Reading circuit of optical signal and image sensor

Abstract

The invention discloses an optical signal readout circuit and an image sensor, and relates to the field of electronic information, when a photosensitive pixel receives an optical signal and generates a corresponding light current, a logarithmic conversion module performs logarithmic conversion on the light current flowing through the photosensitive pixel, so that the light signal is read out; and the output buffer module buffers the voltage signal obtained by conversion and then takes the buffered voltage signal as a final read-out electric signal. A logarithmic conversion module is used for converting a light current signal which is originally in an exponential relationship with light intensity to obtain a voltage signal which is in a logarithmic relationship with the light current signal, compression of an exponential signal is achieved, and the relationship between the voltage signal finally output by the reading circuit and the input light intensity signal returns to a linear relationship. The limitation of the dynamic range of the voltage signal is effectively avoided, the reading of the optical signal is realized by generating the voltage signal with better linearity and dynamic range, the error caused by nonlinearity is reduced, and the accuracy and reliability of the whole optical signal reading process are improved.

Description

Technical Field

[0001] The present invention relates to the field of electronic information, and in particular to a light signal readout circuit and an image sensor. Background Art

[0002] As an important device for obtaining visual information, image sensors can convert perceived light signals into electrical signals for output, and can be applied in the fields of photography, videography, and imaging. With the continuous development and widespread application of image sensors, users' requirements for their performance are also constantly increasing. Resistor-modulated photosensitive devices can capture light signals, and light signals change the resistance of resistor-modulated photosensitive devices. The change in resistance can be quantified by detecting the voltage across the resistor and then detecting the change in the current flowing through the resistor, thereby converting the light signal into an electrical signal of the current change value, thereby realizing the reading of the light signal. However, in the prior art, the relationship between the electrical signal generated by linearly amplifying the photocurrent through a resistor and the light intensity is an exponential relationship. When the light intensity changes, the electrical signal grows exponentially, resulting in poor linearity in the light signal reading process; and once the input range of the light intensity signal is too wide, it is easy to saturate the electrical signal, which limits the dynamic range of the electrical signal. Summary of the invention

[0003] The purpose of the present invention is to provide a light signal readout circuit and image sensor, so that the relationship between the voltage signal finally output by the readout circuit and the input light intensity signal returns to a linear relationship, effectively avoiding the limitation of the dynamic range of the voltage signal, and realizing the readout of the light signal by generating a voltage signal with better linearity and dynamic range, reducing the error caused by nonlinearity, and improving the accuracy and reliability of the entire light signal readout process.

[0004] In order to solve the above technical problems, the present invention provides a readout circuit of an optical signal, comprising:

[0005] A logarithmic conversion module, whose input end is connected to a photosensitive pixel, and is used to perform logarithmic conversion on a photocurrent flowing through the photosensitive pixel to generate a voltage signal having a logarithmic relationship with the photocurrent;

[0006] An output buffer module, whose input end is connected to the output end of the logarithmic conversion module, is used for buffering the voltage signal and then outputting it.

[0007] Optionally, the output buffer module includes:

[0008] A source follower, whose control end is connected to the output end of the logarithmic conversion module, and is used to amplify and output the voltage signal output by the logarithmic conversion module;

[0009] The first current bias module has an output end connected to one end of the source follower and serves as the output end of the output buffer module, and is used to provide a bias current for the source follower.

[0010] Optionally, the image sensor includes a pixel array consisting of a plurality of photosensitive pixels; and the readout circuit further includes:

[0011] A selection switch, the control end of which is connected to an output selection signal, the first end of which is connected to one end of the source follower, and the second end of which is connected to the output end of the first current bias module, is used to turn on when the photosensitive pixel is selected for output, and to turn off when the photosensitive pixel is not selected for output.

[0012] Optionally, the first end of the photosensitive pixel is connected to a first power supply, and the second end is connected to an input end of the logarithmic conversion module, and the logarithmic conversion module includes:

[0013] A-level first amplification unit;

[0014] For any first amplifying unit, the first amplifying unit includes a first conversion switch tube and a first amplifying switch tube, the control end of the first amplifying switch tube is connected to the first end of the first conversion switch tube and serves as the first input end of the first amplifying unit, the first end of the first amplifying switch tube serves as the second input end of the first amplifying unit, the second end of the first conversion switch tube serves as the first output end of the first amplifying unit, and the control end of the first conversion switch tube is connected to the second end of the first amplifying switch tube and serves as the second output end of the first amplifying unit;

[0015] The first input end of the first amplifier unit of the first stage is connected to the second end of the photosensitive pixel, the second input end of the first amplifier unit of the first stage is connected to the second power supply, the first output end of the A-th first amplifier unit is grounded, the first output end of the i-th first amplifier unit is connected to the first input end of the i+1-th first amplifier unit, and the second output end of the i-th first amplifier unit is connected to the second input end of the i+1-th first amplifier unit; A is a positive integer, and i is a positive integer less than A;

[0016] The second current bias module has an output end connected to the second output end of the A-th level first amplification unit and serves as the output end of the logarithmic conversion module.

[0017] Optionally, the first end of the photosensitive pixel is connected to a first power supply, and the second end is connected to an input end of the logarithmic conversion module, and the logarithmic conversion module includes:

[0018] A second amplifying switch tube, a first end of which is connected to a second power supply;

[0019] A second conversion switch tube, a first end of which is respectively connected to the control end of the second amplifying switch tube and the second end of the photosensitive pixel;

[0020] A third conversion switch tube, a first end of which is respectively connected to the second end of the second conversion switch tube and the control end of the second conversion switch tube, and a second end of which is grounded;

[0021] The third current bias module has an output end respectively connected to the control end of the third conversion switch tube and the second end of the second amplification switch tube, and serves as the output end of the logarithmic conversion module.

[0022] Optionally, the first end of the photosensitive pixel is connected to a first power supply, and the second end is connected to an input end of the logarithmic conversion module, and the logarithmic conversion module includes:

[0023] A third amplifying switch tube, a first end of which is connected to the second power supply;

[0024] A fourth conversion switch tube, a first end of which is respectively connected to the control end of the third amplifying switch tube and the second end of the photosensitive pixel, and a control end is connected to a first preset bias voltage;

[0025] The fourth current bias module has an output end connected to the second end of the fourth conversion switch tube and the second end of the third amplification switch tube respectively, and serves as the output end of the logarithmic conversion module.

[0026] Optionally, the first end of the photosensitive pixel is grounded, and the second end is connected to the input end of the logarithmic conversion module, and the logarithmic conversion module includes:

[0027] Class B second amplifier unit;

[0028] For any second amplifying unit, the second amplifying unit includes a fifth conversion switch tube and a fourth amplifying switch tube, the control end of the fourth amplifying switch tube is connected to the first end of the fifth conversion switch tube and serves as the first input end of the second amplifying unit, the first end of the fourth amplifying switch tube serves as the second input end of the second amplifying unit, the second end of the fifth conversion switch tube serves as the first output end of the second amplifying unit, and the control end of the fifth conversion switch tube is connected to the second end of the fourth amplifying switch tube and serves as the second output end of the second amplifying unit;

[0029] The first input end of the second amplifying unit of the first stage is connected to the second end of the photosensitive pixel, the second input end of the second amplifying unit of the first stage is grounded, the first output end of the second amplifying unit of the Bth stage is connected to the second power supply, the first output end of the second amplifying unit of the jth stage is connected to the first input end of the second amplifying unit of the j+1th stage, and the second output end of the second amplifying unit of the jth stage is connected to the second input end of the second amplifying unit of the j+1th stage; B is a positive integer, and j is a positive integer less than B;

[0030] The fifth current bias module has an output end connected to the second output end of the second amplifying unit of the Bth stage and serves as the output end of the logarithmic conversion module.

[0031] Optionally, the first end of the photosensitive pixel is grounded, and the second end is connected to the input end of the logarithmic conversion module, and the logarithmic conversion module includes:

[0032] A fifth amplifying switch tube, a first end of which is grounded;

[0033] a sixth conversion switch tube, a first end of which is respectively connected to the control end of the fifth amplifying switch tube and the second end of the photosensitive pixel;

[0034] a seventh conversion switch tube, wherein a first end is respectively connected to the second end of the sixth conversion switch tube and the control end of the sixth conversion switch tube, and a second end is connected to the second power supply;

[0035] The sixth current bias module has an output end respectively connected to the control end of the seventh conversion switch tube and the second end of the fifth amplification switch tube, and serves as the output end of the logarithmic conversion module.

[0036] Optionally, the first end of the photosensitive pixel is grounded, and the second end is connected to the input end of the logarithmic conversion module, and the logarithmic conversion module includes:

[0037] A sixth amplifying switch tube, a first end of which is grounded;

[0038] An eighth conversion switch tube, wherein a first end is respectively connected to the second end of the photosensitive pixel and the control end of the sixth amplifying switch tube, and the control end is connected to a second preset bias voltage;

[0039] The seventh current bias module has an output end connected to the second end of the eighth conversion switch tube and the second end of the sixth amplification switch tube respectively, and serves as the output end of the logarithmic conversion module.

[0040] To solve the above technical problems, the present invention also provides an image sensor, comprising a photosensitive pixel and a light signal readout circuit as described above, wherein the input end of the light signal readout circuit is connected to the photosensitive pixel for converting the light signal captured by the photosensitive pixel into an electrical signal.

[0041] The present invention provides a light signal readout circuit, including a logarithmic conversion module and an output buffer module. When a photosensitive pixel receives a light signal and generates a corresponding photocurrent, the logarithmic conversion module performs logarithmic conversion on the photocurrent flowing through the photosensitive pixel, and then the output buffer module buffers the converted voltage signal as the final readout electrical signal. The logarithmic conversion module is used to convert the photocurrent signal that originally has an exponential relationship with the light intensity to obtain a voltage signal that has a logarithmic relationship with the photocurrent signal, thereby achieving compression of the exponential signal, so that the relationship between the voltage signal finally output by the readout circuit and the input light intensity signal returns to a linear relationship, effectively avoiding the limitation of the dynamic range of the voltage signal, and realizing the readout of the light signal by generating a voltage signal with better linearity and dynamic range, reducing the error caused by nonlinearity, and improving the accuracy and reliability of the entire light signal readout process.

[0042] The present invention also provides an image sensor having the same beneficial effects as the above-mentioned optical signal readout circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the prior art and the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0044] Figure 1 A schematic diagram of the structure of a light signal readout circuit provided by the present invention;

[0045] Figure 2 A schematic structural diagram of a photosensitive pixel provided by the present invention;

[0046] Figure 3 A schematic diagram of a readout circuit for a light signal when a photosensitive pixel is connected to a high bias voltage provided by the present invention;

[0047] Figure 4 A schematic diagram of a structure of a readout circuit of a light signal when a photosensitive pixel is connected to a low bias voltage provided by the present invention;

[0048] Figure 5 A schematic diagram of the structure of another optical signal readout circuit provided by the present invention;

[0049] Figure 6 A schematic diagram of a configuration method of an output buffer circuit provided by the present invention;

[0050] Figure 7 A schematic diagram of another configuration of an output buffer circuit provided by the present invention;

[0051] Figure 8 A schematic diagram of the structure of a readout circuit of a light signal using a pixel array provided by the present invention;

[0052] Fig. 9 A schematic diagram of the structure of a logarithmic conversion module when the first photosensitive pixel provided by the present invention is connected to a high bias voltage;

[0053] Fig.10 A structural schematic diagram of a logarithmic conversion module when a second photosensitive pixel provided by the present invention is connected to a high bias voltage;

[0054] Fig.11 A schematic diagram of the structure of a logarithmic conversion module when a third photosensitive pixel provided by the present invention is connected to a high bias voltage;

[0055] Fig.12 A structural schematic diagram of a logarithmic conversion module when a fourth photosensitive pixel provided by the present invention is connected to a high bias voltage;

[0056] Fig.13 A schematic diagram of the structure of a logarithmic conversion module when the first photosensitive pixel provided by the present invention is connected to a low bias voltage;

[0057] Fig.14 A structural schematic diagram of a logarithmic conversion module when a second photosensitive pixel provided by the present invention is connected to a low bias voltage;

[0058] Fig.15 A schematic diagram of the structure of a logarithmic conversion module when a third photosensitive pixel provided by the present invention is connected to a low bias voltage;

[0059] Fig.16 This is a structural schematic diagram of a logarithmic conversion module when a fourth photosensitive pixel provided by the present invention is connected to a low bias voltage. DETAILED DESCRIPTION

[0060] The core of the present invention is to provide a light signal readout circuit and image sensor, so that the relationship between the voltage signal finally output by the readout circuit and the input light intensity signal returns to a linear relationship, effectively avoiding the limitation of the dynamic range of the voltage signal, and realizing the readout of the light signal by generating a voltage signal with better linearity and dynamic range, reducing the error caused by nonlinearity, and improving the accuracy and reliability of the entire light signal readout process.

[0061] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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.

[0062] It should be noted that the present invention is mainly aimed at photosensitive pixels using two-dimensional sheet materials. Such pixels belong to resistance modulation type photosensitive devices. In two different situations of light irradiation and no light irradiation, the two-dimensional material will present different resistance values, and its resistance value is exponentially related to the radiation illumination of light, thereby realizing the readout and conversion of light signals. This type of photosensitive pixel includes two nodes, an electrode end and a signal readout end, and its photosensitive part is composed of a two-dimensional material graphene distributed between the two nodes and quantum dots connected to the graphene. The material of the quantum dots can be cadmium sulfide, cadmium selenide, cadmium telluride, zinc selenide, lead sulfide, lead selenide, indium phosphide, etc. By using quantum dots as photosensitive materials, the wavelength of absorbed light can be optimized. For example, PbS can be used to absorb and measure light in the short-wave infrared band; it can also directly use the silicon material itself to be sensitive to light to achieve the capture and acquisition of light signals. The two-dimensional material can also be molybdenum disulfide, etc. For such photosensitive pixels, the present invention provides a light signal readout circuit to implement the readout and conversion of the light signal captured by the photosensitive pixel. The specific implementation is described as follows.

[0063] Please refer to Figure 1 , Figure 1 A schematic diagram of a readout circuit for an optical signal provided by the present invention; please refer to Figure 2 , Figure 2 The present invention provides a schematic diagram of the structure of a photosensitive pixel. The electrical signal after photoelectric conversion in the photosensitive pixel is transmitted to the signal readout terminal 31 and then output. The electrode terminal 32 provides necessary electrical energy for each component in the photosensitive pixel. The photosensitive pixel uses silicon dioxide 33 to isolate different electrodes and circuit elements in the photosensitive pixel. Graphene 34 is set in the photosensitive area to quickly collect and transmit the charge generated in the photoelectric conversion process. Quantum dots 35 are set in the photosensitive area to absorb photons. To solve the above technical problems, the present invention provides a readout circuit of an optical signal, including:

[0064] A logarithmic conversion module 1, whose input end is connected to a photosensitive pixel, is used to perform logarithmic conversion on a photocurrent flowing through the photosensitive pixel to generate a voltage signal having a logarithmic relationship with the photocurrent;

[0065] The output buffer module 2 has an input end connected to the output end of the logarithmic conversion module 1 and is used to buffer the voltage signal before outputting it.

[0066] It is not difficult to understand that in order to achieve more accurate and reliable reading of the light signal, the present invention sets a logarithmic conversion module 1 in the readout circuit of the light signal. The logarithmic conversion module 1 performs logarithmic conversion on the photocurrent flowing through the photosensitive pixel and generates a corresponding voltage signal, and realizes the reading of the light signal based on the voltage signal. The logarithmic conversion module 1 is connected in series with the photosensitive pixel. When the photosensitive pixel is exposed to light, its resistance value changes with the change of the light signal, and the resistance value is exponentially related to the radiation illumination of the light; when the power supply connected to the photosensitive pixel remains unchanged, the photocurrent flowing through the photosensitive pixel is inversely proportional to the resistance value of the photosensitive pixel, so the photocurrent flowing through the photosensitive pixel can also effectively characterize the light signal received by the photosensitive pixel, and is exponentially related to the radiation illumination of the light. After the photocurrent flowing through the photosensitive pixel is input into the logarithmic conversion module 1, the logarithmic conversion module 1 performs logarithmic conversion on it to obtain a voltage signal that is linearly related to the radiation illumination of the light. Thus, the mechanism of exponential transformation in the photosensitive pixel is offset by logarithmic transformation, and linear compensation of light intensity is efficiently achieved.

[0067] It is understandable that, considering that the voltage signal obtained after the conversion by the logarithmic conversion module 1 may have abnormal jitter due to noise and interference signals, and considering that the voltage signal read by the readout circuit needs to be input into the analog-to-digital conversion circuit and the upper computer and other circuits for further processing to realize functions such as image generation, in the optical signal readout circuit, the present invention further sets an output buffer module 2, and the voltage signal output by the logarithmic conversion module 1 will pass through the output buffer module 2 to realize the final electrical signal readout, and the output buffer module 2 can not only play the role of signal isolation, avoid mutual interference of signals between other circuit modules and the logarithmic conversion module 1, and prevent the voltage signal from being affected by noise, interference signals, etc. that may appear in the subsequent circuit, but also can absorb abnormal reverse current and back electromotive force, protect the logarithmic conversion module 1, and ensure the safety and reliability of the entire readout circuit. At the same time, by setting the output buffer module 2, the signal quality of the voltage signal can be further improved, and the output buffer module can shape the voltage signal, realize the level matching of the voltage signal, improve the driving ability of the voltage signal, etc., ensure the complete transmission of the voltage signal, and reduce the jitter of the signal; improve the stability and reliability of the entire readout circuit.

[0068] It should be noted that the specific type and implementation of the logarithmic conversion circuit and the output buffer module 2 are not specifically limited in this application. The circuit architecture composed of MOS tubes (Metal-Oxide-Semiconductor Field-Effect Transistor), triodes and other devices can be used for implementation. The specific type and implementation of the photosensitive pixel can also be set and adjusted according to the actual application situation. This application does not make any special restrictions here. Please refer to Figure 3 , Figure 3 A schematic diagram of a readout circuit for a light signal when a photosensitive pixel is connected to a high bias voltage provided by the present invention; please refer to Figure 4 , Figure 4 A structural schematic diagram of a readout circuit of a light signal when a photosensitive pixel is connected to a low bias voltage provided by the present invention; VDD is the power supply voltage, and Rpix represents the resistance of the photosensitive pixel; there are two possibilities in the application of the photosensitive pixel, one is that the photosensitive pixel needs to be connected to a high bias voltage for application implementation (Vdd is used to represent the high bias voltage in this embodiment), and the other is that the pixel needs to be connected to a low bias voltage for application implementation (GND is used to represent the low bias voltage in this embodiment).

[0069] It is not difficult to understand that the present invention can be applied to various types of image sensors and other devices using resistive modulation type photosensitive pixels. Figure 5 , Figure 5 This is a schematic diagram of the structure of another optical signal readout circuit provided by the present invention; the electrode end node in the photosensitive pixel is connected to a bias voltage, and the signal readout end node is connected to a logarithmic conversion module 1, which converts the photocurrent into a voltage signal, and the magnitude of the voltage signal is in a logarithmic relationship with the magnitude of the photocurrent. Then, this voltage is buffered by the source follower SF of the output buffer module 2 and the signal is amplified, and then connected to the signal readout line shared by the pixel array through the selection switch SEL, thereby realizing the readout and conversion of the optical signal.

[0070] It is understandable that for resistance modulated photosensitive devices, especially new materials represented by two-dimensional sheet materials (graphene or molybdenum disulfide) + quantum dots as sensors of photosensitive devices, the logarithmic conversion module 1 is used to process the photocurrent of the photosensitive pixel to generate a voltage signal with better linearity and dynamic range. The resistance change of the photosensitive pixel caused by light is exponentially related to the light intensity. By using the logarithmic conversion module 1, the compression of the exponential signal is achieved, so that the relationship between the output voltage signal and the input light intensity signal returns to a linear relationship. This solves the problems of poor linearity of the readout signal and limited dynamic range.

[0071] The present invention provides a light signal readout circuit, including a logarithmic conversion module 1 and an output buffer module 2. When a photosensitive pixel receives a light signal and generates a corresponding photocurrent, the logarithmic conversion module 1 performs logarithmic conversion on the photocurrent flowing through the photosensitive pixel, and then the output buffer module 2 buffers the converted voltage signal as the final readout electrical signal. The logarithmic conversion module 1 is used to convert the photocurrent signal that originally has an exponential relationship with the light intensity to obtain a voltage signal that has a logarithmic relationship with the photocurrent signal, thereby achieving compression of the exponential signal, so that the relationship between the voltage signal finally output by the readout circuit and the input light intensity signal returns to a linear relationship, effectively avoiding the limitation of the dynamic range of the voltage signal, and realizing the readout of the light signal by generating a voltage signal with better linearity and dynamic range, reducing the error caused by nonlinearity, and improving the accuracy and reliability of the entire light signal readout process.

[0072] Based on the above embodiments:

[0073] Please refer to Figure 6 , Figure 6 A schematic diagram of the configuration of an output buffer circuit provided by the present invention; please refer to Figure 7 , Figure 7 A schematic diagram of another configuration of an output buffer circuit provided by the present invention; as an optional embodiment, the output buffer module 2 includes:

[0074] The source follower SF has a control end connected to the output end of the logarithmic conversion module 1 and is used to amplify the voltage signal output by the logarithmic conversion module 1 and then output it;

[0075] The first current bias module Q31 has an output end connected to one end of the source follower SF and serves as an output end of the output buffer module 2 to provide a bias current for the source follower SF.

[0076] It is not difficult to understand that the transformed voltage signal needs to be further buffered and amplified before being read out. The output buffer module 2 can be specifically implemented by a source follower SF. The voltage signal output by the logarithmic conversion module 1 acts on the gate of the source follower SF, causing the potential of the source of the source follower SF to change with the change of the voltage signal, thereby realizing the voltage following function. At the same time, the input impedance of the source follower SF itself is relatively high, and can effectively buffer the voltage signal. Considering that the source follower SF needs to work in a specific state, generally in the saturation region to achieve buffering and amplification of the input signal, a first current bias module Q31 needs to be set in the output buffer module 2 to provide the source follower SF with a bias current that supports it to work in the saturation region, ensuring that the source follower SF can effectively achieve buffering and amplification of the voltage signal. The specific type and implementation method of the source follower SF and the first current bias module Q31 are not particularly limited in this application.

[0077] As a specific embodiment, Figure 6 As shown, the source follower SF can be implemented by a PMOS tube with a drain grounded, and the first current bias module Q31 can be implemented by a PMOS tube with a source connected to a power supply and a gate connected to a preset fixed bias voltage Vbias_peri, and a fixed bias current is generated by using the fixed bias voltage to provide to the source follower SF; the specific value and implementation method of the bias voltage connected to the first current bias module Q31 are not particularly limited in this application. Figure 7 As shown, the source follower SF can be implemented by an NMOS tube whose drain is connected to the power supply, and the first current bias module Q31 can be implemented by an NMOS tube whose source is grounded and whose gate is connected to a preset fixed bias voltage Vbias_peri. The source of the source follower is connected to the analog-to-digital conversion circuit after passing through the selection switch SEL, so as to further convert the voltage signal of the read voltage output into a digital signal, which is convenient for subsequent processing by a processor and other equipment. Figure 6 The figure shows the implementation method when the logarithmic conversion module, the first current bias module and the output buffer module use the same power supply and a common ground. In actual applications, the power supply and grounding point implementation methods used by the logarithmic conversion module, the first current bias module and the output buffer module can be different, that is, the VDD connected to the fifth conversion switch tube Q15, the VDD connected to the fifth current bias module Q35 and the VDD connected to the first current bias module Q31 can be implemented using different power supplies, and the grounding point of the photosensitive pixel, the grounding point of the fourth amplifying switch tube Q24 and the grounding point of the source follower SF can also be implemented in different ways.

[0078] Specifically, by adopting the source follower SF to implement the output buffer module 2, the converted voltage signal can be effectively buffered and amplified. At the same time, the first current bias module Q31 is set to ensure the accurate application of the source follower SF, thereby improving the accuracy and stability of the final output voltage signal and ensuring the accuracy and reliability of the entire readout circuit.

[0079] Please refer to Figure 8 , Figure 8 A schematic diagram of a readout circuit for a light signal using a pixel array provided by the present invention; as an optional embodiment, the image sensor includes a pixel array composed of a plurality of photosensitive pixels; the readout circuit also includes:

[0080] The selection switch SEL has a control end connected to an output selection signal, a first end connected to one end of the source follower SF, and a second end connected to the output end of the first current bias module Q31, and is used to be turned on when the photosensitive pixel is selected for output, and turned off when the photosensitive pixel is not selected for output.

[0081] It is understandable that a plurality of photosensitive pixels are generally provided in an image sensor and are arranged in an array, so that a detailed, comprehensive and complete image presentation can be achieved through the pixel array. At this time, the readout circuit of the light signal needs to realize the signal readout of all photosensitive pixels in the pixel array. Therefore, in order to facilitate management and realize the accurate readout of each photosensitive pixel, a plurality of selection switches SEL connected one-to-one with a plurality of photosensitive pixels in the pixel array will also be provided in the readout circuit. The selection switch SEL is connected in series between the source of the source follower SF and the output end of the readout circuit, and can control whether the voltage signal finally obtained by the readout circuit is output or not. When a selection switch SEL is turned on, the readout circuit outputs the voltage signal converted by the corresponding photosensitive pixel. When a selection switch SEL is turned off, the voltage signal corresponding to the conversion of the photosensitive pixel will not be output to the subsequent circuit; thereby realizing the accurate readout of the voltage signal corresponding to each different photosensitive pixel. The specific type and implementation of the selection switch SEL are not specifically limited in this application. The specific type and implementation of the output selection signal that controls its action can be set and connected according to actual application conditions, and the application does not specifically limit it. Figure 6 and Figure 7 As shown, the gate switch SEL can be directly implemented by a PMOS tube or an NMOS tube connected in series with the source follower SF.

[0082] It is understandable that, for different bias modes of photosensitive pixels, it is necessary to set up corresponding logarithmic conversion modules 1 and different output buffer modules 2, and use different source followers SF and other methods to cover each photosensitive pixel in the image sensor, so as to realize the reading of the light signal obtained by the entire image sensor, so as to realize functions such as image display.

[0083] As a specific embodiment, Figure 8As shown, the pixel array includes N×M (row×column) photosensitive pixels, and each photosensitive pixel is provided with a corresponding pixel circuit including a logarithmic conversion module 1, a source follower SF and a gate switch SEL. This embodiment takes the gate switch SEL as a row selection switch as an example for explanation. The controller generates N row selection signals RowSel as output selection signals. The N photosensitive pixels in each column share a first current bias module Q31 and an analog-to-digital conversion circuit. The entire pixel array only needs to be provided with M first current bias modules Q31 and M analog-to-digital conversion circuits. The controller controls the corresponding gate switch SEL through the row selection signals RowSel1-RowSelN. Each time, the gate switch SEL corresponding to the photosensitive pixels of a row is turned on in units of rows to realize simultaneous readout of a row of data, and the row parallel readout circuit is used to read and convert the light signal after Log conversion into analog-to-digital. The row selection signal and the gate switch SEL are both set to control the readout of pixels in different rows when using the pixel array. In the architecture of row-parallel digital-to-analog converters (ADCs), each ADC needs to select and read out pixels by row. Depending on the number of row-parallel ADCs, half a row, one row, or multiple rows can be read out each time.

[0084] Specifically, the selection switch SEL can be set to achieve accurate readout of the corresponding signal of each photosensitive pixel in the pixel array application scenario, and the simultaneous readout of the corresponding signals of multiple photosensitive pixels can be achieved through row selection signals or column selection signals, thereby improving the readout speed of the light signal, effectively reducing the number of circuit connections, and simplifying the circuit structure; further considering the setting method of the readout circuit in the case of a pixel array, the flexibility of the readout circuit is improved and the scope of application is expanded.

[0085] Please refer to Fig. 9 , Fig. 9 This is a structural diagram of the logarithmic conversion module when the first photosensitive pixel provided by the present invention is connected to a high bias voltage; please refer to Fig.10 , Fig.10 A schematic diagram of the structure of a logarithmic conversion module when a second photosensitive pixel provided by the present invention is connected to a high bias voltage; as an optional embodiment, a first end of the photosensitive pixel is connected to a first power supply, and a second end is connected to an input end of a logarithmic conversion module 1, and the logarithmic conversion module 1 includes:

[0086] A-level first amplification unit;

[0087] For any first amplifying unit, the first amplifying unit includes a first conversion switch tube Q11 and a first amplifying switch tube Q21, the control end of the first amplifying switch tube Q21 is connected to the first end of the first conversion switch tube Q11 and serves as the first input end of the first amplifying unit, the first end of the first amplifying switch tube Q21 serves as the second input end of the first amplifying unit, the second end of the first conversion switch tube Q11 serves as the first output end of the first amplifying unit, and the control end of the first conversion switch tube Q11 is connected to the second end of the first amplifying switch tube Q21 and serves as the second output end of the first amplifying unit;

[0088] The first input end of the first-stage first amplifying unit is connected to the second end of the photosensitive pixel, the second input end of the first-stage first amplifying unit is connected to the second power supply, the first output end of the A-th-stage first amplifying unit is grounded, the first output end of the i-th-stage first amplifying unit is connected to the first input end of the i+1-th-stage first amplifying unit, and the second output end of the i-th-stage first amplifying unit is connected to the second input end of the i+1-th-stage first amplifying unit; A is a positive integer, and i is a positive integer less than A;

[0089] The second current bias module Q32 has an output end connected to the second output end of the first amplifying unit of the Ath stage and serves as the output end of the logarithmic conversion module 1 .

[0090] It is not difficult to understand that when the photosensitive pixel is in a state of being connected to a high bias voltage, the logarithmic conversion module 1 can be implemented by using a first amplifying unit of class A. For the first amplifying unit of any level, it includes a first conversion switch tube Q11 and a first amplifying switch tube Q21. The first conversion switch tube Q11 and the first amplifying switch tube Q21 cooperate to perform logarithmic conversion and signal amplification on the photocurrent corresponding to the second terminal voltage Vsens of the photosensitive pixel, and then convert it into a voltage signal Vsig_log for output. The first conversion switch tube Q11 plays a role in logarithmic conversion, and the first amplifying switch tube Q21 plays a role in signal amplification. The specific types and implementation methods of the first conversion switch tube Q11 and the first amplifying switch tube Q21 are not particularly limited in this application. They can be implemented by switching devices such as MOS tubes and triodes, or by other methods. Considering that the first conversion switch tube Q11 and the first amplifying switch tube Q21 in the first amplifying unit need to work in a specific working state to achieve the corresponding logarithmic conversion and signal amplification functions, a second current bias module Q32 is also provided in the logarithmic conversion module 1 to provide a stable bias current for the first conversion switch tube Q11 and the first amplifying switch tube Q21. The specific type of the second current bias module Q32 and the specific value of the bias current provided by it are not specifically limited in this application. The specific type and implementation of the first power supply and the second power supply are not specifically limited in this application. The same power supply can be used for implementation, or different power supplies can be selected according to actual application requirements.

[0091] As a specific embodiment, Fig. 9 As shown, the logarithmic conversion module 1 includes a first-stage amplification unit, and the second current bias module Q32 is implemented by an NMOS tube with a source grounded and a gate connected to a preset fixed bias voltage Vbias. Fig.10 As shown, the logarithmic conversion module 1 includes two stages of first amplifying units, and the second current bias module Q32 is implemented by an NMOS tube with a source grounded and a gate connected to a preset fixed bias voltage Vbias.

[0092] Specifically, a logarithmic conversion module 1 composed of a first conversion switch tube Q11, a first amplifying switch tube Q21 and a second current bias module Q32 can be used to realize the logarithmic conversion of the photocurrent flowing through the photosensitive pixel. The entire circuit structure is simple and easy to implement, which is conducive to the simple implementation of the entire readout circuit.

[0093] Please refer to Fig.11 , Fig.11 A schematic diagram of the structure of a logarithmic conversion module when a third photosensitive pixel provided by the present invention is connected to a high bias voltage; as an optional embodiment, a first end of the photosensitive pixel is connected to a first power supply, and a second end is connected to an input end of a logarithmic conversion module 1, and the logarithmic conversion module 1 includes:

[0094] A second amplifying switch tube Q22, a first end of which is connected to a second power supply;

[0095] A second conversion switch tube Q12, a first end of which is respectively connected to a control end of the second amplifying switch tube Q22 and a second end of the photosensitive pixel;

[0096] A third conversion switch tube Q13, a first end of which is respectively connected to the second end of the second conversion switch tube Q12 and the control end of the second conversion switch tube Q12, and a second end of which is grounded;

[0097] The output end of the third current bias module Q33 is respectively connected to the control end of the third conversion switch tube Q13 and the second end of the second amplification switch tube Q22 , and serves as the output end of the logarithmic conversion module 1 .

[0098] It can be understood that when the photosensitive pixel is in a state of being connected to a high bias voltage, the logarithmic conversion module 1 may specifically include a second amplifying switch tube Q22, a second conversion switch tube Q12, a third conversion switch tube Q13 and a third current bias module Q33, the second conversion switch tube Q12 and the third conversion switch tube Q13 play a role in logarithmic conversion, and the second amplifying switch tube Q22 plays a role in signal amplification. The specific types and implementation methods of the second amplifying switch tube Q22, the second conversion switch tube Q12 and the third conversion switch tube Q13 are not particularly limited in this application, and they may be implemented using switch devices such as MOS tubes and triodes, or may be implemented in other ways. Considering that the second amplifying switch tube Q22, the second conversion switch tube Q12 and the third conversion switch tube Q13 all need to work in a specific working state to achieve the corresponding logarithmic conversion and signal amplification functions, the logarithmic conversion module 1 is also provided with a third current bias module Q33 to provide a stable bias current for the second amplifying switch tube Q22, the second conversion switch tube Q12 and the third conversion switch tube Q13. The specific type of the third current bias module Q33 and the specific value of the bias current it provides and other implementation methods are not specifically limited in this application. Fig.11 As shown, the third current bias module Q33 can be implemented by an NMOS tube with a source connected to the ground and a gate connected to a preset fixed bias voltage Vbias.

[0099] Specifically, a logarithmic conversion module 1 composed of a second amplifying switch tube Q22, a second conversion switch tube Q12, a third conversion switch tube Q13 and a third current bias module Q33 can be used to realize the logarithmic conversion of the photocurrent flowing through the photosensitive pixel. The entire circuit structure is simple and easy to implement, which is conducive to the simple implementation of the entire readout circuit.

[0100] Please refer to Fig.12 , Fig.12A schematic diagram of the structure of a logarithmic conversion module when a fourth photosensitive pixel provided by the present invention is connected to a high bias voltage; as an optional embodiment, a first end of the photosensitive pixel is connected to a first power supply, and a second end is connected to an input end of a logarithmic conversion module 1, and the logarithmic conversion module 1 includes:

[0101] A third amplifying switch tube Q23, a first end of which is connected to the second power supply;

[0102] The fourth conversion switch tube Q14 has a first end connected to the control end of the third amplifying switch tube Q23 and the second end of the photosensitive pixel respectively, and the control end is connected to the first preset bias voltage;

[0103] The output end of the fourth current bias module Q34 is respectively connected to the second end of the fourth conversion switch tube Q14 and the second end of the third amplification switch tube Q23 , and serves as the output end of the logarithmic conversion module 1 .

[0104] It is not difficult to understand that when the photosensitive pixel is in a state of being connected to a high bias voltage, the logarithmic conversion module 1 may specifically include a third amplifying switch tube Q23, a fourth conversion switch tube Q14, and a fourth current bias module Q34, wherein the fourth conversion switch tube Q14 plays a role in logarithmic conversion, and the third amplifying switch tube Q23 plays a role in signal amplification. The specific types and implementation methods of the third amplifying switch tube Q23 and the fourth conversion switch tube Q14 are not particularly limited in this application, and they may be implemented using switch devices such as MOS tubes and triodes, or may be implemented using other methods. Considering that the third amplifier switch tube Q23 needs to work in a specific working state to realize the corresponding signal amplification function, the logarithmic conversion module 1 is also provided with a fourth current bias module Q34 to provide a stable bias current for the third amplifier switch tube Q23. At the same time, the control end of the fourth conversion switch tube Q14 is connected to the first preset bias voltage to ensure its stable bias and ensure its logarithmic conversion function. The specific type of the fourth current bias module Q34 and the specific value of the bias current it provides and other implementation methods are not specifically limited in this application. The specific value and implementation method of the first preset bias voltage are not specifically limited in this application, and can be set and adjusted according to the actual application of the fourth conversion switch. Fig.12 As shown, the fourth current bias module Q34 can be implemented by an NMOS tube with a source grounded and a gate connected to a preset fixed bias voltage Vbias2.

[0105] Specifically, a logarithmic conversion module 1 composed of a third amplifying switch tube Q23, a fourth conversion switch tube Q14 and a fourth current bias module Q34 can be used to realize the logarithmic conversion of the photocurrent flowing through the photosensitive pixel. The entire circuit structure is simple and easy to implement, which is conducive to the simple implementation of the entire readout circuit.

[0106] Please refer to Fig.13 , Fig.13 This is a structural diagram of the logarithmic conversion module when the first photosensitive pixel provided by the present invention is connected to a low bias voltage; please refer to Fig.14 , Fig.14 A schematic diagram of the structure of a logarithmic conversion module when a second photosensitive pixel provided by the present invention is connected to a low bias voltage; as an optional embodiment, a first end of the photosensitive pixel is grounded, and a second end is connected to an input end of the logarithmic conversion module 1, and the logarithmic conversion module 1 includes:

[0107] Class B second amplifier unit;

[0108] For any second amplifying unit, the second amplifying unit includes a fifth conversion switch tube Q15 and a fourth amplifying switch tube Q24, the control end of the fourth amplifying switch tube Q24 is connected to the first end of the fifth conversion switch tube Q15 and serves as the first input end of the second amplifying unit, the first end of the fourth amplifying switch tube Q24 serves as the second input end of the second amplifying unit, the second end of the fifth conversion switch tube Q15 serves as the first output end of the second amplifying unit, and the control end of the fifth conversion switch tube Q15 is connected to the second end of the fourth amplifying switch tube Q24 and serves as the second output end of the second amplifying unit;

[0109] The first input end of the first-stage second amplifying unit is connected to the second end of the photosensitive pixel, the second input end of the first-stage second amplifying unit is grounded, the first output end of the B-stage second amplifying unit is connected to the second power supply, the first output end of the j-stage second amplifying unit is connected to the first input end of the j+1-stage second amplifying unit, and the second output end of the j-stage second amplifying unit is connected to the second input end of the j+1-stage second amplifying unit; B is a positive integer, and j is a positive integer less than B;

[0110] The fifth current bias module Q35 has an output end connected to the second output end of the second amplifying unit of the Bth stage and serves as the output end of the logarithmic conversion module 1 .

[0111] It can be understood that when the photosensitive pixel is in a state of being connected to a low bias, the bias voltage connected to the first end of the photosensitive pixel changes from a high bias voltage to a low bias voltage, and the setting mode of the logarithmic conversion module 1 can refer to the setting mode when the photosensitive pixel is connected to a high bias voltage, and it can be symmetrical with the setting mode when the photosensitive pixel is connected to a high bias voltage. The logarithmic conversion module 1 can be specifically implemented by a Class B second amplification unit. For any level of the second amplification unit, it includes a fifth conversion switch tube Q15 and a fourth amplification switch tube Q24. The fifth conversion switch tube Q15 and the fourth amplification switch tube Q24 cooperate to perform logarithmic conversion and signal amplification on the photocurrent corresponding to the second end voltage Vsens of the photosensitive pixel, and then convert it into a voltage signal Vsig_log for output. The fifth conversion switch tube Q15 plays a role in logarithmic conversion, and the fourth amplification switch tube Q24 plays a role in signal amplification. The specific types and implementation methods of the fifth conversion switch tube Q15 and the fourth amplification switch tube Q24 are not particularly limited in this application. They can be implemented by switching devices such as MOS tubes and triodes, or by other methods. Taking into account that the fifth conversion switch tube Q15 and the fourth amplifying switch tube Q24 in the second amplifying unit need to work in a specific working state to achieve the corresponding logarithmic conversion and signal amplification functions, a fifth current bias module Q35 is also provided in the logarithmic conversion module 1 to provide a stable bias current for the fifth conversion switch tube Q15 and the fourth amplifying switch tube Q24. The specific type of the fifth current bias module Q35 and the specific value of the bias current it provides and other implementation methods are not particularly limited in this application.

[0112] As a specific embodiment, Fig.13 As shown, the logarithmic conversion module 1 includes a first-stage second amplification unit, and the fifth current bias module Q35 is implemented by an NMOS tube with a source grounded and a gate connected to a preset fixed bias voltage Vbias. Fig.14 As shown, the logarithmic conversion module 1 includes two stages of second amplifying units, and the fifth current bias module Q35 is implemented by an NMOS tube with a source grounded and a gate connected to a preset fixed bias voltage Vbias.

[0113] Specifically, a logarithmic conversion module 1 composed of a fifth conversion switch tube Q15, a fourth amplifying switch tube Q24 and a fifth current bias module Q35 can be used to realize the logarithmic conversion of the photocurrent flowing through the photosensitive pixel. The entire circuit structure is simple and easy to implement, which is conducive to the simple implementation of the entire readout circuit.

[0114] Please refer to Fig.15 , Fig.15 A schematic diagram of the structure of a logarithmic conversion module when a third photosensitive pixel provided by the present invention is connected to a low bias voltage; as an optional embodiment, a first end of the photosensitive pixel is grounded, and a second end is connected to an input end of the logarithmic conversion module 1, and the logarithmic conversion module 1 includes:

[0115] A fifth amplifying switch tube Q25, a first end of which is grounded;

[0116] A sixth conversion switch tube Q16, a first end of which is respectively connected to the control end of the fifth amplifying switch tube Q25 and the second end of the photosensitive pixel;

[0117] A seventh conversion switch tube Q17, a first end of which is respectively connected to the second end of the sixth conversion switch tube Q16 and the control end of the sixth conversion switch tube Q16, and a second end of which is connected to the second power supply;

[0118] The sixth current bias module Q36 has an output end connected to the control end of the seventh conversion switch tube Q17 and the second end of the fifth amplifying switch tube Q25 respectively, and serves as the output end of the logarithmic conversion module 1.

[0119] It is not difficult to understand that when the photosensitive pixel is in a state of being connected to a low bias voltage, the logarithmic conversion module 1 may specifically include a fifth amplifying switch tube Q25, a sixth conversion switch tube Q16, a seventh conversion switch tube Q17, and a sixth current bias module Q36, the sixth conversion switch tube Q16 and the seventh conversion switch tube Q17 play a role in logarithmic conversion, and the fifth amplifying switch tube Q25 plays a role in signal amplification. The specific types and implementation methods of the fifth amplifying switch tube Q25, the sixth conversion switch tube Q16, and the seventh conversion switch tube Q17 are not particularly limited in this application, and they may be implemented using switch devices such as MOS tubes and triodes, or may be implemented in other ways. Considering that the fifth amplifying switch tube Q25, the sixth conversion switch tube Q16 and the seventh conversion switch tube Q17 all need to work in a specific working state to achieve the corresponding logarithmic conversion and signal amplification functions, the logarithmic conversion module 1 is also provided with a sixth current bias module Q36 to provide a stable bias current for the fifth amplifying switch tube Q25, the sixth conversion switch tube Q16 and the seventh conversion switch tube Q17. The specific type of the sixth current bias module Q36 and the specific value of the bias current it provides and other implementation methods are not particularly limited in this application. Fig.15 As shown, the sixth current bias module Q36 can be implemented by an NMOS tube with a source grounded and a gate connected to a preset fixed bias voltage Vbias.

[0120] Specifically, a logarithmic conversion module 1 composed of a fifth amplifying switch tube Q25, a sixth conversion switch tube Q16, a seventh conversion switch tube Q17 and a sixth current bias module Q36 can be used to realize the logarithmic conversion of the photocurrent flowing through the photosensitive pixel. The entire circuit structure is simple and easy to implement, which is conducive to the simple implementation of the entire readout circuit.

[0121] Please refer to Fig.16 , Fig.16A schematic diagram of the structure of the logarithmic conversion module when the fourth photosensitive pixel provided by the present invention is connected to a low bias voltage. As an optional embodiment, the first end of the photosensitive pixel is grounded, and the second end is connected to the input end of the logarithmic conversion module 1, and the logarithmic conversion module 1 includes:

[0122] A sixth amplifying switch tube Q26, a first end of which is grounded;

[0123] The eighth conversion switch tube Q18, the first end of which is respectively connected to the second end of the photosensitive pixel and the control end of the sixth amplifying switch tube Q26, and the control end is connected to the second preset bias voltage;

[0124] The seventh current bias module Q37 has an output end connected to the second end of the eighth conversion switch tube Q18 and the second end of the sixth amplification switch tube Q26 respectively, and serves as the output end of the logarithmic conversion module 1.

[0125] It can be understood that when the photosensitive pixel is in a state of being connected to a low bias voltage, the logarithmic conversion module 1 can specifically include a sixth amplifying switch tube Q26, an eighth conversion switch tube Q18 and a seventh current bias module Q37, the eighth conversion switch tube Q18 plays a role in logarithmic conversion, and the sixth amplifying switch tube Q26 plays a role in signal amplification. The specific types and implementation methods of the sixth amplifying switch tube Q26 and the eighth conversion switch tube Q18 are not particularly limited in this application, and can be implemented by switching devices such as MOS tubes and triodes, or can be implemented by other methods. Considering that the sixth amplifying switch tube Q26 needs to work in a specific working state to realize the corresponding signal amplification function, the logarithmic conversion module 1 is also provided with a seventh current bias module Q37 to provide a stable bias current for the sixth amplifying switch tube Q26. At the same time, the control end of the eighth conversion switch tube Q18 is connected to the first preset bias voltage to ensure its stable bias and ensure its logarithmic conversion function. The specific type of the seventh current bias module Q37 and the specific value of the bias current it provides and other implementation methods are not specifically limited in this application. The specific value and implementation method of the first preset bias voltage are not specifically limited in this application, and can be set and adjusted according to the actual application of the fourth conversion switch. Fig.16 As shown, the seventh current bias module Q37 can be implemented by an NMOS tube with a source grounded and a gate connected to a preset fixed bias voltage Vbias2.

[0126] Specifically, the logarithmic conversion module 1 composed of the sixth amplifying switch tube Q26, the eighth conversion switch tube Q18 and the seventh current bias module Q37 can be used to realize the logarithmic conversion of the photocurrent flowing through the photosensitive pixel. The entire circuit structure is simple and easy to implement, which is conducive to the simple implementation of the entire readout circuit.

[0127] To solve the above technical problems, the present invention also provides an image sensor, including photosensitive pixels and a light signal readout circuit as described above, wherein the input end of the light signal readout circuit is connected to the photosensitive pixels for converting the light signals captured by the photosensitive pixels into electrical signals.

[0128] It is not difficult to understand that a single photosensitive pixel or multiple photosensitive pixels can be set in the image sensor according to the actual application situation, or a pixel array composed of multiple photosensitive pixels can be directly used to implement it. Multiple photosensitive pixels can directly use the same light signal readout circuit to realize the readout of the light signal. It is only necessary to set the corresponding selection switch in the readout circuit to control the accurate readout of the light signal corresponding to each photosensitive pixel, thereby greatly simplifying the circuit structure in the image sensor and reducing the cost and volume. When the number of photosensitive pixels is relatively small, a readout circuit corresponding to each photosensitive pixel can also be set to respectively realize the readout of the light signal corresponding to each photosensitive pixel. The specific setting method of the photosensitive pixels and the corresponding readout circuit in the image sensor is not particularly limited in this application, and can be set and adjusted according to the actual application situation.

[0129] For an introduction to an image sensor provided by the present invention, please refer to the embodiment of the optical signal readout circuit described above, and the present invention will not be described in detail here.

[0130] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the embodiments can be referred to each other. It should also be noted that in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also other elements that are not explicitly listed, or also include elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements.

[0131] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A readout circuit for an optical signal, characterized in that: include: A logarithmic conversion module, whose input end is connected to a photosensitive pixel, and is used to perform logarithmic conversion on a photocurrent flowing through the photosensitive pixel to generate a voltage signal having a logarithmic relationship with the photocurrent; An output buffer module, whose input end is connected to the output end of the logarithmic conversion module, is used for buffering the voltage signal and then outputting it.

2. The optical signal readout circuit according to claim 1, characterized in that: The output buffer module comprises: A source follower, whose control end is connected to the output end of the logarithmic conversion module, and is used to amplify and output the voltage signal output by the logarithmic conversion module; The first current bias module has an output end connected to one end of the source follower and serves as the output end of the output buffer module, and is used to provide a bias current for the source follower.

3. The optical signal readout circuit according to claim 2, characterized in that: The image sensor includes a pixel array composed of a plurality of photosensitive pixels; the readout circuit also includes: A selection switch, the control end of which is connected to an output selection signal, the first end of which is connected to one end of the source follower, and the second end of which is connected to the output end of the first current bias module, is used to turn on when the photosensitive pixel is selected for output, and to turn off when the photosensitive pixel is not selected for output.

4. The optical signal readout circuit according to any one of claims 1 to 3, characterized in that: The first end of the photosensitive pixel is connected to the first power supply, and the second end is connected to the input end of the logarithmic conversion module, and the logarithmic conversion module includes: A-level first amplification unit; For any first amplifying unit, the first amplifying unit includes a first conversion switch tube and a first amplifying switch tube, the control end of the first amplifying switch tube is connected to the first end of the first conversion switch tube and serves as the first input end of the first amplifying unit, the first end of the first amplifying switch tube serves as the second input end of the first amplifying unit, the second end of the first conversion switch tube serves as the first output end of the first amplifying unit, and the control end of the first conversion switch tube is connected to the second end of the first amplifying switch tube and serves as the second output end of the first amplifying unit; The first input end of the first amplifier unit of the first stage is connected to the second end of the photosensitive pixel, the second input end of the first amplifier unit of the first stage is connected to the second power supply, the first output end of the A-th first amplifier unit is grounded, the first output end of the i-th first amplifier unit is connected to the first input end of the i+1-th first amplifier unit, and the second output end of the i-th first amplifier unit is connected to the second input end of the i+1-th first amplifier unit; A is a positive integer, and i is a positive integer less than A; The second current bias module has an output end connected to the second output end of the A-th level first amplification unit and serves as the output end of the logarithmic conversion module.

5. The optical signal readout circuit according to any one of claims 1 to 3, characterized in that: The first end of the photosensitive pixel is connected to the first power supply, and the second end is connected to the input end of the logarithmic conversion module, and the logarithmic conversion module includes: A second amplifying switch tube, a first end of which is connected to a second power supply; A second conversion switch tube, a first end of which is respectively connected to the control end of the second amplifying switch tube and the second end of the photosensitive pixel; A third conversion switch tube, a first end of which is respectively connected to the second end of the second conversion switch tube and the control end of the second conversion switch tube, and a second end of which is grounded; The third current bias module has an output end respectively connected to the control end of the third conversion switch tube and the second end of the second amplification switch tube, and serves as the output end of the logarithmic conversion module.

6. The optical signal readout circuit according to any one of claims 1 to 3, characterized in that: The first end of the photosensitive pixel is connected to the first power supply, and the second end is connected to the input end of the logarithmic conversion module, and the logarithmic conversion module includes: A third amplifying switch tube, a first end of which is connected to the second power supply; A fourth conversion switch tube, a first end of which is respectively connected to the control end of the third amplifying switch tube and the second end of the photosensitive pixel, and a control end is connected to a first preset bias voltage; The fourth current bias module has an output end connected to the second end of the fourth conversion switch tube and the second end of the third amplification switch tube respectively, and serves as the output end of the logarithmic conversion module.

7. The optical signal readout circuit according to any one of claims 1 to 3, characterized in that: The first end of the photosensitive pixel is grounded, and the second end is connected to the input end of the logarithmic conversion module, and the logarithmic conversion module includes: Class B second amplifier unit; For any second amplifying unit, the second amplifying unit includes a fifth conversion switch tube and a fourth amplifying switch tube, the control end of the fourth amplifying switch tube is connected to the first end of the fifth conversion switch tube and serves as the first input end of the second amplifying unit, the first end of the fourth amplifying switch tube serves as the second input end of the second amplifying unit, the second end of the fifth conversion switch tube serves as the first output end of the second amplifying unit, and the control end of the fifth conversion switch tube is connected to the second end of the fourth amplifying switch tube and serves as the second output end of the second amplifying unit; The first input end of the second amplifying unit of the first stage is connected to the second end of the photosensitive pixel, the second input end of the second amplifying unit of the first stage is grounded, the first output end of the second amplifying unit of the Bth stage is connected to the second power supply, the first output end of the second amplifying unit of the jth stage is connected to the first input end of the second amplifying unit of the j+1th stage, and the second output end of the second amplifying unit of the jth stage is connected to the second input end of the second amplifying unit of the j+1th stage; B is a positive integer, and j is a positive integer less than B; The fifth current bias module has an output end connected to the second output end of the second amplifying unit of the Bth stage and serves as the output end of the logarithmic conversion module.

8. The optical signal readout circuit according to any one of claims 1 to 3, characterized in that: The first end of the photosensitive pixel is grounded, and the second end is connected to the input end of the logarithmic conversion module, and the logarithmic conversion module includes: A fifth amplifying switch tube, a first end of which is grounded; a sixth conversion switch tube, a first end of which is respectively connected to the control end of the fifth amplifying switch tube and the second end of the photosensitive pixel; a seventh conversion switch tube, wherein a first end is respectively connected to the second end of the sixth conversion switch tube and the control end of the sixth conversion switch tube, and a second end is connected to the second power supply; The sixth current bias module has an output end respectively connected to the control end of the seventh conversion switch tube and the second end of the fifth amplification switch tube, and serves as the output end of the logarithmic conversion module.

9. The optical signal readout circuit according to any one of claims 1 to 3, characterized in that: The first end of the photosensitive pixel is grounded, and the second end is connected to the input end of the logarithmic conversion module, and the logarithmic conversion module includes: A sixth amplifying switch tube, a first end of which is grounded; An eighth conversion switch tube, wherein a first end is respectively connected to the second end of the photosensitive pixel and the control end of the sixth amplifying switch tube, and the control end is connected to a second preset bias voltage; The seventh current bias module has an output end connected to the second end of the eighth conversion switch tube and the second end of the sixth amplification switch tube respectively, and serves as the output end of the logarithmic conversion module.

10. An image sensor, characterized in that: It comprises a photosensitive pixel and a readout circuit of an optical signal as claimed in any one of claims 1 to 9, wherein an input end of the readout circuit of the optical signal is connected to the photosensitive pixel and is used to convert the optical signal captured by the photosensitive pixel into an electrical signal.

Images