JP2000214261A - Distance measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distance measuring device with high detection accuracy. SOLUTION: The distance measuring device has a constitution provided with a reference signal generator 1 outputting a reference signal of which periods of high level and low level are determined, a controller 4 controlling a light direction changing part 3 reflecting with a mirror a light signal from a light signal emitter 2 flashing while the reference signal is high level of and introducing it to the front of a vehicle, a phase difference detector 6 detecting the phase difference between reception signal output by a reflection signal receiver 5 having received the reflection light from a mirror and the reference signal and outputting the phase difference signal, a frequency divider 7 converting the reference signal to a sign wave signal, and a distance measuring part 9 detecting the voltage value of the output signal from the frequency divider 7 when the fall of the phase difference signal from the phase difference detector 6 is made sampling timing and calculating the distance by the digital voltage data from a sampling part 8 outputting the detected voltage value to the A/D converted digital voltage data and the signal from a level change detector 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device for calculating a distance from a phase difference or a time difference between a light wave transmitted from light or an electromagnetic wave and a reflected wave from a reflector.

[0002]

2. Description of the Related Art A conventional distance measuring device is disclosed in, for example,
As disclosed in JP-A-333336, a phase difference between a transmitted optical signal and a received optical signal is detected, charging is performed according to an RC time constant according to the phase difference, and based on the charged voltage value. , The distance to the reflector is calculated.

[0003]

However, in the conventional distance measuring device, charging is performed by the time constant of the resistor and the capacitor, and the distance is calculated from the voltage value. And the time constant changes due to the change in value due to temperature change. As a result,
There is a problem that detection accuracy is reduced. Therefore, the present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a distance measuring device with high detection accuracy.

[0004]

To achieve the above object, according to the first aspect of the present invention, there is provided a transmitting means for transmitting light or electromagnetic waves based on a reference signal from a reference transmitter,
Receiving means for receiving a reflected wave by a reflector, and inputting the reference signal, a signal synchronized with the reference signal, and
Signal conversion means for converting the signal into a signal which decreases or increases during one cycle; voltage level detection means for detecting a voltage level of the signal converted by the signal conversion means at the time of receiving the reflected wave; Distance calculating means for calculating the distance to the reflector based on the voltage level detected by the detecting means. According to the second aspect of the present invention, a transmitting means for transmitting light or an electromagnetic wave based on a reference signal from a reference transmitter, a receiving means for receiving a reflected wave by a reflector, and the reference signal are inputted, and the reference signal is inputted. A signal converting means for converting into a signal which is a synchronized signal and a combination of increasing and decreasing in one cycle, and a voltage level of the signal converted by the signal converting means at the time of receiving the reflected wave Voltage level detection means for detecting the signal, the signal converted by the signal conversion means, a determination means for determining whether the reduction period or the increase period,
Distance calculating means for calculating a distance to a reflector based on the voltage level detected by the voltage level detecting means at the time of receiving the reflected wave and the period determined by the determining means. .

[0005]

(Embodiment 1) Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of the first embodiment, FIG. 2 is a time chart of each signal output of the first embodiment, and FIG. 3 is a diagram showing a configuration of a light direction changing unit. Reference numeral 1 denotes a reference signal generator, which is shown in FIG.
As shown in (1), the reference signal is output in a period in which the high-level and low-level periods are predetermined. Specifically, a temperature-compensated oscillator, crystal oscillator, or the like is used. 2
Is an optical signal transmitting unit, which emits light while the reference signal is at a high level. Reference numeral 3 denotes a light direction changing unit, as shown in FIG. 3, which reflects the optical signal from the optical signal transmitting unit 2 by mirrors 11 and 12 and guides the signal to the front of the vehicle. At this time, by changing the X direction by the mirror 11 and changing the Y direction by the mirror 12, two-dimensional information in front of the vehicle can be detected by sweeping. Reference numeral 4 denotes a control unit of the light direction changing unit 3, which controls the angles of the mirrors 11 and 12 as described above, so that the optical signals 1 and 2 are output as shown in FIG.
1 (x direction, Y direction)... 1, n, 2, 1.
Sweep to m and n and repeat. Reference numeral 5 denotes a reflected signal receiving unit which receives the reflected light from the reflector and outputs a received signal as shown in FIG. Reference numeral 6 denotes a phase difference detection unit, which receives a signal received by the reflected signal reception unit 5 (FIG. 2).
(2)) and the reference signal from the reference signal generator 1 (FIG.
(1)) and outputs a phase difference signal as shown in FIG. 2 (3). Reference numeral 7 denotes a frequency divider, which converts the reference signal into a sine wave signal as shown in FIG. The frequency-divided waveform of the reference signal starts from the time when the reference signal shown in FIG. 2A is output, and one cycle ends when the reference signal is transmitted twice. Since the signal thus divided is formed from the reference signal, it is synchronized with the reference signal. Reference numeral 8 denotes a sampling unit, and the phase difference detection unit 6
The voltage value of the output signal from the frequency divider 7 is detected when the falling of the phase difference signal from the sampling timing is used as the sampling timing, and digital voltage data obtained by A / D converting the detected voltage value is output. Reference numeral 9 denotes a distance measurement unit that calculates a distance based on digital voltage data from the sampling unit 8 and a signal from a level change detection unit 10 described later. That is, since the signal and the amplitude of the signal of FIG. 2D are known in advance, for example, the detected voltage value is changed from the start of the waveform of FIG. The current voltage is calculated. Thereby, the phase difference and, consequently, the distance to the reflector can be calculated based on the time up to the calculated time point.

Next, the reason why the frequency-divided waveform is one cycle in two cycles of the reference signal will be described. Assuming that the reference signal and the divided waveform have the same period, when the phase is calculated from the voltage of the divided waveform at the time of the fall of the phase difference signal by an inverse trigonometric function or the like, the calculation result is two values that are 180 degrees out of phase. Comes out. At this time, the distance to the reflector in front is unknown,
It is not possible to determine which value corresponds to a short distance or a long distance. Therefore, by setting the divided waveform to two periods of the reference signal, it is possible to prevent two points of the same voltage as the voltage at the time of the fall of the phase difference signal. The level change detection unit 10 detects whether the divided waveform is changing from the high level to the low level or during the reverse period,
By the inverse trigonometric function according to each period (change),
The phase is detected from the voltage, and the distance to the target is determined.
The frequency-divided waveform is synchronized with a high-precision reference signal from a temperature-compensated oscillator or a crystal oscillator, and has a predetermined relationship between voltage and time. The influence of the variation of the time constant circuit is extremely reduced.

As described above, according to the present embodiment, a frequency-divided signal synchronized with the reference signal of the reference signal generator 1 using a high-precision signal is usually used, and the frequency is divided in one cycle. Since the distance is calculated based on the voltage level of the frequency-divided signal at the time of falling of the phase difference signal and the detection result of the level change detection unit 10, the signal is converted into a signal obtained by combining the increase and the subtraction. There is an effect that ranging can be performed. In the above-described embodiment, the sine wave is used. However, the sine wave is a signal synchronized with the reference signal, and
The signal is not limited to a sine wave as long as the signal decreases and increases during one cycle. Further, the signal may be a signal synchronized with the reference signal and may be a signal that is reduced or increased in one cycle. In this case, since the slash and increase are not combined in one cycle, the level change detection unit 10 is not required, so that the configuration can be simplified.

(Embodiment 2) Next, Embodiment 2 according to the present invention will be described with reference to FIGS. The first embodiment is different from the first embodiment in that a control unit 21 for generating and outputting a pulse signal from the reference signal from the reference signal generation unit 1 is added, and a pulse signal is used instead of the optical signal transmission unit 2 in the first embodiment. The transmitting unit 22 is different from the first embodiment only in that a voltage comparing unit 23 is provided instead of the phase difference detecting unit 6 and a sampling unit 24 is different.
The same reference numerals are given and the description is omitted, and only the changed points will be described below.

First, the control unit 21 detects the rise of the reference signal and outputs a pulse-like transmission signal having a predetermined time width as shown in FIG. Although a slight time delay occurs between the output of the reference signal and the output of the transmission signal, it is omitted in the figure. Then, the pulse signal sending unit 22
A pulsed optical signal is output to the optical direction changing unit 3 based on a transmission signal from the control unit 21. Voltage comparator 23 compares the voltage level of the received signal received by reflected signal receiver 5 with a threshold. Then, the sampling unit 24
A voltage value of a frequency-divided waveform, which is an output signal from the frequency divider 7 at the time when a received signal equal to or larger than the threshold value is detected, is detected.
The digital voltage data subjected to the / D conversion is output to the distance measuring unit 9.

As described above, in this embodiment, in addition to the effect of the first embodiment, since the reference signal is converted into a pulse-like transmission signal, the instantaneous energy output as an optical signal is increased. And the measurable distance can be increased.

[0011]

As described above, according to the present invention, usually,
It is a frequency-divided signal synchronized with a reference signal transmitted by a reference transmitter using a high-precision one, and is converted into a signal that increases or decreases in one cycle. Since the distance is calculated based on the voltage level of the frequency-divided signal, there is an effect that distance measurement with high detection accuracy can be performed. Also, instead of converting to a signal that increases or decreases during one cycle, the signal is converted to a signal that increases or decreases during one cycle, and the distance is calculated when the phase difference signal falls. By using the change state of the voltage level of the divided signal in addition to the voltage level of the divided signal, there is an effect that distance measurement with high detection accuracy can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of Embodiment 1 of the present invention.

FIG. 2 is a time chart of each signal output of the first embodiment.

FIG. 3 is a diagram illustrating a configuration of a light direction changing unit.

FIG. 4 is a diagram showing an image of two-dimensional distance measurement.

FIG. 5 is a block diagram showing a configuration of a second embodiment.

FIG. 6 is a time chart of each signal output according to the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reference signal generation part 2 Optical signal transmission part 3 Light direction change part 4 Control part 5 Reflection signal reception part 6 Phase difference detection part 7 Frequency division part 8 Sampling part 9 Distance measurement part 10 Level change detection part 11 Mirror 12 Mirror 21 Control Unit 22 pulse signal sending unit 23 voltage comparing unit 24 sampling unit

Claims (2)

[Claims] 1. A transmitting means for transmitting light or electromagnetic waves based on a reference signal from a reference transmitter, a receiving means for receiving a reflected wave by a reflector, a signal synchronized with the reference signal And a signal conversion means for converting the signal into a signal which decreases or increases during one cycle, and a voltage level detection which detects a voltage level of the signal converted by the signal conversion means at the time of receiving the reflected wave. And a distance calculating means for calculating a distance to the reflector based on the voltage level detected by the voltage level detecting means. 2. A transmitting means for transmitting light or an electromagnetic wave based on a reference signal from a reference transmitter, a receiving means for receiving a reflected wave by a reflector, a signal synchronized with the reference signal And signal conversion means for converting the signal into a signal obtained by combining increase and decrease in one cycle, and detecting a voltage level of the signal converted by the signal conversion means at the time of receiving the reflected wave. Voltage level detecting means; determining means for determining whether the signal converted by the signal converting means is a slashing period or a slashing period; and detection by the voltage level detecting means at the time of receiving a reflected wave. A distance calculating unit that calculates a distance to the reflector based on the measured voltage level and a period determined by the determining unit.