Technical Field

The present invention relates to an apparatus and method for detecting movement of a controller along an axis and in particular, though not necessarily, to such a method and apparatus for use with rotary encoders.

Background

In the field of conventional mechanical watches, the “crown” of the watch is the button or knob that projects from an edge of the watch to allow the user to set the time and date and to control other functions. The crown is fixed to a “stem” or shaft which is the elongate tube that connects the crown to the internal mechanism. For the sake of brevity, the term “crown” as used hereinafter refers to the combination of the conventional crown and stem, unless stated otherwise.

Smartwatches are advanced iterations of the conventional watch and of course include many more features, typically implementing many of the functions of smartphones. However, common to many such smartwatches is the use of a crown-type knob to allow users to access and control functions. The advantage of the crown is that it allows not only control of certain “binary” type operations, e.g. on/off, with a simple button press, it can additionally be used to scroll through many function states by way of rotation. Rotation of the crown can therefore be used to set a time by scrolling through a range of numbers, to scroll through menu option, to zoom a camera feature, etc. Figure 1 illustrates schematically the main body of a smartwatch 130 comprising a display 131 and a crown 110. Also illustrated are a series of Graphical User Interface (GUI) screens 132 that can be used to control the smartwatch in conjunction with the crown (and possibly other switches and knobs not shown in the drawing).

In order to perform the operations, the smartwatch may include a means for detecting the angular position of the crown about its axis of rotation as well as the position along the axis. This means may detect the absolute position as well as a speed of rotation. This means is commonly referred to as a “rotary encoder” (sometimes called a “shaft encoder”). The measurements that are obtained by a rotary encoder can be converted into an analogue or digital output for further processing. Rotary encoders can include one or more mechanical, optical, magnetic, and/or capacitive components. For example, a rotary encoder can be implemented as an electro-mechanical device. Of course, two factors critical for rotary encoders in the context of smartwatches are miniaturisation and cost.

Figure 2 illustrates a system for (i) measuring the angular position and/or motion of a rotary shaft 102 coupled to the watch crown 110 via a stem 111 , and (ii) detecting a longitudinal movement of the rotary shaft 102. The system 150 includes an optical rotary encoder system 100, a computer system 154, and a display 131 that is controlled by display control signals 156 provided to it by the computer system 154. The system 150 can be used, for example, to control an electronic device such as a smartwatch.

An end view of the rotary shaft 102 is shown in inset A from which it can be seen that a multiplicity of grooves 104 are formed coaxially along the length of the shaft. The rotary encoder 100 includes a system 101 having at least one light generating element 105 operable to generate light, and a pair of light detecting elements 106a, 106b operable to detect light and convert the detected light into a signal. It will be readily apparent that rotation of the control knob 110 results in a corresponding rotation of the rotary shaft 102 causing a modulation of the light 108a, 108b reflected towards the light detecting elements. Electrical signals 155 generated by the light detecting elements 106a, 106b are provided to the computer system 154, allowing the computer system to demodulate the signals and thereby detect a rotation and position of the rotary shaft 102 about its axis 111a.

The system 150 includes a switching contact mechanism 152 (e.g., a push button mechanism) positioned proximate to the end of rotary shaft 102. Further, the system includes a spring element 151 that biases the rotary shaft 102 away from a switching contract mechanism 152. When a user is not pressing the control knob 110, the rotary shaft 102 is positioned away from the switching contact mechanism 152, and the switching contact mechanism 152 remains electrically open. When the user presses the control knob / crown 110 inward (e.g., in the direction of arrow 158), the rotary shaft 102 presses against the switch contact mechanism 152, and causes the switching contact mechanism 152 to electrically close. The computer system 154 can detect the opening and closing of the switch contact mechanism 152 by monitoring (e.g., via wires or a flexible printed circuit board) control signal 153, and control the operation of the electronic device 130 accordingly. WO2019156629A1 describes an improvement upon the rotary encoder of Figure 1 and which involves replacing the switching contact mechanism 152 by introducing a further marking around the rotary shaft 102 at a given axial position. This lies outside of the illuminated region of the shaft when the control knob 110 is in its resting position. However, when the knob is depressed, the further marking moves into this illuminated region and produces a modulation of the reflected light that is detectable by the light detecting elements 106a, 106b and the coupled computer system 154. The marking may be, for example, a dark band that contrasts with a reflective metallic surface of the rest of the rotary shaft. The rotary encoder of WO2019156629A1 reduces the overall component count and therefore offers the possibility of reduced cost.

US20190317454A1 also describes a rotary encoder suitable for a smart watch. The approach relies upon the coherent mixing of light reflected from the watch’s rotary shaft with the source light to detect rotation of the shaft.

Summary

Aspects of the present invention are set out in the appended claims

Embodiments may allow detection of movement of the controller along the axis regardless or angular orientation of the controller, thereby allowing the apparatus to additionally comprise a rotary encoder.

Brief Description of the Drawings

Figure 1 illustrates schematically a known smartwatch design;

Figure 2 illustrates a known rotary encoder with axial position detection mechanism; Figures 3a-c illustrate a first embodiment for detection an axial position of a controller; Figures 4a-c illustrate a second embodiment for detection an axial position of a controller; Figures 5a-d illustrate a third embodiment for detection an axial position of a controller; Figure 6 illustrates an axial position versus distance profile for the embodiment of Figure 5;

Figures 7a-c illustrate a fourth embodiment for detection an axial position of a controller; Figures 8a-d illustrate various light source and detector arrangements for measuring a distance; and

Figures 9a-b illustrate the incorporation of lenses into a light source and detector arrangement. Detailed Description

As has already been discussed above, it is desirable or even necessary to be able to detect movement of the knob or crown 110 along an axis of rotation 202 as well as potentially around that axis. A conventional electromechanical arrangement was described with reference to Figure 2. It is also known to use visible markings on the rotary shaft 102 that can be detected by optical means to indicate such an axial movement. Such visible markings can be provided around the eccentric components described with respect to Figures 3 to 12 such that they are detected by the light source and detector arrangement 300 upon axial movement of the eccentric components. Figures 13a-c illustrate an alternative arrangement that relies on detecting changes in distance, where Figure 3a illustrates an end-on view of the arrangement, looking into the device (e.g. the smartwatch), whilst Figures 3b and 3c illustrate side views of the arrangement.

In this arrangement, a component 400, which in this example is a circular cylinder, is provided with a step change in its diameter at a given axial position. This gives rise to two distinct sections, 40T and 410’, with the former having a greater diameter than the latter. The larger section 40T lies within the illuminated region of the light source and detector arrangement 300 in the resting axial position of the knob 110, i.e. when the knob is not being pressed. When the knob is pressed in, e.g. against the resistance provided by an internal spring, the smaller section 410’ moves into the illuminated region as illustrated by the change between Figures 13b and 13c. The resulting (step) change in distance between the light source and detector arrangement 300 and the surface of the eccentric component can be detected and taken as indicative of a button press. A press can be detected regardless of the rotational orientation of the component 400. It will be further appreciated that multiple step changes can be provided along the length of the eccentric component to allow different extents of button press to be detected. Such step changes may also be used to detect pulling of the knob into an extended state.

Figures 4a-c illustrate an alternative arrangement in which the diameter varies linearly (at an angle a to the axis of rotation) along the axis of the eccentric component 420. With this arrangement, it is possible not only to determine that a particular axial position has been crossed (indicated by the step), but one can quantitatively determine an axial position. This arrangement potentially provides an additional “degree of freedom” for controlling the device. Figures 5a-d illustrate a yet further alternative arrangement in which the component 430 is provided with a circumferentially extending notch 432 at an intermediate axial location. The notch lies outside of the normal region of illumination, but moves across that region when the knob 110 is pressed. A complete pressing of the knob moves an axial section of the component on the other side of the notch into the illumination region. A button press is therefore detected by observing a short increase in the measured distance. Similarly the release of the knob is detected by a subsequent, temporary change in the distance. Operation of the arrangement is further illustrated by the distance versus axial position profile of Figure 6.

The arrangements described above rely on measuring a distance to a circumferential edge of a component mounted with respect to a rotation axis. Figures 7a-c illustrate an arrangement that employs an alternative approach. In this arrangement the light source and detector arrangement are located at a position that is axially spaced from the (innermost) end of the component 500. The light source and detector arrangement directs a beam of light in a substantially coaxial direction so that it is incident on and is reflected from the end of the component.

Figure 7a illustrates a light source and detector arrangement which uses a single arrangement providing a single distance measurement. Figure 7b illustrates an alternative light source and detector arrangement which utilises a pair of such arrangements providing a pair of distance measurements, with the target region for the light beam indicated by “X”. The use of a pair of light source and detector arrangements provides for redundancy and therefore increased reliability and security.

The mechanisms described above are well suited to use in smartwatches where miniaturisation of the encoders is desired. The measure of distance derived, be that a direct measure or an indirect measure, can be used as or to derive a control signal for the smartwatch. The described mechanisms can find application in other areas of course, including but not limited to conventional electromechanical watches and smartphones.

Considering now light source and detector arrangements suitable for use with the embodiments described above, these may rely on SMI (self-mixing interference). This is a well-known technique in which light is emitted from a resonant light source (having an optical resonator in which the light circulates), e.g., a laser, with reflected (or scattered) light being fed-back into the resonator. The feed-back light interacts with the light in the resonator or, more precisely, it introduces a disturbance in the light source by interference. This effect can be sensed and can be related to the interaction with the object, such as to a distance to the object or a velocity of the object (relative to the light source / resonator exit mirror). By calibration, it is possible to map an output signal of the SMI arrangement to a distance. SMI-based sensors can be made very compact and therefore small, and make possible absolute distance and velocity measurements. VCSELs (vertical-cavity surface emitting lasers) can be used for SMI, which can be made very small and cost-efficient.

Considering this approach in more detail, the intensity of light output by the VCSEL various sinusoidally as the distance between the resonator and the target changes. Consequently, the output of the detector will also vary sinusoidally. A measure of change of distance can be obtained by counting the number of fringes (peaks and troughs) in the output signal.

Various means to determine the distance to the reflecting / scattering surface are illustrated in Figures 8a to 8d:

Figure 8a. Light emitted by the VCSEL, by way of reflection from the target, is detected using a photodiode 604a. The intensity of the emitted light, indicated by the output current of the photodiode, can be correlated with distance.

Figure 8b. A beam splitter 606 can be positioned close to the exit mirror to pass most of the light exiting the exit mirror and reflect a small portion thereof to a photodetector 609. Again, detected light intensity can be correlated with distance.

Figure 8c. A cover glass 611 is located between the light source and the target so that a portion of the emitted light is reflected back from the cover glass to the detector 604c. Figure 8d. A photodetector 604d is located directly beneath the VCSEL to detect light generated within the resonator.

Alternative arrangements for detecting a measure of distance may involve monitoring a drive signal for the light source, e.g.,

1) the light source is driven with constant current, and a change in voltage is determined; or

2) the light source is driven with a constant voltage, and a change in current is determined. The electrical signal may however be noisier than an optically obtained signal (Figures 8a-d).

It will be appreciated by the person of skill in the art that various modifications may be made to the above described embodiments without departing from the scope of the present invention. These may include, by way of example:

Operating the laser at any wavelength from UV to IR;

Using an edge emitter laser EEL, VCSEL, quantum dot laser QDL or quantum cascade laser QCL; In case of a VCSEL, the VCSEL can be front side or back side emitting VCSEL;

In case of VCSEL, a lens 633a can be added in order to focus the beam or collimate the beam on the disc or shaft as illustrated in Figure 9a, or a lens 633b can integrated onto the VCSEL itself using a back side emitting VCSEL, Figure 9b.

It will be further appreciated that the light source (and detector) may be replaced by any other suitable radiation source and detector, for example operating in the visible of non- visible spectra, e.g. infra-red, ultra-violet.

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