WO2021258236A1 - 飞时测距方法与装置 - Google Patents

飞时测距方法与装置 Download PDF

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Publication number
WO2021258236A1
WO2021258236A1 PCT/CN2020/097338 CN2020097338W WO2021258236A1 WO 2021258236 A1 WO2021258236 A1 WO 2021258236A1 CN 2020097338 W CN2020097338 W CN 2020097338W WO 2021258236 A1 WO2021258236 A1 WO 2021258236A1
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phase
laser light
phase shift
reflected laser
light intensity
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PCT/CN2020/097338
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English (en)
French (fr)
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李宗德
王浩任
杨孟达
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深圳市汇顶科技股份有限公司
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Priority to PCT/CN2020/097338 priority Critical patent/WO2021258236A1/zh
Publication of WO2021258236A1 publication Critical patent/WO2021258236A1/zh

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/46—Indirect determination of position data
    • G01S17/48—Active triangulation systems, i.e. using the transmission and reflection of electromagnetic waves other than radio waves

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  • This application relates to a time-of-flight ranging method system, and more particularly to a flying distance-measuring method that uses lasers of different frequencies to sense the distance to an object and a related time-of-flight ranging device.
  • 3D image sensors can generate two-dimensional (2D) images and videos. Recently, image sensors and systems that can generate three-dimensional (3D) images (or depth images) have received widespread attention. These three-dimensional image sensors can be used for face recognition and augmented reality ( Augmented reality (AR)/virtual reality (VR) can be used in mobile phones, drones, security systems, artificial intelligence systems and other equipment.
  • AR Augmented reality
  • VR virtual reality
  • the existing three-dimensional image sensor mainly has three implementation methods: stereo binocular, structured light and time of flight (ToF).
  • Time-of-flight ranging is done by using specially designed pixels to measure the flight time of photons. Its computational complexity is high, so power consumption and computational time are also long. How to solve the above problems without affecting accuracy , Has become an important work item in this field.
  • One of the objectives of the present application is to provide a time-of-flight ranging method and a time-of-flight ranging device, so as to solve the technical problem that the time-of-flight ranging method consumes time and power in the prior art.
  • An embodiment of the present application discloses a time-of-flight distance measurement method, including: irradiating a first laser to the object and generating a first reflected laser; sensing the first reflected laser, and obtaining the first laser and The first phase shift between the first reflected lasers, wherein the first phase shift is less than 2 ⁇ ; the first phase shift is added to 2 ⁇ to obtain the second phase shift; the second laser is irradiated to the object and Generate a second reflected laser; sense the second reflected laser, and obtain the first light intensity of the second reflected laser at a preset time point; calculate the difference between the second laser and the second reflected laser The third phase displacement and the fourth phase displacement, wherein the flight distance corresponding to the first phase displacement caused by the first laser is equal to the flight distance corresponding to the third phase displacement caused by the second laser, and The flying distance corresponding to the second phase shift caused by the first laser is equal to the flying distance corresponding to the fourth phase shift caused by the second laser; the second reflected laser is calculated according to the preset
  • the time-of-flight ranging device includes a time-of-flight ranging system for executing the aforementioned time-of-flight ranging method. .
  • An embodiment of the present application discloses a time-of-flight ranging method, including: irradiating a first laser to the object 4 times and generating a first reflected laser; respectively sensing in the first phase, the second phase, and the third phase And the first reflected laser of the fourth phase, and obtain the first phase shift between the first laser and the first reflected laser, wherein the first phase shift is less than 2 ⁇ ; and the first phase Displacement plus 2 ⁇ to obtain a second phase shift; irradiate a second laser to the object once and generate a second reflected laser; sense the second reflected laser, and obtain the second reflected laser at a preset time point According to the first light intensity, determine the first phase shift or the second phase shift as the phase delay between the first laser and the first reflected laser; and according to The phase delay calculates the distance.
  • the time-of-flight ranging method disclosed in the present application solves the problem of phase ambiguity of the time-of-flight distance in a novel way, thereby reducing power consumption and processing time.
  • FIG. 1 is a schematic block diagram of an embodiment of the time-of-flight ranging system of this application.
  • Figure 2 is a waveform diagram of the low-frequency laser in the sensing operation.
  • Fig. 3 is a waveform diagram of the high-frequency laser in the sensing operation.
  • FIG. 4 is a time sequence diagram of the time-of-flight ranging operation of the time-of-flight ranging system of FIG. 1.
  • Figure 5 is a flow chart of the time-of-flight ranging method.
  • FIG. 6 is a schematic diagram of an embodiment in which the time-of-flight ranging system shown in FIG. 1 is applied to an electronic device.
  • first and second features are in direct contact with each other; and may also include
  • additional components are formed between the above-mentioned first and second features, so that the first and second features may not be in direct contact.
  • present disclosure may reuse component symbols and/or labels in multiple embodiments. Such repeated use is based on the purpose of brevity and clarity, and does not in itself represent the relationship between the different embodiments and/or configurations discussed.
  • spatially relative terms here such as “below”, “below”, “below”, “above”, “above” and similar, may be used to facilitate the description of the drawing in the figure The relationship between one component/component or feature relative to another component/component or feature is shown.
  • the original meaning of these spatially-relative vocabulary covers not only the orientation shown in the figure, but also the various orientations in which the device is in use or operation.
  • the device may be placed in other orientations (for example, rotated 90 degrees or in other orientations), and these spatially-relative description vocabulary should be explained accordingly.
  • the existing three-dimensional image sensor mainly has three implementation methods: stereo binocular, structured light and time of flight (ToF).
  • the sensor emits laser to measure the time of photon flight, and then calculates the time-of-flight distance based on the speed of light, that is, the distance between the sensor and the measured object, where the time of photon flight, It is inversely inferred from the phase delay between the emitted laser light and the returning laser light.
  • the length of the distance from the object may cause the above-mentioned phase delay to exceed one wavelength (ie, 2 ⁇ ), that is, the phase aliasing caused by the phase ambiguity.
  • the senor it is necessary to use the sensor to re-emit a laser with a lower frequency to measure the flight time of the photon to help determine whether the above-mentioned phase delay exceeds one wavelength. The details are described below.
  • FIG. 1 is a schematic block diagram of an embodiment of the time-of-flight ranging system 100 of this application.
  • the time-of-flight ranging system 100 is used to sense the phase delay ⁇ +2n ⁇ (where ⁇ is less than 2 ⁇ and n is an integer) of the emitted and received laser light, and calculates the phase delay with the object 101 according to the frequency and phase delay of the laser Distance D.
  • the method of the present application can reduce the number of laser irradiations. Since a large amount of energy is required for each laser irradiation, reducing the number of laser irradiations can reduce the power consumption of the time-of-flight ranging system 100. It should be noted that although the embodiment takes the phase delay ⁇ or ⁇ +2 ⁇ as an example, the application is not limited to this, for example, ⁇ +4 ⁇ , ⁇ +6 ⁇ , ⁇ +2n ⁇ , etc. can be resolved.
  • the time-of-flight distance measurement system 100 includes a light-emitting device 120, an optical sensor 140, a processing circuit 160, and a storage device 165.
  • the light emitting device 120 is used to emit laser light LT1 and LT2 to the object 101, wherein the frequency of the laser light LT1 and the frequency of LT2 are different.
  • the optical sensor 140 is used to receive the laser light LR1, LR2 reflected from the object 101, and generate a signal according to the received laser light LR1, LR2.
  • the processing circuit 160 is coupled to the light-emitting device 120 and the optical sensor 140, and is used to control the operation of the light-emitting device 120 and the optical sensor 140, for example, controlling the turning on and off of the light-emitting device 120 and the optical sensor 140 through a clock signal.
  • the processing circuit 160 is also used to process the signal generated by the optical sensor 140.
  • the processing circuit 160 includes a microcontroller unit (MCU), a central processing unit (CPU), or a graphics processing unit (GPU).
  • phase shift ⁇ 1 can be obtained.
  • the time-of-flight ranging system 100 cannot determine that the laser light LT1 is true Whether the phase delay exceeds 2 ⁇ , that is, it is impossible to determine whether the true phase shift (phase difference) between the received laser LR1 and LT1 is ⁇ 1 or ⁇ 1 +2 ⁇ , or ⁇ 1 +4 ⁇ , so choose the smallest possible phase
  • the delay is taken as the phase shift ⁇ 1 , that is, ⁇ 1 is less than 2 ⁇ .
  • the phase shift ⁇ 2 is obtained according to the transmitting laser LT2 and the receiving laser LR2, where ⁇ 2 is less than 2 ⁇ . Since the laser LT1 and the laser LT2 have different frequencies, the phase shift ⁇ 1 and the phase shift ⁇ 2 are not the same. Assuming that f H and f L are the frequencies of the laser LT1 and laser LT2 respectively, and f H is greater than f L , the phase The displacement ⁇ 1 is greater than the phase displacement ⁇ 2 .
  • the lasers LT1, LT2, LR1, and LR2 are represented by the following signal equations 1 to 4.
  • a H , A'H , A L and A'L are amplitudes, f H and f L are frequencies, t is time, and B H , and B L are noises generated in the time-of-flight ranging system 100.
  • system noises B H and B L are also generated.
  • the system noises B H and B L become B′ H and B′ L after being reflected by the object, they are reflected back to the optical sensor 140 along with the laser light LT1 and LT2.
  • the measurement of phase shift ⁇ 1 the light emitting device 120 generates a laser LT1 irradiation target 101, and the optical sensor 140 at four different time points t1, t2 t3 and t4 sense, were measured with the phase change of the laser light LR1 Intensities Q1, Q2, Q3 and Q4.
  • the light emitting device 120 generates the laser light LT1 to illuminate the object 101 four times, and the optical sensor 140 only senses one of the light intensities Q1, Q2, Q3, and Q4 in each shot.
  • the point of time t1, t2, t3 and t4 and the light intensity Q1, Q2, Q3 and Q4 into the equation can be derived LR1 laser 2 after the amplitude A 'H, phase shift ⁇ 1 and system noise B'H .
  • the phase shift ⁇ 1 is a value smaller than 2 ⁇ .
  • the time points t1 and t3 are chosen to be half a period apart. Converted into a phase change, the phase changes by ⁇ from time t1 to t3. Correspondingly, the time points t2 and t4 are also chosen to be half a period apart. Under this condition, the laser LR1 equation 2 can be solved as follows.
  • k can be set to 0.5 ⁇ to further simplify the equation of laser LR1 as follows.
  • the actual phase delay may be ⁇ 1 or ⁇ 1 +2 ⁇
  • ⁇ 1 corresponds to the distance D1
  • ⁇ 1 +2 ⁇ corresponds to the distance D2 which is based on the phase shift ⁇ 1 and frequency f H and the speed of light c
  • the corresponding distance D1 is calculated
  • the corresponding distance D2 is calculated according to the phase shift ⁇ 1 +2 ⁇ , frequency f H and the speed of light c, but the calculation of D1 and D2 does not need to be performed in this step, but the actual phase After the delay is determined, the real distance is calculated.
  • the light emitting device 120 In order to confirm whether the actual phase delay is ⁇ 1 or ⁇ 1 +2 ⁇ , the light emitting device 120 generates laser light LT2 to irradiate the object 101 once, and recognizes whether the actual phase delay is ⁇ 1 or ⁇ 1 +2 ⁇ by reflecting the information of the laser light TR2.
  • the processing circuit 160 is used to establish a reference function and store related data in the storage device 165 in the form of a lookup table.
  • the time-of-flight ranging system 100 uses a variety of lasers with different amplitudes to emit to the object 101 and reflects a variety of lasers with different amplitudes back to the optical sensor 140.
  • the processing circuit 160 is used to write the correspondence between the incident and reflection of the various laser beams with different amplitudes into the storage device 165 to form a look-up table.
  • a set of amplitude A H and system noise B H only corresponds to a set of amplitude A'L and system noise B'L . Therefore, when the amplitude A H of the incident laser LT1 and the system noise B H are known, the processing circuit 160 can obtain the corresponding amplitude A′ L and the system noise B′ L according to the look-up table.
  • the reference function may be pre-established before the time-of-flight ranging system 100 leaves the factory. The reference function is expressed by Equation 15 as follows:
  • the optical sensor 140 senses Q5 of the laser light LR2 at time t5.
  • the processing circuit 160 inputs the amplitude A H and the system noise B H and outputs the amplitude A′ L and the system noise B′ L corresponding to the reflected laser LT2, where A H and B H are the known quantities of the system. Furthermore, when the frequency f L of the laser light LR2 is known, only the light intensity Q5, the time t, and the phase shift ⁇ 2 in the equation 4 of the laser light LR2 are unknown.
  • the processing circuit 160 is used to calculate the phase shifts ⁇ 3 and ⁇ 4 of the possible distances D1 and D2 corresponding to the laser LR2, respectively.
  • the phase shifts ⁇ 3 and ⁇ 4 can be expressed by the following equations.
  • LR2 may have a phase shift of ⁇ 3 (if the actual distance is D1) or a phase shift of ⁇ 4 (if the actual distance is D2) relative to LT2, that is, ⁇ 2 may be Is ⁇ 3 or ⁇ 4 .
  • ⁇ 3 if the actual distance is D1
  • ⁇ 4 if the actual distance is D2
  • ⁇ 2 may be Is ⁇ 3 or ⁇ 4 .
  • the light intensities Q6 and Q7 of the laser light LR2 with phase shifts ⁇ 3 and ⁇ 4 are respectively calculated.
  • the processing circuit 160 has calculated that the phase shift of the laser LR2 should be ⁇ 3 or ⁇ 4 .
  • the phase shift of the laser LR2 should be ⁇ 3 or ⁇ 4 .
  • the light intensity of the laser LR2 at the time point t5 should be Q6, that is, Q5 is equal to Q6.
  • the laser LR2 has a phase delay equal to the phase shift ⁇ 4
  • the light intensity of the laser LR2 at the time point t5 should be Q7, that is, Q5 is equal to Q7.
  • the phase delay of the laser light LR2 should be equal to ⁇ 3 or ⁇ 4 .
  • the phase delay of the laser LR2 should be equal to ⁇ 3 , and the actual distance from the object 101 is D1.
  • the phase delay of the laser LR2 should be equal to ⁇ 4 , and the actual distance from the object 101 is D2.
  • the time-of-flight ranging method enables the flying ranging system 100 to only emit lasers five times (ie, four times for high-frequency laser LT1 and one time for low-frequency laser LT2 when measuring the distance from object 101). ) To get the actual distance.
  • the time-of-flight ranging system 100 not only does it consume power to emit laser light, but it also consumes time in the receiver light and processing the signals generated by the receiver light. Therefore, the on-the-fly ranging method implemented by the on-the-fly ranging system 100 provided in the present application reduces the power consumption of the system without changing the accuracy of the measurement, and improves the long-standing problems in the field.
  • the frequency f L of the laser LR2 is smaller than the frequency f H of the laser LR1.
  • the frequency f L of the laser LR2 is less than or equal to half of the frequency f H of the laser LR1.
  • the difference between the phase shifts ⁇ 1 and ⁇ 1 +2 ⁇ is equal to 2 ⁇
  • the difference between the phase shifts ⁇ 3 and ⁇ 4 is less than ⁇ (see equations 16, 17 available).
  • the distance between the light intensity Q6 and the light intensity Q7 in the equation of the laser LR2 is less than a half period of the laser LR2.
  • the range of the half cycle can be located in an absolute decreasing or absolute increasing region. Therefore, when the light intensity Q5 is sensed, the time point t5 is selected when the light intensity Q6 and the light intensity Q7 are located in the absolute decreasing area of the laser LR2 equation 4 (as shown by the dotted square DF1 in FIG. 3). In this way, the situation where the light intensity Q6 is equal to the light intensity Q7 (as shown by the dashed box DF2 in FIG. 3) can be avoided. In other words, selecting the time point t5 in the region where the light intensity Q6 and the light intensity Q7 are located in the absolute increasing region of the laser LR2 equation can also avoid the above problem.
  • phase shift ⁇ 1 , ⁇ 1 +2 ⁇ , ⁇ 1 +4 ⁇ , or ⁇ 1 +6 ⁇ may be ⁇ 1 , ⁇ 1 +2 ⁇ , ⁇ 1 +4 ⁇ , or ⁇ 1 +6 ⁇ , according to equations 16 and 17, the phase shift ⁇ 1 , ⁇ 1 +2 ⁇ , ⁇ 1 +4 ⁇ and ⁇ 1 +6 ⁇ to calculate the phase shift between the laser LR2 and LT2 ⁇ ', ⁇ '+2 ⁇ /(f H /f L ), ⁇ '+4 ⁇ /(f H /f L ) and ⁇ '+6 ⁇ /(f H /f L ).
  • the frequency f L of the laser LT2 can be set to 1/4 times of f H , so the phase shift ⁇ ', ⁇ '+2 ⁇ /(f H /f L ), ⁇ '+4 ⁇ /( The four light intensities corresponding to f H /f L ) and ⁇ '+6 ⁇ /(f H /f L ) can fall in an absolute increase or absolute decrease area in the laser LR2. In this way, by comparing the light intensity Q5 with the corresponding four light intensities, it can be known whether the true phase delay is ⁇ 1 , ⁇ 1 +2 ⁇ , ⁇ 1 +4 ⁇ , or ⁇ 1 +6 ⁇ .
  • the optical sensor 140 also senses the background information BG.
  • the background information BG is the noise generated by the environment in which the time-of-flight ranging system 100 and the object 101 are located. Therefore, the equations of lasers LR1 and LR2 can be expressed by the following equations.
  • an additional variable BG is added.
  • the optical sensor 140 is used to separately sense the background information BG. That is, without laser irradiation, the optical sensor 140 senses the received energy, and then obtains the background information BG according to the received energy. After obtaining the background information BG, first subtract the background information BG from the sensed light intensities Q1 to Q4, and then calculate the distance D according to the above-mentioned method. Therefore, the time-of-flight ranging system 100 can obtain the distance D that is not affected by the background information BG.
  • Fig. 4 illustrates the operation sequence diagram of the time-of-flight ranging method.
  • the light emitting device 120 irradiates the laser light LT1 to the object 101 four times.
  • the optical sensor 140 senses the reflected laser light LR1 to obtain the light intensities Q1 to Q4 in sequence.
  • the light emitting device 120 irradiates the laser light LT2 to the object 101 once, and the optical sensor 140 senses the reflected laser light LR2 to obtain the light intensity Q5.
  • the optical sensor 140 senses the background information BG when there is no laser irradiation.
  • the quality of the signal generated by the optical sensor 140 is related to the laser energy. If the received laser energy is low, the signal-to-noise ratio of the signal is low. Conversely, if the received laser energy is high, the signal-to-noise ratio of the signal is high. In order to obtain a higher signal-to-noise ratio, the optical sensor 140 receives laser light for a longer period of time to increase the received laser energy. In order to achieve this effect, in some embodiments, the optical sensor 140 is used to sense the laser light LR1 in two sensing periods S1 and S2 in each of the above-mentioned irradiations. As shown in Fig.
  • the sensing period S1 is connected to the sensing period S2, and the sensing period S1 is the same length as the sensing period S2.
  • the integral amount received and sensed in the sensing period S1 is energy E1
  • the integral amount received and sensed in the sensing period S2 is energy E2.
  • the optical sensor 140 can obtain the light intensity based on the sum of the energy E1 and the energy E2.
  • the integrated amount received and sensed in the sensing period S3 is energy E3
  • the integrated amount received and sensed in the sensing period S4 is energy E4.
  • the optical sensor 140 can obtain the light intensity based on the sum of the energy E3 and the energy E4.
  • the optical sensor 140 has two switches TX1 and TX0. When the switch TX1 and the switch TX0 are turned on, the optical sensor 140 can sense laser light. In the sensing period S1, the switch TX1 is turned on and the switch TX0 is turned off, and in the sensing period S2, the switch TX0 is turned on and the switch TX1 is turned off.
  • the optical sensor 140 when the switch TX1 is turned on and the switch TX0 is turned on, the optical sensor 140 has different conversion efficiencies, where the efficiency ratio is g. That is, the optical sensor 140 can be E1+gE2 and E3+gE4 according to the energy used to generate the signal.
  • the optical sensor 140 due to the time-of-flight ranging system 100 and/or the environment, the optical sensor 140 generates a directional offset (offset) after sensing the laser time.
  • the energy E1 received in the sensing period S1 and the energy E2 received in the sensing period S2 are opposite to each other. For example, if the energy E1 and the offset are expressed as E1+offset with a positive value by the processing circuit 160, the energy E2 and the offset are expressed as -(E2-offset) with a negative value.
  • the time-of-flight distance measuring system 100 can obtain a distance that is not affected by the orientation shift when the optical sensor 140 is sensing.
  • the time-of-flight distance measurement method of the present application is shown in FIG.
  • the phase shift ⁇ 1 is added to 2 ⁇ to obtain a possible phase shift ⁇ 1 +2 ⁇ (S503).
  • the laser light LT2 is irradiated to the object 101 and the reflected laser light LR2 is generated (S504), the reflected laser light LR2 is sensed, and the light intensity Q5 of the reflected laser light at the time point t5 is obtained (S505).
  • the phase shift ⁇ 1 or the phase shift ⁇ 1 +2 ⁇ is determined as the phase delay of the laser light LR1 (S506).
  • the distance D is calculated (S507). Therefore, the distance to the object 101 obtained by the time-of-flight ranging method of the present application eliminates the disadvantage of phase aliasing.
  • FIG. 6 is a schematic diagram of an embodiment in which the time-of-flight ranging system 100 shown in FIG. 1 is applied to an electronic device 600.
  • the electronic device 600 can be any electronic device such as a smart phone, a personal digital assistant, a handheld computer system, or a tablet computer.
  • the invention calculates the phase aliasing problem of the time-of-flight distance measurement based on the measured data of the high and low frequency laser, which can reduce the number of laser irradiation and make the distance measurement more accurate.

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Abstract

一种飞时测距装置及方法，飞时测距方法用来测量与对象（101）的距离，包括：照射第一激光至对象（101）并产生第一反射激光（S501）；感测第一反射激光并得到第一与第一反射激光间的第一相位移（S502）；将第一相位移加上2π以得到第二相位移（S503）；照射第二激光至对象（101）并产生第二反射激光（S504）；感测第二反射激光并得到第二反射激光在时点上的第一光强度（S505）；计算第二与第二反射激光间的第三和第四相位移；依据时点，计算第二反射激光分别对应第三与第四相位移的第二与第三光强度；依据第一光强度决定第一或第二相位移为第一与第一反射激光间的相位延迟（S506）；及依据相位延迟计算距离（S507）。飞时测距方法在不影响准确度的前提下，降低系统耗电和运算时间。

Description

飞时测距方法与装置 技术领域
本申请涉及一种飞时测距方法系统，尤其涉及一种使用不同频率的激光来感测与对象距离的飞行测距方法以及相关飞时测距装置。
背景技术
传统的图像传感器可以生成二维(2D)图像和视频，近来可以产生三维(3D)图像(或者深度图像)的图像传感器和系统受到广泛关注，这些三维图像传感器可用于脸部识别，增强现实(augmented reality，AR)/虚拟现实(virtual reality，VR)，可以应用在手机、无人机、安防系统、人工智能系统等设备中。
现有的三维图像传感器主要有三种实现方式：立体双目，结构光和飞时测距(time of flight，ToF)。
飞时测距是通过采用特殊设计的像素来测量光子飞行的时间而完成测距，其运算复杂度高，因此耗电和运算时间也较长，如何在不影响准确度的前提下解决上述问题，已成为本领域重要的工作项目。
发明内容
本申请的目的之一在于提供一种飞时测距方法以及飞时测距装置，以解决现有技术中飞时测距方法耗时耗电的技术问题。
本申请的一实施例公开了一种飞时测距方法，包括：照射第一激光至所述对象并产生第一反射激光；感测所述第一反射激光，并得到所述第一激光与所述第一反射激光之间的第一相位移，其中所述第一相位移小于2π；将所述第一相位移加上2π以得到第二相位移；照射第二激光至所述对象并产生第二反射激光；感测所述第二反射激光，并得到所述第二反射激光在预设时点上的第一光强度；计算所述第二激光与所述第二反射激光之间的第三相位移和第四相位移，其中造成 所述第一激光产生所述第一相位移对应的飞行距离等于造成所述第二激光产生所述第三相位移对应的飞行距离，以及造成所述第一激光产生所述第二相位移对应的飞行距离等于造成所述第二激光产生所述第四相位移对应的飞行距离；依据所述预设时点，计算所述第二反射激光分别对应所述第三相位移与所述第四相位移的第二光强度与第三光强度；依据所述第一光强度，决定所述第一相位移或所述第二相位移为所述第一激光与所述第一反射激光之间的相位延迟；以及依据所述相位延迟，计算所述距离。决定所述第一相位移或所述第二相位移为所述第一激光与所述第一反射激光之间的所述相位延迟包括当所述第一光强度较接近所述第二光强度时，决定所述相位延迟等于所述第一相位移。
本申请的一实施例公开了一种飞时测距装置。所述飞时测距装置包括飞时测距系统用于执行前述的飞时测距方法。.
本申请的一实施例公开了一种飞时测距方法，包括：照射第一激光至所述对象4次并产生第一反射激光；分别感测在第一相位、第二相位、第三相位与第四相位的所述第一反射激光，并得到所述第一激光与所述第一反射激光之间的第一相位移，其中所述第一相位移小于2π；将所述第一相位移加上2π以得到第二相位移；照射第二激光至所述对象1次并产生第二反射激光；感测所述第二反射激光，并得到所述第二反射激光在预设时点上的第一光强度；依据所述第一光强度，决定所述第一相位移或所述第二相位移为所述第一激光与所述第一反射激光之间的相位延迟；以及依据所述相位延迟，计算所述距离。
本申请所公开的飞时测距方法以新颖的方式解决飞时距离的相位模糊度(phase ambiguity)的问题，进而降低功耗与处理时间。
附图说明
图1为本申请的飞时测距系统的实施例的方框示意图。
图2为在感测操作中低频激光的波形图。
图3为在感测操作中高频激光的波形图。
图4为图1的飞时测距系统的飞时测距操作时序图。
图5为飞时测距方法的流程图。
图6为图1所示的飞时测距系统应用在电子装置的实施例的示意图。
具体实施方式
以下揭示内容提供了多种实施方式或例示，其能用以实现本揭示内容的不同特征。下文所述之组件与配置的具体例子系用以简化本揭示内容。当可想见，这些叙述仅为例示，其本意并非用于限制本揭示内容。举例来说，在下文的描述中，将一第一特征形成于一第二特征上或之上，可能包括某些实施例其中所述的第一与第二特征彼此直接接触；且也可能包括某些实施例其中还有额外的组件形成于上述第一与第二特征之间，而使得第一与第二特征可能没有直接接触。此外，本揭示内容可能会在多个实施例中重复使用组件符号和/或标号。此种重复使用乃是基于简洁与清楚的目的，且其本身不代表所讨论的不同实施例和/或组态之间的关系。
再者，在此处使用空间上相对的词汇，比如「之下」、「下方」、「低于」、「之上」、「上方」及与其相似者，可能是为了方便说明图中所绘示的一组件/组件或特征相对于另一或多个组件/组件或特征之间的关系。这些空间上相对的词汇其本意除了图中所绘示的方位之外，还涵盖了装置在使用或操作中所处的多种不同方位。可能将所述设备放置于其他方位(如，旋转90度或处于其他方位)，而这些空间上相对的描述词汇就应该做相应的解释。
虽然用以界定本申请较广范围的数值范围与参数皆是约略的数值，此处已尽可能精确地呈现具体实施例中的相关数值。然而，任何数值本质上不可避免地含有因个别测试方法所致的标准偏差。在此处，「相同」通常系指实际数值在一特定数值或范围的正负10％、5％、1％或0.5％之内。或者是，「相同」一词代表实际数值落在平均值的可 接受标准误差之内，视本申请所属技术领域中具有通常知识者的考虑而定。当可理解，除了实验例之外，或除非另有明确的说明，此处所用的所有范围、数量、数值与百分比(例如用以描述材料用量、时间长短、温度、操作条件、数量比例及其他相似者)均经过「相同」的修饰。因此，除非另有相反的说明，本说明书与附随申请专利范围所揭示的数值参数皆为约略的数值，且可视需求而更动。至少应将这些数值参数理解为所指出的有效位数与套用一般进位法所得到的数值。在此处，将数值范围表示成由一端点至另一端点或介于二端点之间；除非另有说明，此处所述的数值范围皆包括端点。
现有的三维图像传感器主要有三种实现方式：立体双目，结构光和飞时测距(time of flight，ToF)。通常，在飞时测距的实现方式当中，是利用传感器发射激光来测量光子飞行的时间，再结合光速计算得到飞时距离，即传感器与被测物体之间的距离，其中光子飞行的时间，是从发射出的激光和返回的激光之间的相位延迟所反推得知。
然而，和对象(即待测物)之间的距离长度有可能会使上述相位延迟超过一个波长(即2π)，也就是因相位模糊度所造成的相位混迭。
因此，需要利用传感器再发射频率较低的激光来测量光子飞行的时间，以帮助判断上述相位延迟是否超过一个波长，其细节说明如下。
图1为本申请的飞时测距系统100的实施例的方框示意图。参照图1，飞时测距系统100用于感测发射和接收的激光的相位延迟θ+2nπ(其中θ小于2π，n为整数)，并依据激光的频率与相位延迟来计算与对象101的距离D。一般情况下，相位延迟小于2π，即n＝0，但如前所述，若发射的激光频率较高，或距离D太大时，n可能会大于0。图2至图5的实施例中叙述的飞时测距方法可分辨相位延迟为θ还是θ+2π，并据以计算出实际距离D。相较于一般作法，本申请的方法可减少激光的照射次数，由于每次照射激光都需要大量能量，因此减少激光照射次数可以降低飞时测距系统100的功耗。应注意的是，尽管实施例以分辨相位延迟θ或θ+2π为例，但本申请不以此为限，例如 可以分辨θ+4π、θ+6π、θ+2nπ等。
飞时测距系统100包括发光装置120、光学传感器140、处理电路160以及存储装置165。发光装置120用以发射激光LT1、LT2至对象101，其中激光LT1的频率和LT2的频率不同。光学传感器140用以接收从对象101反射的激光LR1、LR2，并依据接收的激光LR1、LR2产生信号。处理电路160耦接发光装置120与光学传感器140，并用以控制发光装置120与光学传感器140的操作，例如通过时钟信号控制发光装置120与光学传感器140的开启与关闭。处理电路160还用于处理光学传感器140所产生的信号。在一些实施例中，处理电路160包括微控制单元(microcontroller unit，MCU)、中央处理器(central processing unit，CPU)或图形处理器(graphics processing unit，GPU)。
由于发光装置120发射的激光LT1的相位为已知，因此当光学传感器140接收到激光LR1后，可得到相位移θ 1，但单单依据激光LT1的话，飞时测距系统100无法判断激光LT1真实的相位延迟是否超过2π，也就是无法判断接收到的激光LR1与LT1之间的真实相位移(相位差)是θ 1还是θ 1+2π,抑或是θ 1+4π，因此选择最小的可能相位延迟作为相位移θ 1，即θ 1小于2π。同样地，再依据发射激光LT2和接收激光LR2得到相位移θ 2，其中θ 2小于2π。由于激光LT1与激光LT2具有不同的频率，因此，相位移θ 1和相位移θ 2不相同，假设f H与f L分别为激光LT1与激光LT2的频率，且f H大于f L，则相位移θ 1大于相位移θ 2。为了清楚起见，激光LT1、LT2、LR1与LR2以下列信号方程式1～4表示。
LT1：A Hcos(f Ht)+B H   (方程式1)
LR1：A′ Hcos(f Ht+θ 1)+B′ H   (方程式2)
LT2：A Lcos(f Lt)+B L  (方程式3)
LR2：A′ Lcos(f Lt+θ 2)+B′ L  (方程式4)
其中A H、A' H、A L与A' L为振幅，f H与f L为频率，t为时间，以及B H、与B L为飞时测距系统100内产生的噪声，具体来说，当发光装置120产生激光LT1、LT2时，连带产生系统噪声B H与B L。当系统噪声B H与B L经对象反射后变成B' H与B' L，随着激光LT1、LT2反射回光学传感器140。
参照图2，在量测相位移θ 1时，发光装置120产生激光LT1照射对象101，且光学传感器140在四个不同时点t1、t2、t3与t4分别感测激光LR1随相位变化的光强度Q1、Q2、Q3与Q4。在一些实施例中，发光装置120产生激光LT1照射对象101四次，在每一次的照射中光学传感器140仅感测光强度Q1、Q2、Q3与Q4其中之一。因为激光LR1的频率f H已知，将时点t1、t2、t3与t4与光强度Q1、Q2、Q3与Q4带入激光LR1的方程式2后即可得出振幅A' H、相位移θ 1与系统噪声B' H。其中，相位移θ 1为小于2π的值。
为了计算方便，选择时点t1与t3相距半个周期。换算成相位变化，从时点t1到t3相位变化了π。相应的，时点t2与t4亦选择相距半个周期。在此条件下，激光LR1方程式2可解出如下。
Figure PCTCN2020097338-appb-000001
Figure PCTCN2020097338-appb-000002
Figure PCTCN2020097338-appb-000003
其中k为时点t2与t1之间的相变化，参数A1～A4可由下列方程式表示。
A1＝(Q1-B)×cosθ  (方程式8)
A2＝(Q2-B)×cos(θ+k)  (方程式9)
A3＝(Q3-B)×cos(θ+π)  (方程式10)
A4＝(Q4-B)×cos(θ+π+k)  (方程式11)
在一些实施例中，可将k设为0.5π，以进一步简化激光LR1的方程式如下。
Figure PCTCN2020097338-appb-000004
Figure PCTCN2020097338-appb-000005
Figure PCTCN2020097338-appb-000006
请回到图1，假设实际的相位延迟可能是θ 1或θ 1+2π，θ 1对应到距离D1，θ 1+2π对应到距离D2，也就是根据相位移θ 1和频率f H以及光速c计算得到对应的距离D1,根据相位移θ 1+2π和频率f H以及光速c计算得到对应的距离D2，但D1、D2的计算在本步骤中并不需要执行，而是可以待实际相位延迟确定后再进行计算真实的距离。为了确认实际的相位延迟为θ 1还是θ 1+2π，发光装置120再产生激光LT2照射对象101一次，通过反射激光TR2的信息来辨识实际的相位延迟是θ 1还是θ 1+2π。
另外，因响应对象101的反射率，入射激光LT1、LT2与反射激光LR1、LR2的振幅与噪声的相对关系由参考函数表示。在一些实施例中，处理电路160用以建立参考函数，并将相关数据以查找表(lookup table)的形式储存在存储装置165中。在一些实施例中，飞时测距系统100利用多种不同振幅的激光发射至对象101，并反射多种不同振幅的激光回到光学传感器140。处理电路160用以将所述多种不同振幅的激光入射与反射之间的对应关系写入存储装置165形成查找表。在查找表中，一组振幅A H与系统噪声B H仅对应一组振幅A' L与系统噪声B' L。因此，当入射激光LT1的振幅A H与系统噪声B H已知时，依据查找表，处理电路160可取得对应的振幅A' L与系统噪 声B' L。在一些实施例中，参考函数可以在飞时测距系统100出厂前就预先建立完毕。参考函数由方程式15表示如下:
Figure PCTCN2020097338-appb-000007
参照图3，当发光装置120照射激光LT2后，光学传感器140在时点t5感测激光LR2的Q5。
激光LR2方程式4中的振幅A' L与系统噪声B' L可由参考函数(方程式15)得到。确切来说，依据查找表，处理电路160输入振幅A H与系统噪声B H并输出反射激光LT2对应的振幅A' L与系统噪声B' L，其中A H和B H是系统已知量。再者，在激光LR2的频率f L已知的情况下，激光LR2方程式4中仅剩光强度Q5、时间t与相位移θ 2未知。接着，利用处理电路160分别计算激光LR2对应可能的距离D1与D2的相位移θ 3与θ 4。其中，相位移θ 3与θ 4可以下列方程式表示。
Figure PCTCN2020097338-appb-000008
Figure PCTCN2020097338-appb-000009
依据上述计算得到的相位移θ 3与θ 4可知LR2可能相对LT2具有θ 3的相位移(假如实际距离是D1)或者具有θ 4(假如实际距离是D2)的相位移，也就是θ 2可能是θ 3或者θ 4。在时点t5上，分别计算具有相位移θ 3与θ 4的激光LR2的光强度Q6与Q7。
在量测光强度Q5时，激光LR2的相位延迟未知。然而，处理电路160已计算激光LR2应有的相位移为θ 3或θ 4。举例来说，若激光LR2具有相位延迟等于相位移θ 3，则激光LR2在时点t5的光强度应为Q6，亦即Q5等于Q6。反之，若激光LR2具有相位延迟等于相位移θ 4，则激光LR2在时点t5的光强度应为Q7，亦即Q5等于Q7。
因此，分别比较光强度Q5与光强度Q6、Q7之间的差，可得知激光LR2具有的相位延迟应等于θ 3或θ 4。当光强度Q5较靠近光强 度Q6时(如图3上部所示)，激光LR2具有的相位延迟应等于θ 3，则与对象101的实际距离为D1。当光强度Q5较靠近光强度Q7时(如图3下部所示)，激光LR2具有的相位延迟应等于θ 4，则与对象101的实际距离为D2。
综上所述，本申请所提供的飞时测距方法可使飞测距系统100在量测与对象101的距离时，仅发射激光五次(即高频激光LT1四次，低频激光LT2一次)即可取得实际距离。对于飞时测距系统100来说，发射激光不仅耗电，且在接收机光与处理接收机光所产生的信号亦耗时。因此本申请所提供的飞测距系统100所执行的飞时测距方法在不改变量测的准确度下减少系统的功耗，改善本领域存在已久的问题。
请再回到图3，激光LR2的频率f L小于激光LR1的频率f H。在一些实施例中，激光LR2的频率f L小于或等于激光LR1的频率f H的一半。在此条件下，因为相位移θ 1与θ 1+2π之间的差等于2π，所以相位移θ 3与θ 4之间的差小于π(参照方程式16、17可得)。光强度Q6与光强度Q7在激光LR2的方程式上相距小于激光LR2的半个周期。依据激光LR2的方程式4的特性(亦即cos(t)＝Q的特性)，半个周期的范围可位于绝对递减或绝对递增的区域中。因此，在感测光强度Q5时，将时点t5选定在光强度Q6与光强度Q7位于激光LR2方程式4中绝对递减的区域(如图3虚线方块DF1所示)。如此可避免光强度Q6等于光强度Q7的情形(如图3虚线方块DF2所示)。换言之，将时点t5选定在光强度Q6与光强度Q7位于激光LR2方程式中绝对递增的区域亦可避免上述问题。
如上所述，再举一例来说明。当要分辨激光LR1与LT1之间真实的相位延迟可能为θ 1、θ 1+2π还是θ 1+4π抑或是θ 1+6π时，可依据方程式16及17，由相位移θ 1、θ 1+2π、θ 1+4π与θ 1+6π计算对应至激光LR2与LT2之间的相位移θ'、θ'+2π/(f H/f L)、θ'+4π/(f H/f L)与θ'+6π/(f H/f L)。在此情况下，激光LT2的频率f L可设定为f H的1/4倍，因此可使得相位移θ'、θ'+2π/(f H/f L)、θ'+4π/(f H/f L)与θ'+6π/(f H/f L)对应的四个光强度可以落在激光LR2中一个绝对递增或绝对递减的区域 中。如此一来，通过比较光强度Q5与对应的四个光强度可得知真实的相位延迟为θ 1、θ 1+2π还是θ 1+4π或是θ 1+6π。
在一些实施例中，光学传感器140亦感测背景信息BG。背景信息BG为飞时测距系统100与对象101所处的环境所产生的噪声。因此，激光LR1与LR2的方程式可以下列方程式表示。
LR1：A′ Hcos(f Ht+θ 1)+B′ H+BG  (方程式18)
LR2：A′ Lcos(f Lt+θ 2)+B′ L+BG   (方程式19)
依据上述方程式，当量测光强度Q1～Q5时，多了一个变数BG。当处理电路160计算距离D时，会因为背景信息BG的影响而产生误差。为了消除这个额外的变数，光学传感器140更用以单独感测背景信息BG。亦即在没有激光照射的情况下，光学传感器140感测所接收到的能量，接着依据收到的能量取得背景信息BG。取得背景信息BG之后，先将感测的光强度Q1～Q4扣除背景信息BG，再依上述的方法计算距离D。因此，飞时测距系统100可得到不受背景信息BG影响的距离D。
参照图4。图4绘示了飞时测距方法的操作时序图。发光装置120照射激光LT1至对象101四次，在每一次照射中，光学传感器140感测反射激光LR1依序得到光强度Q1～Q4。接着发光装置120照射激光LT2至对象101一次，光学传感器140感测反射激光LR2得到光强度Q5。最后，光学传感器140在没有激光照射时感测得到背景信息BG。
一般说来，光学传感器140产生的信号质量与激光能量相关。若接收的激光能量低，则信号的信噪比低。反之，若接收的激光能量高，则信号的信噪比高。为了取得较高的信噪比，光学传感器140接收较长时段的激光，以提高接收的激光能量。为了达到此效果，在一些实施例中，光学传感器140用以在上述的每一次照射中分两个感测时段S1与S2感测激光LR1。如图4所示，感测时段S1与感测时段S2相 连接，且感测时段S1与感测时段S2等长。感测时段S1内接收并感测的积分量为能量E1，感测时段S2内接收并感测的积分量为能量E2。光学传感器140可依据能量E1与能量E2的加总来得到光强度。相应地，当感测激光LR2时，感测时段S3内接收并感测的积分量为能量E3，感测时段S4内接收并感测的积分量为能量E4。光学传感器140可依据能量E3与能量E4的加总来得到光强度。
在一些实施例中，光学传感器140具有两个开关TX1与TX0。开关TX1与开关TX0开启时，光学传感器140可感测激光。在感测时段S1时，开关TX1开启以及开关TX0关闭，在感测时段S2时，开关TX0开启以及开关TX1关闭。
在一些实施例中，在开启开关TX1与开启开关TX0时，光学传感器140具有不同的转换效率，其中效率比为g。亦即，光学传感器140可依据用来产生信号的能量为E1+gE2与E3+gE4。
在一些情况下，因飞时测距系统100及/或环境使得光学传感器140在感测激光的时后产生一个定向的偏移(offset)。为了消除偏移，在一些实施例中，在感测时段S1接收的能量E1与感测时段S2所接收的能量E2互为反相。举例来说，若能量E1与偏移被处理电路160以正值表示为E1+offset，则能量E2与偏移则以负值表示为-(E2-offset)。在此情况下，当感测时段S1与感测时段S2等长时，将能量E1与能量E2的绝对值加总，存在每个时段中的偏移将会相互抵消。因此，飞时测距系统100可得到不受光学传感器140感测时的定向偏移影响的距离。
由上述说明可知，本申请的飞时测距方法如图5所示，首先照射激光LT1至对象100并产生反射激光LR1(S501)，感测反射激光LR1，并得到激光LT1与反射激光LR1之间的相位移θ 1，其中相位移θ 1小于2π(S502)。接着将相位移θ 1加上2π以得到可能的相位移θ 1+2π(S503)。再来，照射激光LT2至对象101并产生反射激光LR2(S504)，感测反射激光LR2，并得到反射激光在时点t5上的光强度Q5(S505)。 依据光强度Q5，决定相位移θ 1或相位移θ 1+2π为激光LR1的相位延迟(S506)。最后，依据相位延迟，计算距离D(S507)。因此，本申请的飞时测距方法所得到与对象101的距离消除了相位混迭的缺点。
图6为图1所示的飞时测距系统100应用在电子装置600的实施例的示意图。参照图6，电子装置600可为例如智能型手机、个人数字助理、手持式计算机系统或平板计算机等任何电子装置
本发明通过高低频激光实测数据计算出用于解决飞时测距的相位混迭问题，可以降低激光照射次数并使距离的测量更为准确。
上文的叙述简要地提出了本申请某些实施例之特征，而使得本申请所属技术领域具有通常知识者能够更全面地理解本揭示内容的多种态样。本申请所属技术领域具有通常知识者当可明了，其可轻易地利用本揭示内容作为基础，来设计或更动其他工艺与结构，以实现与此处所述之实施方式相同的目的和/或达到相同的优点。本申请所属技术领域具有通常知识者应当明白，这些均等的实施方式仍属于本揭示内容之精神与范围，且其可进行各种变更、替代与更动，而不会悖离本揭示内容之精神与范围。

Claims (21)

  1. 一种飞时测距方法，用来测量与对象的距离，其特征在于，包括：
    照射第一激光至所述对象并产生第一反射激光；
    感测所述第一反射激光，并得到所述第一激光与所述第一反射激光之间的第一相位移，其中所述第一相位移小于2π；
    将所述第一相位移加上2π以得到第二相位移；
    照射第二激光至所述对象并产生第二反射激光；
    感测所述第二反射激光，并得到所述第二反射激光在预设时点上的第一光强度；
    计算所述第二激光与所述第二反射激光之间的第三相位移和第四相位移，其中造成所述第一激光产生所述第一相位移对应的飞行距离等于造成所述第二激光产生所述第三相位移对应的飞行距离，以及造成所述第一激光产生所述第二相位移对应的飞行距离等于造成所述第二激光产生所述第四相位移对应的飞行距离；
    依据所述预设时点，计算所述第二反射激光分别对应所述第三相位移与所述第四相位移的第二光强度与第三光强度；
    依据所述第一光强度，决定所述第一相位移或所述第二相位移为所述第一激光与所述第一反射激光之间的相位延迟，其中决定所述第一相位移或所述第二相位移为所述第一激光与所述第一反射激光之间的所述相位延迟包括:
    当所述第一光强度较接近所述第二光强度时，决定所述相位延迟等于所述第一相位移；以及
    依据所述相位延迟，计算所述距离。
  2. 如权利要求1所述的飞时测距方法，其特征在于，所述第二激光的频率低于所述第一激光的频率的二分之一。
  3. 如权利要求1所述的飞时测距方法，其特征在于，所述第二反射激光对应所述第三相位移与所述第四相位移之间的光强度与相位关系为严格递增函数或严格递减函数。
  4. 如权利要求1所述的飞时测距方法，其特征在于，决定所述第一相位移或所述第二相位移为所述第一激光与所述第一反射激光之间的所述相位延迟进一步包括:
    当所述第一光强度较接近所述第三光强度时，决定所述相位延迟等于所述第二相位移。
  5. 如权利要求1所述的飞时测距方法，其特征在于，感测所述第一反射激光并得到所述第一激光与所述第一反射激光之间的所述第一相位移包括:
    以所述第一激光照射置所述对象4次；以及
    在每一次的照射中，分别感测在第一相位、第二相位、第三相位与第四相位的所述第一反射激光，其中所述第三相位与所述第一相位相差π，以及所述第四相位与所述第二相位相差π。
  6. 如权利要求5所述的飞时测距方法，其特征在于，所述第二相位与所述第一相位相差0.5π。
  7. 如权利要求1所述的飞时测距方法，其特征在于，感测所述第二反射激光在所述预设时点上的所述第一光强度包括:
    以所述第二激光并照射置所述对象1次；以及
    在所述预设时点测量所述第二反射激光的所述第一光强度。
  8. 如权利要求7所述的飞时测距方法，其特征在于，感测所述第二反射激光在所述预设时点上的所述第一光强度还包括:
    在没有产生所述第二激光时，测量背景信息，
    其中所述的飞时测距方法还包括:
    移除所述背景信息以更新所述第二光强度与所述第三光强度。
  9. 如权利要求1所述的飞时测距方法，其特征在于，感测所述第一反射激光并得到所述第一激光与所述第一反射激光之间的所述第一相位移包括:
    感测在第一感测时段内的所述第一反射激光的第一积分量；
    感测在第二感测时段内的所述第一反射激光的第二积分量；以及
    依据所述第一积分量与所述第二积分量，得到所述第一相位移，
    其中所述第一感测时段与所述第二感测时段相连，所述第一感测时段与所述第二感测时段等长，以及所述第一积分量与所述第二积分量反相。
  10. 如权利要求1所述的飞时测距方法，其特征在于，感测所述第二反射激光并得到所述第二反射激光在所述预设时点上的所述第一光强度包括:
    感测在第三感测时段内的所述第二反射激光的第三积分量；
    感测在第四感测时段内的所述第二反射激光的第四积分量；以及
    依据所述第三积分量与所述第四积分量，得到在所述预设时点上的所述第一光强度，
    其中所述第三感测时段与所述第四感测时段相连，所述第三感测时段与所述第四感测时段等长，所述预设时点在所述第三感测时段与所述第四感测时段相之间，以及所述第三积分量与所述第四积分量反相。
  11. 一种飞时测距装置，用来测量与对象间的距离，其特征在于，包括:
    飞时测距系统，用于执行如权利要求1至10中任一项所述的飞时测距方法。
  12. 一种飞时测距方法，用来测量与对象的距离，其特征在于，包括：
    照射第一激光至所述对象4次并产生第一反射激光；
    分别感测在第一相位、第二相位、第三相位与第四相位的所述第一反射激光，并得到所述第一激光与所述第一反射激光之间的第一相位移，其中所述第一相位移小于2π；
    将所述第一相位移加上2π以得到第二相位移；
    照射第二激光至所述对象1次并产生第二反射激光；
    感测所述第二反射激光，并得到所述第二反射激光在预设时点上的第一光强度；
    依据所述第一光强度，决定所述第一相位移或所述第二相位移为所述第一激光与所述第一反射激光之间的相位延迟；以及
    依据所述相位延迟，计算所述距离。
  13. 如权利要求12所述的飞时测距方法，其特征在于，所述第二激光的频率低于所述第一激光的频率的二分之一。
  14. 如权利要求12所述的飞时测距方法，其特征在于，进一步包括:
    对应所述第一相位移与所述第二相位移，分别计算所述第二激光与所述第二反射激光之间的第三相位移与第四相位移，其中造成所述第一激光产生所述第一相位移对应的飞行距离等于造成所述第二激光产生所述第三相位移对应的飞行距离，以及造成所述第一激光产生所述第二相位移对应的飞行距离等于造成所述第二激光产生所述第四相位移对应的飞行距离；以及
    依据所述预设时点，计算所述第二反射激光分别对应所述第三相位移与所述第四相位移的第二光强度与第三光强度。
  15. 如权利要求14所述的飞时测距方法，其特征在于，所述第二反射激光对应所述第三相位移与所述第四相位移之间的光强度与相位关系为严格递增函数或严格递减函数。
  16. 如权利要求14所述的飞时测距方法，其特征在于，决定所述第一相位移或所述第二相位移为所述第一激光与所述第一反射激光之间的所述相位延迟包括:
    当所述第一光强度较接近所述第二光强度时，决定所述相位延迟等于所述第一相位移；
    当所述第一光强度较接近所述第三光强度时，决定所述相位延迟等于所述第二相位移。
  17. 如权利要求12所述的飞时测距方法，其特征在于，所述第三相位与所述第一相位相差π，以及所述第四相位与所述第二相位相差π。
  18. 如权利要求17所述的飞时测距方法，其特征在于，所述第二相位与所述第一相位相差0.5π。
  19. 如权利要求12所述的飞时测距方法，其特征在于，感测所述第二反射激光在所述预设时点上的所述第一光强度进一步包括:
    在没有产生所述第二激光时，测量背景信息，
    其中所述的飞时测距方法进一步包括:
    对应所述第一相位移与所述第二相位移，分别计算所述第二激光与所述第二反射激光之间的的第三相位移与第四相位移；
    分别计算具有所述第三相位移与所述第四相位移的所述第二反射激光的第二光强度与第三光强度；以及
    移除所述背景信息以更新所述第二光强度与所述第三光强度。
  20. 如权利要求12所述的飞时测距方法，其特征在于，分别感测在所述第一相位、所述第二相位、所述第三相位与所述第四相位的所述第一反射激光并得到所述第一激光与所述第一反射激光之间的所述第一相位移包括:
    感测在第一感测时段内的所述第一反射激光的第一积分量；
    感测在第二感测时段内的所述第一反射激光的第二积分量；以及
    依据所述第一积分量与所述第二积分量，得到所述第一相位移，
    其中所述第一感测时段与所述第二感测时段相连，所述第一感测时段与所述第二感测时段等长，以及所述第一积分量与所述第二积分量反相。
  21. 如权利要求12所述的飞时测距方法，其特征在于，感测所述第二反射激光并得到所述第二反射激光在所述预设时点上的所述第一光强度包括:
    感测在第三感测时段内的所述第二反射激光的第三积分量；
    感测在第四感测时段内的所述第二反射激光的第四积分量；以及
    依据所述第三积分量与所述第四积分量，得到在所述预设时点上的所述第一光强度，
    其中所述第三感测时段与所述第四感测时段相连，所述第三感测时段与所述第四感测时段等长，所述预设时点在所述第三感测时段与所述第四感测时段相之间，以及所述第三积分量与所述第四积分量反相。
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