Collector, distance measurement system and electronic equipment

Abstract

The present invention discloses a collector, a distance measurement system and an electronic device, including a pixel unit composed of at least one macro pixel, each of which includes a plurality of pixels with different aperture factors, for collecting light spots reflected from targets at different distances in the field of view; wherein the pixels with a large aperture factor are configured to collect long-distance light spots, and the pixels with a small aperture factor are configured to collect short-distance light spots. By setting pixels with different aperture factors, the present invention avoids the situation where the signal light received on the pixels of the short-distance light spots is very strong, and the pixels are prone to saturation or pile-up effect, balances the reflected signal intensity of the measured objects at different distances received by the collector, reduces the variation range of the signal light intensity, and improves the distance measurement accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of optical distance measurement, and in particular to a collector, a distance measurement system and electronic equipment. Background Art

[0002] The time of flight principle (ToF) can be used to measure the distance of the target to obtain a depth image containing the target depth value. Further, based on the depth image, three-dimensional reconstruction, face recognition, human-computer interaction and other functions can be realized. Related distance measurement systems have been widely used in consumer electronics, unmanned driving, AR / VR and other fields. Distance measurement systems based on the time of flight principle often include a beam transmitter and a collector. The light source in the transmitter emits a beam to the target space to provide illumination, and the beam reflected back by the target is received by the collector. Among them, the collector includes a pixel array, which is generally a pixel array based on a single photon avalanche diode (SPAD). When a photon in the reflected light beam is incident on the SPAD, an avalanche event output signal can be triggered to record the time when the photon arrives at the pixel, based on which the time required for the light beam to be emitted to be received is calculated.

[0003] According to the optical path configuration between the transmitter and the collector, ToF measurement systems can be divided into two types: coaxial and off-axis. In the coaxial system, the transmitter and the collector often share a scanning device, such as a MEMS galvanometer, to achieve scanning of a large field of view. In the off-axis system, there is often no need for a scanning device, but more receiving components (such as a pixel array) are set up on the collector end, so as to measure the distance of multiple points in a large field of view at one time.

[0004] For off-axis ToF measurement systems, in order to receive reflected signals from objects at different distances, pixels are generally arranged in a two-dimensional array, and superpixels are turned on within the moving range of the light spot to receive signal light. However, since the intensity of reflected signals from objects at different distances is roughly inversely proportional to the square of the distance, this will cause the signal light received by pixels at close distances to be very strong, making these pixels prone to saturation or severe pile-up effects, resulting in inaccurate distance measurement.

[0005] The disclosure of the above-mentioned background technology content is only used to assist in understanding the inventive concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above-mentioned content has been disclosed on the filing date of this patent application, the above-mentioned background technology should not be used to evaluate the novelty and creativity of this application. Summary of the invention

[0006] The object of the present invention is to provide a collector, a distance measurement system and an electronic device to solve at least one of the above-mentioned background technical problems.

[0007] To achieve the above object, the technical solution of the embodiment of the present invention is implemented as follows:

[0008] A collector includes a pixel unit composed of at least one macro pixel, each of which includes multiple pixels with different aperture factors, so as to collect light spots reflected by targets at different distances in the field of view; the aperture factor is any value between 0 and 1; wherein pixels with a large aperture factor are configured to collect long-distance light spots, and pixels with a small aperture factor are configured to collect short-distance light spots.

[0009] In some embodiments, the pixel is configured with a shielding sheet to limit the light-incoming area of ​​the pixel through the shielding sheet, thereby reducing the light-sensitive area of ​​the pixel.

[0010] In some embodiments, the shielding film is a metal or non-metal light-shielding medium or coating disposed on the pixel.

[0011] In some embodiments, each pixel corresponds to one shielding sheet, and a plurality of shielding sheets are configured to have different opening factors.

[0012] In some embodiments, the shielding sheet is provided with an opening, and the signal light reflected by the target object to be measured is incident on the corresponding pixel through the opening.

[0013] In some embodiments, the opening shape of the shielding sheet can be square, rectangular, circular, polygonal or other irregular shapes.

[0014] In some embodiments, the shielding sheet may have one or more openings.

[0015] In some embodiments, the pixel is configured to have an adjustable photosensitive area size. By adjusting the photosensitive area size of each pixel, the photosensitive area size of each pixel is made different, so that the pixels have different aperture factors.

[0016] Another technical solution of the embodiment of the present invention is:

[0017] A distance measurement system comprises a collector and a transmitter as described in any of the above embodiments, and a processing circuit connected to the transmitter and the collector respectively; wherein:

[0018] An emitter, configured to emit a pulse light beam to a target area, wherein at least a portion of the pulse light beam is reflected by the target area to form a reflected pulse light beam;

[0019] A collector receives photons in the reflected pulse light beam to form a photon signal;

[0020] The processing circuit synchronizes the trigger signals of the transmitter and the collector, processes the photon signal, and calculates the distance information of the target to be measured based on the flight time of the reflected pulse light beam.

[0021] Another technical solution of the embodiment of the present invention is:

[0022] An electronic device, characterized in that it includes: a housing, a screen, and the distance measurement system described in the aforementioned embodiment; wherein a transmitter and a collector of the distance measurement system are arranged on the same surface of the electronic device, so as to emit a light beam to a target object and receive a light beam reflected back from the target object and form an electrical signal.

[0023] The beneficial effects of the technical solution of the present invention are:

[0024] Compared with the prior art, the present invention sets pixels with different opening factors so that the pixel irradiated by the distant light spot has a large opening factor, while the pixel irradiated by the close light spot has a small opening factor, thereby avoiding the situation where the signal light received on the pixel of the close light spot is very strong and the pixel is easily saturated or produces a pile-up effect. It balances the reflected signal intensity of the objects under test received by the collector at different distances, narrows the variation range of the signal light intensity, and improves the ranging accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be 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 paying creative labor.

[0026] Figure 1 is a schematic diagram of a distance measurement system according to an embodiment of the present invention.

[0027] Figure 2 is a schematic diagram of a collector according to an embodiment of the present invention.

[0028] Figure 3 It is a schematic diagram of the arrangement of the light shielding plate and the pixel array of the collector according to an embodiment of the present invention.

[0029] Figure 4 Schematic diagram of another arrangement of the pixel array of a collector according to an embodiment of the present invention.

[0030] Figure 5 Schematic diagram of another arrangement of the pixel array of a collector according to an embodiment of the present invention.

[0031] Figure 6is a schematic diagram of an electronic device according to another embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by the embodiments of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] It should be noted that when a component is referred to as being "fixed to" or "disposed on" another component, it can be directly on the other component or indirectly on the other component. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. In addition, connection can be used for fixing or for circuit connection.

[0034] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0035] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0036] Figure 1 The figure shows a schematic diagram of a distance measurement system according to an embodiment of the present invention. The distance measurement system 10 includes a transmitter 11, a collector 12, and a processing circuit 13 connected to the transmitter 11 and the collector 12, respectively. The transmitter 11 is used to transmit a light beam 30 to a target area 20, and the light beam 30 is transmitted to the target area space to illuminate the target object in the space; at least part of the transmitted light beam 30 is reflected by the target area 20 to form a reflected light beam 40, and at least part of the reflected light beam 40 is received by the collector 12; the processing circuit 13 is connected to the transmitter 11 and the collector 12, respectively, and synchronizes the trigger signals of the transmitter 11 and the collector 12 to calculate the time required for the light beam to be transmitted and reflected back to be received, that is, the flight time t between the transmitted light beam 30 and the reflected light beam 40. Further, the distance D of the corresponding point on the target object can be calculated by the following formula:

[0037] D=c·t / 2 (1)

[0038] Where c is the speed of light.

[0039] The transmitter 11 includes a light source 111, an emitting optical element 112, a driver 113, etc. Among them, the light source 111 can be a light emitting diode (LED), a laser diode (LD), an edge emitting laser (EEL), a vertical cavity surface emitting laser (VCSEL), etc., or it can be a one-dimensional or two-dimensional light source array composed of multiple light sources. Preferably, the light source array is a VCSEL array light source chip formed by generating multiple VCSEL light sources on a single semiconductor substrate, and the arrangement of the light sources in the light source array can be regular or irregular. The light beam emitted by the light source 111 can be visible light, infrared light, ultraviolet light, etc. The light source 111 emits a light beam outward under the control of the driver 113.

[0040] In one embodiment, the light source 111 emits a pulsed light beam at a certain frequency (pulse period) under the control of the driver 113, which can be used in direct time of flight (Direct TOF) measurement. The frequency is set according to the measurement distance, for example, it can be set to 1MHz-100MHz, and the measurement distance is from a few meters to hundreds of meters. It is understandable that a part of the processing circuit 13 or a subcircuit that exists independently of the processing circuit 13 can also be used to control the light source 111 to emit a light beam. In one embodiment, the light source 111 emits a continuous wave light beam with amplitude modulated, such as a sine or square wave continuous wave light beam, under the control of the processing circuit, which can be used in indirect time of flight (Indirect TOF) measurement.

[0041] The emission optical element 112 receives the light beam emitted from the light source 111 and shapes it to project it to the target area. In one embodiment, the emission optical element 112 receives the pulse light beam from the light source 111, and optically modulates the pulse light beam, such as diffraction, refraction, reflection, etc., and then emits the modulated light beam into space, such as a focused light beam, a flood light beam, a structured light beam, etc. The emission optical element 112 can be a combination of one or more of the forms of a lens, a liquid crystal element, a diffractive optical element, a microlens array, a metasurface optical element, a mask plate, a reflector, a MEMS galvanometer, etc.

[0042] The collector 12 includes a pixel unit 121, a filter unit 122 and a receiving optical element 123; wherein the receiving optical element 123 is used to receive at least part of the light beam reflected by the target and guide it to the pixel unit 121, and the filter unit 122 is used to filter out background light or stray light. The pixel unit 121 includes a two-dimensional pixel array composed of a plurality of pixels; in one embodiment, the pixel unit 121 is a pixel array composed of a single photon avalanche photodiode (SPAD), which can respond to a single incident photon and output a signal indicating the response arrival time of the received photon at each SPAD, and uses a method such as time-correlated single photon counting (TCSPC) to realize the collection of weak light signals and the calculation of flight time.

[0043] Generally, it also includes a readout circuit composed of one or more devices such as a signal amplifier, a time-to-digital converter (TDC), and a digital-to-analog converter (ADC) connected to the pixel unit 121. These circuits can be integrated with the pixel as a part of the collector, or as a part of the processing circuit 13, and are collectively defined as a part of the processing circuit 13 below.

[0044] The processing circuit 13 synchronizes the trigger signals of the transmitter 11 and the collector 12, processes the photon signal of the pixel collection light beam, and calculates the distance information of the target to be measured based on the flight time of the reflected light beam. In one embodiment, the SPAD responds to the incident single photon and outputs a photon signal, and the processing circuit 13 receives the photon signal and performs signal processing to obtain the flight time of the light beam. Specifically, the processing circuit 13 calculates the number of collected photons to form a continuous time bin, and these time bins are connected together to form a statistical histogram to reproduce the time series of the reflected light beam, and uses peak matching and filtering detection to identify the flight time of the reflected light beam from emission to reflection back to reception. It can be understood that the processing circuit 13 can be an independent dedicated circuit, such as a dedicated SOC chip, FPGA chip, ASIC chip, etc., and can also include a general processing circuit.

[0045] In some embodiments, the distance measurement system 10 further includes a memory for storing a pulse coding program, and the coding program is used to control the excitation time, emission frequency, etc. of the light beam emitted by the light source 111.

[0046] In some embodiments, the distance measurement system 10 may also include devices such as a color camera, an infrared camera, and an IMU. The combination of these devices can achieve richer functions, such as 3D texture modeling, infrared face recognition, SLAM, and other functions.

[0047] Reference Figure 2 As shown, Figure 2The figure is a schematic diagram of the structure of a collector 12 according to an embodiment of the present invention. The collector 12 includes a pixel unit 200; the pixel unit 200 includes at least one macro pixel 201, and each macro pixel 201 includes a plurality of pixels 202 with different aperture factors, so as to collect light spots reflected back from targets at different distances in the field of view; wherein, the long-distance light spot (the light spot reflected back from a long-distance target) is incident on a pixel with a large aperture factor, and the short-distance light spot (the light spot reflected back from a short-distance target) is incident on a pixel with a small aperture factor. Specifically, the pixels 202 with different aperture factors may be arranged regularly or irregularly, which is not particularly limited in the embodiment of the present invention. In one embodiment, as Figure 4 As shown, the reflected light spot is incident on the combined pixel 204 (for example, 4 pixels form a combined pixel), and the aperture factor of each pixel in the combined pixel can be configured to be the same or different.

[0048] In one embodiment, the collector further includes a readout circuit 300 , and the readout circuit 300 includes a TDC circuit and a histogram processing circuit, so as to process the photon signal and output a histogram containing photon flight time information.

[0049] Reference Figure 3 As shown, in one embodiment, a shielding sheet 203 is provided to realize that pixels have different aperture factors. Specifically, the collector 12 includes a pixel array and a plurality of shielding sheets 203; wherein the pixel array is a two-dimensional pixel array composed of a plurality of pixels, for sensing the signal light reflected back by the target object to be measured; the plurality of shielding sheets 203 are configured to have different aperture factors, so as to limit the light-incoming area of ​​the pixel by shielding the pixel, reduce the light-sensitive area of ​​the pixel, and limit the amount of light entering. Figure 3 As shown, the shielding sheet 203 is provided with an opening 2031, and the signal light reflected by the target object can be incident on the pixel 202 through the opening 2031; the white in the figure represents the opening of the shielding sheet, and one shielding sheet corresponds to one pixel. In the embodiment of the present invention, the opening of the shielding sheet is not adjustable; of course, in some other embodiments, the opening of the shielding sheet can also be set to be adjustable, and the number of shielding sheets is less than or equal to the number of pixels.

[0050] In some embodiments, the number of shielding sheets and the number of pixels may be the same or different; for example, in long-distance measurement, most pixels do not need to be shielded, so the number of shielding sheets and the number of pixels may be different, and the number of shielding sheets is less than the number of pixels. It is understood that in some embodiments, one shielding sheet may correspond to multiple pixels.

[0051] In some embodiments, the shielding sheet is a metal or non-metallic light-shielding medium or coating disposed on the pixel. The opening shape of the shielding sheet can be a square, rectangle, circle, polygon or other irregular shape. The number of openings of the shielding sheet can be one or more, and the position of the opening is not limited to the central position. Correspondingly, the unshielded portion of the pixel is not limited to the central position of the pixel.

[0052] In some embodiments, the pixel is designed to have an adjustable photosensitive area size. By adjusting the size of each pixel's photosensitive area, the photosensitive area size of each pixel is different, so that each pixel has a different opening factor. The opening factor of the pixel can be any value between 0 and 1. When the opening factor is 0, the area of ​​the pixel's photosensitive area is zero, the amount of light entering is zero, and the pixel cannot collect light spots; when the opening factor is 1, the area of ​​the pixel's photosensitive area is not reduced, and it is the area of ​​the pixel's photosensitive area under the initial normal condition. This time, the area of ​​the pixel's photosensitive area is the largest, the amount of light entering is the largest, and the pixel is allowed to collect more light signals. Pixels with different opening factors can be combined in any combination to form a pixel array, as long as the pixel array can adapt to changes in signal light intensity with position.

[0053] It should be noted that in the embodiments of the present invention, a shielding film is used or the pixel is designed to achieve different aperture factors for the pixel. In some other embodiments, the pixel can also have different aperture factors in other ways. The embodiments of the present invention will not be explained one by one by examples. No matter which method is adopted, as long as it does not deviate from the purpose of the invention, it should fall within the protection scope of the present invention.

[0054] Reference Figure 4-Figure 5 As shown, pixels with different aperture factors can be any combination of positions, as long as they can adapt to the change of signal light intensity with position, and the arrangement of pixels can be regular or irregular. Figure 4 The arrangement is regular, and the pixel opening factor is the same within the combined pixel. The pixel opening factor gradually decreases from left to right. Pixels with different opening factors collect light spots at long distances, medium distances, and short distances in turn. Figure 5 It is an irregular form, and the opening factors of pixels in the composite pixel are different, and the opening factor is any value between 0 and 1.

[0055] In one embodiment, when the emitter 11 emits a spot beam to the object to be measured, the spot beam is reflected by the object to be measured, and the pixel unit in the collector 12 guides the spot beam to the corresponding pixel, wherein the imaging spot of a single spot beam is incident on the corresponding "combined pixel" composed of multiple pixels. Figure 4The single spot shown corresponds to a combined pixel 204 composed of 4 pixels. The size of the combined pixel 204 can be specifically set according to the actual situation, including at least one pixel. For off-axis scanning, due to the existence of parallax, there will be displacement when the light spot is incident on the pixel at different distances of the measured object. Generally, the light spot will shift along the baseline direction. Therefore, all the combined pixels contained in the light spot that is affected by the parallax and shifted are combined into a macro pixel through a pre-calibrated method. When measuring the distance, all the pixels in the macro pixel are turned on, so that the combined pixels corresponding to the spots reflected back by the object at different distances within the measurement range all fall into the macro pixel area. In addition, the number of macro pixels determines the number of sampling points for the collector to complete a frame of measurement.

[0056] Reference Figure 2 As shown, the readout circuit includes a TDC circuit and a histogram processing circuit, which are used to process the photon signal to draw a histogram reflecting the pulse waveform emitted by the light source in the transmitter; further, the flight time can also be calculated according to the histogram, and the result is finally output. Among them, the readout circuit can be composed of a single TDC circuit and a histogram processing circuit, or it can be an array readout circuit composed of multiple TDC circuits and histogram processing circuits.

[0057] Reference Figure 6 As shown, Figure 6 Another embodiment of the present invention is an electronic device, which may be a desktop, table-mounted device, portable device, wearable device or vehicle-mounted device, robot, etc. Specifically, the device may be a laptop or electronic device to allow gesture recognition or biometrics. In other examples, the device may be a head-mounted device for identifying objects or dangers in the user's surroundings to ensure safety. For example, a virtual reality system that obstructs the user's vision of the environment may detect objects or dangers in the surroundings to provide the user with warnings about nearby objects or obstacles. In other examples, it may be a mixed reality system that mixes virtual information and images with the user's surroundings, and may detect objects or people in the user's environment to integrate virtual information with the physical environment and objects. In other examples, it may also be a device used in fields such as unmanned driving. Reference Figure 6 As shown, taking a mobile phone 400 as an example, the electronic device includes a housing 41, a screen 42, and the distance measurement system described in the aforementioned embodiment; wherein the transmitter and collector of the distance measurement system are arranged on the same surface of the electronic device, for emitting a light beam to a target object and receiving a light beam reflected back from the target object and forming an electrical signal.

[0058] It is to be understood that the above content is a further detailed description of the present invention in conjunction with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, it can also make several substitutions or modifications to these described embodiments, and these substitutions or modifications should be deemed to belong to the protection scope of the present invention. In the description of this specification, the description of reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention.

[0059] In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples without contradicting each other. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope defined by the appended claims.

[0060] Furthermore, the scope of the present invention is not intended to be limited to the particular embodiments of the processes, machines, manufactures, compositions of matter, means, methods, and steps described in the specification. One of ordinary skill in the art will readily appreciate that the above disclosures, processes, machines, manufactures, compositions of matter, means, methods, or steps, currently existing or to be developed, may be utilized to perform substantially the same functions as the corresponding embodiments described herein or to obtain substantially the same results as the embodiments described herein. Therefore, the appended claims are intended to include within their scope such processes, machines, manufactures, compositions of matter, means, methods, or steps.

Claims

1. A collector, characterized in that: A system for measuring off-axis distance, comprising a pixel unit of a two-dimensional array composed of at least one macro pixel, wherein all pixels included in the offset of a light spot due to parallax are combined into one macro pixel by a pre-calibrated method, and when measuring distance, all pixels in the macro pixel are turned on, so that all pixels corresponding to the spots reflected by objects at different distances within the measuring range fall within the macro pixel area; Each of the macro pixels includes a plurality of pixels with different aperture factors, so as to collect light spots reflected by targets at different distances in the field of view; the aperture factor is any value between 0 and 1; wherein the pixel with a large aperture factor is configured to collect the long-distance light spot, and the pixel with a small aperture factor is configured to collect the short-distance light spot; The pixel is configured to have an adjustable photosensitive area size. By adjusting the photosensitive area size of each pixel, the photosensitive area size of each pixel is made different, so that the pixels have different aperture factors.

2. The collector according to claim 1, characterized in that: The pixel is configured with a shielding sheet to limit the light-incoming area of ​​the pixel through the shielding sheet, thereby reducing the light-sensitive area of ​​the pixel.

3. The collector according to claim 2, characterized in that: The shielding film is a metal or non-metal light-shielding medium or coating disposed on the pixel.

4. The collector according to claim 2, characterized in that: Each pixel corresponds to one shielding sheet, and the plurality of shielding sheets are configured to have different opening factors.

5. The collector according to claim 4, characterized in that: The shielding sheet is provided with an opening, and the signal light reflected by the target object to be measured is incident on the corresponding pixel through the opening.

6. The collector according to claim 5, characterized in that: The opening shape of the shielding sheet can be square, rectangular, circular, polygonal or other irregular shapes.

7. The collector according to claim 5, characterized in that: The shielding sheet may have one or more openings.

8. A distance measurement system, characterized in that: It comprises a transmitter, a collector according to any one of claims 1 to 7, and a processing circuit connected to the transmitter and the collector respectively; wherein, An emitter, configured to emit a pulse light beam to a target area, wherein at least a portion of the pulse light beam is reflected by the target area to form a reflected pulse light beam; A collector receives photons in the reflected pulse light beam to form a photon signal; The processing circuit synchronizes the trigger signals of the transmitter and the collector, processes the photon signal, and calculates the distance information of the target to be measured based on the flight time of the reflected pulse light beam.

9. An electronic device, characterized in that: include: A housing, a screen, and a distance measurement system as described in claim 8; wherein the transmitter and collector of the distance measurement system are arranged on the same surface of the electronic device, so as to emit a light beam to a target object and receive a light beam reflected back from the target object and form an electrical signal.

Images