Distance measurement device using two optical modulation frequencies and operation method thereof

Abstract

A distance measurement device includes a light source, a light detection element, a timing control circuit and a processor. In a first measurement, the timing control circuit controls the light source to emit light at a low modulation frequency; the processor calculates the rough flight time according to the first detection signal of the light detection element and determines the operation phase interval and delay time accordingly. In a second measurement, the timing control circuit controls the light source to emit light at a high modulation frequency and makes the light source driving signal of the light source and the detection control signal of the light detection element differ by the delay time; and the processor calculates the fine flight time according to the second detection signal of the light detection element.

Description

Technical Field

[0001] The present invention relates to an optical distance measuring device, and more particularly to a time-of-flight distance measuring device and an operating method thereof that uses two light sources to modulate frequencies to increase noise immunity and detectable distance range. Background Art

[0002] At present, optical distance measurement devices generally use imaging technology based on CCD image sensors or CMOS image sensors. The method of calculating the distance of an object by estimating the time difference between the light beam emitted by a light source and the light sensor after it is reflected by the object is called time-of-flight (TOF) detection technology.

[0003] Indirect time-of-flight detection technology (iTOF) modulates the light source drive signal and uses the time difference between the light source drive signal and the detection signal as the flight time. Figure 1 As shown, there is a time difference Tf between the light source emitting light (corresponding to the light source driving signal) and the reflected light being detected. The larger the time difference Tf is, the larger the measured distance is. The maximum value of the time difference Tf does not exceed the exposure period. Therefore, if you want to obtain a larger detectable distance range, you can choose to configure a longer exposure period.

[0004] However, a long exposure period means that the modulation frequency of the light source is slower and has a lower signal-to-noise ratio (SNR). If you want to improve the SNR, you need to increase the modulation frequency of the light source, which in turn shortens the detectable distance. Therefore, in actual configuration, you need to make a trade-off between the SNR and the detectable distance range.

[0005] Therefore, an indirect time-of-flight distance measurement device having both a large detectable distance range and a high signal-to-noise ratio is needed. Summary of the invention

[0006] The present invention provides a distance measurement device which uses two optical modulation frequencies to perform two-stage measurement, so as to increase the detectable distance range and the anti-noise capability.

[0007] The present invention provides a distance measuring device including a light source, a light detection element and a processor. The light source is used to illuminate the object with a first modulation frequency and a second modulation frequency in sequence according to a light source driving signal, wherein the second modulation frequency is higher than the first modulation frequency. The light detection element is used to detect the reflected light from the object to generate a first detection signal when the light source emits light at the first modulation frequency according to a detection control signal, and to detect the reflected light from the object to generate a second detection signal when the light source emits light at the second modulation frequency. The processor is used to calculate the operating phase interval in which the first phase is located according to the first detection signal and determine the delay time accordingly, make the light source driving signal and the detection control signal differ by the delay time when the light source emits light at the second modulation frequency, and calculate the second phase according to the second detection signal and calculate the object distance accordingly.

[0008] The present invention also provides a distance measurement device including a light source, a light detection element, a timing control circuit and a processor. The light source is used to emit light to illuminate the object. The light detection element is used to detect the reflected light of the object to generate a detection signal. The timing control circuit is used to control the light source to emit light at a first modulation frequency during a first measurement and to control the light source to emit light at a second modulation frequency during a second measurement, wherein the second modulation frequency is higher than the first modulation frequency. The processor is used to calculate a coarse phase according to the detection signal generated by the light detection element during the first measurement and to calculate a fine phase according to the detection signal generated by the light detection element during the second measurement, wherein the processor outputs the object distance corresponding to the fine phase but does not output the object distance corresponding to the coarse phase.

[0009] The present invention also provides an operating method of a distance measuring device, the distance measuring device comprising a light source, a light detection element and a processor. The operating method comprises the following steps: using a light source driving signal to control the light source to emit light at a first modulation frequency and using a detection control signal to control the light detection element to detect reflected light from an object to generate a first detection signal; using the processor to calculate the operating phase interval in which the first phase is located according to the first detection signal and determine the delay time accordingly; using the light source driving signal to control the light source to emit light at a second modulation frequency higher than the first modulation frequency and using the detection control signal to control the light detection element to detect reflected light from the object to generate a second detection signal, wherein the light source driving signal and the detection control signal differ by the delay time; and using the processor to calculate the second phase according to the second detection signal.

[0010] In the distance measuring device of the embodiment of the present invention, the light detecting element is, for example, a photodiode. The first accumulator and the second accumulator include a charge storage, such as a capacitor, for storing light energy detected by the photodiode in different periods.

[0011] In the distance measuring device of the embodiment of the present invention, the light detection element is, for example, an avalanche diode. The first accumulator and the second accumulator include a counter, such as a continuous wave counter, for counting the electrical pulses generated by the avalanche diode in different periods. The count value is positively correlated with the light energy detected by the avalanche diode.

[0012] In order to make the above and other purposes, features and advantages of the present invention more obvious, the following will be described in detail with reference to the accompanying drawings. In addition, in the description of the present invention, the same components are represented by the same symbols, which are hereby described together. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic diagram of a known time-of-flight detection technique;

[0014] Figure 2 is a block diagram of a distance measurement device according to an embodiment of the present invention;

[0015] Figure 3 is a schematic diagram of the operation of the distance measurement device according to an embodiment of the present invention;

[0016] Figure 4 is another block diagram of a distance measurement device according to an embodiment of the present invention;

[0017] Figure 5 is a schematic diagram of a detection phase of a distance measurement device according to an embodiment of the present invention;

[0018] Figure 6 is another operation schematic diagram of the distance measuring device according to an embodiment of the present invention; and

[0019] Figure 7 is a flow chart of an operating method of a distance measuring device according to an embodiment of the present invention.

[0020] Description of Reference Numerals

[0021] 200 Distance measuring device

[0022] 21 Light Source

[0023] 22 Light detection element

[0024] 23 Detection switch

[0025] 24 Timing Control Circuit

[0026] 251 First accumulator

[0027] 252 Second accumulator

[0028] 27 Memory

[0029] 29 Processor

[0030] O Object DETAILED DESCRIPTION

[0031] The present invention relates to a time-of-flight distance measurement device using two-stage measurement. Based on the fact that a higher light modulation frequency can obtain a higher signal-to-noise ratio and a lower light modulation frequency can obtain a larger detectable distance range, the distance measurement device of the embodiment of the present invention sequentially uses two different light modulation frequencies to obtain the advantages of both at the same time and obtain better noise immunity.

[0032] Please refer to Figure 2 , which is a block diagram of a distance measuring device 200 according to an embodiment of the present invention. The distance measuring device 200 includes a light source 21, a light detection element 22, a detection switch 23, a timing control circuit 24, a first accumulator 251, a second accumulator 252, a memory 27, and a processor 29 that are coupled to each other. In one embodiment, these components are configured in the same detection chip. In another embodiment, the light detection element 22, the detection switch (e.g., a transistor switch) 23, the first accumulator 251, and the second accumulator 252 form a light sensor, which is used to output the first accumulated energy and the second accumulated energy accumulated during different periods.

[0033] In one embodiment, the light source 21 is a laser diode (LD), such as a vertical cavity surface emitting laser (VCSEL). In another embodiment, the light source 21 is a light emitting diode (LED). The light source 21 emits light in a recognizable spectrum (such as red light and / or infrared light) to illuminate the object O; wherein the object O is any object within the detectable distance range of the distance measuring device 200, as long as it can reflect the light emitted by the light source 21, and there is no specific limitation. In some applications, the larger the detectable distance range, the better. The distance measuring device 200 of the embodiment of the present invention can measure the distance of the object O or establish its depth map. For example, the distance measuring device 200 may include a plurality of light detection elements arranged in an array.

[0034] The light detection element 22 is a photodiode or an avalanche diode, such as a single photon avalanche diode (SPAD), wherein the operation principle of the photodiode and the avalanche diode is known and thus will not be described in detail herein. The light detection element 22 is used to detect the reflected light of the object O to generate a detection signal So.

[0035] The timing control circuit 24 controls the light source 21 to emit light using the light source driving signal S1. Figure 3, which is a schematic diagram of the operation of the distance measuring device 200 according to an embodiment of the present invention. The light source driving signal S1 is a time-varying signal, which is used to alternately light up the light source 21 during the first period T1 of the exposure period and turn off the light source 21 during the second period T2 of the exposure period. It can be understood that when the modulation frequency of the light source driving signal S1 is smaller, the first period T1 and the second period T2 are longer. The timing control circuit 24 also controls the light detection element 22 to detect the reflected light from the object O with the detection control signal S2. In the present invention, the light source driving signal S1 and the detection control signal S2 can be adjusted to have two different oscillation frequencies.

[0036] The detection switch 23 is, for example, a switch component or a multiplexer (MUX). The detection switch 23 conducts the light detection element 22 and the first accumulator 251 during the first period T1, so that the first accumulator 251 can accumulate the first light energy E1 of the reflected light detected by the light detection element 22, for example, using the first synchronization signal S syn The detection switch 13 also conducts the light detection element 22 and the second accumulator 252 during the second period T2, so that the accumulator 252 can accumulate the second light energy E2 of the reflected light detected by the light detection element 22, for example, using the second synchronization signal S syn_inv Controls the operation of the second accumulator 252. The first synchronization signal S syn For example, the second synchronization signal S is in phase with the light source driving signal S1. syn_inv For example, the first synchronization signal S1 is inversely proportional to the light source driving signal S2. syn After the inverter, the second synchronization signal S syn_inv In the present invention, since the reflected light is detected during both the first period T1 and the second period T2, the exposure period = T1 + T2.

[0037] In the present invention, the types of the first accumulator 251 and the second accumulator 252 are configured corresponding to the light detection element 22. When the light detection element 22 is a photodiode, the first accumulator 251 and the second accumulator 252 are, for example, capacitors for accumulating charges to reflect the detection energies E1 and E2 of the reflected light. When the light detection element 22 is an avalanche diode, the first accumulator 251 and the second accumulator 252 are asynchronous counters, such as ripple counters, for counting photon events of the avalanche diode to reflect the detection energies E1 and E2 of the reflected light.

[0038] like Figure 2 and Figure 3As shown, a time interval Tf passes from when the light source 21 emits light until the light detection element 22 receives the reflected light, wherein when there is no time difference between the light source driving signal S1 and the detection control signal S2, the time interval Tf is equal to the flight time; when there is a time difference between the light source driving signal S1 and the detection control signal S2, the time interval Tf is equal to the sum of the flight time and the time difference, wherein the time difference is described later, for example, as a delay time.

[0039] Please refer to Figure 4 , which is another block diagram of the distance measurement device 200 according to an embodiment of the present invention. The timing control circuit 24 includes a timing controller 240, a first delay circuit 241 and a second delay circuit 242. The timing controller 240 is used to provide a synchronization signal S syn The synchronization signal S syn After passing through the first delay circuit 241, the light source driving signal S1 is used as the light source driving signal S1. The light source driving signal S1 is driven by the light source driver 210 (for example, a voltage or current is generated corresponding to the light source driving signal S1) to turn on and off the light source 21. syn After passing through the second delay circuit 242, the detection control signal S2 is used as the detection control signal S2, which controls the light detection of the light detection element 22 through the detection controller 220, for example, turning on and off the transistor switch corresponding to the detection control signal S2. The first delay circuit 241 is used to control the phase delay of the light source driving signal S1. The second delay circuit 242 is used to control the phase delay of the detection control signal S2.

[0040] Figure 4 In the figure, the detection switch 23, the first accumulator 251 and the second accumulator 252 are omitted.

[0041] The processor 29 is, for example, a digital signal processor (DSP) or an application specific integrated circuit (ASIC), and is used to calculate the detection phase (such as the first phase and the second phase described below) according to the first light energy E1 and the second light energy E2. In one embodiment, the processor 29 uses the formula: detection phase = E2 / (E1+E2) to calculate, which corresponds to Figure 3 The time interval Tf is shown.

[0042] Please refer to Figure 5 , which is a schematic diagram showing the detection phase calculated by the processor 29. When there is no phase delay between the light source driving signal S1 and the detection control signal S2, Figure 2 and Figure 3 It can be seen that during the first exposure period when the object O gradually moves away from the distance 0 (i.e., Tf gradually increases from 0), the value of E2 / (E1+E2) gradually increases until the phase of the reflected light is aligned with the second period T2 of the first exposure period, and the value of E2 / (E1+E2) is the maximum, for example, when the phase of the reflected light is aligned with the second period T2 of the first exposure period. Figure 5 point P1; when the object O is further away, the phase of the reflected light enters Figure 3 During the second exposure period, the value of E2 / (E1+E2) gradually decreases until the phase of the reflected light is aligned with the first period T1 of the second exposure period, and the value of E2 / (E1+E2) is the minimum, for example, reaching Figure 5 At point P2, the phase curve will be as follows Figure 5 Changes repeatedly.

[0043] Since the light source 21 generally has temperature dependence, different modulation parameters will be generated at different operating temperatures, so that the phase curve has nonlinear regions, such as regions close to the maximum value (such as P1) and the minimum value (such as P2). Figure 5 It can be seen that a value of E2 / (E1+E2) can correspond to multiple phases. The present invention only uses the first linear region (the linear region is represented by a filled dot region, for example) to calculate the object distance to avoid miscalculation of the object distance due to misjudgment of the current phase. The object distance can be calculated using the calculated current phase, for example, object distance = (E2 / (E1+E2))×(c / 2)×P, where c is the speed of light and P is the light source modulation period. Figure 5 It is also shown that when the detection control signal S2 delays the light source driving signal S1 by half the light source modulation period T D The phase curve (lower row) at this time, Figure 3 The time interval Tf = T D +E2 / (E1+E2). That is, the time difference between the detection control signal S2 and the light source driving signal S1 changes the length of the time interval Tf, thereby changing the calculated object distance.

[0044] As mentioned above, since the present invention only utilizes Figure 5 The first linear region of the phase curve is used to calculate the object distance, so the range of the first linear region determines the detectable distance range, and the range of the first linear region is affected by the light modulation frequency. In the present invention, two measurements are used to determine the object distance.

[0045] Please also refer to Figures 2 to 6 , and then the operation of the distance measuring device 200 of the present invention is described. Figure 6 In order to simplify the diagram, only the first linear region corresponding to the light source modulation frequency F1 without phase delay and the light source modulation frequency F2 with different delay times (or delayed phases) is shown, wherein, Figure 6 Del = -0.5 to 3.5 represents the ratio of the delay time to the exposure period (or light source modulation period). Figure 6 The first linear regions corresponding to different delay times of the light source modulation frequency F2 are arranged in two rows and represented by regions filled with dots.

[0046] The timing control circuit 24 controls the light source 21 to emit light to illuminate the object O with the light source driving signal S1 having the first modulation frequency F1 during the first measurement, and controls the light source 21 to emit light to illuminate the object O with the light source driving signal S1 having the second modulation frequency F2 during the second measurement, wherein the second modulation frequency F2 is higher than the first modulation frequency F1, for example Figure 6 It is shown that F2 = 4×F1. Therefore, the linear region of the phase curve of the first measurement is four times the linear region of the phase curve of the second measurement. That is, the detectable distance range of the first measurement is four times the detectable distance range of the second measurement.

[0047] In the first measurement, the timing control circuit 24 controls the light detection element 22 to detect the reflected light from the object O with the detection control signal S2 having the frequency F1 to generate the first detection signal So1, wherein the first detection signal So1 is accumulated by the first accumulator 251 and the second accumulator 252 to form the first light energy E1 and the second light energy E2 (for example, refer to Figure 3 ), and at this time, there is preferably no delay time between the light source driving signal S1 and the detection control signal S2.

[0048] Similarly, during the second measurement, the timing control circuit 24 controls the light detection element 22 to detect the reflected light from the object O with the detection control signal S2 having a frequency F2 to generate a second detection signal So2, wherein the second detection signal So2 accumulates light energy through the first accumulator 251 and the second accumulator 252 to form the first light energy E1' and the second light energy E2'.

[0049] The processor 29 calculates the first phase according to the first detection signal So1, for example, E2 / (E1+E2) indicates that the phase is located at Figure 6 A, wherein, since the low frequency F1 is used in the first measurement and has a lower signal-to-noise ratio, the first phase is referred to as a coarse phase in the present invention. At the same time, the processor 29 uses the first phase to determine the operating phase interval (e.g. Figure 6 Point A is shown to be located in the fourth phase interval Z4) to determine the delay time (or delay phase), for example Figure 6 The display delay is 1.5 F2 modulation cycles. In the present invention, the processor 29 does not use the first phase to calculate the object distance (ie, does not calculate (c / 2)×P F1 ×E2 / (E1+E2), where P F1 It is the modulation period of F1, and the object distance corresponding to the first phase is not output.

[0050] In the present invention, a plurality of preset operation phase intervals (eg, Figure 6 Displays 8 phase intervals Z0 to Z8) and multiple delay times (e.g. Figure 6 The relative relationship of the delay phase from Del = -0.5 to 3.5 is shown. For example, when the detection control signal S2 lags behind the light source driving signal S1, the delay time is set to a positive value (for example Figure 6 However, when the light source driving signal S1 lags behind the detection control signal S2, the delay time is set to a negative value (eg Figure 6 When there is no phase difference between S1 and S2, Del=0.

[0051] When the processor 29 calculates the first phase, it is able to obtain the delay time by accessing the memory 27, and notify the timing control circuit 24 to delay one of the detection control signal S2 and the light source driving signal S1 relative to the operating phase interval where the first phase is located during the second measurement, that is, to control one of the first delay circuit 241 and the second delay circuit 242.

[0052] During the second measurement, the timing control circuit 24 controls the light source driving signal S1 and the detection control signal S2 to differ by the delay time. The processor 29 calculates the second phase according to the second detection signal So2 generated by the light detection element 22, for example, E2' / (E1'+E2') is displayed at Figure 6 The second phase is called fine phase in the present invention because the second measurement uses a high modulation frequency F2 and has a higher signal-to-noise ratio. The processor 29 calculates and outputs the object distance according to the second phase, for example, object distance = (c / 2) × P F2 ×(T D +E2' / (E1'+E2')), where P F2 is the modulation period of F2, T D is the delay time obtained by the first measurement. In other words, the processor 29 delays the phase T D The sum of the fine phase E2' / (E1'+E2') is taken as the flight time.

[0053] Thus, although the second measurement has a smaller detectable distance range, the delay time T is confirmed by using the first measurement. D , which can effectively extend the overall detectable distance range of the second measurement. Figure 6 As shown, when the first phase is located after the fifth phase interval Z5, the delay time T D will be greater than the period of the second modulation frequency F2.

[0054] Please refer to Figure 7, which is a flow chart of the operating method of the distance measurement device 200 according to an embodiment of the present invention, comprising the following steps: measuring a coarse phase at a low frequency (step S71); identifying an operating phase interval and selecting a delay time according to the coarse phase (step S73); measuring a fine phase at a high frequency (step S75); and calculating a distance according to the fine phase and the operating phase interval (step S77).

[0055] Please also refer to Figures 2 to 7 , and then explain this operating mode.

[0056] Step S71: During the first measurement, the timing control circuit 24 controls the light source 21 to emit light at the first modulation frequency F1 with the light source driving signal S1, and controls the light detection element 22 to detect the reflected light from the object O to generate the first detection signal So1 with the detection control signal S2 (also a time-varying signal with the frequency F1). As described above, the first accumulator 251 and the second accumulator 252 accumulate the light energy detected by the light detection element 22 to generate the first light energy E1 and the second light energy E2 respectively.

[0057] Step S73: Next, the processor 29 calculates the operating phase interval where the first phase E2 / (E1+E2) is located according to the first detection signal So1, for example Figure 6 The fourth phase interval Z4 is shown. The processor 29 determines the delay time (eg, Del=1.5) according to the first phase, for example, by accessing the memory 27 .

[0058] Step S75: During the second measurement, the processor 29 notifies the timing control circuit 24 to make the light source driving signal S1 and the detection control signal S2 have the delay time (for example, the processor 29 sends a control signal to the first delay circuit 241 or the second delay circuit 242), wherein the timing control circuit 24 can delay one of the light source driving signal S1 and the detection control signal S2 corresponding to the obtained operation phase interval. The timing control circuit 24 controls the light source 21 to emit light at a second modulation frequency F2 higher than the first modulation frequency F1 with the light source driving signal S1, and controls the light detection element 22 to detect the reflected light from the object O with the detection control signal S2 (also a time-varying signal with the frequency F2) to generate the second detection signal So2. Similarly, the first accumulator 251 and the second accumulator 252 accumulate the light energy detected by the light detection element 22 to generate the first light energy E1' and the second light energy E2' respectively.

[0059] Step S77: Finally, the processor 29 calculates the second phase E2' / (E1'+E2') according to the second detection signal So2, and calculates and outputs the current object distance accordingly, for example, object distance = (c / 2) × P F2 ×(T D +E2' / (E1'+E2')).

[0060] One of the advantages of the present invention is that even in the first measurement, the first phase is shifted to the point B of the fifth phase zone Z5 (such as Figure 6 However, in the second measurement, since the linear region of the delayed phase Del=2 (i.e., Z5) partially overlaps with the linear region of the delayed phase Del=1.5 (i.e., Z4), the same phase A' will be obtained regardless of whether Z4 or Z5 is used to calculate the fine phase. In other words, the number of phase intervals divided by the linear region corresponding to the first modulation frequency F1 can be set according to the circuit parameters of the distance measurement device 200, and is not limited to Figure 6 Preferably, the configuration of the delay time can make adjacent linear regions corresponding to high modulation frequencies partially overlap each other, which can improve the anti-noise capability.

[0061] In the present invention, since the signal-to-noise ratio of the first measurement is lower, the phase A is not necessarily equal to the phase A′ due to the offset caused by the noise.

[0062] It must be pointed out that although Figure 4 The display timing control circuit 24 includes two delay circuits, but the present invention is not limited thereto. In implementations where only one of the light source driving signal S1 and the detection control signal S2 needs to be delayed (for example, depending on the position of the detected object), the timing control circuit 24 may include only a single delay circuit.

[0063] It is understood that the values ​​in the above embodiments, such as the ratio of high and low driving frequencies, the delay time or phase, and the number of phase intervals, are only illustrative and are not intended to limit the present invention. In other embodiments, if a longer detectable distance range is to be obtained, multiple light source driving frequencies can be measured twice or more (for example, the driving frequencies are increased sequentially), which can also achieve the same effect.

[0064] In summary, in the conventional indirect time-of-flight detection technology, a trade-off needs to be made between the signal-to-noise ratio and the detectable distance range. Whether increasing or decreasing the light source modulation frequency, there will be a negative impact. Therefore, the present invention also provides a distance measurement device ( Figure 2 and Figure 4 ) and its operation method ( Figure 6 to Figure 7 ), which can perform two measurements by changing the light source modulation frequency, thereby having the advantages of a large detectable distance range and a high signal-to-noise ratio, and having a high noise immunity.

[0065] Although the present invention has been disclosed through the above examples, they are not intended to limit the present invention. Any person skilled in the art with ordinary knowledge in the art to which the present invention belongs can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the appended claims.

Claims

1. A distance measuring device, the distance measuring device is used to measure the distance of an object, the distance measuring device comprising: a light source, the light source being used to illuminate the object in sequence with a first modulation frequency and a second modulation frequency according to a light source driving signal, wherein the second modulation frequency is higher than the first modulation frequency; a light detection element, the light detection element being used to detect reflected light from the object when the light source emits light at the first modulation frequency to generate a first detection signal, and to detect reflected light from the object when the light source emits light at the second modulation frequency to generate a second detection signal according to a detection control signal; a first accumulator, the first accumulator being used to accumulate first light energy of the first detection signal and the second detection signal during a first period; a second accumulator, the second accumulator being used to accumulate second light energy of the first detection signal and the second detection signal during a second period; as well as A processor that is used to: Calculate the operating phase interval where the first phase is located according to the first detection signal and determine the delay time accordingly, When the light source emits light at the second modulation frequency, the light source driving signal and the detection control signal differ by the delay time, and Calculate the second phase according to the second detection signal and calculate the object distance accordingly, The processor is used to calculate the first phase and the second phase according to the first light energy and the second light energy. 2 . The distance measuring device according to claim 1 , wherein the light detecting element is a photodiode or an avalanche diode.

3. The distance measuring device according to claim 1, further comprising a memory, wherein the memory is used to pre-record the relative relationship between a plurality of preset operation phase intervals and a plurality of delay times.

4. The distance measuring device according to claim 3 further comprises a timing control circuit coupled to the light source, the light detection element and the processor, wherein the timing control circuit is used to delay one of the detection control signal and the light source driving signal according to the delay time determined by the operating phase interval in which the first phase is located. The distance measurement device as claimed in claim 1 , wherein the delay time is greater than a period of the second modulation frequency. 6 . The distance measurement device according to claim 1 , wherein the processor uses a sum of the second phase and the delay time as a flight time.

7. A distance measuring device, the distance measuring device is used to measure the distance of an object, the distance measuring device comprising: a light source for emitting light to illuminate the object; a light detection element, the light detection element being used to detect reflected light of the object to generate a detection signal; A timing control circuit, the timing control circuit is used to control the light source to emit light at a first modulation frequency during a first measurement and to control the light source to emit light at a second modulation frequency during a second measurement, wherein the second modulation frequency is higher than the first modulation frequency; A first accumulator, the first accumulator being used to accumulate a first light energy of the detection signal during a first period; a second accumulator, the second accumulator being used to accumulate a second light energy of the detection signal during a second period; as well as a processor, the processor being used to calculate a coarse phase according to the detection signal generated by the light detection element during the first measurement, and to calculate a fine phase according to the detection signal generated by the light detection element during the second measurement, wherein the processor outputs an object distance corresponding to the fine phase but does not output an object distance corresponding to the coarse phase, The processor is used to calculate the coarse phase and the fine phase according to the first light energy and the second light energy. 8 . The distance measuring device according to claim 7 , wherein the light detecting element is a photodiode or an avalanche diode.

9. The distance measurement device according to claim 7, wherein the timing control circuit comprises: A first delay circuit, the first delay circuit being used to delay the phase of a light source driving signal of the light source; and a second delay circuit, the second delay circuit being used to delay the phase of the detection control signal of the light detection element, in, The processor is further configured to determine a delayed phase between the light source driving signal and the detection control signal during the second measurement according to the rough phase. 10 . The distance measurement device according to claim 9 , further comprising a memory for pre-recording a relative relationship between the coarse phase and the delayed phase. 11 . The distance measurement device according to claim 9 , wherein the processor is further configured to use a sum of the delay phase and the fine phase as a flight time. 12 . The distance measuring device according to claim 9 , wherein the delay phase between the light source driving signal and the detection control signal is 0 during the first measurement.

13. An operating method of a distance measuring device, the distance measuring device comprising a light source, a light detection element and a processor, the operating method comprising: Controlling the light source to emit light at a first modulation frequency using a light source driving signal and controlling the light detection element to detect reflected light from an object using a detection control signal to generate a first detection signal; Using the processor to calculate the operating phase interval in which the first phase is located according to the first detection signal and determine the delay time accordingly; Controlling the light source to emit light at a second modulation frequency higher than the first modulation frequency by the light source driving signal and controlling the light detection element to detect the reflected light from the object by the detection control signal to generate a second detection signal, wherein the light source driving signal differs from the detection control signal by the delay time; as well as calculating a second phase according to the second detection signal by the processor, The processor calculates the first phase and the second phase according to a first accumulator accumulating first light energy of the first detection signal and the second detection signal during a first period and according to a second accumulator accumulating second light energy of the first detection signal and the second detection signal during a second period. 14 . The operating method according to claim 13 , wherein when the light source emits light at the second modulation frequency, the detection control signal lags behind the light source driving signal by the delay time. 15 . The operating method according to claim 13 , wherein when the light source emits light at the second modulation frequency, the light source driving signal lags behind the detection control signal by the delay time.

16. The operating method according to claim 13, further comprising: The processor uses the sum of the second phase and the delay time as the flight time. 17 . The operating method according to claim 13 , wherein when the light source emits light at the first modulation frequency, the delay time between the light source driving signal and the detection control signal is 0.

18. The operating method according to claim 13, further comprising: The processor calculates a distance to an object using the second phase but not using the first phase to calculate the distance to the object.

Images