Inspection apparatus of the ocular fundus

Abstract

The present invention relates to an inspection apparatus of the ocular fundus. The apparatus according to the invention comprises a first arrangement of components for acquiring images of the retina through line scanning ophthalmoscopy, a second arrangement of components for acquiring images of the retina by optical coherence tomography and a control arrangement to control the operation of said first and second arrangement of components.

Description

[0001] INSPECTION APPARATUS OF THE OCULAR FUNDUS

[0002] DESCRIPTION

[0003] The present invention relates to an inspection apparatus of the ocular fundus. In particular, the present invention relates to an inspection apparatus of the ocular fundus capable of acquiring images of the retina through line scanning ophthalmoscopy (hereinafter “LSO”) and optical coherence tomography (hereinafter “OCT”).

[0004] In the state of the art, there are known inspection apparatus of the ocular fundus capable of combining the operations of a line scanning ophthalmoscopic device (hereinafter “LSO device”) and of a device for acquiring images of the retina by optical coherence tomography (hereinafter “OCT device”) in order to allow a more accurate and complete diagnosis of possible diseases of the eye.

[0005] An example of this type of inspection apparatus of the ocular fundus is described in the patent document US7648242B2.

[0006] In these systems, a dichroic beam splitter (dichroic mirror) is typically used to direct the illumination beams of the LSO device and of the OCT device along corresponding optical paths that pass through a series of common optical components (for example an ocular lens and an optical scanning assembly) before reaching the retina.

[0007] As is known, a dichroic beam splitter can be produced to be transparent for a light radiation having a first wavelength band and reflect a light radiation having a second wavelength band. For example, it can be passed through by the illumination beam coming from the light source of the LSO device and reflect the illumination beam coming from the light source of the OCT device so that both the illumination beams pass through some common components in common (positioned downstream of the beam splitter) before reaching the retina.

[0008] The use of a dichroic beam splitter causes some problems.

[0009] With regard to image acquisition by means of OCT, it has been noted how this component introduces different optical delays for the different groups of photons composing the illumination beam of the OCT device causing a group delay dispersion (GDD).

[0010] This phenomenon has negative effects on the coherence of the illumination beam, which can cause a reduction of the axial resolution in the images of the retina acquired by the OCT device. Moreover, the presence of a GDD can cause the appearance of artifacts in the images acquired. To mitigate these drawbacks, it is possible to use a dichroic beam splitter designed to reduce the GDD. However, these devices (Low GDD) are costly to produce on an industrial scale and their use can also cause a reduction of the axial resolution in the images of the retina acquired. With regard to image acquisition by means of LSO, it has been noted how the dichroic beam splitter can introduce undesirable reflections, spectrum variations or optical power losses in the illumination beam of the LSO device. These drawbacks cause, as a whole, a reduction of the quality of the images of the retina acquired.

[0011] The main aim of the present invention is to provide an inspection apparatus of the ocular fundus capable of acquiring images of the retina by LSO and OCT, which allows the drawbacks of the prior art, set forth above, to be overcome.

[0012] Within this aim, an object of the present invention is to provide an inspection apparatus of the ocular fundus that does not require the use of dichroic beam splitters or other additional optical components with similar functions to direct the various illumination beams of the retina along the corresponding optical paths.

[0013] A further object of the present invention is to provide an inspection apparatus of the ocular fundus capable of acquiring LSO and OCT images of the retina with very high quality.

[0014] A further object of the present invention is to provide an inspection apparatus of the ocular fundus characterized by very simple assembly and flexible use.

[0015] A further object of the present invention is to provide an inspection apparatus of the ocular fundus that is easy to manufacture on an industrial scale, at costs competitive with systems of similar type currently available on the market.

[0016] This aim and these objects, as well as other objects that will be apparent from the description below and from the accompanying drawings, are achieved, according to the invention, by an inspection apparatus of the ocular fundus according to the appended claim 1 and the related dependent claims.

[0017] Features and advantages of the inspection apparatus of the ocular fundus, according to the invention, may be better perceived by referring to the description given below and to the accompanying figures, provided purely for non-limiting illustrative purposes, wherein:

[0018] - Fig. 1 schematically illustrates the inspection apparatus of the ocular fundus, according to the invention, in an embodiment thereof;

[0019] - Figs. 2-5 schematically illustrate some parts of the inspection apparatus of Fig. 1;

[0020] - Fig. 6 schematically illustrates a procedure for acquiring a B-scan image of the retina performed by the inspection apparatus of Fig. 1;

[0021] - Figs. 7-8 schematically illustrate the acquisition of a B-scan image during the aforesaid acquisition procedure.

[0022] With reference to the aforesaid figures, the present invention refers to an inspection apparatus of the ocular fundus 500 capable of combining the functions of an LSO device and of an OCT device.

[0023] The apparatus 500 comprises a first arrangement of components 500a for acquiring images of the retina by LSO, a second arrangement of components 500b for acquiring images of the retina by OCT and a control arrangement 10, 50 to control the operation of the apparatus.

[0024] In general, the arrangements of components 500a, 500b can be of any type, according to requirements. Therefore, the object of the invention must not be considered in any way limited to the examples described below and in the cited figures.

[0025] The first arrangement of components 500a comprises a first illumination unit 11 configured to project a first light beam Li to illuminate the retina 101 of an eye 100 of a patient.

[0026] The first arrangement of components 500a further includes a first optical path 1 for the first light beam Li emitted by the first light source. Along the first optical path 1, the light beam Zy, coming from the light source 111, travels in direction Di until reaching the retina 101.

[0027] The illumination unit 11 comprises a first light source 111, for example an LED (Light Emitting Diode) device.

[0028] Preferably, the illumination unit 11 includes a projecting diaphragm 112 comprising a first projecting aperture for shaping the light beam Li and arranged so as to be optically conjugated with the retina 101 (during use of the apparatus 500).

[0029] For greater clarity of explanation, it is specified that, within the scope of the present invention, the definition “optically conjugated” identifies the positioning in the exact optical conjugation position or in a relatively small region around the exact optical conjugation position (with respect to the lengths of the optical paths of the light beams in the apparatus 500).

[0030] Preferably, the illumination unit 11 includes a first collimating lens 113 positioned close to the light source 111.

[0031] The first arrangement of components 500a comprises a first image acquisition unit 27 configured to receive a second light beam L2 that includes light reflected by the retina illuminated with the first light beam Li projected by the first light source 111.

[0032] The first arrangement of components 500a further includes a second optical path 2 for the second light beam L2. Along the second optical path 2, the light beam Z2, coming from the retina 101, travels in the direction D2 until reaching the image acquisition unit 27.

[0033] The acquisition unit 27 can include, for example, CCD or C-MOS sensors of a digital video camera arranged so as to receive the second light beam Z2, at a receiving surface, and allow observation and filming of the retina 101.

[0034] The first arrangement of components 500a comprises a first scanning mirror 17 configured to reflect and direct the first light beam Li toward the retina 101 along the first optical path 1. The first scanning mirror 17 is rotatably movable around a respective axis of rotation to scan (i.e., project and move) the first light beam Li along the surface of the retina, according to a desired scanning direction.

[0035] Preferably, as illustrated in Fig. 1-2, the scanning mirror 17 is configured to reflect and direct the second light beam L2 toward the first image acquisition unit 27 along the second optical path 2.

[0036] Preferably, the scanning mirror 17 is operatively coupled to a corresponding actuator 170 capable of rotating it around the corresponding axis of rotation (Fig. 2). The actuator 170 is electronically controllable by a suitable drive module (not illustrated), in turn controlled by a control unit 10.

[0037] The scanning mirror 17 can include, for example, an oscillating resonant, galvanometric or similar type of mirror, provided with a pair of reflecting surfaces opposite each other (Fig. 2). In this case, the second light beam L2 undergoes a first reflection at a first surface of the scanning mirror, in which it is de-scanned and transformed into a stationary light beam, and a second reflection, at a second surface of the scanning mirror, in which it is re-scanned in order to generate a two-dimensional image of the retina acquired by the acquisition means 27.

[0038] Other construction solutions in which the scanning mirror 17 consists of a polygonal mirror, an array of micromirrors, or similar, are also possible.

[0039] The first arrangement of components 500a comprises a light beam separator 16 to separate the second light beam L2 that travels along the second optical path 2 from the first light beam Li that travels along the first optical path 1. In other words, the light beam separator 16 is arranged to separate the light L2 reflected by the retina from the light Li projected thereon.

[0040] Preferably, the first scanning mirror 17, the light beam separator 16 and the first acquisition unit 27 are arranged in succession along the second optical path 2 (with reference to the direction D2 of the second light beam Z2).

[0041] The light beam separator 16 can include a separation diaphragm 161 optically conjugated with the pupil 102, during use of the apparatus 500, and provided with an appropriate shaped aperture for the passage of the second light beam L2 (Fig. 2).

[0042] The light beam separator 16 can also include a fixed mirror 162 to direct the second light beam L2 along the second optical path 2 after the passage through the separation diaphragm 161 (Fig. 2).

[0043] Preferably, the first arrangement of components 500a comprises a first lens 15, arranged along the optical path 1 between the illumination unit 11 and the first scanning mirror 17, as well as a scanning lens 18 and an ocular lens 19 arranged downstream of the first scanning mirror 17. The first light beam Li passes through the scanning lens 18 and the ocular lens 19 before it reaches the eye 100, and the second light beam L2 passes through them before it reaches the scanning mirror 17.

[0044] Preferably, the first arrangement of components 500a comprises a confocal diaphragm 23 arranged along the optical path 2 of the second light beam L2 to be optically conjugated with the retina 101, during use of the apparatus 500.

[0045] The confocal diaphragm 23 preferably comprises at least one confocal aperture appropriately shaped to allow the passage of the light beam L2 and at least partially block undesirable light reflected by surfaces of the apparatus 500 or of the eye 100 that are not optically conjugated with the retina.

[0046] Preferably, the first arrangement of components 500a further comprises a second lens 21, the fixed mirrors 22, 24, a third lens 25, an objective lens 26 arranged along the optical path 2 of the second light beam L2 between the light beam separator 16 and the first acquisition unit 27 (with reference to the direction of travel D2 of the second light beam L2 along the second optical path).

[0047] In general, the illumination unit 11, the first scanning mirror 17 and the light beam separator 16 can be produced according to known solutions. Therefore, hereinafter these components of the apparatus 500 will not be described in further detail, but only with reference to the aspects relevant to the invention, for reasons of brevity of exposition.

[0048] The aforesaid optical components 15, 18, 19, 21, 22, 23, 24, 25, 26 of the first arrangement of components 500a can also be produced according to known solutions and will not be described in further detail herein for evident reasons of brevity of description.

[0049] The first arrangement of components 500a could be configured differently from the solution illustrated, by way of example, in Fig. 1 provided that it is capable of creating a so-called “side by side” separation of the illumination light beam (first light beam Zy) and of the acquisition light beam (second light beam Z2). With this definition, it is meant that the illumination beam Li enter the eye 100 at a first portion 1021 of the pupil 102 and that the acquisition beam L2 exits from the eye 100 at a second portion 1022 of the pupil 102, distinct and separate from the aforesaid first portion of pupil (Fig. 5).

[0050] In other words, the first arrangement of components 500a could include optical components completely different from those described along at least one of the optical paths 1, 2 described above and in association with at least one between the first illumination unit 11, the light beam separator 16, the first scanning mirror 17 and the first acquisition unit 27. The control arrangement of the apparatus 500 comprises a first control unit 10 configured to control the operation of the first control arrangement 500a.

[0051] The control unit 10 is advantageously configured to carry out functions for acquiring signals, memorizing data, calculating data, generating control signals and providing images Wo of the retina after optional processing the images acquired.

[0052] Preferably, the control unit 10 comprises at least one digital processing device, for example a microprocessor.

[0053] The control unit 10 is operatively associated with the first illumination unit 11, with the first scanning mirror 17 and with the first acquisition unit 27 and is capable of controlling the operation of these devices generating appropriate command and control signals.

[0054] To generate these control signals, the control unit 10 preferably executes suitable software instructions stored in one or more memory locations of said control unit.

[0055] The control unit 10 can also include or be operatively associated with a human-machine interface (not illustrated) for entering manual commands, for executing configuration or programming operations and for viewing the images of the retina provided.

[0056] The control unit 10 can be an electronic device, stand alone or integrated in a further control unit 50 intended to control the operation of the second arrangement of components 500b. The control unit 10 can also be integrated in the first acquisition unit 27.

[0057] As indicated above, the second arrangement of components 500b is arranged to provide images of the retina 101 of an eye 100 acquired by OCT.

[0058] The second arrangement of components 500b can be arranged to provide images f of the retina 101 of various type, for example A-scan. B-scan. C-scan images. Hereinafter, it will be described with particular reference to the acquisition of B-scan images, without intending to limit the scope of protection of the invention.

[0059] The second arrangement of components 500b can be of various type as a function of the OCT technique used. For example, it can be produced for acquiring images of the retina by optical coherence tomography of SD-OCT (Spectral Domain OCT) type or of SS-OCT (Swept Source OCT) type.

[0060] With reference to Fig. 3, the second arrangement of components 500b comprises a light source 52, preferably configured to emit a coherent electromagnetic radiation. For the applications of relevance, this light source can, for example, be a laser (Swept Source) or an SLD (Super- Luminescent Diode) preferably configured to emit light with a wavelength in the infrared range. In some applications (SS-OCT), the light source 52 can be configured to emit a light beam according to a sequence of emission cycles, during each of which the radiation emitted is in a very narrow band with a wavelength that is varied very rapidly and progressively in a predefined range of wavelengths.

[0061] In other applications, for example of SD-OCT type, the light source 52 can be configured to emit a broadband light radiation.

[0062] In general, the second light source 52 can be produced according to known solutions. Therefore, this component of the apparatus 500 will not be described in further detail, for evident reasons of brevity of description.

[0063] The second arrangement of components 500b comprises an optical detection unit 53 optically coupled to the light source 52.

[0064] The optical detection unit 53 is configured to receive a light radiation Ls coming from the light source 52 and provide at the output an interferometric optical signal II obtained by optical interference between a measurement light beam L- and a reference light beam LR provided by a pair of interferometric arms.

[0065] The optical detection unit 53 thus forms an interferometric structure that can be produced according to a known configuration, such as a Michelson or Mach-Zender configuration.

[0066] The optical detection unit 53 comprises a measurement interferometric arm 54 and a reference interferometric arm 56 optically coupled to the light source 52.

[0067] During use of the apparatus 500, the measurement interferometric arm 54 is optically coupled to the retina 101 of an eye 100 of the patient to be examined and is configured to receive at the input a third light beam Ls and provide at the output the measurement light beam LM.

[0068] The third light beam Ls includes a first portion of the light radiation Ls coming from the light source 52 while the measurement light beam LM includes light radiation back-scattered from the retina 101 after it has been illuminated with the third light beam Ls.

[0069] The measurement interferometric arm 54 preferably includes a same third optical path 3 along which the third light beam Ls is conveyed toward the retina 101 and the measurement light beam L is conveyed in the opposite direction.

[0070] Fig. 4 schematically illustrates the measurement interferometric arm 54 of the second arrangement of components 500b.

[0071] The interferometric arm 54 comprises an optical port 545 configured to receive the third light beam Ls intended to illuminate the retina 101.

[0072] The optical port 545 can advantageously consist of the end of an appropriately arranged optical fibre. The optical port 545 is arranged so as to be optically conjugated with the retina 101, during use of the apparatus 500. In this way, the third light beam Ls has a focal point positioned close to the surface of the retina, during inspection thereof.

[0073] The interferometric arm 54 further comprises a scanning assembly 540 configured to scan (i.e., project and move) the third light beam Ls on the retina 101.

[0074] The scanning assembly 540 advantageously comprises at least one optical scanning mirror controllable by a control unit 50. In this way, during optical scanning, the scanning assembly 540 can project and move the third light beam Ls on the retina 101 to cover a desired optical field and illuminate a desired portion of the retina.

[0075] Preferably, the interferometric arm 54 comprises a collimation assembly 546 of the third light beam Ls optically coupled to the scanning assembly 540.

[0076] The collimation assembly 546 is advantageously arranged between the optical port 541 and the scanning assembly 540. It is configured to receive the third light beam Ls from the optical port 41 and transmit this light beam to the scanning assembly 540.

[0077] When the third light beam Ls is transmitted from the optical port 541 it has light rays that naturally tend to diverge conically. The collimation assembly 546 has the task of making the light rays of the third light beam Ls entering the scanning assembly 540 substantially parallel to one another.

[0078] In general, the optical port 545 and the collimation assembly 546 can be produced according to known solutions. Therefore, these components of the apparatus 500 will not be described in further detail either, for evident reasons of brevity of description.

[0079] If the light beams Ls, L travel along a same optical path 3 in the measurement interferometric arm 54 (as illustrated in Fig. 3), the measurement light beam LM, also passes through the aforesaid optical components 540, 545, 546 of the measurement interferometric arm 54 in the opposite direction relative to the third light beam Ls. In this case, the optical port 45 can be used also to provide the measurement light beam LM at the output from the measurement interferometric arm.

[0080] As mentioned above, the scanning assembly 540 comprises one or more scanning mirrors 542, 543 movable in a controlled manner to reflect the third light beam Ls. The aforesaid one or more scanning mirrors are rotatably movable about respective axes of rotation to move the third light beam Ls on the retina 101 according to respective optical scanning directions perpendicular to one another.

[0081] Preferably, the scanning assembly 540 includes a second scanning mirror 542 to reflect and direct the third light beam Ls along the third optical path 3. This scanning mirror is rotatably movable about a corresponding axis of rotation to move the third light beam Ls along the surface of the retina 101, according to a first scanning direction (for example a direction Y) of the retina (Figs. 7-8).

[0082] Preferably, the scanning mirror 542 is operatively coupled to a corresponding actuator 542a capable of moving it about the corresponding axis of rotation (Fig. 2). The actuator 542a is electronically controllable by an appropriate drive module (not illustrated), in turn controlled by a control unit 50.

[0083] Preferably, the scanning assembly 540 includes a third scanning mirror 543 to reflect the third light beam L3. This scanning mirror is rotatably movable about a corresponding axis of rotation to move the third light beam L3 along the surface of the retina 101, according to a second scanning direction (for example a direction X ± Y) of the retina (Figs. 7-8).

[0084] Preferably, the scanning mirror 543 is operatively coupled to a corresponding actuator 543a capable of moving it about the corresponding axis of rotation (Fig. 2). The actuator 543a is electronically controllable by an appropriate drive module (not illustrated), in turn controlled by a control unit 50.

[0085] Preferably, the axes of rotation of the scanning mirrors 542, 543 of the scanning assembly 540 are perpendicular to one another.

[0086] Preferably, the axis of rotation of the second scanning mirror 542 is parallel to the axis of rotation of the first scanning mirror 17 of the first arrangement of components 500a.

[0087] The scanning mirrors 542, 543 can be galvanometric mirrors, or of similar type.

[0088] In general, the scanning mirrors 542, 543 can be produced according to known solutions. Therefore, these components of the apparatus 500 will not be described in further detail either, for evident reasons of brevity of description.

[0089] The reference interferometric arm 56 of the optical detection unit 53 includes an optical reference T (for example a reflecting element included in the reference interferometric arm) and is configured to receive at the input a fourth light beam L4 and provide at the output the reference light beam LR.

[0090] The fourth light beam L4 includes a second portion of the light radiation Ls coming from the light source 52 while the reference light beam LR includes light radiation reflected from the optical reference T illuminated with the fourth light beam L4.

[0091] The reference interferometric arm 56 preferably includes a same fourth optical path 4 along which the fourth light beam L4 is conveyed towards the optical reference T and the reference light beam LR is conveyed in the opposite direction.

[0092] Preferably, the fourth optical path 4 has an optical length adjustable in relation to the length of the third optical path 3 in the measurement interferometric arm 54.

[0093] Preferably, the optical detection unit 3 comprises a fibre optic array 57 configured to optically couple the measurement interferometric arm 54 and the reference interferometric arm 56 to each other and to the light source 52.

[0094] The fibre optic array 57 is configured to receive a light radiation Ls coming from the light source 52, convey a first portion of this light radiation toward the measurement interferometric arm 54 to form the third light beam Ls and convey a second portion of this light radiation toward the reference interferometric arm 56 to form the fourth light beam L4.

[0095] The fibre optic array 57 is configured to convey the measurement light beam LM, coming from the measurement interferometric arm 54, toward an output port combining it with the reference light beam LR coming from the reference interferometric arm 56. The aforesaid fibre optic array thus provides at the output an interferometric optical signal II (also called “measurement interferogram ”) generated by the optical interference between the measurement light beam LM (radiation backscattered from the retina 101 illuminated with third light beam / ..?) and the reference light beam LR (radiation reflected by the optical reference illuminated with the fourth light beam LJ).

[0096] The interferometric optical signal II is indicative of a reflectivity profile along the axial depth of the portion of retina illuminated with the third light beam Ls.

[0097] The second arrangement of components 500b comprises a second acquisition unit 58 optically coupled (for example by optical fibre) to the optical detection unit 3.

[0098] The acquisition unit 58 is configured to receive the interferometric signal II and provide sampling data indicative of the aforesaid interferometric signal.

[0099] The acquisition unit 58 can comprise a conversion module (not illustrated) configured to convert the interferometric signal II into a corresponding electrical detection signal. This conversion module can include, for example, a spectrometer or an assembly of photodiodes.

[0100] The acquisition unit 58 can also include an interface module (not illustrated) configured to receive the electrical detection signal, provided by the aforesaid conversion module, and perform sampling thereof through known data and signal processing algorithms. This interface module can include appropriate microprocessor circuits, FPGAs, or electronic circuits of other type mounted on an appropriate circuit board.

[0101] In general, the second acquisition unit 58 can be produced according to known solutions. Therefore, these components of the apparatus 500 will not be described in further detail either, for evident reasons of brevity of description. Naturally, the second arrangement of components 500b could include further optical components, in addition to those mentioned above. The second arrangement of components 500b could, for many aspects, be configured differently to the solution illustrated, by way of example, in Fig. 3 provided that the measurement interferometric arm 54 of the arrangement of components is provided with at least one scanning mirror of the third light beam L3.

[0102] The control arrangement of the apparatus 500 comprises a second control unit 50 configured to control the operation of the components of the second control arrangement 500b.

[0103] Preferably, the control unit 50 comprises at least one digital processing device, for example a microprocessor.

[0104] The control unit 50 is operatively connected to the second acquisition unit 58 and is advantageously configured to execute processing functions of data and signals provided thereby to obtain images Wf of the retina. These images of the retina can be of various type, for example A-Scan, B-Scan or C-Scan. The operation of the control unit 50 will be described herein with particular reference to obtaining B-scan images of the retina.

[0105] Preferably, the control unit 50 comprises at least one data processing module (not illustrated) configured to process the sampling data provided by the interface module of the second acquisition unit 58 and obtain the images Wf of the retina.

[0106] The control unit 50 is advantageously also configured to perform control functions of the operation of the second control arrangement 500b.

[0107] Preferably, the control unit 50 is operatively associated with the second illumination unit 52, with the scanning mirrors 541, 542 of the scanning assembly 540, with the scanning lens 18 and with the second acquisition unit 58 and is capable of controlling the operation of these devices by generating appropriate command and control signals.

[0108] To generate these control signals, the control unit 50 preferably executes appropriate software instructions stored in one or more memory locations of said control unit.

[0109] Naturally, the control unit 50 can be configured also to control the operation of other components of the second arrangement of components 500b.

[0110] The control unit 50 can include or also be operatively associated with a human-machine interface (not illustrated) for entering manual commands, for executing configuration or programming operations and for viewing the images of the retina provided.

[0111] The control unit 50 can be a free-standing electronic device or be integrated in the first control unit 10 intended to control operation of the first arrangement of components 500a. The control unit 50 can also be integrated in the second acquisition unit 58 and / or the first acquisition unit 27.

[0112] From the above, it is evident that the first control unit 10 and the second control unit 50 form a control arrangement of the apparatus 500 configured to control the operation thereof, in particular of the arrangements of components 500a, 500b.

[0113] The arrangements of components 500a, 500b can be integrated with each other so as to have some optical components in common arranged along the optical paths 1, 2, 3 of the light beams Zy, Z2, L3. Preferably, the interferometric arm 54 of the second arrangement of components 500b comprises some optical components in common with the first arrangement of components 500a, in particular the scanning lens 18 and the ocular lens 19. Therefore, the third light beam L3, before it reaches the retina 101 along the corresponding optical path 3, and the measurement light beam - also pass through these optical components, if the light beams Z5, LM travel along a same optical path 3 in the measurement interferometric arm 54 (as illustrated in Fig. 3).

[0114] A peculiar aspect of the apparatus 500 consists in the fact that the aforesaid first and second arrangements of components 500a, 500b are integrated with each other without the use of additional optical components (for example a dichroic beam splitter) which compromise the quality of the images of the retina acquired by LSO and OCT.

[0115] For this purpose, the scanning assembly 540 of the measurement interferometric arm 54 of the second arrangement of components 500b comprises a second scanning mirror 542 arranged in a region 510 of the apparatus 500 delimited by the first scanning mirror 17, by the light beam separator 16 of the first arrangement of components 500a and by the optical paths of the first and second light beam Zy, Z2 (Fig. 2)

[0116] It should be noted that, in the region 510 of the apparatus 500, the light beams Zy, Z2 are stationary during use of the apparatus 500. In fact, the first light beam Zy is scanned by the first scanning mirror 17 positioned farther downstream (with reference to the direction of travel Z>y of the first light beam Zy) while the second light beam Z2 is de-scanned by the first scanning mirror 17 positioned farther upstream (with reference to the direction of travel D2 of the second light beam L2).

[0117] Preferably, the second scanning mirror 542 is arranged to reflect and direct the third light beam L3 toward the first scanning mirror 17 along a portion 3a of the third optical path 3 positioned between the first optical path 1 of the first light beam Li and the second optical path 2 of the second light beam Z2. The first scanning mirror 17 reflects and directs the third light beam L3 toward the retina 101 along the third optical path 3.

[0118] Therefore, thanks to the particular positioning of the scanning mirror 542 of the optical scanning assembly, the second arrangement of components 500b also includes the first scanning mirror 17, naturally in common with the first arrangement of components 500a.

[0119] In the embodiment illustrated in Figs. 1-2, the first scanning mirror 17 reflects and directs the light beams Li, L2, L3 along the corresponding optical paths 1, 2, 3, during use of the apparatus 500.

[0120] Preferably, the second scanning mirror 542 is placed close to the light beam separator 16 in a position more or less optically conjugated with the pupil 102 of the eye 100, during use of the apparatus 500. In this way, as shown in Fig. 5, the third light beam L3 passes through a third portion of pupil 1023 located between the first portion of pupil 1021, through which the first light beam Li enters the eye, and the second portion of pupil 1022, through which the second light beam L2 exits from the eye.

[0121] It should be noted how the third portion of pupil 1023, through which the third light beam L3 passes, is distinct and separate from the portions of pupil 1021, 1022 through which the light beams Zy, L2 pass.

[0122] Preferably, the light beam L3 passes through the pupil in an approximately central area thereof. Preferably, at the pupil 102 of the eye, the light beams Zy, Z2, L3 are aligned with one another as shown in Fig. 5. In principle, however, the light beams Zy, Z2, L3 could also be staggered from one another at the pupil 102 of the eye.

[0123] It should be noted how in the embodiment of Fig. 2, the arrangement of components 500b in fact includes a system of three scanning mirrors 17, 542, 543 for scanning the third light beam L3 on the retina 101 of the eye.

[0124] The scanning assembly 540 receives at the input the third light beam L3 (having a direction of travel D3) after it has been collimated by the collimation assembly 546 after having been passed through the optical port 545.

[0125] The third light beam L3 undergoes a first reflection, at the third scanning mirror 543 and a second reflection at the second scanning mirror 542. Downstream of the scanning assembly 540, the light beam L3 undergoes a third reflection at the first scanning mirror 17. Subsequently, the light beam L3 travels toward the retina 101 passing through the scanning lens 18 and the ocular lens 19.

[0126] During optical scanning of the retina 101 (i.e., during the execution of at least one optical scanning cycle to acquire an image of the retina by OCT), the scanning mirrors 17, 542, 543 can move in a synchronized manner around the corresponding axes of rotation and cooperate with one another to reflect and direct the illumination beam L3 toward the retina 100.

[0127] The control unit 50 controls the operation of the three scanning mirrors 17, 542, 543 so that they move with appropriately calculated angles of rotation.

[0128] Thanks to their synchronized movement, the first, second and third scanning mirror 17, 542, 543 move the third illumination beam Li along the surface of the retina 101 according to corresponding motion laws 0(1), My(t) n Mx(t). These motion laws are predefined or can be calculated in real time or selected from a memory by the control unit 50 based on the desired scanning trajectory.

[0129] As will be more apparent below, according to some operating modes of the apparatus 500, the first scanning mirror 17 can be maintained in fixed position during acquisition of an image of the retina by OCT. In this case, the corresponding motion law of the first scanning mirror 17 is of the type 0(t) = 0, where 0is a predefined angle.

[0130] In the embodiments of the invention (Fig. 3) in which the measurement interferometric arm 54 is produced so that the light beams L3, L travel along a same optical path, the measurement light beam L travels along the optical path 3 in the opposite direction relative to the third light beam L3. In this case, the measurement light beam LM, coming from the retina 101, after having passed through the ocular lens 19 and the scanning lens 18, undergoes three successive reflections by the scanning mirrors 17, 542, 543. The combination of these successive reflections de-scans the measurement light beam LM before travelling toward the collimator 546 and, subsequently, the optical port 545 of the optical scanning assembly.

[0131] With regard to obtaining images Wo of the retina by LSO, the apparatus 500 can operate according to conventional modes. For this purpose, the control arrangement 10, 50 can carry out known procedures for acquiring images of the retina, not described in detail herein for brevity of description.

[0132] With regard to obtaining images Wf of the retina by OCT, the operating modes of the apparatus 500 depend substantially on the behaviour of the first scanning mirror 17, in particular on whether it remains in fixed position or moves oscillating about its axis of rotation.

[0133] According to a first operating mode, the control arrangement 10, 50 commands the first scanning mirror 17 to remain fixed in a predefined position and commands each of the scanning mirrors 542, 543 to move the third light beam L3 on the retina 101 along a corresponding optical scanning direction, according to a corresponding motion law calculated to move the third light beam L3 according to a desired optical scanning trajectory.

[0134] The main advantage of this operating mode consists in its simplicity. To obtain images Wf of the retina by OCT, the apparatus 500 can in fact operate as if the first arrangement of components 500a were not present. For this purpose, the control arrangement 10, 50 can execute known procedures for acquiring images of the retina, not described in detail herein for brevity of description.

[0135] It is evident how the possibility of operating according to the aforesaid first operating mode considerably improves the versatility of use of the apparatus 500, which can be easily used both as OCT ophthalmic machine and as combined ophthalmic machine (OCT+LSO), according to requirements.

[0136] However, a disadvantage of this operating mode consists in the fact that it does not allow the use, in real time or during post-processing, of information deriving from images of the retina by LSO to improve the quality of the images of the retina acquired by OCT, for example to perform appropriate tracking procedures of the movements of the retina during acquisition of said images.

[0137] According to a second operating mode, the control arrangement 10, 50 commands the first scanning mirror 17 to move the third light beam Ls on the retina with a predefined motion law 0(t) and commands each of the scanning mirrors 542, 543 to move the third light beam on the retina along a corresponding optical scanning direction according to a corresponding motion law.

[0138] Preferably, the first optical scanning mirror 17 moves the illumination beam Ls with a periodic, for example sinusoidal, motion law 0(t). This means that the first scanning mirror 17 can move (for example oscillating about the corresponding axis of rotation) with relatively low dynamic performances.

[0139] The scanning mirrors 17, 542, 543 adopt, time by time, combinations of angles of rotation different from one another in order to reflect the illumination beam Ls toward a desired position on the retina.

[0140] For obvious reasons of geometric optics, each combination of angles of rotation of the aforesaid scanning mirrors corresponds to a different length of optical path of the illumination beam Ls. The combination of movements of the scanning mirrors 17, 542, 543 (in particular of the scanning mirrors 17, 542 having axes of rotation parallel to one another in the embodiment of Fig. 2) thus determines a cyclic variation Z(t) of the length of the optical path of the illumination beam L3 along the measurement interferometric arm 4.

[0141] This has consequences with regard to the acquisition of successive series of A-scan images, in order to compose a B-scan image of the retina. In fact, the A-scan images acquired are necessarily affected by cyclic distortion along an axial direction Z perpendicular to the surface of the retina.

[0142] This circumstance can be advantageously exploited to remove the speckle noise from the B- scan images acquired, given that the speckle pattern of each B-scan image depends substantially on the optical path difference (OPD) between the optical paths 3, 4 of the illumination beams L3, L4 along the interferometric arms 54, 56 of the detection unit 53 of the second arrangement of components 500b. The variation function Z(t) of the optical path difference of the illumination beam L3, along the axial direction Z, depends on the motion law 0(t) with which the first scanning mirror 17 moves the third light beam L3 along the surface of the retina.

[0143] For example, in the case in which the first scanning mirror 17 moves the illumination beam L3 with a periodic motion law 0(t), the variation function Z(t) of the optical path difference of the illumination beam Li will also have a cyclic trend.

[0144] As mentioned above, according to the aforesaid second operating mode of the apparatus 500, the first scanning mirror 17 moves continuously (preferably with oscillatory motion) to move the illumination beam Li with a motion law 0(t) along the surface of the retina.

[0145] According to the aforesaid second operating mode of the apparatus 500, the control arrangement 10, 50 commands each of the scanning mirrors 542, 543 to move the third light beam Li on the retina along a corresponding optical scanning direction X, Y according to a corresponding motion law that includes:

[0146] - a motion component calculated to compensate for a movement of said third light beam along the corresponding optical scanning direction X, Y upon the reflection of said third light beam L3 by said first scanning mirror 17;

[0147] - a motion component calculated to move the third light beam L3 according to a desired optical scanning trajectory.

[0148] Preferably, during optical scanning of the retina, the second mirror 542 moves the third light beam L3, along the second scanning direction Y, with a motion law My(t) that advantageously includes:

[0149] - a first motion component Myi(t, 0(t)) calculated to compensate for the movement of the third light beam L3, along the second scanning direction Y, caused by the reflection thereof on the first scanning mirror 17. If applied alone, this first motion component would make the illumination beam L3 stationary along the scanning direction Y;

[0150] - a second motion component My2(t) calculated to move the third light beam L3 according to a desired optical scanning trajectory.

[0151] In other words, the motion law My(t) can be expressed by the following relation:

[0152] My(t) = Myl(t, 0(t)) + My2(t) wherein Myi(t, 0(t)) is the first motion component of the third light beam L3 along the scanning direction Y, calculated as a function of the motion law 0(t) with which the aforesaid illumination beam moves along the scanning direction Y upon the reflection on the first scanning mirror 17, and My2(t) is the second motion component of the third light beam L3 along the scanning direction Y, calculated to move the aforesaid illumination beam according to a desired scanning trajectory.

[0153] Preferably, during optical scanning of the retina, the third scanning mirror 543 moves the first light beam L3, along the second scanning direction X, with a motion law Mx(t) that advantageously includes:

[0154] - a third motion component Mxi(t, 0(t)) calculated to compensate for the movement of the third light beam Ls, along the second scanning direction X, caused by the reflection thereof on the first scanning mirror 17. If applied alone, this first motion component would make the illumination beam Ls stationary along the scanning direction X;

[0155] - a fourth motion component Mx2(t) calculated to move the illumination beam Li according to a desired optical scanning trajectory.

[0156] In other words, the motion law c(7) can be expressed by the following relation:

[0157] Mx(t) = Mxi(t, 0(t)) + Mx2(t) wherein Mxi(t, 0(t)) is the third motion component of the third light beam Ls along the scanning direction X, calculated as a function of the motion law 0(t) with which the aforesaid illumination beam moves along the scanning direction X upon the reflection on the third scanning mirror 431, and Mx2(t) is the second motion component of the third light beam Ls along the scanning direction X, calculated to move the aforesaid illumination beam according to a desired scanning trajectory.

[0158] In the embodiment illustrated in Fig. 3, the axis of rotation of the first scanning mirror 17 is parallel to the axis of rotation of the second scanning mirror 542. Given that the latter moves the third light beam Ls along the optical scanning direction Y (according to the example illustrated), the scanning mirror 17 also moves the illumination beam Ls along the scanning direction Y. Upon the reflection on the first scanning mirror 17, the illumination beam 1.3 is thus substantially stationary along the scanning direction X. However, it could also move along this scanning direction if the axes of rotation are not perfectly parallel with one another, for example due to mechanical tolerances or construction defects.

[0159] According to the embodiment of Fig. 3, the motion law c(7) of the third scanning mirror 543 can be expressed by the following relation:

[0160] Mx(t) = Mx2(t).

[0161] In other words, the first scanning mirror 543 moves the third light beam L3, along the first scanning direction X, with a first motion law Mx(t) comprising only the fourth motion component MX2(t) calculated to move the aforesaid illumination beam according to a desired scanning trajectory.

[0162] Preferably, the control arrangement 10, 50 is configured to carry out an acquisition procedure 90 of an image Wf of the retina 101, when the apparatus 500 operates in the aforesaid second operating mode (Fig. 6).

[0163] This acquisition procedure allows a B-scan image of the retina to be obtained in which the speckle noise is eliminated or reduced to negligible levels.

[0164] The acquisition procedure 90 includes a step 90a in which the control arrangement 10, 50 commands the first scanning mirror 17 and the optical scanning assembly 540 to carry out a plurality TV >1 of optical scanning cycles of the retina 101 along a same scanning plane perpendicular to the surface of the retina.

[0165] During each optical scanning cycle, the scanning mirrors 17, 542, 543 project and move the third light beam Ls according to predefined motion laws. For example, in the embodiment of Fig. 3, in which the axis of rotation of the first scanning mirror 17 is parallel to the axis of rotation of the second scanning mirror 542, the first scanning mirror 17 can move the illumination beam Ls according to a sinusoidal motion law 0(l), the second scanning mirror 542 can move the illumination beam Li according to a motion law of the type My(t) = Myi(t, 0(t)) + My2(t) and the third scanning mirror 543 can move the illumination beam Ls according to a motion law of the fy^Q Mx(t)=MX2(t) .

[0166] The acquisition procedure 90 includes a step 90b in which the control arrangement 10, 50 acquires, for each optical scanning cycle, a first B-scan preliminary image Wrof the retina at the same scanning plane.

[0167] The control arrangement 10, 50 thus acquires a collection of first preliminary B-scan images Wr(r = 1, . . ., N) of the retina 101 referred to a same scanning plane P.

[0168] Each B-scan image Wris a two-dimensional image having the position of the third light beam Ls along a scanning direction (for example the scanning direction Y) on the abscissa and the position of the aforesaid illumination beam along the axial direction Z of incidence on the ordinate (Figs. 7-8).

[0169] The first B-scan images Wrof the retina acquired are characterized by a same speckle pattern, given that they all refer to a same useful acquisition field AZ = [OPD=0, OPD=OPDmax] on the ordinate (i.e., along the axial direction Z), of the order of magnitude of a few mm.

[0170] However, each first B-scan image Wrshows each physical feature Q of the retina in different positions along the axial direction Z (ordinate). Each B-scan image Wris in fact composed of a plurality M> 1 of A-scan images Wri, WrM of the retina.

[0171] Given that the length of the optical path 3 of the third light beam Ls varies according to variation function Z(t), over the course of the optical scan, each A-Scan image is referred to a different depth value along the axial direction Z of incidence of the third light beam Ls.

[0172] Therefore, each B-scan image resulting from the composition of the corresponding M A-Scan images acquired is affected by a distortion along the axial direction Z perpendicular to the surface of the retina (Fig. 7-8).

[0173] This distortion depends on the variation function Z(t) of the length optical path difference of the third light beam Ls. As illustrated above, it is known, can be calculated based on the motion law 0(t) or can be identified through a calibration procedure, using a specific measurement instrument.

[0174] The acquisition procedure 90 includes a step 90c in which the control arrangement 10, 50 obtains a second preliminary B-scan image Wp(p = 1, . .., N) of the retina from each first preliminary B-scan image Wr(r = 1, . . . , N) of the retina.

[0175] Each second B-scan image Wpof the retina is obtained by processing the corresponding first B- scan image Wrto realign the A-scan images Wri, WrM composing the aforesaid first preliminary B-scan image Wralong an axial direction Z perpendicular to the surface of the retina 101.

[0176] The realignment process of the A-scan images Wri, WrM is advantageously carried out based on the variation function Z(t) of the optical path difference of the third light beam Ls and hence on the (sinusoidal) motion law 0(t) with which the first optical scanning mirror 17 moves the illumination beam L3.

[0177] The realignment process of the A-scan images Wri, WrM can be carried out using suitable image processing algorithms, which can be of known type.

[0178] In practice, each A-scan image Wri, WrM is translated with a correction value along an axial direction Z perpendicular to the surface of the retina 100, extrapolated from a correction function, advantageously corresponding to the variation function Z(t) of the length of optical path.

[0179] The control unit 5 thus obtains a collection of second preliminary B-scan images Wp (p = 1, . . . , N) of the retina 100 referred to a same scanning plane P and without distortions along an axial direction perpendicular to the surface of the retina.

[0180] Each second B-scan image Wpthus shows each physical feature of the retina in a same position along the axial direction Z (ordinate). Each second B-scan image Wpis instead characterized by a speckle pattern modified with respect to the original speckle pattern of the corresponding first B-scan image Wrfrom which it was obtained.

[0181] The realignment process of the A-scan images Wri, WrM of each first B-scan image Wrdetermines a variation of the depth values along the axial direction Z to which the aforesaid A- scan images refer.

[0182] Therefore, the speckle pattern of each B-scan image Wpvaries time by time, being affected by a distortion along an axial direction Z perpendicular to the surface of the retina.

[0183] Therefore, the speckle pattern of various B-scan images Wpis not repeated, given that it depends substantially on the optical path difference (OPD) between the optical paths 3, 4 of the illumination beams L3, L4 along the interferometric arms 54, 56 of the detection unit 53.

[0184] Advantageously, the step 90c of the acquisition procedure 90 can be carried out in real time, simultaneously to the acquisition of each first B-scan image Wrof the retina, or during postprocessing, after the acquisition of the N first B-scan images Wrhas been completed.

[0185] The acquisition procedure 90 includes a step 90d in which the control arrangement 10, 50 obtains a final image Wf of the retina by processing a plurality of second B-scan images Wpof the retina obtained during the performance of successive optical scanning cycles.

[0186] The final image Wf of the retina can be a. B-scan image of the retina obtained through a image mediation process applied to a plurality of (not necessarily to all of the) second B-scan images Wpof the retina obtained in the previous step 90c of the acquisition procedure.

[0187] The mediation process of the second B-scan images Wpcan be carried out using appropriate image processing algorithms, which can be of known type.

[0188] The acquisition procedure 90 allows B-scan images of the retina to be obtained with a speckle noise that is substantially eliminated or reduced to negligible levels, given that the second B- scan images Wpare characterized by speckle patterns that differ from one another.

[0189] The acquisition procedure 90 also allows a considerable improvement in the signal / noise ratio of the B-scan images of the retina acquired through the mediation process performed on the second B-scan images.

[0190] The inspection apparatus of the ocular fundus 500, according to the invention, has numerous advantages with respect to the prior art.

[0191] The apparatus 500 includes two different arrangements of components 500a, 500b for the acquisition of images of the retina by LSO and OCT, respectively, which are combined with each other without the use of additional components (in particular dichroic mirrors or other similar optical components) to direct the various illumination beams of the retina along the corresponding optical paths.

[0192] From a viewpoint of image acquisition by LSO, the solution proposed by the present invention (arrangement of the scanning mirror 542 in the region 510 of the apparatus 500) does not influence the optical paths of the light beams Zy, L2 (illumination and acquisition beams). Therefore, it does not cause any reduction of the quality of the images of the retina acquired. From a viewpoint of image acquisition by OCT, the solution proposed by the present invention does not cause any alteration of the coherence of the illumination beam L3. Therefore, the occurrence of group delay dispersion (GDD) linked to the use of dichroic mirrors is avoided and an optimal axial resolution of the images acquired is guaranteed. The solution proposed by the invention instead allows an improvement of the quality of the images of the retina acquired. In the aforesaid second operating mode of the apparatus, it is possible to vary in a controlled manner the optical path difference of the illumination beam L3 along the interferometric arm of the second arrangement of components 500b. This allows the implementation of procedures for acquiring B-scan images of the retina capable of providing images of very high quality, characterized by a substantial absence of speckle noise.

[0193] The apparatus, according to the invention, is also characterized by a considerable operational flexibility.

[0194] The arrangements of components 500a, 500b can operate individually or simultaneously. The same second arrangement of components 500b can operate according to diversified operating modes, according to requirements.

[0195] The apparatus 500 can thus operate either as LSO ophthalmic machine, as combined ophthalmic machine, or as OCT ophthalmic machine.

[0196] The apparatus, according to the invention, is characterized by a very modular overall structure in which the various arrangements of components 500a, 500b can be easily combined with one another. For example, the second arrangement of components can be easily “added” to the first arrangement of components without having to take structural action thereon.

[0197] This modular structure allows considerable economies of scale to be obtained in the production of ophthalmic machines. In fact, it can be used to industrially produce a combined ophthalmic machine (LSO+OCT) or an LSO ophthalmic machine obtained as a design variant of the combined ophthalmic machine, in which the second arrangement of components 500b is simply not mounted. The apparatus according to the invention has a structure that is very compact and easy to assemble. Therefore, it is easy to manufacture on an industrial scale, with considerable advantages in terms of containment of production costs.

Claims

CLAIMS1. Inspection apparatus (500) of the ocular fundus comprising a first arrangement of components (500a) for acquiring images of the retina through line scanning, a second arrangement of components (500b) for acquiring images of the retina by optical coherence tomography and a control arrangement (10, 50) to control the operation of said first and second component arrangements, wherein said first arrangement of components (500a) comprises: a first illumination unit (11) for projecting a first light beam (Zy) to illuminate the retina (101) of an eye (100), said first illumination unit comprising at least a first light source (111); a first optical path (1) for said first light beam (Zy); a first image acquisition unit (27) for receiving a second light beam (Z2) including light reflected by the retina illuminated with said first light beam (Zy); a second optical path (2) for said second light beam (Z2) reflected by the retina and directed towards said first image acquisition unit (27); a first scanning mirror (17) for reflecting and directing said first light beam (Zy) towards the retina (101) along said first optical path (1), said first scanning mirror being configured to move said first light beam (Zy) along the surface of the retina; a light beam separator (16) to separate the second light beam (Z2) travelling along said second optical path (2) from the first light beam (Zy) travelling along said first optical path (1); wherein said second arrangement of components (500b) comprises: a second light source (52); an optical detection unit (53) comprising a measurement interferometric arm (54) and a reference interferometric arm (56), wherein said measuring interferometric arm (54) includes a third optical path (3) for a third light beam (LI) coming from said second light source (52) and directed towards the retina (101), wherein said measurement interferometer arm (54) comprises a scanning assembly (540) including one or more scanning mirrors (542, 543) for reflecting and directing said third light beam (Li) along said third optical path (3), said one or more scanning mirrors being configured to move said third light beam (Li) on the retina (101); a second image acquisition unit (58) for receiving an interferometric optical signal (II) generated by optical interference between a measurement light radiation LM)provided at the output from said measurement interferometry arm (54) and a light radiation reference (LR) supplied at the output from said reference interferometric arm (56); characterized in that said scanning assembly (540) includes a second scanning mirror(542) arranged in a region (510) of said apparatus between said first scanning mirror (17) and said light beam separator (16), wherein said second arrangement of components (500b) includes also said first scanning mirror (17) to reflect and direct said third light beam (Li) towards the retina (101) along said third optical path (3).

2. Apparatus, according to claim 1, characterized in that, in operation, said second scanning mirror reflects and directs said third light beam (Li) towards said first scanning mirror (17) along a portion (3a) of said third optical path (3) in an intermediate position between the first optical path (1) of said first light beam (Li) and the second optical path (2) of said second light beam (Li).

3. Apparatus, according to one of the previous claims, characterized in that the axis of rotation of said first scanning mirror (17) is parallel to the axis of rotation of said second scanning mirror (542).

4. Apparatus, according to one of the previous claims, characterized in that said scanning assembly (540) includes said second scanning mirror (542) and a third scanning mirror(543), in which said second and third scanning mirrors are positioned respectively in a proximal and distal position with respect to said first scanning mirror (17), along the third optical path (3) of said third light beam (Li).

5. Apparatus, according to claim 4, characterized in that the second scanning mirror (542) and the third scanning mirror (543) have rotation axes perpendicular to each other.

6. Apparatus, according to one of the previous claims, characterized in that, in a first operating mode of said apparatus, said control arrangement (10, 50) commands said first scanning mirror (17) to remain fixed in a predefined position and commands each of the scanning mirrors (542, 543) of said scanning group (540) to move said third light beam (Li) on the retina (101), along a respective optical scanning direction, with a corresponding motion law calculated to move said third light beam (Li) according to a desired optical scanning trajectory.

7. Apparatus, according to one of the previous claims, characterized in that, in a second operating mode of said apparatus, said control arrangement (10, 50) commands said first scanning mirror (17) to move said third light beam (Li) on the retina (101) with apredefined motion law and commands each of the scanning mirrors (542, 543) of said scanning group (540) to move said third light beam (Li) on the retina (101), along a respective optical scanning direction (X, Y) with a corresponding motion law which includes: a motion component calculated to compensate for a movement of said third light beam (Li) along the respective optical scanning direction upon the reflection of said third light beam by said first scanning mirror (17); a motion component calculated to move said third light beam (Li) according to a desired optical scanning trajectory.

8. Apparatus, according to claim 7, characterized in that, in said second operating mode of said apparatus, said control arrangement (10, 50) carries out an acquisition procedure (90) of an image (Wf) of the retina (101), which includes the following steps: commanding (90a) the first scanning mirror (17) and said scanning group (540) to perform a plurality of optical scanning cycles of the retina along a same scanning plane (P) of the retina; for each optical scanning cycle, acquiring (90b) a first B-Scan image ( Pr) of the retina in correspondence with said scanning plane (P), each first B-Scan image (PP7) acquired being composed of a plurality of A-Scan images (Wri, WriL) of the retina; obtaining (90c) a second B-Scan image (Wp) of the retina from each first B-Scan image (PP ) of the retina, each second B-Scan image (Wp) of the retina being obtained by processing said first B- Scan image (Wr) in order to realign the A-scan images Wri, ...,WTM) composing said first B-Scan image (Wr) along an axial direction (Z) perpendicular to the surface of the retina (101); obtaining (1 Od) said image (Wf) of the retina based on a plurality of second B-Scan images (Wp) of the retina.

9. Apparatus, according to claim 8, characterized in that said image ( f) of the retina is a B- Scan image of the retina obtained by processing a plurality of second B-Scan images (Wp) of the retina through an image mediation process.

Images