Time-of-flight sensor capable of compensating for temperature drift and its temperature compensation method

Abstract

A time-of-flight sensor includes a light source, a first pixel, a second pixel, and a processor. The first pixel does not receive reflected light from an external object illuminated by the light source and generates a first output signal. The second pixel receives reflected light from the external object illuminated by the light source and generates a second output signal. The processor calculates a temperature-related offset compensation amount and an offset correction amount based on the first output signal, and corrects the distance calculated based on the second output signal accordingly.

Description

Technical Field

[0001] This invention relates to a time-of-flight sensor, and more particularly to a time-of-flight sensor and its temperature compensation method that corrects detection deviations caused by different operating temperatures by pre-storing offset compensation and offset correction amounts related to temperature changes. Background Technology

[0002] Please refer to Figure 1 The diagram shows a known time-of-flight sensor 100, which includes a light source 11 and a light sensor 13 disposed in two accommodating spaces of a package. The light source 11 projects emitted light toward an object outside the package, and the emitted light is reflected by the object to produce reflected light, which enters the package and is received by the light sensor 13.

[0003] Please refer to Figure 2 As shown, it is Figure 1 The timing diagram shows the output signal and pixel sampling signal of the time-of-flight sensor 100. The time from when light is emitted from the light source 11 until the light sensor 13 receives the reflected light from the object is called the time-of-flight T. tof This flight time T tof Multiplying half of the distance by the speed of light yields the distance between the object and the time-of-flight sensor 100.

[0004] However, the light source 11 generally exhibits temperature dependence, and different modulation parameters will be generated at different operating temperatures, for example, by Figure 2 Clock width T duty Changes and frequency T freq The error in distance measurement is caused by factors such as drift.

[0005] While it is known that compensation can be achieved by using a light source with low temperature dependence or by configuring an embedded temperature sensor to measure the operating temperature, these methods cannot effectively compensate for light source modulation time-of-flight sensors.

[0006] Therefore, a time-of-flight sensor that can effectively compensate for the temperature dependence of the light source of the time-of-flight sensor is needed. Summary of the Invention

[0007] This invention provides a time-of-flight sensor and a temperature compensation method thereof that uses a reference pixel to compensate for the temperature dependence of the detection results of the active pixel.

[0008] This invention provides a time-of-flight sensor comprising a light source, a photodetector, and a processor. The light source emits light according to a light source driving signal. The photodetector includes a first pixel and a second pixel. The first pixel receives a sampled signal and, at a reference temperature, generates a first reference output signal when the sampled signal has a first time delay difference with the light source driving signal and a second reference output signal when the sampled signal has a second time delay difference with the light source driving signal; and, at an operating temperature, generates a first operating output signal when the sampled signal has the first time delay difference with the light source driving signal and a second operating output signal when the sampled signal has the second time delay difference with the light source driving signal. The second pixel receives the sampled signal and, at the operating temperature, generates an operating detection signal when the sampled signal has the first time delay difference with the light source driving signal. The processor is configured to obtain a first reference phase-distance relationship based on the first reference output signal and the second reference output signal, and to obtain an operation phase-distance relationship based on the first operation output signal and the second operation output signal. It is also configured to calculate a temperature compensation amount and a temperature correction amount based on the first reference phase-distance relationship and the operation phase-distance relationship, and to correct the current phase obtained based on the operation detection signal using the temperature compensation amount and the temperature correction amount.

[0009] The present invention also provides a time-of-flight sensor comprising a light source, a photodetector, memory, and a processor. The light source emits light according to a light source driving signal. The photodetector includes a first pixel and a second pixel for generating an output signal based on a sampled signal. The memory is used to pre-record a first reference phase-distance relationship related to the first pixel at a reference temperature, as well as a detection compensation amount and a detection correction amount, which are obtained based on a second reference phase-distance relationship related to the second pixel at the reference temperature. The processor is used to calculate an operating phase-distance relationship related to the first pixel at an operating temperature, calculate a temperature compensation amount and a temperature correction amount based on the first reference phase-distance relationship and the operating phase-distance relationship, and correct the current distance using the temperature compensation amount, the temperature correction amount, the detection compensation amount, and the detection correction amount.

[0010] The present invention also provides a temperature compensation method for a time-of-flight sensor. The time-of-flight sensor includes a timing controller, a first delay circuit, a second delay circuit, a first pixel, a second pixel, and a light source. The first delay circuit is coupled to the light source, and the second delay circuit is coupled to the first pixel and the second pixel. The temperature compensation method includes the following steps: generating timing signals to the first delay circuit and the second delay circuit using the timing controller, and sequentially setting the first delay circuit and the second delay circuit to have a first delay time difference and a second delay time difference; generating a first reference output signal using the first pixel under a reference temperature and the first delay time difference; generating a second reference output signal using the first pixel under the reference temperature and the second delay time difference; obtaining and recording a first reference phase-distance relationship based on the first reference output signal and the second reference output signal; generating a first operation output signal using the first pixel under an operating temperature and the first delay time difference; generating a second operation output signal using the first pixel under the operating temperature and the second delay time difference; obtaining an operation phase-distance relationship based on the first operation output signal and the second operation output signal; calculating a temperature compensation amount and a temperature correction amount based on the first reference phase-distance relationship and the operation phase-distance relationship; and correcting the current phase obtained based on the operation detection signal generated by the second pixel at the operating temperature using the temperature compensation amount and the temperature correction amount.

[0011] The present invention also provides a time-of-flight sensor comprising a package, a light source, a first pixel, and a second pixel. The package includes a first accommodating space and a second accommodating space, wherein the first accommodating space communicates with a first opening and is covered by a top cover surrounding the first opening, and the second accommodating space communicates with a second opening. The light source is disposed within the first accommodating space. The first pixel is disposed within the first accommodating space and is used to receive reflected light from the light source projected onto the top cover. The second pixel is disposed within the second accommodating space and is used to receive reflected light from the light emitted by the light source, after being projected through the first opening of the first accommodating space onto an object outside the package and reflected by the light through the second opening of the second accommodating space.

[0012] To make the above and other objects, features and advantages of the present invention more apparent, a detailed description will be provided below with reference to the accompanying drawings. Furthermore, in the description of the present invention, the same components are denoted by the same reference numerals, which will be stated herein as well. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of a known time-of-flight sensor;

[0014] Figure 2 yes Figure 1 Timing diagram of the output signal and pixel sampling signal of the time-of-flight sensor;

[0015] Figure 3 This is a schematic diagram of a time-of-flight sensor according to an embodiment of the present invention;

[0016] Figure 4 This is a block diagram of the time-of-flight sensor according to an embodiment of the present invention;

[0017] Figure 5 yes Figure 4 Timing diagram of the control signals of the time-of-flight sensor;

[0018] Figure 6A This is a timing diagram of the output signal and sampling signal of the first pixel of the time-of-flight sensor in an embodiment of the present invention, wherein there is no time delay between the light source driving signal and the sampling signal;

[0019] Figure 6B This is a timing diagram of the output signal and sampling signal of the first pixel of the time-of-flight sensor according to an embodiment of the present invention, wherein there is a time delay difference between the light source driving signal and the sampling signal;

[0020] Figure 7A This is a timing diagram of the output signal and sampling signal of the second pixel of the time-of-flight sensor according to an embodiment of the present invention, wherein there is no time delay between the light source driving signal and the sampling signal;

[0021] Figure 7B This is a timing diagram of the output signal and sampling signal of the second pixel of the time-of-flight sensor according to an embodiment of the present invention, wherein there is a time delay difference between the light source driving signal and the sampling signal;

[0022] Figure 8 This is a graph showing the relationship between the detection phase and detection distance of the first and second pixels in the time-of-flight sensor of this invention at a reference temperature.

[0023] Figure 9 This is a graph showing the relationship between the detection phase and detection distance of the first pixel in the time-of-flight sensor of this invention under reference temperature and operating temperature.

[0024] Figure 10 This is a graph showing the relationship between the detection phase and detection distance of the second pixel in the time-of-flight sensor of this invention under reference temperature and operating temperature; and

[0025] Figure 11 This is a flowchart of a temperature compensation method for a time-of-flight sensor according to an embodiment of the present invention.

[0026] Explanation of reference numerals in the attached figures

[0027] 300 Time-of-Flight Sensor

[0028] 31 Light Source

[0029] 33. Photodetector

[0030] 331 First pixel

[0031] 332 Second pixel

[0032] 39 Package

[0033] 391 First Accommodation Space

[0034] 393 Second Accommodation Space

[0035] 395 Separation Wall

[0036] 41 Timing Controller

[0037] 431 First Delay Circuit

[0038] 433 Second Delay Circuit

[0039] 45 Light source driver

[0040] 47 Sampling Controller

[0041] 49 processors Detailed Implementation

[0042] The time-of-flight sensor of this invention uses an additional reference pixel to pre-record temperature compensation and temperature correction values ​​in memory. These temperature compensation and temperature correction values ​​are used to correct the phase and distance obtained during actual operation. The actual operation process includes two stages: the first stage is a pre-shipment setup stage, which records the reference phase-distance relationship related to the reference pixel at a reference temperature; the second stage is a power-on stage before each use, which records the operational phase-distance relationship related to the reference pixel at the operating temperature, and calculates the temperature compensation and temperature correction values ​​based on the reference phase-distance relationship and the operational phase-distance relationship to correct for temperature changes between the reference temperature and the operating temperature. This effectively eliminates the offset caused by temperature changes.

[0043] Please refer to Figure 3 The diagram shown is a schematic representation of a time-of-flight sensor 300 according to an embodiment of the present invention. The time-of-flight sensor 300 is used to detect the distance D of an object based on the time of flight of light. The time-of-flight sensor 300 includes a light source 31 and a photodetector 33 disposed within a package 39. It should be noted that, although... Figure 3The light source 31 and the photodetector 33 are disposed within the same package 39, but the present invention is not limited thereto. In other embodiments, the light source 31 and the photodetector 33 may be disposed in different packages. The following will use... Figure 3 The following example illustrates the implementation of the present invention.

[0044] Light source 31 emits a recognizable spectrum to illuminate objects outside the package 39. Light source 31 can be a coherent or non-coherent light source, such as a light-emitting diode or a laser diode.

[0045] The photodetector 33, for example, includes a CMOS sensor having a first pixel 331 and a second pixel 332, wherein the first pixel 331 and the second pixel 332 each include at least one photodiode or single-photon breakdown diode (SPAD) for detecting light energy and outputting an electrical signal. It must be noted that, although... Figure 3 The first pixel 331 and the second pixel 332 are configured in the same base layer, but the present invention is not limited thereto. In other embodiments, the first pixel 331 and the second pixel 332 may be configured in different base layers.

[0046] The package 39 has a first accommodating space 391 and a second accommodating space 393. The first accommodating space 391 communicates with a first opening and is covered by a top cover surrounding the first opening, and is used to accommodate a first pixel 331 and a light source 31, wherein the first pixel 331 is used to receive reflected light projected by the light source 31 onto the top cover of the package 39 (e.g., located above the first pixel 331). Since the first pixel 331 and the light source 31 are disposed together in the first accommodating space 391 and are close to each other, the flight time of the emitted light from the light source 31 to the first pixel 331 can be considered to be almost zero. The second accommodating space 393 communicates with a second opening and is used to accommodate a second pixel 332.

[0047] More specifically, part of the emitted light from the light source 31 is reflected by the interior of the first accommodating space 391 and received by the first pixel 331, while another part of the emitted light is projected through the first opening of the first accommodating space 391 to an object outside the package 39 and reflected, and then received by the second pixel 332 through the second opening of the second accommodating space 393.

[0048] The package 39 preferably also has a partition wall 395, such as Figure 3 As shown, it extends downward from the top cover to the surface of the base layer, and is used to separate the first accommodating space 391 and the second accommodating space 393, so that the second pixel 332 does not directly receive the emitted light from the light source 31, thereby reducing interference.

[0049] In some embodiments, a filter is further disposed at the first opening of the first accommodating space 391 to filter out light other than the emission spectrum of the light source 31, so as to reduce the detection interference of ambient light on the first pixel 331. Another filter is further disposed at the second opening of the second accommodating space 393 to filter out light other than the emission spectrum of the light source 31, so as to reduce the detection interference of ambient light on the second pixel 332.

[0050] Please refer to Figure 4 As shown, it is a block diagram of the time-of-flight sensor 300 according to an embodiment of the present invention, wherein... Figure 3 Identical components are indicated by the same symbols. In this invention, the time-of-flight sensor 300 also includes timing control circuitry (e.g., indicated by dashed boxes) for generating a light source drive signal to the light source 31, which can be selectively delayed (e.g., S). d2_d ) or not delayed (e.g., S) d2_nd The light source driver 45 then operates according to the light source driving signal S. d2_d or S d2_nd Drive the light source 31 to emit modulated light, for example by changing the driving voltage or driving current to modulate the emitted light of the light source 31.

[0051] The timing control circuit also sends a sampling signal S. d1 The light is directed to the photodetector 33. The sampling controller 47 of the photodetector 33 then operates based on the sampling signal S. d1 Read (e.g., through correlated double sampling, but not limited to) the charges of the first pixel 331 and the second pixel 332 to generate output signals S respectively. O1 and S O2 The timing control circuit is also used to control the sampling signal S. d1 With the light source driving signal S d2_d and S d2_nd The delay time difference between them. That is, whether or not there is a delay in this invention is, for example, whether there is a delay time difference between the light source driving signal and the sampling signal. The processor 49 then determines the delay time difference based on the output signal S. O1 and S O2 The calculation of compensation, correction, phase, and distance is illustrated below with examples.

[0052] In this invention, the processor 49 is selected, for example, from an ASIC and a digital signal processor (DSP), and is configured, for example, within the photodetector 33 and performs its computational functions in software, firmware and / or hardware.

[0053] In one embodiment, the timing control circuit includes, for example, a timing controller 41, a first delay circuit 431, and a second delay circuit 433. The timing controller 41 generates timing signals to the first delay circuit 431 and the second delay circuit 433. See, for example, [reference needed]. Figure 5As shown, timing controller 41 generates timing signal S syn The first delay circuit 431 is coupled to the light source 31, and it can delay the timing signal S. syn A delay time T d0 or T delay As a light source driving signal, it includes S d2_nd or S d2_d The second delay circuit 433 is coupled to the first pixel 331 and the second pixel 332, and it can also delay the timing signal S. syn A delay time T d1 Using as the sampling signal S d1 .

[0054] In one embodiment, other circuitry of the sampling controller 47 or the photodetector 33 further adjusts the sampling signal S. d1 Generate an inverted sampling signal S d1_inv (for example, refer to) Figures 6A to 7B Sampling signal S d1 and the inverted sampling signal S d1_inv It is used to read the charge of the first pixel 331 and the second pixel 332, wherein the sampling signal S is used. d1 Generate an inverted sampling signal S d1_inv The method of reading pixel charge is known and not the main purpose of this invention, so it will not be described in detail here.

[0055] It is understood that, although the timing signal S is illustrated using a square wave signal in the diagrams of this invention... syn Sampling signal S d1 and light source drive signal S d2_nd and S d2_d However, the present invention is not limited thereto. In other embodiments, the timing signal S syn Sampling signal S d1 and light source drive signal S d2_nd and S d2_d They can each have other different waveforms, depending on the actual application.

[0056] In this invention, the time-of-flight sensor 300 preferably further includes memory (e.g., volatile or non-volatile) for recording and storing in advance (e.g., during a pre-shipment setup phase) (1) a first reference phase-distance relationship associated with the first pixel 331 at a reference temperature; and (2) a detection compensation amount and a detection correction amount, which are obtained based on a second reference phase-distance relationship associated with the second pixel 332 at the reference temperature. The memory is also used to record and store (3) a temperature compensation amount and a temperature correction amount calculated at the operating temperature based on the operating phase-distance relationship associated with the first pixel 331 and the first reference phase-distance relationship before actual operation (e.g., during power-on). These stored parameters (1)-(3) are used to compensate and correct the detection phase or detection distance during actual operation, and are illustrated below.

[0057] Please refer to the following at the same time Figures 3 to 8 As shown, the method for recording temperature change parameters during the pre-shipment setup phase will be explained next. In this invention, the ambient temperature during the setup phase is set as a reference temperature, for example, 20°C to 30°C, but is not limited to this. Figure 5 As shown, the timing control circuit controls the sampling signals S sequentially. d1 With the light source driving signal S d2_nd and S d2_d With the first delay time difference T d0 and the second delay time difference T delay For ease of explanation, in this invention, the first delay time difference T is... d0 Choose approximately zero and the second delay time difference T delay The time difference is greater than zero, but the invention is not limited thereto. In other embodiments, the first delay time difference T d0 You can choose a value greater than zero.

[0058] At the reference temperature, when the sampling signal S d1 With the light source driving signal S d2_nd and S d2_d With the first delay time difference T d0 At that time, the first pixel 331 generates the first reference output signal S. O1_nd ,like Figure 6A As shown. As previously mentioned, due to the flight time T associated with the first pixel 331 tof Approximately zero and the first delay time difference T d0 The value is approximately zero, therefore the first reference output signal S O1_nd With the sampled signal S d1 Time difference T overall =0. When the sampled signal S d1 With the light source driving signal S d2_nd and S d2_d With a second delay time difference Tdelay At that time, the first pixel 331 generates the second reference output signal S. O1_d ,like Figure 6B As shown. Due to flight time T tof It is approximately zero, therefore T overall =T delay .

[0059] For example, when the first pixel 331 is a single pixel, the first reference output signal S O1_nd and the second reference output signal S O1_d This is the output signal of a single pixel; while when the first pixel 331 contains multiple pixels, the first reference output signal S O1_nd and the second reference output signal S O1_d The output signals of the plurality of pixels can be summed or averaged, and the summing or averaging can be implemented, for example, using the circuitry of the first pixel 331.

[0060] The processor 49 of the photodetector 33 or an external processor (since it is pre-shipped, an external calculator can be used for calculation) outputs the signal based on the first reference signal S. O1_nd and the second reference output signal S O1_d The first reference phase-distance relationship is obtained, for example. Figure 8 line segment L Rr Because the detection is not performed under ideal conditions, line segment L... Rr There is an offset from the ideal line segment, which is shown as phase offset and slope offset.

[0061] In one embodiment, line segment L Rr It utilizes two reference points RP r1 and RP r2 This is determined by, for example, the processor 49 or an external processor based on the first reference output signal S. O1_nd The first reference phase is obtained and based on the first delay time difference T d0 Find the first distance, so that in such a case Figure 8 The phase-range plane shown obtains the first reference point RP. r1 For example, processor 49 or an external processor calculates the area ratio according to the formula: area B1 / (area A1 + area B1) as the first reference phase, and according to the formula: speed of light × T d0 / 2, calculate the first distance. Finally, based on the calculated first reference phase (i.e., the first reference point RP) r1 The vertical axis value) and the first distance (i.e., the first reference point RP) r1 The first reference point RP can be obtained by taking the horizontal axis value. r1 .

[0062] Similarly, processor 49 or an external processor outputs the second reference signal S. O1_d The second reference phase is obtained (e.g., using the formula: area B2 / (area A2+area B2)) and based on the second delay time difference T. delay The second distance can be obtained (for example, by using the formula: speed of light × T). delay / 2), so as in Figure 8 The phase-range plane shown yields the second reference point RP. r2 Among them, the second reference point RP is obtained. r2 The method of obtaining the first reference point RP r1 The method is the same, so it will not be repeated here.

[0063] Next, the processor 49 or an external processor determines the time based on the first reference point RP. r1 and the second reference point RP r2 The first reference phase-distance relationship L is obtained by connecting the points on the phase-distance plane. Rr The first reference phase-distance relationship L Rr It is then recorded in memory.

[0064] At the reference temperature, when the sampling signal S d1 With the light source driving signal S d2_nd and S d2_d With the first delay time difference T d0 At that time, the second pixel 332 generates the first detection output signal S. O2_nd ,like Figure 7A As shown. During this stage, the object is positioned at a predetermined distance, therefore the predetermined flight time T tof Given that the first delay time difference T d0 When it is zero, the first detection output signal S O2_nd With the sampled signal S d1 Time difference T overall Approximately equal to the predetermined flight time T tof When the sampling signal S d1 With the light source driving signal S d2_nd and S d2_d With a second delay time difference T delay At that time, the second pixel 332 generates the second detection output signal S. O2_d ,like Figure 7B As shown. At this time, T overall =T tof +T delay .

[0065] Similarly, the second pixel 332 can be a single pixel or contain multiple pixels, used to directly output the first detection output signal S. O2_nd and the second detection output signal S O2_dAlternatively, the sum or average of the output signals from multiple pixels can be used as the first detection output signal S. O2_nd and the second detection output signal S O2_d .

[0066] Next, the processor 49 of the photodetector 33 or an external processor outputs the first detection signal S. O2_nd and the second detection output signal S O2_d The second reference phase-distance relationship is obtained, for example. Figure 8 line segment L Ar Because the detection is not performed under ideal conditions, line segment L... Ar There is an offset between it and the ideal line segment.

[0067] Similarly, line segment L Ar Two detection points AP can be used r1 and AP r2 Decision. For example, processor 49 or an external processor outputs the first detection signal S. O2_nd Determine the first detection phase (e.g., the first detection point AP). r1 (vertical axis value) and based on the first delay time difference T d0 and scheduled flight time T tof (e.g. T) overall =T d0 +T tof ) Calculate the first detection distance (e.g., the first detection point AP) r1 (the horizontal axis value), so as to... Figure 8 The phase-range plane shown yields the first detection point AP. r1 The first detection phase is calculated, for example, using the formula: area B3 / (area A3 + area B3), and the first detection distance is calculated, for example, using the formula: speed of light × T. overall / 2, as it has already been explained above, will not be repeated here.

[0068] Similarly, processor 49 or an external processor outputs the second detection signal S. O2_d The second detection phase (e.g., the second detection point AP) is obtained. r2 (vertical axis value) and based on the second delay time difference T delay and scheduled flight time T tof (e.g. T) overall =T delay +T tof ) Calculate the second detection distance (e.g., the second detection point AP) r2 (the horizontal axis value), as shown in... Figure 8 The phase-distance plane shown obtains the second detection point AP. r2The second detection phase is calculated, for example, using the formula: area B4 / (area A4 + area B4), and the second detection distance is calculated, for example, using the formula: speed of light × T. overall / 2, as it has already been explained above, will not be repeated here.

[0069] Next, processor 49 or an external processor determines the first detection point AP based on the data. r1 and the second testing point AP r2 The second reference phase-distance relationship L is obtained by connecting the points in the phase-distance plane. Ar In one embodiment, the second reference phase-distance relationship L Ar Recorded in memory; in another embodiment, the processor 49 or an external processor, based on the second reference phase-distance relationship L Ar Calculate the detection compensation amount (e.g., L). Ar (intercept with phase axis) and detection correction (e.g., L) Ar The slope is corrected to the ideal slope, i.e. Figure 8 The dashed line segment, the correction amount), and the detection compensation amount and the detection correction amount are recorded in memory, but the second reference phase-distance relationship L is not recorded. Ar .

[0070] After all the above parameters have been stored or recorded in the memory of the time-of-flight sensor 300 before leaving the factory, the setting phase is complete. It is understood that although the above description determines L based on two points... Rr and L Ar However, this invention is not limited thereto. In other embodiments, multiple delay time differences T are set. delay Therefore, L can be determined by multiple reference points. Rr L is determined by multiple detection points Ar .

[0071] Please refer to the following at the same time Figures 3 to 6B and Figure 9 As shown, the method for recording temperature change parameters during the power-on phase before actual operation will be explained next. In this invention, the ambient temperature during the power-on phase is set as the operating temperature, and its actual value depends on the actual ambient temperature.

[0072] Similarly, the timing control circuit is based on Figure 5 Sequential control sampling signal S d1 With the light source driving signal S d2_nd and S d2_d With the first delay time difference T d0 and the second delay time difference T delay This corresponds to the parameters stored before leaving the factory.

[0073] At the operating temperature, when the sampling signal Sd1 With the light source driving signal S d2_nd and S d2_d With the first delay time difference T d0 At that time, the first pixel 331 generates a first operation output signal, similar to Figure 6A S shown O1_nd When the operating temperature differs from the reference temperature, the output signal waveform changes, causing the area ratio to be different. Figure 6A The area ratio is B1 / (A1+B1). When the sampling signal S d1 With the light source driving signal S d2_nd and S d2_d With a second delay time difference T delay At that time, the first pixel 331 generates a second operation output signal, similar to... Figure 6B S shown O1_d Similarly, because the output signal waveform changes due to temperature variations, the area ratio of the second operation output signal is not equal to... Figure 6B The area ratio is B2 / (A2+B2). This waveform change will cause a phase shift Δoffset and a slope shift Δslope, such as... Figure 9 As shown.

[0074] The processor 49 of the photodetector 33 then determines the operation phase-distance relationship based on the first operation output signal and the second operation output signal, for example... Figure 9 line segment L Ro It is similar to the output signal S based on the first reference signal. O1_nd and the second reference output signal S O1_d The first reference phase-distance relationship is obtained, so it will not be elaborated further here. First reference phase-distance relationship L Rr With the operation phase-distance relationship L Ro The offset between them can be considered as being caused by temperature changes. Therefore, in this invention, the processor 49 determines the phase-distance relationship L based on the first reference phase-distance relationship. Rr and the operational phase-distance relationship L Ro Calculate the temperature compensation amount Δoffset and the temperature correction amount Δslope, where the temperature correction amount is, for example, L. Ro The slope is corrected to L Rr The slope correction Δslope = slope_L Ro / slope_L Rr The temperature compensation amount Δoffset and the temperature correction amount Δslope are temporarily stored in memory (until shutdown or the next restart) to correct the current phase and current distance obtained during actual operation.

[0075] Similarly, line segment L Ro Two reference points RP can be usedO1 and RP O2 Decision. For example, processor 49 determines the first operating phase (e.g., the first reference operating point RP) based on the first operating output signal. O1 (vertical axis value) and based on the first delay time difference T d0 Find the first distance (e.g., the first reference operation point RP). O1 (the horizontal axis value), so as to... Figure 9 The phase-distance plane shown yields the first reference operating point RP. O1 Wherein, based on the first reference operating point RP O1 The first distance obtained is approximately equal to the distance calculated based on the first reference point RP. r1 The processor 49 also calculates the second operating phase (e.g., the second reference operating point RP) based on the second operating output signal. O2 (the vertical axis value) and based on the second delay time difference T delay Find the second distance (e.g., the second reference operation point RP). O2 (the horizontal axis value), so as to... Figure 9 The phase-distance plane shown yields the second reference operating point RP. O2 According to the second reference operating point RP O2 The obtained second distance is approximately equal to the distance calculated based on the second reference point RP. r2 The second distance is obtained. The method for obtaining the first operating phase and the second operating phase is similar to the method for obtaining the first reference phase and the second reference phase, so it will not be described again here.

[0076] Next, the processor 49, based on the first reference operating point RP O1 and the second reference point operation RP O2 The operational phase-distance relationship L is obtained by connecting the points in the phase-distance plane. Ro The phase-distance relationship L of this operation Ro It is then recorded in memory.

[0077] Please refer to the following at the same time Figures 3 to 5 , Figure 7A , Figure 8 and Figure 10 As shown, the temperature compensation method during actual operation will then be explained. The ambient temperature during actual operation is also the operating temperature.

[0078] When the sampling signal S d1 With light source drive S d2_nd and S d2_d With the first delay time difference T d0 At that time, the second pixel 332 generates an operation detection signal, similar to Figure 7A S shown O2_ndSimilarly, when the operating temperature differs from the reference temperature and the object distance differs from the predetermined distance D, the pulse area ratio of the operation detection signal is not equal to... Figure 7A The area ratio is B3 / (A3+B3).

[0079] Following the same method described above, processor 49 determines the current phase (e.g., current operating point AP) based on the area ratio of the operation detection signal. O (vertical axis value) and according to T overall =T tof Find the current distance (e.g., the current operation point AP). O (the horizontal axis value), thereby obtaining the current operating point AP. O At this point, the distance to the object is the value to be measured. For example... Figure 10 As shown, the current operating point AP O Phase-distance relationship with the second reference L Ar The longitudinal distance is caused by temperature changes. Therefore, the processor 49 can use the recorded temperature compensation amount Δoffset and temperature correction amount Δslope to correct the current operating point AP obtained from the operation detection signal. O The current phase can be roughly corrected to line segment L using formulas such as (current phase - Δoffset) / Δslope. Ar Above, it represents the phase after correction back to the reference temperature. Finally, the processor 49 also uses the stored detection compensation amount and the detection correction amount to correct the current operating point AP obtained from the operation detection signal. O The current distance, for example, using the formula:

[0080] Compensation distance = speed of light × detection correction × [(current phase - Δoffset) / Δslope - detection compensation] / 2

[0081] That is, the processor 49 corrects the current distance based on the stored temperature compensation, temperature correction, detection compensation, and detection correction values, which are calculated from the currently detected flight time. In other words, if the object is placed at the same predetermined distance (i.e., L calculated before leaving the factory)... Rr L Ar Given the distance D set at the time, the result can be calculated using the same method described above. Figure 10 Operation line segment L AO At this point, if the temperature compensation amount Δoffset and the temperature correction amount Δslope are used (based on...), Figure 9 (Obtained), the operation line segment L can be... AO Corrected to reference line segment L Ar This is to eliminate the offset caused by temperature changes. Next, the detection compensation and correction amounts (based on...) are used. Figure 8 If obtained, then the reference line segment L can be used.Ar Corrected to the ideal line segment.

[0082] In another implementation, the processor 49 is sampling signal S d1 With the light source driving signal S d2_nd and S d2_d With a second delay time difference T delay At that time, the current phase and current distance are calculated based on the operation detection signal generated by the second pixel 332. That is, in this invention, there is no specific limitation on the delay time used to calculate the current phase and current distance.

[0083] Please refer to Figure 11 As shown, this is a temperature compensation method for a time-of-flight sensor 300 according to an embodiment of the present invention, which includes the following steps: generating a timing signal S by a timing controller 41. syn The first delay circuit 431 and the second delay circuit 433 are sequentially set to have a first delay time difference T. d0 and the second delay time difference T delay (Step S111); at the reference temperature and the first delay time difference T d0 Below, a first reference output signal S is generated using the first pixel 331. O1_nd (Step S112); at the reference temperature and the second delay time difference T delay Next, a second reference output signal S is generated using the first pixel 331. O1_d (Step S113); Based on the first reference output signal S O1_nd and the second reference output signal S O1_d Obtain and record the first reference phase-distance relationship L. Rr (Step S114); at the operating temperature and the first delay time difference T d0 Next, a first operation output signal is generated using the first pixel 331 (step S115); at the operating temperature and the second delay time difference T delay Next, a second operation output signal is generated using the first pixel 331 (step S116); the operation phase-distance relationship L is obtained based on the first operation output signal and the second operation output signal. Ro (Step S117); Based on the first reference phase-distance relationship L Rr and the operational phase-distance relationship L Ro Calculate the temperature compensation amount Δoffset and the temperature correction amount Δslope (step S118); and correct the current phase obtained from the operation detection signal generated by the second pixel 332 at the operating temperature using the temperature compensation amount Δoffset and the temperature correction amount Δslope.

[0084] The detailed implementation methods of each step of this temperature compensation method have been described above. Steps S112-S114 are performed in the setting stage before leaving the factory; steps S115 to S118 are performed in the power-on stage before actual operation; step S111 is performed in both the setting stage and the power-on stage; and step S119 is performed in actual operation based on the current phase measured by the current flight time.

[0085] Furthermore, the above steps are mainly used to compensate for the phase shift caused by temperature changes. To eliminate the distance shift caused by other factors, the temperature compensation method of this embodiment preferably further includes the following steps: at the reference temperature and the first delay time T d0 The difference is that the second pixel 332 generates the first detection output signal S. O2_nd ; at the reference temperature and the second delay time difference T delay Next, the second detection output signal S is generated using the second pixel 332. O2_d According to the first detection output signal S O2_nd and the second detection output signal S O2_d The second reference phase-distance relationship L is obtained. Ar According to the second reference phase-distance relationship L Ar The detection compensation amount and detection correction amount are calculated and recorded; and the current distance obtained from the operation detection signal is corrected based on the detection compensation amount and the detection correction amount. Details of these steps have been illustrated above and will not be repeated here.

[0086] In this invention, it is assumed that the operating temperature will not change significantly in a short period of time; therefore, the operating phase-distance relationship L... Ro Therefore, this is determined during the startup phase. If the operating temperature changes significantly within a short period, the operating phase-distance relationship L... Ro It can calculate and record at any time according to the user's needs, as long as it is done before the actual distance measurement.

[0087] In summary, it is known that the distance to an object detected by a time-of-flight sensor will shift due to changes in ambient temperature, and known methods cannot effectively compensate for this shift in light-modulated time-of-flight sensors. Therefore, this invention provides another time-of-flight sensor that can compensate for temperature shifts (e.g., see reference). Figures 3 to 4 ) and its temperature compensation method (e.g., refer to Figure 11 It eliminates phase shift and distance error caused by changes in ambient temperature by recording temperature compensation and temperature correction values ​​in memory before actual operation.

[0088] While the present invention has been disclosed through the foregoing examples, it is not intended to limit the invention. Anyone skilled in the art to which this invention pertains can make various modifications and alterations without departing from the spirit and scope of the invention. Therefore, the scope of protection of this invention shall be determined by the appended claims.

Claims

1. A time-of-flight sensor, the time-of-flight sensor comprising: A light source, which emits light according to a light source drive signal; A photodetector, comprising: The first pixel is used to receive the sampling signal. At a reference temperature, a first reference output signal is generated when the sampling signal and the light source driving signal have a first time delay difference, and a second reference output signal is generated when the sampling signal and the light source driving signal have a second time delay difference. At the operating temperature, a first operating output signal is generated when the sampling signal and the light source driving signal have a first delay time difference, and a second operating output signal is generated when the sampling signal and the light source driving signal have a second delay time difference. The second pixel is used to receive the sampling signal. At the operating temperature, an operation detection signal is generated when the sampling signal and the light source drive have the first delay time difference; as well as Processor, the processor is used for The first reference phase-distance relationship is obtained based on the first reference output signal and the second reference output signal, and the operation phase-distance relationship is obtained based on the first operation output signal and the second operation output signal. The temperature compensation and temperature correction amounts are calculated based on the first reference phase-distance relationship and the operating phase-distance relationship. The current phase obtained from the operation detection signal is corrected using the temperature compensation amount and the temperature correction amount.

2. The time-of-flight sensor according to claim 1, wherein the first delay time difference is zero and the second delay time difference is greater than zero.

3. The time-of-flight sensor according to claim 1 further includes a timing control circuit for controlling the time delay difference between the sampling signal and the light source driving signal.

4. The time-of-flight sensor according to claim 1, further comprising: A package containing: A first accommodating space, wherein the first accommodating space accommodates the first pixel and the light source, wherein... The first pixel is used to receive reflected light from the top cover of the package; A second accommodating space, which accommodates the second pixel; and An isolation wall separates the first accommodating space and the second accommodating space so that the second pixel does not directly receive the emitted light from the light source.

5. The time-of-flight sensor according to claim 1, wherein, The second pixel is further configured to generate a first detection output signal when the sampling signal and the light source driving signal have a first delay time difference at the reference temperature, and to generate a second detection output signal when the sampling signal and the light source driving signal have a second delay time difference. The processor is further configured to obtain a second reference phase-distance relationship based on the first detection output signal and the second detection output signal, and to calculate and record the detection compensation amount and the detection correction amount based on the second reference phase-distance relationship.

6. The time-of-flight sensor of claim 5, wherein the processor is further configured to correct the current distance obtained from the operation detection signal using the detection compensation amount and the detection correction amount.

7. The time-of-flight sensor according to claim 5, wherein the first reference phase-distance relationship and the second reference phase-distance relationship are pre-recorded in memory.

8. The time-of-flight sensor according to claim 1, wherein the processor is further configured to: The first reference phase is obtained based on the first reference output signal, and the first distance is obtained based on the first delay time difference. The second reference phase is obtained based on the second reference output signal, and the second distance is obtained based on the second delay time difference. The first reference phase-distance relationship is obtained by using the first reference phase, the first distance, the second reference phase, and the second distance in the phase-distance plane.

9. A time-of-flight sensor, the time-of-flight sensor comprising: A light source, which emits light according to a light source drive signal; A photodetector, comprising a first pixel and a second pixel for generating an output signal based on a sampled signal; Memory, which is used for pre-recording: The first reference phase-distance relationship related to the first pixel at the reference temperature, and The detection compensation amount and the detection correction amount are obtained based on the second reference phase-distance relationship related to the second pixel at the reference temperature; as well as Processor, which is used at operating temperature, Calculate the operational phase-distance relationship associated with the first pixel. Calculate the temperature compensation and temperature correction amounts based on the first reference phase-distance relationship and the operating phase-distance relationship, and The current distance is corrected using the temperature compensation amount, the temperature correction amount, the detection compensation amount, and the detection correction amount.

10. The time-of-flight sensor according to claim 9, further comprising: A package containing: A first accommodating space, wherein the first accommodating space accommodates the first pixel and the light source, wherein... The first pixel is used to receive the reflected light projected by the light source onto the top cover of the package; A second accommodating space, which accommodates the second pixel; and An isolation wall separates the first accommodating space and the second accommodating space so that the second pixel does not directly receive the emitted light from the light source.

11. The time-of-flight sensor of claim 9, wherein the first reference phase-distance relationship is obtained at the reference temperature based on the following signal: When the sampling signal and the light source driving signal have a first delay time difference, the first reference output signal generated by the first pixel, and The second reference output signal generated by the first pixel when the sampling signal has a second delay time difference with the light source driving signal.

12. The time-of-flight sensor of claim 9, wherein the operating phase-distance relationship is obtained at the operating temperature based on the following signal: When the sampling signal and the light source driving signal have a first delay time difference, the first operation output signal generated by the first pixel, and The second operational output signal generated by the first pixel when the sampling signal has a second delay time difference with the light source driving signal.

13. The time-of-flight sensor of claim 9, wherein the second reference phase-distance relationship is obtained at the reference temperature based on the following signal: When the sampling signal and the light source driving signal have a first delay time difference, the second pixel generates a first detection output signal, and The second detection output signal generated by the second pixel when the sampling signal has a second delay time difference with the light source driving signal.

14. The time-of-flight sensor of claim 9, wherein the current phase is obtained at the operating temperature based on an operation detection signal generated by the second pixel.

15. A temperature compensation method for a time-of-flight sensor, the time-of-flight sensor comprising a timing controller, a first delay circuit, a second delay circuit, a first pixel, a second pixel, and a light source, wherein the first delay circuit is coupled to the light source and the second delay circuit is coupled to the first pixel and the second pixel, the temperature compensation method comprising: The timing controller generates timing signals to the first delay circuit and the second delay circuit, and sequentially sets the first delay circuit and the second delay circuit to have a first delay time difference and a second delay time difference; At the reference temperature and the first delay time difference, a first reference output signal is generated using the first pixel; At the reference temperature and the second delay time difference, a second reference output signal is generated using the first pixel; The first reference phase-distance relationship is obtained and recorded based on the first reference output signal and the second reference output signal; Under the operating temperature and the first delay time difference, the first operation output signal is generated by the first pixel; At the operating temperature and the second delay time difference, a second operating output signal is generated from the first pixel; The operation phase-distance relationship is obtained based on the first operation output signal and the second operation output signal; Calculate the temperature compensation amount and temperature correction amount based on the first reference phase-distance relationship and the operating phase-distance relationship; as well as The current phase, obtained from the operation detection signal generated by the second pixel at the operating temperature, is corrected using the temperature compensation amount and the temperature correction amount.

16. The temperature compensation method according to claim 15, wherein the first delay time difference is zero and the second delay time difference is greater than zero.

17. The temperature compensation method according to claim 15, further comprising: At the reference temperature and the first delay time difference, a first detection output signal is generated using the second pixel; At the reference temperature and the second delay time difference, a second detection output signal is generated using the second pixel; The second reference phase-distance relationship is obtained based on the first detection output signal and the second detection output signal; Calculate and record the detection compensation and detection correction amounts based on the second reference phase-distance relationship; and The current distance obtained from the operation detection signal is corrected using the detection compensation amount and the detection correction amount.

18. The temperature compensation method according to claim 17, further comprising: The first detection phase is obtained based on the first detection output signal, and the first detection distance is obtained based on the first delay time difference and the predetermined flight time, so as to obtain the first detection point in the phase-distance plane; The second detection phase is obtained based on the second detection output signal, and the second detection distance is obtained based on the second delay time difference and the predetermined flight time, so as to obtain the second detection point in the phase-distance plane; and The second reference phase-distance relationship is obtained in the phase-distance plane based on the first detection point and the second detection point.

19. The temperature compensation method according to claim 15, further comprising: The first reference phase is obtained based on the first reference output signal, and the first distance is obtained based on the first delay time difference, so as to obtain the first reference point in the phase-distance plane; The second reference phase is obtained based on the second reference output signal, and the second distance is obtained based on the second delay time difference, so as to obtain the second reference point in the phase-distance plane; and The first reference phase-distance relationship is obtained in the phase-distance plane based on the first reference point and the second reference point.

20. The temperature compensation method according to claim 15, further comprising: The first operation phase is obtained based on the first operation output signal, and the first distance is obtained based on the first delay time difference, so as to obtain the first reference operation point in the phase-distance plane; The second operation phase is obtained based on the second operation output signal, and the second distance is obtained based on the second delay time difference, so as to obtain the second reference operation point in the phase-distance plane; and The operational phase-distance relationship is obtained in the phase-distance plane based on the first reference operation point and the second reference operation point.

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