Device used in a lensless imaging system and lensless imaging system incorporating the device

Abstract

The invention relates to a device used in a lensless imaging system, said device comprising: An image sensor (C) defining a capture surface, Arranged outside the capture surface of the image sensor (C), a mechanical holding assembly (10) intended to hold a container (2) for storing and observing a sample, said mechanical holding assembly (10) being configured to define an observation window (Z2), Means for rotating said mechanical holding assembly (10) about an axis of rotation (A1) perpendicular to the capture surface, so as to be able to rotate the storage and observation container (2) about itself when it is held by the mechanical holding assembly (10), Control means (4) being configured to control said image sensor (4) so ​​as to acquire several successive images, during the rotation of said mechanical holding assembly (10).Figure to be published with the abbreviation: Figure 4.

Description

Title of the invention: Device used in a lensless imaging system and lensless imaging system incorporating the device. Technical field of the invention

[0001] The present invention relates to a device used in a lensless imaging system and to the lensless imaging system incorporating said device. State of the art

[0002] In the field of lensless imaging, a small image sensor with a capture area of ​​only a few mm² is frequently used. This area is often much smaller than the area to be imaged. To image the entire area, it is therefore necessary to acquire several images and reconstruct the different images using processing methods.

[0003] Furthermore, the shape of the area to be imaged and that of the capture surface are often incompatible. For example, Petri dishes with a disk-shaped area to be observed are often used, while the sensor often has a rectangular capture surface. It is therefore not easy to image the entire area with a single image.

[0004] The object of the invention is to propose a device intended to be used in a lensless imaging system, which can manage the two constraints described above. Description of the invention

[0005] This objective is achieved by a device used in a lensless imaging system, said device comprising: - An image sensor defining a capture area, - Arranged outside the image sensor capture surface, a mechanical holding assembly intended to hold a container for storing and observing a sample, said mechanical holding assembly being configured to define an observation window surrounding the image sensor capture surface, - Means for rotating said mechanical holding assembly around an axis of rotation perpendicular to the capture surface, so as to be able to rotate the storage and observation container on itself when it is held by the mechanical holding assembly, - Means for controlling said image sensor and said rotational drive means, - The control means being configured to command said image sensor so as to acquire several successive images, during the rotation of said mechanical holding assembly.

[0006] According to one particular feature, the control means are configured to acquire images at a suitable acquisition frequency so that two consecutive images have an overlap area.

[0007] According to another feature, the control means are configured to control the rotating drive means continuously.

[0008] According to another feature, the control means are configured to control the rotational drive means by applying several successive rotational steps, and, at each rotational step, the control means are configured to control the image sensor for image acquisition.

[0009] According to another feature, the image sensor capture surface is rectangular in shape.

[0010] According to another feature, the observation window is disc-shaped.

[0011] According to another feature, the image sensor is positioned so that the axis of longitudinal symmetry is aligned along a diametrical plane of the observation window.

[0012] According to another feature, the device comprises a closed housing made of an opaque material, having a bottom wall integrating the image sensor and defining an internal volume of a suitable size to receive the mechanical support assembly and to place the storage and observation container therein, said housing having an opening made along an axis perpendicular to the capture surface.

[0013] According to another feature, the rotation drive means comprise a motor whose shaft engages with a toothed wheel of the mechanical holding assembly.

[0014] According to another feature, the mechanical retaining assembly comprises at least two interlocking spiral-shaped strips.

[0015] According to another feature, the two slats each hook at one end onto said toothed wheel.

[0016] The invention relates to a lensless imaging system comprising a controlled light source to emit a light signal and processing means, the system comprising a device as defined above, the light source being arranged to emit its light signal through the observation window, the processing means being configured to reconstruct a single image from the set of images captured by the image sensor during the rotation of the mechanical holding assembly.

[0017] The invention also relates to a method for imaging, without a lens, an area to be observed in a container, implemented using the system defined above, the method comprising the following steps: - Position the container in the mechanical holding assembly; - Control the light source and the means of rotational drive; - Control the image sensor to acquire several successive images of the area to observe when rotating the container on itself; - Reconstruct a single image from all the images acquired using the image sensor; Brief description of the figures

[0018] Other features and advantages will become apparent in the detailed description that follows, given in relation to the accompanying drawings in which: - Fig. 1 shows the superposition of a Petri dish and a rectangular image sensor; - Fig. 2 shows a top view of the mechanical holding assembly used in the invention; - Fig. 3 shows a top view of the mechanical support assembly in which a Petri dish is integrated and illustrates the operating principle of the device of the invention; - Fig. 4 schematically represents the imaging system according to the invention, in which a Petri dish is placed; - Fig. 5 illustrates the operating principle of the device of the invention;

[0019] Detailed description of at least one embodiment

[0020] For the remainder of the description, we define an orthonormal frame X, Y, Z. X and Y are the two dimensions of the horizontal plane and Z the vertical direction.

[0021] The terms "on", "under", "above" and "below", "superior" and "inferior" are to be considered taking into account the vertical Z direction.

[0022] As is known, with reference to [Fig. 4], a lensless imaging system comprises a controlled light source S that emits a light signal through an area to be observed. In one embodiment, the light source S is chosen, for example, to illuminate at a wavelength of 940 nm and at a distance of 10 cm from the area to be observed. Of course, these parameters can be adapted to the specific case.

[0023] The system also includes an image sensor C, the area ZI to be observed being positioned on said sensor C, between the light source and the image sensor.

[0024] Image sensor C is, for example, a conventional 24x36mm type digital sensor.

[0025] The system of the invention has the particularity of comprising a specific device 1 adapted for taking images of the ZI zone to be observed.

[0026] The device 1 is intended to facilitate the capture of images of the ZI zone to be observed, this ZI zone to be observed being for example defined by the surface of the bottom wall of a container 2 for storing a sample and observing this sample.

[0027] In the context of the invention, this container 2 is, for example, a Petri dish. A Petri dish is known to be a transparent-walled container (glass or other PMMA-type material) with a circular cross-section and therefore has a bottom wall forming the disc-shaped area ZI to be observed. It is intended to contain the sample to be observed / analyzed. It typically has a diameter of several centimeters. It should be noted that the invention is applicable to any container with a closed cross-section, whether rectangular, square, or otherwise.

[0028] The device therefore mainly comprises the image sensor C defining a capture surface. The capture surface is conventionally rectangular in shape.

[0029] Fig. 1 shows the superposition of the bottom wall (Zl zone) of a Petri dish on a rectangular image sensor C.

[0030] The device also includes a mechanical holding assembly 10 for holding the storage and observation container, said mechanical holding assembly 10 being configured to define an observation window Z2 positioned around the image sensor capture surface C ([Fig.2]). This observation window Z2 corresponds to the cross-section of the container when the container is positioned and held by the mechanical assembly and therefore corresponds to the area Z1 to be observed when the container is positioned within the mechanical assembly 10 ([Fig.3]).

[0031] This mechanical retaining device 10 may comprise at least two curved strips 100, 101, for example, each in the form of a spiral. The two strips 100, 101 each hook at one end onto a ring and each have a free end. This configuration of sufficiently long strips creates a spring effect, enabling the mechanical assembly 10 to grip the container 2 by pressing against its lateral wall from the outside ([Fig. 3]).

[0032] The crown of the mechanical retaining device is advantageously notched on the outside so as to be able to mesh with an axis driven in rotation by a motor.

[0033] The toothed wheel, the shaft, and the motor M are defined as means for rotating the mechanical holding assembly. These drive means are controlled to rotate the mechanical holding assembly about itself. around an axis parallel to the Z direction. This axis corresponds to the axis of revolution of container 2, when this container 2 is for example a Petri dish.

[0034] As indicated above, the observation window Z2 defined by the mechanical holding device is positioned above and surrounds the image sensor C's capture window ([Fig. 2]). When the container 2 is held by the mechanical holding device 10, the area ZI to be observed covers the observation window Z2 defined by the mechanical holding assembly 10.

[0035] By way of non-limitation, it is possible to define several rules for the relative positioning of the observation window ZI with respect to the image sensor capture surface C: - A plane PI diametrical to the observation window Z2 passes through an axis of symmetry of the capture surface. Advantageously, this is the longitudinal axis of symmetry of the capture surface of the image sensor C ([Fig.2]). - The axis of the capture surface (orthogonal to its surface and passing through its center of gravity along Z) is offset with respect to the axis Al of revolution of the observation window Z2 ([Fig.2]). - The axis Al of revolution of the observation window Z2 advantageously passes through the small side of the capture surface so as to be able to image the central part of the observation window during the rotation of the mechanical holding assembly ([Fig.2]).

[0036] It would of course be possible to implement another configuration, by rotating the image sensor C by 90° and its capture surface relative to the observation window Z2.

[0037] The device of the invention advantageously comprises a housing 3 made of a material opaque to the light emitted by the light source S of the system.

[0038] This housing 3 advantageously includes an opening 30 onto which the light source S of the system can be adapted ([Fig.4]).

[0039] Control means 4 of the device are configured to: - Control the means of rotational driving; - Control the image sensor C in preparation for the acquisition of each image;

[0040] The principle of the invention is illustrated by [Fig.4] and [Fig.5], and comprises the following steps:

[0041] Initially, the container 2 is positioned in the device so as to be held in position by the mechanical holding assembly 10. The container is, for example, a Petri dish whose cross-section occupies the observation window Z2 defined by the mechanical holding assembly 10 (as in the top view in [Fig.3]).

[0042] T0: The image sensor C is controlled by the control means 4 to acquire a first image IMG_0 corresponding to its capture surface.

[0043] T1: The container 2 is driven in rotation about its axis by the drive means controlled by the control means 4 and after a rotation of the container by a defined rotation step (angle A in [Fig. 5]), or after a determined time, the image sensor C is controlled to acquire a second image IMG-L

[0044] T2: The container 2 is again driven in rotation around its axis by the drive means and after a rotation of the container 2 by a new defined rotation step (angle A on the [Fig.5]), or after a determined time, the image sensor is controlled to acquire a third image IMG_2.

[0045] TN: This principle continues until the container has completed a full rotation. The last image acquired is the image IMG_N at T_N.

[0046] It should be noted that: - The rotation can be carried out continuously at a constant speed, with each image being acquired at regular time intervals; - The rotation can be done step by step, with the image sensor C being controlled at each rotation step for image acquisition.

[0047] In practical terms, with a Petri dish of diameter equal to 9cm, an advantageous configuration is the following and illustrated by [Fig.5]: - The sensor is, for example, a 24X36mm; - The rotation step is, for example, equal to an angle A of 36 degrees; - An image is acquired at each rotation step; - The complete cycle is completed after 10 time steps (from T0 to T9 on [Fig.5]). We therefore obtain 10 distinct images; - The observed area ZI is reconstructed (at least partially) using the 10 images acquired by the image sensor C; - This results in a single 38cm2 image with a resolution of 3.76qm (pixel size); - Since the length of the capture surface is less than the diameter of the Petri dish, an outer ring of the area to be observed ZI will not be imaged.

[0048] The solution of the invention is adapted so that two images taken successively have an overlap area, in order to allow subsequent reconstruction (see [Fig.5]).

[0049] UC processing means of the imaging system are configured to perform reconstruction from all images acquired by the image sensor C. The UC processing means are thus configured to implement an algorithm of reconstruction. Such image reconstruction algorithms are known in the prior art and are not the subject of this application.

[0050] The present invention has many advantages, including: - A simple solution that takes into account the two geometric constraints related to: • The rectangular shape of the sensors and the circular cross-section of the Petri dish-type containers, and • The size of the sensors in relation to the size of the areas to be observed; - An optimal solution for acquiring a minimum number of images while ensuring wide coverage of the area to be observed. - A simple and easy-to-make mechanical device (e.g., by 3D printing), easily adaptable to existing sensor and Petri dish solutions.

Claims

Demands

1. A device used in a lensless imaging system, said device comprising: - An image sensor (C) defining a capture surface, - Arranged outside the capture surface of the image sensor (C), a mechanical holding assembly (10) for holding a container (2) for storing and observing a sample, said mechanical holding assembly (10) being configured to define an observation window (Z2) surrounding the capture surface of the image sensor, - Means for rotating said mechanical holding assembly (10) about an axis of rotation (A1) perpendicular to the capture surface, so as to be able to rotate the storage and observation container (2) about itself when it is held by the mechanical holding assembly (10), - Means for controlling said image sensor (C) and said rotational driving means,- The control means (4) being configured to control said image sensor (4) so ​​as to acquire several successive images during the rotation of said mechanical holding assembly (10).

2. Device according to claim 1, characterized in that the control means (4) are configured to acquire images at a suitable acquisition frequency so that two consecutive images have an overlap area.

3. Device according to claim 1 or 2, characterized in that the control means (4) are configured to control the rotating drive means continuously.

4. Device according to any one of claims 1 to 3, characterized in that the control means are configured to control the rotational drive means by applying several successive rotational steps, and in that, at each rotational step, the control means (4) are configured to control the image sensor (C) for image acquisition.

5. Device according to any one of claims 1 to 4, characterized in that the image sensor capture surface (C) is rectangular in shape.

6. Device according to claim 5, characterized in that the observation window (Z2) is disc-shaped.

7. Device according to claim 6, characterized in that the image sensor (C) is positioned so that the longitudinal axis of symmetry is aligned along a diametrical plane of the observation window (Z2).

8. Device according to any one of claims 1 to 7, characterized in that it comprises a closed housing (3) made of an opaque material, having a bottom wall integrating the image sensor (C) and defining an internal volume of suitable size to receive the mechanical assembly (10) for holding and to place the storage and observation container (2) therein, said housing (3) having an orifice (30) made along an axis perpendicular to the capture surface.

9. Device according to any one of claims 1 to 8, characterized in that the rotational drive means comprise a motor (M) whose shaft engages with a toothed wheel of the mechanical holding assembly (10).

10. Device according to any one of claims 1 to 9, characterized in that the mechanical retaining assembly (10) comprises at least two interlocking spiral-shaped strips (100, 101).

11. Device according to claim 10, characterized in that the two rings each hook by one end onto said toothed wheel.

12. Lensless imaging system comprising a light source (S) controlled to emit a light signal and processing means (UC), characterized in that it comprises a device as defined in any one of claims 1 to 11, and in that the light source (S) is arranged to emit its light signal through the viewing window (Z1) and in that the processing means (UC) are configured to reconstruct a single image from the set of images captured by the image sensor during the rotation of the mechanical holding assembly (10).

13. A method for lensless imaging of an area (Zl) to be observed in a container (2), implemented using the system defined in the claim 12, characterized in that it comprises the following steps: - Position the container (2) in the mechanical holding assembly (10); - Control the light source (S) and the means of rotational drive; - Control the image sensor (C) to acquire several successive images of the area (Zl) to be observed during the rotation of the container (2) on itself; - Reconstruct a single image from all the images acquired using the image sensor (C);

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