CN217213116U

CN217213116U - Time of flight TOF sensing device

Info

Publication number: CN217213116U
Application number: CN202122139165.5U
Authority: CN
Inventors: 杨骁�; 史斌; 刘昆; ***
Original assignee: Shanghai Trance Microelectronics Technology Co ltd
Current assignee: Shanghai Trance Microelectronics Technology Co ltd
Priority date: 2021-09-06
Filing date: 2021-09-06
Publication date: 2022-08-16
Anticipated expiration: 2031-09-06

Abstract

The utility model provides a time of flight TOF sensing device, sensing device includes: the single photon avalanche diode SPAD array comprises SPAD pixel groups with N different sensitivities, wherein N is a natural number which is more than or equal to 2; logic control circuitry configured to be connected between the SPAD array and readout circuitry for controlling the SPAD pixel groups to be gated on or off as a function of measured distance; the readout circuit comprises a TDC and an SRAM, wherein the TDC is used for recording breakdown time information of an SPAD pixel group, and the SRAM is used for storing a histogram of the breakdown time information recorded by the TDC for being called by a controller.

Description

Time of flight TOF sensing device

Technical Field

The utility model relates to a 3D degree of depth sensing field to specifically, relate to the sensing controlling means of Time of Flight (Time of Flight, TOF) sensor.

Background

With the technical development of laser radar, Time of flight (TOF) has been receiving increasing attention, and the TOF principle is to obtain the distance to an object to be measured by continuously emitting light pulses to the object to be measured, receiving the light reflected from the object to be measured with a sensor, and detecting the Time of flight of the light pulses.

A TOF sensor is an active light sensor comprising at least two main parts, a transmitting device and a receiving device. The transmitting device transmits short pulse laser to irradiate the object to be measured, and part of the laser is reflected and then received by the receiving device.

In the case of short-distance measurement, since reflected light is strong, signal saturation may occur and distance measurement may not be performed, or a pile-up effect may occur, which may distort a recorded signal (histogram) and degrade the accuracy of distance measurement. Under strong background light, a Single Photon Avalanche Diode (SPAD) type detector may suffer from Avalanche breakdown before a real signal comes due to the influence of the background light, and the SPAD cannot respond to the real signal due to the limitation of dead time, so that the farthest detection distance is limited.

In view of the above technical problems, it is urgently needed to enhance the performance of the TOF 3D sensing device, so as to achieve accurate distance measurement of the TOF 3D sensing device in a distance measurement scene with strong light intensity at a short distance.

SUMMERY OF THE UTILITY MODEL

Solves the technical problem

During short-distance measurement, due to strong reflected light, the TOF sensor may be saturated to cause incapability of measuring distance or generate a stacking effect, so that a recorded signal is distorted, and the measurement precision is reduced.

Technical scheme

In order to solve the problem, the utility model provides a TOF sensing device with higher accuracy through the pixel group that configures the different sensitivity of multiunit in the SPAD array, and every group pixel can the independent control opening time to deal with the detection of different distances. In addition, the same multi-event time-to-digital converter is multiplexed by a plurality of groups of pixels, and the corresponding TDC and SRAM resources are multiplexed in a time-sharing manner, so that the resources of the TDC and the SRAM are saved to the greatest extent, the efficiency of the device is improved, and the cost is reduced.

The utility model provides a time of flight TOF sensing device, include: the SPAD array comprises SPAD pixel groups with N different sensitivities, wherein N is a natural number greater than or equal to 2; logic control circuitry configured to be connected between the SPAD array and readout circuitry for controlling the SPAD pixel groups to be gated on or off as a function of measured distance; the reading circuit comprises a TDC and an SRAM, wherein the TDC is used for recording breakdown time information of an SPAD pixel group, and the SRAM is used for storing a breakdown time information histogram recorded by the TDC for being called by a controller.

The utility model provides a time of flight TOF sensing device, wherein, SPAD pixel group is including the SPAD pixel group that has high sensitivity, has the SPAD pixel group of middle sensitivity and has the SPAD pixel group of low sensitivity.

The utility model provides a time of flight TOF sensing device, wherein, the sensitivity of SPAD pixel group passes through: different pixel sizes, different fill efficiencies, different transmittance filters, and different overload voltages.

The utility model provides a time of flight TOF sensing device, wherein, logic control circuit is configured to when measuring the distance and being less than first threshold value, gates the SPAD pixel group that has low sensitivity in first time quantum.

The utility model provides a time of flight TOF sensing device, wherein, logic control circuit is configured to when measuring the distance and being greater than the second threshold value, gates the SPAD pixel group that has high sensitivity in the second time quantum.

The utility model provides a time of flight TOF sensing device, wherein, logic control circuit is configured to when measuring the distance and being greater than first threshold and being less than the second threshold, gates the SPAD pixel group that has sensitivity in the third time quantum.

The utility model provides a time of flight TOF sensing device, wherein, first time quantum, second time quantum and third time quantum are according to the information dynamic adjustment of frame before.

The utility model provides a time of flight TOF sensing device, wherein, the N SPAD pixel group that has different sensitivity in the SPAD array is configured to interval arrangement each other for the pixel of same pixel group is not adjacent each other.

The utility model provides a time of flight TOF sensing device, wherein, logic control circuit is configured to control SPAD pixel group gates or shuts off to the pixel is opened at the interval.

Advantageous effects

Compared with the prior art, the utility model provides a sensing control method and device of TOF sensor possesses following beneficial effect: due to the existence of the low-sensitivity SPAD pixels, signal saturation and accumulation effects caused by too strong reflected light during short-distance ranging are avoided, and the short-distance ranging precision is effectively improved; the high-sensitivity pixels are turned on for a long distance, and the interference of background light is reduced; the SPAD array is started in a time-sharing manner, so that the dead time of the whole system is reduced; and the pixels are opened at intervals, so that the crosstalk between the pixels is effectively reduced.

Drawings

Figure 1 is a schematic diagram of a TOF sensing device according to an embodiment of the invention,

fig. 2 is a schematic diagram of a SPAD array according to an embodiment of the invention, an

Fig. 3 is a schematic diagram of the operational timing sequence of a SPAD array according to an embodiment of the invention.

Detailed Description

Before proceeding with the following detailed description, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document. The terms "couple," "connect," and derivatives thereof refer to any direct or indirect communication or connection between two or more elements, whether or not those elements are in physical contact with one another. The terms "transmit," "receive," and "communicate," as well as derivatives thereof, encompass both direct and indirect communication. The terms "include" and "comprise," as well as derivatives thereof, mean inclusion without limitation. The term "or" is inclusive, meaning and/or. The phrase "associated with … …" and derivatives thereof means including, included within … …, interconnected, contained within … …, connected or connected with … …, coupled or coupled with … …, in communication with … …, mated, interwoven, juxtaposed, proximate, bound or bound with … …, having an attribute, having a relationship or having a relationship with … …, and the like. The term "controller" refers to any device, system, or part thereof that controls at least one operation. Such a controller may be implemented in hardware, or a combination of hardware and software and/or firmware. The functionality associated with any particular controller may be centralized or distributed, whether locally or remotely. The phrase "at least one of, when used with a list of items, means that a different combination of one or more of the listed items can be used and only one item in the list may be required. For example, "at least one of A, B, C" includes any one of the following combinations: A. b, C, A and B, A and C, B and C, A and B and C.

Definitions for other specific words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.

In this patent document, the application combination of modules and the division levels of sub-modules are only for illustration, and the application combination of modules and the division levels of sub-modules may have different manners without departing from the scope of the present disclosure.

Fig. 1 is a schematic diagram of a TOF sensing device according to an embodiment of the invention.

Referring to fig. 1, the sensing control device of the time-of-flight TOF sensing device includes a SPAD array, a logic control circuit 140, a readout circuit, and a controller 130.

The SPAD array comprises SPAD pixel groups with N different sensitivities, wherein N is a natural number which is greater than or equal to 2. The SPAD array is capable of detecting the incidence of photons and outputting a pulse signal.

According to embodiments of the present invention, the sensitivity may be defined by a) different pixel sizes or fill efficiencies; b) filters of different transmittances; and c) different overload voltages.

According to the utility model discloses an embodiment, SPAD pixel group includes 1 or parallel connection's a plurality of SPAD pixel of the same sensitivity.

The logic control circuit 140 is configured to be connected between the SPAD array and the readout circuit for controlling the SPAD pixel group gating or turning off, wherein, according to the embodiment of the present invention, each SPAD pixel group can control the SPAD gating/turning off time via the external enable signal through the logic control circuit 140. In particular, the logic control circuit 140 may be configured to independently control the N SPAD pixel groups. For example, the logic control circuitry 140 may be configured to gate SPAD pixel groups of different sensitivities at different time periods depending on the measured distance. According to the embodiment of the present invention, the logic control circuit 140 can be configured to only open the lower SPAD pixel group of sensitivity in the closer distance to avoid the event to pile up the influence to the precision, in addition, the logic control circuit 140 can also be configured to only open the higher SPAD pixel group of sensitivity in the farther distance, in order to reduce the interference of background light. In addition, the logic control circuit 140 switches on (turns on) the SPAD pixel groups in the SPAD array in a time-sharing manner, thereby reducing the dead time of the whole system. In addition, the logic control circuit 140 can be configured to turn on (turn on) different SPAD pixel groups in the SPAD array in a time-sharing manner to turn on the pixels at intervals, so that crosstalk between the pixels is effectively reduced.

The readout circuit includes a Time To Digital Converter (TDC) 110 and a Static Random-Access Memory (SRAM) 120.

The TDC 110 is configured as a high-precision clock for recording breakdown timing information of SPAD pixels, that is, timing at which the SPAD array is broken down and generates a pulse signal.

The SRAM 120 stores SPAD breakdown time information recorded by the TDC 110 in the form of a histogram for storing a histogram about the breakdown time, i.e., a photon information histogram about the SPAD breakdown time information.

The controller 130 is configured to invoke and process data processing based on the histogram for the breakdown time.

Fig. 2 is a schematic diagram of a SPAD array according to an embodiment of the invention.

Referring to fig. 2, illustrated in fig. 2 is a SPAD array when N-3, in which pixel groups having different sensitivities are configured to be arranged spaced apart from each other such that pixels of the same pixel group are not adjacent to each other. Specifically, pixels in the second SPAD pixel group and the third SPAD pixel group are arranged at a pixel start interval in the second SPAD pixel group in the first row of the SPAD array; and arranging pixels in the third SPAD pixel group and the first SPAD pixel group at a pixel start interval in the third SPAD pixel group in a second row of the SPAD array, repeating the arrangement of the first row and the second row to form the SPAD array. With the array arrangement shown in fig. 2, when different SPAD pixel groups in the SPAD array are turned on (turned on) in a time-sharing manner by the logic control circuit 140, the pixels can be turned on at intervals to effectively reduce crosstalk between the pixels. Although the arrangement of SPAD arrays is shown in fig. 2 for N3, it will be understood by those skilled in the art that the principles of the present invention are equally applicable to SPAD arrays for other values of N without departing from the scope of the present invention.

Fig. 3 is a schematic diagram of the operation timing sequence of the SPAD array according to an embodiment of the present invention.

The timing diagram for the operation when N is 3 is shown in fig. 3, however, it should be understood by those skilled in the art that the principles of the present invention can be equally applied to SPAD arrays when N is other values without departing from the scope of the present invention.

Referring to fig. 3, in the first period T1, only the first SPAD pixel group having the lowest sensitivity is enabled; enabling the second SPAD pixel group with the intermediate sensitivity while continuing to keep the first SPAD pixel group on in the second time period T2; in the third period T3, all pixel groups including the third SPAD pixel group having the highest sensitivity are turned on. When the SPAD is subjected to avalanche breakdown, generating short pulses, transmitting the short pulses to the TDC through a logic control circuit, and recording the arrival time; and writing the time recorded by the TDC into the SRAM. And repeating the process after finishing the ranging of one frame and continuously working.

According to the embodiment of the present invention, the first time period T1, the second time period T2, and the third time period T3 may be dynamically adjusted according to information of previous frames.

According to an embodiment of the utility model, a method of controlling TOF sensing device is provided, including: dividing the measuring distances into N groups, wherein N is a natural number greater than or equal to 2; the method comprises the following steps of enabling and disabling N SPAD pixel groups with different sensitivities in the SPAD array according to the measured distance through a logic control circuit; and recording breakdown time information of the strobed SPAD pixel group through a readout circuit and storing a histogram about the breakdown time. And (5) completing the ranging of one frame, repeating the process and continuously working.

According to the utility model discloses a method of control TOF sensing device of embodiment still includes: gating the SPAD pixel groups with low sensitivity for a first time period when the measured distance is less than a first threshold; gating the SPAD pixel groups having low high sensitivity for a second time period when the measured distance is greater than a second threshold; and gating the SPAD pixel groups with medium and high acuity for a third time period when the measured distance is greater than the first threshold and less than the second threshold.

According to the utility model discloses a method of control TOF sensing device of embodiment still includes: and controlling the N SPAD pixel groups to be switched on or switched off so as to switch on the pixels at intervals.

Although the present disclosure has been described with exemplary embodiments, various changes and modifications may be suggested to one skilled in the art. The present disclosure is intended to embrace such alterations and modifications as fall within the scope of the appended claims.

None of the description in the present application should be read as implying that any particular element, step, or function is an essential element which must be included in the claim scope. The scope of patented subject matter is defined only by the claims.

Claims

1. A time-of-flight TOF sensing apparatus, comprising:

the single photon avalanche diode SPAD array comprises N SPAD pixel groups with different sensitivities, wherein N is a natural number more than or equal to 2;

logic control circuitry configured to be connected between the SPAD array and readout circuitry for controlling the SPAD pixel groups to be gated on or off as a function of measured distance;

the readout circuit comprises a time-to-digital converter (TDC) and a Static Random Access Memory (SRAM), the TDC is used for recording breakdown moment information of the SPAD pixel group, and the SRAM is used for storing a histogram of the breakdown moment information recorded by the TDC for being called by a controller.

2. The time of flight TOF sensing apparatus of claim 1, wherein the SPAD pixel groups comprise SPAD pixel groups with high sensitivity, SPAD pixel groups with intermediate sensitivity and SPAD pixel groups with low sensitivity.

3. The time-of-flight TOF sensing apparatus of claim 1, wherein the sensitivity of the SPAD pixel groups is determined by: different pixel sizes, different fill efficiencies, different transmittance filters, and different overload voltages.

4. The time-of-flight TOF sensing apparatus of claim 2, wherein the logic control circuitry is configured to gate the SPAD pixel groups having low sensitivity for a first period of time when the measured distance is less than a first threshold.

5. The time-of-flight TOF sensing apparatus of claim 2, wherein the logic control circuitry is configured to gate the SPAD pixel groups of high sensitivity for a second time period when the measured distance is greater than a second threshold.

6. The time-of-flight TOF sensing apparatus of claim 2, wherein the logic control circuit is configured to gate the SPAD pixel groups of medium sensitivity for a third time period when the measured distance is greater than the first threshold and less than the second threshold.

7. A time-of-flight TOF sensing apparatus according to claim 4 wherein said first time period is dynamically adjusted in accordance with information of a previous frame.

8. A time-of-flight TOF sensing apparatus according to claim 5 and wherein said second time period is dynamically adjusted in accordance with information of a previous frame.

9. A time-of-flight TOF sensing apparatus according to claim 6 wherein said third time period is dynamically adjusted in accordance with information of a previous frame.

10. The time-of-flight TOF sensing apparatus of claim 1, wherein the N SPAD pixel groups of different sensitivities in the SPAD array are arranged spaced apart from each other such that the pixels of the same pixel group are not adjacent to each other.

11. The time-of-flight TOF sensing apparatus of claim 1, wherein said logic control circuitry is configured to control said SPAD group of pixels to be turned on or off to turn on pixels at intervals.