Backlight imaging system based on variable diaphragm and control method

Abstract

The invention belongs to the technical field of optical imaging, and particularly provides a high-light background imaging system based on a variable diaphragm. The system comprises a variable diaphragm module, an optical lens group, an image sensor and a control processing center. According to the imaging system, an iris diaphragm is initialized, an image sensor obtains an original image and transmits the data to a control processing center, the control processing center tracks a strong light area, a iris diaphragm controller is enabled through calculation, the center position, the shape, the size and the transmittance distribution of the diaphragm are adjusted, strong light is filtered, and the high light is obtained. And finally, carrying out data fusion on a new image obtained by the image sensor and the original image to realize restoration of detail information lost due to strong light. The invention has the advantages of variable diaphragm non-mechanical regulation and control, high dynamic regulation range and the like.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging system technology, specifically relating to an imaging system with adjustable aperture area distribution, which is particularly suitable for image acquisition and processing under strong light backgrounds. Background Technology

[0002] Currently, in optical imaging systems, when facing a strong background, conventional image sensors are prone to saturation or overexposure due to the excessively high intensity of incident light, leading to loss of image details or even failure to form a proper image. Traditional imaging devices typically use fixed aperture or global exposure control methods to adjust the amount of light entering the sensor. However, under different lighting conditions, a fixed aperture cannot be dynamically adjusted to optimize the amount of light entering the sensor, nor can it adjust the depth of field as needed. In high-contrast scenes, global exposure may cause the sensor to fail to simultaneously and correctly capture details in both very bright and very dark areas.

[0003] Existing technologies also employ dynamic aperture or digital image processing techniques to mitigate the effects of strong light. For example, some camera systems balance image brightness by adjusting shutter speed or increasing ISO, but because the optical path is not dynamically controlled, the problem of image distortion caused by localized strong light cannot be fundamentally solved. Furthermore, some high-end camera devices have introduced multi-frame HDR fusion technology, but it still has significant limitations in dynamic range.

[0004] Therefore, there is an urgent need to provide a technical solution that can adjust the optical path and restore the target details with high dynamic range under strong light background, so as to improve image quality and system adaptability. Summary of the Invention

[0005] This invention aims to address the problems of difficulty in restoring local details and limited dynamic range in existing technologies under strong light conditions, and provides a strong light background imaging system based on a variable aperture. By employing advanced optical design and intelligent control algorithms, this system can achieve clear, high-quality imaging results in high dynamic range scenes.

[0006] The objective of this invention is achieved as follows: A high-light background imaging system based on a variable aperture includes a front variable aperture group, an optical lens group, a rear variable aperture group, a variable aperture controller, an image sensor, and a control and processing center. The front variable aperture group is located between the target object and the optical lens group, while the rear variable aperture group is located between the optical lens group and the image sensor. The variable aperture can adjust its center position, shape, size, and transmittance distribution in real time. The front and rear variable aperture groups are each connected to the variable aperture controller, and the variable aperture controller and the image sensor are each connected to the control and processing center. Attached Figure Description

[0007] Figure 1 This is a system architecture diagram.

[0008] Figure 2 This is a schematic diagram showing the movement of the aperture center.

[0009] Figure 3 This is a schematic diagram showing the changes in the shape and size of the aperture.

[0010] Figure 4 This is a schematic diagram showing the change in the transmittance of the aperture.

[0011] Figure 5 This is a schematic diagram of a combination of a variable aperture and a liquid crystal spatial light modulator.

[0012] Figure 6 This is a schematic diagram of the light filtering principle.

[0013] Figure 7 A flowchart for deriving the basic formula for light filtering.

[0014] Figure 8 This is a top view of a four-channel voltage-driven liquid crystal variable aperture.

[0015] Figure 9 and Figure 10 This is an aperture image generated by adjusting the variable aperture of a liquid crystal driven by four voltage channels.

[0016] Figure 11 , Figure 12 and Figure 13 The figure shows some experimental results of using four voltages to drive a liquid crystal variable aperture.

[0017] Explanation of reference numerals in the attached diagram: 1. Strong light background; 2. Target object; 3. Front variable aperture group; 4. Optical lens group; 5. Rear variable aperture group; 6. Variable aperture controller; 7. Image sensor; 8. Control and processing center; 901. Aperture; 902. Liquid crystal spatial light modulator; 903. Light divergence area of ​​liquid crystal spatial light modulator; 904. Electrode; 905. Liquid crystal distribution area. Detailed Implementation

[0018] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the preferred embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0019] Example 1: A strong light background imaging system based on a variable aperture, such as Figure 1As shown, the system includes a front variable aperture group (3), an optical lens group (4), a rear variable aperture group (5), a variable aperture controller (6), an image sensor (7), and a control processing center (8). The front variable aperture group (3) is positioned between the target object (2) and the optical lens group (4), and the rear variable aperture group (5) is positioned between the optical lens group (4) and the image sensor (7). The front variable aperture group (3) and the rear variable aperture group (5) are respectively connected to the variable aperture controller (6), and the variable aperture controller (6) and the image sensor (7) are respectively connected to the control processing center (8). The centers of the four parts—the front variable aperture group (3), the optical lens group (4), the rear variable aperture group (5), and the image sensor (7)—are located on the same optical axis. The specific working process of the imaging system is as follows: First, the front variable aperture group (3) and the rear variable aperture group (5) are initialized, that is, each aperture group is in the maximum light transmission state. After initialization, the imaging system is aligned with the target object (2) and the focal length of the optical lens group (4) is adjusted so that the image sensor (7) obtains a clear original image and transmits the original image data to the control processing center (8). After receiving the original image data, the control processing center (8) uses the highlight detection program to analyze it, obtain the highlight area distribution, and calculate the strong light path and the optimal center position, shape and size of each aperture. The transmittance distribution is then calculated, and the control processing center (8) causes the variable aperture controller (6) to adjust the aperture center position, shape, size, and transmittance distribution of the front variable aperture group (3) and the rear variable aperture group (5) to the calculated optimal center position, shape, size, and transmittance distribution to achieve the filtering of strong light. After the above operations are completed, the image sensor (7) obtains a new image and transmits the new image data to the control processing center (8). The control processing center (8) compares and fuses the new image with the original image to finally generate an image with good detail information, thereby restoring the detail information lost due to strong light.

[0020] Example 2: In this example, the center positions of the apertures of the front variable aperture group (3) and the rear variable aperture group (5) are adjustable, such as... Figure 2 As shown. When the control processing center (8) receives the raw image data transmitted by the image sensor (7), it identifies the highlight area through a highlight recognition algorithm, analyzes the distribution of strong light paths, and calculates the optimal aperture center positions of the front variable aperture group (3) and the rear variable aperture group (5). Based on this result, the control processing center (8) sends a command to the variable aperture controller (6) to adjust the aperture centers of the front variable aperture group (3) and the rear variable aperture group (5) to the calculated optimal positions. This process can effectively reduce the impact of strong light on image quality, enabling clear and high-quality images to be obtained even under extreme lighting conditions.

[0021] Example 3: In this example, the shape and size of the apertures in the front variable aperture group (3) and the rear variable aperture group (5) are adjustable, such as... Figure 3 As shown. After receiving the raw image data from the image sensor (7), the control processing center (8) identifies the highlight areas and analyzes the distribution of strong light paths through the highlight recognition algorithm, and uses advanced image processing algorithms to determine the optimal aperture shape and size of the front variable aperture group (3) and the rear variable aperture group (5). Once the optimal aperture shape and size are determined, the control processing center (8) controls the variable aperture controller (6) to adjust the front variable aperture group (3) and the rear variable aperture group (5) accordingly, so that each aperture is adjusted to the calculated optimal shape and size. These parameter adjustments are to adapt to the lighting conditions in different scenes, especially to effectively block local high-brightness areas, in order to achieve the best imaging effect.

[0022] Example 4: In this example, the aperture transmittance of the front variable aperture group (3) and the rear variable aperture group (5) is adjustable, such as... Figure 4 As shown. The change in transmittance allows the system to dynamically adjust the amount of light entering the optical lens group (4) and projected onto the image sensor (7) according to the actual lighting conditions. The control processing center (8) identifies the highlight area and analyzes the strong light path distribution through the highlight recognition algorithm based on the raw image data information provided by the image sensor (7), calculates the optimal aperture transmittance distribution of the front variable aperture group (3) and the rear variable aperture group (5), and sends the instruction to the variable aperture controller (6) to make corresponding adjustments to the front variable aperture group (3) and the rear variable aperture group (5) so that the transmittance distribution of each aperture is adjusted to the calculated optimal transmittance distribution. This method can avoid overexposure while maintaining image details, thereby improving the overall imaging quality.

[0023] Example 5: In this example, the rear variable aperture group (5) adopts a design that combines a variable aperture and a liquid crystal spatial light modulator (902), such as Figure 5As shown. After the control processing center (8) obtains the distribution of the highlight area and the distribution of the strong light path by analyzing the original image data, it calculates the optimal strong light dispersion area of ​​the liquid crystal spatial light modulator (902) in the rear variable aperture group (5), and controls the liquid crystal spatial light modulator (902) in the rear variable aperture group (5) through the variable aperture controller (6) to adjust the strong light dispersion area (903) to the calculated optimal area. This combination not only allows for traditional aperture adjustment, but also further disperses the strong light through the liquid crystal optical element, making the projection of the strong light on the image sensor (7) more dispersed, thereby reducing the risk of local overexposure and improving the contrast between the target object (2) and the strong light background (1). In addition, by precisely calculating the adjustment parameters of the liquid crystal spatial light modulator (902) and fusing it with the original image and the new image, a detailed and high-quality image can be obtained.

[0024] The working principle of this invention is analyzed in detail below: Because this imaging system has a certain degree of symmetry, for ease of understanding, we will simplify its working principle into a two-dimensional planar form for explanation, as follows: Figure 6 As shown. By adjusting the aperture center position, shape, size, and transmittance distribution of the front variable aperture group (3) and the rear variable aperture group (5), the strong light is partially or completely blocked, thereby increasing the imaging contrast between the target object (2) and the strong light background (1) on the final image sensor (7), and realizing the restoration of the details lost by the target object (2) due to the strong light background (1).

[0025] The following is the derivation of the basic formula for strong light filtering, and the process is as follows: Figure 7 As shown, the formulas for orthogonal planes are similar: First, determine the positions of the object and its image. Then, use the object-image relationship formula. and This yields the two-dimensional coordinates of the object and its image. Let x be the x-coordinate of the object. The vertical coordinate of the object Let x be the x-coordinate of the image. Let be the ordinate of the image. Let be the focal length of the optical lens group (4). Then, calculate the luminous flux of light rays transmitted from the object space to the optical lens group (4). Assume that the front variable stop group (3) contains a variable stop. , The ordinates of the upper and lower boundaries of the nth aperture region are respectively , The angular interval subtended by the object in this region is obtained. ,in for The abscissa. Similarly, the angular range of the object-pair optical lens group (4) can be obtained. .use This represents the sum of the angles at which the object light rays travel to the lens group (the length of the interval is expressed in absolute value; subsequent formulas follow the same principle). Indicating the intensity of light from an object, the luminous flux of light rays transmitted from the object space to the optical lens group (4) is: The next step is to calculate the luminous flux transmitted from the image space to the image sensor (7). It is assumed that the rear variable aperture group (5) contains two variable apertures. , As mentioned above, the angular range of the image pair optical lens group (4) is calculated. Like to The angular interval of the nth aperture region Like to The angular interval of the nth aperture region And like the cause The angular interval of the dark region created by the nth group of aperture regions blocking light. The luminous flux transmitted from the image space to the image sensor is then... Next, the distribution of light rays on the image sensor (7) is calculated. From the formula for collinearity of three points, we have... , The coverage area of ​​the image when there is no aperture on the image sensor (7) is obtained. ,in and These are the ordinates of the lower and upper boundaries of the covered area, respectively. It is half the diameter of the lens. Let x be the x-coordinate of the plane where the sensor receives the image. Similarly, find the factor... , , The nth aperture region blocks the light-free area on the image sensor (7). , , The distribution range of light on the image sensor is then... Finally, the luminous flux per unit length of light on the image sensor (7) was calculated. Through the above derivation, the luminous flux per unit length of light on the image sensor (7) was obtained. .

[0026] The specific working process of a preferred embodiment is as follows: The front variable aperture group (3) and the rear variable aperture group (5) are each driven by a four-channel voltage, as shown in the top view. Figure 8As shown. This four-channel voltage-driven liquid crystal variable aperture device consists of an upper polarizer, an upper glass substrate, a liquid crystal layer, a lower glass substrate, and a lower polarizer. Strip-shaped metal or indium tin oxide (ITO) electrodes are deposited at both ends of each transparent glass substrate, and the remaining parts are coated with a high-impedance film with a sheet resistance of 104~106 Ω / sq. The two transparent substrates are vertically stacked to form a liquid crystal variable aperture with a rectangular light-passing aperture. By changing the amplitude, frequency, and initial phase of the input voltage on the four electrodes, the average electric field distribution in the effective area is changed, thereby controlling the arrangement and distribution of liquid crystal molecules. Let the electrode channels at both ends of the upper glass substrate be CH1 and CH2, and the electrode channels at both ends of the lower glass substrate be CH3 and CH4. First, initialize the front variable aperture group (3) and the rear variable aperture group (5), that is, each aperture group is in the maximum light-passing state. After initialization, align the imaging system with the target object (2) and adjust the focal length of the optical lens group (4) so ​​that the image sensor (7) obtains a clear original image, such as Figure 11 As shown, the original image data is transmitted to the control processing center (8). After receiving the original image data, the control processing center (8) analyzes it using a highlight detection program to obtain the highlight area distribution and calculate the strong light path and the optimal center position, shape, size, and transmittance distribution of each aperture. Subsequently, the control processing center (8) uses a variable aperture controller (6) to adjust the frequency, voltage, phase, and other parameters of the applied electric field of the four electrodes (904), changing the arrangement of liquid crystal molecules in the liquid crystal distribution area (905) until the center position, shape, size, and transmittance distribution of the aperture are the same as the calculated optimal center position, shape, size, and transmittance distribution, such as... Figure 9 and Figure 10 As shown, these are the apertures adjusted by the front variable aperture group (3) and the rear variable aperture group (5), respectively. CH1 in the front variable aperture group (3) has an amplitude of 10V, a frequency of 1000Hz, and a phase of... CH2: Amplitude 10V, Frequency 1000Hz, Phase CH3: Amplitude 10V, Frequency 2000Hz, Phase CH4: Amplitude 10V, Frequency 2000Hz, Phase CH1 in the rear variable aperture group (5): amplitude 9V, frequency 1000Hz, phase CH2: Amplitude 11V, Frequency 1000Hz, Phase CH3: Amplitude 9V, Frequency 2000Hz, Phase CH4: Amplitude 11V, Frequency 2000Hz, Phase After completing the above operations, the image sensor (7) acquires a new image, such as... Figure 12As shown, the new image data is transmitted to the control processing center (8). The control processing center (8) compares and fuses the new image with the original image to finally generate an image with good detail information, such as... Figure 13 As shown.

[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. A strong light background imaging system based on a variable aperture, characterized in that: It includes a front variable aperture group, an optical lens group, a rear variable aperture group, a variable aperture controller, an image sensor, and a control processing center.

2. The imaging system according to claim 1, characterized in that: The aforementioned front variable aperture group is located between the target object and the optical lens group.

3. The imaging system according to claim 1, characterized in that: The aforementioned rear variable aperture group is located between the optical lens group and the image sensor.

4. The imaging system according to claim 1, characterized in that: The variable aperture can adjust the center position, shape, size, and transmittance distribution of the aperture in real time.

5. The imaging system according to claim 1, characterized in that: The front and rear variable aperture groups are connected to the variable aperture controller, and the variable aperture controller and the image sensor are connected to the control processing center.

6. The imaging system according to claim 3, characterized in that: The rear variable aperture group contains one or more variable apertures.

7. The imaging system according to claim 6, characterized in that: The rear variable aperture group can adopt a structure combining a variable aperture and a liquid crystal spatial light modulator.

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