JP3086339B2 - Distance measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art For example, Japanese Unexamined Utility Model Publication No. Sho 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 to receive light from the time of launch. There is disclosed a technique for measuring the distance to the object from the time required until the time point.

[0003]

By the way, time measurement?
As shown in FIG. 4, a signal processing method for converting distance from
During the time T from the light signal emission time to the light reception time,
The voltage is integrated, and the integrated voltage value V at the time of the light reception is converted into a distance.
And the optical signal generation as shown in FIG.
From the time of firing, for example, a pulse P with a constant pulse interval Occurs
And the number of the pulses P is counted,
It can be considered as a digital method that converts the distance from the number of contacts.

In this case, the former analog method has a relatively simple circuit configuration and is advantageous in cost, but when mounted on a car or the like, there is a possibility that the distance accuracy capability is inferior in terms of distance resolution. is there. That is, the distance measurement by car is 10
Since it is necessary to cover the distance in the range of 0 m, if the distance resolution is to be increased, the upper limit of the integrated voltage value V must be increased accordingly. However, in a car, when a battery voltage is considered, a high voltage cannot be used, so that it is difficult to increase the distance resolution as described above.

On the other hand, in the latter digital system which does not require a high voltage, the period of the pulse P is shortened as shown in FIG. If the number of generated pulses per time is increased, the number of counts is also increased, so that it is relatively easy to increase the distance resolution, which is suitable for mounting on an automobile or the like.
However, the shortening of the pulse interval inevitably requires an increase in the speed of signal processing, and the circuit components used must be high-speed signal-compatible components at high cost.

Accordingly, an object of the present invention is to provide a distance measuring device capable of suppressing an increase in cost while increasing 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 to when light reflected from the object is received by the light receiving means. A triangular wave generating means for generating a triangular wave pulse at a predetermined period from the emission time of the optical signal; a counting means for counting the number of triangular wave pulses from the emission time to the light receiving time of the optical signal; and the light receiving time Voltage value detecting means for detecting the voltage value of the triangular wave pulse, and a calculation for calculating the distance to the object by the distance conversion of the count number of the counting means and the voltage value of the voltage value detecting means. Means.

[0008]

According to the above arrangement, the distance is determined 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 improved by using the voltage value detecting 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.

In FIG. 1, the control circuit 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
By inputting a start pulse S ₁ shown in FIG. 3, the laser light is periodically emitted from the laser diode 1. Further, the start pulse S ₁ described above are also input to the measurement section 5, are adapted to the distance measurement operation from the firing point of the laser beam is started.

On the light receiving side, a light receiving diode 6 for receiving light reflected from an object is provided, and a light receiving signal S ₂
Is input to the light reception level detection circuit 8 via the light reception amplifier 7. When the light receiving level detecting circuit 8 detects the light receiving signal S ₂ , a stop pulse S ₃ shown in FIG. ₃ is output from the pulse generating circuit 9 to the measuring unit 5, and the measuring unit 5 outputs the stop light S _3. Calculates a distance corresponding to a time T (see FIG. 3) from the time of emission of the object to the time of reception of the reflected light, and displays the distance to the object corresponding to half of the distance.
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. and S ₁ and the stop pulse S ₃ is inputted. When the start pulse S ₁ thereto is inputted, the flip-flop 11 outputs an ON signal, also outputs the triangular wave pulses are driven triangular wave generating circuit 12 shown in FIG. 3 (a) at a predetermined period, flip-flop 11 outputs the OFF signal when the stop pulse S ₃ is input, the triangular wave generating circuit 1
2 is stopped.

In the measuring section 5, the triangular wave generating circuit 12 and the signal processing circuit 13 connected to the display section 10 are connected by two measuring systems.
That is, one of them is a digital system,
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 shown in FIG. The signal is sent to the signal processing circuit 13 described above.

On the other hand, the other measuring system is an analog system, and an integrating circuit including a capacitor 16 and an A / D
And a flip-flop 11 as 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 when it is 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 signals input from the two measurement systems, calculates the distance to the object by adding the two distance values, and displays the distance on the display unit 10.

That is, since the time t (67 _{nsec in} this embodiment) corresponding to the pulse interval of the differential signal is known from the differential output in FIG. 3B, the time t corresponds to the time t from the speed of light. You know the distance. Therefore, when the stop pulse S ₃ is input to the flip-flop 11 (the time when the reflected light is received), the number N of differential signals (five in 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 can be determined. 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 integral 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. since the time T from emission of the laser beam to the light receiving of the reflected light is the remaining time obtained by subtracting the time T _1, by converting the voltage value V ₁ of the reception time period, the distance corresponding to the time τ Can be calculated. That is, the peak value of the integral output as a 5V, and when the voltage value V ₁ of the the light receiving time of the and 3V, the digital output of the A / D converter 17 which shows the proportion of three-fifths of the time t Which corresponds to the 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 calculated thereby (to be 6 m).
Is added to the above-described 50 m, a distance corresponding to the time T is obtained as 56 m.
The half value (28 m) of the display unit 10 is defined as the distance to the object.
To be displayed.

As described above, the distance measurement from immediately before the light receiving time is performed by the distance measurement using the digital system, and the distance measurement from the immediately preceding to the light receiving time is performed by the distance measurement using the analog system. Is obtained, a 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 triangular wave pulse, and the upper limit of the integrated voltage is reduced, so that it can be easily mounted on an automobile or the like.

In the above distance measurement, in order to cause the capacitor 16 to perform an integrating operation from the time when the optical signal is emitted to the time when the light signal is received, an ON output of the flip-flop 11 is provided between the capacitor 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 it 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, a second switch 18b is connected 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 light receiving point,
The switch 18b is controlled to be turned off and turned on in response to light reception. In that case, the second switch 1
In 8b, when entered a stop pulse S ₃ to the flip-flop 11, since the integration start due to the capacitor 16, it is necessary to turn OFF the switch 18b simultaneously, is charged in the capacitor 16 at the reception time of the reflected light In order to integrate the charged electric charges, the above-mentioned ON timing must be delayed for a certain time Δt as shown in FIG. That is not ON Sasenebanara with a delay than when it entered the flip-flop 11 is stop pulse S _3. Therefore, a delay circuit 19 is provided between the flip-flop 11 and the switch 18b.

The delay circuit 19 includes a flip-flop 1
And inverting the first output inverter 20 to ON · OFF switch 18, a resistor 21 and capacitor 22 perform a delay operation, consists-connected diode 23 in parallel with the resistor 21, the start pulse S ₁ is flip When the input to the flip-flop 11 turns on the output of the flip-flop 11, the capacitor 22 is rapidly charged by the diode 23, and the switch 18 is turned off by the inverted output of the inverter 20. 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 is turned off.
To delay ON by a time Δt.

[0024]

As is apparent from the above description, according to the present invention, the distance measurement immediately before the light receiving point is performed by the distance measurement by the digital system, and the distance measurement from the immediately preceding to the light receiving point is performed by the distance measurement by the analog system. Distance measurement is performed, and the two distances are added to determine the distance corresponding to time.Therefore, accurate distance measurement with excellent distance resolution can be performed without shortening the generation cycle of the triangular wave pulse, and the circuit is a high-speed signal processing type. This eliminates the necessity of a configuration, and can avoid an increase in component costs. In addition, the upper limit of an integrated voltage for distance measurement by an analog system is reduced, and mounting on an automobile or the like can be easily performed.

[Brief description of the 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 measurement 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]

 REFERENCE SIGNS LIST 1 laser diode 5 measuring section 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

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01S ⁷ /48-7/51 G01S 17/00-17/95

Claims (1)

(57) [Claims] 1. An apparatus for measuring a distance to an object based on a time from when a light signal is emitted to the object by the light emitting means to when light reflected from the object is received by the light receiving means. Triangular wave generating means for generating a triangular wave pulse at a predetermined period from the time of emission, counting means for counting the number of triangular wave pulses from the time of emission of the optical signal to the time of light reception, and detecting the voltage value of the triangular wave pulse at the time of light reception Voltage value detecting means, and a calculating means for calculating the distance to the object by the distance conversion by converting each of the count value by the counting means and the voltage value by the voltage value detecting means to a distance. Distance measuring device.