Single-exposure video compression imaging system based on ferroelectric liquid crystal spatial light modulator

Abstract

The utility model discloses a single exposure video compression imaging system based on ferroelectric liquid crystal spatial light modulator, in single exposure video compression imaging system, the ferroelectric liquid crystal spatial light modulator is used first to replace traditional digital micromirror device to realize high -speed space -time modulation. Utilize the bistable phase delay characteristic of ferroelectric liquid crystal spatial light modulator, combine linear polarization incident light and polarization beam splitter, realize a novel binary amplitude modulation together, overcome the technical defects that the realization scheme based on DMD exists optical path structure complex and the imaging quality is limited.

Description

Technical Field

[0001] This utility model relates to the field of optical system technology, and more specifically, to a single-exposure video compression imaging system based on a ferroelectric liquid crystal spatial light modulator. Background Technology

[0002] Single-exposure video compression imaging is an emerging computational imaging technique. Its core idea is to rapidly encode the spatiotemporal information of a dynamic scene using a single encoding element (usually a spatial light modulator), then perform a single-exposure measurement using a low-speed detector, and finally reconstruct a high-speed video sequence from a single two-dimensional measurement image using computational algorithms. This technology overcomes the physical limitations of detector frame rates in traditional high-speed imaging and has enormous application potential in scientific observation, industrial inspection, and biomedicine.

[0003] In existing single-exposure video compression imaging schemes, digital micromirror devices (DMDs) are the most commonly used spatial light modulators. DMDs achieve binary (0 or 1) amplitude modulation of incident light by controlling the deflection state (+12° or -12°) of millions of micromirror units on their surface. By rapidly switching these micromirror patterns, dynamic scenes can be temporally controlled.

[0004] However, the DMD-based implementation has the following inherent drawbacks: First, the optical path structure is complex and difficult to align: the deflection axis of each micromirror in the DMD is at a 45° angle to its pixel array plane. This special geometric design results in the incident and outgoing light paths not being on the same plane, making the optical path design of the entire optical system complex. Multiple mirrors are needed for optical path folding and height compensation, making system assembly and adjustment difficult. Although rotating the entire DMD by 45° can bring the optical paths to the same plane, this causes the projected image to rotate by 45°, requiring additional image processing steps for correction, increasing system complexity and error. Second, imaging quality is limited: the deflection angle of the DMD micromirrors is fixed at ±12°. This special angle means that the object plane, the DMD modulation plane, and the CCD detection plane cannot simultaneously satisfy the conjugate relationship optically, meaning they cannot simultaneously achieve clear imaging. This non-conjugate relationship introduces aberrations, reducing the system's light energy utilization and the signal-to-noise ratio and spatial resolution of the final reconstructed image. Utility Model Content

[0005] The technical problem this invention aims to solve is how to overcome the technical defects of existing DMD-based implementation schemes, such as complex optical path structures and limited imaging quality. To overcome these defects, this invention provides a single-exposure video compression imaging system based on a ferroelectric liquid crystal spatial light modulator.

[0006] This invention provides a single-exposure video compression imaging system based on a ferroelectric liquid crystal spatial light modulator, comprising:

[0007] The imaging lens is configured to converge the light beams formed by the moving scene to obtain a converged light beam;

[0008] A ferroelectric liquid crystal spatial light modulator is configured to perform spatiotemporal binary amplitude modulation on reflected polarized light to obtain a modulated beam.

[0009] A polarization beam splitter is configured to separate the converging beam according to polarization state to form the reflected polarized light and the transmitted polarized light, and to transmit the reflected polarized light to the ferroelectric liquid crystal spatial light modulator, and also to transmit the modulated beam;

[0010] A relay imaging lens is configured to image the modulated beam transmitted from the polarizing beam splitter in order to obtain imaging information corresponding to the dynamic scene.

[0011] An array detector is configured to receive and expose imaging information corresponding to the dynamic scene to obtain a two-dimensional measurement image;

[0012] in,

[0013] The imaging lens and the polarization beam splitter are arranged sequentially along the propagation direction of the light beam formed by the dynamic scene. The polarization beam splitter and the ferroelectric liquid crystal spatial light modulator are arranged sequentially along the propagation direction of the reflected polarized light. The ferroelectric liquid crystal spatial light modulator, the polarization beam splitter, the relay imaging lens, and the area array detector are arranged sequentially along the propagation direction of the modulated light beam.

[0014] This invention discloses a single-exposure video compression imaging system based on a ferroelectric liquid crystal spatial light modulator (F-SLM). It is the first single-exposure video compression imaging system to use a F-SLM to replace the traditional digital micromirror device (DMD) for high-speed temporal control. Utilizing the dual-state phase delay characteristic of the F-SLM, combined with linearly polarized incident light and a polarization beam splitter (PBS), a novel binary amplitude modulation is achieved. Specifically, the polarization state of the reflected light is changed by controlling the pixel state of the F-SLM, and the polarization beam splitter selectively controls the polarization state of the emitted light (one state reflected, another transmitted), achieving physical separation of the "0" and "1" modulated light. Furthermore, because the reflective surface of the F-SLM is parallel and fixed to the pixel plane, it requires no mechanical deflection. Therefore, the optical axis of the optical system constructed based on the F-SLM is always at the same plane height, resulting in a regular structure that is easy to assemble and adjust. Meanwhile, the object surface, the modulation surface of the ferroelectric liquid crystal spatial light modulator, and the target surface of the detector are more likely to satisfy the conjugate relationship, thereby obtaining higher imaging quality and overcoming the technical defects of complex optical path structure and limited imaging quality of the DMD-based implementation scheme.

[0015] In one possible implementation, the imaging lens is a lens or lens that acts as a relay imaging device to accurately image the target dynamic scene onto the polarization beam splitter.

[0016] In one possible implementation, the polarization beam splitter is a beam splitter with separable polarization states; thereby achieving clear finding of the reflecting and transmitting surfaces, and deflecting the light beam by 90° through its reflecting surface towards the ferroelectric liquid crystal spatial light modulator, thus achieving the effect of adjustable optical path.

[0017] In one possible implementation, the relay imaging lens is an imaging lens that serves as a relay imaging lens.

[0018] In one possible implementation, the relay imaging lens includes a first lens and a second lens arranged sequentially along the propagation direction of the modulated beam, the first lens and the second lens forming a 4f system; thereby enabling the modulation surface of the ferroelectric liquid crystal spatial light modulator to be relay-imaged onto the target surface of the array detector for single long exposure, to acquire compressed measurement values ​​and transmit them to a computer.

[0019] In one possible implementation, the exposure time of the area array detector is longer than the display time of one pattern of the ferroelectric liquid crystal spatial light modulator; thus, the ferroelectric liquid crystal spatial light modulator can quickly switch several different binary random mask patterns throughout the exposure time, ensuring that all the high-speed spatiotemporal change information of the dynamic scene is compressed and encoded into one exposure of the detector, and finally forming a two-dimensional measurement image. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the single-exposure video compression imaging system based on DMD disclosed in Embodiment 1 of this application;

[0021] Figure 2 This is a schematic diagram illustrating how the relay image plane of an object is difficult to coincide with the surface of the DMD in the single-exposure video compression imaging system based on DMD disclosed in Embodiment 1 of this application, which affects the final image quality.

[0022] Figure 3 This is a schematic diagram illustrating the principle of implementing binary amplitude modulation as disclosed in Embodiment 1 of this application;

[0023] Figure 4 This is a schematic diagram of a single-exposure video compression imaging system based on a ferroelectric liquid crystal spatial light modulator disclosed in Embodiment 1 of this application;

[0024] Figure 5 This is a schematic diagram of a single-exposure video compression imaging system based on a ferroelectric liquid crystal spatial light modulator disclosed in Embodiment 2 of this application.

[0025] Explanation of reference numerals in the attached figures:

[0026] 1. Dynamic scene, 2. Imaging lens, 3. Ferroelectric liquid crystal spatial light modulator, 4. Polarization beam splitter, 5. Relay imaging lens, 51. Lens 1, 52. Lens 2, 6. Area array detector. Detailed Implementation

[0027] First, those skilled in the art should understand that these embodiments are merely used to explain the technical principles of the embodiments of this application and are not intended to limit the scope of protection of the embodiments of this application. Those skilled in the art can make adjustments as needed to adapt to specific application scenarios.

[0028] Secondly, in the embodiments of this application, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0029] The present application will be further described in detail below using two embodiments, in conjunction with the accompanying drawings and specific examples.

[0030] Example 1:

[0031] See Figures 1-2 In the diagram, L1, L2, L3, and L4 all represent lenses. In existing single-exposure video compression imaging schemes, the DMD used in implementations based on digital micromirror devices (DMDs) is typically placed at a 45° angle to the camera. Figure 1 As shown, this increases the complexity of system assembly and alignment, resulting in a complex optical path structure that is difficult to align. Furthermore, it is difficult for the relay image plane of the object to coincide with the surface of the DMD. Figure 2 The image shows a 24° angle between the relay image plane and the DMD surface, which affects the final image quality.

[0032] For this, see Figures 3-4 This application discloses a single-exposure video compression imaging system based on a ferroelectric liquid crystal spatial light modulator. Figure 4 This is a schematic diagram of the single-exposure video compression imaging system, which includes an imaging lens 2 and a ferroelectric liquid crystal spatial light modulator (…). Figure 3 3. Polarization beam splitter (abbreviated as F-SLM in Chinese) Figure 3The array consists of PBS (abbreviated as PBS) 4, relay imaging lens 5, and area array detector 6. The imaging lens 2 and polarization beam splitter 4 are arranged sequentially along the beam propagation direction formed by the dynamic scene 1. The polarization beam splitter 4 and ferroelectric liquid crystal spatial light modulator 3 are arranged sequentially along the propagation direction of the reflected polarized light output by the polarization beam splitter 4. The ferroelectric liquid crystal spatial light modulator 3, polarization beam splitter 4, relay imaging lens 5, and area array detector 6 are arranged sequentially along the propagation direction of the modulated beam output by the ferroelectric liquid crystal spatial light modulator 3.

[0033] In this single-exposure video compression imaging system, the imaging lens 2 is configured to converge the light beam formed by the dynamic scene 1 to obtain a converged light beam. The imaging lens 2 is a lens or lens that serves as a relay imaging device, such as a single lens, an SLR camera lens, or an industrial lens. In this embodiment, the imaging lens 2 used is a single lens.

[0034] In this single-exposure video compression imaging system, the ferroelectric liquid crystal spatial light modulator 3 is configured to perform spatiotemporal binary amplitude modulation on the reflected polarized light to obtain a modulated beam. See also Figure 3 The reflected polarized light, formed by the polarization beam splitter 4, is incident on the surface of the ferroelectric liquid crystal spatial light modulator 3. Under the control of its driving circuit, the ferroelectric liquid crystal spatial light modulator 3 can switch the state of each pixel at a high frame rate (thousands to tens of thousands of hertz). Each pixel has two states (state 0 and state 1), corresponding to different orientations of the fast axis of the liquid crystal molecules (for example, in state 0, the fast axis direction is consistent with the polarization direction of the incident light, and in state 1, the fast axis direction forms a 45° angle with the polarization direction of the incident light). When the pixel is in state 0, the polarization direction of the incident linearly polarized light is parallel to the direction of the liquid crystal fast axis, so its polarization state does not change and it still maintains the original linear polarization state (vertical polarization) reflection. When the pixel is in state 1, the pixel of the ferroelectric liquid crystal spatial light modulator 3 is equivalent to a half-wave plate, rotating the polarization direction of the incident linearly polarized light by 90°, turning it into horizontally polarized light (or elliptically polarized light) for reflection.

[0035] In this single-exposure video compression imaging system, the polarization beam splitter 4 is configured to separate the converging beam according to its polarization state to form reflected polarized light and transmitted polarized light, and to transmit the reflected polarized light to the ferroelectric liquid crystal spatial light modulator 3, while also transmitting the modulated beam. For example... Figure 3 and Figure 4 As shown, polarization beam splitter 4 separates the incident light into reflected light and transmitted light according to their polarization states. The reflected light (e.g., Figure 3In path 3, the incident light (for S-polarized light) is redirected by 90 degrees, while the transmitted light (for P-polarized light) passes directly through. By precisely setting the polarization state of the incident light or the orientation of the polarization beam splitter 4, it can be ensured that only a single linearly polarized light (such as vertically polarized light) is reflected towards the ferroelectric liquid crystal spatial light modulator 3. The polarization beam splitter 4 simultaneously serves the dual function of changing the direction of the optical path and polarizing the light. In this embodiment, the polarization beam splitter 4 is a beam splitter with separable polarization states, such as a cubic polarization beam splitter.

[0036] In this single-exposure video compression imaging system, the relay imaging lens 5 is configured to image the modulated beam transmitted from the polarization beam splitter 4 to obtain imaging information corresponding to the dynamic scene 1. (See also...) Figure 4 In this embodiment, the relay imaging lens 5 is an imaging lens that performs relay imaging function.

[0037] In this single-exposure video compression imaging system, the area array detector 6 is configured to receive and expose the imaging information corresponding to the dynamic scene 1 to obtain a two-dimensional measurement image. In this embodiment, the area array detector 6 is a charge-coupled device (CCD). In this embodiment, the exposure time of the area array detector 6 is longer than the display time of one pattern of the ferroelectric liquid crystal spatial light modulator 3. Specifically, during the entire exposure time in this embodiment, the ferroelectric liquid crystal spatial light modulator 3 rapidly switches between dozens to hundreds of different binary random mask patterns, compressing and encoding all the high-speed spatiotemporal change information of the dynamic scene into a single exposure of the area array detector 6, forming a two-dimensional measurement image. Finally, using the pre-known modulation pattern sequence of the ferroelectric liquid crystal spatial light modulator 3 and the corresponding compressed sensing reconstruction algorithm on a computer, the original high-speed video sequence is reconstructed from the single measurement image.

[0038] The single-exposure video compression imaging system based on a ferroelectric liquid crystal spatial light modulator in this embodiment innovatively uses a ferroelectric liquid crystal spatial light modulator 3 to replace the traditional digital micromirror device (DMD) to achieve high-speed temporal control. Utilizing the dual-state phase delay characteristic of the ferroelectric liquid crystal spatial light modulator 3, combined with linearly polarized incident light and a polarization beam splitter 4, a novel binary amplitude modulation is achieved. Specifically, the polarization state of the reflected light can be changed by controlling the pixel state of the ferroelectric liquid crystal spatial light modulator 3, and then the polarization beam splitter 4 can selectively polarize the emitted light (reflecting one state, transmitting another state) to achieve the physical separation of the "0" and "1" modulated light. Furthermore, since the reflective surface of the ferroelectric liquid crystal spatial light modulator 3 is parallel and fixed to the pixel plane, it has the characteristic of requiring no mechanical deflection. Therefore, the optical axis of the optical system constructed based on the ferroelectric liquid crystal spatial light modulator 3 is always located at the same plane height, resulting in a regular structure that is easy to assemble and adjust. Meanwhile, the object surface, the modulation surface of the ferroelectric liquid crystal spatial light modulator 3, and the target surface of the array detector 6 are more likely to satisfy the conjugate relationship, thereby obtaining higher imaging quality and overcoming the technical defects of complex optical path structure and limited imaging quality of the DMD-based implementation scheme.

[0039] Example 2:

[0040] See Figure 5 This application discloses a single-exposure video compression imaging system based on a ferroelectric liquid crystal spatial light modulator. Figure 5 This is a schematic diagram of the single-exposure video compression imaging system. The difference between this embodiment and Embodiment 1 is that in the single-exposure video compression imaging system disclosed herein, the relay imaging lens 5 includes a first lens 51 and a second lens 52 arranged sequentially along the propagation direction of the modulation beam. Lens 51 and second lens 52 form a 4f system, meaning that the focal length of both lens 51 and second lens 52 is f, and the image-side focal plane of lens 51 coincides with the object-side focal plane of lens 52. This allows the modulation surface of the ferroelectric liquid crystal spatial light modulator to be relayed onto the target surface of the area array detector for a single long exposure, acquiring compressed measurement values ​​and transmitting them to a computer.

[0041] In the description of the embodiments of this application, it should be noted that the terms "inner", "outer", "front", "rear", etc., indicating the direction or positional relationship are based on the direction or positional relationship shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or component must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this application.

[0042] In the description of this application, the references to terms such as "an embodiment," "some embodiments," "in this embodiment," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0043] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A single-exposure video compression imaging system based on a ferroelectric liquid crystal spatial light modulator, characterized in that, include: The imaging lens (2) is configured to converge the light beam formed by the dynamic scene (1) to obtain a converged light beam; The ferroelectric liquid crystal spatial light modulator (3) is configured to perform spatiotemporal binary amplitude modulation on the reflected polarized light to obtain a modulated beam; The polarization beam splitter (4) is configured to separate the converging beam according to polarization state to form the reflected polarized light and the transmitted polarized light, and to transmit the reflected polarized light to the ferroelectric liquid crystal spatial light modulator (3), and also to transmit the modulated beam; The relay imaging lens (5) is configured to image the modulated beam transmitted from the polarization beam splitter (4) to obtain imaging information corresponding to the dynamic scene (1); The array detector (6) is configured to receive and expose the imaging information corresponding to the dynamic scene (1) to obtain a two-dimensional measurement image; in, The imaging lens (2) and the polarization beam splitter (4) are arranged sequentially along the beam propagation direction formed by the dynamic scene (1). The polarization beam splitter (4) and the ferroelectric liquid crystal spatial light modulator (3) are arranged sequentially along the propagation direction of the reflected polarized light. The ferroelectric liquid crystal spatial light modulator (3), the polarization beam splitter (4), the relay imaging lens (5), and the area array detector (6) are arranged sequentially along the propagation direction of the modulated beam.

2. The single-exposure video compression imaging system based on a ferroelectric liquid crystal spatial light modulator according to claim 1, characterized in that, The imaging lens (2) is a lens or lens that serves as a relay imaging device.

3. The single-exposure video compression imaging system based on a ferroelectric liquid crystal spatial light modulator according to claim 1 or 2, characterized in that, The polarization beam splitter (4) is a beam splitter that can separate polarization states.

4. The single-exposure video compression imaging system based on a ferroelectric liquid crystal spatial light modulator according to claim 3, characterized in that, The relay imaging lens (5) is an imaging lens that performs relay imaging function.

5. The single-exposure video compression imaging system based on a ferroelectric liquid crystal spatial light modulator according to claim 3, characterized in that, The relay imaging lens (5) includes a first lens (51) and a second lens (52) arranged sequentially along the propagation direction of the modulated beam, and the first lens (51) and the second lens (52) form a 4f system.

6. The single-exposure video compression imaging system based on a ferroelectric liquid crystal spatial light modulator according to claim 4 or 5, characterized in that, The exposure time of the area array detector (6) is longer than the display time of one pattern of the ferroelectric liquid crystal spatial light modulator (3).

Images