TOF sensor and distance detection method thereof

Abstract

A TOF sensor and a distance detection method thereof, the TOF sensor comprising: a light emitting module, comprising a light emitting device and a driving unit, the driving unit being used to control the on or off state of the light emitting device, the light emitting device and the driving unit being both arranged in the same common temperature region, the light emitting module being used to emit pulse detection light when the common temperature region reaches a preset temperature; a temperature sensing module being arranged in the common temperature region and being used to detect the temperature of the common temperature region; a feedback module being connected to the temperature sensing module and calculating a heat control strategy when the common temperature region is heated to a preset temperature according to the temperature of the common temperature region detected by the temperature sensing module; and a control module being connected to the light emitting module and the feedback module and being used to control the light emitting module to heat the common temperature region to a preset temperature according to the heat control strategy calculated by the feedback module. The difficulty of temperature compensation calibration of the detection result of the TOF sensor is reduced.

Description

Technical Field

[0001] The present invention relates to the field of sensing technology, and in particular to a TOF sensor and a distance detection method thereof. Background Art

[0002] The Time of Flight (TOF) method measures the three-dimensional structure or three-dimensional contour of the object by measuring the time interval from the emission to the reception of the pulse signal emitted by the measuring instrument or the phase generated by the laser going back and forth to the object. TOF measuring instruments can obtain grayscale images and distance images at the same time, and are widely used in many fields such as body control, behavior analysis, monitoring, autonomous driving, artificial intelligence, machine vision and automatic 3D modeling.

[0003] A time-of-flight (TOF) sensor generally includes: a light source module and a photosensitive module; the light source module is used to emit pulse detection light of a specific band and frequency, the detection light is reflected on the surface of the object to be measured, and the reflected light is received by the photosensitive module; the photosensitive module calculates the distance information of the object to be measured based on the time difference or phase difference between the emitted light wave and the received light wave.

[0004] The light source module includes a driving circuit and a light-emitting component. Since the driving circuit and the light-emitting component change with temperature, it will cause circuit delay or change in luminous efficiency. Generally, as the temperature rises, the delay of the electrical device becomes larger, and thus the timing changes. Light-emitting components, such as lasers and LEDs, also have a temperature range with higher luminous efficiency. Temperature changes will cause the luminous efficiency of the light-emitting components to change accordingly. For TOF sensors, changes in the light-emitting timing or luminous efficiency of the light source module will seriously affect the accuracy of distance measurement. For existing TOF sensors, every 1°C change in temperature will cause the driving circuit to delay by about 16.7ps, affecting the linear deviation of distance judgment by about 5mm, seriously affecting the measurement accuracy. The change in luminous efficiency caused by temperature will cause fluctuations in the signal-to-noise ratio, thereby affecting the accuracy of distance measurement.

[0005] In the prior art, a temperature sensing module is usually added to the light module circuit, and the detection result is calibrated for temperature compensation through an algorithm according to the temperature change. When the temperature range of the TOF sensor is large, in order to improve the detection accuracy, it is necessary to obtain calibration parameters at multiple temperatures, which requires more correction parameters, the calculation is complex, and the temperature change range of the algorithm correction is limited.

[0006] Therefore, how to reduce the impact of temperature changes on the detection accuracy of TOF sensors is a problem that needs to be solved urgently. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a TOF sensor and a distance detection method thereof, so as to reduce the difficulty of temperature compensation calibration of the TOF sensor.

[0008] In order to solve the above problems, the present invention provides a TOF sensor, including: a light-emitting module, including a light-emitting device and a driving unit, the driving unit is used to control the on or off state of the light-emitting device, the light-emitting device and the driving unit are both arranged in the same common temperature area, and the light-emitting module is used to emit a pulse detection light when the common temperature area reaches a preset temperature; a temperature sensing module, arranged in the common temperature area, and used to detect the temperature of the common temperature area; a feedback module, connected to the temperature sensing module, and calculating a heat control strategy for heating the common temperature area to a preset temperature according to the temperature of the common temperature area detected by the temperature sensing module; a control module, connected to the light-emitting module and the feedback module, and used to control the light-emitting module to heat the common temperature area to a preset temperature according to the heat control strategy calculated by the feedback module.

[0009] Optionally, the control module is connected to the light emitting device and is used to control a heating current passing through the light emitting device so that the light emitting device heats the common temperature area.

[0010] Optionally, the heating current is less than a light emitting current threshold of the light emitting device.

[0011] Optionally, the driving unit includes a switching element, which is connected between the cathode of the light-emitting device and the ground terminal, and a control source is connected to the control end of the switching element through a buffer; the control module is also connected to the control source, for controlling the pulse duty and frequency of the control source to control the heating time of the light-emitting device.

[0012] Optionally, a processing module is further included, in which calibration parameters at a preset temperature are stored, and the processing module is also used to calibrate the detection distance of the object to be measured according to the calibration parameters.

[0013] In order to solve the above problems, the technical solution of the present invention also provides a distance detection method of a TOF sensor, wherein the TOF sensor includes a light-emitting module, including: detecting the temperature of a common temperature area where the light-emitting module is located, wherein the light-emitting module includes a light-emitting device and a driving unit, and the light-emitting device and the driving unit are both arranged in the same common temperature area; heating the common temperature area to a preset temperature; after the temperature of the common temperature area reaches the preset temperature, stopping heating, and controlling the light-emitting module to emit a pulse detection light to detect the distance of the object to be measured to obtain the detection distance.

[0014] Optionally, the heating current passing through the light-emitting device is controlled so that the light-emitting device heats the common temperature area.

[0015] Optionally, the heating current is less than a light emitting current threshold of the light emitting device.

[0016] Optionally, the heating time of the light emitting device is controlled by controlling the turn-on time of the light emitting device.

[0017] Optionally, the detection distance of the object to be measured is calibrated according to calibration parameters at a preset temperature.

[0018] The TOF sensor and the distance detection method thereof of the present invention heat the light emitting device and the common temperature region where the driving unit is located to a preset temperature before emitting the detection light for distance detection, so that the distance detection is performed at the preset temperature. When the temperature compensation calibration of the detection distance is subsequently performed, only the calibration parameters at the preset temperature need to be used for calibration, thereby reducing the difficulty of the temperature compensation calibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of a TOF sensor according to a specific embodiment of the present invention;

[0020] Figure 2 A schematic diagram of the timing of the light emitting device and the detection light of a TOF sensor according to a specific embodiment of the present invention;

[0021] Figure 3 The figure is a flow chart of a distance detection method of a TOF sensor according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0022] The specific implementation of the TOF sensor and the distance detection method provided by the present invention are described in detail below with reference to the accompanying drawings.

[0023] Please refer to Figure 1 , is a schematic structural diagram of a TOF sensor according to a specific embodiment of the present invention.

[0024] The TOF sensor includes: a light emitting module, a temperature sensing module 102 , a feedback module 103 and a control module 104 .

[0025] The light emitting module includes a light emitting device D1 and a driving unit 1031, wherein the driving unit 1031 is used to control the on or off state of the light emitting device D1. The light emitting device D1 and the driving unit 1031 are both arranged in the same common temperature region 100, and the light emitting module is used to emit pulse detection light when the common temperature region 100 reaches a preset temperature.

[0026] In one specific embodiment, the light-emitting device D1 is a photodiode. In other specific embodiments, the light-emitting device D1 is a light-emitting device including a photodiode element, such as an LED diode, a laser diode or a VCSEL laser, etc. The greater the current of the light-emitting device D1, the greater the light intensity emitted by the light-emitting device D1, and the greater the light power.

[0027] The driving unit 1031 includes a switch element M1, which is connected between the cathode of the light emitting device D1 and the ground terminal. The control source S1 is connected to the control terminal of the switch element M1 through a buffer B1, and is used to control the on-off state of the switch element M1, thereby controlling the on-off state of the light emitting device D1. The control source S1 can be a voltage source or a current source. Whether the light emitting device D1 emits light is controlled by the driving unit 1031, and the light emitting current of the light emitting device D1 is determined by the light source voltage VDD_LD input to the anode of the light emitting device D1. The switch element M1 can be composed of one or more semiconductor devices.

[0028] The light-emitting module also includes a capacitor C, one end of which is grounded, and the other end is connected to the output end of the adjustable voltage source module 1042, for stabilizing the anode terminal voltage VDD_LD of the light-emitting device D1 to prevent VDD_LD from changing rapidly. Due to the capacitive reactance of the capacitor C, when the output terminal voltage of the adjustable voltage source module 1042 changes, it takes a period of time for the anode terminal voltage VDD_LD of the anode terminal of the light-emitting module to be consistent with the output terminal voltage of the adjustable voltage source module 1042. The internal resistance of the connection between the output end of the adjustable voltage source module 102 and the capacitor C1 is R, and the single voltage adjustment time of the voltage input end of the light source module is T, T=τ=2π×RC. Since the resistance value of the internal resistance R is determined by the circuit and is difficult to adjust, the voltage adjustment time T of the voltage input end of the light source module can be adjusted by adjusting the value of the capacitor C.

[0029] The common temperature region 100 may be a circuit board, the light emitting device D1 and the driving unit 1031 are arranged in the same common temperature region 100, and the temperature of the light emitting device D1 and the driving unit 1031 jointly determine the temperature of the common temperature region 100. Other modules of the TOF sensor may be arranged on other circuit boards, so that the temperature of the common temperature region 100 is mainly affected by the light emitting device D1 and the driving unit 1031, thereby improving the accuracy of the temperature control of the common temperature region 100.

[0030] The temperature sensing module 102 is disposed in the common temperature region 100 and is used to detect the temperature of the common temperature region. The temperature sensing module 102 includes at least one temperature sensor, which is disposed in the common temperature region 100 and detects the temperature of the common temperature region 100 in real time.

[0031] The feedback module 103 is connected to the temperature sensing module 102 and is used to calculate a heat control strategy for heating the common temperature area 100 to a preset temperature according to the temperature of the common temperature area 100 detected by the temperature sensing module 102 .

[0032] The control module 104 is connected to the light emitting module and the feedback module 103, and is used to control the light emitting module to heat the common temperature area 100 to a preset temperature according to the heat control strategy calculated by the feedback module 103. The control module 104 includes a current control logic unit 1041 and an adjustable voltage source unit 1042. The current control logic unit 1041 is used to control the current input to the adjustable voltage source 1042 to control the voltage VDD_LD output by the adjustable voltage source 1042.

[0033] The temperature of the common temperature region 100 affects the luminous efficiency of the light emitting device D1 and the circuit delay of the driving unit 1031, causing the detection result of the TOF sensor to be related to the temperature of the common temperature region 100. Before the TOF sensor starts working, the temperature of the common temperature region 100 is the ambient temperature, so the ambient temperature will affect the detection accuracy of the TOF sensor.

[0034] The temperature sensing module 102 detects the temperature of the common temperature region 100, and the feedback module 103 obtains a heat control strategy for heating the common temperature region 100 to a preset temperature according to the temperature detected by the temperature sensing module 102, and feeds back the strategy to the control module 104. Since the light emitting device D1 and the driving unit 1031 are disposed in the common temperature region 100, the control module 104 can heat the common temperature region by controlling the light emitting device D1 and the driving unit 1031.

[0035] In a specific embodiment of the present invention, the heat control strategy includes controlling the heating of the light emitting device D1 and / or the driving unit 1031 .

[0036] In this specific implementation, the control module 104 is connected to the light emitting device D1, and is used to control the heating current passing through the light emitting device D1, so that the light emitting device D1 heats the common temperature region 100. When the driving unit 1031 controls the light emitting device D1 to be turned on, the control module 104 controls the voltage VDD_LD output to the anode end of the light emitting device D1, thereby adjusting the current flowing through the light emitting device D1. Since the heating of the common temperature region 100 is performed before the TOF sensor performs distance detection, the heating current is less than the light emitting current threshold of the light emitting device D1. Therefore, before the light emitting device D1 is heated, the light emitting device D1 will not emit light, but is only equivalent to a resistor, generating heat, thereby increasing the temperature of the common temperature region 100. The feedback module 103 can obtain the temperature of the common temperature region 100 detected by the temperature sensing module 102 in real time, and adjust the heat control strategy in time.

[0037] In another specific embodiment, the control module 104 is also connected to the control source S1, and is used to control the pulse duty cycle and frequency of the control source S1. The control source S1 is used to control the on and off state of the switch element M1. By controlling the duty cycle and frequency of the control source S1, the conduction frequency and the conduction time of each time of the switch element M1 can be controlled, thereby controlling the conduction frequency and the conduction time of each time of the light-emitting element D1, and finally realizing the control of the heating efficiency of the light-emitting element D1. For example, the control source S1 is a pulse control signal, and when it is at a high level, it controls the switch element M1 to turn on; the control module 104 can control the pulse width and pulse frequency of the control source S1, so that the switch element M1 can be periodically turned on and off; thereby, the light-emitting device D1 can periodically heat the common temperature area 100.

[0038] In other specific implementations, the size of the control source S1 may be controlled so that the switch element M1 operates in a linear region or a cut-off region, thereby adjusting the heat of the driving unit 1031 and heating the common temperature region 100 through the driving unit 1031 .

[0039] When the common temperature region 100 is heated to a preset temperature, the control module 104 adjusts the conduction current of the light emitting device D1 and controls the driving unit 1031 so that the light emitting device D1 emits pulse detection light to detect the distance to the object to be detected.

[0040] During the distance detection process, the temperature sensing module 102 detects the temperature of the common temperature area 100 in real time. When the temperature of the common temperature area 100 drops, the common temperature area 100 can continue to be heated to a preset temperature during the emission gap of the detection light. When the temperature of the common temperature area is greater than the preset temperature, the light-emitting module is turned off during the emission gap of the detection light, so that the common temperature area dissipates heat until the temperature drops to the preset temperature, and then the detection light is emitted to perform distance detection.

[0041] Please refer to Figure 2 In this specific implementation, before applying a stable periodic light-emitting current to the light-emitting device D1, a relatively small heating current Q1 is applied to the light-emitting device D1 for a period of time, and the light-emitting device D1 heats the common temperature region 100. Since the heating current Q1 is less than the light-emitting threshold current of the light-emitting device, the light-emitting device D1 does not emit detection light at this time.

[0042] The TOF sensor further includes a processing module, in which calibration parameters at a preset temperature are stored, and the processing module is further used to calibrate the detection distance of the object under test according to the calibration parameters. The TOF sensor further includes a sensing module, which is used to obtain the detection distance of the object under test.

[0043] In the above specific implementation manner, the TOF sensor only needs to calibrate the calibration parameters at a preset temperature. Even if the TOF sensor operates in a range where the ambient temperature changes greatly, there is no need to consider the actual ambient temperature when performing temperature compensation calibration on the detection distance. Only the calibration parameters at the preset temperature need to be used for calibration, thereby reducing the difficulty of temperature compensation calibration of the TOF sensor.

[0044] The preset temperature can be set according to the temperature that the TOF sensor is expected to reach in actual operation; the preset temperature is generally greater than the temperature range used by the TOF sensor. Regardless of the ambient temperature of the TOF sensor, before the TOF sensor performs distance detection, the light-emitting device D1 and the common temperature area where the driving unit 1031 is located are heated to the preset temperature. When the temperature compensation calibration of the detection distance is subsequently performed, only the calibration parameters under the preset temperature need to be used for calibration, thereby reducing the difficulty of the temperature compensation calibration of the detection distance of the TOF sensor and increasing the application temperature range of the TOF sensor.

[0045] In other specific implementations, two or more preset temperatures may be set, and the most suitable preset temperature may be selected according to the ambient temperature of the TOF sensor.

[0046] A specific embodiment of the present invention further provides a distance detection method of a TOF sensor.

[0047] Please refer to Figure 3 , the distance detection method of the TOF sensor comprises the following steps:

[0048] Step S1: Detecting the temperature of a common temperature region where a light emitting module is located, wherein the light emitting module comprises a light emitting device and a driving unit, and the light emitting device and the driving unit are both arranged in the same common temperature region.

[0049] Step S2: heating the common temperature area to a preset temperature.

[0050] The heating current passing through the light emitting device is controlled so that the light emitting device heats the common temperature region. The heating current is less than the light emitting current threshold of the light emitting device so that the light emitting device can only generate heat but not emit detection light.

[0051] In other specific implementations, the heating time of the light emitting device may be controlled by controlling the on-time of the light emitting device, thereby controlling the heating efficiency of the light emitting device.

[0052] In other specific implementations, the heat of the driving unit can be adjusted by controlling the switch element in the driving unit to operate in the linear region or the cut-off region, and the common temperature area can be heated by the driving unit.

[0053] Step S3: After the temperature in the common temperature area reaches a preset temperature, the heating is stopped, and the light emitting module is controlled to emit a pulse detection light to detect the distance of the object to be detected to obtain the detection distance.

[0054] During the distance detection process, the temperature of the common temperature area can continue to be detected in real time. When the temperature of the common temperature area drops below the preset temperature, the common temperature area can continue to be heated to the preset temperature during the emission gap of the detection light; when the temperature of the common temperature area is greater than the preset temperature, the light-emitting module is turned off through the emission gap of the detection light, so that the common temperature area dissipates heat until the temperature drops to the preset temperature, and then the detection light is emitted to perform distance detection.

[0055] The detection distance of the object to be measured is calibrated according to the calibration parameters at a preset temperature. The calibration parameters at the preset temperature may be stored in advance in the processing module of the TOF sensor. Even if the TOF sensor operates in a range where the ambient temperature varies greatly, when the detection distance is calibrated for temperature compensation, only the calibration parameters at the preset temperature need to be used for calibration, thereby reducing the difficulty of temperature compensation calibration of the TOF sensor.

[0056] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A TOF sensor, characterized in that: include: Common temperature area; A light-emitting module, comprising a light-emitting device and a driving unit, wherein the driving unit is used to control the on or off state of the light-emitting device, wherein the light-emitting device and the driving unit are both arranged in the common temperature region, wherein the temperature of the light-emitting device and the driving unit jointly determine the temperature of the common temperature region, wherein the light-emitting module is used to heat the common temperature region to a preset temperature, and emit a pulse detection light when the common temperature region reaches the preset temperature, wherein the driving unit comprises a switch element, wherein the switch element is connected between a cathode of the light-emitting device and a ground terminal, and a control source is connected to a control terminal of the switch element through a buffer; A temperature sensing module is disposed in the common temperature area and is used to detect the temperature of the common temperature area; A feedback module, connected to the temperature sensing module, and calculating a heat control strategy for heating the common temperature area to a preset temperature according to the temperature of the common temperature area detected by the temperature sensing module; A control module is connected to the light-emitting device, the control source and the feedback module, and is used to control the heating current passing through the light-emitting device according to the heat control strategy calculated by the feedback module, so that the light-emitting device heats the common temperature area, and control the pulse duty cycle and frequency of the control source to control the conduction frequency of the switching element and the time of each conduction, thereby controlling the conduction frequency of the light-emitting device and the time of each conduction, thereby controlling the heating time of the light-emitting device, and heating the common temperature area to a preset temperature.

2. The TOF sensor according to claim 1, characterized in that: The heating current is less than a light emitting current threshold of the light emitting device.

3. The TOF sensor according to claim 1, characterized in that: It also includes a processing module, in which calibration parameters at a preset temperature are stored. The processing module is also used to calibrate the detection distance of the object to be measured according to the calibration parameters.

4. A distance detection method of a TOF sensor, wherein the TOF sensor comprises a light emitting module, characterized in that: include: Detecting the temperature of a common temperature region where a light emitting module is located, wherein the light emitting module includes a light emitting device and a driving unit, wherein both the light emitting device and the driving unit are arranged in the common temperature region, wherein the temperature of the light emitting device and the driving unit jointly determine the temperature of the common temperature region, wherein the light emitting module is used to heat the common temperature region to a preset temperature, and emit a pulse detection light when the common temperature region reaches the preset temperature, wherein the driving unit includes a switch element, wherein the switch element is connected between a cathode of the light emitting device and a ground terminal, and a control source is connected to a control terminal of the switch element through a buffer; By controlling the heating current passing through the light-emitting device, the light-emitting device heats the common temperature area, and by controlling the pulse duty ratio and frequency of the control source to control the conduction frequency of the switch element and the conduction time of each time, thereby controlling the conduction frequency and the conduction time of each time of the light-emitting device, thereby controlling the heating time of the light-emitting device, the common temperature area is heated to a preset temperature; After the temperature in the common temperature area reaches a preset temperature, the heating is stopped, and the light emitting module is controlled to emit a pulse detection light to detect the distance of the object to be detected to obtain the detection distance.

5. The distance detection method according to claim 4, characterized in that: The heating current is less than a light emitting current threshold of the light emitting device.

6. The distance detection method according to claim 4, characterized in that: The detection distance of the object to be measured is calibrated according to the calibration parameters at the preset temperature.

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