WO2016181068A1

WO2016181068A1 - Optical system for the acquisition of information about a surface

Info

Publication number: WO2016181068A1
Application number: PCT/FR2016/051100
Authority: WO
Inventors: Sylvaine Picard; Yann LE GUILLOUX
Original assignee: Safran
Priority date: 2015-05-12
Filing date: 2016-05-11
Publication date: 2016-11-17
Also published as: FR3036246B1; FR3036246A1

Abstract

The invention relates to an optical system (1) for the acquisition of information about a surface (4), comprising: a plenoptic lighting device (20) designed to illuminate the surface to be acquired (4); an imaging device (30) designed to acquire an image of the surface to be acquired (4); a matrix mask (7) comprising a matrix (71) of cells that can be controlled independently of each other in order to transmit a selected quantity of light; and a control device (9) designed to limit the quantity of light transmitted by a cell (71) when the light transmitted through said cell (71) generates, following reflection on the surface to be acquired (4), a specular reflection in the field angle of the imaging device (30).

Description

Optical system for acquiring information on a surface

FIELD OF THE INVENTION The present invention relates to the optical acquisition of information on a surface, and in particular the optical three-dimensional (3D) metrological acquisition of a surface. Optical 3D metrological acquisition consists in obtaining the coordinates of the points constituting the surface of a part, by sending a luminous radiation on the surface of the part and by measuring the radiation reflected by the surface of the part. The present invention can of course be used to acquire all kinds of information on a surface, such as, for example, the demonstration of a particular surface condition (corrugations, scratches) on a non-planar surface.

The present invention relates in particular to the acquisition of information on a non-Lambertian surface, that is to say that can present specular reflections. A non-Lambertian surface is characterized by a specular component, the specular component being the preferred reflection direction or directions, and a Lambertian component, the Lambertian component being the Lambert-law component, that is, having a equal luminance in all directions.

STATE OF THE ART

Optical acquisition systems are known, in particular of 3D optical metrological acquisition, such as that illustrated in FIG. 1, comprising a light source 2 which illuminates the surface to be acquired 4 and an imaging sensor 3 which acquires the light reflected by the surface 4.

The optical acquisition system determines, from the image acquired by the imaging sensor 3, information on the surface by known techniques such as triangulation scanner, phase shift scanner, light scanner. structured, or modulated light scanner. Optical acquisition systems of the prior art do not make it possible to satisfactorily acquire the non-Lambertian surfaces because it is very probable that there are points such as the specular reflection of the surface or in the angle of camera field, which leads to a saturation of the imaging sensor in the preferred reflection directions.

As shown in FIG. 1, there are specular reflections at the points P, Q and S, and the direction of the specular reflection at the point P is included in the field of view of the camera, which results in a saturation of the Imaging sensor at the point P image.

In the case of a piece of complex shape such as a turbomachine blade, this problematic configuration is very likely. However, these saturations prevent a satisfactory acquisition in the areas concerned, because the saturation causes the loss of information.

To overcome this problem, several solutions have been proposed.

It has been proposed to use a surface matification with the aid of a powder. This solution is very effective but expensive because it entails additional operations. In addition it causes a loss of accuracy of the measurement because the powder adds a poorly known thickness.

Another solution, proposed by Nayar and Gupta in "Diffuse structured light in IEEE International Conference on Computational Photography", 2012 and illustrated in Figure 2, is to add an optical diffuser 5 to limit the effect of specularities. Thus, each point of the surface is illuminated in several directions which allows not to illuminate the surface at a single angle but a plurality of angles. This makes it possible to limit the intensity of the specularities because the energy sent towards the surface in each direction is limited. However, the effect of specular reflection is only diminished in this case, since the piece is always illuminated along the direction causing specular reflection in the direction of the camera. Another disadvantage of this system is that the diffuser 5 prohibits the modification of the projected pattern. It can only be a band pattern whose orientation is compatible with the direction of diffusion. Another disadvantage of this system is that it can not adapt in real time. Another solution is to illuminate the room by one point and to observe this point with two cameras. In this case at least one of the cameras is not dazzled. The disadvantage of this solution is that it is punctual and does not allow rapid acquisition of an entire surface, moreover it requires the use of two cameras.

SUMMARY OF THE INVENTION

An object of the invention is to provide an optical system for acquiring information on a surface that makes it possible to totally eliminate specular reflections towards the camera and adaptable in real time. Adaptable means that the projected light can be changed at any time, locally or globally.

This object is achieved in the context of the present invention by virtue of an optical system for acquiring information on a surface comprising:

a lighting device configured to illuminate the surface to be acquired,

one or more imaging devices, each having a field angle, configured to acquire an image of the surface to be acquired, the acquisition system being characterized in that the lighting device is a configured plenoptic lighting device for illuminating each point of the surface according to at least two different angles of incidence, and further comprising:

a matrix mask positioned between the lighting device and the surface to be acquired and comprising a matrix of cells that can be controlled independently of each other to transmit a chosen quantity of light, and

a control device configured to limit the amount of light transmitted by a cell when the light transmitted through said cell generates, after reflection on the surface to be acquired, a specular reflection in the field of view of one of the devices; imaging. The invention makes it possible to control the luminous intensity at any point of the illuminated surface and for each incidence.

Once the intensity distribution is defined, it is still possible to project different patterns on the surface while respecting this distribution of incidences.

The invention makes it possible in particular to produce a plurality of textured lights on the surface to be acquired without creating specularities in the images acquired.

The invention further allows, when one is aware of a prior model of the observed surface, to detect shape defects even for complex 3D shapes.

The invention notably makes it possible to perform a stereo algorithm reconstruction for non-Lambertian (and complex) surfaces.

The invention is advantageously completed by the following characteristics, taken individually or in any of their technically possible combinations:

the plenoptic lighting device comprises a light source and a microlens array comprising a plurality of microlenses all having the same image focal plane;

the matrix mask is positioned between the microlens array and the image focal plane of the microlenses;

the microlenses are divergent;

the microlenses are convergent;

the plenoptic lighting device comprises a light source and a panel of opaque material in which is formed a matrix of holes, the source illuminating the panel at a plurality of angles of incidence;

the plenoptic lighting device comprises a plurality of light sources arranged in the same plane;

the matrix mask is an LCD screen, the cells being LCD cells; the matrix mask is a matrix of orientable mirrors, the cells being orientable mirrors;

each cell can be controlled to be in an on state, in which it transmits all the light, or in a blocking state, in which it transmits no light,

each cell can be controlled to be in an intermediate state, in which it lets a certain quantity of light pass;

each cell being controllable to be alternately in an on or off state, the controller is configured to control the alternation of the passing and blocking states of the cell so as to control the amount of light transmitted through the cell during a period of time. integration time;

an optical separation device is positioned in such a way that the light coming from the source is transmitted to the surface to be analyzed through the optical separation device, the light coming from the reflection on the surface being reflected by the separation device optical to the imaging device;

the imaging device is a plenoptic sensor.

The invention also proposes a method for acquiring information on a surface implemented by an acquisition optical system according to one of the preceding claims, consisting of:

illuminate the surface to be acquired with a plenoptic lighting device so as to illuminate each point of the surface in at least two different angles of incidence,

- acquire an image of the surface to be acquired,

- observe any specular reflection in the direction of the field of view of the imaging device,

- limit the amount of light transmitted by the matrix mask cells through which light is transmitted or reflected generating, after reflection on the surface to be acquired, the specular reflection observed.

The invention also proposes the use of an optical acquisition system as characterized above, for the metrological control of a turbomachine blade.

DESCRIPTION OF THE FIGURES Other objectives, features and advantages will become apparent from the detailed description which follows with reference to the drawings given by way of non-limiting illustration, among which:

FIG. 1, discussed above, illustrates an optical acquisition system of the prior art,

FIG. 2, discussed above, illustrates an optical acquisition system equipped with an optical diffuser as proposed in the prior art,

FIG. 3a illustrates an optical acquisition system according to a first embodiment of the invention,

FIG. 3b illustrates an optical acquisition system according to an alternative embodiment of the invention,

FIG. 4a illustrates an optical acquisition system according to a second embodiment of the invention,

FIG. 4b illustrates an optical acquisition system according to an alternative embodiment of the invention,

FIG. 5 illustrates an optical acquisition system comprising two imaging devices according to an embodiment of the invention,

FIG. 6 illustrates an optical acquisition system in which the matrix mask is a DLP matrix,

FIG. 7 illustrates an optical acquisition system according to an alternative embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

As illustrated in FIGS. 3a to 7, an optical acquisition system 1 of a surface 4 comprises a lighting device 20, and one or more imaging devices 30, a matrix mask 7, and a control system of the matrix mask 9.

The lighting device 20 is a plenoptic lighting device configured to illuminate each point of the surface 4 according to at least two different angles of incidence, and a matrix mask 7 adapted to shut off or deflect some beams selectively from the surface.

For this purpose, the plenoptic lighting device 20 comprises, in some embodiments, a light source 21, and a matrix 6 of microlenses.

In some embodiments, the light source 21 is collimated with a collimator 25 placed between the light source 21 and the matrix 6 of microlenses.

The light source 21 may also be a flat electroluminescent film or a plurality of light emitting diodes (LEDs) optionally associated with an optical diffuser.

As illustrated in Figures 3a and 4a, the matrix 6 of microlenses consists of a set of microlenses 61 located in the same plane. The microlenses 61 may in particular be arranged in rows and columns or staggered.

The microlenses 61 all have the same focal length and their focal planes F 'are merged.

Each microlens 61 transmits an incident beam on the surface 4 with one or more angle (s) of incidence. For a given point of the surface 4, the angle of incidence angle (s) on said point of the beam transmitted by a lens 61 is different from the angle interval (s) of incidence on said point of the beam transmitted by the other microlenses 61. Thus, each point is illuminated by several beams with different angles of incidence. If a point of the surface is in the image focal plane of the lighting device, it is illuminated by several beams coming from the same lens 61 having different angles of incidence (except, of course, by the beams occulted by the mask 7). Otherwise, it is illuminated by several beams having different angles of incidence from different lenses 61.

In other words, the matrix 6 of microlenses 61 transforms the light source 21 into a plurality of secondary light sources positioned at the focal point of each microlens 61. Thus, each microlens 61 transforms the light emitted by the light source 21 into a secondary light source which illuminates the surface to be analyzed 4 according to a particular set of angles. In this way, each point of the surface 4 is illuminated according to several different angles of incidence. Preferably, each secondary light source illuminates the entire surface 4.

In a first embodiment illustrated in FIG. 3a, the microlenses

61 are convergent and the lighting device 20 further comprises a main lens 8. The focal image plane F 'of the microlenses 61 is between the matrix 6 of microlenses 61 and the main lens 8.

The main lens 8 is a converging lens.

The matrix mask 7 is positioned between the microlens matrix 6 and the main lens 8, and more precisely between the microlens matrix 6 and the image focal plane F 'of the microlenses 61.

Alternatively, the matrix mask 7 may be placed between the light source 21 and the microlenses 61.

This first embodiment corresponds to the optical assembly of a plenoptic camera, the path of the light however being reversed compared to that of a plenoptic camera. Whereas a conventional photographic camera records at each point the accumulated energy of all the rays converging on the sensitive surface, a plenoptic camera records separately the energies of the rays according to their direction of propagation. In this first embodiment, the matrix 6 of microlenses 61 focuses the light of the source 21 into a plurality of image focal points f, all arranged in the same focal plane plane F '.

The spacing between the microlenses 61 is typically of the order of 0.3mm. The number of microlenses 61 is typically of the order of 60 in one direction. The height of the network 6 of microlenses is then of the order of 20mm. The focal length of the microlenses is typically 0.6mm. The focal length of the main lens is typically 40mm. The distance between the microlens matrix 6 and the main lens 8 is 40 mm. The distance between the main lens 8 and the surface is of the order of 50mm.

To optimize the spatial resolution of the illuminated points on the surface 4, it is necessary to choose microlenses 61 with the smallest possible diameter or to reduce the magnification of the main lens. To maximize the angular resolution of the rays illuminating a point on the surface 4, the microlenses of a relatively large diameter must be spaced apart. In this first embodiment, the spacing of the microlenses is a determining factor for the characteristics of the system.

In a second embodiment, illustrated in FIG. 4a, the microlenses 61 are divergent. The focal plane image F 'of the microlenses 61 is between the matrix 6 of microlenses and the light source 21.

The matrix mask 7 is positioned between the microlens matrix 6 and the light source 21, and more precisely between the microlens matrix 6 and the image focal plane F 'of the microlenses 61. The distance between the microlens matrix 6 and the surface 4 is typically of the order of a few tens of centimeters.

In an alternative embodiment, illustrated in FIGS. 3b and 4b, the matrix 6 of microlenses is replaced by a panel 11 in which circular holes 11 are formed. The diameter of these circular holes 11 is small compared to the size of the elements of the mask 7 but much greater than the wavelength. The light source 21 sends light to each hole 1 1 1 at a plurality of angles of incidence. Each troul 1 1 then behaves as a secondary source. In a fourth embodiment, not shown because close in principle of the third mode, point sources 21 and matrix masks 7 are point sources 21 and matrix masks 7 of a plurality of video projectors. In this case the working volume of the plenoptic lighting may exceed the m ³ and the working distance may exceed the m.

The matrix mask 7 comprises a matrix of cells 71 that can be controlled independently of each other to transmit a chosen amount of light.

Each cell 71 may be either in an on state, in which it transmits the light passing through it, or in a blocking state, in which it obstructs the light, as in the case of an LCD screen, or deflects it out of the surface 4, as in the case of a DLP matrix. A modulation of the amount of light emitted through each cell 71 is controllable either by varying the degree of opacity of the cells 71 or by temporal modulation. Indeed, each cell 71 can change state several thousand times per second. The imaging device 30 integrates the pulses during the exposure time and thus perceives the average light level. The gray level detected by the imaging device 30 is therefore directly proportional to the time during which the cell 71 is in the passing position over time.

In an alternative embodiment, each microlens 61 corresponds to a cell 71.

In another embodiment, the beam from each microlens 61 is transmitted through a set of neighboring cells 71. .

In particular, each microlens 61 may correspond to a square of cells 71, typically composed of 4, 9, or 16 cells 71,

The matrix mask 7 may in particular be a liquid crystal screen 7 subsequently called an LCD screen, consisting of a grid of liquid crystal cells (LCD), each cell 71 being either transparent (on-state) or opaque (state blocking), depending on the state of the liquid crystal of this pixel. An LCD cell 71 consists, in known manner, of a thin layer of liquid crystal, enclosed between two transparent plates equipped with polarizers, and subjected to a variable electric field. The state of each liquid crystal cell 71 is controlled, in a known manner, by applying between transparent electrodes distributed in matrix opposite the two transparent plates a bias voltage evolving between two levels: a low level at which the cell LCD 71 is transparent (on state) and a high level at which the LCD cell 71 is opaque (blocking state).

The matrix mask 7 may also be a DLP (for "Digital Light Processor") matrix consisting of a matrix of moving mirrors, each cell 71 of the mask being a moving mirror. The state of each cell 71 is controlled, in known manner, by orienting the moving mirror so that it reflects light to the surface 4, the cell is then in the on state, or so that that it reflects this light towards a surface that absorbs the rays, the cell is then in the blocking state. This produces the projection of a lit point, or a point off. In the case where the matrix mask 7 is a DLP matrix, the matrix mask 7 and the light source 21 are positioned relative to the surface 4 so that the cells 71 in the blocking state do not reflect the light on the screen. surface 4, while the cells 71 in the on state reflect the light on the surface 4, as shown in FIG. 6.

By modulating the state of the cells 71, the matrix mask 7 makes it possible to control at each point of the surface 4, the intensity of each ray illuminating this point.

As explained above, only certain angles of incidence of the illumination create, after reflection, specularities causing the saturation of the photometric information in the image.

If one or more of the rays incident on the surface 4 generate a specular reflection included in the field angle of the imaging device 30, the control system 9 controls the blocking state of the cell or cells 71 through which the radiation generating specular reflection passes. As illustrated in FIGS. 3a to 7, the optical acquisition system 1 comprises one or more imaging devices 30. Each imaging device 30 comprises a photographic sensor 31 and a focusing optic 32. In addition, the imaging system 30 comprises Optical acquisition may include other optical elements, such as mirrors, so as to create folds of the optical paths. The photographic photographic sensor 31 is a photosensitive electronic component adapted to convert the electromagnetic radiation (UV, visible or IR) into an analog electrical signal. This signal is then amplified and digitized by an analog-to-digital converter to obtain a digital image. The focusing optics 32 is conventionally an optical lens or a combination of optical lenses. The imaging device 30 is for example a camera. The angle of view of the imaging device 30 is the angle that the imaging device 30 will be able to capture.

In the case where the imaging system 30 has N imaging devices 30, to always be able to eliminate all specular reflections while illuminating the entire surface 4 in the images of all the imaging devices 30, it is necessary that each point the surface 4 is illuminated according to at least N + 1 different angles of incidence.

The imaging device 30 is arranged with respect to the surface 4 and the lighting device 20, so as to capture a significant part of the light reflected on the surface to be analyzed 4.

As illustrated in FIGS. 3a to 6b, the imaging device 30 can be arranged to capture the light directly after reflection on the surface to be analyzed 4, as illustrated in FIG. 1. For this purpose, the optical axis of the imaging device 30 is oriented towards the surface to be analyzed 4.

As illustrated in FIG. 7, the acquisition system 1 may also comprise an optical separation device 10, such as a semi-reflecting plate, positioned between the source 21 and the surface 4. The light coming from the source 21 is transmitted to the surface to be analyzed 4 through the optical separation device 10. The light resulting from the reflection on the surface 4 is reflected by the optical separation device 10 to the imaging device 30. In this case, the optical of Focus 32 of the imaging device 30 is a set of microlenses, the imaging device 30 being a plenoptic imaging sensor.

In the first embodiment according to FIG. 7, the optical separation device 10 is positioned between the main lens 8 and the microlens matrix 6. The light from the microlens array 6 is transmitted to the main lens 8 and the surface to be analyzed 4 through the optical separation device 10. The light resulting from the reflection on the surface 4 is transmitted by the main lens 8 and then reflected by the optical separation device 10 to the imaging device 30.

In an application to the second embodiment, the optical separation device is positioned between the microlens matrix 6 and the surface 4.

The light from the source 21 is transmitted to the surface to be analyzed 4 through the optical separation device 10.

In an application in the third embodiment, the optical separation device is positioned between the sources 21 and the surface 4. The light from the sources 21 is transmitted to the surface to be analyzed 4 through the semi-reflective plate.

The reflecting face is oriented with respect to the surface 4 so that, after reflection, the light reflected on the surface 4 is transmitted to the imaging device 30, (passing through the main lens 8 in the case of the first embodiment).

Alternatively, the reflecting face is oriented with respect to the surface 4 so that the light coming from the source 21 is reflected on the reflecting face towards the surface to be analyzed 4, and so that the light reflected on the surface 4 is transmitted to the imaging device 30 through the semi-reflecting plate 10.

The controller 9 can be operated using various methods.

In the general case, the different optical paths followed by the light depend on the configuration of the lighting device and the device (s) of acquisition but also on the surface 4 which is unknown. In this case, to determine the cells 71 of the mask which must be in the blocking state, it is possible to proceed by trial / error. For this purpose, successively controls the passing state of each of the cells 71 of the mask, one by one. When specular reflection is detected by the imaging device 30, i.e., when the camera detects radiation above a predefined threshold, the controller 9 records in a database that the cell 71 question must be put in the blocking state. Specular reflection can also be detected by an observer and not detected automatically by the camera. In this case, it will be understood that "detect" means "observe".

In the case where a priori model of the surface 4 is known, it is possible to calibrate the control device 9 taking into account the knowledge a priori of the shape of the surface 4. For this purpose, it is estimated (or known) the position of the surface with respect to the lighting device 20 as well as with respect to the imaging system, then the incident rays which are not to lead to specularities and those which must lead to specularities by modeling the propagation of the rays are determined; , and we deduce the cells 71 through which these rays pass. By switching on and off the beam-transmitting cells 71 to specularities and those not leading to specularities, it is possible to check whether the specularities appear according to the prediction made by modeling. If this is not the case, then we must conclude that the surface 4 does not conform to the predicted model. In this case, a defect in the shape of the surface has been detected. The novelty brought by plenoptic lighting is that this operation can be performed on surfaces of complex 3D shape.

In the case illustrated in FIG. 7, where the acquisition system 1 comprises an optical separation device 10 placed between the source 21 and the surface 4 so that the light after reflection on the surface 4 is transmitted towards the device 30, the direction of the rays to be extinguished can be deduced directly from the image of the imaging device 30 because there is a fixed geometrical correspondence between the optical paths of the imaging channels and those of the lighting channels (see FIG. Fig. 6). In this variant embodiment, the correspondence between the optical path of the light coming from the lighting device and that of the light reaching the imaging device 30 does not depend on the surface 4, and the control device 9 can be calibrated a priori so as to associate each pixel of the image on the imaging device 30 with a cell 71 of the mask 7 In this case, the calibration of the control device 9 consists of associating with each pixel of the image on the imaging device 30, the cell or cells 71 of the mask 7 which transmit the light incident on said pixel. Calibration of the control device 9 makes it easy to determine which cell (s) 71 of the mask 7 must be closed (s) to suppress annoying specular reflection. This variant embodiment makes it possible on the one hand to reduce the size of the device and, on the other hand, to simplify the control device 9.

It should be noted that it is possible to project a pattern on the surface 4 by selectively closing certain cells 71 of the mask, while taking into account the cells 71 which must be closed to suppress the specular reflections. This may be useful especially when the optical acquisition device 30 is a structured light 3D scanner projecting a bright pattern on the surface. The pattern can be one or two dimensional. The imaging device is a camera that records any deformation of the pattern. A calculator calculates, in known manner, the distances of the points making up this pattern.

This may also be useful when the optical acquisition device 30 is a stereo imaging device having a plurality of cameras. The projected pattern (s) may be, for example, random patterns generated so as not to create specularities. The analysis of the images taken by each of the cameras of the optical acquisition device 30 makes it possible to associate with each pixel of a camera the pixel of the other corresponding camera. The mask 7 is controlled to remove all lambertian components of the light reflected by the surface. Thus, no camera is affected by specular reflection, and the cameras record only the lambertian component of the light reflected by the surface. Thus, the light energy received by the different cameras is the same and the images of the pixels can therefore be matched in a conventional manner (by correlation of the neighborhood of the pixels or by observation of a unique signature at each pixel). It should be noted that it is possible to modulate the light sent on the surface 4 by modulating the state of the cells 71 of the mask, while taking into account the cells 71 which must be closed in order to suppress the specular reflections. This can be useful especially when the optical acquisition device is a 3D modulated light scanner illuminating the subject with a changing light.

Claims

1. An optical information acquisition system (1) on a surface (4) comprising:

a lighting device (20) configured to illuminate the surface to be acquired (4),

one or more imaging devices (30), each having a field angle, configured to acquire an image of the surface to be acquired (4),

the acquisition system (1) being characterized in that the lighting device (20) is a plenoptic lighting device configured to illuminate each point of the surface (4) at at least two different angles of incidence, the plenoptic illuminator (20) having a light source (21) and a microlens array (6) comprising a plurality of microlenses (61) all having the same image focal plane (F ')

and further comprising:

a matrix mask (7) positioned between the lighting device (20) and the surface to be acquired (4) and comprising a matrix of cells (71) which can be controlled independently of each other to transmit a chosen quantity of light, and

a control device (9) configured to limit the amount of light transmitted by one or more cells (71) when the light transmitted through said cells (71) generates, after reflection on the surface to be acquired (4), a reflection specular in the field of view of one of the imaging devices (30).

2. Optical system (1) according to the preceding claim, the matrix mask (7) being positioned between the array (6) of microlenses and the image focal plane (F ') microlenses (61).

Optical system (1) according to one of the preceding claims, the microlenses (61) being divergent.

Optical system (1) according to one of the preceding claims, the microlenses (61) being convergent.

Optical system (1) according to one of the preceding claims, the plenoptic lighting device (20) comprising a plurality of elementary light sources (210) forming the source (21) arranged in the same plane facing the microlens array ( 6).

Optical acquisition system (1) according to one of the preceding claims, the matrix mask (7) being an LCD screen (7), the cells (71) being LCD cells.

Optical acquisition system (1) according to one of the preceding claims, the matrix mask (7) being a matrix of steerable mirrors, the cells (71) being orientable mirrors.

Optical acquisition system (1) according to one of the preceding claims, wherein each cell (71) can be controlled to be in an on state, in which it transmits all the light, or in a blocking state, in which it does not transmits no light.

Optical acquisition system (1) according to one of the preceding claims, wherein each cell (71) can be controlled to be alternately in an on or off state, the control device (9) being configured to control the alternation of states passing and blocking the cell (71) to control the amount of light transmitted through the cell (71) during an integration time.

10. Optical acquisition system (1) according to one of the preceding claims, comprising an optical separation device (10) positioned so that the light from the source (21) is transmitted to the surface to be analyzed ( 4) through the optical separation device (10), the light from the reflection on the surface (4) being reflected by the optical separation device (10) to the imaging device (30).

1 1. Optical acquisition system (1) according to one of the preceding claims, the imaging device (30) being a plenoptic sensor.

12. A method of acquiring information on a surface (4) implemented by an optical acquisition system (1) according to one of the preceding claims, consisting of:

illuminating the surface to be acquired (4) with a plenoptic lighting device so as to illuminate each point of the surface (4) according to at least two different angles of incidence,

acquiring at least one image of the surface to be acquired (4),

detecting specular reflection in the field of view of the imaging device (30),

- Limit the amount of light transmitted by the cells (71) of the matrix mask (7) through which is transmitted the light generating, after reflection on the surface to be acquired (4), the specular reflection detected.

13. Use of an optical acquisition system (1) according to one of claims 1 to 1 1, for three-dimensional metrological control of a turbine engine blade.