JP2024013232A - Range-finding device and range-finding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a range-finding device and the like that are robust against noise more than conventional arts.

SOLUTION: A range-finding device 100 is the range-finding device that measures a distance to an object according to a TOF (Time Of Flight) method, and comprises: a light source unit 40; a light reception element that receives reflection light in which light the light source unit 40 emits is reflected upon an object 200; and a light reception unit 60 that has a first tap, second tap and third tap to which an electric charge generated by the light reception element receiving the reflection light is distributed; and a signal generation unit 20 that generates a control signal for a light emitting timing of the light source unit 40, and an exposure timing corresponding to the first tap, second tap and third tap by adding modulation using a pseudo random number to a basic signal.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a distance measuring device and a distance measuring method.

2. Description of the Related Art Conventionally, as a distance measuring device for measuring the distance to an object, a TOF (Time of Flight) type distance measuring device that uses the flight time of light is known. Patent Document 1 discloses a distance measuring device in which a spread spectrum signal is applied to a modulation reference frequency of an optical pulse.

Special Publication No. 2014-522979

However, in a distance measuring device, it is desired that the measured distance be less affected by disturbance noise. In other words, a distance measuring device that is more robust against noise is desired.

Therefore, the present invention provides a distance measuring device and a distance measuring method that are more robust against noise than conventional ones.

A distance measuring device according to one embodiment of the present invention is a distance measuring device that measures a distance to a target object using a TOF (Time Of Flight) method, and includes a light source section and light emitted from the light source section that measures a distance to a target object using a TOF (Time Of Flight) method. a light-receiving element that receives the reflected light reflected by the light-receiving element, and a light-receiving section having a first tap, a second tap, and a third tap to which charges generated when the light-receiving element receives the reflected light are distributed; A signal that generates a control signal for the light emission timing of the light source unit and the exposure timing corresponding to the first tap, the second tap, and the third tap by modulating the basic signal using pseudorandom numbers. and a generating section.

A distance measuring method according to one embodiment of the present invention is a distance measuring method executed by a distance measuring device that measures the distance to an object using a TOF (Time Of Flight) method, and the distance measuring device includes a light source section. and a light-receiving element that receives reflected light from which the light emitted by the light source is reflected by the object; a first tap to which charges generated when the light-receiving element receives the reflected light are distributed; a light receiving section having two taps and a third tap; A control signal for controlling the distribution of charges to each is generated by modulating the basic signal using pseudo-random numbers.

According to one embodiment of the present invention, it is possible to realize a distance measuring device or the like that is more robust against noise than conventional ones.

FIG. 1 is a block diagram showing the functional configuration of a distance measuring device according to the first embodiment. FIG. 2 is a diagram illustrating a part of the circuit configuration of a pixel in the light receiving section according to the first embodiment. FIG. 3 is a diagram showing an example of various signals. FIG. 4 is a diagram illustrating an example of a light emission control signal and an exposure control signal according to the first embodiment. FIG. 5 is a diagram illustrating an example of a detection signal and distance calculation method according to the first embodiment. FIG. 6 is a flowchart showing the operation of the distance measuring device according to the first embodiment. FIG. 7A is a first diagram showing a comparison of distance measurement results. FIG. 7B is a second diagram showing a comparison of distance measurement results. FIG. 8 is a diagram showing measurement results of a distance measuring device of a comparative example. FIG. 9 is a diagram showing measurement results of the distance measuring device according to the first embodiment. FIG. 10 is a diagram illustrating an example of a light emission control signal and an exposure control signal according to a modification of the first embodiment. FIG. 11 is a flowchart showing the operation of the distance measuring device according to a modification of the first embodiment. FIG. 12 is a diagram showing measurement results of the distance measuring device according to a modification of the first embodiment. FIG. 13 is a diagram showing a part of the circuit configuration of a pixel of a light receiving section according to the second embodiment. FIG. 14 is a diagram illustrating an example of a light emission control signal and an exposure control signal according to the second embodiment. FIG. 15 is a diagram illustrating an example of a detection signal and distance calculation method according to the second embodiment. FIG. 16 is a flowchart showing the operation of the distance measuring device according to the second embodiment. FIG. 17A is a diagram showing measurement results of a distance measuring device of a comparative example. FIG. 17B is a first diagram showing measurement results of the distance measuring device according to the second embodiment. FIG. 18 is a second diagram showing measurement results of the distance measuring device according to the second embodiment. FIG. 19 is a diagram illustrating an example of a light emission control signal and an exposure control signal according to Operation Example 1. FIG. 20A is a diagram showing a graph obtained by simulation using the timing chart of FIG. 19. FIG. 20B is a diagram showing a graph obtained by actually measuring using the timing chart of FIG. 19. FIG. 21 is a diagram illustrating an example of a light emission control signal and an exposure control signal according to Operation Example 2. FIG. 22A is a diagram showing a graph obtained by simulation using the timing chart of FIG. 21. FIG. 22B is a diagram showing a graph obtained by actually measuring using the timing chart of FIG. 21. FIG. 23 is a diagram illustrating an example of a light emission control signal and an exposure control signal according to operation example 3. FIG. 24 is a diagram showing a graph obtained using the timing chart of FIG. 23. FIG. 25 is a diagram showing how the first distance measurement was additionally performed. FIG. 26A is a diagram showing distance measurement results using the conventional method. FIG. 26B is a diagram showing distance measurement results using a method using pseudo-random number modulation. FIG. 27A is a diagram showing distance measurement results when a control signal obtained by adding pseudo-random number modulation to the basic signal shown in FIG. 3(b) is used. FIG. 27B is a diagram showing a distance measurement result when a control signal obtained by adding pseudo-random number modulation to the basic signal shown in FIG. 3(f) is used. FIG. 28 is a diagram showing comparison results of distance measurement based on differences in basic signals. FIG. 29A is a diagram for explaining a coding curve when using the basic signal shown in FIG. 3(b). FIG. 29B is a diagram for explaining a coding curve when using the basic signal shown in FIG. 3(f). FIG. 30 is a diagram showing how the second distance measurement was additionally performed. FIG. 31A is a diagram showing distance measurement results using the conventional method. FIG. 31B is a diagram showing distance measurement results using a method using pseudo-random number modulation. FIG. 32A is a diagram showing evaluation results of distance estimation accuracy when the basic signal shown in FIG. 3(d) is used in a noise-free environment. FIG. 32B is a diagram showing evaluation results of distance estimation accuracy when using the basic signal shown in FIG. 3(b) in a noise-free environment. FIG. 32C is a diagram showing evaluation results of distance estimation accuracy when the basic signal shown in FIG. 3(f) is used in a noise-free environment. FIG. 32D is a diagram showing evaluation results of distance estimation accuracy when DSSS modulation is applied to the basic signal in a noise-free environment. FIG. 32E is a diagram showing evaluation results of distance estimation accuracy when pseudo-random number modulation is applied to the basic signal shown in FIG. 3(d) in a noise-free environment. FIG. 32F is a diagram showing evaluation results of distance estimation accuracy when pseudo-random number modulation is applied to the basic signal shown in FIG. 3(b) in a noise-free environment. FIG. 32G is a diagram showing evaluation results of distance estimation accuracy when pseudo-random number modulation is applied to the basic signal shown in FIG. 3(f) in a noise-free environment. FIG. 33A is a diagram showing evaluation results of distance estimation accuracy when the basic signal shown in FIG. 3(d) is used in a noisy environment. FIG. 33B is a diagram showing evaluation results of distance estimation accuracy when using the basic signal shown in FIG. 3(b) in a noisy environment. FIG. 33C is a diagram showing evaluation results of distance estimation accuracy when the basic signal shown in FIG. 3(f) is used in a noisy environment. FIG. 33D is a diagram showing evaluation results of distance estimation accuracy when DSSS modulation is added to the basic signal in a noisy environment. FIG. 33E is a diagram showing evaluation results of distance estimation accuracy when pseudo-random number modulation is applied to the basic signal shown in FIG. 3(d) in a noisy environment. FIG. 33F is a diagram showing evaluation results of distance estimation accuracy when pseudo-random number modulation is applied to the basic signal shown in FIG. 3(b) in a noisy environment. FIG. 33G is a diagram showing evaluation results of distance estimation accuracy when pseudo-random number modulation is applied to the basic signal shown in FIG. 3(f) in a noisy environment. FIG. 34 is a diagram showing comparison results of distance estimation accuracy.

A distance measuring device according to one aspect of the present invention is a distance measuring device that measures a distance to a target object using a TOF (Time Of Flight) method, and includes a light source section and light emitted from the light source section that measures a distance to a target object. a light-receiving element that receives reflected light reflected by the light-receiving element, and a first tap, a second tap, and a third tap to which charges generated when the light-receiving element receives the reflected light are distributed; A signal that generates a control signal for the light emission timing of the light source unit and the exposure timing corresponding to the first tap, the second tap, and the third tap by modulating the basic signal using pseudorandom numbers. and a generating section.

Thereby, since the distance measuring device randomly modulates the basic signal using pseudo-random numbers, it is possible to suppress the influence of low-frequency and high-frequency disturbance light. Furthermore, since the light receiving section has three taps, the influence of constant disturbance light (environmental light) such as sunlight can also be suppressed. Therefore, according to the present invention, it is possible to suppress the effects of low-frequency and high-frequency disturbance light as well as steady disturbance light, so it is possible to realize a distance measuring device that is more robust against noise than the conventional one.

Furthermore, for example, the modulation using the pseudorandom numbers may be modulation using a Galois field.

As a result, the first tap, second tap, and third tap are controlled using a control signal generated by modulation using a Galois field, so that the first tap, second tap, and third tap have a steady state. Charges generated when disturbance light is received can also be accumulated. That is, the first tap, the second tap, and the third tap accumulate electric charges corresponding to the received amount of reflected light and steady disturbance light. In this case, the influence of steady ambient light can be removed by the output signal (detection signal) output from each of the first tap, second tap, and third tap, so the distance measuring device can eliminate the influence of steady ambient light. can be suppressed. Therefore, according to the present invention, it is possible to realize a distance measuring device that is more robust against noise than the conventional one.

Further, for example, in the modulation using the Galois field, a pseudorandom number in the Galois field having the same number of orders as the number of taps included in the light receiving section may be used as the Galois field.

As a result, since the number of taps and the order of the Galois field are the same, if the tap can take on three states: on, off, and transition state, in each of the first tap, second tap, and third tap, The probability of occurrence of on, off and transition states can be made equal. In other words, the amount of light received in the on, off, and transition states can equally contribute to the distance measurement result. Therefore, even when measuring distance with equal probability of occurrence of on, off, and transition states, it is possible to realize a distance measuring device that is more robust against noise than the conventional one.

Further, for example, in the modulation using the Galois field, a pseudorandom number in the Galois field having an order larger than the number of taps included in the light receiving section may be used as the Galois field.

Accordingly, by using a Galois field whose order is larger than the number of taps, the degree of freedom in controlling the first tap, second tap, and third tap increases, for example. This can lead to realizing a distance measuring device that is more robust to noise than conventional ones.

Further, for example, each of the first tap, the second tap, and the third tap may be in a first state in which it is on for one period, a second state in which it is off for one period, and a state in which it is on and off within one period. and a third state that switches from one off state to the other state, and the signal generation unit, based on the pseudo-random number, at one tap of the first tap, the second tap, and the third tap, The control signal for the one tap may be generated so that the probability of appearance of one of the first state, the second state, and the third state is different from that of the other taps.

As a result, when a tap can take on three states: on, off, and a transition state, in at least one of the first tap, second tap, and third tap, the probability of occurrence of the on, off, and transition state is reduced compared to the other taps. It can be made different. For example, the amount of light received in a state to be prioritized among on, off, and transition states can be made to contribute more to the distance measurement result. Therefore, even when measuring distances with different probabilities of occurrence of on, off, and transition states, it is possible to realize a distance measuring device that is more robust against noise than conventional ones.

Further, for example, the signal generation unit modulates the basic signal with a first pseudo-random number using a first pseudo-random number, and modulates the basic signal with a second pseudo-random number different from the first pseudo-random number. The control signal for the light emission timing is generated by multiplexing the added second signal in the time direction, and a first light reception signal based on the first signal and a first light reception signal based on the second signal are generated. The control signal for the exposure timing may be generated by multiplexing the second light reception signal in the time direction.

Thereby, the measurable distance range of the distance measuring device can be expanded, and the accuracy of the distance can be improved.

Further, for example, another distance measuring device is arranged in the space where the distance measuring device is arranged, and the distance measuring device is used to emit the disturbance light based on the disturbance light received by the light receiving section. The distance measuring device may include a signal processing unit that specifies a pseudorandom number and identifies the other distance measuring device from the specified pseudorandom number.

Thereby, it is possible to identify other distance measuring devices using the distance measuring device. Furthermore, when a distance measuring device and another distance measuring device emit light from their light sources using pseudo-random numbers, the light is uncorrelated with each other. Less susceptible to light emitted by the range finder (disturbance light). Therefore, even in an environment where other distance measuring devices emit disturbance light, it is possible to realize a distance measuring device that is robust against noise.

Further, for example, a calculation unit may be provided that calculates the distance based on a ratio using the amount of charge accumulated in each of the first tap, the second tap, and the third tap.

Thereby, the signal processing section can calculate the distance based on a ratio using the amount of charge accumulated in each tap, specifically, a ratio using a detection signal corresponding to the amount of charge. That is, the signal processing section can directly calculate the distance using the detection signal from the light receiving section. Therefore, the distance measuring device can calculate the distance without being affected by noise generated during AD conversion, for example, compared to the case where the distance is calculated by A/D (Analog/Digital) conversion.

Further, for example, the basic signal may be a single frequency signal.

Thereby, the distance measuring device can calculate the distance without changing the frequency of the basic signal and performing measurements multiple times. Therefore, the distance measuring device can calculate distance at higher speed.

Further, for example, the basic signal of the control signal for the light emission timing is a pulse-like signal, and the basic signal of the control signal for the exposure timing is the first tap, the second tap, and the third tap. It may also be a trapezoidal signal whose phase differs depending on the tap.

This makes it possible to lengthen the coding curve visualized in three-dimensional space by connecting the input values of the control signals to each tap corresponding to the distance, so it is possible to realize a distance measuring device that is more robust against noise.

Further, for example, the root mean square error of the distance measured in an environment where high frequency noise is present may be 100 mm or less.

As a result, since the root mean square error is 100 mm, accurate distance measurement can be performed.

A distance measuring device according to one aspect of the present invention is a distance measuring device that measures a distance to a target object using a TOF (Time Of Flight) method, and includes a light source section and light emitted from the light source section that measures a distance to a target object. a light receiving element that receives the reflected light reflected by the light receiving element; a light receiving part having a first tap and a second tap to which charges generated when the light receiving element receives the reflected light are distributed; and a light emitting part of the light source part. and a signal generation unit that generates a control signal for timing and exposure timing corresponding to the first tap and the second tap by modulating the basic signal using pseudorandom numbers.

Thereby, since the distance measuring device randomly modulates the basic signal using pseudo-random numbers, it is possible to suppress the influence of low-frequency and high-frequency disturbance light. Therefore, according to the present invention, it is possible to realize a distance measuring device that is more robust against noise than the conventional one.

A distance measuring method according to one aspect of the present invention is a distance measuring method executed by a distance measuring device that measures the distance to an object using a TOF (Time Of Flight) method, and the distance measuring device includes a light source unit. a light-receiving element that receives light emitted by the light source and reflected by the object; a first tap and a second tap to which charges generated when the light-receiving element receives the reflected light are distributed; a light receiving section having a tap and a third tap; A control signal for controlling the distribution of charges to each is generated by modulating the basic signal using pseudo-random numbers.

This produces the same effect as the distance measuring device described above.

Note that these general or specific aspects may be realized in a system, a method, an integrated circuit, a computer program, or a non-transitory recording medium such as a computer-readable CD-ROM. It may be realized by any combination of a circuit, a computer program, or a recording medium. The program may be stored in advance on a recording medium, or may be supplied to the recording medium via a wide area communication network including the Internet.

Hereinafter, embodiments and the like will be specifically described with reference to the drawings.

Note that the embodiments described below are all inclusive or specific examples. Numerical values, shapes, constituent elements, arrangement positions and connection forms of constituent elements, steps, order of steps, etc. shown in the following embodiments are merely examples, and do not limit the present invention. Further, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims will be described as arbitrary constituent elements.

Furthermore, each figure is a schematic diagram and is not necessarily strictly illustrated. Therefore, for example, the scale etc. of each figure do not necessarily match. Further, in each figure, substantially the same configurations are denoted by the same reference numerals, and overlapping explanations will be omitted or simplified.

In addition, in this specification, terms indicating relationships between elements such as orthogonal and the same, terms indicating shapes such as sine wave shape and rectangular shape, numerical values, and numerical ranges have only strict meanings. This is not an expressive expression, but an expression that means that it includes a substantially equivalent range, for example, a difference of about several percent (for example, about 10%).

In addition, in this specification, ordinal numbers such as "first" and "second" do not mean the number or order of components, unless otherwise specified, and should be used to avoid confusion and distinguish between similar components. It is used for the purpose of

(Embodiment 1)
The distance measuring device according to this embodiment will be described below with reference to FIGS. 1 to 9. In this embodiment, an example in which random encoding is applied to a 2-tap (or 3-tap) distance measuring device will be described.

[1-1. Configuration of distance measuring device]
FIG. 1 is a block diagram showing the functional configuration of distance measuring device 100 according to the present embodiment.

As shown in FIG. 1, the distance measuring device 100 measures the distance to the target object 200 by emitting light toward the target object 200 and receiving the reflected light that is reflected by the target object 200. The distance measuring device 100 is a device that measures the distance to an object 200 using a TOF (Time of Flight) method. The distance measuring device 100 is also called a TOF camera. The distance measuring device 100 is used for shape measurement in AR (Augmented Reality)/MR (Mixed Reality) including entertainment, a distance measuring device mounted on an autonomous vehicle, a biometric authentication device, and the like. Further, the distance measuring device 100 may also be used as a device for performing shape measurement in real time. Note that the distance is the distance from the distance measuring device 100 to the target object 200.

The distance measuring device 100 includes a control section 10, a signal generation section 20, a light source control section 30, a light source section 40, a light reception control section 50, a light reception section 60, and a signal processing section 70.

The control unit 10 is a control device that controls each component of the distance measuring device 100. The control unit 10 controls the light source unit 40 and the light receiving unit 60 based on, for example, a control signal from an object on which the distance measuring device 100 is mounted, a user's operation on an operation unit (not shown), etc. The signal generation unit 20 is caused to generate a signal. Note that the operation unit is, for example, a button, a touch panel, or the like.

The signal generating section 20 generates control signals for controlling the light emission timing of the light source section 40, the exposure timing of the light receiving section 60, and the like. The signal generating section 20 generates random control signals for each of the light source section 40 and the light receiving section 60.

The signal generation unit 20 generates a control signal by modulating the basic signal using a pseudorandom number (bit string). The basic signal is a signal that can realize distance measurement to the target object 200, and for example, a signal with a single frequency is used. In this embodiment, a signal called "double ramp" (see (d) in FIG. 3) is used as the basic signal. Furthermore, in this embodiment, DSSS (Direct Sequence Spread Spectrum) modulation is used as the modulation using pseudo-random numbers. That is, DSSS is used to generate pseudo-random numbers. DSSS is also referred to as PN (Pseudo Random Noise) spreading, and can use an M-sequence code as the pseudo random noise.

Note that the M sequence is a random number in which binary values of 0 and 1 are randomly arranged, and is generated by feeding back using a shift register of a predetermined length and an exclusive OR. Pseudo-random numbers are also called modulation signals (modulation codes).

The control signal generated by the signal generation unit 20 is a spread spectrum signal in which "1" and "0" bits are arranged almost randomly. Since the control signal has randomness, it is possible to suppress the influence of low-frequency and high-frequency disturbance light on distance measurement. In other words, it is possible to realize the distance measuring device 100 that is robust against low-frequency and high-frequency disturbance light.

Note that the method for generating pseudorandom numbers is not limited to the above, and any known method may be used. Further, hereinafter, a control signal for controlling the light source section 40 will also be referred to as a light emission control signal, and a control signal for controlling the light receiving section 60 will also be referred to as an exposure control signal.

The light source control section 30 causes the light source section 40 to emit light according to control from the signal generation section 20 . The light source control section 30 controls the light emission by the light source section 40 by controlling the timing of supplying power to each light emitting element of the light source section 40 based on the light emission control signal from the signal generation section 20 .

The light source section 40 emits light under control from the light source control section 30. The light source section 40 may have, for example, an LED (Light Emitting Diode) element as a light emitting element, a laser element, or another light emitting element. Further, the wavelength of the light emitted by the light source section 40 is not particularly limited as long as it is a wavelength that allows the measurement of a desired distance.

The light reception control section 50 causes the light reception section 60 to receive the reflected light under control from the signal generation section 20 . The light reception control section 50 controls light reception (exposure) by the light reception section 60 by controlling the timing of supplying power to the light reception section 60 based on the exposure control signal from the signal generation section 20 . For example, the light reception control section 50 applies a gate signal (voltage) to the gate electrodes of the transfer transistors 63a and 63b (see FIG. 2) of the light reception section 60 for turning the gate electrodes on and off based on the exposure control signal. Output. The light reception control section 50 outputs a gate signal to the gate electrodes of the transfer transistors 63a and 63b so as to turn off the other transfer transistor 63a and 63b while turning on one of the transfer transistors 63a and 63b.

The light receiving section 60 outputs a detection signal according to the amount of received light by receiving the reflected light from the light source section 40 reflected by the target object 200. The light receiving section 60 includes a light receiving element such as a photodiode 62 (see FIG. 2). The light receiving section 60 is, for example, a CMOS (complementary metal-oxide-semiconductor) sensor in which light receiving elements are arranged in a two-dimensional manner. Note that the detection signal is a signal that indicates one voltage value depending on the amount of accumulated charge.

FIG. 2 is a diagram showing a part of the circuit configuration of the pixel 61 of the light receiving section 60 according to the present embodiment. In FIG. 2, of the circuit configuration of the pixel 61, only the components required from receiving reflected light to accumulating charges are illustrated.

As shown in FIG. 2, the pixel 61 of the light receiving section 60 has a photodiode 62, a first tap 61a, and a second tap 61b as a circuit configuration. The pixel 61 is configured such that the charge generated in one photodiode 62 is distributed to either the first tap 61a or the second tap 61b. A detection signal corresponding to the amount of charge accumulated in the first tap 61a and a detection signal corresponding to the amount of charge accumulated in the second tap 61b are separately output to the signal processing section 70. Note that the above-mentioned distribution means to distribute the charges so that the charges accumulated for each tap can be read out. Further, separately outputting means, for example, outputting at different timings or using different signal lines.

The first tap 61a includes a transfer transistor 63a and an FD (Floating Diffusion) section 64a, and outputs a detection signal according to the amount of charge accumulated in the FD section 64a.

The second tap 61b includes a transfer transistor 63b and an FD section 64b, and outputs a detection signal according to the amount of charge accumulated in the FD section 64b.

The conductivity types of transfer transistors 63a and 63b may be the same or different. For example, if one of the transfer transistors 63a and 63b has an n-type conductivity type, and the other transfer transistor 63a and 63b has a p-type conductivity type, a common gate signal is used to connect the transfer transistors 63a and 63b. Can be controlled on and off. Note that the conductivity type is not limited to n-type and p-type.

Note that the pixel 61 may further include a third tap (not shown, but for example, the third tap 61c shown in FIG. 13) connected to the photodiode 62. The third tap is, for example, a tap for accumulating charges caused by constant environmental light (global light) such as sunlight and illumination light. In this case, the signal generation unit 20 further generates a gate signal for controlling the third tap. The gate signal is a gate signal that turns on the third tap at a timing when the reflected light emitted from the light source section 40 and reflected by the target object 200 is not received, for example, at a timing before the light source section 40 emits light. Note that the control signal that controls the third tap is, for example, a signal that is not randomly encoded using pseudorandom numbers.

Referring again to FIG. 1, the signal processing section 70 functions as a calculation section that calculates the distance from the distance measuring device 100 to the target object 200 based on the detection signal supplied from the light receiving section 60. The signal processing unit 70 calculates a ratio using the detection signal from the first tap 61a and the detection signal from the second tap 61b, and calculates the distance based on the calculated ratio.

The signal processing unit 70 sets the amount of charge indicated by the detection signal from the first tap 61a as Q2, the amount of charge indicated by the detection signal from the second tap 61b as Q3, and the amount of charge indicated by the detection signal from the third tap as Q1. , when the light emission period is T0, the flight time ΔT of the reflected light is calculated using the following (Formula 1).

(Q3-Q1)/((Q2-Q1)+(Q3-Q1))=ΔT/T0...(Formula 1)

Note that the light emission period T0 is, for example, a cumulative period of light emission periods of each of a plurality of light emissions in a predetermined period (for example, one frame period), but is not limited thereto. Further, in this specification, flight time ΔT is also referred to as delay time.

Although the signal processing section 70 directly calculates the distance from the signal strength of the detection signal (analog signal) output from the light receiving section 60, the distance may be calculated by digital signal processing, for example.

Here, various signals in the distance measuring device 100 will be explained with reference to FIGS. 3 to 5. First, basic signals and the like will be explained with reference to FIG. FIG. 3 is a diagram showing an example of various signals. FIG. 3 shows the basic signals of the light emission control signal and the exposure control signal, and the relationship between the distance and signal strength for each basic signal. The output signal is a detection signal that the light receiving section 60 outputs to the signal processing section 70. In the graphs shown in FIGS. 3(a) and 3(b), the horizontal axis represents time, the vertical axis represents signal strength, and the horizontal axis represents depth (distance) in the graph shown in FIG. 3(c). , and the vertical axis shows the signal strength. The vertical axis is a value with the maximum value of signal strength being 1. Further, the depth is synonymous with the round trip time (flight time ΔT) of light.

Further, FIG. 3 shows basic signals in the case of the 3-tap method. The solid lines (M1(t), D1(t) and F1(t)) indicate the signals for the first tap 61a, and the broken lines (M2(t), D2(t) and F2(t)) indicate the signals for the second tap 61a. 61b, and the dash-dotted lines (M3(t), D3(t), and F3(t)) indicate the signal for the third tap. For example, the solid line M1(t) is a basic signal for causing the light source unit 40 to emit light for accumulating charges in the first tap 61a, and the broken line M2(t) is the basic signal of the solid line M1(t). shows a basic signal for accumulating charges generated by reflected light emitted from the light source unit 40 by the target object 200 in the first tap 61a.

In FIG. 3, when signals overlap, the solid line is given priority. Furthermore, although six types of basic signals (a) to (f) are illustrated in FIG. 3, the present invention is not limited to these six types, and signals of other shapes may be used.

FIG. 3(a) shows a case where the basic signal of the light emission control signal is a sinusoidal signal with three taps and the same phase, and the basic signal of the exposure control signal is a sinusoidal signal with three taps and different phases. ing. In this case, for each of the three taps, the output signal is set to any value on the sinusoidal waveform depending on the distance to the object 200 (the sine wave shown in "output signal for distance" in (a) of FIG. 3). This is a signal that indicates any value on a wavy waveform.

FIG. 3(b) shows a case where the basic signal of the light emission control signal is a rectangular waveform signal with 3 taps and the same phase, and the basic signal of the exposure control signal is a rectangular waveform signal with 3 taps and different phases. ing. In this case, the output signal becomes a signal indicating any value on the triangular waveform depending on the distance to the target object 200 in each of the three taps.

FIG. 3(c) shows that the basic signal of the light emission control signal is a ramp-type signal that changes from 1 to 0 at the timing of half the predetermined period (2τ) at the first tap 61a, and the intensity at the second tap 61b. is a signal with an intensity of 0.5, the intensity is a signal with an intensity of 0 at the third tap, and the basic signal of the exposure control signal transitions from 1 to 0 at the timing of half the predetermined period (2τ) at the first tap 61a. The signal is a ramp type signal, and the intensity is 1 at the second tap 61b and the third tap. In this case, the output signal is a signal indicating any value on a straight line downward to the right at the first tap 61a, and a signal whose intensity is 1 at the second tap 61b, depending on the distance to the target object 200. The third tap provides a signal indicating 0 when there is no disturbance light.

(d) of FIG. 3 is a ramp type signal in which the basic signal of the light emission control signal changes from 1 to 0 at the timing of half the predetermined period (2τ) at the first tap 61a and the second tap 61b; At 3 taps, the intensity is 0, and the basic signal of the exposure control signal is a ramp type signal that transitions from 1 to 0 at half the timing of a predetermined period (2τ) at the first tap 61a, and at the second tap 61b is a ramp type signal that transitions from 0 to 1 at a timing half of a predetermined period (2τ), and the third tap shows a case where the signal has an intensity of 1. In this case, the output signal is a signal indicating any value on a straight line downward to the right at the first tap 61a, and any value on a straight line upward to the right at the second tap 61b, depending on the distance to the target object 200. If there is no disturbance light at the third tap, the signal becomes 0.

(e) in FIG. 3 shows a case where the basic signal of the light emission control signal is a pulse-like signal with 3 taps and the same phase, and the basic signal of the exposure control signal is a sine wave-like signal with 3 taps and different phases. ing. In this case, the output signal becomes a signal indicating any value on a sinusoidal waveform depending on the distance to the target object 200 in each of the three taps.

(f) in FIG. 3 shows a case where the basic signal of the light emission control signal is a pulse-like signal with 3 taps and the same phase, and the basic signal of the exposure control signal is a trapezoidal wave-like signal with 3 taps and different phases. ing. In this case, the output signal becomes a signal indicating any value on the trapezoidal waveform depending on the distance to the target object 200 in each of the three taps.

Next, the light emission control signal and the exposure control signal will be explained with reference to FIG. 4. FIG. 4 is a diagram showing an example of a light emission control signal and an exposure control signal according to this embodiment. The horizontal axis shows time, and the vertical axis shows signal strength.

FIG. 4A shows an exposure control signal for the first tap 61a, specifically a gate signal supplied to the gate electrode of the transfer transistor 63a. It can also be said that (a) in FIG. 4 shows the timing and period during which the photodiode 62 is exposed and the first tap 61a accumulates charge. In other words, the signal generation unit 20 uses pseudo-random numbers to change the exposure period and exposure period of the photodiode 62, as well as the storage period and storage period of the charge to the first tap 61a. The exposure period and exposure cycle are also referred to as exposure mode.

FIG. 4B shows an exposure control signal for the second tap 61b, specifically a gate signal supplied to the gate electrode of the transfer transistor 63b. It can also be said that (b) in FIG. 4 shows the timing and period during which the photodiode 62 is exposed and the second tap 61b accumulates charge. In other words, the signal generation unit 20 uses pseudo-random numbers to change the exposure period and exposure period of the photodiode 62, as well as the storage period and storage period of the charge to the second tap 61b.

FIG. 4C shows a light emission control signal for controlling the light source section 40, and specifically shows a signal supplied to the light emitting element of the light source section 40. It can also be said that (c) of FIG. 4 shows the timing and light emission period when the light source section 40 emits light. In other words, the signal generation section 20 changes the light emission period and light emission period of the light source section 40 using pseudo-random numbers. The light emission period and the light emission period are also referred to as the light emission mode.

The signals shown in (a) to (c) of FIG. 4 are signals based on modulation using pseudo-random numbers, respectively. A signal modulated using pseudo-random numbers becomes a signal including multiple frequencies. Including a plurality of frequencies means including a plurality of light emission periods and a plurality of light emission cycles within a predetermined period (for example, within one frame). Note that in FIG. 4, three arbitrary locations corresponding to (a) to (c) in FIG. 4 are indicated by broken lines.

As shown in FIGS. 4A and 4C, the exposure control signal that controls the first tap 61a and the light emission control signal that controls the light source section 40 are the same signal. That is, the on/off of the first tap 61a and the on/off of the light source section 40 are synchronized, and the first tap 61a is turned on when the light source section 40 emits light, and turned off when the light source section 40 is turned off. The signal generation section 20 controls the first tap 61a using the same signal as the light emission control signal that controls the light source section 40.

As shown in FIGS. 4B and 4C, the exposure control signal that controls the second tap 61b and the light emission control signal that controls the light source section 40 are signals in which ON and OFF are inverted. That is, the second tap 61b is turned off when the light source section 40 emits light, and turned on when the light source section 40 is turned off. The signal generation section 20 controls the second tap 61b using an exposure control signal that is an inverted state of on/off from the light emission control signal that controls the light source section 40.

By controlling the light source section 40 and the light receiving section 60 with such a control signal, the charge generated by the reflected light from the object 200 located near the distance measuring device 100 is mainly accumulated in the first tap 61a. The charges generated by the reflected light from the object 200 located far from the distance measuring device 100 are mainly accumulated in the second tap 61b.

Next, a method for calculating the detection signal and distance will be described with reference to FIG. 5. FIG. 5 is a diagram illustrating an example of a detection signal and distance calculation method according to the present embodiment. The dashed-dotted line frame shown in FIG. 5 indicates the distance range to be measured by the distance measuring device 100.

(a) of FIG. 5 is a diagram showing the relationship between the distance to the object 200 and the signal strength of the detection signal in each of the detection signals output from the first tap 61a and the second tap 61b. In FIG. 5(a), the horizontal axis indicates distance, and the vertical axis indicates signal strength (sensor output). Moreover, "tap1" shown in FIG. 5(a) indicates the detection signal from the first tap 61a, and "tap2" indicates the detection signal from the second tap 61b. The relationship shown in FIG. 5A is obtained by measuring the object 200 for each distance using the distance measuring device 100.

As shown in FIG. 5A, the detection signals from the first tap 61a and the second tap 61b each have a shape that is horizontally inverted with respect to the distance "0".

FIG. 5B is a diagram showing the relationship between the signal strength ratio of the detection signals output from the first tap 61a and the second tap 61b and the distance to the target object 200. The horizontal axis in FIG. 5(b) indicates distance, and the vertical axis indicates the ratio of signal strengths. The relationship between the signal strength ratio and the distance to the target object 200 shown in FIG. 5(b) can be obtained in advance. The relationship may be such that the influence of environmental light is excluded.

The broken line in the left-right direction shown in FIG. 5(b) indicates one ratio obtained when the distance to the target object 200 is measured. The distance to the target object 200 is the intersection of the detection signal ratio (broken line) and the graph showing the relationship between the ratio and distance (solid line) within the dashed-dotted line frame.

[1-2. Operation of distance measuring device]
Next, the operation of the distance measuring device 100 configured as described above will be explained with reference to FIG. 6. FIG. 6 is a flowchart showing the operation (distance measuring method) of the distance measuring device 100 according to the present embodiment.

As shown in FIG. 6, the signal generation unit 20 generates a light emission control signal and an exposure control signal from the basic signal and the modulation signal (DSSS) (S11). The signal generation section 20 outputs a light emission control signal to the light source control section 30 and an exposure control signal to the light reception control section 50.

Next, the light source control section 30 causes the light source section 40 to emit light based on the light emission control signal (S12). In step S12, the light emission mode of the light source section 40 is controlled based on a light emission control signal obtained by adding modulation using a pseudorandom number to a basic signal. As a result, light with random light emission periods and light emission periods is emitted from the light source section 40.

Next, the light reception control section 50 controls the light reception section 60 based on the exposure control signal to receive the reflected light (S13). The exposure control signal includes a control signal for controlling the first tap 61a and a control signal for controlling the second tap 61b. Controls on/off of the tap 61a and the second tap 61b.

In step S13, the exposure mode of the light receiving section 60 is controlled based on an exposure control signal obtained by adding modulation using a pseudorandom number to the basic signal. Specifically, in step S13, the exposure mode of the photodiode 62 and the distribution of charges to the first tap 61a and the second tap 61b are controlled. It can also be said that in step S13, the exposure timings corresponding to the first tap 61a and the second tap 61b are controlled. Furthermore, when the distance measuring device includes a third tap, it can be said that in step S13, the exposure timings corresponding to the first tap 61a, the second tap 61b, and the third tap are controlled.

Then, when the exposure for a predetermined period (for example, one predetermined frame period) is completed, the light reception control section 50 sends a detection signal corresponding to the amount of charge accumulated in the first tap 61a and a detection signal to the second tap 61b. The signal processing unit 70 outputs a detection signal corresponding to the amount of accumulated charge.

Next, the signal processing unit 70 calculates the distance to the target object 200 based on the ratio using the two detection signals (S14). Thereby, the distance measuring device 100 can obtain the distance to the target object 200.

[1-3. Experimental result]
Next, noise resistance (susceptibility to disturbance light) of the distance measuring device 100 will be explained with reference to FIGS. 7A to 9. FIG. 7A is a first diagram showing a comparison of distance measurement results. FIG. 7B is a second diagram showing a comparison of distance measurement results. 7A and 7B show the results of measuring the target object 200 using the distance measuring device of the comparative example and the distance measuring device 100 according to the present embodiment. The objects 200 include a plate-shaped first object placed approximately 60 cm from the distance measuring device 100 and a plate placed above the first object and approximately 90 cm from the distance measuring device 100. The figure shows the results of measuring a second target object. 7A shows a distance image, and FIG. 7B shows a distance measurement result for each pixel 61 included in the straight line shown in FIG. 7A. In addition, in FIGS. 7A and 7B, experiments are conducted with a case in which a 100 MHz disturbance light is emitted as high-frequency noise (with noise) and a case in which a 100 MHz disturbance light is not emitted (w/o noise). .

Note that the distance measuring device of the comparative example is a three-tap distance measuring device (TOF camera) that emits pulsed light at regular intervals. In other words, the distance measuring device of the comparative example is a distance measuring device that does not perform modulation using pseudo-random numbers and uses the basic signal as it is to control the light source section and the light receiving section.

As shown in (a) and (b) of FIG. 7A and FIG. 7B, when high frequency noise is not generated, the distance measuring device of the comparative example and the distance measuring device 100 have similar results.

As shown in FIGS. 7A (c) and (d) and FIG. 7B, when high-frequency noise is generated, the distance to the first object is particularly deviated greatly in the distance measuring device of the comparative example. However, in the distance measuring device 100, the results are similar to those obtained when high frequency noise is not generated. In other words, the distance measuring device 100 is not easily affected by high frequency noise.

Next, simulation results of distance calculation when high frequency noise is applied will be described with reference to FIGS. 8 and 9. FIG. 8 is a diagram showing measurement results of a distance measuring device of a comparative example. FIG. 9 is a diagram showing measurement results of distance measuring device 100 according to this embodiment. FIGS. 8 and 9 show measurement results when 100 MHz disturbance light is emitted as high-frequency noise.

In (a) of FIG. 8, the horizontal axis shows the delay time (e.g., equivalent to distance), and the vertical axis shows the brightness of reflected light (or disturbance light) (e.g., equivalent to signal strength). . "tap0" shown in (a) of FIG. 8 shows the relationship between the brightness of environmental light and the delay time, and "tap1" and "tap2" show the relationship between the brightness of light including reflected light and the delay time. It shows a relationship. The relationship between brightness and delay time shown in FIG. 8(a), that is, the relationship between signal strength and distance to target object 200, can be obtained by measurement. In addition, in (b) of FIG. 8, the detection signal from the tap that accumulates charges generated by ambient light is subtracted from each of the two detection signals from the taps that accumulate charges generated by light including reflected light. A graph showing the ratio of the two subtracted detection signals is shown. Further, the delay time is synonymous with the flight time of light.

As shown in FIG. 8(a), in the distance measuring device of the comparative example, each signal is wavy, and as a result, the ratio graph is also wavy as shown in FIG. 8(b) (for example, , see the frame shown in FIG. 8(b)). This indicates that the measurement results of the distance measuring device of the comparative example are affected by high frequency noise. In such cases, it is difficult to measure accurate distances.

On the other hand, in the distance measuring device 100, the signal is not wavy as shown in FIG. 9(a), and as a result, the ratio graph is not wavy as shown in FIG. (For example, see the frame shown in FIG. 9(b)). This indicates that the measurement results of distance measuring device 100 according to this embodiment are not significantly affected by high frequency noise. In such cases, accurate distance measurements can be made.

Note that "tap0" shown in FIG. 9(a) indicates the first tap 61a, and "tap1" indicates the second tap 61b.

(Modification of Embodiment 1)
The distance measuring device according to this modification will be described below with reference to FIGS. 10 to 12. In this modification, an example will be described in which a control signal is generated by multiplexing a plurality of signals with different frequencies (frequency bands). An example in which three signals are multiplexed will be described below, but the number of signals to be multiplexed may be two or more. In addition, in distance measurement using the TOF method, increasing the frequency of the control signal tends to narrow the measurement range and increase the accuracy of distance, while decreasing the frequency tends to widen the measurement range and decrease accuracy of distance. be.

The configuration of the distance measuring device according to this modification may be the same as the distance measuring device 100 according to Embodiment 1 except for the pixels, and hereinafter, the components other than the pixels will be described using the reference numerals of the distance measuring device 100.

FIG. 10 is a diagram showing an example of a light emission control signal and an exposure control signal according to this modification.

As shown in FIG. 10, the light emission control signal includes a first signal (dashed line) which is a signal of a first frequency including a plurality of light emission periods and a plurality of light emission cycles, a second signal including a plurality of light emission periods and a plurality of light emission cycles. A second signal (solid line), which is a frequency signal, and a third signal (dotted chain line), which is a third frequency signal including a plurality of light emission periods and a plurality of light emission periods, are temporally multiplexed and generated. . The plurality of light emission periods and the plurality of light emission cycles included in the first signal, second signal, and third signal include mutually different light emission periods and light emission cycles, and the first signal, second signal, and light emission period in the light emission control signal are different from each other. The three signals are mutually different signals.

Further, as shown in FIG. 10, the exposure control signal includes a first signal (dashed line) which is a signal of a first frequency including a plurality of exposure periods and a plurality of exposure cycles; A second signal (solid line), which is a signal at the second frequency, and a third signal (dotted chain line), which is a signal at the third frequency including multiple exposure periods and multiple exposure cycles, are temporally multiplexed and generated. be done. The plurality of exposure periods and the plurality of exposure periods included in the first signal, the second signal, and the third signal include mutually different exposure periods and exposure periods, and the first signal, the second signal, and the plurality of exposure periods in the exposure control signal The three signals are mutually different signals.

Note that the first signal in the exposure control signal is a signal based on the first signal in the light emission control signal, and is an example of the first light reception signal. Further, the second signal in the exposure control signal is a signal based on the second signal in the light emission control signal, and is an example of the second light reception signal. Further, the third signal in the exposure control signal is a signal based on the third signal in the light emission control signal, and is an example of the third light reception signal.

Although the example of FIG. 10 shows an example in which the frequencies decrease in the order of the first frequency, the second frequency, and the third frequency, the order of the frequencies is not limited to this. Moreover, multiplexing means temporally connecting a second signal after a first signal. Furthermore, in the example of FIG. 10, the light emission control signal and the exposure control signal are signals whose phases are shifted.

Each of the first signal, second signal, and third signal is a signal modulated with a pseudo-random number. For example, the signal generation unit 20 generates a first signal obtained by modulating a first basic signal using a first pseudorandom number (first modulation signal), and a second pseudorandom number different from the first pseudorandom number as a second basic signal. (second modulation signal), and the third basic signal is modulated using a third pseudo-random number (third modulation signal) that is different from the first pseudo-random number and the second pseudo-random number. and a third signal. Note that the first to third basic signals may be the same signal or may be different signals.

The first signal, second signal, and third signal are mutually uncorrelated signals. In other words, the first signal, the second signal, and the third signal are signals that have different light emission periods or exposure periods, and different light emission periods or exposure periods. Therefore, when distance measurement is performed using the first signal, second signal, and third signal, interference due to mutual light is less likely to occur. That is, even if the first signal, second signal, and third signal are multiplexed, there is little effect on distance measurement. Note that if modulation using pseudo-random numbers is not performed, for example, the first signal will affect the exposure of the second signal, making it difficult to accurately measure the distance.

Therefore, between time t1 and t2, the light emission control signal is the second signal and the exposure control signal is the first signal, but since there is no correlation between the signals, the light emission from the light source unit 40 is the light reception by the light reception unit 60. There is little impact on The same holds true between times t3 and t4. In addition, since the light emission control signal and the exposure control signal are signals of the same frequency (for example, signals of the same waveform) before time t1, between time t2 and t3, and after time t4, the reflected light due to light emission from the light source section 40 The light receiving unit 60 can receive the light.

In this manner, in the distance measuring device according to the present modification, arbitrary light emission and exposure can be realized by multiplexing a plurality of signals generated from the basic signal and pseudo-random numbers in the time direction. Furthermore, by multiplexing signals, it becomes possible to solve the multipath problem and use it for optical communication. In addition, conventionally, measurements using signals of multiple frequencies are performed for each frequency, but by multiplexing randomly encoded signals as in this modification, measurement results using signals of multiple frequencies can be obtained. can be obtained in one measurement.

In addition, in this specification, the expressions "no correlation" and "no correlation" are not limited to no correlation at all, but include substantially no correlation and a small correlation below a predetermined value. It also includes having.

In the signal processing unit 70, evaluation (distance calculation) is performed for each of the first signal, second signal, and third signal, so that a wide measurement range can be measured simultaneously with high precision.

Note that the exposure control signal in FIG. 10 indicates the control signal for one of the two taps shown below, and the control signal for the other tap turns on or off the control signal for the one tap. It becomes an inverted signal.

The circuit configuration of the pixel of the light receiving section 60 according to this modification is the same as the circuit configuration of the pixel 61 of the light receiving section 60 of Embodiment 1, and a description thereof will be omitted. Note that the pixel 61 may further include a third tap (not shown, but for example, the third tap 61c shown in FIG. 13) connected to the photodiode 62. The third tap is, for example, a tap for accumulating charges caused by constant environmental light (global light) such as sunlight and illumination light.

The pixel 61 has a circuit configuration such that charges generated in one photodiode 62 are distributed to either the first tap 61a or the second tap 61b. For example, charges generated in the photodiode 62 by the first to third signals in the exposure control signal shown in FIG. 10 are accumulated in one of the first tap 61a and the second tap 61b, and Charges generated in the photodiode 62 by signals obtained by inverting the first to third signals are accumulated in the other of the first tap 61a and the second tap 61b.

Then, detection signals corresponding to the amount of charge accumulated in the first tap 61a and the second tap 61b are separately output to the signal processing section 70.

Pixel 61 may further have a tap connected to photodiode 62 to store charge due to constant ambient light.

The operation of the distance measuring device configured as described above will be explained with reference to FIG. 11. FIG. 11 is a flowchart showing the operation (distance measuring method) of the distance measuring device according to this modification.

As shown in FIG. 11, the signal generation unit 20 generates a multiplexed light emission control signal and exposure control signal from the basic signal and a plurality of modulation signals (DSSS) (S21). The signal generation unit 20 generates, for example, a light emission control signal and an exposure control signal as shown in FIG. The signal generation section 20 outputs a light emission control signal to the light source control section 30 and an exposure control signal to the light reception control section 50.

Next, the light source control section 30 causes the light source section 40 to emit light based on the light emission control signal (S22). Thereby, light corresponding to each of the first signal, second signal, and third signal whose light emission period and light emission period are random is emitted from the light source section 40.

Next, the light reception control section 50 controls the light reception section 60 based on the exposure control signal to receive reflected light for each modulated signal (S23). The exposure control signal includes a signal for controlling the first tap 61a and the second tap 61b, and the light reception control unit 50 turns on the first tap 61a and the second tap 61b based on the exposure control signal. Control off independently. Note that the light reception control unit 50 may control, for example, the first tap 61a and the second tap 61b so that the two taps are not turned on at the same time. It can also be said that in step S23, the exposure timings corresponding to the first tap 61a and the second tap 61b are controlled.

Then, when the exposure for a predetermined period (for example, one predetermined frame period) is completed, the light reception control section 50 outputs a detection signal according to the amount of charge accumulated in each of the first tap 61a and the second tap 61b. , are separately output to the signal processing section 70.

Next, the signal processing unit 70 calculates the distance to the target object 200 for each modulated signal (S24). The signal processing unit 70 calculates the distance to the target object 200 based on the detection signals of the first tap 61a and the second tap 61b.

FIG. 12 is a diagram showing measurement results of the distance measuring device according to this modification. FIG. 12 shows measurement results when 100 MHz disturbance light is not emitted as high-frequency noise. In (a) of FIG. 12, the horizontal axis indicates delay time (e.g., corresponds to distance), and the vertical axis indicates brightness of reflected light (e.g., corresponds to signal strength). In (a) of FIG. 12, the relationship between the detection signal obtained from the first tap 61a and the delay time is shown by the solid line (tap0), and the relationship between the detection signal obtained from the second tap 61b and the delay time is shown by the broken line (tap1). ).

In addition, the solid line (“multiplex”) in FIG. 12(b) is the ratio of tap0 and tap1 in FIG. 12(a), and this value is the light source signal (light source control signal) and the detection It represents the deviation from the signal, that is, the distance. Note that the three broken lines ("sequence 1" to "sequence 3") in FIG. 12(b) correspond to the first signal to the third signal in FIG. 10, and if they were not multiplexed, is the value of the ratio calculated.

As shown in FIG. 12(b), it can be seen that as the sequence changes from "sequence 1" to "sequence 3", the effective range of signal deviation (range of ratios of 0 or more) expands. On the other hand, as shown by the solid line in FIG. 12 (b), the slope when the delay time goes positive from near the center (delay time 0 nsec) is steep, so the difference between "sequence 1" and "sequence 3" before multiplexing is It can be seen that the distance resolution is higher than that of ``, and as a result, the measurement accuracy of the distance measuring device is high.

Furthermore, as shown in FIGS. 12(a) and 12(b), the measurement range is also expanded compared to the case of "sequence 1" using only the first signal.

In this way, the distance measuring device according to this modification multiplexes multiple signals with different frequencies (frequency bands) and controls light emission and exposure based on the multiplexed signals, thereby improving the accuracy of distance measurement. It is possible to achieve both improvement and expansion of the measurement range.

Furthermore, the distance measuring device according to this modification can also be used to identify TOF signals. For example, the distance measurement device receives light for distance measurement (disturbance light) emitted from another distance measurement device, and generates a light emission control signal to control the emission of the light based on the received light. , to identify which pseudorandom number sequence was used. The pseudo-random number sequence used in another ranging device may be, for example, the M sequence used in the ranging device according to this modification with a different seed, or may be a sequence different from the M sequence. good.

The distance measuring device then identifies the type, manufacturer, etc. of the other device based on the pseudo-random number series and the table in which product types, manufacturers, etc. are associated with each other, and the identified pseudo-random number series. Can be done. In other words, the signal processing unit 70 can identify other ranging devices from the identified pseudo-random numbers. Note that the distance measuring device and another distance measuring device may be placed in the same space, or may be placed in different spaces, for example.

(Embodiment 2)
The distance measuring device according to this embodiment will be described below with reference to FIGS. 13 to 18. In this embodiment, an example will be described in which random encoding using Galois field GF(q) is applied to a 3-tap distance measuring device. A Galois field is a set with a finite number of elements, and is also called a finite field. GF(q) is generated by calculating mod q for the calculation result. Note that "q" is the order.

[2-1. Configuration of ranging device]
The configuration of the distance measuring device according to this embodiment may be the same as the distance measuring device 100 according to Embodiment 1 except for the pixels, and the components other than the pixels will be described using the reference numerals of the distance measuring device 100 below. . FIG. 13 is a diagram showing a part of the circuit configuration of the pixel 161 of the light receiving section 60 according to this embodiment.

As shown in FIG. 13, the pixel 161 of the light receiving section 60 has a photodiode 62, a first tap 61a, a second tap 61b, and a third tap 61c as a circuit configuration. The pixel 161 is configured such that charges generated in one photodiode 62 are distributed to a first tap 61a, a second tap 61b, and a third tap 61c. Then, each of the detection signals corresponding to the amount of charge accumulated in the first tap 61a, second tap 61b, and third tap 61c is output to the signal processing section 70 separately.

The third tap 61c includes a transfer transistor 63c and an FD section 64c.

Further, in this embodiment, the signal generation unit 20 modulates the basic signal using modulation using a Galois field as modulation using pseudo-random numbers. For example, in modulation using a Galois field, the signal generation unit 20 modulates the basic signal using a Galois field GF(3) of three elements. That is, the order q of the Galois field is the same number as the number of taps of the distance measuring device. In this case, a pseudorandom number in a Galois field GF(3) of three elements is used as the pseudorandom number. Further, in this embodiment, a signal called "single ramp" (see (c) in FIG. 3) is used as the basic signal, but the present invention is not limited to this.

Note that the order q of the Galois field GF(q) may be a value larger than the number of taps of the distance measuring device. For example, a Galois field GF(5) or the like may be used as the Galois field. When the Galois field GF(3) is used in a three-tap method, the probability of appearance of on, off, and transition portions is 1/3 in each of the three taps. On is the first state in which all of one period is on, Off is a second state in which all of one period is off, and the transition part is the first state in which on and off are switched from one to the other within one period. There are 3 states (transition states). For example, but not limited to, the transition portion may be on for the first half of a period and off for the second half, or vice versa. Note that one period means, for example, one period in which one frame is divided into a plurality of periods, and the length thereof is set in advance.

For example, in the exposure control signal, there may be a case where it is desired to cause transition portions important for distance measurement to appear more frequently, and to lower the probability of occurrence of on and off portions. That is, in the exposure control signal, there are cases where it is desired to increase the number of transition portions and reduce the number of on and off times in other portions. Therefore, the signal generation unit 20 may change the appearance probabilities of on, off, and transition portions in a plurality of taps using a Galois field whose order q is larger than the number of taps. For example, in the case of the 3-tap method, the signal generation unit 20 generates pseudorandom codes with an appearance probability of 1/5 using the Galois field GF(5), and sends three of them to the first tap 61a and one to the first tap 61a. By allocating one to the second tap 61b and one to the third tap 61c, the probability of appearance of the transition part in the first tap 61a, second tap 61b, and third tap 61c is reduced to 3/5, 1/5, 1/5, and 1/5, respectively. It becomes possible to make it 5th grade.

Note that the target state for which the appearance probability is to be varied (for example, increased) is not limited to the transition portion, and may be one or two of on, off, and transition portions. For example, the signal generation unit 20 selects one of the first state, the second state, and the third state based on the pseudo-random numbers at one of the first tap 61a, the second tap 61b, and the third tap 61c. A control signal for one tap may be generated so that the probability of appearance of one state is different from that of other taps.

Note that the method for generating pseudorandom numbers is not limited to the above, and any known method using a Galois field may be used.

Further, in the present embodiment, the signal processing unit 70 determines the distance to the object 200 based on the ratio using the amount of charge accumulated in each of the first tap 61a, the second tap 61b, and the third tap 61c. It functions as a calculation unit that calculates . For example, the signal processing unit 70 sets the amount of charge accumulated when the first tap 61a is in the first state to Q2, the amount of charge accumulated when the second tap 61b is in the second state to Q3, and the amount of charge accumulated when the third tap 61c is in the second state. Assuming that the amount of charge accumulated when is in the third state is Q1 and the light emission period is T0, the flight time ΔT of the reflected light is calculated using (Equation 2) shown below.

(Q2-Q1)/(Q3-Q1)=ΔT/T0...(Formula 2)

Here, various signals in the distance measuring device will be explained with reference to FIGS. 14 and 15. First, the light emission control signal and the exposure control signal will be explained with reference to FIG. 14. FIG. 14 is a diagram showing an example of a light emission control signal and an exposure control signal according to this embodiment.

FIG. 14(a) shows the signal in the drain state, that is, in the non-exposed state.

FIG. 14B shows a light emission control signal for controlling the light source section 40, and specifically shows a signal supplied to the light emitting element of the light source section 40. By being controlled by the light emission control signal shown in FIG. 14(b), the light source section 40 emits light in a random light emission manner. The signal generation unit 20 modulates the basic signal using 2 bits of the pseudorandom number sequence for one period (for example, a light emission period or a light-off period). For example, when it is "00", it is turned on (light emission), when it is "11", it is turned off (light out), and when it is "10", it is turned on (light emission). The pseudorandom number sequence according to this embodiment is a random number sequence in which three states, on, off, and transition states, appear randomly.

FIG. 14C shows an exposure control signal for the first tap 61a, specifically a gate signal supplied to the gate electrode of the transfer transistor 63a.

FIG. 14(d) shows an exposure control signal for the second tap 61b, specifically a gate signal supplied to the gate electrode of the transfer transistor 63b.

FIG. 14(e) shows an exposure control signal for the third tap 61c, specifically a gate signal supplied to the gate electrode of the transfer transistor 63c.

FIG. 14(b) is a control signal obtained by adding modulation using a Galois field to the basic signal of the light emission control signal shown in FIG. 3(c). Further, each of (c) to (e) in FIG. 14 is a control signal obtained by adding modulation using a Galois field to the basic signal of the exposure control signal shown in (c) in FIG. (b) to (e) in FIG. 14 are mutually different signals, and are mutually uncorrelated signals.

As shown in FIGS. 14C to 14E, in this embodiment, each of the first tap 61a to third tap 61c is controlled to receive reflected light and ambient light. In other words, pixel 161 does not have a dedicated tap for accumulating charge due to ambient light.

Next, a method for calculating the detection signal and distance will be described with reference to FIG. 15. FIG. 15 is a diagram illustrating an example of a detection signal and distance calculation method according to the present embodiment. FIG. 15 shows detection signals when 100 MHz disturbance light is not emitted as high frequency noise.

(a) of FIG. 15 shows the brightness (luminance) of reflected light in each of the detection signals output from the first tap 61a (tap0), the second tap 61b (tap1), and the third tap 61c (tap2), It is a figure showing the relationship with delay time. The horizontal axis in (a) of FIG. 15 shows the delay time (e.g., equivalent to distance), and the vertical axis shows the brightness of reflected light (e.g., equivalent to signal intensity).

As shown in FIG. 15(a), the detection signals from the first tap 61a, the second tap 61b, and the third tap 61c each vary in brightness depending on the delay time. For example, changes in brightness cancel each other out. For example, in a range where the delay time is 30 ns or more, as the delay time becomes longer, the brightness of the third tap 61c decreases instead of increasing the brightness of the first tap 61a. The relationship shown in FIG. 15(a) is obtained by measuring the object 200 for each distance using a distance measuring device.

FIG. 15(b) is a diagram showing the relationship between the signal strength ratio of the detection signals output from each of the first tap 61a, second tap 61b, and third tap 61c and delay time. The horizontal axis of FIG. 15(b) shows the delay time, and the vertical axis shows the ratio of signal strengths. The relationship between the signal strength ratio and the distance to the target object 200 shown in FIG. 15(b) is obtained in advance.

The broken line in the left-right direction shown in FIG. 15(b) indicates one ratio obtained when the distance to the target object 200 is measured. The intersection of the detection signal ratio (broken line) and the graph showing the relationship between the ratio and delay time (solid line) is the currently measured distance to the target object 200. The distance measuring device according to the present embodiment has the advantage that the distance to the target object 200 is uniquely determined because the straight line indicating the ratio of detection signals intersects with the graph at only one point.

[2-2. Operation of distance measuring device]
Next, the operation of the distance measuring device configured as described above will be explained with reference to FIG. 16. FIG. 16 is a flowchart showing the operation (distance measurement method) of the distance measurement device according to this embodiment.

As shown in FIG. 16, the signal generation unit 20 generates a light emission control signal and an exposure control signal from the basic signal and the modulation signal (Galois field GF(3)) (S31). The signal generation unit 20 generates, for example, a light emission control signal as shown in FIG. 14(b) and an exposure control signal as shown in FIGS. 14(c) to 14(e). The signal generation section 20 outputs a light emission control signal to the light source control section 30 and an exposure control signal to the light reception control section 50.

Next, the light source control section 30 causes the light source section 40 to emit light based on the light emission control signal (S32). In step S32, the light emission mode of the light source section 40 is controlled based on a light emission control signal obtained by adding modulation using pseudo-random numbers to the basic signal. As a result, light is emitted from the light source section 40 with random light emission periods and light emission periods.

Next, the light reception control section 50 controls the light reception section 60 based on the exposure control signal to receive the reflected light (S33). The exposure control signal includes a control signal for controlling the first tap 61a, a control signal for controlling the second tap 61b, and a control signal for controlling the third tap 61c. The unit 50 independently controls on and off of the first tap 61a to the third tap 61c based on the exposure control signal. Note that the light reception control unit 50 controls the first tap 61a to the third tap 61c so that two or more taps may be turned on at the same time.

In step S33, the exposure mode of the light receiving section 60 is controlled based on an exposure control signal obtained by adding modulation using a pseudorandom number to the basic signal. Specifically, in step S33, the exposure mode of the photodiode 62 and the distribution of charges to the first tap 61a, second tap 61b, and third tap 61c are controlled. It can also be said that in step S33, the exposure timings corresponding to the first tap 61a, the second tap 61b, and the third tap 61c are controlled.

Then, when the exposure for a predetermined period (for example, one predetermined frame period) is completed, the light reception control section 50 outputs a detection signal according to the amount of charge accumulated in each of the first tap 61a to the third tap 61c. , are separately output to the signal processing section 70.

Next, the signal processing unit 70 calculates the distance to the target object 200 based on the ratio using the detection signals from the first tap 61a to the third tap 61c (S34). The signal processing unit 70 calculates one ratio from the three detection signals, and calculates the distance to the target object 200 based on the value of the one ratio.

[2-3. Experimental result]
Next, the noise resistance of the distance measuring device according to this embodiment will be explained with reference to FIGS. 17A to 18. FIG. 17A is a diagram showing measurement results of a distance measuring device of a comparative example. FIG. 17B is a first diagram showing measurement results of the distance measuring device according to the present embodiment. FIGS. 17A and 17B show distance images obtained by measuring object 200 using a distance measuring device according to a comparative example and a distance measuring device according to the present embodiment. The target object 200 is a plate-shaped object placed at a predetermined distance from the distance measuring device. “With noise” shown in FIGS. 17A and 17B indicates the measurement results when 100 MHz disturbance light is emitted as high-frequency noise. If there is no influence of high-frequency noise, the distance image "without noise" and the distance image "with noise" will be the same image.

In FIG. 17A, the distance at the lower right (circled frame) is significantly different between "with noise" and "without noise". This means that the distance measuring device of the comparative example is affected by high frequency noise.

On the other hand, in FIG. 17B, although the distance at the lower right (circular frame) is slightly different between "with noise" and "without noise", the difference is not as large as in the distance measuring device of the comparative example. This means that the distance measuring device according to the present embodiment is less susceptible to the effects of high frequency noise than the distance measuring device of the comparative example.

FIG. 18 is a second diagram showing the measurement results of the distance measuring device according to the present embodiment. FIG. 18 shows measurement results when 100 MHz disturbance light is emitted as high frequency noise. Without the influence of high frequency noise, the graph shown in FIG. 18 would be the same as the graph shown in FIG. 15.

In (a) of FIG. 18, the horizontal axis shows the delay time (e.g., equivalent to distance), and the vertical axis shows the brightness of reflected light (or disturbance light) (e.g., equivalent to signal strength). . “tap0” to “tap2” shown in FIG. 18(a) each indicate the relationship between the brightness of light and the delay time at each of the first tap 61a to third tap 61c. Moreover, (b) of FIG. 18 shows the relationship between the ratio of the three detection signals from the three taps and the delay time.

As shown in FIG. 18(a), in the distance measuring device according to the present embodiment, the signal is only slightly wavy, and as a result, the ratio graph is also slightly wavy, as shown in FIG. 18(b). It's only wavy and almost straight. This indicates that the measurement results of the distance measuring device according to this embodiment are only slightly affected by high frequency noise. In such cases, accurate distance measurements can be made.

Note that, as shown in FIG. 8 of the first embodiment, in the distance measuring device of the comparative example, each signal is undulating and is affected by high frequency noise. Although the distance measuring device according to the present embodiment is affected by high frequency noise, the influence is significantly suppressed compared to the distance measuring device of the comparative example.

(Operation example 1)
This operation example shows an operation example of the distance measuring device (3Tap ToF) according to the second embodiment. An example of operation using a signal obtained by adding Galois field modulation to the basic signal of FIG. 3(b) using the distance measuring device according to the second embodiment will be shown using FIGS. 19 to 20B. FIG. 19 is a diagram showing an example of a light emission control signal ((a) in FIG. 19) and an exposure control signal ((b) in FIG. 19) according to this operation example. FIG. 19 shows the control signal (emitted signal) of the light source unit 40, the first tap 61a (for example, "tap0"), the second tap 61b (for example, "tap1"), and the third tap 61c (for example, 3 shows a timing chart of the control signal (tap control) of “tap2”). Here, the basic waveform is a rectangular wave signal whose phase is shifted by 0, π/3, and 2π/3 with respect to the rectangular light source signal, and is modulated by a 3-bit signal of a Galois field (GF3). - Implemented in the timing chart by making it the exposure control signal of the third tap 61c.

20A is a diagram showing a graph (integral graph) obtained by simulation using the timing chart of FIG. 19, and FIG. 20B is a graph obtained by actually measuring using the timing chart of FIG. 19. FIG. FIGS. 20A and 20B show detection output from the first tap 61a (tap0 or tap0 minus dark noise), the second tap 61b (tap1 or tap1 minus dark noise), and the third tap 61c (tap2 or tap2 minus dark noise) FIG. 3 is a diagram showing the relationship between the luminance of reflected light and delay time for each signal. Moreover, FIG. 20B shows a graph measured using a delay layer in actual ToF.

As shown in FIG. 20B, since the error correction ability is higher than when using the basic signal shown in FIG. 3(c), by using FIG. 3(b) as the basic signal, the 2Tap It is expected that the measurement will be more robust than the conventional method.

(Operation example 2)
This operation example shows a first operation example of the distance measuring device (2TAP ToF+multiplexing) according to a modification of the first embodiment. Below, an example of operation when three different signals are multiplexed will be shown using FIGS. 21 to 22B. FIG. 21 is a diagram showing an example of a light emission control signal ((a) in FIG. 21) and an exposure control signal ((b) in FIG. 21) according to this operation example. FIG. 21 shows a timing chart of a control signal (emitted signal) of the light source unit 40 and a control signal (tap control) of each tap obtained by time-multiplexing three signals. Here, in-phase DSSS modulated sequences 1, 2, and 3, each having unit pulse lengths of 30 ns, 60 ns, and 120 ns and having the same total length, are temporally multiplexed by combining and used as control signals for light emission and exposure. So, I implemented it in the timing chart. For example, tap0 in FIG. 21(b) corresponds to the first tap 61a, and tap1 corresponds to the second tap 61b.

22A is a diagram showing a graph obtained by simulation using the timing chart of FIG. 21, and FIG. 22B is a diagram showing a graph obtained by actually measuring using the timing chart of FIG. 21. be.

(a) of FIG. 22A is a diagram showing a graph (integral graph) obtained by simulation using the timing chart of FIG. 21, in which the horizontal axis represents the delay time and the vertical axis represents the brightness of reflected light. show. In (a) of FIG. 22A, the relationship between the detection signal obtained from the first tap 61a and the delay time is shown by a solid line (tap0), and the relationship between the detection signal obtained from the second tap 61b and the delay time is shown by a broken line (tap1). ). The solid line (“multiplex”) in FIG. 22A (b) is the ratio of tap0 and tap1 in FIG. 22A (a), and this value represents the difference between the light source signal and the detection signal, In other words, it represents distance. Note that the three broken lines ("sequence 1" to "sequence 3") in (b) of FIG. 22A correspond to each of the three signals, and are the ratio values calculated if they were not multiplexed. It is. Further, "sequence sum" indicated by the two-dot chain line in FIG. 22A (b) is a graph obtained by adding up the graphs of "sequence 1" to "sequence 3".

FIG. 22B shows a graph of actual ToF measured using a delay layer in FIG.

As shown in FIGS. 22A and 22B, it can be confirmed that the measurement range is expanded.

Moreover, the graph of "sequence sum" shown in FIG. 22A (b) almost matches the solid line. This shows that the measurement results obtained using the control signal obtained by time-multiplexing three signals are accurate values.

(Operation example 3)
This operation example shows a second operation example of the distance measuring device (2TAP ToF+multiplexing) according to the modification of the first embodiment. In the following, an example of an operation in which three different signals are multiplexed with different phases shifted from the signal of the light source unit 40 will be shown using FIGS. 23 and 24. FIG. 23 is a diagram showing an example of a light emission control signal ((a) in FIG. 23) and an exposure control signal ((b) in FIG. 23) according to this operation example. FIG. 23 shows a timing chart of a control signal (emitted signal) of the light source unit 40 and a control signal (tap control) of each tap obtained by time-multiplexing three signals. Here, DSSS-modulated sequences 1, 2, and 3 having the same unit pulse length and the same total length with phase delays of 30 ns, 30 ns, and 0 ns are temporally multiplexed by coupling to the light source unit 40, and light emission/exposure is performed. This control signal was implemented in the timing chart. For example, tap0 in FIG. 23(b) corresponds to the first tap 61a, and tap1 corresponds to the second tap 61b.

FIG. 24 is a diagram showing a graph obtained using the timing chart of FIG. 23. FIG. 24(a) is a graph (integral graph) obtained by simulation using the timing chart of FIG. 23, where the horizontal axis represents the delay time and the vertical axis represents the brightness of reflected light. show. In (a) of FIG. 24, the relationship between the detection signal obtained from the first tap 61a and the delay time is shown by a solid line (tap0), and the relationship between the detection signal obtained from the second tap 61b and the delay time is shown by a broken line (tap1). ). Moreover, the solid line (“multiplex”) in FIG. 24(b) is the ratio of tap0 and tap1 in FIG. 24(a), and this value is the difference between the light source signal and the detection signal, In other words, it represents distance. Note that the three broken lines ("sequence 1" to "sequence 3") in FIG. 24(b) correspond to each of the three signals, and are the ratio values calculated if they were not multiplexed. It is. Further, "sequence sum" indicated by the two-dot chain line in FIG. 24(b) is a graph obtained by adding together the graphs of "sequence 1" to "sequence 3".

As shown in FIGS. 24A and 24B, it can be confirmed that by shifting the phase of the control signal, a non-symmetrical correlation graph can be obtained.

Further, the graph of "sequence sum" shown in FIG. 24(b) almost matches the solid line. This shows that the measurement results obtained using a control signal obtained by multiplexing three different signals with phase shifts are accurate values.

(Additional data for distance measurement)
Distance measurement in the following actual environment was additionally performed, and will be explained with reference to FIGS. 25 to 34. Note that below, modulation using pseudorandom numbers will also be referred to as pseudorandom number modulation. Further, although the distance measuring device 100 is a 3-tap type distance measuring device, it may be a 2-tap type distance measuring device.

(About the first distance measurement result)
First, the first distance measurement result will be explained with reference to FIGS. 25 to 29B. FIG. 25 is a diagram showing how the first distance measurement was additionally performed. FIG. 25 shows only the light source section 40 and the light receiving section 60 among the components of the distance measuring device 100.

As shown in FIG. 25, in the first distance measurement, plates 410 and 420 are placed as target objects. The plate 410 is placed at a distance of 45 cm from the light receiving section 60, and the plate 420 is placed at a distance of 60 cm from the light receiving section 60. Also, plate 420 is taller than plate 410. Therefore, when the plates 410 and 420 are viewed from the positions of the light source section 40 and the light receiving section 60, a part of the plate 420 can be seen above the plate 410.

For example, the plates 410 and 420 are arranged in parallel, and the optical axes of the light source section 40 and the light receiving section 60 are arranged to be perpendicular to the main surfaces of the plates 410 and 420.

Further, a noise light source 300 is arranged as a noise source that generates high frequency noise. The noise light source 300 is fixed in a posture that allows it to output high-frequency noise toward the plates 410 and 420 from an oblique direction. As the high frequency noise, disturbance light of 100 MHz is used.

Next, the presence or absence of high frequency noise and the results of actual environment distance measurement for each signal train will be described with reference to FIGS. 26A and 26B. FIG. 26A is a diagram showing distance measurement results (distance images) in the conventional method. The conventional method means that distance measurement is performed using a control signal that is generated without applying pseudo-random number modulation to the basic signal. Further, "no noise" means that the noise light source 300 is not outputting high frequency noise, and "with noise" means that the noise light source 300 is outputting high frequency noise. Note that the signal sequence refers to a basic signal (control signal) that has not been pseudo-randomly modulated (for example, the signal shown in FIG. 3), or a control signal that has been pseudo-randomly modulated to the basic signal (for example, the signal shown in FIG. 4). signal).

"(a) C-Double ramp" shown in FIG. 26A indicates the case where the basic signal shown in FIG. 3(d) is used as a control signal, and "(b) C-Square" indicates "(c) C-Hamiltonian" shows the case where the basic signal shown in (f) of FIG. 3 is used as the control signal. Note that "(a) C-Double ramp" is also written as "(a)".

As shown in FIG. 26A, in the conventional method, the measurement results with noise are different from the measurement results without noise. In other words, the conventional method is easily affected by high-frequency noise, and when there is noise, it is difficult to accurately measure distance.

FIG. 26B is a diagram showing a distance measurement result (distance image) in a method using pseudo-random number modulation (method of the present invention). “(d) DSSS” shown in FIG. 26B indicates a case where a non-repetitive unit of double ramp is used as a basic signal, and a control signal obtained by adding pseudo-random number modulation to the basic signal is used, and “(e) PR (pseudorandom number)-Double ramp" indicates the case where a control signal obtained by adding pseudorandom number modulation to the basic signal shown in (d) of FIG. 3 is used, and "(f) PR-Square" This shows a case where a control signal obtained by adding pseudo-random number modulation to the basic signal shown in (b) of FIG. A case is shown in which a modulated control signal is used.

In addition, "(d) DSSS" is also written as "(d)", "(e) PR-Double ramp" is also written as "(e)", and "(f) PR-Square" is also written as "(f)". "(g)PR-Hamiltonian" is also written as "(g)". In (d) to (g), M sequences are used as pseudorandom numbers. Further, the basic signals used in (e) to (g) are repetitive signals (periodic signals).

As shown in FIG. 26B, in both methods using pseudo-random number modulation, the measurement results with and without noise are almost the same. In other words, the method using pseudo-random number modulation is less susceptible to the effects of high-frequency noise and can perform accurate distance measurements even in the presence of noise.

Furthermore, in the method using pseudo-random number modulation, noise in the distance image becomes smaller in the order of (d)>(e)>(f)>(g). This is considered to be the effect of sensor noise, and the longer the coding curve is, the better the measurement results are obtained.

FIG. 27A is a diagram showing distance measurement results when a control signal obtained by adding pseudo-random number modulation to the basic signal shown in FIG. 3(b) is used. 27A (a) shows a distance image, and FIG. 27A (b) shows the distance measurement results for each pixel 61 included in the straight line (vertical straight line in the central part) shown in FIG. 27A (a). show.

FIG. 27B is a diagram showing a distance measurement result when a control signal obtained by adding pseudo-random number modulation to the basic signal shown in FIG. 3(f) is used. 27B (a) shows a distance image, and FIG. 27B (b) shows the distance measurement results for each pixel 61 included in the straight line (vertical straight line in the center) shown in FIG. 27B (a). show.

The vertical and horizontal axes in (a) of FIG. 27A and (a) of FIG. 27B indicate the pixel position (pixel index), and the horizontal axis of (b) of FIG. 27A and (b) of FIG. 27B indicates the pixel position. (pixel index), and the vertical axis indicates the measured distance ([mm]). The horizontal axis in FIG. 27A (b) corresponds to the vertical axis in FIG. 27A (a), and the horizontal axis in FIG. 27B (b) corresponds to the vertical axis in FIG. 27B (a). There is.

As shown in the dashed-dotted line frames in FIGS. 27A and 27B, it can be seen that the influence of noise is reduced in "(g) PR-Hamiltonian" than in "(f) PR-Square."

FIG. 28 is a diagram showing comparison results of distance measurement based on differences in basic signals. FIG. 28 shows the distances to the plates 410 and 420 and the RMSE (Root Mean Squared Error) in "(g) PR-Hamiltonian" and "(f) PR-Square." The smaller the RMSE, the less affected by noise.

As shown in FIG. 28, distance values close to the true values (450.00 mm and 600.00 mm) are obtained for both signal trains of "(g) PR-Hamiltonian" and "(f) PR-Square". ing. Furthermore, the distance error is smaller in "(g) PR-Hamiltonian" than in "(f) PR-Square", and it can be said that "(g) PR-Hamiltonian" is more robust against sensor noise. .

FIG. 29A is a diagram for explaining a coding curve when using the basic signal shown in FIG. 3(b). FIG. 29B is a diagram for explaining a coding curve when using the basic signal shown in FIG. 3(f). The coding curve is a curve that connects observed values at each tap corresponding to distance and is visualized in three-dimensional space.

As shown in FIGS. 29A and 29B, the total length of the coding curve when using the basic signal shown in FIG. 3(f) is longer than that when using the basic signal shown in FIG. 3(b). It can be seen that it is long. If the measured observed value contains an error, the measurement point does not exist on the coding curve, and the measurement point corresponding to the true distance has an ambiguity that is within the range surrounded by the dashed-dotted ellipse. Presumed. “O” in FIGS. 29A and 29B indicates an observation point containing an error. The arrow lines in FIGS. 29A and 29B indicate that an observation point containing an error corresponds to somewhere on the coding curve within the range surrounded by the ellipse (for example, at any position of the arrow). The longer the coding curve, the narrower the range of distances corresponding to this range, and thus the less ambiguous the distance estimation. In other words, "(g) PR-Hamiltonian" has less ambiguity in distance than "(f) PR-Square".

It can be seen from FIGS. 27A to 29B that the longer the coding curve, the smaller the influence of noise. Therefore, from the viewpoint of realizing the distance measuring device 100 that is more robust against noise, it is preferable to use a basic signal with a long coding curve, and (g)>(f)>(e)>( It can be said that the order of d) is suitable.

(About the second distance measurement result)
Next, the second distance measurement result will be explained with reference to FIGS. 30 to 34. FIG. 30 is a diagram showing how the second distance measurement was additionally performed.

As shown in FIG. 30, in the second distance measurement, a dog figurine 430 is placed as the target object. The figurine 430 is placed at a distance of 50 cm from the light receiving section 60. The figurine 430 is placed in front of the light source section 40 and the light receiving section 60.

Furthermore, as a noise source that generates high-frequency noise, a noise light source 300 is arranged as in the case of FIG. 25. As the high frequency noise, disturbance light of 100 MHz is used.

Next, the presence or absence of high frequency noise and the results of actual environment distance measurement for each signal train will be described with reference to FIGS. 31A and 31B. FIG. 31A is a diagram showing distance measurement results (distance images) in the conventional method. FIG. 31B is a diagram showing a distance measurement result (distance image) using a method using pseudo-random number modulation.

As shown in FIG. 31A, in the conventional method, the measurement results with noise are different from the measurement results without noise. In other words, the conventional method is easily affected by high-frequency noise, and when there is noise, it is difficult to accurately measure distance.

As shown in FIG. 31B, in both methods using pseudo-random number modulation, the measurement results with noise and those without noise are almost the same. In other words, the method using pseudo-random number modulation is less susceptible to the effects of high-frequency noise and can perform accurate distance measurements even in the presence of noise. Note that from FIG. 31B, it can be said that the longer the coding curve, the more robust the signal train is to sensor noise.

Next, evaluation results of distance measurement accuracy in a noise-free environment will be described with reference to FIGS. 32A to 32G. FIGS. 32A to 32G are diagrams showing evaluation results of distance measurement accuracy when using each signal train in a noise-free environment. In (a) of each of FIGS. 32A to 32G, the horizontal axis represents the delay time (delay [ns]) from the light emission of the light source unit 40, and the vertical axis represents the brightness of the reflected light (or disturbance light) (for example, , corresponding to signal strength). (b) in each of FIGS. 32A to 32G shows the relationship between the delay time and the distance to the target object (depth [mm]), where the horizontal axis shows the delay time and the vertical axis shows the distance. . Note that in each figure, when a solid line overlaps another line such as a broken line, the solid line is shown with priority.

As shown in FIGS. 32A to 32G, when there is no high-frequency noise, ideal measurement signals are obtained for all signals, and distance estimation is accurate. Ideal means, for example, that it is close to the true value and that the standard deviation is small.

Next, evaluation results of distance measurement accuracy in a noisy environment will be described with reference to FIGS. 33A to 33G. 33A to 33G are diagrams showing evaluation results of distance measurement accuracy when using each signal train in a noisy environment. In each of FIGS. 33A to 33G (a), the horizontal axis indicates the delay time, and the vertical axis indicates the brightness (corresponding to signal intensity, for example) of the reflected light (or disturbance light). (b) in each of FIGS. 33A to 33G shows the relationship between the delay time and the distance to the target object, with the horizontal axis showing the delay time and the vertical axis showing the distance. Note that the width of each graph (the width of the area expressed in gray scale) indicates the standard deviation of the error.

As shown in FIGS. 33A to 33C, when high-frequency noise is present, the conventional methods ((a) to (c)) include large noise in the measurement signal and large errors in distance estimation. On the other hand, as shown in FIGS. 33D to 33F, when high-frequency noise is present, the method using pseudorandom number modulation (method of the present invention) ((d) to (g)) suppresses noise in the measurement signal. , and there is no significant effect on distance estimation.

FIG. 34 is a diagram showing comparison results of distance estimation accuracy. As a comparative evaluation, FIG. 34 shows a comparison result of the root mean square error in the distance estimation shown in FIGS. 32A to 33G.

As shown in FIG. 34, it can be seen that the method using pseudo-random number modulation has a smaller root mean square error than the conventional method and is robust under noise conditions. Furthermore, the accuracy of (g) with a long coding curve is the highest.

In addition, in an environment where high-frequency noise exists, the root mean square error of the distance calculated using the method using pseudorandom number modulation (the method of the present invention) is smaller than the root mean square error of the distance calculated using the conventional method. For example, it may be 100 mm or less, 50 mm or less, 25 mm or less, or 10 mm or less.

(Other embodiments)
Although the distance measuring device and the like according to one or more aspects have been described above based on the embodiments, the present invention is not limited to the embodiments. Unless departing from the spirit of the present invention, the present invention may include various modifications that can be thought of by those skilled in the art to this embodiment, and embodiments constructed by combining components of different embodiments. .

For example, in the above embodiments, the signal generating section is configured to perform digital modulation, but it may be configured to perform analog modulation.

Furthermore, in the modification of the first embodiment, an example in which DSSS modulated signals are multiplexed is described, but signals generated by other modulation methods such as signals modulated using a Galois field may also be multiplexed. It's okay. Further, each of the signals to be multiplexed may be a signal of a single frequency.

Further, the distance measuring device in the above embodiments and the like may be used indoors or outdoors.

Further, in the above embodiments and the like, each component may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory.

Further, the order in which the steps in the flowchart are executed is for illustrative purposes to specifically explain the present invention, and may be in an order other than the above. Furthermore, some of the above steps may be executed simultaneously (in parallel) with other steps, or some of the above steps may not be executed.

Furthermore, the division of functional blocks in the block diagram is just an example; multiple functional blocks can be realized as one functional block, one functional block can be divided into multiple functional blocks, or some functions can be moved to other functional blocks. It's okay. Further, functions of a plurality of functional blocks having similar functions may be processed in parallel or in a time-sharing manner by a single piece of hardware or software.

Further, the distance measuring device according to the above embodiments may be realized as a single device, or may be realized by a plurality of devices. When a distance measuring device is realized by a plurality of devices, each component included in the distance measuring device may be distributed to the plurality of devices in any manner. When the distance measuring device is realized by a plurality of devices, the communication method between the plurality of devices is not particularly limited, and may be wireless communication or wired communication. Additionally, wireless communication and wired communication may be combined between devices.

Furthermore, each of the components described in the above embodiments may be realized as software, or typically, as an LSI that is an integrated circuit. These may be integrated into one chip individually, or may be integrated into one chip including some or all of them. Although it is referred to as an LSI here, it may also be called an IC, system LSI, super LSI, or ultra LSI depending on the degree of integration. Further, the method of circuit integration is not limited to LSI, and may be implemented using a dedicated circuit (a general-purpose circuit that executes a dedicated program) or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed or a reconfigurable processor that can reconfigure the connections or settings of circuit cells inside the LSI may be used after the LSI is manufactured. Furthermore, if an integrated circuit technology that replaces LSI emerges due to advances in semiconductor technology or other derived technology, that technology may of course be used to integrate the components.

A system LSI is an ultra-multifunctional LSI manufactured by integrating multiple processing units on a single chip, and specifically includes a microprocessor, ROM (Read Only Memory), RAM (Random Access Memory), etc. A computer system that includes: A computer program is stored in the ROM. The system LSI achieves its functions by the microprocessor operating according to a computer program.

Further, one aspect of the present invention may be a computer program that causes a computer to execute each characteristic step included in the ranging method shown in any one of FIGS. 6, 11, and 16.

Further, for example, the program may be a program to be executed by a computer. Further, one aspect of the present invention may be a computer-readable non-transitory recording medium in which such a program is recorded. For example, such a program may be recorded on a recording medium and distributed or distributed. For example, by installing a distributed program on a device having another processor and having that processor execute the program, it becomes possible to cause that device to perform each of the above processes.

(Additional note)
The following technology is disclosed by the description of the above embodiments and the like.

(Technology 1)
A distance measuring device that measures the distance to an object using a TOF (Time Of Flight) method,
A light source part,
a light-receiving element that receives light emitted by the light source and reflected by the object; and a first tap and a second tap to which charges generated when the light-receiving element receives the reflected light are distributed. and a light receiving section having a third tap;
Control signals for the light emission timing of the light source unit and the exposure timing corresponding to the first tap, the second tap, and the third tap are generated by modulating the basic signal using pseudorandom numbers. A distance measuring device comprising a signal generating section.

(Technology 2)
The distance measuring device according to technique 1, wherein the modulation using the pseudo-random numbers is modulation using a Galois field.

(Technology 3)
The distance measuring device according to technique 2, wherein in the modulation using the Galois field, a pseudorandom number in the Galois field having the same number of orders as the number of taps that the light receiving section has is used as the Galois field.

(Technology 4)
The ranging device according to technique 2, wherein in the modulation using the Galois field, a pseudorandom number in the Galois field having an order larger than the number of taps included in the light receiving section is used as the Galois field.

(Technique 5)
Each of the first tap, second tap, and third tap has a first state of being on for one period, a second state of being off for one period, and one of on and off within one period. and a third state that switches to the other state,
The signal generation unit is configured to change the first state, the second state, and the third state in one of the first tap, the second tap, and the third tap based on the pseudo-random number. The distance measuring device according to any one of techniques 1 to 4, wherein a control signal for one of the taps is generated so that the probability of appearance of one of the states is different from that of other taps.

(Technology 6)
The signal generation unit generates a first signal obtained by modulating the basic signal using a first pseudo-random number, and a second signal obtained by modulating the basic signal using a second pseudo-random number different from the first pseudo-random number. generating the control signal by multiplexing the signal in the time direction,
Any of techniques 1 to 5, wherein the light receiving unit accumulates charges generated by reflected light received by emitting light based on the first signal and reflected light received by emitting light based on the second signal in mutually different taps. Distance measuring device described in Crab.

(Technology 7)
Another distance measuring device is arranged in the space where the distance measuring device is arranged,
A signal processing unit that identifies a pseudorandom number used for emitting the disturbance light based on the disturbance light received by the light receiving unit, and identifies the other distance measuring device from the identified pseudorandom number. 7. The distance measuring device according to any one of 1 to 6.

(Technology 8)
The method according to any one of techniques 1 to 7, further comprising a calculation unit that calculates the distance based on a ratio using the amount of charge accumulated in each of the first tap, the second tap, and the third tap. distance measuring device.

(Technology 9)
The distance measuring device according to any one of techniques 1 to 8, wherein the basic signal is a single frequency signal.

(Technology 10)
The basic signal of the control signal for the light emission timing is a pulse-like signal,
The distance measuring device according to any one of Techniques 1 to 9, wherein the basic signal of the control signal for the exposure timing is a trapezoidal signal having different phases at the first tap, the second tap, and the third tap. .

(Technology 11)
The distance measuring device according to any one of Techniques 1 to 10, wherein the root mean square error of distance measured in an environment where high frequency noise is present is 100 mm or less.

(Technology 12)
A distance measuring device that measures the distance to an object using a TOF (Time Of Flight) method,
A light source part,
The light-receiving element receives reflected light generated by the light emitted by the light source being reflected by the object, and the light-receiving element has a first tap and a second tap to which charges generated when the light-receiving element receives the reflected light are distributed. A light receiving section,
a signal generation unit that generates a control signal for the light emission timing of the light source unit and the exposure timing corresponding to the first tap and the second tap by modulating a basic signal using pseudo-random numbers; Equipped with a distance measuring device.

(Technology 13)
A distance measurement method performed by a distance measurement device that measures the distance to an object using a TOF (Time Of Flight) method,
The distance measuring device is
A light source part,
a light-receiving element that receives light emitted by the light source and reflected by the object; and a first tap and a second tap to which charges generated when the light-receiving element receives the reflected light are distributed. and a light receiving section having a third tap,
The distance measuring method is
A control signal for controlling each of the light emission timing of the light source section, the exposure timing of the light receiving element, and the distribution of charges to the first tap, the second tap, and the third tap is simulated as a basic signal. A distance measurement method that generates distance by adding modulation using random numbers.

INDUSTRIAL APPLICATION This invention is useful for the distance measuring device etc. which measure the shape of a target object, etc.

10 control section 20 signal generation section 30 light source control section 40 light source section 50 light reception control section 60 light reception section 61, 161 pixel 61a 1st tap 61b 2nd tap 61c 3rd tap 62 photodiode 63a, 63b, 63c transfer transistor 64a, 64b , 64c FD section 70 Signal processing section (calculation section)
100 Range finder 200 Object 300 Light source for noise 410, 420 Board 430 Figurine t1, t2, t3, t4 Time

Claims (13)

A distance measuring device that measures the distance to an object using a TOF (Time Of Flight) method,
A light source part,
a light-receiving element that receives light emitted by the light source and reflected by the object; a first tap, a second tap, and a second tap to which charges generated when the light-receiving element receives the reflected light are distributed; a light receiving section having a third tap;
Control signals for the light emission timing of the light source unit and the exposure timing corresponding to the first tap, the second tap, and the third tap are generated by modulating the basic signal using pseudorandom numbers. A distance measuring device comprising a signal generating section. The distance measuring device according to claim 1, wherein the modulation using the pseudorandom numbers is modulation using a Galois field. The ranging device according to claim 2, wherein in the modulation using the Galois field, a pseudorandom number in the Galois field having the same number of orders as the number of taps that the light receiving section has is used as the Galois field. The distance measuring device according to claim 2, wherein in the modulation using the Galois field, a pseudorandom number in the Galois field having an order larger than the number of taps included in the light receiving section is used as the Galois field. Each of the first tap, second tap, and third tap has a first state of being on for one period, a second state of being off for one period, and one of on and off within one period. and a third state that switches to the other state,
The signal generation unit is configured to change the first state, the second state, and the third state in one of the first tap, the second tap, and the third tap based on the pseudo-random number. The distance measuring device according to claim 4, wherein a control signal for one of the taps is generated so that the probability of appearance of one of the taps is different from that of the other taps. The signal generation unit generates a first signal obtained by modulating the basic signal using a first pseudo-random number, and a second signal obtained by modulating the basic signal using a second pseudo-random number different from the first pseudo-random number. The control signal for the light emission timing is generated by multiplexing the signals in the time direction, and a first light reception signal based on the first signal and a second light reception signal based on the second signal are generated. The distance measuring device according to any one of claims 1 to 5, wherein the control signal for the exposure timing is generated by multiplexing the signals in the time direction. Another distance measuring device is arranged in the space where the distance measuring device is arranged,
A signal processing unit that identifies a pseudorandom number used for emitting the disturbance light based on the disturbance light received by the light receiving unit, and identifies the other distance measuring device from the identified pseudorandom number. The distance measuring device according to any one of items 1 to 5. Any one of claims 1 to 5, further comprising a calculation unit that calculates the distance based on a ratio using the amount of charge accumulated in each of the first tap, the second tap, and the third tap. Distance measuring device described in section. The distance measuring device according to any one of claims 1 to 5, wherein the basic signal is a single frequency signal. The basic signal of the control signal for the light emission timing is a pulse-like signal,
6. The basic signal of the control signal for the exposure timing is a trapezoidal signal having different phases at the first tap, the second tap, and the third tap. Ranging device. The distance measuring device according to any one of claims 1 to 5, wherein the root mean square error of distance measured in an environment where high frequency noise is present is 100 mm or less. A distance measuring device that measures the distance to an object using a TOF (Time Of Flight) method,
A light source part,
a light-receiving element that receives light emitted by the light source and reflected by the object; and a first tap and a second tap to which charges generated when the light-receiving element receives the reflected light are distributed. a light receiving section having;
a signal generation unit that generates a control signal for the light emission timing of the light source unit and the exposure timing corresponding to the first tap and the second tap by modulating a basic signal using pseudo-random numbers; Equipped with a distance measuring device. A distance measurement method performed by a distance measurement device that measures the distance to an object using a TOF (Time Of Flight) method,
The distance measuring device is
A light source part,
a light-receiving element that receives light emitted by the light source and reflected by the object; a first tap, a second tap, and a second tap to which charges generated when the light-receiving element receives the reflected light are distributed; and a light receiving section having a third tap,
The distance measuring method is
A control signal for controlling each of the light emission timing of the light source section, the exposure timing of the light receiving element, and the distribution of charges to the first tap, the second tap, and the third tap is simulated as a basic signal. A distance measurement method that generates distance by adding modulation using random numbers.

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