CN117954296A - Photoelectric detection device - Google Patents
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- CN117954296A CN117954296A CN202410046928.7A CN202410046928A CN117954296A CN 117954296 A CN117954296 A CN 117954296A CN 202410046928 A CN202410046928 A CN 202410046928A CN 117954296 A CN117954296 A CN 117954296A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J31/00—Cathode ray tubes; Electron beam tubes
- H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
- H01J31/50—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output
- H01J31/506—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output tubes using secondary emission effect
- H01J31/507—Image-conversion or image-amplification tubes, i.e. having optical, X-ray, or analogous input, and optical output tubes using secondary emission effect using a large number of channels, e.g. microchannel plates
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- H01L27/14—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation
- H01L27/144—Devices controlled by radiation
- H01L27/146—Imager structures
- H01L27/14643—Photodiode arrays; MOS imagers
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- H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by potential barriers, e.g. phototransistors
- H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
- H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier
- H01L31/107—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier working in avalanche mode, e.g. avalanche photodiodes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
- H04N25/67—Noise processing, e.g. detecting, correcting, reducing or removing noise applied to fixed-pattern noise, e.g. non-uniformity of response
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Abstract
The application discloses a photoelectric detection device, which comprises a control circuit, a wavelength conversion module and an avalanche detector, wherein the wavelength conversion module at least comprises a photocathode, a fluorescent screen and a first accelerating electric field; the incident light photons enter a photocathode to excite photoelectrons, and the photoelectrons are driven by a first accelerating electric field to move and enter a fluorescent screen to excite photons with specific wavelength; photons with specific wavelengths are detected by an avalanche detector and an electrical signal is output; the control circuit controls at least one of bias voltage of the photocathode and bias voltage of the avalanche type detector according to an incident light intensity signal I or an output signal of the avalanche type detector. The application effectively increases the whole dynamic range of the detection device through low-cost circuit arrangement and system transformation of the detector, and simultaneously, the avalanche detector has great internal gain, suppresses the noise generated by a reading circuit, can avoid the noise caused by a micro-channel plate, has controllable noise of the detection device and improves the quality of output signals.
Description
Technical Field
The present application relates to semiconductor devices, and more particularly, to a photodetection device.
Background
The conventional image Intensifier (ICCD) consists of photocathode, microchannel plate, phosphor screen and imaging system with CCD or CIS chip, and its working principle is as follows: after the light of an external detection target is incident, the light enters a photocathode, and the photocathode converts received photons into electrons through photoelectricity; electrons enter the micro-channel plate along with the electric field, and are continuously collided with the side wall of the micro-channel by utilizing the strong electric field in the micro-channel plate to ionize more electrons, so that the multiplication of the electron number and the amplification of signals are realized; these electrons then strike the phosphor screen to produce new photons; the newly generated photons enter a subsequent imaging structure, are received by a CCD or CIS chip, and formed imaging signals are finally output from a readout circuit.
The traditional image intensifier is multiplied by a microchannel plate, and an imaging chip CCD or CIS of the traditional image intensifier has no internal gain and cannot regulate and control imaging effects by controlling physical quantities such as voltage of pixels of the traditional image intensifier; at the same time, CCDs or CIS also have a fixed noise source. Therefore, for different application environments, different imaging distances and different light sources, the CCD and the CIS have relatively fixed imaging modes, the adjusting capability is relatively poor, and the imaging effect difference is relatively large.
With the effect of its microchannel plate multiplication, an image intensifier can detect very weak light, but its large noise is a key factor limiting its application. Noise of the image intensifier is mainly caused by the following aspects: electrons generated by photocathodes in dark conditions, electrons emitted by microchannel plates under strong electric fields, readout circuit noise of CCDs or CIS. To avoid the first two kinds of noise, a low voltage can be applied to the image intensifier, but the gain and detection efficiency of the image intensifier are reduced at the same time; and for the latter noise, the inherent property of the CCD or CIS, it is difficult to improve the device itself.
As a core imaging component of the image intensifier, a CCD or CIS chip essentially uses a diode built-in electric field to collect photo-generated carriers in a semiconductor, and thus reads a voltage signal through a subsequent circuit. For the two types of devices, the working voltage is basically fixed, and the performance of the devices cannot be adjusted by using the voltage; the gain in the interior is 1, that is, a single photo-generated carrier will only respond to the external generation of one unit charge, so that the single photo-generated carrier will need to be amplified and read in the subsequent circuit, which also means that the noise of the subsequent readout circuit will greatly affect the quality of the output image.
Because CIS and CCD have comparatively fixed imaging mode, traditional image intensifier regulating ability is relatively poor, and the noise is great and relatively fixed, hardly adjusts and controls different imaging environment, and the imaging effect difference is great. The current focus research direction for improving the imaging effect is focused on CCD pixel technology, circuit design and the like, and the cost is high and the effect is low.
Disclosure of Invention
The invention provides a photoelectric detection device aiming at the defects of the prior art.
The application adopts the following technical scheme: a photoelectric detection device comprises a control circuit, a wavelength conversion module and an avalanche type detector, wherein the wavelength conversion module at least comprises a photocathode, a fluorescent screen and a first accelerating electric field; the incident light photons enter a photocathode to excite photoelectrons, and the photoelectrons are driven by a first accelerating electric field to move and enter a fluorescent screen to excite photons with specific wavelength; photons with specific wavelengths are detected by an avalanche detector and an electrical signal is output; the control circuit controls the bias voltage of the avalanche type detector according to the incident light intensity signal I or the output signal of the avalanche type detector. Because the gain and noise of the avalanche detector under different bias voltages are different, the control circuit can change the internal gain and noise of the avalanche detector by regulating and controlling the bias voltage of the avalanche detector, so that the avalanche detector works under the optimal bias voltage. Therefore, the application effectively increases the whole dynamic range of the detection device through low-cost circuit arrangement and system transformation of the detector, and simultaneously, the avalanche detector has great internal gain, suppresses the noise generated by a reading circuit, can avoid the noise caused by a micro-channel plate, has controllable noise of the detection device and improves the quality of output signals.
For example, in some embodiments of the invention, the control circuit sets a threshold I2, and if the intensity of incident light I > the threshold I2, controls the bias voltage applied to the avalanche-type detector to operate in the linear mode; and if the incident light intensity I is less than or equal to the threshold I2, controlling the bias voltage applied to the avalanche type detector to enable the avalanche type detector to work in the cover grid mode. When the device works in a linear mode, the gain is smaller, but the noise is small, so that the device is suitable for detecting strong light environment; when the device works in the cover grid mode, the gain is large, and the device is suitable for detecting the low-light environment. Therefore, by utilizing different response modes of the avalanche detector under different bias voltages and changing the bias voltages, light with different incident intensities can output reasonable signal intensity, noise level is controlled, and imaging quality under different light intensities can be improved.
In a preferred embodiment of the invention, a control function V (I) is provided which is a function of the intensity of the incident light, and the magnitude of the bias voltage applied to the avalanche-type detector is adjusted in accordance with the function. Similarly, the gain of the avalanche detector is increased along with the increase of the bias voltage, the gain can be dynamically adjusted by using a control function, the output signal intensity of the avalanche detector is maintained in a reasonable interval, and the imaging effect of the detection device is more stable under different working environments through finer regulation and control, so that the imaging quality is kept good.
In some embodiments of the invention, the control circuit controls the bias voltage of the avalanche type detector and the bias voltage of the photocathode according to the incident light intensity signal I or the output signal of the avalanche type detector. After the control circuit further controls the photocathode bias voltage, the direction of the first accelerating electric field can be changed, when the first accelerating electric field is positive, electrons can pass through the accelerating electric field and bombard the fluorescent screen, the fluorescent screen further generates photons to enter the avalanche detector, and the whole detection device images the environment; when the direction of the first accelerating electric field is reversed, electrons generated by the photocathode cannot pass through the electric field, and the whole device does not image the environment. Such a method allows the imaging of the entire detection device to be controllable in the time dimension, i.e. the direction of the first accelerating electric field is controlled at different times to decide whether to image the environment or not; the forward and reverse occupation time ratio of the first accelerating electric field can also be controlled to control the number of photons entering the detector in unit time. Through synchronous regulation and control of photocathode and detector, play the effect that increases detection device whole detection dynamic range, reduces noise, be suitable for multiple environment.
Of course, as another technical scheme of the invention, the control circuit can also control the bias voltage of the photocathode based on the incident light intensity signal I or the output signal of the avalanche type detector, but not the bias voltage of the avalanche type detector. The high gain of the avalanche detector can be used for realizing the imaging of the low-light environment, but the dark noise of the avalanche detector is larger, and the problem of strong light imaging is solved (namely, the dead time of the avalanche process is greatly improved under the strong light intensity, the avalanche times and the photon number are not kept in good linear relation any more, and even the avalanche frequency is improved to burn out the avalanche). By utilizing the regulation and control of the photocathode, whether photocathode electrons enter the next imaging link or not can be controlled, the imaging effect of the avalanche detector is dark noise of the detector when the first accelerating electric field is reversed, so that the dark noise can be stored, and the external normal imaging can be filtered by the avalanche detector when the first accelerating electric field is forward. In addition, by utilizing the regulation and control of the photocathode, the photon number entering the detector can be reduced by controlling the forward and reverse occupation time ratio of the first accelerating electric field when external light is stronger, so that the detection device can normally image in a strong light environment.
As described above, the bias voltage of the photocathode can be controlled to control at least one of the magnitude and the direction of the first accelerating electric field. The electric field direction of the first accelerating electric field comprises a forward electric field and a reverse electric field, wherein the first accelerating electric field promotes photoelectrons to escape from the photocathode when in the forward electric field, and inhibits photoelectrons to escape from the photocathode when in the reverse electric field. The magnitude of the first accelerating electric field can control the photoelectric conversion efficiency of the photocathode photoelectric effect and the magnitude of generated dark noise, and when the magnitude of the first accelerating electric field is smaller, the photoelectric conversion efficiency of the photocathode is smaller, and the generated dark noise is also smaller; conversely, the greater the photoelectric conversion efficiency and noise.
In some embodiments of the present invention, the control circuit sets a threshold I0, and if the incident light intensity I > I0, controls the bias voltage of the photocathode to make the first accelerating electric field direction be in a positive-negative alternating state, so as to reduce the number of photons entering the avalanche detector during strong light, so that the avalanche detector can perform normal imaging, and increase the overall dynamic range of the detection device.
In some preferred embodiments of the present invention, the control circuit controls the photocathode electric field duty cycle according to the incident light intensity I; for example, a control function f (I) is set, which varies with the intensity of the incident light I, and has a magnitude that is the photocathode electric field duty cycle, i.e., the ratio of the time in the forward electric field to the time in the reverse electric field. When the light intensity is increased, the light duty ratio is continuously reduced by using the control function, so that the number of photons entering the avalanche detector is nearly constant, the stable and normal operation of the detector is ensured, and the overall dynamic range of the detection device is increased.
The control circuit includes a memory for storing system noise in the absence of signal input to modify the detected output signal. For example, prior to image acquisition, the control circuit controls the bias voltage of the photocathode such that the first accelerating electric field is a reverse electric field; storing the avalanche-type detector signal S0 at this time in a memory; during image acquisition, the control circuit controls the first accelerating electric field to be a forward electric field, the signal of the avalanche type detector is S1, and the signal in the memory is used for correcting the image signal output by the avalanche type detector at the moment, so as to output signals S1-S0. Therefore, dark noise of the avalanche detector can be filtered, and the integral imaging effect of the detection device is improved.
In some embodiments of the present invention, the wavelength conversion module includes a microchannel plate, photoelectrons escape from the photocathode under the drive of the first accelerating electric field and enter the microchannel plate for multiplication, and the multiplied electrons enter the fluorescent screen to excite more photons. The micro-channel plate is also connected with a control circuit, and the control circuit controls the second accelerating electric field in the micro-channel plate according to the output signal of the avalanche detector. Through the regulation and control of the second accelerating electric field, the multiplication times of electrons in the microchannel plate can be changed, so that the gain of the electron can be changed, and the two-stage compound regulation and control of the gain can be realized by combining the voltage regulation and control of the avalanche detector, so that the overall dynamic range of the detection device is increased.
In some embodiments of the present invention, the control circuit sets two thresholds I3 and I4, where I3< I4, and two electric fields of high and low in the microchannel plate, if the incident light intensity I is less than or equal to I3, the control circuit controls the microchannel plate to be in a high electric field to generate gain, and controls the bias voltage applied to the avalanche detector to operate in the grid mode; if I3 is less than or equal to I4, the control circuit controls the micro-channel plate to be in a low electric field so as not to generate gain, and controls the bias voltage applied to the avalanche detector so as to work in the cover grid mode; if I > I4, the control circuit controls the microchannel plate to be in a low electric field so as not to generate gain, and controls the bias voltage applied to the avalanche type detector to operate in a linear mode. By this method, when the incident light is strongest, the composite gain of the microchannel plate and the avalanche type detector is smallest; as the light intensity decreases, the composite gain of the two increases; as the light intensity further decreases, the composite gain increases to a maximum. Thus, the overall output signal intensity of the detection device is maintained in a certain range, and the dynamic range of the detection device is enlarged. Meanwhile, the electric field in the micro-channel plate is controlled as much as possible, and the ground noise introduced by the micro-channel plate is reduced.
In some preferred embodiments of the present invention, a control function E (I) is set, which uses the intensity of incident light as a variable, and the magnitude of the electric field in the microchannel plate is adjusted according to the control function E (I); meanwhile, when I is less than or equal to I4, the bias voltage applied to the avalanche type detector is controlled to work in the cover lattice mode, and when I is more than I4, the bias voltage applied to the avalanche type detector is controlled to work in the linear mode. The gain of the micro-channel plate can be finely regulated and controlled by using the control function E (I), so that the output signal strength is more stable, and meanwhile, the noise introduced by the micro-channel plate is reduced as much as possible by controlling the size of an internal electric field.
For some far weaker light sources, the photon number of imaging can be effectively increased by using larger pixels (with lower resolution), so that the success rate of detection is improved; for closer stronger light sources, imaging accuracy can be effectively improved by using smaller pixels (with higher resolution). In some embodiments of the present invention, the avalanche type detector is composed of a plurality of detection pixels, the control circuit sets a threshold I5, and if the incident light intensity I < I5, the output signals of more than two detection pixels are superimposed; if the incident light intensity I is greater than or equal to I5, single signal reading is carried out by using a single pixel. Therefore, high-intelligent output control is formed, and when the incident light intensity is too weak, a plurality of small-size detection pixels can be connected in parallel in a signal mode so as to enhance output signals. When the light intensity is large enough, only one small-size detection pixel is used for detection, so that the resolution is effectively ensured.
In some preferred embodiments of the present invention, a control function N (I) using the intensity of incident light as a variable is set, and the number of pixels used for single signal readout of the avalanche type detector is adjusted according to the function, so that the readout modes under different light intensities are precisely controlled by dynamically adjusting the function, and the resolution is improved as much as possible while the intensity of the readout signal is ensured.
Drawings
FIG. 1 is a schematic diagram of the detecting device of embodiment 1;
FIG. 2 is a schematic diagram of the detecting device of embodiment 2;
FIG. 3 is a schematic diagram of the detecting device of embodiment 3;
Fig. 4 is a schematic structural view of the detecting device of embodiment 4.
Detailed Description
1. Interpretation of the terms
The first accelerating electric field refers to an electric field in a space from the photocathode to its rear plane (front surface of the microchannel plate when the microchannel plate is present and phosphor screen surface when the microchannel plate is absent). The forward direction of the electric field is defined as the direction of the electric field in which electrons can move from the photocathode to the latter plane, i.e., from the latter plane toward the photocathode; the direction opposite to the forward direction is defined as the reverse direction of the electric field.
The second accelerating electric field refers to the electric field inside the microchannel plate. The forward direction of the electric field is defined as the direction of the electric field in which electrons can move from the front surface of the microchannel plate (on the side closer to the photocathode) to the rear plane of the microchannel plate (on the side closer to the phosphor screen), i.e., from the rear plane of the microchannel plate toward the front surface of the microchannel plate; the direction opposite to the forward direction is defined as the reverse direction of the electric field.
The third accelerating electric field refers to the electric field of the microchannel plate into the space of the rear phosphor screen.
Avalanche-type detectors refer to avalanche-type photodetectors including, but not limited to, avalanche photodiodes. Avalanche photodiodes are diodes operating under reverse bias, which have different signal types in different operating voltage intervals: the reverse breakdown voltage of the avalanche photodiode is recorded as Vbd, when the working voltage is larger than Vbd, the avalanche photodiode is in a grid mode, a single photon can enter the avalanche photodiode to generate a pulse signal (digital signal), and the gain reaches about 10 6; when the light source works at about 0.9Vbd, the generated current is proportional to photons absorbed by the light source, the signals are analog signals, the intensity information of the incident light can be conveniently provided, and the gain is about 10. The working voltage of the avalanche photodiode is adjusted to switch the working mode of the avalanche photodiode, so that different imaging requirements are met. In the prior art, the relatively mature avalanche type detector comprises silicon base, germanium base, gaN base, inGaAs base and the like.
Example 1
A silicon-based avalanche photodiode with a diameter of 50um was used for the test, and the breakdown voltage was 40V.
The method is characterized in that 37v voltage is applied to the detector, 550nm light is incident, the working mode is a linear mode, the detection efficiency is 10A/W, and the gain is about 50; when the voltage is adjusted to 44v, 550nm light is incident, the working mode is a Geiger mode, the single photon detection efficiency is 51%, and the gain is about 3.4X10 6; when the voltage is adjusted to 47v, 550nm light is incident, the operation mode is geiger mode, the single photon detection efficiency is 64%, and the gain is about 6×10 6. It can be seen that unlike CCDs, avalanche photodiodes can effectively change the gain of the detector by changing the bias voltage, so that different operating voltages can be selected for different incident light intensities, outputting a stable image.
The SPAD, an InP/InGaAs photocathode, a ZnS fluorescent screen and a control circuit are assembled to form a detection device, optical signal detection is carried out, 1550nm incident light is adopted, incident light photons enter the photocathode to excite photoelectrons, the photoelectrons are driven by a first accelerating electric field to move, enter the fluorescent screen, and photons of a specific wave band (with the center wavelength of 550 nm) are excited; photons of a specific wavelength are detected by an avalanche photodiode and an electrical signal is output; the control circuit controls the bias voltage of the avalanche photodiode according to the incident light intensity signal I or the output signal of the avalanche photodiode.
Specifically, an incident light intensity threshold I 2 is set to be 10 11ph/(mm2 s), and when the incident light intensity is higher than the incident light intensity threshold I 2, the SPAD voltage is set to be 37V, so that the SPAD works in a linear mode; when the incident light intensity is less than this value, the SPAD voltage is set to 44V, which allows it to operate in geiger mode.
Example 2
Testing with InP/InGaAs photocathodes, when the electric field applied thereto is 0, the quantum efficiency for 1550nm incident light is <1%; when the electric field applied to the light source is forward 1X10 6 V/m, the quantum efficiency of 1550nm incident light reaches 2%; when the electric field applied thereto was 1×10 6 V/m in the opposite direction, almost no electrons were received behind it.
The photocathode, the silicon-based avalanche photodiode, the ZnS fluorescent screen and the control circuit are assembled to form a detection device for detecting optical signals. The principle of operation is similar to that of example 1. The control circuit controls the voltage applied to the photocathode in accordance with the incident light intensity signal I or the output signal of the avalanche photodiode, thereby controlling the electric field applied to the photocathode.
Specifically, an incident light intensity threshold value I 0 is set to be 10 11ph/(mm2 s), when the incident light intensity is higher than the value, an electric field of 1X 10 6 V/m with positive and negative alternation is set on the photocathode, wherein the duration of the positive electric field is 1 mu s, and the duration of the negative electric field is 9 mu s; when the incident light intensity is smaller than the threshold I 0, the electric field on the photocathode is always set to be forward, and the magnitude is 1X 10 6 V/m.
Example 3
The test is carried out by adopting a microchannel plate with the thickness of 1mm and the micropore diameter of 10 mu m, and the gain is 2X 10 3 when the electric field applied on the microchannel plate is 1X 10 6 V/m; when the electric field applied thereto was 1.3X10 6 V/m, the gain thereof was 2X 10 5.
The microchannel plate is assembled with InP/InGaAs photocathodes, silicon-based avalanche photodiodes, znS phosphor screens and control circuitry to form a detector device. When the micro-channel plate works, 1550nm incident light is adopted, photons of the incident light enter a photocathode to excite photoelectrons, and the photoelectrons move under the drive of a first accelerating electric field and enter the micro-channel plate; under the drive of a second accelerating electric field, electrons collide and multiply in the micro-channel; the electrons are emitted from the microchannel plate, are driven by a third accelerating electric field, are incident on the fluorescent screen, and excite photons with specific wavelengths; photons of a specific wavelength band (the center wavelength is 550 nm) are detected by an avalanche photodiode, and an electric signal is output; the control circuit controls the voltage applied to the micro-channel according to the incident light intensity signal I or the output signal of the avalanche photodiode, thereby controlling the second driving electric field therein.
Specifically, an incident light intensity threshold I 3 is set to be 10 7ph/(mm2 s), and when the incident light intensity is higher than the incident light intensity threshold I 3, an electric field of 1X 10 6 V/m in the microchannel plate is set; when the incident light intensity is less than the threshold I 0, an electric field of 1.3X10 6 V/m in the microchannel plate is set. In addition, the avalanche photodiode operates in geiger mode
Example 4
The detection device of example 3 was used to control both the microchannel and the avalanche photodiode using a circuit. Based on the threshold I 3, a threshold I 4 is set to be 10 11ph/(mm2 s). When the incident light intensity I < I 3, setting an electric field of 1.3X10 6 V/m in the microchannel plate, biasing the avalanche photodiode to 44V, and operating in a Geiger mode; when I 4<I<I3 is set to an electric field of 1X 10 6 V/m in the microchannel plate, the avalanche photodiode is biased to 44V and works in the Geiger mode; when the incident light intensity I < I 3, an electric field of 1X 10 6 V/m in the microchannel plate is set, the avalanche photodiode is biased to 37V, and the linear mode is operated.
Example 5
With the detection device in embodiment 1, the control circuit controls the duty ratio of the photocathode electric field according to the incident light intensity I, that is, the ratio of the forward electric field to the reverse electric field, specifically, sets a control function f (I) of the duty ratio of the photocathode electric field with the incident light intensity I as a variable, so as to control the ratio of the forward electric field to the reverse electric field. f (I) is an inverse proportional function, namely:
A 0 is 10 11ph/(mm2 s), which can make the photon number received by SPAD approach to a constant in unit time, so that the SPAD has relatively stable working condition and the dynamic range of the whole device is enlarged.
Example 6
The detection device in embodiment 3 is used to adjust the electric field in the microchannel plate by taking the incident light intensity as a variable, specifically, a control function E (I) is used, namely:
E 0 is 6.5X10 4 V/m, ir is 2X 10 4ph/(mm2 s, E (I) is the electric field in the microchannel plate. Because the gain of the microchannel plate is about an exponential function of the electric field intensity, photons with different light intensities generate relatively stable numbers of electrons after passing through the photocathode and the microchannel plate in the electric field, and then generate relatively stable numbers of photons through the fluorescent screen, so that the SPAD has relatively stable working conditions, and the dynamic range of the whole device is enlarged.
Example 7
With the detection device in embodiment 1, the magnitude V (I) of the bias voltage applied to the avalanche type detector is adjusted by using the intensity of the incident light as a variable, and V (I) is a step function, namely:
In the formula, V bd is the breakdown voltage of SPAD, V 0～VN is a positive number, V 1～VN is an increasing voltage, I r0～Ir(N-1) is N reference light intensities, and when the light intensity is large enough (> I r0), the voltage is lower than the breakdown voltage, and the device works in a linear region; when I is smaller (< I r0), the voltage is greater than the breakdown voltage, and as the light intensity decreases, the voltage increases, so that the photon detection efficiency (Photon Detection Efficiency, PDE) of the SPAD increases, the ground signal can still be measured under the condition of weak light, the output signal intensity of the SPAD is stable, and the dynamic range of the whole device is enlarged.
Example 8
With the detection device in embodiment 1, the number N (I) of pixels used for single signal readout of the avalanche type detector is adjusted with the incident light intensity as a variable, where N (I) has the following form:
The square pixels form a square array according to the light intensity and are used as a single signal reading unit, and meanwhile, the number of photons received by the single signal reading unit is stable, so that the dynamic range of the whole device can be enlarged.
Claims (11)
1. The photoelectric detection device is characterized by comprising a control circuit, a wavelength conversion module and an avalanche detector, wherein the wavelength conversion module at least comprises a photocathode, a fluorescent screen and a first accelerating electric field; the incident light photons enter a photocathode to excite photoelectrons, and the photoelectrons are driven by a first accelerating electric field to move and enter a fluorescent screen to excite photons with specific wavelength; photons with specific wavelengths are detected by an avalanche detector and an electrical signal is output; the control circuit controls at least one of bias voltage of the photocathode and bias voltage of the avalanche type detector according to an incident light intensity signal I or an output signal of the avalanche type detector.
2. The device of claim 1, wherein the wavelength conversion module comprises a microchannel plate into which photoelectrons enter for multiplication after exiting the photocathode under the drive of the first accelerating electric field.
3. The device of claim 2, wherein the microchannel plate has a second accelerating electric field therein, the microchannel plate being connected to a control circuit, the control circuit controlling the second accelerating electric field in the microchannel plate in response to an output signal from the avalanche-type detector.
4. The photodetector device of claim 1 wherein said control circuit varies the bias voltage of the photocathode to control at least one of the magnitude and direction of the first accelerating electric field; the electric field direction of the first accelerating electric field comprises a forward electric field and a reverse electric field, wherein the first accelerating electric field promotes photoelectrons to escape from the photocathode when in the forward electric field, and inhibits photoelectrons to escape from the photocathode when in the reverse electric field.
5. The device of claim 4, wherein the control circuit sets a threshold I0, and controls the bias voltage of the photocathode such that the first accelerating electric field direction is alternately positive and negative if the incident light intensity I > I0.
6. The device of claim 4, wherein the control circuit controls the photocathode electric field duty cycle, i.e., the ratio of time in forward and reverse electric fields, based on the intensity of the incident light I.
7. The photodetection device according to claim 4, wherein the control circuit comprises a memory for storing system noise in the absence of signal input to modify the detected output signal. Before detection, the control circuit controls bias voltage of the photocathode so that the first accelerating electric field is a reverse electric field; storing the avalanche-type detector signal S0 at this time in a memory; during detection, the control circuit controls the first accelerating electric field to be a forward electric field, the signal of the avalanche type detector is S1, and the signal in the memory is used for correcting the image signal output by the avalanche type detector at the moment, so as to output signals S1-S0.
8. The device according to claim 1, wherein the control circuit sets a threshold I2, and controls the bias voltage applied to the avalanche type detector to operate in the linear mode if the incident light intensity I > the threshold I2; and if the incident light intensity I is less than or equal to the threshold I2, controlling the bias voltage applied to the avalanche type detector to enable the avalanche type detector to work in the cover grid mode.
9. The device according to claim 3, wherein the control circuit sets two thresholds I3 and I4, wherein I3< I4, and two electric fields of high and low in the microchannel plate, if the incident light intensity I is less than or equal to I3, the control circuit controls the microchannel plate to be in the high electric field to generate gain, and controls the bias voltage applied to the avalanche detector to operate in the grid mode; if I3 is less than or equal to I4, the control circuit controls the micro-channel plate to be in a low electric field so as not to generate gain, and controls the bias voltage applied to the avalanche detector so as to work in the cover grid mode; if I > I4, the control circuit controls the microchannel plate to be in a low electric field so as not to generate gain, and controls the bias voltage applied to the avalanche type detector to operate in a linear mode.
10. The photoelectric detection apparatus according to claim 1, wherein the avalanche type detector is composed of a plurality of detection pixels, the control circuit sets a threshold I5, and if the intensity of incident light I < I5, the output signals of two or more detection pixels are superimposed; if the incident light intensity I is greater than or equal to I5, a single detection pixel is used for single signal reading.
11. The detection system according to claims 1-10, wherein the avalanche type detector employs a silicon-based avalanche diode, a iii-v material avalanche diode or a germanium-based avalanche diode for detecting ultraviolet, visible or infrared light.
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| CN202410046928.7A CN117954296A (en) | 2024-01-12 | 2024-01-12 | Photoelectric detection device |
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