JP2000206244A - Distance-measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately measure a distance with reducing influences of noises of light- receiving elements by providing a light-receiving means with two kinds of light-receiving elements one of which responds slower than the other and has a higher sensitivity than the other. SOLUTION: A light-projecting means 10 projects to an object to be measured a projection light F which is modulated by a modulation signal of a mixture of a pulse signal and a reference signal. A reflecting light R of the projection light F reflected by the object to be measured is received by a first light-receiving element 22 and a second light-receiving element 23 of a light-receiving means 11 independently and concurrently. A first measuring part 12 detects a time difference between a pulse signal component of a first receive signal of the reflecting light R detected by the first light-receiving element 22 and a pulse signal component of the projected light. A distance to the object to be measured is schematically calculated from the time difference. A second measuring part 13 detects a phase difference between a reference signal component of the second receive signal of the reflecting light R detected by the second light-receiving element 23 and a reference signal component of the projected light. Then, information on a distance within one phase difference to the object to be measured is calculated from the phase difference. A distance-calculating part 14 calculates a distance to the object 2 to be measured on the basis of the schematic calculation result of the first measuring part 12 and the distance information of the second calculating part 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for improving a distance measuring apparatus using light waves.

[0002]

2. Description of the Related Art As a distance measuring apparatus using a light wave, a pulse-like light wave is projected toward a distance measuring object, reflected light from the distance measuring object is detected, and the distance measuring object is determined from the reflection time and the light speed. And a method of calculating the distance to the target (hereinafter, abbreviated as a time difference method), and a method in which a light wave modulated by a reference signal having a constant period is projected toward a distance measurement target, and reflected light from the distance measurement target is detected. Calculating the distance to the object to be measured from the phase difference between the projected light and the reflected light (hereinafter, abbreviated as a phase difference method)
There are things.

In the case of the above time difference method, the distance measurement resolution is limited by the time resolution at the time of measuring the reflection time. In order to obtain an accuracy of 1 cm as the distance measurement resolution, a time resolution of 100 ps is required. There is a problem that it is extremely difficult. On the other hand, in the case of the above phase difference method, the phase difference is 0 to
Since the detection can be performed only in the range of 2π (one cycle), the reciprocating distance to the measurement target is limited in principle to a distance corresponding to one cycle of the reference signal having the constant cycle. That is, assuming that the wavelength of the reference signal is λ and the distance corresponding to the detected phase difference is φ, the distance D to the distance measurement target can be generally expressed as shown in Expression 1, but the simple phase difference method Then, only the distance φ corresponding to the phase difference in the above equation is measured, and the distance measurement range is limited to a maximum of λ / 2 with n = 0.

[0004]

D = (n × λ + φ) / 2 (n is an integer of 0 or more)

Therefore, when the distance is measured beyond the above range, the wavelengths are changed to a plurality by using reference signals of different periods, the respective distances φ are measured, and the integer n is determined from the measurement result. Specifically, the distance D was determined.

As described above, the time difference method has a problem in the distance measurement accuracy, and the phase difference method has a limitation in the distance measurement range.
Based on the distance determined by the time difference method, an integer n
And a mixing method for determining the distance D has been proposed.
For example, in Japanese Patent Application Laid-Open No. H10-96778, the present inventors project a light wave modulated by a signal obtained by adding and mixing a pulse signal and a sine wave signal having a frequency higher than the repetition frequency of the pulse toward a distance measurement target. Then, the reflected light from the object to be measured is detected, the time difference between the projected light and the reflected light is detected from the pulse signal component, the phase difference between the projected light and the reflected light is detected from the sine wave signal component, and the time difference is detected. A method has been proposed in which the necessary correction is performed from the distance φ corresponding to the approximate distance and the phase difference calculated from Equation (1), and the integer n is specified to obtain the distance D. Therefore, since the distance measurement resolution can be ensured by the phase difference method, there is a feature that the distance measurement range can be improved by lowering the distance measurement resolution of the time difference method and extending the distance measurement range.

[0007]

However, in the case of the above-mentioned mixed system, the light-receiving element for receiving the reflected light has a high cut-off frequency or a rising edge of the output signal so as to accurately detect a high-frequency signal component. It is necessary to use an element with a high operating speed. However, in general, a light-receiving element having a high operation speed has a lower light-receiving sensitivity than a light-receiving element having a low operation speed, and thus has a poor SN ratio. In addition, the influence of specific noise due to a change in environmental light or the like may not be ignored. In particular, when determining the time difference between the projected light and the reflected light of the pulse signal, the above-described noise of the light receiving element directly affects. For example, when the noise occurs before receiving the reflected light, the noise may be erroneously recognized as the reflected light, and a large error may occur in the distance to the distance measurement target.
When a single light-receiving element with a high operating speed receives reflected light, it is necessary to divide the light-receiving signal and process one for signal processing for approximate distance detection and the other for signal processing for phase difference detection. However, by dividing the light receiving signal, the signal intensity required for each signal processing is reduced by half, thereby deteriorating the SN ratio, and this is a problem particularly when the reflected light intensity is weak.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has as its object to solve the above-described problems and to determine the distance from a time difference and a phase difference between projected light and reflected light to a distance measurement target. Another object of the present invention is to provide a distance measuring apparatus capable of performing high-accuracy distance measurement by reducing the influence of noise of a light receiving element in a distance measuring method for measuring the distance.

[0009]

According to a first aspect of the present invention, there is provided a distance measuring apparatus according to the present invention. A light projecting means for projecting a light wave intensity-modulated by a modulation signal formed by mixing a signal and a reference signal having a higher frequency than the pulse signal toward a distance measuring object, and a light receiving means for receiving reflected light from the distance measuring object Means, a first measuring unit for estimating a distance to the object to be measured from a time difference between the projected light projected from the light projecting means and the reflected light, and the distance measurement based on a phase difference between the projected light and the reflected light. A second measurement unit that calculates predetermined distance information to the target; and a distance calculation unit that calculates a distance to the distance measurement target from the approximate result of the first measurement unit and the distance information of the second measurement unit. A distance measuring device, wherein one of the light receiving means is the other The first light receiving signal detected by the first light receiving element having a slow response but having a high light receiving sensitivity is used by the first measuring section. The second light receiving signal detected by the second light receiving element, which is the other light receiving element, is used in the second measuring section. As a method of generating the modulation signal by mixing the pulse signal and the reference signal, addition and mixing in which the reference signal is superimposed on the pulse signal and multiplication in which the predetermined level of the pulse signal is output only during the output period are performed. Including both mixed. In addition, the predetermined distance information to the distance measurement target means a propagation distance corresponding to the phase difference of the light wave or a half distance thereof, and specifically, the distance φ or the distance in Expression 1 in the description of the related art. Half the value is equivalent. If the reflected light is received before the light wave changes by one phase, the half distance corresponds to the distance to the object to be measured.

[0010] The second characteristic configuration is, as described in claim 2 of the claims, in addition to the first characteristic configuration described above, of the first light receiving element and the second light receiving element. Are located around the other.

[0011] The third characteristic configuration is, as described in claim 3 of the claims, in addition to the above-mentioned second characteristic configuration, wherein the first light receiving element is provided around the second light receiving element. It is located at the point.

The operation and effect of the above-described configuration will be described below. According to the first characteristic configuration, the light projecting means projects the light wave modulated by the modulation signal formed by mixing the pulse signal and the reference signal toward the distance measurement target, and the projected light is used for the distance measurement. The first light-receiving element and the second light-receiving element of the light-receiving means receive the light reflected by the object independently and in parallel.
The measuring unit detects a time difference between a pulse signal component of the first light receiving signal of the reflected light detected by the first light receiving element and a pulse signal component of the projection light, estimates a distance to the distance measurement target from the time difference, and The second part of the reflected light detected by the second light receiving element by the measuring unit
The phase difference between the reference signal component of the received light signal and the reference signal component of the projection light is detected, and distance information within one phase difference from the phase difference to the object to be measured is calculated. The distance to the distance measurement target can be calculated with high accuracy based on the approximate result and the distance information of the second measurement unit. Here, since the sensitivity of the first light receiving element is higher than that of the second light receiving element, the approximate distance can be reliably measured even if the reflected light intensity is weak, and the pulse signal component has a relatively low frequency. The operating speed of the first light receiving element can be kept low, the sensitivity can be increased, and the influence of noise can be reduced. As a result, it is possible to avoid occurrence of a large error in the measurement result of the approximate distance, and to use the distance information measured by the second measuring unit accurately and effectively. That is, if an error of one phase difference or more occurs in the measurement result of the first measurement unit, the distance to the distance measurement target can no longer be calculated with high accuracy, but such a situation can be avoided. Furthermore, 2
The first light-receiving signal for measuring the approximate distance and the second light-receiving signal for detecting the phase difference are separately and independently generated using different types of light-receiving elements, so that compared to the case of receiving light with a single light-receiving element, Since the frequency band of the amplifier circuit for each light receiving signal can be narrowed for each of the pulse signal component and the reference signal component, the amplification factor can be increased. In particular, for the signal processing of the second light receiving signal, the high performance of the signal processing can be achieved even though the second light receiving element having the same high-speed operation as the case of receiving light with a single light receiving element is used. is there. In addition, since two types of light receiving elements having different sensitivities are used, when the reflected light intensity is weak, the degree of light reception failure can be analyzed based on the detection result of each light receiving element. Specifically, when the first light receiving element having high sensitivity cannot detect the reflected light, it is assumed that the reflected light intensity is extremely weak and the reflected light cannot be received at all due to a low reflectance of the object to be measured. If it can be determined and only the second light receiving element cannot receive light, it is possible to measure only the approximate distance based on the first light receiving signal detected by the first light receiving element.

According to the second characteristic configuration, when the light receiving means is configured to focus the reflected light on the first and second light receiving elements, the peak of the signal intensity of the first and second light receiving signals is obtained. The deviation between the focal position of the reflected light and the position of the light receiving surface of each light receiving element can be detected from the change in the value or the average value, and by adjusting the focal position or the position of the light receiving surface based on the detection result, a good The light receiving state can be maintained.

According to the third characteristic configuration, the first and second
When the distribution of the reflected light intensity on the light receiving surface of the light receiving element has an intensity distribution pattern that is higher toward the center, low intensity reflected light at the peripheral portion can be received by the plurality of highly sensitive first light receiving elements. Thus, both the pulse signal component and the reference signal component can be satisfactorily detected from the reflected light.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a distance measuring apparatus according to the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a distance measuring apparatus 1 according to the present invention includes a pulse signal B having a predetermined repetition period and a sine wave having a higher frequency than the pulse signal B only during a high level period of the pulse signal. A light projecting unit 10 for irradiating a lightwave intensity-modulated by a modulation signal C obtained by multiplying and mixing the two signals so as to output a signal A toward the distance measurement target 2, and a reflected light R from the distance measurement target 2 A time difference between the respective pulse signal components of the projected light F emitted from the light projecting means 10 and the reflected light R received by the light receiving means 11, and the measurement is performed based on the time difference. A first measuring unit 12 for calculating an approximate distance D 'to the distance measurement target 2 and a phase difference between respective reference signal components of the projection light F and the reflection light R, and from the phase difference to the distance measurement target 2 Measuring unit 1 for calculating distance information φ in one phase of A distance calculation unit 14 that calculates a distance D to the distance measurement target 2 from the approximate distance D ′ calculated by the first measurement unit 12 and the distance information φ calculated by the second measurement unit 13 And a configuration including

The light projecting means 10 includes a laser light source 15 such as a semiconductor laser capable of intensity modulation, a modulation section 16 for intensity modulating the projection light F emitted from the laser light source 15, and a projection light emitted from the laser light source 15. A collimating lens 17 for converting the light F into parallel light, and a reflecting mirror 18 for bending the projection light F passing through the collimating lens 17 toward the distance measurement target 2
And the main part.

The modulation section 16 includes a first oscillation circuit 19 for oscillating the 100 MHz sine wave reference signal A (indicated by "A" in FIG. 2) and the pulse signal B (FIG. 2) having a repetition period of 10 .mu.s. In FIG. 2, the pulse generator 20 oscillates. The drive current of the laser light source 15 is modulated by a modulation signal C (indicated by “C” in FIG. 2) obtained by multiplying and mixing the reference signal A and the pulse signal B. Is modulated, and as a result, the projection light F emitted from the laser light source 15 has a signal waveform ("C" in FIG. 2) as shown in FIG.
) Is intensity-modulated.

The light receiving means 11 includes two types of first light receiving element 21 and second light receiving element 22 for converting the light intensity of the reflected light R into an electric signal, and the first and second light receiving elements 2 for reflecting the reflected light R.
A converging lens 23 for converging light to the light sources 1 and 22 is configured as a main part. The first light receiving element 21 is the first light receiving element 21.
The second light receiving element 22 is for detecting the first light receiving signal S ₁ input to the measuring unit 12, and the second light receiving element 22 is for detecting the second light receiving signal S ₂ input to the second measuring unit 13. The first light receiving element 21 is provided with the second light receiving element 22
Use one with higher sensitivity and lower operating speed. The first
Various photoelectric conversion elements such as a photodiode, a photoconductor, and a phototransistor can be used as the second light receiving elements 21 and 22. In the case where a photodiode is used, in the present embodiment, a GaAsP photodiode (NEP (Noise Eq.) Is used for the first light receiving element 21 in consideration of the oscillation frequency of the pulse signal B and the reference signal A.
uivalent Power) = 1.5 × 10 ⁻¹⁵ W / Hz ^1/2 , dark current = 10 pA, rise time of detection output = 1 μsec), and a silicon avalanche photodiode is used for the second light receiving element 22. (Dark current = 0.5 nA, cutoff frequency = 1 GHz). By the way, the first light receiving element 21 has a rise time of the first light receiving element 21 as slow as 1 μsec and cannot follow the reference signal A of 100 MHz.
Substantially functions as a low pass filter, the reference signal component is removed from the reflected light R, so that only the pulse signal component is extracted in the first light receiving signal S _1. FIG.
As shown in the figure, the first light receiving element 21 and the second light receiving element 2
Reference numeral 2 denotes a configuration in which a plurality of the first light receiving elements 21 are arranged around the second light receiving element 22.

The first measuring unit 12 receives a first light receiving signal S ₁ generated by photoelectrically converting the reflected light R by the first light receiving element 22 and a pulse signal B from the pulse oscillator 20. A first timer 24 for measuring the time difference t between the two pulses
And an approximate distance D ′ from the time difference t to the distance measurement target 2 as D ′ = t × c / 2 (c = light speed).
And an arithmetic unit 25. The first timer 24 is constituted by an 8-bit binary counter having an operating frequency of 200 MHz, starts counting from the input of the pulse signal B, and continues counting until the input of the first light receiving signal S _1. The bit count result U is output. The 8-bit output value U is stored in a predetermined memory area (8 bits) in the first arithmetic unit 25. The first measuring unit 1
The ranging resolution of 2 is limited by the time resolution of the counter,
Since it takes 5 ns to count one bit, the length is 0.75 m. Therefore, the first arithmetic unit 25 is configured to use the first timer 2
The approximate distance D 'can be calculated by multiplying the output value U of 4 by 0.75 m which is the distance measurement resolution. The most significant bit of the 8-bit binary counter uses the lower 7 bits because it is used to detect a state in which ranging is impossible.
Therefore, the distance measurement limit of the first measurement unit 12 is 0.7
5mx (2 < ⁷ > -1) = 95.25m. Therefore, for example, when the distance to the distance measurement target 2 exceeds 95.25 m, the most significant bit of the 8-bit binary counter is set,
Detects distance measurement disabled state. The repetition period 10 μs of the pulse signal B is equal to the time (5 ns × 2 ⁸ = 1.28) until the most significant bit of the 8-bit binary counter rises.
μs).

The second measuring section 13 is configured to detect the second light receiving signal.
S_Two To detect a sine wave signal S ′ as a reference signal component.
And an oscillation frequency of the first oscillation circuit 1
100.1MHz sine wave signal 100KHz higher than 9
A second oscillation circuit 27 for oscillating A ', and the first oscillation circuit
19 and the 100 MHz reference signal A
2 100.1 MHz sine output from the oscillation circuit 27
From the signal obtained by integrating the wave signal A '
First beat signal A₁ First low-pass filter 2 for extracting
8 and 100 MHz positive output from the amplifier 26.
The product of the sine wave signal S 'and the 100.1 MHz sine wave signal A'
Second beat signal of 100 KHz from the signal obtained by calculation
A_Two And a second low-pass filter 29 for extracting
Beat signal A₁ Is shaped into a first rectangular wave A_Three Output
The first comparator 30 and the second beat signal A_Two To
Waveform shaping and second rectangular wave A_Four Second comparator that outputs
And the first rectangular wave A_Three And the second rectangular wave A_Four To
Input and both rectangular waves A_Three , A _Four The time difference between
The reference signal A corresponding to the reference signal component of F and the reflected light R
With the sine wave signal S 'corresponding to the reference signal component
A second timer 32 for outputting an output value L corresponding to the difference,
Of the reference signal A and the sine wave signal S ′ from the output value L of
Calculates distance information φ to the distance measurement target 2 in one phase
It is composed of a second calculating unit 33 for outputting.

The second measuring section 13 forms a so-called heterodyne detection circuit. The first beat signal A ₁ contains the phase information of the reference signal A, and the second beat signal A ₂ Is the distance measurement target 2 of the sine wave signal S ′.
The phase information includes phase information to which a phase shift corresponding to the distance up to is added, and the second timer 32 can calculate the phase difference.

The second timer 32 has an operating frequency of 25.2.
It is constituted by a 6 MHz 8-bit binary counter, starts counting from the input of the first rectangular wave A ₃ , continues counting until the input of the second rectangular wave A ₄ , and outputs the 8-bit count result L. Output. The 8-bit output value L is stored in a predetermined memory area (8 bits) in the second arithmetic unit 33. When the phase difference of the 100 KHz signal is divided into 256 (2 ⁸ ) by an 8-bit binary counter, the operating frequency needs to be 25.6 MHz. here,
The maximum displacement distance, which is the propagation distance during one phase change of the projection wave F intensity-modulated by the 100 MHz reference signal A, is 3 m, which is the wavelength of the reference signal A (λ = c / 100 MHz). Half is 2 by 8-bit binary counter
Since the one-way distance to the distance measurement target 2 in one phase is measured by dividing into 56, the distance measurement resolution of the second measurement unit 13 is 5.86 mm (3 m / (2 × 256)). Accordingly, the second arithmetic unit 33 calculates a value obtained by multiplying the output value L of the second timer 32 by the distance measurement resolution of 5.86 mm by 2
And the distance information φ can be calculated.

The distance calculator 14 calculates the distance D to the distance measurement target 2 from the approximate distance D 'and the distance information φ in the following manner. Here, while the resolution of the approximate distance D ′ is 0.75 m as described above, a half value of the maximum value of the distance information φ, that is, a half value of the maximum displacement distance is 1.5 m. It is twice. Therefore, when the half value of the distance information φ is 0.75 m or more, that is, when there is a remainder 0.75 m obtained by dividing the approximate distance D ′ by 1.5 m, the approximate distance D ′ For both the half values of the distance information φ, 0.75 m is counted twice. Therefore, the distance calculation unit 14 adjusts the resolution of the approximate distance D 'to 1.5 m, so that the first
A calculation process for truncating the least significant bit of the output value U (8 bits) of the timer 24 is performed. Specifically, the output value U (8
A value obtained by performing a logical AND operation on the binary number “01111110” and the 8-bit binary number “01111110” is defined as U ′, and the distance D to the distance measurement target 2 is calculated based on Equation 2.

[0025]

D = U ′ × 0.75 m + L × 5.86 mm + Δ

Here, Δ is a correction value for correcting an error due to an optical path difference between the reflected light R and the projected light F and an error associated with the time required for the photoelectric conversion processing in the modulation section 16 and the light receiving element 22. is there. When the least significant bit of the output value U (8 bits) is 1 and the distance information φ is 0.75 m or less, 0.75 m is added to the correction value Δ to obtain the distance D.
Is corrected. Conversely, when the least significant bit is 0 and the distance information φ is 0.75 m or more, the distance D is corrected by subtracting 0.75 m from the correction value Δ. Projection light F
And the reference signal component of the reflected light R slightly deviates beyond the boundary between 0 and 2π due to a measurement error or the like, and the output value L of the second timer 32 becomes 0 to 255 or 255 to 0 at worst.
The distance information φ calculated from the phase difference may have an error of up to 1.5 m at maximum, but due to the above correction, the measurement condition is poor, and a measurement error occurs in the phase difference. However, the maximum error of the distance D can be suppressed to 0.75 m or less. The addition / subtraction value for the correction value Δ may be arbitrarily selected in the range of 0.75 m to 1.5 m.

Further, in the second measuring section 13, the predetermined memory area in the second calculating section 33 in which the output value L of the second timer 32 is temporarily stored, because it is reset in advance 0 (8 bits) to the count at the start, when the light receiving state of the reflected light R is poor, not the reflected signal strength reference signal component from the second light receiving signal S ₂ sufficient to heterodyne detection is A valid output value L is not obtained from the second timer 32, and the value of the memory area remains 0. However, the first light receiving element 22
, The approximate distance D ′ can be calculated if the first light receiving signal S ₁ is detected at a level sufficient to stop the counting operation of the first timer 24. Therefore, it is necessary to confirm that the value of the memory area is not 0 before calculating Equation 2. When the state of receiving the reflected light R is poor and the value of the memory area is 0,
Since the resolution of the approximate distance D ′ has been reduced to 1.5 m, if the calculation of Equation 2 is performed as it is, the maximum measurement error becomes 1.5 m.
And the original output value U is used. As a result, the maximum error of the distance D can be suppressed to 0.75 m or less.

The first measuring unit 12, the second measuring unit 13, and the distance calculating unit 14 may be formed integrally with an integrated circuit or the like, or a part of an arithmetic circuit or Only the memory may be integrated and configured by a microcomputer or the like, and the specific hardware configuration of the circuit may be arbitrarily selected.

Next, a second embodiment will be described. <1> In the above embodiment, when the beam diameter of the reflected light R is small, the light receiving unit 11 is replaced by a beam splitter between the collimating lens 17 and the reflecting mirror 18 instead of using the condenser lens 23. 21 may be provided to guide the reflected light R to the first and second light receiving elements 22 and 23.

<2> In each of the above embodiments, the modulation method and modulation frequency of the light wave can be changed as appropriate. For example, the modulation signal C may be a waveform to which a DC bias is added as shown in FIG. Furthermore, as shown in FIG. 5, it is preferable that the modulation signal C is generated by adding and mixing the reference signal A and the pulse signal B in the modulation section 16. In addition, a specific configuration of each means may adopt a configuration other than the above description. In particular,
As the first and second light receiving elements 22 and 23, those having appropriate response characteristics and sensitivity in accordance with the respective frequencies of the reference signal A and the pulse signal B may be used. However, the present invention is not limited to this.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of an embodiment of a distance measuring apparatus according to the present invention.

FIG. 2 is a waveform diagram showing a modulation state of projection light in one embodiment of the distance measuring apparatus according to the present invention.

FIG. 3 is a schematic diagram showing an arrangement state of first and second light receiving elements as viewed from an incident direction of reflected light.

FIG. 4 is a waveform chart showing another embodiment of a modulation state of projection light.

FIG. 5 is a waveform chart showing another embodiment of the modulation state of the projection light.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Distance measuring device 2 Distance measuring object 10 Light projecting means 11 Light receiving means 12 First measuring unit 13 Second measuring unit 14 Distance calculating unit 22 First light receiving element 23 Second light receiving element F Projection light R Reflected light

Continued on the front page F term (reference) 2F065 AA06 DD03 FF31 GG04 JJ02 LL21 QQ25 5J084 AA05 AD01 AD02 BA04 BA36 BB02 BB21 CA03 CA22 CA27 CA31 CA49 DA01 DA09 EA01 EA04

Claims (3)

[Claims] 1. A light projecting means for projecting a light wave intensity-modulated by a modulation signal obtained by mixing a pulse signal having a constant period and a reference signal having a higher frequency than the pulse signal toward a distance measurement target, and the distance measurement Light receiving means for receiving light reflected from the object,
A first measurement unit that estimates a distance to the distance measurement target from a time difference between the projection light projected from the light projection unit and the reflected light, and a distance measurement target to the distance measurement target based on a phase difference between the projection light and the reflected light. A second measurement unit that calculates predetermined distance information, and a distance calculation unit that calculates a distance to the distance measurement target from the estimation result of the first measurement unit and the distance information of the second measurement unit. A distance device, wherein one of the light receiving means has two types of light receiving elements having slower response but higher light receiving sensitivity than the other, and is detected by the first light receiving element having slower response but higher light receiving sensitivity. A first light receiving signal is used by the first measuring unit, and a second light receiving signal detected by a second light receiving element, which is the other light receiving element, is used by the second measuring unit. apparatus. 2. The distance measuring apparatus according to claim 1, wherein one of the first light receiving element and the second light receiving element is arranged around the other. 3. The distance measuring apparatus according to claim 2, wherein said first light receiving element is arranged around said second light receiving element.