THEREWITH

TECHNICAL FIELD

The present invention relates to a spectrometer and a detector arrangement for use therewith, for being used in sorting objects, and more specifically for sorting objects in bulk.

BACKGROUND

There are a lot of different spectrometers on the market today configured for a lot of different applications. One such application is the sorting bulk of objects, where the quality of the objects differs. Example of such objects may be different types of granules, such as grains. Such objects may be illuminated and the light reflected from or passing trough the object may be collected by a detector. The detector preferably generates a plurality of measurement variables, such that multivariate analysis may be performed in order to determine the quality of the object. A standard spectrometer usually comprises a gate or port for incoming light. At the port there may be a grating or prism for diffracting the received light into different wavelength ranges. The

spectrometer may also comprise a number of mirrors for projecting the diffracted light onto the detector.

The most common detectors are made up by diode arrays, i.e. there are a lot of small detectors or sensors arranged closely together. Such a detector is a Charge- Coupled Device, CCD, such as linear CCDs. The small sensors are called pixels and there are usually 8 to 4096, such as 8 to 1024, such as 128 to 512 pixels. The pixels may have a height of about 500 μιη and a width of 25 μιη. It is also possible to use detectors in form of diode arrays, without capacitors, provided with other amplification options. The spectrometer may be configured for different wavelength ranges. If an Indium Gallium Arsenic, InGaAs, diode array is used as detector; the normal range may be 900-1700 nm. If for example one diode array having 256 photodiodes is used, each photodiode will cover a wavelength range of 3,125 nm. Such a detector will have a resolution of 256 different wavelength ranges, ranging from 900 nm to 1700 nm and each being 3,125 nm wide. In use the amount of light that is collected by each pixel or photodiode will be monitored and a diagram showing the registered amount of light for each pixel or photodiode is called a spectrum. As for a camera it is possible to select a time of exposure which is adapted to luminance of the object and the sensitivity of the pixels or photodiodes, i.e. how much light each pixel needs in order to get a good reading. There are also diode arrays, such as for example diode arrays based on Silicon, Si, which work in the wavelength range of 400-1050 nm. Such a Si diode array is much cheaper, but has the disadvantage that it needs more light in order to give qualitative readings, which indicates that the time of exposure needs to be longer then for the InGaAs diode array.

If a spectrometer is used with for example a device for sorting objects as described in the international patent application no. WO2004/060585, there will be high demands on the time for each exposure. Such a device is capable of sorting up to 250 granules per channel and second or 1 granule per each 4 ms. If there was a way to speed up the reading time in and data transfer from the spectrometer, i.e. the time it takes for sufficient amount of light (number of photons) to be received by a pixel or photodiode, the throughput of such a sorting device could be realized.

Thus, there is a need for a spectrometer that gives faster readings, but still is capable to determine the quality of an object with high predictability.

SUMMARY

An object with embodiments of the present invention is to provide a spectrometer having a configuration that allows faster readings. The object may be achieved by a spectrometer comprising illuminating means for providing incoming light, diffracting means for diffracting the incoming light in different wavelength ranges, and a detector having a detector area for receiving the diffracted light, wherein the incoming light enters into a plurality of light channels, each light channel having an associated port and diffracting means, resulting in a plurality of associated ports and diffracting means, and in that said detector area is divided into a plurality of detector subarrays, each detector subarray corresponding to one of the plurality of light channels, wherein each subarray is arranged to receive diffracted light mainly from its corresponding light channel via the diffraction means associated to said corresponding light channel.

In preferred embodiments the illumination means may be optical fibres connected to each port, which optical fibres also may be furcated such that each optical fibre is arranged to provide light to multiple light channels through a single port, the number of multiple light channels served by the single port corresponding to the furcations of the optical fibre.

In other embodiments the diffracting means may be a grating or a prism or may be constituted by filters, each filter corresponding to a variable suitable for multivariate analysis. The arrangement of reflectors and/or lenses may then be adapted accordingly. Furthermore, the detector may preferably be a charge-coupled device, CCD, comprising a diode array of Indium Gallium Arsenic, InGaAs, Silicon, Si, PbSe, or PbS.

A further object of embodiments herein is to provide a detector arrangement, which is suitable to use in a spectrometer for increasing the speed of readings and obtaining high sensitivity in said spectrometer.

The object may be achieved by a detector arrangement configured for use with a multi channel spectrometer, comprising a detector arranged for receiving light from illuminating means, which light has been diffracted by means of diffracting means, said detector having a detector area. The incoming light provided by the illumination means is divided into a plurality of light channels, such as one illumination means per light channel, and the detector area is divided into a plurality of detector areas corresponding to said plurality of light channels. By using the above described detector arrangement in a spectrometer it is possible to substantially increase the sensitivity, which in turn increase the speed with which the spectrometer may make readings.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of embodiments of the present disclosure will be apparent and elucidated from the following description of various embodiments, reference being made to the accompanying drawings, in which:

Fig. l is a schematic view of a spectrometer, an object, and a light source, according to one embodiment of the present invention;

Fig. 2 is a schematic view of a detector, according to one embodiment of the present invention;

Fig. 3 is a schematic view of some elements in a multi channel spectrometer, according to one embodiment of the present invention;

Fig. 4 is a schematic illustration of a spectrometer according to an

embodiment; and

Fig. 5 is a schematic illustration of a spectrometer according to an embodiment.

DETAILED DESCRIPTION

In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular components, elements, techniques, etc. in order to provide a thorough understanding of the exemplifying embodiments. However, it will be apparent to one skilled in the art that the exemplifying embodiments may be practiced in other manners that depart from these specific details. In other instances, detailed descriptions of well-known methods and elements are omitted so as not to obscure the description of the example embodiments. The terminology used herein is for the purpose of describing the example embodiments and is not intended to limit the embodiments presented herein.

Turning now to Figure 1 a schematic view of a spectrometer 20 is shown. A light source 2, such as a lamp, illuminates an object 3, from which object light is fed into the spectrometer 20. The spectrometer 20 comprises different reflectors 4, such as mirrors, grits, or combinations of these, possibly lenses (not shown), diffracting means 6, a detector 8, integral or connected illumination means 10, and an incoming port 12. The light from the object 3 is transported by the illuminating means 10 and sometimes reflectors 4 to the diffracting means 6. The illuminating means 10 provide incoming light to the spectrometer 20. As will be further explained in conjunction with figure 3, the incoming light may be divided into different light channels. The diffracting means 6 diffract the incoming light in different wavelength ranges such that each wavelength range will reach its corresponding pixel(s) or photodiode(s) on a detector area of the detector 8. Mirrors 4 may be used both for reflecting light from the object 3 onto the diffracting means and for projecting the diffracted incoming light onto the detector 8.

As explained above in the background a typical spectrometer may have a resolution of 256 wavelength bands for a diode array detector, such as a photodiode detector, said photodiode detector having 256 photodiodes. Such a photodiode detector measures the amount of light striking the photodiode array to determine the absorbance of the sample, such as grain. Each photodiode is comprised in a pixel in turn also comprising a capacitor initially holding a fixed amount of charge. Light striking the photodiode discharges the capacitor. The magnitude of the discharge depends on the amount of light striking the photodiode. Today there is often a strive for improving the resolution in a spectrometer, such that one is able to detect objects and substances more and more accurate. However, by realizing that this strive for improved resolution is not always true for measurement of quality in all type of objects, the inventors decided to deteriorate the resolution in order to create a detector that has a higher light sensitivity then is the case today. Basically the same type of detector 8 as conventionally is used. However, as will now be explained in conjunction with Figure 2 the detector 8 has been dived into 8 subarrays 8a-8h. Each subarray (sub detector) 8a-8h now comprises 32 photodiodes as compared to 256 photodiodes for the original detector 8. By doing this it is possible to create a multichannel spectrometer, wherein each subarray 8a-8h will represent one of the channels. In this case the detector 8 has been divided into eight subarrays 8a-8h. However it should be understood that the detector 8 may divided into four, eight, sixteen or any other number of subarrays depending on which type of application the spectrometer 20 is aimed for.

Although the reflector 4 in Figure 1 is shown as a mirror it should be appreciated that a mirror is required for the spectormeter according to some

embodiments. By incorporating one or several mirrors in the light path between the ports and detector the external dimensions relating to the compactness of the spectrometer could be decreased. For example, a spectrometer without any mirrors will likely have a length being greater than that of a spectrometer provided with a number of mirrors.

In this exemplary case with eight subarrays 8a-8h the resolution of the spectrometer 20 will deteriorate with a factor eight. It is by realizing the fact, as mentioned above, that even if the resolution has deteriorated with a factor eight, the spectrometer 20 may still be very useful for many applications. In this case each photodiode will receive light from a wavelength band of 3,125 x 8 nm = 25 nm instead of as in the conventional spectrometer where the wavelength band is 3,125 nm. The spectrometer may be adapted in relation to the wavelength interval of the light source, such that the spectrometer will collect the wavelength interval of interest for the specific application. If for example the light source emits light in the wavelength interval of 400 to 1700 nm, the spectrometer is adapted accordingly, and also in accordance with the light expected to be emitted from the object, to collect the wavelength interval of interest for the specific application. However, the light source could just as well for example emit light in wavelengths above and below 1700 nm and 400 nm, respectively, whereby the spectrometer is adapted after that, in accordance with above. No restrictions in this regard are thus envisioned, but in the field of multivariate analysis of grain, the wavelength interval of 400 to 1700 is specifically preferred. Another benefit with having a deteriorated resolution is that the requirements of the incoming light as a thin light beam with high intensity are much more relaxed. Normally the port/ports 12, in figures 1 and 3, respectively, for incoming light needs to have a slit that is between 25 to 50 μηι for accomplishing a fair (standardized) resolution. Since, the wavelength band for each photodiode now has increased to 25 nm according to the above described embodiment it is also possible to increase such a slit with a factor 8 to 100 to 200 um. Resolution increases when the slit is narrowed. If an optical fibre is used as illuminating means 10 for providing the incoming light, it may typically have a diameter of about 500 μιη. It would be possible to use such an optical fibre directly without any slit and thus accomplish a simpler spectrometer having less parts. As mentioned above, this solution gives a much worse resolution then in prior art spectrometers, but is still sufficient for example for predicting specific qualities in grain together with the increase in sensitivity.

Another benefit with the much increased light sensitivity of the detector 8 is that instead of using a detector array of InGaAs it is possible to use detector array of Si. The obvious advantage with the Si detector array is that it is much cheaper, and thereby it is also possible to use much larger detectors.

Turning now to Figure 3 a schematic view of some elements in a multi channel spectrometer are shown. In figure 3 eight different light channels are shown. However, as mentioned above the detector 8 may be configured with more or less subareas, such as subarrays, than eight and therefore it should be understood that also the number of light channels may vary in correspondence with the number of detector subareas, such as subarrays. The figure shows eight diffracting means 6a-6h, such as gratings or prisms. The first, second, third, sixth, seventh, and eighth diffracting means from above in figure 3, i.e. diffracting means 6a, 6b, 6c, 6f, 6g, and 6h, each have a fiber optical cable 10 as illuminating means and are connected to an incoming port 12 of the diffracting means 6 and each constitute a light channel. Upstream the fiber optical cables 10, objects 3a to 3h are arranged, such that light emitted onto the objects 3a to 3h then is emitted from the objects 3a to 3h to enter the respective fiber optical cables and ports 12. The fourth and fifth diffracting means from above in figure 3, i.e. diffracting means 6d and 6e, each have a fiber optical cable 10 as illuminating means and are connected to an incoming port 12 of the diffracting means 6. In this case the optical fiber cable 10 is bifurcated and has incoming light from two sources - light source 21 and light source 22 for the fourth diffracting means and light source 23 and light source 24 for the fifth diffracting means, wherein said light sources 21 to 24 may be light from objects 3di, 3d ₂ , 3ei, and 3e ₂ , respectively, which in turn have been illuminated by a light source, such as a lamp 2. It is also possible that the cable 10 can be more than bifurcated, such as tri-, terra-, penta-, hexa-, hepta-, octafurcated, and then having each furcation arranged to collect light from an object from one light source each per furcation. The optical fiber cable may be furcated with more then two branches depending on the available light sources. Sequential exposure times for the multiple, such as two or more, light sources, are also envisioned. Hence, for the fourth diffracting means 6d, this diffracting means 6d is first exposed to light from light source 21, which in turn is spread onto the object 3di (arranged in line with corresponding parts in Fig. 1), where after light from said object 3di then is spread on the corresponding detector subarea, such as for example subarray 8d. A signal is then collected from the subarray 8d. After being exposed to light from light source 21 the diffracting means 6d is exposed to light from an object 3d ₂ (normally another object than the object emitted by light source 21) emitted by light from light source 22, which in turn is spread onto the same detector subarea, such as for example subarray 8d. In this way spectra from two objects, such as two objects being exposed to light at different points in time due to different positions in a bulk of objects, such as different positions in a drum for sorting objects in a bulk of such objects, as disclosed in WO2004/060585 may be received by the corresponding subarray 8d. Correspondingly, the fifth diffracting means 6e, may be sequentially exposed to light from light sources 23 and 24.

When using a spectrometer according to figures 1 to 3, the

illumination/exposure scheme for the different channels may be regulated such that if for example a subarray 8b is exposed at a first point of time, then subarrays 8a and 8c are not exposed simultaneously, i.e. at said first point in time. In this way, diffractions intended for neighboring subarrays will not interfere with each other.

It is also possible to use the neighboring subarray or subarrays, such as one or both of subarrays 8a and 8c when mainly illuminating/exposing subarray 8b, to extend the available area for readings under subarray 8b into subarrays 8a and/or 8c. In this way, if needed, the available area or number of pixels may be increased from for example 32 to 64, wherein up to half of the pixels of subarrays 8a and/or 8c are used in addition to subarray 8b. Then the other half being furthest from the subarray 8b may be used in the same way to increase available area for readings under subarray 8d, and so on.

Thereafter, in direct sequential order or at a later sequential stage, subarray 8a and/or 8c are exposed, and signals collected therefrom, while then no exposure is performed on subarray 8b at that later point in time and hence no signal is collected from subarray 8b at this later point in time. In one illumination/exposure scheme subarrays 8a, 8c, 8e, and 8g are exposed at a first period of time, where after subarrays 8b, 8d, 8f, and 8h are exposed at a later point in time, and this procedure is then repeated.

Figure 4 shows an exemplary embodiment comprising three different light channels 10, each arranged to guide light onto a respective port 12. Each port is operatively connected a diffracting means 6a-6c, The diffracted light from each diffracting means 6a-6c is further projected onto each subarray 8a-8c, respectively. As mentioned before majority or all of the light originating from each diffracting means 6a- 6c is projected onto the corresponding subarray 8a-8c of the detector 8. Hence, at least a major part of the diffracted light from diffracting means 6b will thus be projected onto its corresponding subarray 8b. Depending on the application, actual component configuration setup, and specifications of each component in the spectrometer, in some situations neighbouring subarrays, e.g. 8a and/or 8c when looking at the diffracting means 6b/subarray 8b, may be able to receive a minor portion of the light originating from diffracting means 6b, and therefore the diffracted light detected at these neighbouring subarrays 8a, 8c could also be used for the subsequent analysis, e.g.

multivariate analyis.

Figure 5 shows another example configuration of the spectrometer in which convex lenses 51a-51c are arranged between each diffracting means 6a-6c and the detector 8 containing the subarrays 8a-8c. In some embodiment these convex lenses 51a-51c could be replaced by a single convex lens (not shown).

It should be appreciated that the although only three light channels with corresponding ports, diffracting means, and subarrays of the detectors are shown in Figures 4 and 5 the present invention is not limited to this specific three light channel configuration. Hence, any number of light channel with corresponding ports, diffracting means, and detector subarrays is equally possible within the scope of the present invention. For example, a similar configuration of Figs 4 or 5 provided with four or more light channels could also be used, simply by adding one or more light channels with corresponding ports, diffracting means, and defining one or more further corresponding detector subarrays (having smaller extensions) within the detecting area of the detector. Hence, the physical detector area would in such way be divided up into four or more subarrays instead of three subarrays as shown in Figures 4 and 5.

Thus, it is believed that different embodiments have been described thoroughly for purpose of illustration and description. However, the foregoing description is not intended to be exhaustive or to limit example embodiments to the precise form disclosed. Thus, modifications and variations are possible in light of the above teachings or may be acquired from practice of various alternatives to the provided embodiments. The examples discussed herein were chosen and described in order to explain the principles and the nature of various example embodiments and its practical application to enable one skilled in the art to utilize the example embodiments in various manners and with various modifications as are suited to the particular use contemplated. The features of the embodiments described herein may be combined in all possible combinations of methods, apparatus, modules, systems, and computer program products. It should be appreciated that any of the example embodiments presented herein may be used in conjunction, or in any combination, with one another.

It should be noted that the word "comprising" does not necessarily exclude the presence of other elements or steps than those listed and the words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements. It should further be noted that any reference signs do not limit the scope of the example embodiments, that the example embodiments may be implemented at least in part by means of both hardware and software, and that several "means", "units" or "devices" may be represented by the same item of hardware.