Imaging optical system and imaging method

Abstract

The invention discloses an imaging optical system and an imaging method. The system comprises a controller, a front lens group, a space tunable component, a rear lens group and an imaging detector, the space tunable assembly is located on a primary image plane and comprises a first polaroid, a liquid crystal spatial light modulator and a second polaroid which are sequentially arranged. The first polaroid is used for polarizing natural light emitted by a target object to obtain polarized light; the liquid crystal spatial light modulator is used for performing phase modulation on the polarized light in the target coordinate area to obtain phase modulation light; the second polaroid is used for carrying out polarization analysis on the phase modulation light to obtain amplitude modulation light; the imaging detector is used for receiving a target image corresponding to the amplitude modulation light. The system firstly performs phase modulation on incident light through the spatial light modulator, and then realizes amplitude modulation through the second polaroid, so that the dynamic range of the system is greatly expanded; the system can also modulate the light intensity of different spatial positions of the light field at one time, and the modulation efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular to an imaging optical system and an imaging method. Background Art

[0002] There are two ways to achieve large dynamic range imaging in traditional optoelectronic systems: The first method is to use an imaging detector with a large dynamic range. The second method is to use HDR (High Dynamic Range Imaging) technology, for example, to expose the same scene several times, and control the exposure time and imaging detector gain of each time to obtain a group of images, and then perform grayscale splicing on this group of images to achieve simultaneous imaging of bright and dark targets in the same scene. For example, when shooting a portrait against the sun, both the sun and the person can be photographed brightly.

[0003] The inventors found in the process of studying related technologies that the first method has high requirements on the dynamic range of the imaging detector, and the upper limit of the dynamic range is not high. The second method uses algorithm technology to achieve large dynamic range imaging, but because multiple exposures are required, the timeliness of the system is reduced, and the upper limit of the dynamic range is restricted by the integration time and electronic gain of the imaging detector. Summary of the invention

[0004] The present invention aims to at least solve the technical problems existing in the prior art. To this end, the first aspect of the present invention provides an imaging optical system, the system comprising a controller and a front mirror group, a spatially tunable component, a rear mirror group and an imaging detector placed in sequence; the controller is electrically connected to the spatially tunable component and the imaging detector, and the optical axes of the front mirror group, the spatially tunable component, the rear mirror group and the imaging detector coincide with the main optical axis of the system respectively;

[0005] The front lens group is composed of at least one group of lenses, and is used to image the target object on a primary image plane;

[0006] The spatially tunable component is located on the primary image plane, and the spatially tunable component includes a first polarizer, a liquid crystal spatial light modulator, and a second polarizer placed in sequence; the first polarizer is used to polarize the natural light emitted by the target object to obtain polarized light; the liquid crystal spatial light modulator is used to phase modulate the polarized light in the target coordinate area after receiving the target modulation signal of the controller to obtain phase modulated light; the second polarizer is used to analyze the phase modulated light to obtain amplitude modulated light;

[0007] The rear mirror group is composed of at least one group of lenses, and is used to image the amplitude modulated light onto a final image plane;

[0008] The imaging detector is located on the final image plane, and is used to receive the target image corresponding to the amplitude modulated light.

[0009] Optionally, the liquid crystal spatial light modulator is a reflective liquid crystal spatial light modulator or a transmissive liquid crystal spatial light modulator.

[0010] Optionally, the front mirror group includes at least one of a first reflective mirror and a first transmissive mirror, and the rear mirror group includes at least one of a second reflective mirror and a second transmissive mirror.

[0011] Optionally, when the liquid crystal spatial light modulator is a reflective liquid crystal spatial light modulator, the main optical axis of the system is a broken line, and the second polarizer, the rear mirror group, and the imaging detector are arranged on the reflected light path of the reflective liquid crystal spatial light modulator;

[0012] When the liquid crystal spatial light modulator is a transmissive liquid crystal spatial light modulator, the main optical axis of the system is a straight line, and the front mirror group, the first polarizer, the transmissive liquid crystal spatial light modulator, the second polarizer, the rear mirror group and the imaging detector are arranged in a straight line.

[0013] A second aspect of the present invention provides an imaging method, which is applied to the system described in the first aspect, and comprises:

[0014] When the liquid crystal spatial light modulator is in a fully transparent state, the controller acquires an initial image received by the imaging detector;

[0015] The controller divides the initial image into a plurality of grid areas of equal area;

[0016] The controller obtains the grayscale value of each pixel in each of the grid areas, and determines a target grid area that needs to be grayscale modulated from the multiple grid areas based on the grayscale value;

[0017] The controller determines, according to the spatial mapping relationship between the photosensitive surface of the imaging detector and the liquid crystal spatial light modulator, that the target grid area corresponds to the target coordinate area on the liquid crystal spatial light modulator;

[0018] The controller generates a target modulation signal according to the grayscale value of the target coordinate area;

[0019] The liquid crystal spatial light modulator performs phase adjustment on the polarized light passing through the target coordinate area according to the target modulation signal to obtain phase modulated light; the polarized light is natural light passing through the first polarizer;

[0020] After the phase modulated light is amplitude modulated by the polarization analyzer of the second polarizer, the rear mirror group images the amplitude modulated light onto the imaging detector to obtain a target image; the grayscale values ​​of the pixels in the target network area of ​​the target image are within a preset grayscale range.

[0021] Optionally, the determining a target grid area requiring grayscale modulation from the plurality of grid areas based on the grayscale value includes:

[0022] For each of the grid areas in the initial image, counting a first number of first pixel points whose grayscale values ​​are less than or equal to a preset first grayscale threshold;

[0023] If there is a first grid area where the first number is greater than a preset target number, a parameter adjustment instruction is sent to the imaging detector, where the parameter adjustment instruction includes a target parameter and a target value of the target parameter; the target parameter is an initial parameter related to the response amplitude of the imaging detector;

[0024] The imaging detector adjusts the target parameter to the target value according to the parameter adjustment signal, so that the imaging detector displays a first image; the first image is an image in which the first number of each grid area is smaller than the target number;

[0025] For each of the grid areas in the first image, counting a second number of pixel points whose grayscale values ​​are greater than a preset second grayscale threshold;

[0026] The second grid areas whose second number is greater than the target number are determined as target grid areas.

[0027] Optionally, after counting the first number of first pixel points whose grayscale values ​​are less than or equal to a preset first grayscale threshold, the method further includes:

[0028] If there is no first grid area whose first number is greater than the preset target number, then for each of the grid areas in the initial image, counting a second number of second pixel points whose grayscale values ​​are greater than a preset second grayscale threshold;

[0029] The second grid areas whose second number is greater than the target number are determined as target grid areas.

[0030] Optionally, the target modulation signal includes a target rotation angle of liquid crystal molecules in the target coordinate region, and the liquid crystal spatial light modulator performs phase adjustment on polarized light located in the target coordinate region according to the target modulation signal, including:

[0031] The liquid crystal spatial light modulator controls the liquid crystal molecules in the target coordinate region to rotate according to the target rotation angle according to the target modulation signal, so that the polarized light passing through the target coordinate region is phase-adjusted.

[0032] Optionally, the preset grayscale range is between the first grayscale threshold and the second grayscale threshold.

[0033] Optionally, before the controller acquires the initial image received by the imaging detector, the method further includes:

[0034] After the system is turned on, the liquid crystal spatial light modulator sets the rotation angles of all liquid crystal molecules to the initial angles, so that the spatial light modulator is in a fully transparent state; the fully transparent state is a state with the highest transmittance of natural polarized light;

[0035] The rear mirror group images the target object located in front of the front mirror group onto the imaging detector;

[0036] The imaging detector receives an initial image corresponding to the target object.

[0037] The embodiments of the present invention have the following beneficial effects:

[0038] An imaging optical system provided by an embodiment of the present invention comprises a controller and a front mirror group, a spatially tunable component, a rear mirror group and an imaging detector which are placed in sequence; the controller is electrically connected to the spatially tunable component and the imaging detector, and the optical axes of the front mirror group, the spatially tunable component, the rear mirror group and the imaging detector respectively coincide with the main optical axis of the system; the front mirror group is composed of at least one group of lenses and is used to image a target object on a primary image plane; the spatially tunable component is located on the primary image plane, and the spatially tunable component comprises a first polarizer, a liquid crystal spatial light modulator and a second polarizer which are placed in sequence; the first polarizer is used to polarize the natural light emitted by the target object to obtain polarized light; the liquid crystal spatial light modulator is used to phase modulate the polarized light in the target coordinate region after receiving the target modulation signal of the controller to obtain phase modulated light; the second polarizer is used to analyze the phase modulated light to obtain amplitude modulated light; the rear mirror group is composed of at least one group of lenses and is used to image the amplitude modulated light on a final image plane; the imaging detector is located on the final image plane and is used to receive the target image corresponding to the amplitude modulated light. The system can phase modulate the incident light through the cooperation of the first polarizer and the spatial light modulator, and finally realize amplitude modulation through the second polarizer, which greatly improves the dynamic range of the system; moreover, the system can phase modulate the polarized light in the target coordinate area, realize one-time modulation of the light intensity at different spatial positions of the light field, and significantly improve the modulation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a schematic diagram of an imaging optical system provided by an embodiment of the present invention;

[0040] Figure 2 A schematic diagram of an optical path of an imaging optical system including a reflective liquid crystal spatial light modulator provided by an embodiment of the present invention;

[0041] Figure 3 A schematic diagram of an optical path of an imaging optical system including a transmissive liquid crystal spatial light modulator provided by an embodiment of the present invention;

[0042] Figure 4 A schematic diagram of a practical scenario provided by an embodiment of the present invention;

[0043] Figure 5 A flowchart of the steps of an imaging method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present disclosure, unless otherwise specified, "multiple" means two or more. In addition, the use of "based on" or "according to" means openness and inclusiveness, because the process, steps, calculations or other actions "based on" or "according to" one or more of the conditions or values ​​may be based on additional conditions or values ​​beyond the described values ​​in practice.

[0046] Figure 1 It is a schematic diagram of an imaging optical system provided by an embodiment of the present invention.

[0047] like Figure 1 As shown, the system includes a controller and a front mirror group, a spatially tunable component, a rear mirror group and an imaging detector which are placed in sequence. The controller is electrically connected to the spatially tunable component, and the controller can send an electrical signal to the spatially tunable component.

[0048] The optical axes of the front mirror group, the spatially tunable component, the rear mirror group and the imaging detector coincide with the main optical axis of the system respectively.

[0049] The front lens group is composed of at least one group of lenses and is used to image the target object at a primary image plane position.

[0050] The spatially tunable component is located on the primary image plane and receives the imaging of the target object by the front lens group. The spatially tunable component includes a first polarizer, a liquid crystal spatial light modulator (LC-SLM) and a second polarizer placed in sequence. The first polarizer is placed in front of the LC-SLM and is used as a polarizer to convert the natural light emitted by the target object into polarized light. The light in natural light propagates in all directions, while the polarizer can selectively allow light propagating in only one vibration direction to pass through and remove light wave information in other directions.

[0051] The liquid crystal spatial light modulator can receive the electrical signal of the controller. Liquid crystal spatial light modulators include but are not limited to LC-SLM (Liquid Crystal-Spatial Light Modulator), or ordinary LCD (Liquid Crystal Display), etc. The liquid crystal spatial light modulator is composed of two parallel glass substrates with polarized materials, and a liquid crystal layer is configured in the middle. The rotation direction of the liquid crystal molecules in the liquid crystal layer is controlled by voltage to achieve imaging.

[0052] The liquid crystal spatial light modulator receives polarized light passing through the first polarizer, and after receiving the target modulation signal from the controller, it rotates the liquid crystal molecules in the corresponding area according to the angle specified in the target modulation signal, so that the polarization direction of the polarized light changes, which is equivalent to phase modulating the polarized light, so that the polarized light becomes phase modulated light. The phase modulated light passes through the second polarizer, and the second polarizer acts as an analyzer, which only allows light vibrating in a specific direction to pass through, and cannot allow light vibrating perpendicular to the direction to pass through. The second polarizer finally outputs the projection light of the phase modulated light on the plane of the second polarizer, which changes the intensity of the phase modulated light, thereby realizing the amplitude modulation of the light on the primary image plane, obtaining amplitude modulated light, and changing the brightness of the light.

[0053] The rear mirror group consists of at least one group of lenses and is used for imaging the amplitude modulated light onto a final image plane.

[0054] The imaging detector is located on the final image plane. It is a photoelectric sensor and a device for observing and recording particles based on imaging. The imaging detector receives the target image corresponding to the amplitude modulated light.

[0055] As an optional embodiment, the liquid crystal spatial light modulator is a reflective liquid crystal spatial light modulator or a transmissive liquid crystal spatial light modulator.

[0056] The liquid crystal spatial light modulator is composed of cover glass, front transparent electrode, liquid crystal layer, pixel layer, integrated circuit backplane and other structures.

[0057] The pixel layer is located at the bottom of the liquid crystal layer. The pixel layer of the reflective liquid crystal spatial light modulator is a reflector pixel, which is a reflective layer plated with aluminum or a dielectric film and has a very high reflection efficiency.

[0058] The pixel layer of the transmissive liquid crystal spatial light modulator is a transmissive mirror pixel, which allows light to pass through. The reflective liquid crystal spatial light modulator achieves modulation by reflecting light, and has the characteristics of high light utilization rate and deep modulation, but the cost is relatively high, and it is suitable for scenes with high light intensity requirements such as laser processing; the transmissive liquid crystal spatial light modulator allows light to pass through for modulation, and has the characteristics of simple structure, low cost, and easy integration, but the light utilization rate is relatively low, and it is often used in optical communications, optical displays and other fields.

[0059] As an optional embodiment, when the liquid crystal spatial light modulator is a reflective liquid crystal spatial light modulator, the main optical axis of the system is a broken line, and the second polarizer, the rear mirror group, and the imaging detector are arranged on the reflected light path of the reflective liquid crystal spatial light modulator;

[0060] When the liquid crystal spatial light modulator is a transmissive liquid crystal spatial light modulator, the main optical axis of the system is a straight line, and the front mirror group, the first polarizer, the transmissive liquid crystal spatial light modulator, the second polarizer, the rear mirror group and the imaging detector are arranged in a straight line.

[0061] Figure 2 A schematic diagram of the optical path of an imaging optical system including a reflective liquid crystal spatial light modulator provided in an embodiment of the present invention.

[0062] like Figure 2 As shown, in an optical system including a reflective liquid crystal spatial light modulator, the main optical axis of the system becomes a broken line after passing through the reflective liquid crystal spatial light modulator, and the second polarizer, the rear mirror group, and the imaging detector are arranged on the reflected light path of the reflective liquid crystal spatial light modulator. The reflective liquid crystal spatial light modulator phase modulates the polarized light passing through the first polarizer and reflects it to the second polarizer, and the second polarizer analyzes the light to obtain amplitude modulated light.

[0063] Figure 3 A schematic diagram of the optical path of an imaging optical system including a transmissive liquid crystal spatial light modulator provided in an embodiment of the present invention.

[0064] like Figure 3As shown, in an optical system including a transmissive liquid crystal spatial light modulator, the main optical axis of the system is a straight line, and the front mirror group, the first polarizer, the transmissive liquid crystal spatial light modulator, the second polarizer, the rear mirror group and the imaging detector are arranged in a straight line. The transmissive liquid crystal spatial light modulator phase modulates the polarized light passing through the first polarizer and transmits it to the second polarizer, and the second polarizer analyzes the light to obtain amplitude modulated light.

[0065] As an optional embodiment, the front mirror group includes at least one of a first reflective mirror and a first transmissive mirror, and the rear mirror group includes at least one of a second reflective mirror and a second transmissive mirror.

[0066] Specifically, the front mirror group and the rear mirror group can be designed as a transmission structure or a reflection structure, or a transmission-reflection hybrid structure. That is, the front mirror group can be the first reflector alone or the first transmission mirror, or can be composed of the first transmission mirror and the first reflector together, and the rear mirror group can be the second reflector alone or the second transmission mirror, or can be composed of the second transmission mirror and the second reflector together.

[0067] The front lens group and the rear lens group are preferably a transmission-reflection hybrid structure. The front lens group adopts a hybrid structure to image the target object as perfectly as possible at the position of the primary image plane, and its residual aberration can be compensated by the rear lens group. Therefore, the rear lens group is also preferably a hybrid structure, which can compensate for the residual aberration of the front lens group on the one hand and relay the image of the primary image plane to the final image plane on the other hand.

[0068] Figure 4 A schematic diagram of an actual scenario provided for an embodiment of the present invention.

[0069] like Figure 4 As shown, when the imaging optical system in this scheme images a target object, if a strong light source, such as the sun, appears in the scene, the light emitted by the sun is amplitude modulated by the spatially tunable component, so that the amplitude intensity of this part of the light is effectively modulated, and finally this part of the light is received by the detector without saturation.

[0070] In summary, the imaging optical system provided by the embodiment of the present invention comprises a controller and a front mirror group, a spatially tunable component, a rear mirror group and an imaging detector which are placed in sequence; the controller is electrically connected to the spatially tunable component and the imaging detector, and the optical axes of the front mirror group, the spatially tunable component, the rear mirror group and the imaging detector coincide with the main optical axis of the system respectively; the front mirror group is composed of at least one group of lenses, and is used to image the target object on a primary image plane; the spatially tunable component is located on the primary image plane, and the spatially tunable component comprises a first polarizer, a liquid crystal spatial light modulator and a second polarizer which are placed in sequence; the first polarizer is used to polarize the natural light emitted by the target object to obtain polarized light; the liquid crystal spatial light modulator is used to phase modulate the polarized light in the target coordinate area after receiving the target modulation signal of the controller to obtain phase modulated light; the second polarizer is used to analyze the phase modulated light to obtain amplitude modulated light; the rear mirror group is composed of at least one group of lenses, and is used to image the amplitude modulated light onto the final image plane; the imaging detector is located on the final image plane, and is used to receive the target image corresponding to the amplitude modulated light. The system can phase modulate the incident light through the cooperation of the first polarizer and the spatial light modulator, and finally realize amplitude modulation through the second polarizer, which greatly improves the dynamic range of the system; moreover, the system can phase modulate the polarized light in the target coordinate area, realize one-time modulation of the light intensity at different spatial positions of the light field, and significantly improve the modulation efficiency.

[0071] Figure 5 A flowchart of the steps of an imaging method provided by an embodiment of the present invention.

[0072] This method is applied to Figure 1-Figure 3 Any system in Figure 5 As shown, the method comprises the following steps:

[0073] Step 101: When the liquid crystal spatial light modulator is in a fully transparent state, the controller acquires an initial image received by the imaging detector.

[0074] In the embodiment of the present invention, the target object is placed in front of the front lens group of the imaging optical system, and the liquid crystal spatial light modulator is set to a fully transparent state, and the controller can obtain an image displayed on the photosensitive surface of the imaging detector. The image is the initial image of the target object, and the controller will subsequently detect whether the initial image contains an overly bright area or an overly dark area.

[0075] As an optional embodiment, before the controller acquires the initial image received by the imaging detector, the method further includes:

[0076] Step 201: After the system is turned on, the liquid crystal spatial light modulator sets the rotation angles of all liquid crystal molecules to the initial angles, so that the spatial light modulator is in a fully transparent state; the fully transparent state is a state with the highest transmittance of natural polarized light;

[0077] Step 202: the rear mirror group images the target object located in front of the front mirror group onto the imaging detector;

[0078] Step 203: The imaging detector receives an initial image corresponding to the target object.

[0079] In step 201-step 203, after the system is turned on, the liquid crystal spatial light modulator does not perform modulation work first. At this time, the liquid crystal spatial light modulator is in a fully transparent state, that is, the incident light of the target object passing through the first polarizer can pass through the liquid crystal spatial light modulator with maximum efficiency, the rear mirror group directly images the target object, and the imaging detector displays the initial image corresponding to the target object.

[0080] Step 102: The controller divides the initial image into a plurality of grid regions of equal area.

[0081] In order to detect whether the initial image contains an overly bright area or an overly dark area, the controller first divides the initial image into multiple grid areas of equal area. The size of the grid area can be set according to the needs.

[0082] Step 103: The controller obtains the grayscale value of each pixel in each of the grid areas, and determines a target grid area that needs to be grayscale modulated from the multiple grid areas based on the grayscale value.

[0083] The controller obtains the grayscale value of each pixel in each grid area, determines the number of bright spots and dark spots in the grid area according to the grayscale value, and determines whether the grid area needs grayscale modulation according to the number. The controller determines the grid area that needs grayscale modulation as the target grid area.

[0084] As an optional embodiment, determining a target grid area requiring grayscale modulation from the plurality of grid areas based on the grayscale value includes:

[0085] Step 1031: For each of the grid areas in the initial image, count the first number of first pixel points whose grayscale value is less than or equal to a preset first grayscale threshold.

[0086] Step 1032: If there is a first grid area whose first number is greater than a preset target number, a parameter adjustment instruction is sent to the imaging detector, where the parameter adjustment instruction is used to adjust a target parameter of the imaging detector; the target parameter is a parameter related to a response amplitude of the imaging detector;

[0087] Step 1033: the imaging detector adjusts the target parameter according to the parameter adjustment signal, so that the imaging detector displays a first image; the first image is an image where the first number is greater than the target number;

[0088] Step 1034: for each of the grid areas in the first image, count a second number of pixel points whose grayscale value is greater than a preset second grayscale threshold;

[0089] Step 1035: determine the second grid areas whose second number is greater than the target number as the target grid areas.

[0090] In step 1031-step 1035, the first grayscale threshold and the second grayscale threshold can be preset according to requirements, the first grayscale threshold is a value close to 0, and the second grayscale threshold is a value close to 255. Exemplarily, the first grayscale threshold can be set to 5, and the second grayscale threshold can be set to 230.

[0091] For each grid area in the initial image, the number of pixel points whose grayscale values ​​are less than or equal to the first grayscale threshold is counted to obtain a first number, and it is determined whether the first number is greater than a preset target number.

[0092] Specifically, the target number is set according to the total number of pixels included in a grid area, and the value of the target number is close to the total number of pixels. For example, the target number can be set to 80% of the total number of pixels.

[0093] If the first number is greater than the preset target number, the grid area is determined as the first grid area.

[0094] Pixels whose grayscale values ​​are less than or equal to the first grayscale threshold are dark points with lower grayscale values. The number of dark points in the first grid area is greater than the target number, indicating that the first grid area is darker as a whole and underexposed, which will bring a bad visual experience and requires grayscale modulation.

[0095] Therefore, after determining that there is a first grid area whose first number is greater than a preset target number, the controller sends a parameter adjustment instruction to the imaging detector. The parameter adjustment instruction includes a target parameter and a target value of the target parameter. The target parameter is an initial parameter related to the response amplitude of the imaging detector, such as an integration time, a gain, and other parameters.

[0096] The integration time of a detector refers to the length of time the detector integrates the light signal. In photoelectric detection, the integration time is used to collect the energy of the light signal and convert it into an electrical signal. The size of the integration time directly affects the sensitivity and signal-to-noise ratio of the detector to the light signal. Generally speaking, the longer the integration time, the more light signal energy the detector collects, the higher the signal-to-noise ratio, and the lower the response speed of the detector.

[0097] Detector gain refers to the ratio of input charge to output charge, and is usually used to reflect the sensitivity and resolution of the detector. The larger the gain, the more obvious the detector's response to the input signal, able to detect weaker signals, and improve energy resolution.

[0098] The imaging detector adjusts the target parameter to the target value according to the parameter adjustment signal, so that the grayscale value of the pixel point of the initial image displayed on the image plane of the imaging detector is increased, thereby obtaining a first image. In the grid area of ​​the first image, the first number of first pixel points whose grayscale value is less than or equal to the first grayscale threshold is less than the target number.

[0099] Next, for each grid area in the first image, a second number of pixels having a gray value greater than a second gray threshold is counted to determine whether the second number is greater than a target number. The second grid area having a second number greater than the target number is determined as a target grid area.

[0100] Pixels with grayscale values ​​greater than the second grayscale threshold are bright spots with too high grayscale values. The number of bright spots in the second grid area is greater than the target number, indicating that the second grid area is brighter overall and overexposed. This grid area will also bring a bad visual experience and is a target grid area that needs grayscale modulation.

[0101] It is understandable that in the initial image, the first grid area may exist or may not exist. After executing step 1031, if it is found that the first number is less than the preset target number, the next step 1032 is not executed, and step 1036 is executed instead. That is:

[0102] As an optional embodiment, after step 1031, the method further includes:

[0103] Step 1031: If there is no first grid area whose first number is greater than the preset target number, for each of the grid areas in the initial image, counting the second number of second pixel points whose grayscale value is greater than a preset second grayscale threshold;

[0104] Step 1032: Determine the second grid area whose second number is greater than the target number as the target grid area.

[0105] In step 1031-step 1032, if there is no first grid area whose first number is greater than the target number, it means that there is no dark spot area with low gray value in the initial image, and there is no need to adjust the dark spot area. Then, the second number of second pixel points whose gray value is greater than the second gray threshold in the initial image is directly counted to determine whether there is a bright spot area with too high gray value.

[0106] When there are second grid areas whose second number is greater than the target number in the initial image, the second grid areas are determined as target grid areas that require grayscale value adjustment.

[0107] It is understandable that the second grid area may or may not exist in the initial image. When the second grid area does not exist, it means that there is no bright spot area with too high grayscale value in the initial image, which means that there is no grid area that needs to be grayscale modulated in the initial image, and the process ends after step 1031.

[0108] Step 104 : The controller determines, based on the spatial mapping relationship between the photosensitive surface of the imaging detector and the liquid crystal spatial light modulator, that the target grid area corresponds to a target coordinate area on the liquid crystal spatial light modulator.

[0109] Record the pixel coordinates (x i_1 ~x i_m ,y i_1 ~y i_n ), according to the spatial mapping relationship between the detector photosensitive surface and the liquid crystal spatial light modulator, the target grid area corresponding to the target coordinate area (x t_1 ~x t_m ,y t_1 ~y t_n ) 。

[0110] Step 105: The controller generates a target modulation signal according to the grayscale value of the target coordinate area.

[0111] The controller generates a corresponding target modulation signal according to the magnitude relationship between the grayscale value of the target coordinate area and the second grayscale threshold.

[0112] As an optional embodiment, the target modulation signal includes a target rotation angle of the liquid crystal molecules in the target coordinate area.

[0113] Specifically, for the pixel points in the target grid area, the grayscale value of the pixel points needs to be reduced to a preset grayscale range, and the controller can determine the extent to which the grayscale value needs to be reduced based on the current grayscale value. For example, if the preset grayscale range is (5, 230], and the highest grayscale value in the target grid area is 255, the controller can determine that the grayscale value needs to be reduced by 25, that is, the grayscale value of each pixel point in the first grid area is reduced by 25. In this way, it can be ensured that the grayscale value of each pixel point in the first grid area is 230 or below.

[0114] The controller determines the target rotation angle of the liquid crystal molecules in the target coordinate region according to the magnitude of the gray value reduction required, thereby generating a target modulation signal. The target modulation signal may include target coordinate region information and target rotation angle information.

[0115] Step 106: The liquid crystal spatial light modulator performs phase adjustment on the polarized light passing through the target coordinate area according to the target modulation signal to obtain phase modulated light; the polarized light is natural light passing through the first polarizer.

[0116] The liquid crystal spatial light modulator receives the polarized light passing through the first polarizer, and after receiving the target modulation signal from the controller, rotates the liquid crystal molecules in the corresponding area according to the angle specified in the target modulation signal, so that the polarization direction of the polarized light changes, which is equivalent to phase adjustment of the polarized light, so that the polarized light becomes phase modulated light.

[0117] As an optional embodiment, the target modulation signal includes a target rotation angle of the liquid crystal molecules in the target coordinate region, and the liquid crystal spatial light modulator performs phase adjustment on the polarized light located in the target coordinate region according to the target modulation signal, including:

[0118] The liquid crystal spatial light modulator controls the liquid crystal molecules in the target coordinate region to rotate according to the target rotation angle according to the target modulation signal, so that the polarized light passing through the target coordinate region is phase-adjusted.

[0119] The liquid crystal spatial light modulator controls the liquid crystal molecules in the target coordinate region to rotate at a target angle, thereby causing the polarization degree of the polarized light in the target coordinate region to change accordingly, thereby obtaining a corresponding phase adjustment amplitude.

[0120] Step 107: After the phase modulated light is amplitude modulated by the analyzer of the second polarizer, the rear mirror group images the amplitude modulated light onto the imaging detector to obtain a target image; the grayscale values ​​of the pixels in the target network area of ​​the target image are within a preset grayscale range.

[0121] The phase modulated light passes through the second polarizer, which acts as an analyzer, allowing only light vibrating in a specific direction to pass through, and not light vibrating perpendicular to that direction. The second polarizer ultimately outputs the projection light of the phase modulated light in the polarization direction of the second polarizer, changing the intensity of the phase modulated light, thereby achieving amplitude modulation of the light on the primary image plane, obtaining amplitude modulated light, and changing the brightness of the light.

[0122] The rear mirror group images the amplitude modulated light onto the final image plane. The imaging detector is located on the final image plane and is used to receive the target image corresponding to the amplitude modulated light.

[0123] The grayscale values ​​of the pixels in the target grid area of ​​the initial image are within the preset grayscale range after modulation, so that the grayscale values ​​of the pixels in the target image are all within the preset grayscale range.

[0124] As an optional embodiment, the preset grayscale range is between the first grayscale threshold and the second grayscale threshold.

[0125] Exemplarily, the preset grayscale range is (5, 230). In this way, the grayscale value of the pixel points in each grid area of ​​the target image can be between the first grayscale threshold and the second grayscale threshold, so that the pixel points are neither too bright nor too dark, thereby improving the visual effect of the target image.

[0126] In summary, the imaging method provided by the embodiment of the present invention is as follows: when the liquid crystal spatial light modulator is in a fully transparent state, the controller obtains an initial image received by the imaging detector; the controller divides the initial image into multiple grid areas of equal area; the controller obtains the grayscale value of each pixel in each of the grid areas, and determines the target grid area that needs to be grayscale modulated from the multiple grid areas based on the grayscale value; the controller determines that the target grid area corresponds to the target coordinate area on the liquid crystal spatial light modulator according to the spatial mapping relationship between the photosensitive surface of the imaging detector and the liquid crystal spatial light modulator; the controller generates a target modulation signal according to the grayscale value of the target coordinate area; the liquid crystal spatial light modulator phase modulates the polarized light passing through the target coordinate area according to the target modulation signal to obtain phase modulated light; the polarized light is natural light passing through the first polarizer; after the phase modulated light is amplitude modulated by the polarization analyzer of the second polarizer, the rear mirror group images the amplitude modulated light onto the imaging detector to obtain a target image; the grayscale value of the pixel in the target grid area of ​​the target image is within a preset grayscale range. The system can phase modulate the incident light through the cooperation of the first polarizer and the spatial light modulator, and finally realize amplitude modulation through the second polarizer, which greatly improves the dynamic range of the system; moreover, the system can perform one-time phase modulation on the polarized light in the entire target coordinate area, realize one-time modulation of the light intensity at different spatial positions of the light field, and significantly improve the modulation efficiency.

[0127] Regarding the device in the above embodiment, the specific manner in which each module performs operations has been described in detail in the embodiment of the method, and will not be elaborated here.

[0128] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0129] Those skilled in the art will readily appreciate other embodiments of the present disclosure after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present disclosure that comply with the general principles of the present disclosure and include common knowledge or customary techniques in the art that are not disclosed in the present disclosure. The description and examples are to be considered exemplary only, and the true scope and spirit of the present disclosure are indicated by the following claims.

[0130] It should be understood that the present disclosure is not limited to the exact structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. An imaging optical system, characterized in that: The system comprises a controller and a front mirror group, a spatially tunable component, a rear mirror group and an imaging detector which are placed in sequence; the controller is electrically connected to the spatially tunable component and the imaging detector, and the optical axes of the front mirror group, the spatially tunable component, the rear mirror group and the imaging detector respectively coincide with the main optical axis of the system; The front lens group is composed of at least one group of lenses, and is used to image the target object on a primary image plane; The spatially tunable component is located on the primary image plane, and the spatially tunable component includes a first polarizer, a liquid crystal spatial light modulator, and a second polarizer placed in sequence; the first polarizer is used to polarize the natural light emitted by the target object to obtain polarized light; the liquid crystal spatial light modulator is used to phase modulate the polarized light in the target coordinate area after receiving the target modulation signal of the controller to obtain phase modulated light; the second polarizer is used to analyze the phase modulated light to obtain amplitude modulated light; The rear mirror group is composed of at least one group of lenses, and is used to image the amplitude modulated light onto a final image plane; The imaging detector is located on the final image plane, and is used to receive the target image corresponding to the amplitude modulated light.

2. The system according to claim 1, characterized in that The liquid crystal spatial light modulator is a reflective liquid crystal spatial light modulator or a transmissive liquid crystal spatial light modulator.

3. The system according to claim 1, characterized in that The front mirror group includes at least one of a first reflective mirror and a first transmissive mirror, and the rear mirror group includes at least one of a second reflective mirror and a second transmissive mirror.

4. The system according to claim 2, characterized in that When the liquid crystal spatial light modulator is a reflective liquid crystal spatial light modulator, the main optical axis of the system is a broken line, and the second polarizer, the rear mirror group, and the imaging detector are arranged on the reflected light path of the reflective liquid crystal spatial light modulator; When the liquid crystal spatial light modulator is a transmissive liquid crystal spatial light modulator, the main optical axis of the system is a straight line, and the front mirror group, the first polarizer, the transmissive liquid crystal spatial light modulator, the second polarizer, the rear mirror group and the imaging detector are arranged in a straight line.

5. An imaging method, characterized in that: The method is applied to the system described in any one of claims 1 to 4, and the method comprises: When the liquid crystal spatial light modulator is in a fully transparent state, the controller acquires an initial image received by the imaging detector; The controller divides the initial image into a plurality of grid areas of equal area; The controller obtains the grayscale value of each pixel in each of the grid areas, and determines a target grid area that needs to be grayscale modulated from the multiple grid areas based on the grayscale value; The controller determines, according to the spatial mapping relationship between the photosensitive surface of the imaging detector and the liquid crystal spatial light modulator, that the target grid area corresponds to the target coordinate area on the liquid crystal spatial light modulator; The controller generates a target modulation signal according to the grayscale value of the target coordinate area; The liquid crystal spatial light modulator performs phase adjustment on the polarized light passing through the target coordinate area according to the target modulation signal to obtain phase modulated light; the polarized light is natural light passing through the first polarizer; After the phase modulated light is amplitude modulated by the polarization analyzer of the second polarizer, the rear mirror group images the amplitude modulated light onto the imaging detector to obtain a target image; the grayscale values ​​of the pixels in the target network area of ​​the target image are within a preset grayscale range.

6. The method according to claim 5, characterized in that The determining a target grid area requiring grayscale modulation from the plurality of grid areas based on the grayscale value comprises: For each of the grid areas in the initial image, counting a first number of first pixel points whose grayscale values ​​are less than or equal to a preset first grayscale threshold; If there is a first grid area where the first number is greater than a preset target number, a parameter adjustment instruction is sent to the imaging detector, where the parameter adjustment instruction includes a target parameter and a target value of the target parameter; the target parameter is an initial parameter related to the response amplitude of the imaging detector; The imaging detector adjusts the target parameter to the target value according to the parameter adjustment signal, so that the imaging detector displays a first image; the first image is an image in which the first number of each grid area is smaller than the target number; For each of the grid areas in the first image, counting a second number of pixel points whose grayscale values ​​are greater than a preset second grayscale threshold; The second grid areas whose second number is greater than the target number are determined as target grid areas.

7. The method according to claim 6, characterized in that After counting the first number of first pixel points whose grayscale values ​​are less than or equal to the preset first grayscale threshold, the method further includes: If there is no first grid area whose first number is greater than the preset target number, then for each of the grid areas in the initial image, counting a second number of second pixel points whose grayscale values ​​are greater than a preset second grayscale threshold; The second grid areas whose second number is greater than the target number are determined as target grid areas.

8. The method according to claim 7, characterized in that The target modulation signal includes a target rotation angle of the liquid crystal molecules in the target coordinate region, and the liquid crystal spatial light modulator performs phase adjustment on the polarized light in the target coordinate region according to the target modulation signal, including: The liquid crystal spatial light modulator controls the liquid crystal molecules in the target coordinate region to rotate according to the target rotation angle according to the target modulation signal, so that the polarized light passing through the target coordinate region is phase-adjusted.

9. The method according to claim 6, characterized in that The preset grayscale range is between the first grayscale threshold and the second grayscale threshold.

10. The method according to claim 5, characterized in that Before the controller acquires the initial image received by the imaging detector, the method further includes: After the system is turned on, the liquid crystal spatial light modulator sets the rotation angles of all liquid crystal molecules to the initial angles, so that the spatial light modulator is in a fully transparent state; the fully transparent state is a state with the highest transmittance of natural polarized light; The rear mirror group images the target object located in front of the front mirror group onto the imaging detector; The imaging detector receives an initial image corresponding to the target object.

Images