GB2607603A

GB2607603A - Imaging apparatus

Info

Publication number: GB2607603A
Application number: GB2108145.0A
Authority: GB
Inventors: Frederick Bullard Edward
Original assignee: Spectrum Logic Ltd
Current assignee: Spectrum Logic Ltd
Priority date: 2021-06-08
Filing date: 2021-06-08
Publication date: 2022-12-14
Also published as: GB202108145D0; WO2022258959A1

Abstract

An imaging apparatus 10 comprises: an optical source 22 configured to emit radiation in a first wavelength range; a fibre optic faceplate (FOF) 30 and an image sensor 40. The FOF 30 comprises an array of optical fibres. The FOF 30 comprises a first side 30A onto which a sample carrier 26 can be placed and a second side facing image sensor 40. The array of optical fibres is configured to convey radiation from the first side 30A to the second side. The radiation in the first wavelength range is configured to stimulate a sample on the sample carrier 26 to emit fluorescent radiation in a second wavelength range. The optical fibres in the FOF and/or a layer of image sensor 40, is configured to attenuate radiation in the first wavelength range. Another aspect is a method where the sample carrier 26 is positioned on the first side 30A of the FOF, the sample is stimulated with radiation from an optical source 22 at a first wavelength range to cause fluorescence in the sample, and the radiation is conveyed through the FOF and detected by the image sensor 40.

Description

IMAGING APPARATUS

BACKGROUND

Western blotting, or protein immunoblot; is a widely used analytical technique in molecular biology. The technique is used to detect proteins in a sample, such as a sample of tissue. A protein mixture is separated by electrophoresis. The separated proteins are transferred to a sample carrier (e.g. a membrane) by a process called blotting. The proteins on this carrier are then detected. A similar blotting process can be applied to analyse samples containing Deoxyribonucleic acid (DNA) or Ribonucleic acid (RNA).

In a chemiluminescence analysis technique, a reagent is applied to the carrier to cause proteins (or DNA/RNA) on the carrier to emit radiation. The emitted radiation is detected by photographic film, or by an image sensor.

In a fluorescence analysis technique, a carrier is exposed to stimulating radiation from a radiation source. This causes proteins (or DNA/RNA) on the carrier to emit radiation. The emitted radiation is detected by photographic film, or by an image sensor.

An imaging apparatus can use an image sensor which is smaller than a carrier, and a lens positioned between the image sensor and the carrier. An alternative type of imaging apparatus uses a large area image sensor which is the same size as the carrier under analysis. Using a large area image sensor has an advantage of improving imaging sensitivity. A paper "Using a large area CMOS APS for direct chemiluminescence detection in Western Blotting Eletrophoresis", by Michela Esposito et al, Medical Imaging 3012: Biomedical Applications in Molecular, Structural, and Functional Imaging, Proc. of SPIE Vol. 8317, describes an imaging apparatus with a wafer scale Active Pixel Sensor (APS) array for chemiluminescence detection.

In a fluorescence analysis technique; a filter is provided before the image sensor to block the stimulating radiation from reaching the image sensor. US 2017/0026829 Al describes a contact imaging device for fluorescence applications with an optical filtering layer mechanically coupled to a fixed fibre faceplate.

It is an aim of the present invention to address at least one disadvantage associated with the

prior art.

SUMMARY OF THE INVENTION

There is provided an imaging apparatus comprising: an optical source configured to emit radiation in a first wavelength range; an image sensor; a fibre optic faceplate comprising an array of optical fibres, the fibre optic faceplate comprising a first side onto which a sample carrier can be placed and a second side facing the image sensor, the array of optical fibres configured to convey radiation from the first side to the second side; wherein the radiation in the first wavelength range is configured to stimulate a sample on the sample carrier to emit fluorescent radiation in a second wavelength range, and wherein at least one of: the optical fibres in the fibre optical faceplate; and a layer of the image sensor is configured to attenuate radiation in the first wavelength range.

Optionally, the fibre optic faceplate is bonded by adhesive to a radiation-receiving face of the image sensor without an intermediate optical filtering device between the fibre optic faceplate and the image sensor.

Optionally, the first side of the fibre optic faceplate comprises exposed end faces of the optical fibres.

Optionally, the first side of the fibre optic faceplate comprises a protective layer over end faces of the optical fibres.

Optionally, the first wavelength range lies within, or partially within, an ultraviolet B (UV-B) radiation band.

Optionally, the first wavelength range is ultraviolet radiation having a wavelength of less than 330 nm.

Optionally, the second wavelength range lies within, or partially within, an ultraviolet A (UV-A) radiation band.

Optionally, the second wavelength range is radiation within, or partially within, a visible radiation band.

Optionally, at least one of: the optical fibres in the fibre optical faceplate; and a layer of the image sensor is configured to transmit <10% of received radiation at wavelengths below 330 nm, or <5% of received radiation at wavelengths below 330 nm, or <1% of received radiation at wavelengths below 330 nm.

Optionally, the optical fibres in the fibre optic faceplate comprise a core and a cladding, wherein the core is glass or fused silica material and the cladding is a different glass or fused silica material.

Optionally, the optical fibres in the fibre optic faceplate have a diameter of between 3 pm and 20 pm.

Optionally, the layer of the image sensor comprises a layer of silicon dioxide (SiO2) on a radiation-receiving side of the image sensor.

Optionally, the imaging apparatus is configured to: operate in a chemiluminescence analysis mode in which the radiation source is not activated; and operate in a fluorescence analysis mode in which the radiation source is activated.

Optionally, the imaging apparatus is configured to operate in a chemiluminescence analysis mode and then to operate in a fluorescence analysis mode during a single analysis operation.

There is also provided a method of imaging a sample comprising: positioning a sample carrier on a first side of a fibre optic faceplate; emitting radiation from an optical source in a first wavelength range to stimulate a sample to emit fluorescent radiation in a second wavelength range; conveying radiation from the first side of the fibre optic faceplate to a second side of the fibre optic faceplate; detecting radiation at an image sensor, wherein at least one of: the optical fibres in the fibre optical faceplate; and a layer of the image sensor is configured to attenuate radiation in the first wavelength range.

An advantage of at least one example or embodiment is a reduced number of optical components in the optical path between the sample under test on the carrier and the image sensor. This can improve detection efficiency. For example, reducing the number of optical interfaces in the optical path between the carrier and the image sensor can improve detection efficiency due to factors such as reduced reflection, scatter and attenuation.

Other advantages include reduced component count, improved assembly yield, and reduced cost.

Embodiments of the invention may be understood with reference to the appended claims.

Within the scope of this application it is envisaged that the various aspects, embodiments, examples and alternatives, and in particular the individual features thereof, set out in the preceding paragraphs, in the claims and/or in the following description and drawings, may be taken independently or in any combination. For example features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.

For the avoidance of doubt, it is to be understood that features described with respect to one aspect of the invention may be included within any other aspect of the invention, alone or in appropriate combination with one or more other features.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying figures in which: FIGURE 1 shows an imaging apparatus; FIGURE 2 shows a cross-section of part of the imaging apparatus of FIGURE 1; FIGURES shows spectral properties of the imaging apparatus of FIGURE 1 and FIGURE 2; FIGURE 4 shows part of a fibre optic faceplate; FIGURE 5 shows a cross-section of an image sensor; FIGURE 6 shows example images acquired by the imaging apparatus; FIGURE 7 shows an example image acquired by the imaging apparatus; FIGURE 8 shows an example of a processing apparatus which may be used to control the imaging apparatus; FIGURE 9 shows the main steps of chemiluminescence analysis and fluorescence analysis.

DETAILED DESCRIPTION

FIGURE 1 and FIGURE 2 show an apparatus 10 for imaging a sample carrier 26. The sample carrier 26 can be in the form of a membrane, such as a membrane of nitrocellulose, nylon or polyvinylidene difluoride (PVDF), which carries a pattern of proteins and/or nucleic acids which have been acquired from a sample of material.

The apparatus 10 comprises a housing with a lid 12 and a base 14. A radiation source 22 is provided as part of the lid 12. An image sensor 40 is provided as part of the base 14. The lid 12 has a hinged connection 16 to the base 14. Wien the lid 12 is closed against the base 14, the lid 12 and base 14 co-operate to form a light-tight enclosure. That is, the interior of the housing is shielded from external radiation. The base 14 has a faceplate 30 for receiving a sample carrier 26. The base 14 also houses a controller for controlling operation of the apparatus 10. The base 14 has indicators 18 to indicate an operating state of the apparatus, and ports (not shown) for connecting to a host computer.

In use, the lid 12 is opened, a sample carrier 26 is placed upon the faceplate 30 and the lid 12 is closed. During an analysis operation, the apparatus is configured to activate the radiation source 22 to emit stimulating, or excitation, radiation. The stimulating radiation causes proteins or nucleic acids on the sample carrier 26 to emit radiation by a process of fluorescence or phosphorescence.

The emission of light through a fluorescence process is nearly simultaneous with the absorption of the excitation radiation due to a short time between photon absorption and emission, a delay that is usually less than a microsecond. Electrons gain energy when a UV photon is absorbed and this vibrational energy is lost when the electron returns to the ground state from the excited state. The photon emitted by an excited fluorophore is normally shifted to longer wavelengths when compared to the stimulating photon it absorbed. This is Stokes' Law. Emission that persists longer than this after the stimulation irradiation has ceased is referred to as phosphorescence.

The apparatus is configured to cause the image sensor 40 to detect radiation emitted by the sample carrier 26. The image sensor 40 can acquire an image which is a two-dimensional array of patches. Each patch represents a protein of a particular type and/or having particular properties. Examples of images acquired by the image sensor 40 are shown in FIGURES 6 and 7.

FIGURE 2 shows a cross-section through part of the apparatus 10. A sample carrier 26 has been placed on the faceplate 30 for imaging. Radiation source 22 is provided as part of the lid 12. The radiation source 22 emits radiation 24 towards a first (top) side of the sample carrier 26. An image sensor 40 detects radiation emitted by the sample carrier 26. The image sensor 40 is a large area device having an area which is substantially equal to an area of the faceplate 30. The image sensor 40 has a radiation-receiving face 40A. The faceplate 30 is a fibre optic faceplate (FOF), or a fibre optic plate (FOP). The FOF is parallel to, and adjacent to, the radiation-receiving face 40A of the image sensor 40. The FOF 30 may be bonded by adhesive 42 to the radiation-receiving face 40A of the image sensor 40 without an intermediate optical device (e.g. filter) between the FOF 30 and the image sensor 40. The adhesive 42 is a type of adhesive which allows radiation to pass through with minimal attenuation. A suitable adhesive is an optical adhesive or optical epoxy. These are liquid adhesives which can be applied in liquid form during an assembly process. Another suitable adhesive is a sheet or film of Optically Clear Adhesive (OCA).

The image sensor 40 can comprise a Complementary Metal Oxide Semiconductor (CMOS) active-pixel sensor (APS) image sensor, a Charge Coupled Device (CCD) image sensor or an image sensor which uses some other technology. The image sensor 40 comprises an array of pixels which can be exposed to radiation. At the end of an exposure period a value, representing an amount of radiation incident on the pixel during the exposure period, is read from each of the pixels of the image sensor 40.

The FOF 30 comprises an array of fibre optic light guides. The fibre optic light guides are oriented orthogonally to the radiation-receiving face 40A of the image sensor 40. The FOF 30 has a first (upstream) face 30A and a second (downstream) face. In use, radiation received at the first face 30A is guided by the individual fibre optic light guides to the second face and emitted towards the image sensor 40. The FOF preserves spatial resolution and minimises, or avoids, blurring of an acquired image. This imaging arrangement can also be described as a contact imaging or 1:1 imaging.

In FIGURE 1, the sample carrier 26 is placed directly onto the first (upstream) face 30A of the FOF 30. There is not an intermediate optical filtering device between the sample carrier 26 and the FOF 30. The first (upstream) end faces of the optical fibre light guides may be fully exposed, or may be covered by a protective layer.

The FOF 30 and the image sensor 40 together form one monolithic unit. This can improve detection efficiency, as there are fewer optical interfaces in the overall optical path between the sample carrier 26 and the image sensor 40. Each optical interface can introduce one or more of: attenuation; reflection; and scattering which can reduce the amount and/or quality of radiation reaching the image sensor 40.

The image sensor 40 can be bonded by adhesive 44 to a substrate 46. An example of a suitable substrate is an aluminium substrate. It is also possible to mount the image sensor 40 on a printed circuit board (PCB). The substrate or PCB can be mounted to the base 14.

FIGURE 3 shows part of the apparatus of FIGURE 1 and explains spectral properties of the stimulating and emitted radiation, and spectral properties of the filter. The right-hand side of FIGURE 3 shows a set of graphs illustrating spectral properties, with wavelength increasing to the right-hand side. The electromagnetic spectrum comprises, in order of increasing wavelength: Ultraviolet C (UV-C) radiation; Ultraviolet B (UV-B) radiation; Ultraviolet A (UV-A) radiation; and visible radiation. Radiation source 22 emits radiation 24 in a first wavelength range. Sample carrier 26 is stimulated by the radiation 24. This causes proteins (or nucleic acids) on the sample carrier 26 to emit radiation in a second wavelength range. The second wavelength range is spaced from the first wavelength range. The first wavelength range may lie within, or partly within, the UV-B radiation band (280-315 nm.) The second wavelength range may lie within, or partly within, the UV-A radiation band (315400 nm.) The second wavelength range may lie within, or partly within, the visible band (e.g. wavelengths between 380 nm and 740 nm.) Optionally, the second wavelength range may comprise near-infrared (NIR) wavelengths, e.g. wavelengths above 740 nm. The second wavelength range may lie within, or partly within, the range of wavelengths from around 700nm or 740nm to around 900nm. The second wavelength range may lie within, or partly within, the range of wavelengths from around 700nm or 740nm to around 1000nm. The second wavelength range my lie within, or partly within, the range of wavelengths from around 700nm to around 1100nm, optionally within or partly within the range of wavelengths from around 740nm to around 1100nm, optionally within or partly within the range of wavelengths from around 740nm to around 1110nm.

In one example, the FOF 30 behaves as a filter. The FOF 30 attenuates shorter wavelengths (e.g. in the UV-B band) and passes longer wavelengths (e.g. in the UV-A and visible bands). It will be understood that the graphs shown in FIGURE 3 are schematic, and that the shapes of the emitted radiation and filter properties can differ. The FOF 30 attenuates wavelengths in the first wavelength range of the source 22. This reduces, or prevents, radiation from the source 22 reaching the image sensor 40. The FOF 30 passes wavelengths in the second wavelength range of the sample. This allows wavelengths in the second wavelength range to reach the image sensor 40.

An example set of transmission properties for each of three different FOFs (FOF #1, FOF #2, FOF #3) is shown below: Transmission nm FOF #1 FOF #2 FOF #3 400 74% 89% 95% 390 71% 84% 92% 380 67% 76% 90% 370 60% 64% 87% 360 50% 42% 80% 350 36% 14% 55% 340 18% - 35% 330 7% -For each of the FOFs, the amount of transmitted radiation increases with increasing wavelength. Each of these FOFs has a different transmission response.

Advantageously, the filter largely transmits visible light, such as >50% transmission at wavelengths >380 nm, and largely blocks UV radiation, such as <10% transmission at wavelengths >200 nm and <330 nm. The filter can have a high-pass filter response. The optimal excitation wavelengths for fluorescence imaging lie in the wavelength range of about 220 nm to about 300 nm. This causes peak fluorescence in a wavelength range of about 320 nm to about 450 nm.

FIGURE 4 shows part of the FOF 30 in plan view, i.e. looking down onto face 30A in FIGURE 2. The FOF 30 comprises an array of fibre optic light guides 32. Each light guide 32 has a core 34 and cladding 36. The core 34 has a core diameter 34D. The cladding 36 has a thickness 36T. The overall diameter of one of the light guides 32 can be, for example, 6 pm or, more generally, in the range of about 3 pm to about 20 pm, or in the range of from about 3 pm to about 30 pm. The individual fibres 32 can have a core of glass material with a different glass cladding material. The glass material can be fused silica (silicon dioxide, Si02). Other materials are possible, such as polymer materials.

A diameter or pitch (i.e. distance between corresponding features in adjacent elements) is much smaller than a diameter or pitch of pixels of the image sensor 40. For example, the light guides 32 in FOF 30 can have a pitch of 6 pm and pixels of the image sensor 40 can have a pitch of 100 pm.

In the apparatus of FIGURE 1 and FIGURE 2, radiation emitted by proteins or nucleic acids on the sample carrier 26 pass directly into the FOF 30. The FOF 30 attenuates the first wavelength range of the radiation 24 emitted by the source 22.

The apparatus can detect emitted radiation at near-infrared (NIR) wavelengths, e.g. wavelengths above 740 nm. A CMOS image sensor response cuts off at wavelengths of 1110 nm as the optical bandgap of silicon is about 1110 nm. A CMOS image sensor has a low response above 900 nm. For practical purposes, a cmos image sensor can provide a useable response to received radiation over wavelengths from 740nm to 900nrn.

FIGURE 5 shows an image sensor 140. The image sensor 140 comprises a layer 142 of Si02. The layer 142 provides a filtering effect on radiation of the first wavelength range. The layer 142 attenuates shorter wavelengths (e.g. in the UV-B band) and passes longer wavelengths (e.g. in the UV-A and visible bands). The image sensor 140 can be used in place of the image sensor 40 in FIGURES 1 and FIGURE 2. The FOF 30 and the image sensor 140 can have a similar filtering response on radiation, or different filtering responses. FIGURE 5 shows the layer 142 as the outermost (radiation-receiving) layer of the image sensor, but there may be other layers above layer 142.

FIGURE 6 shows some examples of images acquired by the apparatus for four samples: Sample 1-4. In the acquired images, useful information is conveyed by: location, intensity and sharpness of each of the patches.

FIGURE 7 shows an example of an image acquired by the apparatus and a graph of gray value (intensity) against distance along a line A-B.

The imaging apparatus can be used for chemiluminescence analysis of a sample and for fluorescence analysis of a sample. The imaging apparatus is configured to: operate in a chemiluminescence analysis mode in which the radiation source is not activated; and operate in a fluorescence analysis mode in which the radiation source is activated.

It is also possible to begin operating in a chemiluminescence analysis mode and then to activate the radiation source and operate in a fluorescence analysis mode. For example, the radiation source can be activated once the chemiluminescence level has fallen to an insignificant level, i.a a level that would not compromise the fluorescence imaging.

FIGURE 8 shows an example of a processing apparatus 150 which may be used to control the imaging apparatus 10. Processing apparatus 150 comprises one or more processor 151 which may be any type of processor for executing instructions to control the operation of the apparatus 10. The processor 151 is connected to other components of the apparatus via one or more buses 152. Processor-executable instructions 154 may be provided using any data storage device or computer-readable media, such as memory 153. The processor-executable instructions 154 comprise instructions for implementing the functionality of the described methods. The memory 153 is of any suitable type such as non-volatile memory, a magnetic or optical storage device. Memory 153 stores data used by the processor.

The processing apparatus 150 is connected to the radiation source(s) 22 and the image sensor 40. The processing apparatus 150 controls when the radiations source 22 is turned on and off. The processing apparatus 150 controls the image sensor 40. For example, the processing apparatus 150 controls an exposure period of the image sensor 40 and controls transfer of image data from the image sensor 40 to memory 153, and transfer of image data from the memory 153 to an external computer.

The processing apparatus 150 comprises an I/O interface 157 (e.g. Universal Serial Bus (USB)). The I/O interface 157 allows the processing apparatus 150 to communicate with a host device, such as a computer. The I/O interface 157 can be used to transfer image data to the host device. The I/O interface 157 can be used to control settings of the imaging apparatus 10, such as an exposure period. The I/O interface 157 can also include a video output interface, such as a High-Definition Multimedia Interface (HDMI).

The processing apparatus 150 comprises a user interface 158. This can include visible indicators 18 (FIGURE 1) and may include one or more of: a display for displaying information about operation of the apparatus buttons for user input; a touchscreen for displaying information and receiving user input.

FIGURE 9 shows the main steps of chemiluminescence analysis and fluorescence analysis. Chemiluminescence analysis begins by processing a sample by electrophoresis 202. A sample of material is analysed by passing an electrical current across a gel containing the sample of material. After a period of time, proteins or nucleic acids have separated into a 1D or 2D pattern. The pattern is transferred to a sample carrier, such as a membrane of nitrocellulose, nylon or PVDF. At block 204, a reagent is added to the membrane. An exampie of a suitable reagent is an Enhanced Cherniluminescence (ECL) reagent based on light emission at 425 111T1 from Lumina! (3-amino-phthallhydrazide) catalysed by Horse Radish Peroxidase (HPR). The HRP is typically attached to an antibody that binds to the target protein. The reagent causes proteins or nucleic acids on the membrane to emit radiation by chemiluminescence. At block 206, the radiation is detected. The sample carrier is inserted into the apparatus 10 to detect emitted radiation over a detection period. The sample carrier is not stimulated by radiation from the radiation source The detection period may, for example, be of the order of seconds or minutes.

Fluorescence analysis begins by processing a sample by electrophoresis 212, which is the same, or similar, to block 202. A sample of material is analysed by passing an electrical current across a gel containing the sample of material. After a period of time, proteins or nucleic acids have separated into a 10 or 20 pattern. The pattern is transferred to a sample carrier, such as a membrane of nitrocellulose, nylon or PVDF. At block 216, the sample carrier is inserted into the apparatus 10. The sample carrier is stimulated by radiation from the radiation source 22. Radiation emitted by the sample carrier is detected over a detection period. The detection period may, for example, be of the order of seconds.

Fluorescence imaging can be performed using fluorochromes to stain tissue, bacteria, proteins and other materials. Some materials exhibit natural autofluorescence under UV radiation, e.g. DNA and RNA. A dye can be used for DNA and RNA fluorescence detection in gel electrophoresis. Ethidium bromide is the most common dye. Ethidium bromide is a DNA intercalator, inserting itself between the base pairs in the double helix. Ethidium bromide has UV absorbance maxima at about 300 nm, and an emission maximum at 590 nm (orange).

The image sensor 40 can respond to a wide range of wavelengths of radiation received from the FOP 30, such as all wavelengths within the pass-band of the FOP 30. The image sensor 40 will respond to intensity of received radiation, but will not distinguish between wavelengths of received radiation. In another imaging apparatus, the image sensor 40 can be provided with a colour filter array, such as a Bayer colour filter array. A colour filter array comprises an array of filter elements in front of the pixels of the image sensor. Each filter passes a limited range of wavelengths. For example, the colour filter array can comprise red, green and blue filter elements. A first sub-set of pixels have a red filter in front of them, a second sub-set of pixels have a green filter in front of them, and a third sub-set of pixels have a blue filter in front of them.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", means "including but not limited to", and is not intended to (and does not) exclude other moieties, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

Claims

CLAIMS: 1. An imaging apparatus comprising: an optical source configured to emit radiation in a first wavelength range; an image sensor; a fibre optic faceplate comprising an array of optical fibres, the fibre optic faceplate comprising a first side onto which a sample carrier can be placed and a second side facing the image sensor, the array of optical fibres configured to convey radiation from the first side to the second side; wherein the radiation in the first wavelength range is configured to stimulate a sample on the sample carrier to emit fluorescent radiation in a second wavelength range, and wherein at least one of: the optical fibres in the fibre optical faceplate; and a layer of the image sensor is configured to attenuate radiation in the first wavelength range.
2. An imaging apparatus according to claim 1 wherein the fibre optic faceplate is bonded by adhesive to a radiation-receiving face of the image sensor without an intermediate optical filtering device between the fibre optic faceplate and the image sensor.
3. An imaging apparatus according to claim 1 or 2 wherein the first side of the fibre optic faceplate comprises exposed end faces of the optical fibres.
4. An imaging apparatus according to claim 1 or 2 wherein the first side of the fibre optic faceplate comprises a protective layer over end faces of the optical fibres.
5. An imaging apparatus according to any one of the preceding claims wherein the first wavelength range lies within, or partially within, an ultraviolet B (UV-B) radiation band.
6. An imaging apparatus according to any one of the preceding claims wherein the first wavelength range is ultraviolet radiation having a wavelength of less than 330 nm.
7. An imaging apparatus according to any one of the preceding claims wherein the second wavelength range lies within, or partially within, an ultraviolet A (UV-A) radiation 35 band.
8. An imaging apparatus according to any one of the preceding claims wherein the second wavelength range is radiation within, or partially within, a visible radiation band.
9. An imaging apparatus according to any one of the preceding claims wherein at least one of: the optical fibres in the fibre optical faceplate; and a layer of the image sensor is configured to transmit <10% of received radiation at wavelengths below 330 nm.
10. An imaging apparatus according to any one of the preceding claims wherein at least one of: the optical fibres in the fibre optical faceplate; and a layer of the image sensor is configured to transmit <5% of received radiation at wavelengths below 330 nm.
11. An imaging apparatus according to any one of the preceding claims wherein at least one of: the optical fibres in the fibre optical faceplate; and a layer of the image sensor is configured to transmit <1% of received radiation at wavelengths below 330 nm.
12. An imaging apparatus according to any one of the preceding claims wherein the optical fibres in the fibre optic faceplate comprise a core and a cladding, wherein the core is glass or fused silica material and the cladding is a different glass or fused silica material.
13. An imaging apparatus according to any one of the preceding claims wherein the optical fibres in the fibre optic faceplate have a diameter of from 3 pm to 30 pm.
14. An imaging apparatus according to any one of the preceding claims wherein the layer of the image sensor comprises a layer of silicon dioxide (Si02) on a radiation-receiving side of the image sensor.
15. An imaging apparatus according to any one of the preceding claims which is configured to: operate in a chemiluminescence analysis mode in which the radiation source is not activated; and operate in a fluorescence analysis mode in which the radiation source is activated.
16. An imaging apparatus according to claim 15 which is configured to operate in a chemiluminescence analysis mode and then to operate in a fluorescence analysis mode during a single analysis operation.
17. A method of imaging a sample comprising: positioning a sample carrier on a first side of a fibre optic faceplate; emitting radiation from an optical source in a first wavelength range to stimulate a sample to emit fluorescent radiation in a second wavelength range; conveying radiation from the first side of the fibre optic faceplate to a second side of the fibre optic faceplate; detecting radiation at an image sensor, wherein at least one of: the optical fibres in the fibre optical faceplate; and a layer of the image sensor is configured to attenuate radiation in the first wavelength range.