Cmos image sensor, cmos camera and high dynamic range cmos camera imaging method

Abstract

The application provides a CMOS image sensor, a CMOS camera and a high dynamic range CMOS camera imaging method, and aims to solve the technical problems of low noise process and pixel size optimization of the CMOS image sensor, long process, complex process and large cost investment. The CMOS image sensor comprises a coated window and an uncoated window; the coated window is coated with a layer of fluorescent material, the coated window is used for receiving light emitted by the fluorescent material, and the uncoated window is used for receiving light of a photographed object. The CMOS camera comprises the CMOS image sensor, the area proportion of the fluorescent material coated by the CMOS image sensor and the attenuation coefficients of different fluorescent materials, and the dynamic range is flexibly adjusted by cooperating with corresponding secondary exposure and data reading mode.

Description

Technical Field

[0001] This invention relates to a CMOS camera, specifically to a CMOS image sensor, a CMOS camera, and a high dynamic range CMOS camera imaging method. Background Technology

[0002] CMOS cameras, with their advantages of high integration, high frame rate, and low cost, currently dominate the digital camera market. Dynamic range is one of the most important indicators of CMOS image sensors and CMOS cameras, and high dynamic range is a goal that CMOS cameras constantly strive for. Dynamic range is defined as the ratio of the maximum light intensity signal to the minimum light intensity signal that a CMOS image sensor can detect. Increasing the upper detection limit and decreasing the lower detection limit are the two main ways to increase dynamic range. Existing technologies mainly achieve a low lower detection limit by optimizing the process and reducing CMOS image sensor noise, while the upper detection limit is mainly improved by increasing the effective pixel size and increasing the full-well charge.

[0003] The low-noise process and pixel size optimization of existing CMOS image sensors are complex, time-consuming, and require significant investment. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problems that the low-noise process and pixel size optimization of existing CMOS image sensors are complex, time-consuming, and require a large investment. The invention provides a CMOS image sensor, a CMOS camera, and a high dynamic range CMOS camera imaging method, which significantly improves the dynamic range of the CMOS camera through simple process adjustments.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] A CMOS image sensor, which is special in that:

[0007] The photosensitive window includes a coated window and an uncoated window; the area ratio of the coated window to the uncoated window is K:1, where K>0.

[0008] The coated window is coated with a fluorescent material. The coated window is used to receive the light emitted by the fluorescent material, while the uncoated window is used to receive the light from the photographed object.

[0009] Furthermore, K = 1.

[0010] Furthermore, the coated window includes a plurality of coated pixel windows, and the uncoated window includes a plurality of uncoated pixel windows;

[0011] Each coated pixel window and each uncoated pixel window are arranged alternately in each row and each column.

[0012] A CMOS camera that is special in that:

[0013] This includes the aforementioned CMOS image sensor.

[0014] A high dynamic range CMOS camera imaging method, characterized by the following steps:

[0015] S1) Coating a fluorescent material onto the window portion of the photosensitive surface of the CMOS image sensor in a CMOS camera;

[0016] S2) The CMOS camera shutter opens, and the subject is exposed for the first time; the exposure time is t1.

[0017] S3) The CMOS camera shutter is closed. After the first exposure, a time interval T is elapsed before a second exposure and data readout. The exposure time is t2. The residual light intensity Q of the phosphor is obtained. t ;

[0018] S4) Calculate the original light intensity of the photographed object Q0 = Q t (K+1) / (kqK), then return to step S2 to perform imaging of the next frame; where K is the ratio of the coated window area to the uncoated window area of ​​the CMOS image sensor, q is the light intensity conversion coefficient of the fluorescent material, and k is the attenuation coefficient of the fluorescent material. The attenuation coefficient k of the same fluorescent material is a fixed value.

[0019] Furthermore, increasing K can extend the upper limit of the dynamic range detection of CMOS cameras.

[0020] Reducing K expands the lower limit of the dynamic range detection of CMOS cameras;

[0021] Alternatively, choosing a fluorescent material with a smaller k-value can extend the detection limit of the dynamic range of a CMOS camera.

[0022] Furthermore, increasing t1 can extend the lower limit of the dynamic range detection of CMOS cameras.

[0023] Increasing T and / or t2 can extend the detection limit of the dynamic range of CMOS cameras.

[0024] A high dynamic range CMOS camera imaging method, characterized by the following steps:

[0025] S1) Coating a fluorescent material onto the window portion of the photosensitive surface of the CMOS image sensor in a CMOS camera;

[0026] S2) The CMOS camera shutter opens, the object is exposed for the first time and the data is read out. The exposure time is t1, and the total light intensity Q of the object and phosphor is obtained.

[0027] S3) When the CMOS camera shutter is closed, determine whether the total light intensity Q is greater than the detection limit of the CMOS image sensor. If not, proceed to step S4; if yes, proceed to step S5.

[0028] S4) Calculate the original light intensity of the photographed object Q0 = Q(K+1) / (1+qK), and then return to step S2 to perform imaging of the next frame; where K is the ratio of the coated window area to the uncoated window area of ​​the CMOS image sensor, and q is the light intensity conversion coefficient of the fluorescent material.

[0029] S5) After the first exposure, a second exposure and data readout are performed after an interval T. The exposure time is t2, and the residual light intensity Q of the phosphor is obtained. t ;

[0030] S6) Calculate the original light intensity of the photographed object Q0 = Q t (K+1) / (kqK), then return to step S2 to perform imaging of the next frame; where k is the attenuation coefficient of the fluorescent material, and the attenuation coefficient k of the same fluorescent material is a fixed value.

[0031] Furthermore, increasing K can extend the upper limit of the dynamic range detection of CMOS cameras.

[0032] Reducing K expands the lower limit of the dynamic range detection of CMOS cameras;

[0033] Alternatively, choosing a fluorescent material with a smaller k-value can extend the detection limit of the dynamic range of a CMOS camera.

[0034] Furthermore, increasing t1 can extend the lower limit of the dynamic range detection of CMOS cameras.

[0035] Increasing T and / or t2 can extend the detection limit of the dynamic range of CMOS cameras.

[0036] The advantages of this invention compared to the prior art are as follows:

[0037] 1. The CMOS camera provided by the present invention improves the detection limit of the CMOS image sensor and enhances the dynamic range of the CMOS camera by performing a simple process on the basis of a conventional CMOS image sensor, namely coating a portion of the window with a fluorescent material.

[0038] 2. The high dynamic range CMOS camera imaging method provided by the present invention flexibly adjusts the dynamic range of the CMOS camera by using the area ratio of the fluorescent material coated on the CMOS image sensor and the attenuation coefficient of different fluorescent materials, as well as the corresponding secondary exposure and data readout methods, thereby greatly expanding the dynamic range of the CMOS camera. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the pixel structure of a CMOS image sensor according to the present invention;

[0040] Figure 2 This is a flowchart illustrating an embodiment of a high dynamic range CMOS camera imaging method according to the present invention;

[0041] Figure 3 This is a light intensity decay curve of a fluorescent material in an embodiment of a high dynamic range CMOS camera imaging method of the present invention (t0 is the time point when the illumination ends, t1 is the time point when the second exposure begins, and Δt is the duration of the second exposure). Detailed Implementation

[0042] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0043] This invention achieves a significant improvement in the dynamic range of a CMOS camera by coating a layer of fluorescent material onto the window of the photosensitive surface of the CMOS image sensor, combined with a double-exposure imaging method and a dynamic range extension algorithm.

[0044] An embodiment of the present invention provides a CMOS image sensor, such as... Figure 1 As shown, the biggest difference from existing CMOS image sensors is that the photosensitive surface of a CMOS image sensor is coated with a layer of fluorescent material, resulting in coated and uncoated windows. The coated windows are used to receive light emitted by the fluorescent material, while the uncoated windows are used to receive light from the photographed object. When the fluorescent material is illuminated, it emits light of a certain wavelength. After the illumination disappears, the fluorescence does not disappear immediately but gradually weakens until it disappears completely.

[0045] The present invention also provides a CMOS camera, including the above-described CMOS image sensor.

[0046] like Figure 2The diagram shows a flowchart of a high dynamic range CMOS camera imaging method according to the present invention. After the CMOS camera is turned on for exposure and the shutter is opened, a first exposure and data readout are performed. At this time, the CMOS camera collects the sum of the light from the object being photographed and the light emitted by the phosphor. With the camera shutter closed, a second exposure and data readout are performed, this time collecting the residual light from the phosphor. Since the relationship between the attenuation and delay of residual light for the same phosphor is fixed, the light intensity value during the first exposure can be calculated based on the exposure delay and the magnitude of the residual light from the phosphor. If the light intensity does not exceed the detection limit of the CMOS image sensor, the data read out after the first exposure can be directly used as the light intensity of the object being photographed. If the light intensity exceeds the detection limit of the CMOS image sensor, causing threshold saturation and preventing accurate reading of the light intensity during the first exposure, the data read out after the second exposure is used, divided by the attenuation coefficient, to calculate the light intensity of the object being photographed. By combining the two exposures, the detection limit of the CMOS image sensor can be greatly expanded, improving the dynamic range of the CMOS camera.

[0047] The ratio of the coated window area to the uncoated window area in a CMOS image sensor is K:1. The formula for calculating the original light intensity of the photographed object based on the data read after the first exposure is as follows:

[0048] Q0 = Q(K+1) / (1+qK)

[0049] Where Q0 is the input original light intensity value, Q is the light intensity value collected during the first exposure (including the light intensity of the coated window and the uncoated window), and q is the light intensity conversion coefficient of the fluorescent material.

[0050] The formula for calculating the original light intensity of the photographed object using the data read from the second exposure is:

[0051] Q0 = Q t (K+1) / (kqK)

[0052] Q t The light intensity is the light intensity collected during the second exposure, and k is the attenuation coefficient of the fluorescent material, which is a fixed value determined by the process parameters.

[0053] This novel structure reduces data volume by performing a judgment after the first exposure and data readout before deciding whether to perform a second exposure. The readout data is compared to the CMOS saturation threshold. If the CMOS is not saturated, a second exposure is not required, and the process proceeds directly to the next frame. If the readout data exceeds the saturation threshold, a second exposure is initiated, followed by a second data readout and storage. Only after all these steps are completed does the next frame acquisition operation begin.

[0054] An imaging method for a high dynamic range CMOS camera is as follows:

[0055] A fluorescent material is coated onto the photosensitive window portion of a CMOS image sensor. The upper limit of the dynamic range of the CMOS camera is determined by the attenuation coefficient of the fluorescent material, and the lower limit of the dynamic range is determined by the area ratio of the coated window to the uncoated window. The lower limit of the dynamic range of the CMOS camera is determined by the area ratio of the coated window to the uncoated window of the CMOS image sensor, and this ratio is inversely proportional to the lower limit of the dynamic range. The upper limit of the dynamic range of the CMOS camera is determined by the attenuation coefficient of the fluorescent material, and this ratio is also inversely proportional to the upper limit of the dynamic range. The area ratio of the coated window to the uncoated window of the CMOS image sensor is K:1, and this ratio is determined by process parameters.

[0056] in:

[0057] Given a fixed pixel size, increasing the proportion of the area occupied by the uncoated window can expand the upper limit of the CMOS image sensor's detection range; conversely, it can expand the lower limit of the CMOS image sensor's detection range, which is greater than the lower limit of the CMOS image sensor without fluorescent coating.

[0058] Alternatively, if the frame rate requirement is met, selecting a fluorescent material with a smaller attenuation coefficient can extend the detection limit of the CMOS image sensor.

[0059] like Figure 3 As shown, the fluorescence intensity is Q at time t0 immediately after the illumination ends. t The light intensity Q at time t t =k·Q t0 For fluorescent materials, the attenuation coefficient k is a fixed value at each time step. During the second exposure, the light intensity collected at time t is used. Based on the attenuation coefficient and the time interval, the fluorescence intensity Q0 = Q at time t0 can be calculated. t / k.

[0060] After the CMOS camera shutter opens, the first exposure and data readout are performed. At this time, the camera collects the sum of the light from the target object and the light emitted by the phosphor.

[0061] The light intensity acquired in the first exposure is Q, which includes the light intensity of the coated and uncoated areas. The light intensity conversion coefficient of the fluorescent material is q, and the original light intensity input to the entire pixel is Q0.

[0062] Q = Q0 / (K+1) + qQ0K / (K+1)

[0063] In the above formula, K and q are fixed values ​​determined based on material and process parameters. Using Q0, K and q, the original light intensity of the entire input pixel portion is calculated as Q0 = Q(K+1) / (1+qK).

[0064] After the camera shutter closes, a second exposure and data readout are performed, at which point the residual light from the phosphor is collected; the intensity Q of the second light sample is measured. t The attenuation coefficient k of the fluorescent material is a fixed value, determined by the process parameters. Therefore, Q... t =kqQ0K / (K+1);

[0065] The original light intensity Q0 = (K+1) / (kqK) of the entire input pixel portion can then be calculated.

[0066] Furthermore, the dynamic range of a CMOS sensor can also be adjusted by changing the interval and duration of the two exposures. Adjusting the length of the first exposure adjusts the lower detection limit of the CMOS device; adjusting the interval and duration of the second exposure adjusts the upper detection limit. Increasing the length of the first exposure results in a better lower detection limit. Within the time frame before the fluorescence has completely decayed, maximizing the interval and duration of the second exposures yields a better upper detection limit. Within a certain range, increasing both the first and second exposure times, along with the interval and duration of the second exposures, can achieve a higher dynamic range.

[0067] When coating a fluorescent material onto the photosensitive window of a CMOS image sensor, one pixel's window can be coated with fluorescent material, while adjacent pixels can use the conventional method of not coating with fluorescent material. The area ratio of the coated window to the uncoated window is 1:1 and they are distributed as follows:

[0068] A coated window includes multiple coated pixel windows, and an uncoated window includes multiple uncoated pixel windows. The coated pixel windows and the uncoated pixel windows are arranged alternately in each row and each column.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. For those skilled in the art, modifications can be made to the specific technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. However, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions protected by the present invention.

Claims

1. A CMOS image sensor, comprising a photosensitive window, characterized in that: The photosensitive window includes a coated window and an uncoated window; the area ratio of the coated window to the uncoated window is K:1, K > 0; The coated window is coated with a fluorescent material. The coated window is used to receive the light emitted by the fluorescent material, while the uncoated window is used to receive the light from the photographed object.

2. The CMOS image sensor according to claim 1, characterized in that: K=1.

3. The CMOS image sensor according to claim 2, characterized in that: The coated window includes multiple coated pixel windows, and the uncoated window includes multiple uncoated pixel windows; Each coated pixel window and each uncoated pixel window are arranged alternately in each row and each column.

4. A CMOS camera, characterized in that: Includes the CMOS image sensor described in any one of claims 1-3.

5. A high dynamic range CMOS camera imaging method, characterized in that, Includes the following steps: S1) Coating a fluorescent material onto the photosensitive window portion of the CMOS image sensor in a CMOS camera; S2) The CMOS camera shutter opens, and the subject is exposed for the first time; the exposure time is t1. S3) The CMOS camera shutter is closed. After the first exposure, a time interval T is elapsed before a second exposure and data readout. The exposure time is t2. The residual light intensity Q of the phosphor is obtained. t ; S4) Calculate the original light intensity of the photographed object Q0=Q t (K+1) / ((kqK)), then return to step S2 to perform imaging of the next frame; where K is the ratio of the coated window area to the uncoated window area of ​​the CMOS image sensor, q is the light intensity conversion coefficient of the fluorescent material, and k is the attenuation coefficient of the fluorescent material, k is a fixed value.

6. The high dynamic range CMOS camera imaging method according to claim 5, characterized in that: Increasing K expands the upper limit of the dynamic range detection of CMOS cameras. Reducing K expands the lower limit of the dynamic range detection of CMOS cameras.

7. The high dynamic range CMOS camera imaging method according to claim 5 or 6, characterized in that: Increasing t1 expands the lower limit of the dynamic range detection of CMOS cameras. Increasing T and / or t2 can extend the detection limit of the dynamic range of CMOS cameras.

8. An imaging method for a high dynamic range CMOS camera, characterized in that, Includes the following steps: S1) Coating a fluorescent material onto the photosensitive window portion of the CMOS image sensor in a CMOS camera; S2) The CMOS camera shutter opens, the object is exposed for the first time and the data is read out. The exposure time is t1, and the total light intensity Q of the object and phosphor is obtained. S3) When the CMOS camera shutter is closed, determine whether the total light intensity Q is greater than the detection limit of the CMOS image sensor. If not, proceed to step S4; if yes, proceed to step S5. S4) Calculate the original light intensity of the photographed object Q0=Q(K+1) / (1+qK), and then return to step S2 to perform imaging of the next frame; where K is the ratio of the coated window area to the uncoated window area of ​​the CMOS image sensor, and q is the light intensity conversion coefficient of the fluorescent material. S5) After the first exposure, a second exposure and data readout are performed after an interval T. The exposure time is t2, and the residual light intensity Q of the phosphor is obtained. t ; S6) Calculate the original light intensity of the photographed object Q0=Q t (K+1) / (kqK), then return to step S2 to perform imaging of the next frame; where k is the attenuation coefficient of the fluorescent material and k is a fixed value.

9. The high dynamic range CMOS camera imaging method according to claim 8, characterized in that: Increasing K expands the upper limit of the dynamic range detection of CMOS cameras. Reducing K expands the lower limit of the dynamic range detection of CMOS cameras.

10. The high dynamic range CMOS camera imaging method according to claim 8 or 9, characterized in that: Increasing t1 expands the lower limit of the dynamic range detection of CMOS cameras. Increasing T and / or t2 can extend the detection limit of the dynamic range of CMOS cameras.

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