WO2024261011A1

WO2024261011A1 - Optical coherence tomography apparatus

Info

Publication number: WO2024261011A1
Application number: PCT/EP2024/067015
Authority: WO
Inventors: Peter Skovgaard; Thomas Buss
Original assignee: Norlase Aps
Current assignee: Norlase Aps
Priority date: 2023-06-20
Filing date: 2024-06-19
Publication date: 2024-12-26
Anticipated expiration: 2025-12-20

Abstract

One aspect of the present disclosure relates to an optical coherence tomography apparatus, in particular a swept-source optical coherence tomography apparatus, for imaging a patient's eye, the apparatus comprising a light source configured to generate a beam of light, the beam of light distributed over a 2-dimensional area on the retina of the patient, a camera comprising a 2-D sensor wherein the apparatus is configured to bundle a plurality of pixels on the sensor, such that each data point comprises the combined response from a plurality of bundled pixels.

Description

OPTICAL COHERENCE TOMOGRAPHY APPARATUS

Technical Field

The present disclosure relates to an optical coherence tomography apparatus, in particular a swept-source optical coherence tomography apparatus, for imaging a patient’s eye.

Background

Optical Coherence Tomography is a technology used in clinical practice within Ophthalmology for non-invasive imaging of the human eye. The traditional method for eye examination is using a slit lamp or ophthalmoscope to view the fundus of the eye. These methods only show the surface, and in many cases it is necessary or advantageous to view the morphology, which is possible using ultrasound or Optical Coherence Tomography (OCT). OCT provides detailed, cross-sectional images of the various layers of the eye, allowing ophthalmologists to diagnose and monitor a wide range of eye conditions and diseases. OCT is most widely adopted using an Optical Coherence Tomographer, which is mainly based on the Spectral Domain Optical Coherence Tomography method, using commercially available Superluminescent Diodes (SLDs) and grating spectrometers. However, many other methods have been researched and commercialized, of which Swept Source Optical Coherence Tomography (SS-OCT), having advantages of faster imaging speed and longer range, is available for OCT biometry and diagnostics.

Commercial Optical Coherence Tomographers mainly use the point scanning method to achieve 2D to 3D images by using a scanning mechanism of the optical beam, such as galvanometer mirrors, to raster scan the focused beam across the fundus or other parts of the eye such as the cornea. OCT is also used in other fields of application, for example dermatology and industrial inspection. In OCT scanning, an A-scan is a one-dimensional depth profile obtained from the light backscattered from the tissue as a function of depth. It provides information about the reflectivity or backscattering intensity of the tissue as a function of depth at a specific location. A-scan data is often used to assess the thickness or dimensions of specific structures within the tissue.

A B-scan is a two-dimensional cross-sectional image generated by combining multiple A-scans. It is a series of A-scans acquired along a line or a scanning pattern. B-scans provide a two-dimensional representation of the tissue structures, showing the internal morphology and organization of different tissue layers. This type of scan is commonly used in ophthalmology to visualize the layers of the retina or the cornea.

A C-scan is a three-dimensional representation of the imaged tissue volume. It is constructed by acquiring multiple B-scans at different locations and then combining them to form a complete 3-D image. C-scans provide a comprehensive view of the tissue in three dimensions and are particularly useful for visualizing complex structures and assessing spatial relationships between different tissue layers. C-scans are commonly used for ophthalmic imaging, such as mapping the topography of the cornea or generating 3D reconstructions of the retina.

LF-OCT can be based on time-domain OCT (TD-OCT), spectral-domain OCT (SD-OCT) or swept-source OCT (SS-OCT). In Line-Field OCT, a B- scan is recorded and a C-scan is achieved by scanning the illuminated line, and further using one of the TD-, SD- or SS-OCT methods.

In Full-field OCT, in contrast, the en-face OCT scan is acquired immediately with a 2D camera, while the A-scan is acquired by the SD- or SS-OCT method.

En-face OCT provides a two-dimensional (2D) image of a specific depth plane within the tissue being imaged. Unlike traditional OCT techniques that produce cross-sectional B-scans, en-face OCT captures a single plane perpendicular to the beam path, resulting in a "top-down" view of the tissue.

The en-face OCT technique may utilize a full-field illumination of the entire sample with a wide-field light source consisting of a broad band of wavelengths. The light is split into two paths: a reference path and a sample path. The reference path includes a reference mirror, while the sample path interacts with the tissue. Interference between the reference and sample light waves is used to extract the depth information from the tissue. En-face views may also be reconstructed from 3D data.

There are several drawbacks of the currently available OCT systems. For example, fast swept-sources are expensive and complex, and they are often combined with a fast 2-D mirror scanner, resulting in expensive and complex OCT systems. OCT systems based on spectral-domain sources needs gratings or spectrometers for resolving the wavelength, which often results in chromatic cross-talk and thereby poor spatial resolution.

In general, OCT systems on the market are often very expensive, standalone systems that take up a lot of space in the clinic.

Summary

In view of the above, it remains desirable to provide a device for OCT scanning, in particular in ophthalmology, that mitigates one or more of the disadvantages of prior art systems or that at least can serve as an alternative.

According to a first aspect, disclosed herein is and optical coherence tomography apparatus, in particular a swept-source optical coherence tomography apparatus, for imaging a target tissue, in particular a patient’s eye, the apparatus comprising:

- a light source for emitting light, - an optical system configured to direct a sample portion of the emitted light as a sample beam of light onto a 2-dimensional area on the target tissue to be imaged, the optical system being further configured to direct a reference portion of the emitted light as a reference beam onto a reflector,

- a 2-D image sensor comprising an array of sensor pixels, wherein the optical system is further configured to receive a reflected portion of the sample beam, reflected by the target tissue, and a reflected portion of the reference beam, reflected by the reflector, and to direct the received reflected portions onto the image sensor to create an interferometric image of the 2-dimensional area of the target tissue;

- a signal processing circuit configured to process sensor signals from the image sensor to obtain one or more images, in particular depth-resolved images, of the target tissue;

- wherein the signal processing circuit is configured to bundle groups of sensor pixels into respective data points, such that each data point comprises a combined response from a plurality of bundled pixels and is indicative of interferometric image information of a portion of the target tissue.

By bundling a plurality of pixels into each data point, the signal to noise ratio is improved. In addition, the need for optical accuracy can be relaxed. For the purpose of the present description, bundling of pixels refers to the combining of responses from respective groups of adjacent pixels within the 2-D image sensor. The bundling of pixels may be performed by summing, averaging or otherwise combining the pixel values of the pixels that are being bundled. The bundling of pixels may be performed during or after readout of the image sensor. Bundling of pixels may also be referred to as binning of pixels. In some embodiments, the signal processing circuit may be configured to select a group of sub-areas within the light-receiving area of the image sensor and to selectively process pixels only from the selected sub-areas. In particular, the bundling of pixels may be performed for adjacent pixels within each of the selected sub-areas. The sub-areas may be nonoverlapping or overlapping. The sub-areas may be in the form of elongated strips, e.g. straight strips each defining an elongated rectangular sub-area, or curved strips, in particular annular strips. An annular strip may be defined as the area between two concentric circles. The selected sub-areas may define a regular pattern. Examples of regular patterns include a series of parallel, mutually spaced apart strips. Another example includes a grid formed by two or more sets of strips, where the strips of each set are mutually parallel with each other and spaced apart from each other, and where the strips of respective sets intersect each other and an angle, e.g. at 90°. Other examples of regular patterns include a set of concentric, annular strips that are sized such that the annular strips are radially spaced apart from each other by annular gaps. The strips may define a length along their direction of elongation and a width defined in a direction across the direction of elongation. For example, the strips may be 2, 3, 4, 5 or more pixels wide. In some embodiments, the bundling of pixels may be performed such that pixels are bundled along the width of the strips, e.g. by bundling all pixels along one line or along multiple adjacent lines of pixels, where the one or more lines extend along a direction across, in particular orthogonal to, the direction of elongation of the strip. However, other bundling schemes may be employed instead. The selected sub-areas together define an area or pattern of interest.

By defining an area or pattern of interest within the 2-D area of the image sensor, response from pixels outside the area of interest can be disregarded, saving data processing time. In some embodiments, the 2-D area is subdivided into a plurality of strips and the pixel bundling is selectively performed within each strip. In this way, the apparatus mimics the more expensive and slower line-field scanner, while enabling a faster read out speed from the sensor. Furthermore, compared to the line-field scanner, the apparatus of this disclosure does not utilize a galvanometer scanner, making it cheaper and less complex.

In various embodiments, the optical system is configured to image the illuminated 2-dimensional area of the target tissue onto the image sensor such that the image of the 2-dimensional area covers a plurality of pixels of the image sensor.

To this end, the 2-dimensional area on the target tissue may have a size of at least 1 mm², such as at least 4 mm², such as at least 10 mm², such as at least 20 mm², such as at least 25 mm², e.g. between 1 mm² and 100 mm², such as between 4 mm² and 75 mm². The illuminated 2-dimensional area may be rectangular, in particular square, round, in particular circular, or have another suitable geometric shape. The illuminated 2-dimensional area may have a linear extent along each of two mutually orthogonal directions of at least 1 mm, such as at least 2 mm, such as at least 4 mm, such as at least 5 mm, e.g. between 1 mm and 10 mm.

The optical system may be configured to illuminate the 2-dimensional area in a substantially uniform manner or in a non-uniform manner. In preferred embodiments, the optical system is configured to only, or predominantly, illuminate selected parts of the 2-dimensional area, in particular so as to project a pattern onto the target tissue, e.g. a pattern of one or more illuminated lines, or otherwise, where the pattern extends across the 2- dimensional area. The 2-dimensional area may thus be defined as the transverse extent of the illuminated pattern. Accordingly, the optical system may be configured to illuminate the 2-dimensional area with structured light. The optical system may be configured to illuminate the entire 2-dimensional area, or at least the projected pattern, concurrently, i.e. without scanning the sample beam across the 2-dimensional area in a direction transverse to the direction of the sample beam.

Accordingly, in some embodiments, the apparatus is configured to generate a pattern, which is projected onto the retina or other target tissue and, preferably, onto the reflector of the reference path. To this end, the optical system may include one or more suitable pattern generation optical elements, e.g. one or more diffractive optical elements, one or more digital light processors, one or more spatial light modulators, one or more lens arrays, etc. or a combination thereof. By illuminating only the area to be imaged onto the selected sub-areas with a pattern, cross-talk is reduced and the required laser power is significantly lower. Camera readout may thus be restricted to the subareas onto which the illuminated area(s) are imaged. Accordingly, in some embodiments, the signal processing circuit may be configured to select the group of sub-areas within the light-receiving area of the image sensor to correspond to the image of the illuminated pattern projected into the target tissue, in particular such that the selected sub-areas correspond to the illuminated portions of the 2-dimensional area on the target tissue.

In some embodiments, the one or more pattern generation optical elements are placed in the optical path in front of the beam splitter, thus providing a compact system.

In some embodiments, the pattern is generated using one or more diffractive optical element(s) (DOE). Using a DOE for pattern generation is a low cost solution, which is simple to insert in the collimated light beam. It is lightweight, and no extra electronics are needed when using a single, fixed pattern. Furthermore, nearly all input light is put into the output light, without absorption or scattering losses.

In some embodiments, one or more pattern generation optical elements are configured to be selectively inserted into the beam path or otherwise configured to be selectively activated. For example the one or more pattern generation optical elements may be mounted on a wheel or slide for selection on demand. In some embodiments, the one or more pattern generation optical elements may be configured to selectively create respective patterns. For example, different pattern generation optical elements may be mounted on a wheel or otherwise in a manner that allows a selected patter generation optical element to be inserted into the beam path. It is advantageous to allow the doctor to choose the pattern they wish to use, and to allow them to change the pattern they are using, as different doctors may have different preferences with regards to the pattern used.

In some embodiments, the pattern is generated using a digital light processor (DLP), which may use a digital micromirror device (DMD). The DMD is an array of individually addressable, highly reflective micromirrors. Compared to the prior art line-field OCT scanners using a galvo, which needs to scan continuously, the DLP pattern is static, and therefore there is no unwanted movement of the pattern during an OCT scan. Furthermore, using a DLP is more reliable, and uses less power than the galvo scanner.

In some embodiments, the pattern is generated using an array of lenses. For example a 1 -D array of cylindrical lenses may be used to generate a pattern of multiple lines.

In some embodiments, the pattern is generated using a spatial light modulator (SLM). Using a spatial light modulator has the advantage that it is electrically reconfigurable, so the pattern can by changed dynamically. In some embodiments, the pattern comprises a plurality of lines, a cross, a line-grid, a plurality of concentric rings, a plurality of lines intersecting in a common intersection point like spokes of a wheel, or any other line pattern, which is clinically relevant and suitable for efficient image read-out and bundling, e.g. using CCD or CMOS readout technologies. In particular, if using a CCD sensor, the dynamic range is large, and binning of pixels is possible. Readout from the CCD sensor is done on a line-by-line bases, since typically, a CCD sensor will have only one amplifier for all pixels. A CMOS sensor on the other hand, has a smaller dynamic range, but both binning and partial readout is possible. This is possible since the CMOS sensor has one amplifier per pixel. Furthermore, the selected pattern should preferably convey information to the user, such as defining a relevant cross section or relevant volume either readable by a human or possible by artificial intelligence such as a machine learning algorithm.

In some embodiments, the light source is a swept-source laser. Accordingly, the 2D image sensor may be configured to acquire multiple images during a wavelength sweep of the swept-source laser, thereby obtaining data points for respective wavelengths of the emitted sample beam. The signal processing unit may be configured to process 2D images obtained for respective wavelengths of the emitted sample beam to obtain 3D image information indicative of tissue properties at respective penetration depths. Preferably, the light source is a swept-source laser with a suitable scanning speed (e.g. a scanning speed of 10-100 Hz), and output power between 0.5-100 mW or higher, and output wavelengths within a wavelength band of 700 - 1300 nm. However, other types of swept-source lasers may be used. The desired output power and wavelength range may depend on the application.

For a given camera with a given data extraction speed, several factors may be considered when selecting the scanning speed of the swept-source laser. These factors may include the desired spatial resolution (i.e. the desired number of pixels) and/or the desired imaging depth in each A-scan which, in some embodiments is related to the number of spectral read-outs during a wavelength sweep of the swept-source (i.e. the number of pixel intensity read-out within each sweep period).

In some embodiments, the laser light wavelength produced by the light source is in the infrared spectrum between 700-1 OOOnm, for example around 750-950nm, preferably around 850 nm. This wavelength range is optimal in regards to attenuation/scattering, and compatible with silicon CCD or CMOS sensors being sensitive in this wavelength range.

In some embodiments, the apparatus comprises an attachment mechanism for attaching to a slit lamp. By attaching the OCT systems onto the slit lamp, several advantages can be obtained. The doctor will be able to look into the eye of patient while the scanning take place and thereby ensure that an OCT image is made of the most interesting area on the retina. Also, the focusing mechanism of the slit lamp can be utilized to ensure that the OCT system is placed at the optimum distance from the patient’s eye, such that the best OCT image is obtained. Finally, a slit lamp mounted OCT system will save space in the clinic, where space is highly valuable.

Brief description of the drawings

The above and other aspects will be apparent and elucidated from the embodiments described in the following with reference to the drawing in which:

FIG. 1 schematically illustrates a swept-source optical coherence tomography apparatus according to embodiments of this disclosure.

FIG. 2 schematically illustrates an image sensor according to embodiments of this disclosure. Detailed description

Fig. 1 schematically shows a swept-source optical coherence tomography apparatus 101 for imaging a patient’s eye according to an embodiment of this disclosure. The apparatus 101 comprises a light source 102, an optical system 120, an image sensor 106, and a signal processing circuit 130. The optical system 120 may comprises a beam splitter 105, a collimator 108 and, optionally, one or more pattern generation optical elements 103, such as a DOE, a DLP, a DMD, an SLM, a lens array and/or the like. The beam splitter 105 may be in the form of a non-polarizing beam splitter. The light source 102 may be a swept-source laser with a suitable sweep rate, e.g. a kHz sweep rate or a sweep rate of 10 to 100 Hz, and a suitable output power and wavelength range, e.g. an output power between 0.5-100 mW and output wavelengths within a wavelength band of 700 - 1300 nm.

The beam splitter 105 splits the light from the light source 102 into two paths: a reference path 109 and a sample path 110. The reference path includes a reference mirror 111 , while the sample path interacts with the target tissue to be imaged, in this example tissue of a subject's eye 107. Light returning from the tissue and from the mirror, respectively, are combined by the beam splitter 105 and directed towards the image sensor 106. The combination of reflected light from the sample path 110 and reference light from the reference path 109 results in an interference pattern on the image sensor which reflects tissue properties at one or more penetration depths at and/or beneath the tissue surface. Areas of the sample that reflect back a lot of light will create greater interference than areas with low reflectivity. Any light that is outside the coherence length of the light does not cause interference.

When employing time-domain OCT, scanning the reference mirror 111 in the reference path, provides interference images of the sample at respective penetration depths. When employing Frequency-Domain OCT (in particular SD-OCT or SS- OCT), spectral interferograms may be obtained by the pixels of the image sensor and then processed, in particular Fourier transformed, to obtain an axial scan of reflectance amplitude versus depth. In SS-OCT, the spectral interferograms may be acquired sequentially by sweeping the wavelength of the light source 102, which in such embodiments may be a swept-source laser as described above.

Accordingly, the apparatus allows the capturing of interferometric images of the target tissue at respective penetration depths.

The image sensor 106 may be a charged coupled device (CCD) or a complementary metal oxide semiconductor sensor (CMOS). The image sensor may be a regular 2-D camera. The apparatus 101 may further comprise one or more pattern generation optical elements 103, configured to generate a projected light pattern 104 with precisely defined dimensions. The light pattern may be in the form of a plurality of lines, a cross, a checkerboard pattern, or any other well-defined geometrical form.

The signal processing circuit 130 may be implemented as any suitable analogue and/or digital circuitry. It may be partly or completely be integrated with the image sensor or it may at least in part be provided as a separate signal processing unit. The signal processing circuit performs pixel bundling as described below and further signal processing, which may depend on the type of OCT employed. For example, the signal processing may include Fourier-transformation and/or other signal processing operations.

In some embodiments, the light source is configured to emit a collimated light beam, distributed over a 2-D area on the patient’s retina. The light beam may be collimated along one or both directions and/or configured to illuminate the target tissue to be imaged with structured light, e.g. by means of the pattern generation optical element(s) 103. As mentioned above, in some embodiments, the pattern generation optical element(s) 103 may include one or more diffractive optical elements. Alternatively, the apparatus may instead comprise another type of pattern generation optical element, e.g. a digital mirror device array, an array of lenses, in particular micro-lenses, or a spatial light modulator for generating the projected pattern. In other embodiments, the DOE or other means for generating a projected pattern may be omitted.

Fig. 2 is a schematic illustration of the image sensor, in which the returning light beam is imaged and distributed over a 2D-area 201 of the image sensor, i.e. over the light receiving area of the image sensor. The 2D-sensor may be a CCD or CMOS sensor, preferably a low cost, a >1 megapixel sensor where each horizontal pixel array consists of e.g. 1000 pixels. This sensor replaces the more expensive line scanner typically used. The 2D- area illuminated by the beam is then further subdivided. To this end, the image sensor and/or the associated signal processing circuit may be configured to selectively only read out and/or process image pixels from selected sub-areas of the 2D area 201 . In the illustrated example, the area is subdivided into a number of straight strips 202, which can efficiently be implemented using either a CCD or CMOS sensor. Other examples of subareas, such as rectangles, crosses etc. could be envisioned, but these may mostly be suitable when using a CMOS sensor, where each pixel can be read out independently. Each sub-area, e.g. each strip, is comprised of a number of pixels 207. In the illustrated example, the sensor area is divided into five lines, covering only a fraction of the illuminated area of the image sensor, and the information from the remaining number of pixels is discarded. This has the advantage that the time needed for reading out the sensor is reduced.

In some embodiments, the strips, or other types of sub-areas, that are read out comprise only a small fraction of the total number of pixels of the image sensor, for example 10%, 5% or even down to only 2% of the pixels on the sensor. This has the advantage that readout is much faster than when using data from all available pixels.

As described above, in some embodiments, the apparatus may project an illumination pattern onto the illuminated area of the target tissue. Preferably, the projected pattern is aligned with the sub-areas, in particular such that the illuminated parts of the projected pattern are imaged onto the selected sub-areas of the image sensor's 2D area 201 , thereby reducing the total illuminance of the tissue and preventing noise from areas that are not illuminated and shall not be imaged.

A zoomed-in view 203 of one of the strips 202n is shown. In this view, it is illustrated how the strip 202n comprises a grid of pixels 207. In this example, strip 202n comprises five rows of pixels, e.g. such that each strip includes 1000x5 pixels. Furthermore, when read out, the pixels 207 are binned or bundled, such that the bundled pixels 204a, 204b...204n, each correspond to one measurement or data point. By bundling the pixels in this way, each measurement has a higher signal to noise ratio, and all strips or sub-areas are read out simultaneously, increasing the speed of signal acquisition.

The bundled pixels from the sub-areas thus provide a two-dimensional array of data points, which may be considered pixels of a reduced-resolution 2D image having a resolution smaller than the native pixel resolution of the image sensor.

By performing depth-scanning (using time-domain or frequency-domain OCT) respective A-scans may be concurrently obtained at each bundled pixel, resulting in a two-dimensional array of depth-resolved interference profiles (A-scans). The arrays of A-scans thus provide a volumetric representation of the target tissue (C-scan). A C-scan may thus be obtained within one sweep cycle of the swept-source laser (or accumulated over multiple sweeps). At least some embodiments of the apparatus described herein may thus be considered to concurrently obtain multiple line-field OCT data sets without the need for laterally scanning a light beam across the tissue surface.

The image data acquired by various embodiments of the apparatus disclosed herein provide depth-resolved interferometric image data from which various representations may be created. Accordingly, the signal processing circuit of various embodiments may be configured to process the sensor signals from the image sensor to obtain one or more images, which may include a volumetric image representation, one or more B-scans of respective cross sections, one or more en-face representations of one or more tissue layers at respective penetration depths beneath the tissue surface, and/or other types of images.

Embodiments of the method described herein can be implemented by means of hardware comprising several distinct elements. In the apparatus claims enumerating several means, several of these means can be embodied by one and the same element, component or item of hardware. The mere fact that certain measures are recited in mutually different dependent claims or described in different embodiments does not indicate that a combination of these measures cannot be used to advantage.

It should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, elements, steps or components but does not preclude the presence or addition of one or more other features, elements, steps, components or groups thereof.

Claims

Claims:

1 . An optical coherence tomography apparatus for imaging a target tissue, in particular a retina of a patient’s eye, the apparatus comprising:

- a light source for emitting light,

- an optical system configured to direct a sample portion of the emitted light as a sample beam of light onto a 2-dimensional area on the target tissue to be imaged, the optical system being further configured to direct a reference portion of the emitted light as a reference beam onto a reflector,

- a 2-D image sensor comprising an array of sensor pixels, wherein the optical system is further configured to receive a reflected portion of the sample beam, reflected by the target tissue, and a reflected portion of the reference beam, reflected by the reflector, and to direct the received reflected portions onto the image sensor to create an interferometric image of the target tissue;

- a signal processing circuit configured to process sensor signals from the image sensor to obtain one or more depth-resolved images of the target tissue; wherein the signal processing circuit is configured to bundle groups of sensor pixels into respective data points, such that each data point comprises the combined response from a plurality of bundled pixels and is indicative of interferometric image information of a portion of the target tissue.

2. The apparatus according to claim 1 , wherein the signal processing circuit is configured to select a group of sub-areas within the light-receiving area of the image sensor and to selectively only process pixels from the selected sub-areas.

3. The apparatus according to any of the preceding claims, the apparatus further configured to direct the sample beam onto the target tissue so as to create a projected pattern within the 2-dimensional area on the target tissue, in particular a pattern corresponding to the selected group of subareas.

4. The apparatus according to the previous claim, wherein the pattern comprises a line pattern, in particular a line pattern selected from: a plurality of parallel lines, a cross, a grid formed by mutually intersecting lines, a plurality of lines intersecting in a common intersection point, a plurality of concentric circles.

5. The apparatus according to claim 3 or 4, wherein the pattern is generated using one or more pattern generation optical elements.

6. The apparatus according to claim 3 or 4, wherein the pattern is generated by a lens array, in particular a 1 -D or 2-D lens array.

7. The apparatus according to the preceding claim, wherein the one or more pattern generation optical elements are mounted on a wheel or slide for selection on demand.

8. The apparatus according to claim 3 or 4, wherein the pattern is generated using a digital mirror device (DMD) array.

9. The apparatus according to claim 3 or 4, where in the pattern is generated using a spatial light modulator.

10. The apparatus according to any of the preceding claims, wherein the apparatus is a swept-source optical coherence tomography apparatus and the light source is a swept-source laser.

11. The apparatus according to any of the preceding claims, further comprising an attachment mechanism for attaching to a slit lamp.