A system, method and computer program for measuring a point spread function of an imaging device

Abstract

A system for measuring a point spread function of an imaging device, the system comprising: a light source configured to emit light, a filter configured to filter light emitted by the light source to a predetermined wavelength range, a light guiding fibre configured to guide light emitted by the light source and filtered by the filter along a path defined by the light guiding fibre, wherein light enters the light guide fibre through a first end of the light guide fibre and exits the light guide fibre through a second end of the light guide fibre; an adjustment unit configured to adjust a position of the second end of the light guiding fibre within a field of view of the imaging device; and circuitry, wherein the circuitry is configured to measure the point spread function of the imaging device when light exiting the light guiding fibre is captured by the imaging device.

Description

[0001] A System, Method and Computer Program for Measuring a Point Spread Function of an Imaging Device

[0002] BACKGROUND

[0003] The present disclosure relates to a system, method and computer program for measuring a point spread function of an imaging device.

[0004] Field of the Disclosure

[0005] The "background" description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in the background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.

[0006] An imaging device may be used to capture images (or image data) in a number of different situations or environments. The imaging device can include one or more optical elements (such as lenses) which focus light onto an imaging sensor. The imaging sensor captures the image data, which varies in response to the light falling on the imaging sensor. That is, light falling on the imaging sensor is converted into a signal which forms the image data. An example of an imaging sensor includes a CCD or CMOS imaging sensor.

[0007] A Point Spread Function (PSF) describes the response of a focused optical imaging device to a point source. That is, the PSF describes what a single point in the object looks like in the image. The PSF (related to the degree of spreading (or blurring) in a captured image of a point source) can provide a measure of the quality of imaging system. The PSF of an imaging device typically varies: over the field of view (FoV), in accordance with object distance, in accordance with image focus and / or in accordance with the wavelength of light. As such, an imaging device may have many different PSFs.

[0008] For a simple imaging device (with few optical elements) a theoretical calculation of the PSF of the imaging device can be made. However, as an imaging device becomes more complex, the theoretical calculation of the PSF may not necessarily accurately reflect the actual PSF of the imaging device.

[0009] As such, it is often desired that an empirical measurement of the PSF of an imaging device is made.

[0010] However, it can be difficult to reliably and accurately measure the PSF of an imaging device. For example, it can be difficult to provide enough illumination (with light from a light source) in order to reliably measure the PSF of an imaging device. This problem is exacerbated when there is a desire to measure the PSF of the imaging device for different wavelengths of light.

[0011] It is an aim of the present disclosure to address these issues. SUMMARY:

[0012] A brief summary about the present disclosure is provided hereinafter to provide basic understanding related to certain aspects of the present disclosure.

[0013] A system for measuring a point spread function of an imaging device is provided in accordance with claim 1 of the appended claims.

[0014] A method for measuring a point spread function of an imaging device is provided in accordance with claim 15 of the appended claims.

[0015] A computer program comprising instructions which, when implemented by a computer, cause the computer to perform a method of measuring a point spread function of an imaging device is provided in accordance with claim 16 of the appended claims.

[0016] Further aspects of the invention are defined by the appended claims.

[0017] According to embodiments of the disclosure, a more accurate and reliable measurement of the PSF of an imaging device can be made. Of course, it will be appreciated that the present disclosure is not particularly limited to this advantageous technical effect. Other technical effects will become apparent to the skilled person when reading the disclosure.

[0018] The foregoing paragraphs have been provided by way of general introduction, and are not intended to limit the scope of the following claims. The described embodiments, together with further advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings.

[0019] BRIEF DESCRIPTION OF THE DRAWINGS

[0020] A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

[0021] Figure 1 illustrates an apparatus in accordance with embodiments of the disclosure;

[0022] Figure 2 illustrates an example Point Spread Function in accordance with embodiments of the disclosure;

[0023] Figure 3 illustrates an example system in accordance with embodiments of the disclosure;

[0024] Figure 4 illustrates an example filter in accordance with embodiments of the disclosure; Figure 5 illustrates an example light guiding fibre in accordance with embodiments of the disclosure;

[0025] Figure 6 illustrates an example adjustment pattern in accordance with embodiments of the disclosure;

[0026] Figure 7 illustrates an example light guiding fibre in accordance with embodiments of the disclosure;

[0027] Figure 8 illustrates an example system in accordance with embodiments of the disclosure; and

[0028] Figure 9 illustrates an example method in accordance with embodiments of the disclosure.

[0029] DESCRIPTION OF THE EMBODIMENTS

[0030] Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views.

[0031] Referring to Figure 1, an apparatus 1000 according to embodiments of the disclosure is shown. Typical ly, an apparatus 1000 according to embodiments of the disclosure is a computer device such as a personal computer or a terminal connected to a server. Indeed, in embodiments, the apparatus may also be a server. The apparatus 1000 is controlled using a microprocessor or other processing circuitry 1002. In some examples, the apparatus 1000 may be a portable computing device such as a mobile phone, laptop computer or tablet computing device.

[0032] The processing circuitry 1002 may be a microprocessor carrying out computer instructions or may be an Application Specific Integrated Circuit. The computer instructions are stored on storage medium 1004 which maybe a magnetically readable medium, optically readable medium or solid state type circuitry. The storage medium 1004 may be integrated into the apparatus 1000 or may be separate to the apparatus 1000 and connected thereto using either a wired or wireless connection. The computer instructions may be embodied as computer software that contains computer readable code which, when loaded onto the processor circuitry 1002, configures the processor circuitry 1002 to perform a method according to embodiments of the disclosure.

[0033] Additionally, an optional user input device 1006 is shown connected to the processing circuitry 1002. The user input device 1006 may be a touch screen or may be a mouse or stylist type input device. The user input device 1006 may also be a keyboard or any combination of these devices. Alternatively or in addition, the user input device 1006 may include a microphone or the like to provide a voice input instruction or command. Thus, the user input device can be an audio input device for user input.

[0034] A network connection 1008 may optionally be coupled to the processor circuitry 1002. The network connection 1008 may be a connection to a Local Area Network or a Wide Area Network such as the Internet or a Virtual Private Network or the like. The network connection 1008 may be connected to a server allowing the processor circuitry 1002 to communicate with another apparatus in order to obtain or provide relevant data. The network connection 1002 may be behind a firewall or some other form of network security.

[0035] Additionally, shown coupled to the processing circuitry 1002, is a display device 1010. The display device 1010, although shown integrated into the apparatus 1000, may additionally be separate to the apparatus 1000 and may be a monitor or some kind of device allowing the user to visualise the operation of the system. In addition, the display device 1010 may be a printer, projector or some other device allowing relevant information generated by the apparatus 1000 to be viewed by the user or by a third party.

[0036] As explained in the Background, it is often desired that the Point Spread Function (PSF) of an optical system (such as an imaging device) can be measured. For example, by measuring the PSF an indication, it is possible to obtain a measurement of the quality of the imaging system. The PSF of an imaging device can therefore be used in order to test the optical performance of an imaging device. Alternatively, the PSF of an imaging system can be measured in order to characterise the optical performance of an imaging device. The PSF of the imaging device can then be applied to computer generated images in order to more realistically simulate the images that would be captured by the imaging device in a real-world environment.

[0037] Figure 2 illustrates an example Point Spread Function in accordance with embodiments of the disclosure. Specifically, Figure 2 illustrates a theoretical PSF of an imaging device and demonstrates the effect the PSF of the imaging device may have upon any captured images.

[0038] Consider, first, panel A of Figure 2. Panel A of Figure 2 shows a small light within an environment (a point object). In this example, the small light source has a spherical shape. This spreading (or blurring) of the light arises owing to many different factors including, for example, diffraction of the light and crosstalk between different pixels within an imaging sensor of the imaging device.

[0039] Panel B of Figure 2 shows the effect of the theoretical PSF of the imaging device on the image obtained by the imaging device of the small light source of panel A of Figure 2. It can be seen that the PSF of the imaging device causes the light of the small light source to be blurred in the image (with maxima and minima of the light visible). This arises in view of the different factors described above (e.g. diffraction of the light, crosstalk between pixels) as the incoming beam from the small light source is spread over a number of neighbouring pixels.

[0040] In other words, the PSF is an image of the point source of light as imaged by the imaging device. It is a function describing the shape of a point source of light when imaged by the imaging system (e.g. describing the way in which the light is "blurred" by the imaging system (such as by diffraction of the light in an optical system)).

[0041] While Figure 2 illustrates an example theoretical PSF of an imaging device (and its effect on the images captured by the imaging device), it will be appreciated that as imaging device becomes more complex (with more optical elements, for example), the theoretical calculation of the PSF may not necessarily accurately reflect the actual PSF of the imaging device. As such, it is often desired to obtain an empirical measurement of the PSF of an imaging device.

[0042] However, using prior art methods of measuring the PSF, it can be difficult to obtain a reliable and accurate measurement of the PSF of an imaging device. This can be exacerbated when a measurement of the PSF of the imaging device at different wavelengths of light is required. Indeed, in such a situation, it can often be difficult to provide sufficient illumination to measure the PSF of the imaging device without increasing the interference in the measurement.

[0043] For at least these reasons (in addition to the reasons discussed in the Background), a system, method and computer program for measuring a point spread function of an imaging device are provided.

[0044] <System>

[0045] As explained, embodiments of the disclosure provide a system for measuring a point spread function of an imaging device. Consider, now, Figure 3 of the present disclosure. Figure 3 illustrates an example system in accordance with embodiments of the disclosure.

[0046] The system 3000 illustrated in Figure 3 is a system for measuring the point spread function (PSF) of an imaging device. The system comprises a light source 3002, a filter 3004, a light guiding fibre 3006, an adjustment 3008 and circuitry 3010.

[0047] In this example, the imaging device (of which the PSF is to be measured) is not part of the system 3000. However, in other examples, the imaging device may optionally be included as part of the system. This will be described in more detail later.

[0048] The light source 3002 of the system 3000 is configured to emit light.

[0049] The filter 3004 is configured to filter light emitted by the light source to a predetermined wavelength range.

[0050] The light guiding fibre 3006 is configured to guide light emitted by the light source and filtered by the filter along a path defined by the light guiding fibre. Light enters the light guide fibre through a first end of the light guide fibre and exits the light guide fibre through a second end of the light guide fibre. The adjustment unit 3008 of the system 3000 is configured to adjust a position of the second end of the light guiding fibre within a field of view of the imaging device (being the imaging device for which the system will measure the PSF).

[0051] Then, the circuitry 3010 of the system 3000 is configured to measure the point spread function of the imaging device when light exiting the light guiding fibre is captured by the imaging device.

[0052] In this way, light emitted from the light source 3002 is filtered by the filter 3004 and guided through the light guiding fibre to the imaging device. The adjustment unit 3008 ensures that the second end of the light guiding fibre 3006 is located at a specific point in the field of view of the imaging device (corresponding, for example, to a specific pixel on the imaging sensor of the imaging device). Furthermore, the use of the light guiding fibre 3006 with the filter 3004 enables the PSF for light of a specific wavelength band to be measured with sufficient illumination and reduced levels of optical interference. Accordingly, the system 3000 enables a more accurate and reliable measurement of the PSF of an imaging device.

[0053] Embodiments of the disclosure are not particularly limited to the example system 3000 described with reference to Figure 3 of the present disclosure. For example, a number of additional elements may be included within the system 3000. Indeed, while the example of Figure 3 is described with reference to a single fibre, other examples of the disclosure included multiple fibres (such as a bundle of fibres). Therefore, it will be appreciated that the example of Figure 3 is provided only as an example of a system in accordance with embodiments of the disclosure and is not limiting to the scope of protection as defined by the claims.

[0054] Further details of a system for measuring the PSF of an imaging device (or other optical system) will now be described.

[0055] <Light Source>

[0056] As explained with reference to Figure 3 of the present disclosure, the system 3000 comprises a light source 3002, the light source 3002 being configured to emit light.

[0057] The type of light source used in accordance with embodiments of the disclosure is not particularly limited. That is, owing the use of the filter 3004, there is no requirement specifically for the light source 3002 to emit light of any particular wavelength range. Furthermore, owing to the use of the light guiding fibre, there is no requirement specifically for the light source 3002 to emit light in a particular direction or over a particular area. Therefore, the type of light source 3002 used in the system 3000 may vary in accordance with the specific situation to which the embodiments of the disclosure are applied. Indeed, in some examples, the light source 3002 may be a broadband light source. A broadband light source is configured to emit light over a wide range of different wavelengths. Halogen lamps, xenon gas discharge lamps or white light LEDs are examples of broadband light sources which can be used in accordance with embodiments of the disclosure.

[0058] Advantageously, use of a broadband light source makes it easier and more efficient to obtain the PSF for different wavelengths of light. That is, the filter 3004 of the system 3000 can filter the light emitted from the light source to a predetermined wavelength range for measurement of the PSF of the imaging device. This means that a same broadband light source can be used (with a different filter) in order to measure the PSF of the imaging device in different wavelength ranges.

[0059] However, any suitable light source 3002 can be used in accordance with embodiments of the disclosure, provided that it is able to emit light of the wavelength for which the PSF of the imaging device should be measured. Furthermore, the light source should emit light with sufficient intensity across all wavelength ranges in order that the PSF of the desired wavelength range can be measured reliably. That is, as the light emitted from the light source is filtered by a filter on the light source side, there is no restriction on the type of light source which is used in order to produce the light. Therefore, a very bright light source can easily be used enabling sufficient illumination power to be provided for a reliable measurement of the PSF (i.e. with sufficient intensity for the imaging device) even when very narrow band filters (bandwidth) are used.

[0060] In some examples, the light source 3002 may be a collimated light source. In examples, collimation of the light emitted by the light source 3002 may be achieved through the use of one or more additional optical elements coupled to the light source.

[0061] The purpose of the light source 3002 is to emit light which can be detected by an imaging device in order that the PSF of the imaging device can be measured. However, in contrast to prior art methods for measurement of the PSF, the light source 3002 does not have to be a point source nor does it have to emit light in any particular wavelength range. Rather, the light from the light source 3002 passes through the filter 3004 and the light guiding fibre 3006 which enables the light from the light source 3002 to be filtered and guided in a manner such that it is suitable for measurement of the PSF in a desired wavelength range. This increases flexibility in design of the system 3000 and enables different types of light sources (such as broadband light sources) to be used.

[0062] <Filter> As explained with reference to Figure 3 of the present disclosure, the system 3000 comprises a filter 3004. The filter 3004 is configured to filter light emitted by the light source to a predetermined wavelength range.

[0063] The light source 3002 is configured to emit light. The filter 3004 is then coupled to this light source 3002 (on the light source side of the light guiding fibre 3006) and filters the light emitted by the light source 3002 such that only filtered light from the light source enters the light guiding fibre 3006. The light when filtered by the filter 3004 has a predetermined wavelength range (being the wavelength of light for which the PSF of the imaging device is to be measured).

[0064] In some examples, the light emitted by the filter may have a certain profile over the wavelength range that passes through the filter. That is, the light passing through the filter may have a non-uniform intensity or power over the range. However, the present disclosure is not particularly limited in this respect.

[0065] As the filter 3004 is on the light source side, the angular dependency of the filter does not impact the measurement of the PSF of the imaging device. That is, the filter can be coupled to the light source 3002 (with or without additional optical elements). Indeed, as the filter is on the light source side, the light source, the filter and the plurality of light guiding fibres can be aligned in a straight line. As such, light that is coupled to the fibre is passing through the filter perpendicularly. The other end of the fibre (on the imaging device side) can then be positioned freely in the field of view (FoV) of the imaging device.

[0066] This negates the effect of the angular dependency of the filter as all light coupled into the fibre is passing through the filter perpendicularly. As such, by placing the filter 3004 on the light source side, the effect of angular dependency of the filter can be reduced.

[0067] In contrast, if the filter was located on the imaging device, the light would only pass through the filter perpendicularly in the centre of the FoV of the imaging device. Thus, the angular dependency of the filter would have a higher impact on the measurement of the PSF of the imaging device.

[0068] The type of filter used to filter the light is not particularly limited. The filter may be a narrowband filter which filters the light emitted by the light source 3002 to a narrow wavelength range. This enables the PSF of a specific wavelength of light to be measured for the imaging device.

[0069] That is, the filter 3004 of the present disclosure is configured to filter the light emitted by the light source 3002 to a predetermined wavelength band. This predetermined wavelength band may include a narrow band wavelength range. That is, the filter 3004 is configured to filter the broadband light emitted by light source 3002 to a specific wavelength range at which the measurement of the PSF of the imaging device should be made. In examples, the system 3000 may be preconfigured with a filter of a specific wavelength range. This would calibrate the system 300 for measurement of the PSF of an imaging device at a particular wavelength range. However, in other examples, the filter 3004 may be an exchangeable filter. This enables a different filter to be used (having a different wavelength range) in order to enable the PSF of the imaging device to be more easily measured in a different wavelength range. That is, for example, a first filter (having a first predetermined wavelength range) may be used in order to obtain a measurement of the PSF of the imaging device at the first predetermined wavelength range. Then, once this measurement has been obtained, the filter may be replaced (either manually or automatically) in order to provide a second filter having a second (different) predetermined wavelength range. This second filter 3004 may then be used in order to obtain a measurement of the PSF of the imaging device at the second predetermined wavelength range.

[0070] In this way, measurement of the PSF of the imaging device for multiple different wavelengths of light can be easily performed. Indeed, as the filter is provided on the light source side of the system, it is easy to replace the filter within the system without affecting the calibration of the other elements of the system 3000.

[0071] The narrower the bandwidth of the filter, the more precisely the PSF of the imaging device can be measured (i.e. for a specific wavelength of light). However, a narrower filter will cause a reduction in the intensity of the light reaching the imaging device (because more light is blocked by the filter). Therefore, the intensity of the light source should be configured to provide sufficient illumination power to achieve sufficient intensity on the sensor for the bandwidth of the filter being used.

[0072] In some examples the filter 3004 may comprises a filter wheel.

[0073] Consider, now, Figure 4 of the present disclosure. Figure 4 of the present disclosure illustrates an example filter in accordance with embodiments of the disclosure.

[0074] The example filter 4000 shown in Figure 4 of the present disclosure is a filter wheel. There are a number of different segments on the filter wheel 4000. These segments include segment 4002 and segment 4004 of the filter wheel.

[0075] The number of different segments on the filter wheel is not particularly limited. That is, while four different segments are illustrated in Figure 4 (including segment 4002 and 4004), there may be many more segments on the filter wheel. Alternatively, the number of segments on the filter wheel may be less than that shown in Figure 4.

[0076] A number of the different segments of the filter wheel may include a filter configured to filter light to a different wavelength range. That is, for example, the segment 4002 may include a filter to filter light to a first predetermined wavelength range. The second segment 4004 may include a filter to filter light to a second predetermined wavelength range (with the second predetermined wavelength range being different from the first wavelength range).

[0077] The filter wheel 4000 may be rotatable around an axis as illustrated in Figure 4. In this way, a different segment of the filter wheel 4000 may be brought into alignment between the light source and the 3002 and the light guiding fibre 3006, in order to change the segment of the filter through which light emitted by the light source 3002.

[0078] The filter wheel may be automatically rotatable (e.g. under control of circuity 3010). Alternatively, the filter wheel may be manually rotatable (e.g. by a person operating system 3000 to measure the PSF of an imaging device).

[0079] Thus, examples of the present disclosure provide a filter comprising a filter wheel, wherein the filter wheel is configured to be rotatable to change the predetermined wavelength range.

[0080] In this way, the filter can be quickly and easily changed thus enabling measurement of the PSF of the imaging device for multiple different wavelengths of light to be easily performed.

[0081] <Light Guiding Fibre>

[0082] As explained with reference to Figure 3 of the present disclosure, the system 3000 comprises a light guiding fibre 3006.

[0083] The light guiding fibre 3006 is configured to guide light emitted by the light source and filtered by the filter along a path defined by the light guiding fibre. Light enters the light guide fibre through a first end of the light guide fibre and exits the light guide fibre through a second end of the light guide fibre.

[0084] Consider again Figure 3 of the present disclosure. In this example, the first end of the light guide fibre is the end of the light guide fibre closest to the filter 3004. Light emitted by the light source 3002 passes through the filter 3004 and enters the light guide fibre 3006 through this end of the light guide fibre 3006.

[0085] Light then passes through the light guide fibre 3006 and exits the light guide fibre 3006 through the second end of the light guiding fibre 3006 (being the end closest to the imaging device).

[0086] In this way, light emitted by the light source 3002 and filtered by the light source 3004 passes along a path defined by the light guiding fibre 3006. This enables the light guiding fibre 3006 to direct the light from the light source 3002 to a specific part of the field of view of the imaging device, enabling precise measurement of the PSF of the imaging device at a specific portion of the field of view of the imaging device. In other words, the light guiding fibre 3006 is therefore used to distribute the light from the light source 3002 to a specific part of the field of view of the imaging device which requires illumination for the measurement of the PSF.

[0087] In some examples, the light guiding fibre 3006 is made of a transparent material (such as glass or plastic) which directs the light along a path inside the light guiding fibre 3006 by internal reflections.

[0088] For example, the light guiding fibre 3006 may include a fibre optic light guide. However, the present disclosure is not particularly limited in this regard.

[0089] In examples, the light guiding fibre 3006 may be a flexible light guiding fibre. However, in other examples, the light guiding fibre 3006 may be a rigid light guiding fibre.

[0090] In examples, the system 3000 may further comprise a first optical element configured to couple light emitted by the light source and filtered by the filter with the first end of the light guiding fibre. Consider again the example illustrated with reference to Figure 3 of the present disclosure. In some examples, a first optical element may be included between the filter 3004 and the first end of the light guiding fibre 3006 (i.e. the end closest to the filter (that is, one the light source side of the light guiding fibre 3006)). The purpose of the optical element may be to collect light as it passes through the filter 3004 and direct that light into the optical fibre 3006 (thus coupling the light guiding fibre 3006 with the light emitted by the light source 3002 once it has been filtered by the filter 3004). This may further improve transmission of light from the light source 3002 to the imaging device for measurement of the PSF.

[0091] In examples, a single light guiding fibre 3006 may be used. This enables light from the light source to be directed to a single precise location within the field of view of the imaging device, such that the PSF of the imaging device at that specific location within the field of view can be measured. However, in other examples, the light guiding fibre 3006 may include a collection or bundle of light guiding fibres 3006. That is, in examples, more than one light guiding fibre 3006 may be provided. Accordingly, in embodiments of the disclosure, the system 3000 comprises a plurality of the light guiding fibres, and the adjustment unit is configured to independently adjust a position of each of the plurality of light guiding fibres within a field of view of the imaging device.

[0092] Thus, by using multiple fibres, the PSF of the imaging device at multiple locations within the field of view of the imaging device may be measured at the same time (since each fibre directs the light to a specific portion of the field of view of the imaging device).

[0093] Control of the different fibres by the adjustment unit 3008 of system 3000 will be described in more detail later. In some examples, when multiple fibres are provided, an optical element may be included to couple light emitted by the light source 3002 and filtered by the filter 3004 with the first end of the light guiding fibre. Indeed, in this case, the optical element may include a fibre coupler. The fibre coupler may be a device to enable input light (from the light source 3002) to be split along multiple different transmission paths (i.e. through multiple different light guiding fibres). This enables the light for the light source to be easily and efficiently transmitted to different portions of the field of view of the imaging device for measurement of the PSF.

[0094] However, it will be appreciated that while multiple light guiding fibres may be provided (such as a bundle of light guiding fibres) the present disclosure is not particularly limited in this respect. Indeed, in examples, a single light guiding fibre 3006 may be provided in system 3000.

[0095] It will be appreciated that the use of the light guiding fibre 3006 provides an easy and efficient way in which a point source of light can be created within the field of view of the imaging device for measurement of the PSF. Consider again Figure 2 of the present disclosure. The measurement of the PSF can be made by identifying how a point source of light (such as that shown in panel A of Figure 2) appears in an image of that point source of light captured by the imaging device (such as that shown in panel B of Figure 2). The use of a light guiding fibre 3006 (or multiple light guiding fibres) thus provides an easy way of generating a point source of light for measurement of the PSF of an imaging device.

[0096] In examples, a diameter of the light guiding fibre is configured to be smaller than a size of a pixel in the imaging sensor of the imaging device, when projected into object space. That is, the light guiding fibre may have a diameter easily much smaller than 1 pixel in object space for an imaging device to be measured. Thus, the light guiding fibre 3006 enables the PSF of the imaging device to be precisely measured at very specific portions of the field of view of the imaging device (i.e. at different positions across an imaging sensor of the imaging device). Likewise, the fibre may (when projected into image space) have a size smaller than 1 pixel of the imaging device.

[0097] Adjustment Unit>

[0098] As explained, the system 3000 further comprises an adjustment unit 3008. The adjustment unit is configured to adjust a position of the second end of the light guiding fibre within a field of view of the imaging device.

[0099] In some examples, the adjustment unit 3008 may comprise a holding structure considered to position the light guiding fibre 3006 precisely in the field of view of the imaging device. This ensures that the light guiding fibre 3006 does not move during measurement of the PSF enabling a more accurate measurement of the PSF to be made. Consider now Figure 5 of the present disclosure. Figure 5 illustrates an example light guiding fibre in accordance with embodiments of the disclosure.

[0100] In this example, a single light guiding fibre 3006 is shown. Furthermore, an imaging device for which the PSF is to be measured is also shown. The distance d between the second end of the light guiding fibre 3006 and the imaging device is shown. The imaging device is held in its position by the adjustment unit 3008 (not shown in this example).

[0101] The adjustment unit 3008 holds the light guiding fibre 3006 in a particular position for measurement of the PSF of the imaging device. For example, the adjustment unit 3008 is configured to hold the second end of the light guiding fibre 3006 such that the light from the light guiding fibre 3006 is directed towards the imaging device (i.e. such that the light guiding fibre points towards the imaging device). In addition, the adjustment unit 3008 is configured to hold the light guiding fibre 3006 such that it remains at a fixed distance d from the imaging device for the duration of the measurement. This ensures that the size of the light guiding fibre 3006 in object space remains constant for the duration of the measurement.

[0102] Furthermore, the adjustment unit 3008 may be configured to adjust a position of the second end of the light guiding fibre within a field of view of the imaging device. This enables the PSF of the imaging device to be measured at a specific position within the field of view of the imaging device (e.g. at a location corresponding to a specific pixel of the imaging sensor of the imaging device). Indeed, by adjusting the position of the second end of the light guiding fibre within the field of view of the imaging device, the PSF of the imaging device can be measured at different locations within the field of view of the imaging device. This enables variations of the PSF of the imaging device across the field of view of the imaging device to be easily identified.

[0103] In examples, the adjustment unit 3008 is configured to adjust a position of the light guiding fibre under control of the circuitry. For example, the adjustment unit 3008 may include a holding structure to hold the light guiding fibre 3006 at a specific position within the field of view of the imaging device. Furthermore, the adjustment unit 3008 may include an actuator which enables the position of the holding structure to be changed (i.e. to change a position of the light guiding fibre to be changed). The actuator may be under control of the circuitry 3010 of system 3000. This enables the position of the light guiding fibre to be automatically changed to a position within the field of view of the imaging device in order to enable easy and efficient measurement of the variation of the PSF of the imaging device across the field of view of the imaging device to be made. In such an example, the type of actuator is not particularly limited. Any suitable actuator which enables movement of the light guiding fibre 3006 under control of the circuitry 3010 may be used in accordance with embodiments of the disclosure.

[0104] In other example, the adjustment unit 3008 may be adjustable under manual control. This may include direct manipulation of the adjustment unit and / or control of an actuator to control a position of the light guiding fibre 3006 at a specific position within the field of view of the imaging device.

[0105] In examples, the adjustment unit may be configured to adjust the position of the light guiding fibre within the field of view of the imaging device in order to measure the PSF of the imaging device at different locations within the field of view of the imaging device (relating to different pixels on an imaging sensor of the imaging device, for example).

[0106] Consider Figure 6 of the present disclosure. Figure 6 illustrates an example adjustment pattern in accordance with embodiments of the disclosure.

[0107] Specifically, in the example of Figure 6, an example imaging sensor of an imaging device is shown. The example imaging sensor comprises 3 columns of pixels (1 to 3) each column comprising 6 rows of pixels (A to F).

[0108] An example adjustment pattern of the light guiding fibre 3006 is shown. In this example, the adjustment unit 3008 is configured to adjust the position of the light guiding fibre 3006 such that a measurement of the PSF of the imaging device at the pixel 1A is made (i.e. the first column of the first row). Then, the adjustment unit 3008 is configured to adjust the position of the light guiding fibre 3006 such that a measurement of the PSF of the imaging device at pixel 2A can be made (i.e. the second column of the first row). Then, the adjustment unit 3008 is configured to adjust the position of the light guiding fibre 3008 to a position corresponding to pixel 3A, such that measurement of the PSF can be made at position 3A (corresponding to the third column of the first row).

[0109] Once measurement of the PSF of the imaging device has been made at each position within the first row A, the adjustment unit may adjust the position of the light guiding fibre 3006 such that the measurement of pixels in the subsequent rows (B to F) can be made in the same way.

[0110] In this manner, the adjustment unit 3008 is configured to adjust the position of the light guiding fibre 3006 in an adjustment or scan pattern within the field of view of the imaging device, such that measurement of the PSF of the imaging device at different locations can be made (using only a single light guiding fibre 3006). Furthermore, for each position, different measurements can be made (corresponding to different image data from the imaging device) for different wavelengths of light by changing the filter 3004 used to filter the light from the light source 3002. It will be appreciated that the present disclosure is not particularly limited to this example. Indeed, in some examples, a single measurement of the PSF of the imaging device may be made at a single location within the field of view of the imaging device. This single measurement of the PSF may then be used as a representative measurement of the PSF of the imaging device across all possible locations.

[0111] In other examples, multiple measurements may be made at multiple sample locations across the field of view of the imaging device, with each measurement being used as a representative measurement of the PSF for a given region or area of the field of view of the imaging device. For example, a single measurement may be made for each row of the imaging device (using, for example, the second column).

[0112] Alternatively, a measurement of the PSF of the imaging device may be made at each possible location within the field of view of the imaging device (i.e. at least one measurement per pixel of the imaging sensor of the imaging device). In such an example, the adjustment unit 3008 may be configured to adjust the position of the light guiding fibre 3006 within the field of view of the imaging device using a scan pattern such as that illustrated with reference to Figure 6 of the present disclosure. However, a scan pattern different from that illustrated with reference to Figure 6 of the present disclosure may also be used. For example, the adjustment unit 3008 may be configured to adjust the position of the light guiding fibre 3006 at a position corresponding to each row within a given column (i.e. rows A to F of column 1 of Figure 6) before moving to the next column of the imaging sensor (i.e. columns 2 and 3 of the imaging sensor of Figure 6).

[0113] Furthermore, it will be appreciated that while the imaging sensor of Figure 6 is illustrated with 18 different pixels (i.e. 3 columns and 6 rows) the present disclosure is not particularly limited in this regard. The imaging sensor of an imaging device for which the measurement of the PSF is made may have a different number of pixels that illustrated in Figure 6. For example, the imaging device may have many more pixels than illustrated in Figure 6 of the present disclosure, with the adjustment unit 3008 being configured to adjust the position of the light guiding device 3006 accordingly.

[0114] Furthermore, while the examples of Figures 5 and 6 of the present disclosure have been described with reference to a single light guiding fibre 3006, it will be appreciated that the present disclosure is not particularly limited in this regard. Indeed, in examples, multiple light guiding fibres (such as a bundle of light guiding fibres 3006) may be provided. In this case, the adjustment unit 3008 may be configured to independently adjust a position of each of the plurality of light guiding fibres within a field of view of the imaging device.

[0115] Consider, now, the example of Figure 7 of the present disclosure. Figure 7 illustrates an example light guiding fibre in accordance with embodiments of the disclosure. Specifically, in the example of Figure 7, multiple light guiding fibres 3006A to 3006C are shown. In this example, each of the light guiding fibres 3006A, 3006B and 3006C are configured to direct light from the light source 3002 to a specific position within the field of view of the imaging device. The light guiding fibres 3006, 3006B and 3006C may be independently adjustable within the field of view of the imaging device by the adjustment unit 3008. Alternatively, the adjustment unit 3008 may be configured to adjust the position of the light guiding fibres 3006 to 3006C while retaining a fixed relative position between the respective light guiding fibres.

[0116] In examples, independently adjusting the position of each of the plurality of light guiding fibres (such as light guiding fibres 3006A, 3006B and 3006C) may comprise setting different fibres of the plurality of light guiding fibres at different distances from the imaging device. This enables the measurement of the PSF of the imaging device at different distances simultaneously.

[0117] In this example, each light guiding fibre directs light to a different pixel of the imaging sensor of the imaging device. That is, light guiding fibre 3006A directs light to a first pixel 7000 of the imaging sensor, light guiding fibre 3006B directs light to a second pixel 7002 of the imaging sensor and light guiding fibre 3006C directs light to a third pixel 7004 of the imaging sensor.

[0118] In this way, the adjustment unit 3008 of system 3000 is configured to adjust the position of the light guiding fibres 3006A to 3006C within the field of view of the imaging device such that multiple measurements of the PSF of the imaging device can be made accurately and reliably at different locations across the field of view of the imaging device at the same time. Furthermore, as the light guiding fibres are small with respect to the pixels of the imaging sensor (with the size of the light guiding fibre being smaller than a single pixel of the imaging sensor in the object plane) multiple simultaneous measurements of the PSF can be made at different locations across the field of view of the imaging sensor without interference between the respective light guiding fibres.

[0119] In examples, a scan pattern such as that described with reference to the example of Figure 6 of the present disclosure may be used by the adjustment unit 3008 when measuring the PSF of the imaging device using multiple light guiding fibres 3006.

[0120] Of course, it will be appreciated that the present disclosure is not limited to the specific example described with reference to Figure 7 of the present disclosure. That is, in examples, even when multiple light guiding fibres are used (as opposed to a single light guiding fibre) the number of light guiding fibres may be different than that illustrated in Figure 7. For example, many more light guiding fibres may be included than shown in the example of Figure 7.

[0121] In some examples, adjustment unit may be further configured to adjust one or more properties related to the imaging device (in addition to the adjustment of the light guiding fibre 3006). Indeed, the adjustment unit may be configured to adjust at least one of: a viewing direction of the imaging device, a focus of the imaging device and / or a distance between the second end of the light guiding fibre and the imaging unit (by adjustment of the position of the imaging device).

[0122] In such an example, accuracy and reliability of measurement of the PSF of the imaging device may further be improved, as the imaging device may be configured in a manner most suitable for measurement of PSF (e.g. by ensuring that the light guiding fibre 3006 is in focus for the imaging device). Indeed, such adjustment by the adjustment unit 3008 may optionally be made under the control of the circuitry 3010 of system 3000.

[0123] <Circuitry>

[0124] As explained, system 3000 further comprises circuitry 3010. The circuitry 3010 is configured to measure the point spread function of the imaging device when light exiting the light guiding fibre is captured by the imaging device.

[0125] The circuitry may include processing circuitry such as processing circuitry 1002 as described with reference to Figure 1 of the present disclosure. In particular, in examples the processing circuitry 3010 may be a microprocessor carrying out computer instructions or may be an Application Specific Integrated Circuit. In examples, computer instructions may be stored on a storage medium which maybe a magnetically readable medium, optically readable medium or solid state type circuitry. In examples, the circuitry may be on a server side.

[0126] In examples, the circuitry 3010 may be configured to control the imaging device in order to capture light emitted by the light guiding fibre. That is, the circuitry may be configured to control the imaging device to capture an image or image data of the appearance of the light guiding fibre within the field of view of the imaging device. For example, the circuitry 3010 may be configured to control the imaging device in order to capture an image such as the image of panel B of Figure 2. The PSF of the imaging device can then be determined, by the circuitry 3010, from this image data. This will be described in more detail below.

[0127] Alternatively, however, the circuitry 3010 may not control the imaging device. That is, the imaging device itself may be configured to capture images (or imaging data). In examples, the imaging device may continually capture imaging data. In other examples, the imaging device may be configured to periodically capture imaging data.

[0128] Once the images (or imaging data) have been captured by the imaging device, circuitry 3010 may then access this data. For example, circuitry 3010 may be communicatively coupled with the imaging device and receive the data directly from the imaging device (e.g. using a wired or wireless connection). Alternatively, the circuitry may access a storage in which the imaging device records the images and retrieve the data from that storage.

[0129] As explained, the adjustment unit 3008 is configured to adjust the position of the light guiding fibre 3006 within the field of view of the imaging device. Therefore, the light emitted from the second end of the light guiding fibre (the end on the imaging device side) forms a point source of light within the field of view of the imaging device. In particular, the light guiding fibre may have a diameter smaller than one pixel of the imaging sensor of the imaging device in the object plane. Therefore, the light emitted from the light guiding fibre forms a point source of light.

[0130] Thus, each light guiding fibre present (being either a single light guiding fibre or multiple light guiding fibres) provides a light source such as that described with reference to panel A of Figure 2.

[0131] However, the light emitted from the light guiding fibre will not be recorded as a perfect point source of light by the imaging device. Instead, the PSF of the imaging device will affect the appearance of the point source of light in the images captured by the imaging device. Indeed, the PSF of the imaging device causes the light emitted from the light guiding fibre to be blurred in the image (with maxima and minima of the light visible).

[0132] A number of different factors and properties of the imaging device contribute to the PSF of the imaging device. For example, diffraction of the light as it passes through the optical elements of the imaging device (such as a lens of the imaging device) contributes to the PSF of the imaging device. Furthermore, properties of the image sensor of the imaging device also contribute to the PSF of the imaging device. For example, crosstalk between pixels of the imaging device as the incoming beam from light guiding fibre is spread over a number of neighbouring pixels contributes to the PSF of the imaging device.

[0133] Therefore, the image of the light emitted by the light guiding fibre 3006 captured by the imaging device will have an appearance similar to the example shown in panel B of Figure 2 of the present disclosure (where the light from the light guiding fibre has been "blurred" by the PSF of the imaging device).

[0134] The circuitry 3010 is thus configured to measure the PSF of the imaging device when light exiting the light guiding fibre is captured by the imaging device (e.g. from an image such as that shown in panel B of Figure 2 of the present disclosure). Indeed, as it is known that the light guiding fibre 3006 provides a point source of light in the field of view of the imaging device (with the position of the light guiding fibre being set by the adjusting unit) the circuitry is able to apply one or more calculations to the image data from the image capture device in order to empirically measure the PSF of the imaging device (at that location and for the predetermined wavelength of light) from the appearance of the light source within the image data. Thus, the PSF of the imaging device can be obtained by the circuitry 3010. In examples, the circuitry may be configured to capture a plurality of images of a fibre at different intensities by adjusting the light source power or camera exposure settings. These different images of the fibre (at the different intensities) may then be stacked to produce HDR-images of the fibre. This may enable a more accurate calculation of the PSF of the imaging device to be performed.

[0135] The calculation or calculations performed by the circuitry 3010 in order to reconstruct the PSF of the imaging device from the captured images are not particularly limited. In examples, the Modulation Transfer Function (MTF) may be calculated from the PSF at a given position. In examples, vignetting and / or field curvature may be calculated from a number of PSF measurements. Therefore, the present disclosure is not particularly limited in this respect.

[0136] In examples, the circuitry 3010 may be configured in order to decouple the respective contribution of different portions of the imaging device to the PSF of the imaging device. For example, if the PSF of the imaging sensor of the imaging device is known (e.g. from prior measurement or theoretical calculation) then the contribution of the imaging sensor to the PSF of the imaging device can be accounted for by the circuitry 3010, enabling the circuitry 3010 to identify the PSF of the optical elements of the imaging device (e.g. the lens or lens system of the imaging device). Thus, in embodiments, the system 3000 can be used in order to measure the PSF of a lens or lens system which is part of the imaging device.

[0137] <Example lmplementation>

[0138] Consider now Figure 8 of the present disclosure. Figure 8 illustrates an example system in accordance with embodiments of the disclosure. The example system shown in Figure 8 may be considered as an example implementation of the system 3000 described with reference to Figure 3 of the present disclosure.

[0139] In Figure 8 of the present disclosure, the system for measuring the PSF of an imaging device comprises a Fibre Source. The Fibre source is, in this example, a light source configured to emit light for use in the measurement of the PSF. In examples, the light emitted by the Fibre source (i.e. the light source) is broadband light.

[0140] In Figure 8, the light which has been emitted passes through the Filter. The Filter filters the light which has been emitted such that only light of a predetermined wavelength passes through the filter. This may include a narrowband range of light (small wavelength range) to enable the PSF of the imaging device to be measured at a specific wavelength range. In the example of Figure 8, the Filter is an exchangeable filter which enables the wavelength range to be easily selectable. The system of Figure 8 includes a Fibre coupler. The Fibre coupler enables input light (from the light source) to be split along multiple different transmission paths (i.e. through a plurality of different light guiding fibres).

[0141] The system of Figure 8 includes a plurality of light guiding fibres. These light guiding fibres direct the light from the light source to a specific portion of the field of view of the imaging device to be measured. This enables the PSF of the imaging device to be measured at a specific portion of the field of view of the imaging device (corresponding to a specific pixel or group of pixels of the image sensor of the imaging device).

[0142] An adjustment unit (not shown in Figure 8) is used to adjust the position of the plurality of light guiding fibres. Furthermore, the adjustment unit holds the light guiding fibres in a specific position during the measurement of the PSF of the imaging device.

[0143] Furthermore, circuitry of the system (not shown in Figure 8) measures the point spread function of the imaging device (for each of the plurality of light guiding fibres) when light exiting the light guiding fibre is captured by the imaging device. As explained, each light guiding fibre provides a single point source of light in the field of view of the imaging device. Therefore, by measuring the appearance of the point source of light (e.g. how spread out the point source appears) in image data captured by the imaging device it is possible to obtain the PSF of the imaging device.

[0144] The system of Figure 8 further includes a camera. The camera is an example of an imaging device. The camera is the imaging device for which the PSF is to be measured. This may be in order to test the optical performance of the camera. Alternatively, this may be to understand the PSF of the camera, in order that the PSF of the camera can be applied to computer generated and / or simulated images, to provide a realistic resultant image (with the appearance as if the computer generated or simulated image had been captured by the real camera).

[0145] In examples, the camera includes an imaging sensor to capture images and a second optical element (e.g. a lens or set of lenses) configured to focus light on the imaging sensor.

[0146] In examples, the adjustment unit of the system of Figure 8 (not shown) may control the camera in addition to controlling the light guiding fibres. For example, the adjustment unit may change a position of the camera and / or a position of the light guiding fibres in order to adjust a distance between the camera and the light guiding fibres.

[0147] In this way, an example system such as that illustrated in Figure 8 of the present disclosure may be used in order to measure the PSF of an imaging device. It will be appreciated that the present disclosure is not particularly limited to the example implementation shown in Figure 8 of the present disclosure.

[0148] As an example, while Figure 8 shows multiple light guiding fibres coupled to a single light source, it will be appreciated that the present disclosure is not particularly limited in this regard. In examples, a single light guiding fibre may be coupled to the single light source. Then, the PSF of the imaging device can (optionally) be measured at different locations across the field of view of the imaging device through adjustment of the position of the light guiding fibre by the adjusting unit (e.g. using a scan pattern as described with reference to Figure 6 of the present disclosure). In an example, multiple different light sources may be provided, each of those light sources coupled (through a filter and fibre coupler) to one or more light guiding fibres. This enables different wavelengths of light to be measured at the same time by the imaging device. In other words, a plurality of systems such as that shown in Figure 8 of the present disclosure may be provided for measurement of a single imaging device (enabling multiple measurements at different frequencies of light to be taken at the same time).

[0149] More generally, embodiments of the present disclosure are defined by the appended claims.

[0150] <Method>

[0151] A method of measuring a point spread function of an imaging device is provided in accordance with embodiments of the disclosure.

[0152] Figure 9 illustrates a method of measuring a point spread function of an imaging device. The method of Figure 9 starts at step S9000 and proceeds to step S9002.

[0153] In step S9002, the method comprises emitting light from a light source.

[0154] Then, in step S9004, the method comprises filtering the light emitted by the light source to a predetermined wavelength range with a filter.

[0155] In step S9006, the method comprises guiding light emitted by the light source and filtered by the filter along a path defined by the light guiding fibre, wherein the light enters the light guide fibre through a first end of the light guide fibre and exits the light guide fibre through a second end of the light guide fibre.

[0156] Then, in step S9008, the method comprises adjusting a position of the second end of the light guiding fibre within a field of view of the imaging device.

[0157] Finally, in step S9010, the method comprises measuring the point spread function of the imaging device when light exiting the light guiding fibre is captured by the imaging device. The method then proceeds to, and ends with, step S9012.

[0158] In examples, the method of Figure 9 may be performed by a system 3000 as described with reference to Figure 3 of the present disclosure and / or by an apparatus 1000 as described with reference to Figure 1 of the present disclosure. In examples, a computer program may also be provided, comprising instructions which, when implemented by a computer (or a system 3000 and / or apparatus 1000 described with reference to Figures 3 and 1 of the present disclosure respectively) cause the computer to perform a method of the present disclosure.

[0159] Concerning the example of Figure 9, it will be appreciated that the present disclosure is not specifically limited to the example method illustrated with reference to this Figure. That is, while the individual steps of the method of Figure 9 are shown in sequence, the present disclosure is not particularly limited in this regard. The steps of the method of Figure 9 may be performed in a different order to that illustrated in this Figure. Alternatively, or in addition, a number of the steps may be performed in parallel. Alternatively or in addition, a number of additional steps may be included. Alternatively or in addition, one or more steps of the method of Figure 9 may be repeated a number of times.

[0160] <Clauses>

[0161] Furthermore, embodiments of the disclosure can be arranged in accordance with the following numbered clauses:

[0162] 1) A system for measuring a point spread function of an imaging device, the system comprising: a light source configured to emit light, a filter configured to filter light emitted by the light source to a predetermined wavelength range, a light guiding fibre configured to guide light emitted by the light source and filtered by the filter along a path defined by the light guiding fibre, wherein light enters the light guide fibre through a first end of the light guide fibre and exits the light guide fibre through a second end of the light guide fibre; an adjustment unit configured to adjust a position of the second end of the light guiding fibre within a field of view of the imaging device; and circuitry, wherein the circuitry is configured to measure the point spread function of the imaging device when light exiting the light guiding fibre is captured by the imaging device.

[0163] 2) The system according to clause 1, further comprising a first optical element configured to couple light emitted by the light source and filtered by the filter with the first end of the light guiding fibre.

[0164] 3) The system according to clause 2, wherein the first optical element is a fibre coupler. 4) The system according to any of clauses 1 to 3, wherein the filter is an exchangeable filter.

[0165] 5) The system according to any of clauses 1 to 3, wherein the filter comprises a filter wheel, wherein the filter wheel is configured to be rotatable to change the predetermined wavelength range.

[0166] 6) The system according to any preceding clause, wherein the predetermined wavelength range is a narrow band wavelength range.

[0167] 7) The system according to any preceding clause, wherein the light source is a broadband light source configured to emit collimated light in a broadband wavelength range.

[0168] 8) The system according to any preceding clause, wherein the adjustment unit is configured to adjust a position of the light guiding fibre under control of the circuitry.

[0169] 9) The system according to any preceding clause, wherein the system comprises a plurality of the light guiding fibres, and wherein the adjustment unit is configured to independently adjust a position of each of the plurality of light guiding fibres within a field of view of the imaging device.

[0170] 10) The system according to clause 9, wherein independently adjusting the position of each of the plurality of light guiding fibres comprises setting different fibres of the plurality of light guiding fibres at different distances from the imaging device.

[0171] 11) The system according to any preceding clause, further comprising the imaging device.

[0172] 12) The system according to clause 11, wherein the imaging device comprises an imaging sensor and a second optical element.

[0173] 13) The system according to clause 12, wherein a diameter of the light guiding fibre is configured to be smaller than a size of a pixel in the imaging sensor of the imaging device projected into object space and / or the size of the pixel is configured to be smaller than a diameter of the light guiding fibre projected into image space.

[0174] 14) The system according to any of clauses 11 to 13, wherein the adjustment unit is further configured to adjust at least one of: a viewing direction of the imaging device, a focus of the imaging device and / or a distance between the second end of the light guiding fibre and the imaging unit.

[0175] 15) A method of measuring a point spread function of an imaging device, the method comprising: emitting light from a light source; filtering the light emitted by the light source to a predetermined wavelength range with a filter; guiding light emitted by the light source and filtered by the filter along a path defined by the light guiding fibre, wherein the light enters the light guide fibre through a first end of the light guide fibre and exits the light guide fibre through a second end of the light guide fibre; adjusting a position of the second end of the light guiding fibre within a field of view of the imaging device; and measuring the point spread function of the imaging device when light exiting the light guiding fibre is captured by the imaging device.

[0176] 16) A computer program comprising instructions which, when implemented by a computer, cause the computer to perform a method of measuring a point spread function of an imaging device, the method comprising: controlling a light source to emit light; controlling a filter to filter the light emitted by the light source to a predetermined wavelength range; controlling a light guide fibre to guide light emitted by the light source and filtered by the filter along a path defined by the light guiding fibre, wherein the light enters the light guide fibre through a first end of the light guide fibre and exits the light guide fibre through a second end of the light guide fibre; controlling an adjustment unit to adjust a position of the second end of the light guiding fibre within a field of view of the imaging device; and controlling measurement of the point spread function of the imaging device when light exiting the light guiding fibre is captured by the imaging device.

[0177] Obviously, numerous modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced otherwise than as specifically described herein.

[0178] In so far as embodiments of the disclosure have been described as being implemented, at least in part, by software-controlled data processing apparatus, it will be appreciated that a non-transitory machine- readable medium carrying such software, such as an optical disk, a magnetic disk, semiconductor memory or the like, is also considered to represent an embodiment of the present disclosure.

[0179] It will be appreciated that the above description for clarity has described embodiments with reference to different functional units, circuitry and / or processors. However, it will be apparent that any suitable distribution of functionality between different functional units, circuitry and / or processors may be used without detracting from the embodiments.

[0180] Described embodiments may be implemented in any suitable form including hardware, software, firmware or any combination of these. Described embodiments may optionally be implemented at least partly as computer software running on one or more data processors and / or digital signal processors. The elements and components of any embodiment may be physical ly, functionally and logically implemented in any suitable way. Indeed the functionality may be implemented in a single unit, in a plurality of units or as part of other functional units. As such, the disclosed embodiments may be implemented in a single unit or may be physically and functionally distributed between different units, circuitry and / or processors.

[0181] Although the present disclosure has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may be combined in any manner suitable to implement the technique.

Claims

CLAIMS1. A system for measuring a point spread function of an imaging device, the system comprising: a light source configured to emit light, a filter configured to filter light emitted by the light source to a predetermined wavelength range, a light guiding fibre configured to guide light emitted by the light source and filtered by the filter along a path defined by the light guiding fibre, wherein light enters the light guide fibre through a first end of the light guide fibre and exits the light guide fibre through a second end of the light guide fibre; an adjustment unit configured to adjust a position of the second end of the light guiding fibre within a field of view of the imaging device; and circuitry, wherein the circuitry is configured to measure the point spread function of the imaging device when light exiting the light guiding fibre is captured by the imaging device.

2. The system according to claim 1, further comprising a first optical element configured to couple light emitted by the light source and filtered by the filter with the first end of the light guiding fibre.

3. The system according to claim 2, wherein the first optical element is a fibre coupler.

4. The system according to any of claims 1 to 3, wherein the filter is an exchangeable filter.

5. The system according to any of claims 1 to 3, wherein the filter comprises a filter wheel, wherein the filter wheel is configured to be rotatable to change the predetermined wavelength range.

6. The system according to any preceding claim, wherein the predetermined wavelength range is a narrow band wavelength range.

7. The system according to any preceding claim, wherein the light source is a broadband light source configured to emit collimated light in a broadband wavelength range.

8. The system according to any preceding claim, wherein the adjustment unit is configured to adjust a position of the light guiding fibre under control of the circuitry.

9. The system according to any preceding claim, wherein the system comprises a plurality of the light guiding fibres, and wherein the adjustment unit is configured to independently adjust a position of each of the plurality of light guiding fibres within a field of view of the imaging device.

10. The system according to claim 9, wherein independently adjusting the position of each of the plurality of light guiding fibres comprises setting different fibres of the plurality of light guiding fibres at different distances from the imaging device.

11. The system according to any preceding claim, further comprising the imaging device.

12. The system according to claim 11, wherein the imaging device comprises an imaging sensor and a second optical element.

13. The system according to claim 12, wherein a diameter of the light guiding fibre is configured to be smaller than a size of a pixel in the imaging sensor of the imaging device projected into object space and / or the size of the pixel is configured to be smaller than a diameter of the light guiding fibre projected into image space.

14. The system according to any of claims 11 to 13, wherein the adjustment unit is further configured to adjust at least one of: a viewing direction of the imaging device, a focus of the imaging device and / or a distance between the second end of the light guiding fibre and the imaging unit.

15. A method of measuring a point spread function of an imaging device, the method comprising: emitting light from a light source; filtering the light emitted by the light source to a predetermined wavelength range with a filter; guiding light emitted by the light source and filtered by the filter along a path defined by the light guiding fibre, wherein the light enters the light guide fibre through a first end of the light guide fibre and exits the light guide fibre through a second end of the light guide fibre; adjusting a position of the second end of the light guiding fibre within a field of view of the imaging device; and measuring the point spread function of the imaging device when light exiting the light guiding fibre is captured by the imaging device.

16. A computer program comprising instructions which, when implemented by a computer, cause the computer to perform a method of measuring a point spread function of an imaging device, the method comprising: controlling a light source to emit light; controlling a filter to filter the light emitted by the light source to a predetermined wavelength range; controlling a light guide fibre to guide light emitted by the light source and filtered by the filter along a path defined by the light guiding fibre, wherein the light enters the light guide fibre through a first end of the light guide fibre and exits the light guide fibre through a second end of the light guide fibre; controlling an adjustment unit to adjust a position of the second end of the light guiding fibre within a field of view of the imaging device; and controlling measurement of the point spread function of the imaging device when light exiting the light guiding fibre is captured by the imaging device.

Images