CN116782043A - Image signal amplifying circuit and corresponding image signal amplifying method - Google Patents

Abstract

The application provides an image signal amplifying circuit and a related method. The image signal amplifying circuit comprises an amplifier and a gain control circuit, wherein the amplifier is configured to amplify a first image signal and a second image signal generated by a pixel array of the image sensor, each pixel circuit of the pixel array comprises a first capacitor and a second capacitor, and the charge storage capacity of the first capacitor is smaller than the charge storage capacity of the second capacitor; the gain control circuit is coupled to the amplifier and configured to selectively set the first analog gain to one of a first gain value and a second gain value, or to selectively set the second analog gain to one of a third gain value and a fourth gain value; wherein each pixel circuit has a first conversion gain corresponding to the first capacitance and a second conversion gain corresponding to the second capacitance; wherein the first conversion gain and the second conversion gain are fixed values. The image signal amplifying circuit and the related method can adjust the gain of the sensor according to different requirements.

Description

Image signal amplifying circuit and corresponding image signal amplifying method

[ field of technology ]

The present application relates to image processing. More particularly, the present application relates to a circuit and method for image signal amplification.

[ background Art ]

Conventional cameras have an image sensor for sensing an image. However, the human eye can perceive a higher dynamic range than the image sensor. A single exposure of the image sensor cannot cover both dark and light areas. Details of the dark areas of the image may be lost due to noise. Furthermore, details of bright areas of the image may be lost due to saturation of the image pixels.

To solve this problem, a high dynamic range imaging (High Dynamic Range Imaging, abbreviated HDR) method has been developed which captures images with different exposure conditions at different times and fuses the images to generate a fused image. However, this method may have a problem of image ghosting (image ghosting) due to the object moving when an image is photographed. Therefore, in order to solve the image ghost problem, a dual conversion gain (dual conversion gain) image sensor has been developed, which has two conversion gains and captures two images at one exposure. However, the conversion gain of the conversion gain image sensor is fixed, and thus the ratio between the conversion gains is also fixed. Accordingly, the dynamic range of the fusion image generated from the image captured by the dual conversion gain image sensor is also fixed.

[ application ]

In view of the foregoing, an image signal amplifying circuit and related method are provided. The following summary is illustrative only and is not intended to be in any way limiting. That is, the following summary is provided to introduce a selection of concepts, emphasis, benefits, and advantages of the novel and non-obvious techniques described herein. The selection and not all implementations will be further described in the detailed description below. Thus, the following summary is not intended to identify essential features of the claimed subject matter, nor is it intended to be used to determine the scope of the claimed subject matter.

Some embodiments of the present disclosure provide an image signal amplifying circuit including: an amplifier configured to amplify a first image signal with a first analog gain and amplify a second image signal with a second analog gain, wherein the first image signal and the second image signal are generated by a pixel array of the image sensor, wherein each pixel circuit of the pixel array comprises a first capacitance generating the first image signal and a second capacitance generating the second image signal, wherein a charge storage capacity of the first capacitance is smaller than a charge storage capacity of the second capacitance; and a gain control circuit coupled to the amplifier and configured to selectively set the first analog gain to one of a first gain value and a second gain value, or to selectively set the second analog gain to one of a third gain value and a fourth gain value, wherein the first gain value is greater than the second gain value and the third gain value is greater than the fourth gain value; wherein each pixel circuit has a first conversion gain corresponding to the first capacitance and a second conversion gain corresponding to the second capacitance; wherein the first conversion gain and the second conversion gain are fixed values.

Some embodiments of the present disclosure also provide an image signal amplifying circuit including: an amplifier configured to amplify a first image signal and amplify a second image signal generated by a pixel array of the image sensor with a first analog gain, wherein a brightness of a dark image corresponding to the first image signal is lower than a brightness of a bright image corresponding to the second image signal, wherein the dark image and the bright image are generated by only one exposure of the image sensor; and a gain control circuit coupled to the amplifier and configured to selectively set the first analog gain to one of a first gain value and a second gain value, or to selectively set the second analog gain to one of a third gain value and a fourth gain value, wherein the first gain value is greater than the second gain value and the third gain value is greater than the fourth gain value; wherein each pixel circuit in the pixel array has a first conversion gain corresponding to a dark image and a second conversion gain corresponding to a bright image, wherein the first conversion gain and the second conversion gain are fixed values.

Some embodiments of the present disclosure also provide an image signal amplifying method, including: (a) amplifying the first image signal with a first analog gain; (b) Amplifying a second image signal with a second analog gain, wherein the first image signal and the second image signal are generated by a pixel array of the image sensor, wherein each pixel circuit of the pixel array comprises a first capacitor that generates the first image signal and a second capacitor that generates the second image signal, wherein a charge storage capacity of the first capacitor is less than a charge storage capacity of the second capacitor; and (c) selectively setting the first analog gain to one of a first gain value and a second gain value, or selectively setting the second analog gain to one of a third gain value and a fourth gain value, wherein the first gain value is greater than the second gain value and the third gain value is greater than the fourth gain value; each pixel circuit has a first conversion gain corresponding to the first capacitance and a second conversion gain corresponding to the second capacitance.

The image signal amplifying circuit and the related method can adjust the output image according to the actual requirement.

[ description of the drawings ]

The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this disclosure. The drawings illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the disclosure. It will be appreciated that the figures are not necessarily to scale, as certain components may be shown out of scale in actual implementation in order to clearly illustrate the concepts of the disclosure.

Fig. 1 is a schematic diagram of an image signal amplifying circuit according to an embodiment of the present application.

Fig. 2 is a gain combination diagram of conversion gain and analog gain according to one embodiment of the application.

Fig. 3 is a schematic view of a luminance distribution and a fused image of the image shown in fig. 2 according to one embodiment of the present application.

Fig. 4 is a schematic diagram of varying gain combinations according to light conditions according to one embodiment of the application.

Fig. 5 is a schematic diagram showing a combination of conversion gain and analog gain according to another embodiment of the present application.

Fig. 6 is a flowchart illustrating an image signal amplifying method according to an embodiment of the present application.

[ detailed description ] of the application

It will be readily understood that the components of the present application, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the systems and methods of the present application, as represented in the figures, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application.

Reference throughout this specification to "one embodiment," "some embodiments," or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. Thus, appearances of the phrases "in one embodiment" or "in some embodiments" in various places throughout this specification are not necessarily all referring to the same embodiment, which may be implemented alone or in combination with one or more other embodiments. Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize, however, that the application may be practiced without one or more of the specific details, or with other methods, components, etc. In other instances, well-known structures or operations are not shown or described. Detailed description to avoid obscuring aspects of the application.

In the following description, several embodiments are provided to explain the inventive concept. It should be understood that the terms "first," "second," and "third" in the following description are merely used to distinguish between different elements and do not indicate a sequential order of the elements. For example, the first device and the second device only indicate that these devices may have the same structure but are different devices.

Fig. 1 is a schematic diagram of an image signal amplifying circuit 105 according to one embodiment of the present application. The image sensor 100 in fig. 1 includes a pixel array 101, a reading circuit 103, an image signal amplifying circuit 105, and an ADC107. The pixel array 101 includes a plurality of pixel circuits that generate a sensing charge corresponding to received light. The reading circuit 103 is configured to read the electric charges to generate an image signal corresponding to the sensing electric charges generated by the pixel circuit. In one embodiment, the image sensor 100 IS a dual conversion gain image sensor, so each pixel circuit of the pixel array 101 includes a first capacitor generating the first image signal is_1 and a second capacitor generating the second image signal is_2. The charge storage capacity of the first capacitor is smaller than the charge storage capacity of the second capacitor. The pixel circuit has a first conversion gain corresponding to the first capacitance and a second conversion gain corresponding to the second capacitance. The first conversion gain is higher than the second conversion gain. In one embodiment, the first conversion gain and the second conversion gain are related to the charge storage capacity of the first capacitor and the second capacitor and are therefore fixed values.

In one embodiment, the first capacitance and the second capacitance are both physical capacitive elements. However, the first capacitance or the second capacitance may refer to a parasitic capacitance of an electronic element such as a transistor. Such a construction is disclosed, for example, in U.S. patent application No. US 20170148832. The configuration of the first and second capacitors may be varied according to different needs.

The image signal amplification circuit 105 includes an amplifier 105_1 and a gain control circuit 105_2. The amplifier 105_1 amplifies the first image signal is_1 with a first analog gain to generate a first amplified image signal ais_1, and amplifies the second image signal is_2 with a second analog gain to generate a second amplified image signal ais_2. The first analog gain and the second analog gain may be the same, but may also be different. The gain control circuit 105_2 is coupled to the amplifier 105_1 for adjusting the first analog gain or the second analog gain. In other words, the gain control circuit 105_2 is configured to selectively set the first analog gain to one of the first gain value and the second gain value, or to selectively set the second analog gain to one of the third gain value and the fourth gain value. In one embodiment, the first gain value is greater than the second gain value and the third gain value is greater than the fourth gain value. Further, in one embodiment, the first gain value is equal to the third gain value and the second gain value is equal to the fourth gain value.

As described above, the first analog gain IS used to amplify the first image signal is_1 from the first capacitor corresponding to the higher first conversion gain, and the second analog gain IS used to amplify the second image signal is_2 from the second capacitor corresponding to the lower second conversion gain. Accordingly, the gain control circuit 105_2 is configured to set the analog gain of the amplifier 105_1 so that the image sensor 100 may have different gain combinations. Each gain combination is made up of a conversion gain and an analog gain.

Please refer to fig. 1 again. In one embodiment, the amplified first image signal ais_1 and the amplified second image signal ais_2 are transferred to the ADC107 to generate digital image signals dis_1, dis_2. The digital image signals dis_1, dis_2 may be transferred to an image signal processor 109 (Image Signal Processor, abbreviated ISP), and the ISP 109 generates images corresponding to the amplified first image signal ais_1 and the amplified second image signal ais_2. In one embodiment, the digital image signals DIS_1, DIS_2 may be further processed before being received by ISP 109. For example, a black level calibration (black level calibration) and digital gain adjustment (digital gain tuning) may be performed before the digital image signals dis_1, dis_2 are processed by the ISP 109. However, the operation of processing the amplified first image signal ais_1 and the amplified second image signal ais_2 to generate an image may be different depending on the different structures of the image sensor.

Fig. 2 is a gain combination diagram of conversion gain and analog gain according to one embodiment of the application. The gain combination c_1 comprises a first conversion gain cg_1 (H) and a first analog gain having a first gain value ag_11 (H). The gain combination c_2 comprises a first conversion gain cg_1 (H) and a first analog gain having a second gain value ag_12 (L). The gain combination c_3 includes a second conversion gain cg_2 (L) and a second analog gain having the third gain value ag_23 (H) described above. The gain combination c_4 includes a second conversion gain cg_2 (L) and a second analog gain having the fourth gain value ag_24 (L) described above.

As described above, the first conversion gain cg_1 (H) is higher than the second conversion gain cg_2 (L). Furthermore, the first analog gain with the first gain value ag_11 (H) is higher than the first analog gain with the second gain value ag_12 (L), while the second analog gain with the third gain value ag_23 (H) is higher than the second analog gain with the fourth gain value ag_24 (L). Further in an embodiment, the first analog gain with the first gain value ag_11 (H) is equal to the second analog gain with the third gain value ag_23 (H), and the first analog gain with the second gain value ag_12 (L) is equal to the second analog gain with the fourth gain value ag_24 (L).

Different gain combinations have different benefits. The gain combination c_1 may preserve details of the dark region. The gain combination c_2 can reduce noise in a dark area (improve image quality in the dark area). The gain combination c_3 may infer differences between noise of images generated based on different gain combinations (i.e., reduce noise of the fused image). The gain combination c_4 may reduce the number of saturated pixels of the bright image.

In one embodiment, the image sensor 100 generates at least two of a first image img_1 corresponding to the gain combination c_1, a second image img_2 corresponding to the gain combination c_2, a third image img_3 corresponding to the gain combination c_3, and a fourth image img_4 corresponding to the gain combination c_4. For example, when the first analog gain has the first gain value ag_11 (H), the first image img_1 corresponds to the digital image signal dis_1, and when the first analog gain has the second gain value ag_12 (L), the second image img_1 corresponds to the digital image signal dis_1. In addition, the image sensor or ISP may further include an image fusion circuit configured to fuse at least two of the first image img_1, the second image img_2, the third image img_3, and the fourth image img_4 to generate a fused image. For example, the image sensor 100 generates a first image img_1 and a third image img_3, and the fusion circuit generates a fusion image according to the first image img_1 and the third image img_3. For another example, the image sensor 100 generates the first image img_1, the second image img_2, the third image img_3, and the fourth image img_4, but the fusion circuit generates the fusion image based on only the first image img_1, the second image img_2, and the third image img_3.

Fig. 3 is a schematic view of a luminance distribution and a fused image of the image shown in fig. 2 according to one embodiment of the present application. As shown in fig. 3, the first image img_1 is the darkest image because it corresponds to the gain combination c_1 having the highest value. In contrast, the fourth image img_4 is the brightest image, because it corresponds to the gain combination c_4 having the lowest value. The second image img_2 and the third image img_3 also have different brightness distributions due to different gain combinations. Therefore, if the first image img_1 and the fourth image img_4 are used to generate the fused image img_f, the fused image has a large dynamic range. In addition, if the second image img_2 and the third image img_3 are used to generate the fused image, the image quality of the image is better. In one embodiment, the second image img_2 is used as the primary reference image during fusion because it has less noise than using the first image img_1.

Thus, the analog gain can be determined according to the desired image condition. For example, assuming that the fused image has a large dynamic range, a high analog gain (gain combination c_1) is set for a high conversion gain, and a low analog gain (gain combination c_4) is set for a low conversion gain. As another example, if a better image quality of the fused image is desired, a low analog gain (gain combination c_2) is set for the high conversion gain, and a high analog gain c_3 (gain combination c_2) is set for the low conversion gain.

In one embodiment, the analog gain may be automatically set according to a light condition (light condition) sensed by the image sensor. Fig. 4 is a schematic diagram of varying gain combinations according to light conditions according to one embodiment of the application. In the embodiment of fig. 4, the camera using the image sensor 100 moves from a high dynamic range scene (t=0) to a low dynamic range scene (t=1). In this case, the analog gain of the first conversion gain cg_1 (H) is adjusted from the first analog gain having the first gain value ag_11 (H) to the first analog gain having the second gain value ag_12 (L), because a large dynamic range is not required when t=1. In this way, noise of the fused image can be reduced while maintaining an appropriate dynamic range. In one embodiment, the operations shown in FIG. 4 are performed as the camera continuously records images. In another embodiment, the operations shown in fig. 4 are performed when the camera is continuously sensing an image but is not recording an image (e.g., the camera is operating in live view mode).

Further, in the above-described embodiment, the first analog gain may be set to one of two candidate gain values (e.g., a first gain value and a second gain value), and the second analog gain may be set to one of two candidate gain values (e.g., a third gain value and a fourth gain value). However, in one embodiment, the number of gain values may be more than two. Fig. 5 is a schematic diagram showing a combination of conversion gain and analog gain according to another embodiment of the present application. As shown in fig. 5, the first analog gain may be adjusted to one of at least three first analog gains having different gain values ag_1a, ag_1b, and ag_1c. Accordingly, the gain combination c_a1 includes the first conversion gain cg_1 (H) and the first analog gain having the first gain value ag_1a, the gain combination c_a2 includes the first conversion gain cg_1 (H) and the first analog gain having the second gain value ag_1b, and the gain combination c_a3 includes the first conversion gain cg_1 (H) and the first analog gain … having the fifth gain value ag_1c. Similarly, the second analog gain may be adjusted to one of at least three second analog gains having different gain values ag_2a, ag_2b, and ag_2c. Accordingly, the gain combination c_b1 includes the second conversion gain cg_2 (L) and the second analog gain having the third gain value ag_2a, the gain combination c_b2 includes the second conversion gain cg_2 (L) and the second analog gain having the fourth gain value ag_2b, and the gain combination c_b3 includes the second conversion gain cg_2 (L) and the second analog gain … having the sixth gain value ag_2c

Further, in the above-described embodiment, the analog gain of the first conversion gain cg_1 (H) or the analog gain of the second conversion gain cg_2 (L) may be adjusted. However, in another embodiment, only one of the analog gains of the first and second conversion gains cg_1 (H) and cg_2 (L) is adjustable, while the other analog gain is fixed. For example, the analog gain of the first conversion gain cg_1 (H) is adjustable, while the analog gain of the second conversion gain cg_2 (L) is fixed.

In addition, in view of the above description, the dual conversion gain image sensor may be replaced with an image sensor that generates a dark image (dark image) through a first conversion gain and a bright image (bright image) through a second conversion gain by only one exposure of the image sensor. The brightness of the dark image is lower than the brightness of the bright image. In this case, the first image signal corresponds to a dark image, and the second image signal corresponds to a bright image. Further, each pixel circuit of the pixel array has a first conversion gain corresponding to a dark image and a second conversion gain corresponding to a light image. Further, it should be appreciated that the image signal amplification circuit described above may be used in other applications and is not limited to fused images.

In summary, an image signal amplifying method is obtained. Fig. 6 is a flowchart illustrating an image signal amplifying method according to an embodiment of the present application. The image signal amplifying method includes:

step 601

The first image signal (e.g., the first image signal is_1 in fig. 1) IS amplified with a first analog gain.

Step 603

The second image signal (e.g., the second image signal is_2 in fig. 1) IS amplified with a second analog gain.

The first image signal and the second image signal are generated by a pixel array of the image sensor. Each pixel circuit in the pixel array includes a first capacitance for generating a first image signal and a second capacitance for generating a second image signal. The charge storage capacity of the first capacitor is smaller than the charge storage capacity of the second capacitor.

Each pixel circuit has a first conversion gain corresponding to the first capacitance and a second conversion gain corresponding to the second capacitance.

Step 605

The first analog gain is selectively set to one of a first gain value and a second gain value, or the second analog gain is selectively set to one of a third gain value and a fourth gain value. The first gain value is greater than the second gain value, and the third gain value is greater than the fourth gain value.

In other words, in one embodiment, either the first analog gain or the second analog gain is adjustable. In another embodiment, only one of the first analog gain and the second analog gain is adjustable.

If the image signal amplification method is adopted to generate the fusion image, the method can further comprise the following steps:

generating at least two of a first image, a second image, a third image, and a fourth image (e.g., first image img_1, second image img_2, third image img_3, and fourth image img_4 in fig. 3), wherein the first image corresponds to a first conversion gain and a first gain value, wherein the second image corresponds to a first conversion gain and a second gain value, wherein the third image corresponds to a second conversion gain and a third gain value, wherein the fourth image corresponds to a second conversion gain and a fourth gain value; and

at least two of the first image, the second image, the third image, and the fourth image are fused to generate a fused image.

Reference may be made to the above embodiments for further detailed steps, which are not described here again.

In view of the above embodiments, the analog gain of the image sensor can be adjusted to a suitable value according to different requirements. For example, the analog gain may be adjusted to increase dynamic range or improve image quality.

The present application may be embodied in other specific forms without departing from its spirit or essential characteristics. The described examples are to be considered in all respects only as illustrative and not restrictive. The scope of the application is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Ordinal terms such as "first," "second," and the like are used in the present disclosure and claims for descriptive purposes. It does not itself imply any order or relationship.

The steps of a method described in connection with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. Software modules (e.g., including executable instructions and associated data) and other data may reside in a data memory such as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of computer-readable storage medium known in the art. The sample storage medium may be coupled to a machine, such as a computer/processor (which may be referred to herein as a "processor" for convenience), such that the processor can read information (e.g., code) from, and write information to, the storage medium. The sample storage medium may be integrated into the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user equipment. In the alternative, the processor and the storage medium may reside as discrete components in a user device. Furthermore, in some aspects, any suitable computer program product may comprise a computer-readable medium comprising code relating to one or more aspects of the present disclosure. In some aspects, the computer software product may include packaging material.

It should be noted that although not explicitly stated, one or more steps of the methods described herein may include steps for storing, displaying and/or outputting as desired for a particular application. In other words, any data, records, fields, and/or intermediate results discussed in the method may be stored, displayed, and/or output to another device as desired for a particular application. While the foregoing is directed to embodiments of the present application, other and further embodiments of the application may be devised without departing from the basic scope thereof. The various embodiments presented herein, or portions thereof, may be combined to produce further embodiments. The above description is of the best mode contemplated for carrying out the application. This description is made for the purpose of illustrating the general principles of the application and should not be taken in a limiting sense. The scope of the application is best determined by reference to the appended claims.

The above paragraphs describe a number of aspects. It should be apparent that the teachings of the present application can be implemented in a variety of ways, and that any particular configuration or function in the disclosed embodiments represents only one representative case. Those skilled in the art will appreciate that all aspects disclosed in the present application may be applied independently or incorporated.

While the application has been described by way of example and preferred embodiments, it is to be understood that the application is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the scope and spirit of the application. The scope of the application should, therefore, be defined and protected by the following claims and their equivalents.

Claims (21)

1. An image signal amplifying circuit comprising:

an amplifier configured to amplify a first image signal with a first analog gain and amplify a second image signal with a second analog gain, wherein the first image signal and the second image signal are generated by a pixel array of an image sensor, wherein each pixel circuit of the pixel array comprises a first capacitance generating the first image signal and a second capacitance generating the second image signal, wherein a charge storage capacity of the first capacitance is smaller than a charge storage capacity of the second capacitance; and

gain control circuitry coupled to the amplifier and configured to selectively set the first analog gain to one of a first gain value and a second gain value, or to selectively set the second analog gain to one of a third gain value and a fourth gain value, wherein the first gain value is greater than the second gain value and the third gain value is greater than the fourth gain value;

each pixel circuit has a first conversion gain corresponding to the first capacitor and a second conversion gain corresponding to the second capacitor.

2. The image signal amplifying circuit according to claim 1, wherein the first conversion gain and the second conversion gain are fixed values.

3. The image signal amplifying circuit according to claim 1, wherein the first gain value is equal to the third gain value, and the second gain value is equal to the fourth gain value.

4. The image signal amplifying circuit according to claim 1, wherein the gain control circuit sets the first analog gain or the second analog gain according to the illumination sensed by the image sensor.

5. The image signal amplifying circuit according to claim 4, wherein the illumination condition includes a dynamic range scene.

6. The image signal amplifying circuit according to claim 1,

wherein the image sensor generates at least two of a first image, a second image, a third image, and a fourth image, wherein the first image corresponds to the first conversion gain and the first gain value, wherein the second image corresponds to the first conversion gain and the second gain value, wherein the third image corresponds to the second conversion gain and the third gain value, and wherein the fourth image corresponds to the second conversion gain and the fourth gain value;

wherein, this image signal amplification circuit still includes:

and the image fusion circuit is used for fusing at least two images of the first image, the second image, the third image and the fourth image to generate a fused image.

7. The image signal amplifying circuit according to claim 6, wherein the fusing circuit applies the second image as a main reference image during fusing.

8. An image signal amplifying circuit comprising:

an amplifier configured to amplify a first image signal and amplify a second image signal generated by a pixel array of an image sensor with a first analog gain, wherein a brightness of a dark image corresponding to the first image signal is lower than a brightness of a bright image corresponding to the second image signal, wherein the dark image and the bright image are generated by only one exposure of the image sensor; and

gain control circuitry, coupled to the amplifier, configured to selectively set the first analog gain to one of a first gain value and a second gain value, or to selectively set the second analog gain to one of a third gain value and a fourth gain value, wherein the first gain value is greater than the second gain value, and the third gain value is greater than the fourth gain value;

wherein each pixel circuit in the pixel array has a first conversion gain corresponding to the dark image and a second conversion gain corresponding to the bright image.

9. The image signal amplifying circuit according to claim 8, wherein the first conversion gain and the second conversion gain are fixed values.

10. The image signal amplifying circuit according to claim 8, wherein the first gain value is equal to the third gain value, and the second gain value is equal to the fourth gain value.

11. The image signal amplifying circuit according to claim 8, wherein the gain control circuit automatically sets the first analog gain or the second analog gain according to the illumination sensed by the image sensor.

12. The image signal amplification circuit of claim 11, wherein the illumination condition comprises a dynamic range scene.

13. The image signal amplifying circuit according to claim 8,

wherein the image sensor generates at least two of a first image, a second image, a third image, and a fourth image, wherein the first image corresponds to the first conversion gain and the first gain value, wherein the second image corresponds to the first conversion gain and the second gain value, wherein the third image corresponds to the second conversion gain and the third gain value, and wherein the fourth image corresponds to the second conversion gain and the fourth gain value;

wherein, this image signal amplification circuit still includes:

and the image fusion circuit is used for fusing at least two images of the first image, the second image, the third image and the fourth image to generate a fused image.

14. The image signal amplifying circuit according to claim 13, wherein the fusing circuit applies the second image as a main reference image during fusing.

15. An image signal amplifying method, comprising:

(a) Amplifying the first image signal with a first analog gain;

(b) Amplifying a second image signal with a second analog gain, wherein the first image signal and the second image signal are generated by a pixel array of an image sensor, wherein each pixel circuit of the pixel array comprises a first capacitor generating the first image signal and a second capacitor generating the second image signal, wherein a charge storage capacity of the first capacitor is smaller than a charge storage capacity of the second capacitor; and

(c) Selectively setting the first analog gain to one of a first gain value and a second gain value, or selectively setting the second analog gain to one of a third gain value and a fourth gain value, wherein the first gain value is greater than the second gain value, and the third gain value is greater than the fourth gain value;

each pixel circuit has a first conversion gain corresponding to the first capacitor and a second conversion gain corresponding to the second capacitor.

16. The image signal amplifying method according to claim 15, wherein the first conversion gain and the second conversion gain are fixed values.

17. The method of amplifying an image signal according to claim 15, wherein the first gain value is equal to the third gain value, and the second gain value is equal to the fourth gain value.

18. The method of claim 15, wherein the step (c) sets the first analog gain or the second analog gain according to the illumination sensed by the image sensor.

19. The image signal amplification method of claim 18, wherein the illumination condition comprises a dynamic range scene.

20. The image signal amplifying method as claimed in claim 15, further comprising:

(d) Generating at least two of a first image, a second image, a third image, and a fourth image, wherein the first image corresponds to the first conversion gain and the first gain value, wherein the second image corresponds to the first conversion gain and the second gain value, the third image corresponds to the second conversion gain and the third gain value, and the fourth image corresponds to the second conversion gain and the fourth gain value; and

(e) At least two of the first image, the second image, the third image, and the fourth image are fused to generate a fused image.

21. The image signal amplifying method according to claim 20, wherein step (e) applies the second image as a main reference image during the fusing.