CN111579068A - A photoelectric imaging sensor - Google Patents

Abstract

The invention discloses a photoelectric imaging sensor, which comprises a filter layer and an imaging unit, wherein the filter layer consists of a plurality of filter units, each filter unit comprises four filter zones, and the four filter zones allow red light, green light, blue light and wide spectrum light to pass through respectively; the imaging unit is used for receiving light rays penetrating through the filter layer and imaging, and comprises a visible light imaging unit and a single photon imaging unit, wherein the filter regions allowing red light, green light and blue light to pass correspond to the visible light imaging unit, the filter regions allowing wide-spectrum light rays to pass correspond to the single photon imaging unit, and the single photon imaging unit is used for receiving weak light signals penetrating through the wide-spectrum filter regions and amplifying the weak light signals at high times to generate images. The invention can generate a color image or a black-and-white night vision image based on the detected scene environment; the single photon imaging unit receives the weak light signal and amplifies the signal by high times to reach the photoelectric detection sensitivity range to generate an image, so that the sensitivity, the signal-to-noise ratio and the definition of the sensor are effectively improved.

Description

A photoelectric imaging sensor

technical field

The invention relates to the technical field of photoelectric detection, in particular to a photoelectric imaging sensor.

Background technique

As the society pays more and more attention to the security field, the scope of its application has gradually increased, and different users have also put forward more and higher requirements for its related equipment and technologies. As the core component of cameras and monitoring equipment, image sensors have a decisive impact on the image quality of the captured scene. Users' needs for security monitoring applications often require surveillance cameras to work 24 hours a day, even at night or in extremely weak light environments, they must be able to obtain clear, intuitive and accurate images.

Image sensors utilize the photoelectric conversion function of photoelectric devices. The light image on the photosensitive surface is converted into an electrical signal proportional to the light image. Compared with the photosensitive elements of "point" light sources such as photodiodes and phototransistors, the image sensor is a functional device that divides the light image on its light-receiving surface into many small units and converts them into usable electrical signals. Image sensors have the characteristics of small size, light weight, high integration, high resolution, low power consumption, long life and low price, and have been widely used. With the upgrade of user applications, the market needs imaging sensors with higher sensitivity to solve new applications such as low illumination, large dynamics, and wide spectrum.

Single-photon detection technology is a weak light detection technology that amplifies the photoelectron signal excited by a single or a small number of photons, and identifies and extracts extremely weak photoelectron signals through techniques such as pulse discrimination and accumulation, reaching the ultra-sensitive limit of photoelectric detection. Single-photon detection technology is used in high-resolution spectral measurement, non-destructive material analysis, high-speed phenomenon detection, precision analysis, atmospheric pollution measurement, bioluminescence, radiation detection, high-energy physics, astronomical photometry, optical time domain reflectometry, quantum encryption Distribution systems and other fields have a wide range of applications. The detectors used for single photon detection mainly include photomultiplier tube (PMT), avalanche photodiode (APD), single photon avalanche diode (SPAD), silicon photomultiplier tube (SIPM), intensified photoelectrode tube (IPD), electronic Multiplying CCD (EMCCD) and scientific grade sCMOS, etc. However, most of the existing single-photon detectors have certain limitations. For example, PMT has low quantum efficiency in the infrared band, large size, and is susceptible to external magnetic field interference; APD has low gain, high noise, peripheral control circuits and thermoelectricity. The refrigeration circuit is more complex and other disadvantages.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a photoelectric imaging sensor, which is compatible with visible light and low-light night vision imaging, and has the properties of large dynamic range, high resolution, high sensitivity, and wide detection spectral range. The specific technical scheme is as follows:

A photoelectric imaging sensor includes a filter layer and an imaging unit, the filter layer is composed of several filter units, each filter unit includes four filter areas, and the four filter areas respectively allow red light, Green light, blue light and broad-spectrum light; the imaging unit is used to receive light passing through the filter layer and perform imaging, including a visible light imaging unit and a single-photon imaging unit, allowing through the filter regions of red, green and blue light and Corresponding to the visible light imaging unit, the filter area that allows light to pass through the broad spectrum corresponds to the single-photon imaging unit, and the single-photon imaging unit is used to receive the weak light signal passing through the broad spectrum filter area and amplify the weak light signal with high multiples. Generate an image.

Further, the single-photon imaging unit includes a package tube and an optical window, the package tube and the optical window are combined to form a vacuum-sealed cavity, a photosensitive cathode and a single-photon imaging circuit are arranged in the vacuum-sealed cavity, and the photosensitive cathode grows. On the lower surface of the optical window, the single-photon imaging circuit is arranged on the opposite surface of the photosensitive cathode, and the photoelectrons released by the photosensitive cathode move to the single-photon imaging circuit under the action of an applied high voltage.

Further, the single-photon imaging circuit includes a high-voltage protection circuit, an acquisition circuit, an amplifying circuit, an ADC circuit and an interface circuit, and is prepared by using a standard CMOS process.

Preferably, the photosensitive cathode adopts one or more materials of type II superlattice of Si, Ge, GaAs, InGaAsP, InGaAs or InAs/GaAsSb and is prepared by MEMS technology.

Preferably, the vertical distance between the photosensitive cathode and the single-photon imaging circuit is greater than 1 mm.

Preferably, the single-photon imaging unit adopts wafer-level, ceramic or metal high-vacuum packaging, and the vacuum degree of the vacuum-sealed cavity is above 1×10 ^-3 Pa.

Further, the single photon imaging circuit adopts the MEMS process to process the growth photon reflection wall and the electron absorption well.

Further, a getter is also arranged in the vacuum-sealed cavity to maintain the vacuum degree in the cavity.

Further, the photoelectric imaging sensor also includes a polarizing layer, the polarizing layer is composed of several polarizing units, and the polarizing units are arranged in a matrix of two rows and two columns by four polarizers with different polarization angles. Corresponding to one filter unit, the filter layer is located between the polarizing layer and the imaging unit or the polarizing layer is located between the filter layer and the imaging unit.

Preferably, the angles of the polarization axes of the four polarizers are 0 degrees, 45 degrees, 90 degrees and 135 degrees, respectively.

Compared with the prior art, the beneficial effects of the present invention:

(1) The present invention generates a color image or a black and white image by setting four filter areas of red, green and blue and a wide spectrum, and corresponding the red, green and blue filter area to the visible light imaging unit, and the wide spectrum filter area to the single photon imaging unit. Night vision image, based on the tested scene environment and user-selected mode, supports color or low-light night vision imaging;

(2) The single-photon imaging unit in the present invention receives the weak light signal passing through the wide-spectrum light filtering area, and amplifies the weak light signal with a high multiple to reach the photodetection sensitive range to generate an image, which effectively improves the sensitivity and reliability of the sensor. noise ratio and sharpness;

(3) The present invention encapsulates the photosensitive cathode and single-photon imaging circuit in high vacuum based on MEMS technology, with high integration, which significantly reduces the size of the sensor; the photosensitive cathode can be made of various materials, and the 300nm-14um band can be realized by changing different materials. The reception of electromagnetic waves, so the spectral response range is wide.

Description of drawings

1 is an exploded schematic view of an embodiment of the present invention;

Fig. 2 is the structural representation of filter unit in the present invention;

3 is a schematic structural diagram of a single-photon imaging unit in the present invention;

4 is a schematic diagram of a single-photon imaging circuit in the present invention;

5a and 5b are exploded schematic views of another embodiment of the present invention;

FIG. 6 is a schematic structural diagram of a polarizing unit in the present invention.

Detailed ways

1 to 6, the embodiments of the present invention and the specific operation process will be described in detail, but the protection scope of the present invention is not limited to the following examples.

The present invention discloses a photoelectric imaging sensor, which includes a filter layer 1 and an imaging unit 2. As shown in FIG. 1, the filter layer 1 is composed of several filter units 11, and each filter unit 11 includes four filter units. In the region 111, the four filter regions 111 allow red light, green light, blue light and broad-spectrum light to pass through, respectively named as R, G, B, BR filter regions, as shown in FIG. 2 . The imaging unit 2 is used to receive the light passing through the filter layer 1 and perform imaging, and includes a visible light imaging unit 21 and a single-photon imaging unit 22 (the filled part in FIG. 1 ). It is allowed to pass through the red, green and blue filter areas corresponding to the visible light imaging unit 21, that is, the visible light imaging unit receives the light filtered through the red, green and blue filter areas to generate a color image, and this imaging method is often used for strong light during the day. Scenes. The filter area that allows the light of the broad spectrum to pass through corresponds to the single-photon imaging unit 22, where the broad spectrum includes the visible light band and the invisible light band. For example, the filter region of the infrared wavelength band is allowed to pass, the wide-spectrum filter region and the single-photon imaging unit are used for low-light night vision scenes, and the single-photon imaging unit 22 receives the weak light signal passing through the wide-spectrum filter region, and converts the weak light The optical signal is processed with high magnification to achieve the sensitive range of photodetection to generate black and white images. Here, the four filter areas can be integrally formed, or the four filter areas can be combined together to form a filter unit by gluing or the like. tightness between.

The present invention is based on user usage scenarios, and can select day mode or night vision mode. The implementation of day mode and night vision mode may be to set switches on the visible light imaging unit and the single photon imaging unit respectively, and select the closing and closing of the switch according to the user usage scenario. Disconnect to realize the selection of different modes. In different scene modes, the visible light imaging unit 21 or the single photon imaging unit 22 generates corresponding images. When the use scene is strong light during the day, the switch on the visible light imaging unit is closed, the switch on the single photon imaging unit is open, and the visible light imaging unit receives the light passing through the red, green and blue filter areas to generate a color image. In this mode The imaging principle has been widely used, such as a visible light camera, and will not be described in detail in the present invention. When the use scene is low-light night vision, the switch on the visible light imaging unit is turned off, and the switch on the single-photon imaging unit is closed. Signal amplification processing to achieve the sensitive range of photoelectric detection to generate black and white images. Of course, in the low-light night vision scene, the user can also choose to close the switch on the visible light imaging unit. The visible light imaging unit and the single-photon imaging unit work at the same time and are generated by image fusion. Color night vision image. It should be noted that in the low-light night vision scene, whether the visible light imaging unit works or not needs to be selected according to the actual situation on site. When the noise introduced by the visible light imaging unit is turned on, only the single-photon imaging unit is selected to work to generate black and white images.

Specifically, the single-photon imaging unit includes a packaging tube 221 and an optical window 222. As shown in FIG. 3, the packaging tube 221 is combined with the optical window 222 to form a vacuum-sealed cavity, and the optical window 222 is used for projecting optical signals. A photosensitive cathode 223 and a single-photon imaging circuit 224 are arranged in the vacuum-sealed cavity, the photosensitive cathode 223 is grown on the lower surface of the optical window 222, and the single-photon imaging circuit 224 is arranged on the opposite surface of the photosensitive cathode 223, and the photoelectrons released by the photosensitive cathode 223 are subjected to an external high voltage move to the single-photon imaging circuit 224 under the action of . The photosensitive cathode 223 is made of one or more materials selected from Si, Ge, GaAs, InGaAsP, InGaAs or InAs/GaAsSb type II superlattice and is fabricated by MEMS technology. By changing different materials, the photosensitive cathode 223 can realize the reception of electromagnetic waves in the 300nm-14um band, so the spectral response range of the present invention is very wide. The vertical distance between the photosensitive cathode 223 and the single-photon imaging circuit 224 is greater than 1 mm. According to different bias voltages, the distance between the photosensitive cathode 223 and the single-photon imaging circuit 224 is also different.

In the present invention, the single-photon imaging circuit 224 is used for receiving photoelectric signals, and processing and outputting the signals, as shown in FIG. And it is prepared by standard CMOS process. After single or multiple photons enter the photosensitive cathode 223 through the optical window 222, the photoelectric effect is triggered to generate photoelectrons, and the photoelectrons are accelerated and fly to the pixel structure anode (ie, the acquisition anode) on the acquisition circuit under the action of the high-voltage electric field, and bombarded by high-energy electrons. A large number of electron-hole pairs are generated inside the lower part to amplify the photoelectron signal at a high multiple, and then processed by the amplifying circuit and the ADC circuit, which effectively improves the overall signal-to-noise ratio, sensitivity and clarity. The interface circuit is used to realize the output of the signal. The entire single-photon imaging circuit is in an ultra-high vacuum working state.

In order to maintain the vacuum degree in the cavity, one or more getters 225 are also arranged in the vacuum-sealed cavity. Preferably, the getters 225 are film-type getters, which can be adhered to the lower surface of the optical window 222 .

The single-photon imaging unit adopts wafer-level, ceramic or metal high-vacuum packaging, and the vacuum degree of the vacuum-sealed cavity is more than 1x10 ^-3 Pa. The photosensitive cathode is prepared by MEMS process, and the single-photon imaging circuit is prepared by standard CMOS process. The overall use of wafer-level, ceramic or metal high vacuum packaging has high integration and its volume is significantly smaller than traditional products.

Light is a transverse wave, and the light vector may have various vibration states in the two-dimensional space perpendicular to the propagation direction of light. The imaging sensor is also provided with a polarizing layer 3. As shown in FIG. 5a and FIG. 5b, the polarizing layer 3 is composed of several polarizing units 31, and the polarizing units 31 are arranged in two rows by four polarizing plates 311 with different polarizing angles. The matrix of columns, for example, the angles of the polarization axes of the four polarizers are 0 degrees, 45 degrees, 90 degrees and 135 degrees respectively, which are arranged in a matrix of two rows and two columns, as shown in FIG. 6 . Each polarizer 311 corresponds to one filter unit 11, and the filter layer 1 is located between the polarizer layer 3 and the imaging unit 2 or the polarizer layer 3 is located between the filter layer 1 and the imaging unit 2. In actual use, you can The positions of the filter layer 1 and the polarizing layer 3 are flexibly set as required. In addition, when the optical filter layer 1 is located between the imaging unit 2 and the polarizing layer 3, since the polarizing layer 1 often uses metal gratings arranged at intervals, the polarizing layer 3 located between the imaging unit 2 and the optical filtering layer 1 will cause the optical filtering layer The placement of 1 is not flat, so it is preferable to choose to set the filter layer 1 between the polarizing layer 3 and the imaging unit 2, and the filter effect is better. The imaging unit 2 receives polarized light with different polarization angles passing through the corresponding filter area 111 , and can acquire polarized light with four different polarization angles in the photographed scene, thereby improving the utilization range of the photographed scene.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention. within.

Claims (10)

1. A photoelectric imaging sensor is characterized by comprising a filter layer and an imaging unit, wherein the filter layer consists of a plurality of filter units, each filter unit comprises four filter zones, and the four filter zones allow red light, green light, blue light and wide spectrum light to pass through respectively; the imaging unit is used for receiving light rays penetrating through the filter layer and imaging, and comprises a visible light imaging unit and a single photon imaging unit, wherein filter areas allowing red light, green light and blue light to correspond to the visible light imaging unit, the filter areas allowing wide-spectrum light to correspond to the single photon imaging unit, and the single photon imaging unit is used for receiving weak light signals penetrating through the wide-spectrum filter areas and amplifying the weak light signals at high times to generate images.

2. The photoelectric imaging sensor according to claim 1, wherein the single photon imaging unit comprises a packaging tube shell and an optical window, the packaging tube shell and the optical window are combined to form a vacuum sealed cavity, a photosensitive cathode and a single photon imaging circuit are arranged in the vacuum sealed cavity, the photosensitive cathode grows on the lower surface of the optical window, the single photon imaging circuit is arranged on the opposite surface of the photosensitive cathode, and photoelectrons released by the photosensitive cathode move to the single photon imaging circuit under the action of an external high voltage.

3. The optoelectronic imaging sensor of claim 2, wherein the single photon imaging circuit comprises a high voltage protection circuit, an acquisition circuit, an amplification circuit, an ADC circuit and an interface circuit, and is fabricated using standard CMOS processes.

4. The optoelectronic imaging sensor of claim 2, wherein the photo-sensing cathode is fabricated using one or more of Si, Ge, GaAs, InGaAsP, InGaAs, or InAs/GaAsSb class II superlattices in a MEMS process.

5. The optoelectronic imaging sensor of claim 2, wherein the vertical distance of the photo-sensing cathode from the single photon imaging circuitry is greater than 1 mm.

6. The optoelectronic imaging sensor of claim 2, wherein the single photon imaging unit is packaged in wafer level, ceramic or metal high vacuum, and the vacuum degree of the vacuum sealed cavity is 1x10^-3Pa or above.

7. The optoelectronic imaging sensor of claim 2, wherein the single photon imaging circuit is fabricated by using MEMS technology to grow photon reflecting walls and electron absorbing wells.

8. The optoelectronic imaging sensor of claim 2, wherein a getter is further disposed within the vacuum-sealed cavity for maintaining a vacuum within the cavity.

9. The optoelectronic imaging sensor according to any one of claims 1 to 8, further comprising a polarizing layer, wherein the polarizing layer is composed of a plurality of polarizing units, the polarizing units are arranged in a two-row and two-column matrix by four polarizing plates with different polarization angles, each polarizing plate corresponds to a filter unit, and the filter layer is located between the polarizing layer and the imaging unit or the polarizing layer is located between the filter layer and the imaging unit.

10. The optoelectronic imaging sensor of claim 9, wherein the angles of the polarization axes of the four polarizers are 0 degrees, 45 degrees, 90 degrees, and 135 degrees, respectively.

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