular, due to the complex structure of the outer ear, it has been found that specific ear parts, such as the tragus or antitragus, may obstruct the measurement beam when the measurement signal is measured from a measurement position outside the ear.

Furthermore, the outer ear consists of structural elements that are very different. For example, the ear canal is relatively narrow, even and deep, while the auricle is much wider and has more relief. Therefore, a required numerical aperture, direction and scan area of a measurement beam, in particular for providing an measurement signal on the basis of interference, may be completely different for each structural element.

A first measurement signal is measured from a first measurement position outside the ear with the first objective and a second measurement signal is measured from a second measurement position outside the ear with a second objective, such that obstructions of the measurement beam may be avoided, and measurement signals measured with the respective objectives can be processed to create a three-dimensional model of the outer surfaces of the outer ear. The first and second objective may emit the measurement beam differently, as optical parameters of the first objective and second objective, such as numerical aperture, scan area and measurement direction may be different such that different portions of the outer ear may be measured reliably.

By having a first and a second objective, different types of measurements may potentially be performed, for example one or more point measurements on the first portion, and a larger area on the second portion, or vice versa. The first objective and/or the second objective may comprise a movable element to guide the measurement beam in multiple measurement directions from the measurement position, resulting in a measurement area adapted to the first portion, respectively second portion, of the outer ear. For example, a first and/or a second objective comprising a galvo scanner or movable mirror may be used, such that an outer surface of a relatively large portion of the outer ear may be measured at once from the first and/or the second measurement position.

In addition to the first objective and the second objective, additional objectives may be used for measuring additional measurement signals.

The usage of OCT enables profiling of the outer surface of the outer ear with high resolution and within a short timeframe. A precise three-dimensional model of the outer surface of the outer ear may be created, which can advantageously be used in many applications, such as the customisation of hearing aids to an individual patient.

As the measurement signal is measured with a first objective from a first measurement position and a second objective from a second measurement position, the outer surfaces of the outer ear may be profiled without movement of a device along substantially the whole outer surfaces. As such, there is no need for a predefined guiding catheter defining a scan path that substantially corresponds with the ear shape.

Furthermore, the first measurement signal and the second measurement signal may be related to each other, such that a three-dimensional model may be created without having a need for a guiding catheter. By relating the first and second signals to each other, for example by creating a first model of the first portion and a second model of the second portion, and combining the first model and the second model, a three-dimensional model may be created with the respective measurement signals from the respective objectives. Further, the use of OCT allows to measure deeper layers, located underneath the outer surfaces of the first portion and/or second portion of the outer ear. As such, the type of material may be determined more reliably, and ear tissue may be differentiated from cerumen, hairs, or other objects. For example, the OCT device may be configured to measure a structure of tissue that, in the measurement direction, is located at least 0,2 mm behind the outer surface of the outer ear, such as at least 0,5 mm.

The method for profiling the outer ear according to the present invention may advantageously enable measurements of the outer surface of the outer ear that are highly accurate, faster, more repeatable and much less intrusive than prior techniques. The OCT device offers audiologists better infection control, less complication risks and a possibility for automation to speed up delivery of a hearing aid to a patient.

The first measurement signal measured by the OCT device may comprise multiple frequencies that may arise from optical interference between the reflected part of the measurement beam and a reference beam. The frequencies in the first measurement signal are related to the optical path length difference between the reference arm and measurement arm. The optical path length difference may represent the distance between a reference plane and the surface of interest, for example the outer ear. A surface of the outer ear close to the reference plane in the measurement direction may give rise to low frequencies in the first measurement signal, while a surface of the outer ear further from the reference plane in the measurement direction may give rise to higher frequencies in the first measurement signal.

The first measurement signal may be processed by decomposition of its frequencies, for example by performing a Fourier transform of the first measurement signal, such that, amongst others, a depth-resolved reflectivity profile i.e. a so-called A-scan of the outer surface of the ear in the measurement direction may be determined precisely.

The position of the amplitudes in the A-scan may be related to the distance of the surface of the ear in relation to the reference plane of the OCT device. The magnitudes of the amplitudes in the A-scan may, amongst others, be related to the reflective properties of the surface of the outer ear. A highly reflective outer surface of the outer ear may give rise to larger amplitudes than a less reflective outer surface. The reflectivity may, amongst others, also depend on ear tissue type and incident angle of the measurement beam.

As the properties of the respective objective and the position of the reference reflector may be known and/or predetermined, a profile of the first portion of the outer surface of the outer ear may be determined on the basis of the first measurement signal alone, such that normally no external distance references would be required for profiling the outer surface of the outer ear. Consequently, it is normally not required to perform calibration of a distance reference to the ear profiler before an outer ear can be measured. This is especially advantageous when multiple patients are measured subsequently.

Therefore, ear profiling using the ear profiler may provide for more precise measurements and provide a higher accuracy and repeatability of measurements compared to other techniques.

In an embodiment, the method comprises the step of providing the ear profiler. In an embodiment, the method comprises the step of optically connecting the first objective to the OCT device. The method may additionally comprise the step of optically connecting the first objective to the OCT device. In an embodiment, the second objective may be optically connected upon removal of the first objective, or the second objective may be connected to the OCT device without prior removal of the first objective in another embodiment.

In an embodiment, at least during the step of measuring the second measurement signal, the second objective is optically connected to the OCT device, wherein the step of measuring the second measurement signal comprises emitting with the second objective from the second measurement position a second measurement beam towards the outer surface of the outer ear and receiving a reflected part of the second measurement beam to measure the second measurement signal on the basis of interference between the reflected part of the second measurement beam and the reference beam.

When the second objective is optically connected to the OCT device, light beams, such as a second measurement beam from and/or a reflected part of the second measurement beam to the OCT device may be guided by the second objective. This way, a second measurement signal may be measured with the OCT device.

Further, the second measurement signal may be measured and/or processed similarly to the first measurement signal in this embodiment such that the advantages of measuring the first portion with the first objective may also apply to the step of measuring the second portion with the second objective.

In an additional or alternative embodiment, the ear profiler comprises a camera, and, at least during the step of measuring the second measurement signal, the second objective is optically connected to the camera.

The camera may be a camera configured to detect visible light and provide the second measurement signal on the basis of detected light, for example using a CCD or CMOS sensor. In particular, the camera may be a stereo camera. In an embodiment, the step of measuring the first measurement signal is performed with a main optical axis of the first objective in a first measurement direction and the step of measuring the second measurement signal is performed with a main optical axis of the second objective in a second measurement direction that is non-parallel to, for example not coaxially aligned with, the first measurement direction.

By measuring with the main optical axes of the first objective and the second objective in the first, respectively second measurement direction, the measured measurement signals may be representative for profiles of outer surfaces of larger portions of the outer ear. Additionally, the complex structure of the outer ear may be profiled better by having multiple measurement directions, as certain portions of the outer ear may be obscured by ear parts, such as the tragus, in the first measurement direction, but may be measured in the second measurement direction, or vice versa.

The first objective and/or second objective may be provided with physical support points for supporting the respective objective on a ground surface and/or on a part of the head, such as on the ear of a patient to be measured. This way, stable measurements may be performed and a better measurement signal may be measured Further, the first objective and/or the second objective may be aligned in the respective first and/or second measurement direction with the physical support points.

In the respective measurement position, the measurement beam may also be guided by the first objective and/or second objective in additional directions at an angle with respect to the first and/or second measurement direction. For example, the ear profiler and/or the objective may comprise a movable element, such as a galvo scanner or movable mirror for guiding the measurement beam along the first and/or second portion of the outer ear, while the main optical axis of the respective objective remains arranged in the respective first or second measurement direction. This way, the measurement beam may be guided towards multiple measurement points on the outer surface in the respective first or second portion of the outer ear.

The optical characteristics of the objective may define outermost additional directions, that, in use, define a measurement area between the outermost directions, for example with respect to the main optical axis. The optical characteristics of the objective may for example define four outermost directions to span a 2D measurement area for a single measurement position.

This way, by guiding the measurement beam in additional measurement directions, a relatively large first or second portion of the outer ear may be measured from the respective measurement position, such that the 3-dimensional model may represent a relatively large surface of the outer ear. In an embodiment, the step of processing the first measurement signal and the second measurement signal comprises the steps of determining a common reference point for the first model and the second model on the basis of; an overlap in the first model and the second model, representative for a partially overlapping surface in the first portion and the second portion of the outer ear; and/or a position tracking system for tracking a position of the ear profiler with respect to the outer ear; and/or a predetermined positional relation between the first measurement position and the second measurement position; and combining the first model and the second model in the common reference point.

The processing unit may be configured to perform these steps.

By having a common reference point, the first measurement signal and the second measurement signal and/or the first model and the second model may be interrelated more easily. For example, the first measurement position and/or the second measurement position may be determined on the basis of differences in perspective of the reference point in the first and second measurement signal.

The common reference point may be determined on the first portion and the second portion of the outer ear, or on another location, for example on the head of the patient or on an external reference. The common reference point may be an internal reference point in an overlap of the first portion and the second portion, represented in the first model and the second model, or be a predetermined positional relation known before the measurements. The common reference point may also be formed by a position tracking system, for example on the basis of the first measurement signal and the second measurement signal or on another input, such as a photograph of the ear or a signal from a sensor, such as a gyroscope.

In an embodiment, the step of processing the first measurement signal and the second measurement signal further comprises the steps of: defining the first measurement position and the second measurement position with respect to the common reference point; determining a positional difference between the first measurement position and the second measurement position and/or a rotational difference between the first measurement direction and the second measurement direction on the basis of the common reference point; and adjusting the first measurement model and/or the second measurement model on the basis of the positional difference and/or the rotational difference, for example by rotating and rescaling. A rotational difference may be determined by defining the respective measurement directions with respect to the common reference point, for example in terms of Euler angles.

In an embodiment, the first portion of the outer ear and the second portion of the outer ear partially overlap to form an overlapping surface. By having a first measurement signal and a second measurement signal representative for overlapping portions of the outer ear, the respective measurement signals may be related to each other on the basis of the overlapping surface.

In a further embodiment, the common reference point is determined on the overlapping surface.

In addition to a single common reference point, multiple common reference points may be determined. This way, the respective measurement positions may be defined more precisely. Additionally, when more than two measurements are performed, a first common reference point may be used for determining a positional difference between the first and second measurement position, while a second common reference point may be used for determining a positional difference between the second and a third measurement position.

In an embodiment, the step of processing the first measurement signal and the second measurement signal comprises the steps of correcting the respective measurement signals for distortion due to non-perpendicular incident angles of measurement beams on the outer surface of the outer ear and combining the corrected first measurement signal and the corrected second measurement signal to create a 3-dimensional model of the outer surfaces of the outer ear.

As respective measurement beams may be guided in specific directions by the respective objectives, multiple portions of the outer ear may be measured from a respective first or second measurement position. In this case, measurements may be performed in which a measurement beam guided by the objective may not be incident to the outer surface of the ear at a perpendicular angle, which may introduce spatial distortions in a created 3d-model. The respective measurement signal may be corrected on the basis of calibration routines.

In an embodiment, the first portion of the outer surface of the outer ear comprises a portion of the ear canal, and the second portion of the outer surface of the outer ear comprises a portion of the concha. The characteristics of the ear profiler, such as the use of a first objective and a second objective may be particularly advantageous in this application.

In a further embodiment, the first measurement direction is substantially parallel to the ear canal. This way, the respective measurement beams may not pass tissue before being reflected on an outer surface of the outer ear, which may deliver a better measurement signal, for example because the reflected measurement beam has not been weakened.

In an embodiment, the ear profiler further comprises a third objective. The third objective may be optically connectable to the OCT device, for example be releasably attachable to the OCT device.

This way, a third portion of the outer ear may be measured using specifically adapted objectives. In addition, additional objectives may be provided to further adapt properties of a light beam to the portion of the outer ear to be measured.

In a further embodiment, the third objective may be configured to be positioned in a third measurement position for measuring the middle or inner ear. The third measurement position may be in or outside of the ear.

The third objective may enhance depth focus and/or a maximum optical path length of the OCT device by guiding a light beam through the ear canal.

The method may further comprise the steps of: when the third objective is optically connected to the OCT device, emitting with the third objective a third measurement beam towards a surface of the middle or inner ear and receiving a reflected part of the third measurement beam to measure, on the basis of interference between the reflected part of the third measurement beam and the reference beam, a third measurement signal representative for a position of a surface of the middle or inner ear; and processing the third measurement signal to create a model of positions of the middle or inner ear.

In a further embodiment, the third measurement signal is measured repeatedly for measuring positional changes due to vibrations of the surface of the middle or inner ear.

Advantageously, a measurement of the outer ear may be performed first, after which a measurement of the middle and/or inner ear may also be performed with the same ear profiler. As such, a hearing care professional may offer an integrated ear measurement service such that hospital visits are no longer necessary.

The invention provides an ear profiler for profiling an outer surface of the outer ear, configured to provide a measurement signal representative for the profile of the outer surface of the outer ear, comprising an OCT device, to emit a measurement beam and to receive a reflected part of the measurement beam, and to provide an measurement signal on the basis of interference between the reflected part of the measurement beam and a reference beam; a first objective to be positioned in a first measurement position outside the ear, and optically connectable to the OCT device to emit a first measurement beam from the OCT device towards a first portion of the outer surface of the outer ear and to receive a reflected part of the first measurement beam to measure a measurement signal; a second objective to be positioned in a second measurement position outside the ear to measure a second measurement signal representative for a profile of a second portion of the outer surface of the outer ear; and a processing unit to process the first measurement signal to create a first model of the first portion, to process the second measurement signal to create a second model of the second portion, and to combine the first model and the second model to create a 3- dimensional model of the outer surfaces of the outer ear.

The ear profiler may be particularly suited for performing the method according to the invention. Similar advantages as with the method may be achieved with the ear profiler.

In an embodiment, the second objective is connectable to the OCT device, and the second measurement signal comprises a second measurement signal.

In an embodiment, the second objective is optically connectable to the OCT device to emit a second measurement beam from the OCT device towards the second portion and to receive a reflected part of the second measurement beam to measure the second measurement signal.

In an alternative or additional embodiment, the ear profiler comprises a camera, for example a stereo camera, to provide a camera signal on the basis of light reflected by the outer ear. In this embodiment, the second objective is optically connectable to the camera to guide light beams between the camera and the second portion of the outer ear for measuring the second measurement signal with the camera.

The camera may comprise a CCD or CMOS sensor. The camera may provide the camera signal on the basis of light reflected by the outer ear.

By having multiple objectives, measuring a second measurement signal may be performed using other optical systems in addition to OCT, such as a camera. This way, measurements may be adapted further to the portion of the outer ear. For example, the ear canal may advantageously be measured with high precision using the OCT device, while other parts of the outer ear may be measured using the camera to shorten measurement time.

In an embodiment, the ear profiler comprises a mount for releasable attachment of the first objective and/or the second objective, wherein the first objective and the second objective are optically connected to the OCT device when releasably attached to the mount.

The ear profiler may comprise a single mount, such that the first objective and the second objective are selectively connectable to the ear profiler. Alternatively, the ear profiler may comprise multiple mounts, such that the first objective and the second objective may be simultaneously optically connected the ear profiler.

In an embodiment provided with a camera, the second objective may be optically connected to the camera when releasably attached to the mount.

This way, the respective objective may be optically connected to the OCT device and/or the camera, respectively, by attaching it to the mount, and be optically disconnected from the OCT device and/or the camera, by detaching the respective objective from the mount.

Alternatively, the first objective and the second objective may be permanently attached to the ear profiler, for example on a single probe. This way, the first measurement position and the second measurement position are defined with respect to each other by their respective positions on the ear profiler.

In an embodiment, the first objective and the second objective are arranged at different locations within the ear profiler, such that the first measurement position and the second measurement position have a predetermined positional relation with respect to each other.

In an embodiment, the first objective is arranged to guide light beams in a first measurement direction, and wherein the second objective, is arranged to guide light beams in a second measurement direction that is non-parallel to the first measurement direction.

A main optical axis of the first objective may define a first measurement direction in which the first measurement beam is emitted and/or a main optical axis of the second objective may, define, a second measurement direction in which a second measurement beam is emitted, if the second objective is optically connectable to the OCT device.

In particular, the second measurement direction may be non-parallel to the first measurement direction, such as transverse to the first measurement direction, for example not coaxially aligned with the first measurement direction.

In an embodiment, the first objective is provided with physical support points to be arranged in a first measurement position to measure the first measurement signal in the first measurement direction and/or the second objective is provided with physical support points to be arranged in a second measurement position to measure the second measurement signal in the second measurement direction.

With physical support points, the respective objective may be stably arranged on a ground surface and/or on a part of the head in the respective measurement position to emit the respective measurement beam in the respective measurement direction more precisely. In an embodiment, the first objective has optical characteristics that are different from optical characteristics of the second objective. The optical characteristics, such as a field of view, may be different for the first and the second objective to measure different portions of the outer ear. For example, for measuring the concha, an area of 35 x 35 mm may be profiled, while for the ear canal, an area of 10 x 10 mm may be sufficient.

The first objective may be configured to measure a first portion of the outer ear that comprises a portion of the ear canal, and/or the second objective may be configured to measure a second portion of the outer ear that comprises a portion of the concha

In an embodiment, the first objective and/or the second objective are configured to guide the measurement beam in additional directions at an angle with respect to the first and/or second measurement direction. The ear profiler, the first objective and/or the second objective may comprise a movable element to move the respective measurement beam in additional direction with respect to the main optical axis of the respective objective.. This way, a relatively large portion may be measured., such that the 3-dimensional model may represent a relatively large surface of the outer ear.

The first objective and/or the second objective may be configured to guide the respective measurement beam in additional measurement directions towards multiple measurement points distributed over the respective first or second portion of the ear.

For example, the ear profiler may comprise a movable element such as a galvo scanner or movable mirror. The galvo scanner or movable mirror may, in an embodiment, be provided in the first objective and/or second objective.

In an embodiment, the ear profiler comprises an actively controlled optical splitter that is configured to selectively optically connect the OCT device to the first objective and the second objective.

This way, an optical path length of a measurement arm may be equal for the first objective and the second objective, and an optical path length of the reference arm may remain constant when the connected objective has been switched. This configuration may advantageously provide a high signal-to-noise ratio as optical energy in the measurement beam is not shared between multiple measurement beams. As such, the signal-to-noise ratio may be approximately equal for each of the objectives as the light beam is not divided between the first objective and the second objective.

In an additional or alternative embodiment, the ear profiler comprises a passive optical splitter that is configured to simultaneously optically connect the OCT device to the objectives. By simultaneously connecting the first objective and the second objective, the reflected parts of the first measurement beam and the second measurement beam may be separated in another way, for example by polarisation. .

A passive optical splitter may provide an economic configuration. Further, a passive optical splitter may allow a shorter measurement time, as no time is needed to switch the objective that is optically connected to the OCT device.

In a further embodiment, the first objective and the second objective are each connected at a different optical path length to the OCT device. For example, an optical path length of the measurement arm with the first objective may be different from the optical path length of the measurement arm with the second objective. This way, different portions of the outer ear may be measured simultaneously, wherein the different portions may be represented in the measurement signal simultaneously at different depths corresponding to differences in the respective optical path lengths. As such, the first measurement signal and the second measurement signal may be measured simultaneously.

In an embodiment, the processing unit is configured to determine a common reference point for the first model and the second model on the basis of an overlap in the first model and the second model, representative for a partially overlapping surface in the first portion and the second portion of the outer ear; and/or a position tracking system for tracking a position of the ear profiler with respect to the outer ear; and/or a predetermined positional relation of the first measurement position and the second measurement position have with respect to each other, and wherein the processing unit is configured to combine the first model and the second model in the common reference point.

In an embodiment, the ear profiler further comprises a third objective, optically connectable to the OCT device to guide the measurement beam from the OCT device towards a surface of the middle or inner ear to measure a third measurement signal representative for a position of a surface of the middle or inner ear.

In a further embodiment, the processing unit is configured to process the third measurement signal to create a model of positions the middle or inner ear.

The third objective may be positioned in a measurement position to emit the measurement beam as a third measurement beam in a third measurement direction towards the middle and/or inner ear. Brief description of the drawings

Further characteristics and advantages of the invention will now be elucidated by a description of embodiments of the invention, with reference to the accompanying drawings, in which:

Figure 1 A schematically depicts an ear of a patient to be measured;

Figure 1 B schematically depicts an embodiment of an ear profiler for measuring an outer surface of the ear of figure 1a, depicted as a cross section along axis A-A of figure 1A, while measuring a first measurement signal with a first objective;

Figure 1C schematically depicts the ear profiler of figure 1 B, provided with a second objective, while measuring a second measurement signal in a second measurement direction;

Figure 1 D schematically depicts the ear profiler of figure 1 C, while measuring a second measurement signal in an additional measurement direction;

Figure 2A schematically depicts a first and/or a second non-telecentric objective according to an embodiment of the invention, for measuring the concha;

Figure 2B schematically depicts a first and/or a second telecentric objective according to an embodiment of the invention, for measuring the outer ear;

Figure 2C schematically depicts a first and/or a second objective according to an embodiment of the invention, for measuring the ear canal;

Figure 2D schematically depicts a first and/or a second objective according to an embodiment of the invention, for measuring the middle or inner ear;

Figure 3 schematically depicts an ear profiler according to an embodiment of the invention, wherein two objectives are attached simultaneously;

Figure 4 schematically depicts an ear profiler according to an embodiment of the invention, configured to measure multiple measurement signals simultaneously;

Figure 5A schematically depicts an embodiment of an ear profiler according to the present invention, wherein the first objective is arranged in first measurement position, and wherein the second objective is arranged in a second measurement position;

Figure 5B schematically depicts a measurement signal according to the embodiment of figure 5A;

Figure 6A schematically depicts another embodiment of the ear profiler according to the present invention, configured to measure multiple measurement signals simultaneously;

Figure 6B schematically depicts measurement signals according to the ear profiler of figure 6A;

Figure 7 A schematically depicts another embodiment of the ear profiler according to the present invention, comprising multiple OCT detectors; Figure 7B schematically depicts measurement signals according to the ear profiler of figure 7A;

Figure 8 schematically depicts an embodiment of an ear profiler according to the present invention, wherein the first objective and the second objective are arranged on a single probe.

Throughout the figures, the same reference numerals are used to refer to corresponding components or to components that have a corresponding function.

Detailed description of embodiments

Figure 1A schematically depicts an ear of a patient. The outer ear 90 comprises the auricle and the ear canal 97, and is separated from the middle and inner ear by the eardrum 95. In the outer ear, a structure or profile of the surfaces of the ear canal 97 and the concha 96 may be of interest in practice. In addition or alternatively, other parts of the ear may be profiled. According to the invention, a first portion 91 and a second portion 92 are measured. In an embodiment, the middle or inner ear 93 may also be measured.

In Figures 1A-1D, an ear profiler 1 is depicted, configured to provide a measurement signal 80 representative for the profile of the outer surface of the outer ear 90. The ear profiler 1 comprises an OCT device 2, configured to emit a measurement beam M1 and to receive a reflected part (not shown) of the measurement beam M1 to measure a measurement signal.

In use, the measurement beam is at least partially reflected by the outer surface of the outer ear 90. The OCT device 2 is configured to provide an measurement signal 21 on the basis of interference between the reflected part of the measurement beam M1 and an internal reference beam.

The ear profiler 1 further comprises a processing unit 70, a first objectives and a second objective 4. The ear profiler 1 comprises a mount 10 for releasable attachment of the first objective 3 or the second objectives 4. The objectives 3,4 are optically connected to the OCT device 2 when releasably attached to the mount 10. The objectives 3,4 are configured to be positioned in a measurement position P1, P2 outside the ear to measure a first measurement signal 21 representative for a profile of the outer surface of a first portion 91 of the outer ear 90 from a first measurement position P1 with the first objective 3 and a second measurement signal 22 representative for a profile of the outer surface of a second portion 92 of the outer ear from a second measurement position P2 with the second objective 4.

In an embodiment of the method, the measurement positions P1, P2 are arranged opposite to the respective first portion 91 and second portion 92, such that they may be measured without obstructions, for example from ear parts as the tragus. Alternatively, the first and second measurement position may be the same position. The first objective 3 and the second objective 4 are detachable and optically connectable to the OCT device 2 via the mount 10, for example by having a mounting mechanism, such as a click, snap or bayonet mechanism. In Fig. 1A and 1B, the first objective 3 is optically connected to the OCT device 2 and is configured to, in the first measurement position P1, guide the measurement beam M1 to emit the measurement beam M1 in a first measurement direction D1, from the OCT device 2 towards the first portion 91 of the outer surface of the outer ear. The first objective 3 may guide the measurement beam M1 in multiple additional measurement directions DT D1” from the first measurement position P1. In the figure, the two outermost additional measurement directions DT D1” of the measurement beam M1 are depicted, which depend, amongst others, on the optical characteristics of the first objective 3,. The optical characteristics of the first objective 3 may define four outermost directions to span a 2D measurement area. The area between the outermost directions DT D1” defines a measurement area. Thus, the first objective may be configured to measure a measurement area adapted to the first portion 91 of the outer ear. The measurement beam M1 may be guided towards multiple measurement points located in between the outermost directions DT D1” on the outer surface in the respective first portion 91 of the outer ear.

The first objective 3 has a relatively large focal distance and a relatively narrow field of view. As such, the first objective 3 is configured to measure the first portion 91 of the outer ear, which comprises a portion of the ear canal 97.

The second objective 4 is also optically connectable to the OCT device 2 via the mount 10, as depicted in Fig. 1C and 1D. The second objective 4 may be connected upon removal of the first objective 3 from the mount 10. In alternative embodiments, the first objective 3 and the second objective 4 may be connected simultaneously. The second objective 4 is configured to be positioned in the second measurement position P2 to guide light beams from and to the second portion 92 of the outer surface to measure a second measurement signal.

In this embodiment, the second objective 4 is configured to, in the second measurement position P2, guide the measurement beam from the OCT device 2 to emit it as a second measurement beam M2 in a second measurement direction D2 towards the second portion 92 of the outer ear. The second measurement direction D2 is not coaxially aligned with and non-parallel to, in particular transverse to the first measurement direction DT

The second objective 4 may guide the measurement beam M2 in multiple additional measurement directions D2’ D2” from the second measurement position. In the figure, the two outermost additional directions D2’ D2” of the measurement beam M2 are depicted, which depend, amongst others, on the optical characteristics of the second objective 4. The optical characteristics of the objective may define four outermost directions to span a 2D measurement area. The measurement beam M2 may be guided towards multiple measurement points in between the outermost directions D2’ D2”. Therewith, the second objective 4 is configured to measure a measurement area adapted to the second portion 92 of the outer ear.

The second objective 4 has optical characteristics that are different from optical characteristics of the first objective 3, such as a smaller focal distance and a relatively wide field of view. As such, optical parameters as numerical aperture, scan area and measurement direction of the second objective 4 are different from the optical parameters of the first objective 3, and, the second objective 4 is configured to measure the second portion 92 of the outer ear that comprises a portion of the concha 96. In use, the first measurement signal 21 comprises an measurement signal from the OCT device 2. The second measurement signal 22 comprises a second measurement signal. In this embodiment, the second measurement signal 22 may be provided upon positioning the OCT device 2 in the second measurement position. In other embodiments, the first and second measurement signals 21, 22 may be provided simultaneously.

The processing unit 70 is configured to process the first measurement signal 21 and the second measurement signal 22 to create a first model of the first portion 91 and a second model of the second portion 91 , and to combine the first model and the second model to create a 3-dimensional model 80 of the outer surfaces of the outer ear. The processing unit 70 here comprises a computer having a display to display the model 80, but may also comprise a computational unit, on a remote location or be integrated in the OCT device 2.

Figures 2A-2D schematically depict objectives 3’, 3”, 4, 5 according to embodiments of the invention. The objectives are configured to be positioned in a measurement position to guide light beams for measuring a measurement signal. The objectives 3’, 3”, 4, 5 may guide a light beam M, for example coming from an OCT device 2 towards an outer surface of the outer ear 90, or vice versa. The objectives 3’, 3”, 4, 5 are detachable and optically connectable to the OCT device 2 by having a mounting mechanism 35, such as a click, snap or bayonet mechanism for releasable attachment to a mount 10. Alternatively, the objectives 3’ 3” 45 may comprise a latch, and the mount 10 may comprise the mounting mechanism 35 In alternative embodiments, the objectives 3’, 3”, 4, 5 may be connectable to other parts of the ear profiler 1 and/or be rigidly attached thereto. The objectives 3’, 3”, 4, 5 may be provided with physical support points 34 for supporting the objective against an outer surface of the outer ear 90, for easy arrangement in a measurement position.

The objectives 3’, 3”, 4, 5 are arranged to guide light beams at least in a measurement direction D defined by a main optical axis 36 thereof. Further, objectives 3’, 3”, 4, 5, by movement of a movable element, such as movable mirror 23, may guide light beams in additional measurement directions D’ D” from a single measurement position, as depicted for measurement beams M M’.

In use, a light beam may be incident at a first lens 31 arranged at a distance d to the galvo scanner 23 of the ear profiler 1 , which may be optically connected to a detector of the ear profiler 1 such as a detector of the OCT device 2 or a ccd chip of a camera. In case of an emitted light beam M, such as a measurement beam, the light beam may be moved by the galvo scanner 23. In an alternative embodiment, the galvo scanner 23 may be arranged within the objective 3’.

In Figure 2A, a non-telecentric objective 3’ is depicted, wherein the distance d is smaller than a focal distance of the first lens 31. The objective 3’ further comprises a high- power lens system. The high-power lens system may comprise multiple lenses 32, a single lens, or other optical elements. The high-power lens system may have an optical power of more than 50 dpt, for example more than 100 dpt. The high-power lens system provides an optical fish-eye effect, such that the objective 3 is configured to guide light beam M along a relatively large field of view, which allows for profiling a relatively large section of the outer ear 90. Therefore, this objective 3’ may be particularly advantageous for profiling the concha 92.

Figure 2B depicts a telecentric objective 3”, wherein a focal distance of the first lens is equal to distance d to a galvo scanner or movable mirror 23. As such, the light beam M leaves the first lens 31 in a direction parallel to an optical axis of the first lens 31, irrespective of an incident angle on the first lens 31. This way, the objective may be guide light beam in a direction transverse, for example perpendicular, to an outer surface of the outer ear 90, This allows for profiling of a relatively large section of the outer ear 90, for example the concha 92. An advantage of a telecentric objective is that the imaged surface 92 may be flat, thus not be curved or distorted in the measurement signal.

In Figure 2c, another objective 4 is depicted. In addition to the telecentric objective 3” of figure 2b, the objective 4 comprises multiple lenses 32 and a reflecting surface 33, such as a mirror or prism. This way, the light beam may be guided sideways with respect to the objective 4, which allows for profiling behind sections of the outer ear 90 that are normally obscured when measuring from outside the ear, such as concha sections that are obscured behind the tragus. In particular, the objective 4 may be advantageous for profiling a first section 91 of the outer ear 90 comprising the ear canal 97.

Figure 2D schematically depicts a third objective 5, connectable to the OCT device 2. The third objective 5 is configured to guide light beams towards the middle and/or inner ear. The third objective 5 has a relatively large profiling distance. The third objective 5 comprises a non-telecentric arrangement, wherein a second lens 32 is arranged at a distance from a first lens 31 , such that an profiling plane 98 at a relatively large distance results. This way, a light beam may be guided past the concha 96 and the ear canal 97 towards a surface in the middle and/or inner ear 93.

The third objective 5 may be particularly advantageous in embodiments wherein the ear profiler 1 is configured to measure a third measurement signal with the third objective 5, representative for a position of a surface the middle or inner ear, and wherein the processing unit is configured to process the third measurement signal to create a model of the middle or inner ear. In a further embodiment, the processing unit may be configured to compare positions of the surface to model vibrations of the surface in the middle and/or inner ear.

Figure 4 schematically depicts an ear profiler according to an embodiment of the invention, wherein two objectives 3,4 are provided simultaneously. In this embodiment, the processing unit 70 is integrated in the OCT device 2. A galvo scanner 23 is in optical communication with a beam splitter 26, such as a semi-transparent mirror, which splits an emitted measurement beam in a first measurement beam M1 and a second measurement beam M2. The first objective 3 guides the first measurement beam M1 in a first measurement direction D1 and the second objective 4 simultaneously guides the second measurement beam M2 in the second measurement direction D2. The first measurement direction D1 is defined by the optical axis of the first objective 3. The second measurement direction D2 is defined by the optical axis of the second objective 4.

By movement of the galvo scanner 23, the direction of the respective measurement beams MT, M2’ is changed, and consequently the respective measurement directions DT, D2’” are changed accordingly. However, the first measurement direction D1, DT remains non-coaxial, in particular non-perpendicular, to the second measurement direction D2, D2”\

In this case, the first measurement direction D1, DT remains transverse, even perpendicular to the second measurement direction D2, D2”\

In an alternative embodiment, as depicted in Figure 3, OCT device 2 may selectively be in optical connection with at least one of the two objectives via a galvo scanner 23, by guiding a measurement beam M1, M2 in another direction. This way, a beam splitter, such as a semi-transparent mirror, may be omitted.

The OCT device 2 may be provided with two objective mounting positions for the mounting mechanisms 35 for simultaneous mounting of multiple objectives 3,4. In addition or alternative to the objectives shown, other objectives may be mounted for profiling specific areas of the ear.

The lengths of optical axes 36 of the first measurement beam M1 and the second measurement beam M2 is different. As such, an optical path length of the measurement arm for the first objective 3 is different from an optical path length of the second objective 4. As a result, the first measurement signal 21 and the second measurement signal 22 may be measured simultaneously, as in Figure 6A and 6B.

Figure 5A schematically depicts an embodiment of an ear profiler 1 according to the present invention, wherein the first objective 3 is arranged in first measurement position, and wherein the second objective 4 is arranged in a second measurement position. The first objective 3 is configured to emit a relatively narrow second measurement beam M1 for profiling the ear canal. The second objective 4 is configured to emit a wider measurement beam M2. In use, the second objective 4 is moved along the surface of the concha for profiling the concha.

The ear profiler 1 comprises an actively controlled optical splitter 26’ configured to selectively optically connect the OCT device 2 to one of the respective objectives 3,4. The first objective 3 is connected to an actively controlled optical splitter 26’ via a first optical fibre 24, and the second objective 4 is connected to the actively controlled optical splitter 26’ via a second optical fibre 25.

The actively controlled optical splitter 26’ optically connects a selected one of the objectives 3,4 with the OCT device 2. A length of the first optical fibre 24 and the second optical fibre 25 is equal, such that an optical path length of light beams through the respective fibres is equal for the first measurement signal 21 and a second measurement signal 22. This way, the optical energy in the measurement beam is not shared between measurement beam M1 and M2 with is beneficial for a signal-to-noise ratio. .

In use, the actively controlled optical splitter 26’ may be configured to switch the selected connected one of the fibres 24, 25 to connect the other one to the OCT device 2.

The actively controlled optical splitter 26’ may be configured to switch upon each measurement, upon a fixed time interval, or switch upon other control methods. A momentary first measurement signal 21 according to this embodiment is depicted in figure 5b.

Figure 6A depicts an embodiment of the ear profiler 1, further comprising a passive optical splitter 26” that is configured to simultaneously optically connect the OCT device 2 to the two objectives 3, 4, comprising a first objective 3 and a second objective 4. The lengths of the optical fibres 24, 25 are different, such that optical path lengths between the first objective 3 and the OCT device 2 and the second objective 4 and the OCT device 2 are different from each other.

This way, the first measurement signal 21 and the second measurement signal 22 may be provided simultaneously. In other embodiments, the lengths of the optical fibres 2425 may be similar, wherein the reflected parts of the first measurement beam and the second measurement beam are separated in another way, for example by having a different polarisation. In the Figure, the signals are shown separately. However, in practice, multiple signals may be provided via a single physical connection. Due to the different optical path lengths of the optical fibres 24, 25, an A-scan depth of the first measurement signal 21 and second measurement signal 22 may be different, such that they do not interfere with each other. As such, the first and second measurement signals may be provided simultaneously using a single detector of a single OCT device 2, as depicted in figure 6b. Additionally or alternatively, the optical lengths of the respective objectives 3, 4 may be different to achieve the same effect without having optical fibres 24, 25 with different optical path lengths.

In this embodiment, the processing unit may be configured to subtract the optical path length difference pi between the second measurement signal 22 and the first measurement signal 21 from the second measurement signal 22 while processing the first measurement signal 21 and the second measurement signal 22 to create a 3-dimensional model of the outer surfaces of the outer ear.

The second objective 4 is configured to emit a relatively wide measurement beam M2. This way, the second objective 4 may be used for profiling the second section 92 of the outer ear comprising a part of the concha in a single measurement.

Figure 7 A discloses an alternative embodiment, wherein the ear profiler 1 comprises multiple OCT devices 2, separately connected to the respective objectives 3, 4, 5 and/or an OCT device having multiple detectors. This way, the multiple OCT devices 2 and/or multiple detectors may each simultaneously measure a measurement signal 21, 22, 23 representative for a profile of an outer surface of the outer ear.

Figure 8 schematically depicts an embodiment of an ear profiler according to the present invention, wherein the first objective and the second objective are arranged on a single probe 71.. wherein the first objective 3 and the second objective 4 are arranged at different locations within the probe 71 of the ear profiler 1 , such that the first measurement position P1 and the second measurement position P2 have a predetermined positional relation with respect to each other.

In other embodiments, the ear profiler may comprise a camera, for example a stereo camera, optically connectable the second objective 4 and configured to provide a camera signal on the basis of light reflected by the outer ear 90, wherein the second objective 4 is optically connectable to the camera, and wherein the second measurement signal comprises the camera signal.

An embodiment described herein may be used as follows: the first objective 3 is positioned in the first measurement position P1 outside the ear and optically connected to the OCT device 2. For measuring the first measurement signal, the OCT device 2 is activated to emit a measurement beam, which is guided by the first objective 3 to be emitted as a first measurement beam M1 towards a first portion 91 of the outer surface of the outer ear, in a first measurement direction D1 parallel to the ear canal. Tissue in the ear canal, for example the outer surface, reflects the first measurement beam M1 at least partially. The reflected part of the first measurement beam M1 may be guided back to the OCT device 2 via the first objective 3, whereby it may be detected by a detector of the OCT device 2 for providing the measurement signal on the basis of interference between the reflected part of the first measurement beam M1 and a reference beam. As such, the first measurement signal 21 is representative for a profile of the outer surface of a first portion 91 of the outer ear 90, comprising a portion of the ear canal.

Then, a second objective 4 is optically connected to the OCT device 2 and positioned in a second measurement position P2 outside the ear, whereby the OCT device 2 is activated to emit a measurement beam, which is guided by the second objective 4 to be emitted as a second measurement beam M2 towards a second portion 92 of the outer surface of the outer ear, in a second measurement direction D2 transverse to the first measurement direction D1. The second measurement beam M2 is at least partially reflected on the outer surface and, via the second objective 4, guided back to the OCT device 2 via the second objective 4 to measure, on the basis of interference between the reflected part of the second measurement beam M2 and a reference beam, measure a second measurement signal 22 that is representative for a profile of the second portion 92 of the outer of the outer ear that comprises a portion of the concha.

Alternatively, the second objective 4 may be connected to another part of the ear profiler 1, such as a camera, and the second measurement signal 22 may comprise another signal, such as a camera signal.

The respective measurement positions P1, P2 and measurement directions D1, D2, are determined such that, when using the first objective 3 and the second objective 4, the first portion of the outer ear and the second portion of the outer ear form a partially overlapping surface.

The processing unit 70 then processes the first measurement signal and the second measurement signal to create a first model of the first portion and a second model of the second portion. The processing unit 70 combines the first model and the second model to create 3-dimensional model of the outer surfaces of the outer ear. For example, the processing unit 70 determines a common reference point 94 on the overlapping surface for the first measurement signal 21 and the second measurement signal 22. Alternatively a common reference point 94 may be determined on the basis of a position tracking system or a predetermined positional relation between the first objective and the second objective. The processing unit 7- then combines the first model and the second model in the common reference point.

The processing unit determines a rotational difference between the first measurement direction D1 and the second measurement direction D2 on the basis of the common reference point, such that the first measurement signal and/or the second measurement signal can be adjusted for the rotational difference. Further, the position of the first measurement position P1 with respect to the second measurement position P2 may now be determined using the common reference point 94, such that a positional difference between the first measurement position P1 and the second measurement position P2 can be determined, and the first measurement signal 21 and/or the second measurement signal 22 may be adjusted on the basis of the positional difference. The first model and the second model may first be rotated and rescaled and then combined to create a 3-dimensional model of the outer surfaces of the outer ear.

On the basis of the 3d-model, the ear may be examined and, for example, a hearing aid can be manufactured precisely. Further, if additional examination of the middle or inner ear is necessary, the ear profiler may be provided with a third objective, which may be used similar to the first and/or second objective to measure a third measurement signal representative for a surface in the middle or inner ear.