JPH0618666A - Distance measuring apparatus - Google Patents

Abstract

PURPOSE:To achieve higher distance resolutions while suppressing a rise in cost in an apparatus which measures a distance to an object from time between the emitting of a light signal to the object and the reception of the reflected light. CONSTITUTION:The number of angular wave pulses which are outputted by an angular wave generation circuit 12 from the moment of emitting a light signal is counted with a counter circuit 15 through a differentiation circuit 14 while the angular wave pulses are integrated with a capacitor 16 to translate the counts to the moment of receiving the light signal with a signal processing 13 into a distance. An integrated voltage value of the angular wave pulses at the moment of receiving the light signal is translated to a distance. Both the translated distance values are added up while being halved to calculates an actual distance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for measuring a distance to an object using an optical signal such as laser light.

[0002]

2. Description of the Related Art For example, Japanese Utility Model Laid-Open No. 62-163780 discloses a laser radar device for a vehicle, which emits an optical signal toward an object in front of the vehicle and receives the reflected light so that the light is received from the time of emission. A technique for measuring the distance to the object from the time required until the time point is disclosed.

[0003]

By the way, is it time measurement?
As a signal processing method for converting the distance from the
During the time T from the time when the optical signal is emitted to the time when the light is received,
The voltage is integrated, and the integrated voltage value V at the time of receiving light is converted to distance.
Analog system and the optical signal generation described above as shown in FIG.
From the time of shooting, for example, a pulse P with a constant pulse interval Occurs
And counting the number of the pulses P,
A digital method in which the distance is converted from the number of points is considered.

In this case, the former analog system has a relatively simple circuit structure and is advantageous in terms of cost, but when mounted on an automobile or the like, there is a possibility that the distance accuracy is inferior in terms of distance resolution. is there. That is, the distance measurement in a car is 10
Since it is necessary to cover the distance in the range of 0 m, in order to improve the distance resolution, the upper limit value of the integrated voltage value V must be increased correspondingly. However, since high voltage cannot be used in an automobile considering the battery voltage, it is difficult to improve the distance resolution as described above.

On the other hand, in the latter digital method which does not require a high voltage, the pulse generating means is made to have a high frequency so that the interval between the above-mentioned pulses P is short and constant as shown in FIG. 5 (b). If the number of pulses generated per time is increased, the number of counts also increases, so that the distance resolution can be increased relatively easily, which is suitable for mounting on an automobile or the like.
However, the shortening of the pulse interval inevitably requires high-speed signal processing, and the circuit components to be used also have to use high-cost high-speed signal compatible components.

Therefore, an object of the present invention is to provide a distance measuring device capable of suppressing an increase in cost while improving the distance resolution.

[0007]

That is, according to the present invention, the distance to an object is measured by the time from when a light signal is emitted to the object by the light emitting means until the reflected light from the object is received by the light receiving means. The device is a device for generating a triangular wave pulse in a predetermined cycle from the emission time point of the optical signal, a counting means for counting the number of triangular wave pulses from the emission time point of the optical signal to the reception time point, and the reception time point The voltage value detecting means for detecting the voltage value of the triangular wave pulse, the calculation of calculating the distance to the object by converting the count value of the counting means and the voltage value of the voltage value detecting means into distances. And means.

[0008]

According to the above construction, the distance is controlled by the counting means as a digital processing circuit for counting the number of triangular wave pulses and the voltage value detecting means as an analog processing circuit for detecting the voltage value of the triangular wave pulse at the time of light reception. Since the measurement is performed, the distance resolution can be increased by using the voltage value detection means together without shortening the cycle of the triangular wave panel.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

The control circuit shown in FIG. 1 includes a laser diode 1 on the light emitting side, a drive circuit 2 for driving the laser diode 1, and a high voltage generation circuit 3 for supplying a high voltage to the drive circuit 2. Light emission controller 4 in drive circuit 2
3 to the start pulse S ₁ shown in FIG. 3, the laser light is periodically emitted from the laser diode 1. The start pulse S ₁ is also input to the measuring unit 5 so that the distance measuring operation is started from the time when the laser light is emitted.

On the other hand, on the light receiving side, a light receiving diode 6 for receiving the reflected light from the object is provided, and its light receiving signal S ₂
Is inputted to the light receiving level detecting circuit 8 through the light receiving amplifier 7. Then, when the received light level detection circuit 8 detects the received light signal S ₂ , the pulse generation circuit 9 outputs the stop pulse S ₃ shown in FIG. The distance corresponding to the time T (see FIG. 3) from the point of time when the light is emitted to the time when the reflected light is received is calculated, and the distance to the object corresponding to half the distance is displayed on the display unit 1.
Display at 0.

In this case, the measuring section 5 is provided with a flip-flop 11 and a triangular wave generating circuit 12 as shown in FIG. 2, and the flip-flop 11 and the triangular wave generating circuit 12 are respectively provided with the above-mentioned start pulse. S ₁ and stop pulse S ₃ are input. Then, when the start pulse S ₁ is input to these, the flip-flop 11 outputs an ON signal, and the triangular wave generating circuit 12 is driven to output the triangular wave pulse shown in FIG. When the stop pulse S ₃ is input, the flip-flop 11 outputs an OFF signal, and the triangular wave generation circuit 1
2 is configured to be stopped.

Further, in the above-mentioned measuring section 5, the triangular wave generating circuit 12 and the signal processing circuit 13 connected to the above-mentioned display section 10 are connected by two measuring systems.
That is, one of them is a digital system, and the differentiation circuit 14
And a counter circuit 15. The triangular wave pulse output from the triangular wave generating circuit 12 is differentiated by the differentiating circuit 14 into a pulse signal having a constant pulse interval time t of (b), and the differential signal is counted by the counter circuit 15. Is sent to the signal processing circuit 13 described above.

On the other hand, the other measurement system is an analog system, and has an integrating circuit composed of the capacitor 16 and an A / D.
The converter 17 and the flip-flop 11 described above.
By starting to as from the time of the start pulse S ₁ is entered in (g) in FIG. 3 the integration of the triangular wave pulse, a stop pulse S ₃ the flip-flop 1
The voltage value of the triangular wave pulse at the time of being input to 1 is taken out as an integrated signal, digitized by the A / D converter 17, and sent to the signal processing circuit 13.

The signal processing circuit 13 performs distance conversion from the signals input from the two measuring systems, adds the two distance numerical values to calculate the distance to the object, and displays it on the display unit 10.

That is, since the time t corresponding to the pulse interval of the differential signal (67 _{nsec in} this embodiment) is known from the differential output of FIG. 3B, it corresponds to the time t from the speed of light. I know the distance. Therefore, when the stop pulse S ₃ is input to the flip-flop 11 (at the time of receiving the reflected light), the differential signal number N (5 in the case of FIG. 3) counted by the counter circuit 15 is multiplied by this distance, The distance to the time T ₁ (see FIG. 3) until the last differential signal is counted is known. For example, time t
When (67 _nsec ) corresponds to a distance of 10 m, T ₁ = t ×
N can be converted to a distance of 50 m.

On the other hand, the voltage value V ₁ of the integrated output of the triangular wave pulse at the time when the stop pulse S ₃ is input to the flip-flop 11 corresponds to the time τ as is apparent from FIG. 3, and this time τ is Since the remaining time is obtained by subtracting the time T ₁ from the time T from the emission of the laser light to the reception of the reflected light, the voltage value V ₁ at the time of the light reception is time-converted to obtain the distance corresponding to the time τ. Can be calculated. That is, when the peak value of the integrated output is 5 V and the voltage value V ₁ at the time of receiving the light is 3 V, the digital output of the A / D converter 17 shows a ratio of 3/5 of the time t. And corresponds to time τ. Therefore, the signal processing circuit calculates the distance by the following equation (1).

Distance = t × (3/5) × 10 (Equation 1) Therefore, the distance thus calculated (6 m)
Is added to the above 50 m, the distance corresponding to the time T is obtained as 56 m.
The half value (28 m) of the
To display.

In this way, the distance from the time immediately before the light reception time is measured by the distance measurement by the digital system, and the distance from the time immediately before the light reception time is measured by the distance measurement by the analog system. Since the distance corresponding to is calculated, precise distance measurement with excellent distance resolution can be performed without shortening the triangular wave pulse interval in the triangular wave generation circuit 12. Therefore, it is not necessary to configure the measurement circuit of a high-speed signal processing type, and it is possible to avoid an increase in cost.

Moreover, the distance measurement by the analog system is
It suffices to perform integration for one pulse of the triangular wave pulse, and the upper limit of the integrated voltage becomes low, so that it can be easily mounted on an automobile or the like.

By the way, in the above distance measurement, in order to cause the condenser 16 to perform an integrating operation from the emission point of the optical signal to the reception point, the ON output of the flip-flop 11 is provided between the condenser 16 and the triangular wave generating circuit 9. A first switch 18a that is turned on (in other words, from the time when the optical signal is emitted to the time when the light is received) is provided.

In order to discharge the electric charge charged in the capacitor 16 after the distance measurement and prepare for the next distance measurement, the second switch 18b is arranged in parallel with the capacitor 16 and between one end of the capacitor 16 and the ground. Is provided,
By the output of the flip-flop 11, until the time of receiving light,
The switch 18b is turned off, and is controlled to be turned on with the reception of light. In that case, this second switch 1
In 8b, when the stop pulse S ₃ is input to the flip-flop 11, it is necessary to turn off the switch 18b at the same time because the integration is started by the capacitor 16, but the capacitor 16 is charged when the reflected light is received. In order to integrate the accumulated charge, the above ON timing must be delayed by a slight time Δt as shown in FIG. That is, the flip-flop 11 must be turned on later than when the stop pulse S ₃ is input. Therefore, the delay circuit 19 is provided between the flip-flop 11 and the switch 18b.

The delay circuit 19 includes a flip-flop 1
An inverter 20 for inverting the output of 1 to turn on / off the switch 18, a resistor 21 and a capacitor 22 for performing a delay operation, and a diode 23 connected in parallel to the resistor 21 are provided, and the start pulse S ₁ is a flip-flop. When the output of the flip-flop 11 is input to the flip-flop 11 and turned on, the diode 23 rapidly charges the capacitor 22, and the inverted output of the inverter 20 turns off the switch 18. In addition, when the stop pulse S ₃ is input to the flip-flop 11 and the output of the flip-flop 11 is turned off, the charge of the capacitor 22 is slowly discharged, and the switch 18
ON delays by the time Δt.

[0024]

As is apparent from the above description, according to the present invention, the distance measurement up to the time immediately before the light reception time is performed by the distance measurement by the digital system, and the distance measurement from the time immediately before the light reception time is performed by the distance measurement by the analog system. Since distance measurement is performed and both distances are added to obtain the distance corresponding to time, precise distance measurement with excellent distance resolution can be performed without shortening the triangular wave pulse generation cycle, and the circuit is of high-speed signal processing type. Since it is not necessary to configure the device as one, the cost of parts can be prevented from increasing, and the upper limit of the integrated voltage for distance measurement by the analog system can be lowered, so that the device can be easily mounted on an automobile or the like.

[Brief description of drawings]

FIG. 1 is a control circuit diagram of a distance measuring device according to the present invention.

FIG. 2 is a circuit diagram of a measuring unit in the control circuit.

FIG. 3 is a time chart of the control circuit.

FIG. 4 is an explanatory diagram of distance measurement by conventional analog processing.

FIG. 5 is an explanatory diagram of distance measurement by conventional digital processing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 laser diode 5 measuring part 6 light receiving diode 12 triangular wave generating circuit 13 signal processing circuit 14 differentiating circuit 15 counting circuit 16 capacitor 17 A / D converter

Claims (1)

[Claims] 1. A device for measuring the distance to an object by the time from the time when an optical signal is emitted to the object by the light emitting means to the time when the reflected light from the object is received by the light receiving means. Triangular wave generating means for generating a triangular wave pulse at a predetermined cycle from the emission time point, counting means for counting the number of triangular wave pulses from the emission time point of the optical signal to the light reception time point, and detecting the voltage value of the triangular wave pulse at the light reception time point A voltage value detecting means; and a calculating means for calculating a distance to the object by converting the count number obtained by the counting means and the voltage value obtained by the voltage value detecting means into distances, respectively. Distance measuring device.