JPS5842411B2 - distance measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a distance measuring device for measuring the distance to an object to be measured by optical means, and its purpose is to adjust the light emitting means so that the amount of light received by the light receiving means is always constant. It is an object of the present invention to provide a distance measuring device capable of feedback controlling the amount of light projected, preventing fluctuations in distance measuring accuracy, simplifying the structure, and suppressing the adverse effects of ambient light.

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 to 4.

In FIG. 1, reference numeral 1 denotes a light projecting element as a light projecting means consisting of a light emitting diode, a laser generator, etc., which is driven by a pulse modulation circuit 2, which is a control means, to emit pulse modulated light.

Reference numeral 3 denotes a condensing optical system composed of a condenser lens, etc., and the pulse modulated light is projected onto the object to be measured 4 via this condensing optical system 3.

Reference numeral 5 denotes a semiconductor device detector (hereinafter abbreviated as PSD) as a light receiving means arranged in parallel with the light emitting element 1 at a predetermined interval, and a light receiving surface 5a of this device is provided with a pulse modulation device reflected by the object to be measured 4. The light is incident and imaged via the imaging optical system 6.

That is, the light projecting element 1 and the PSD 5 are arranged in a triangular manner with respect to the object to be measured 4, and therefore the PSD 5 directs the pulse modulated light reflected by the object to be measured 4 to the distance X from the object to be measured 4. The light is received at a light receiving point according to the

Here, the PSD 5 has the following functions.

In other words, when light is incident on the light-receiving surface 5a while being biased by the bias power source 7, the PSD 5 generates a photocurrent I having a value corresponding to the amount of incident light, and also generates a photocurrent I from the pair of electrodes A and B. Signal current processing, I, given by the following formulas, respectively:
B (however, +I, =I) is output as a position signal.

That is, as shown in Fig. 2, when the distance between electrodes A and B of PSD 5 is defined as the distance from L1 electrode A to the light receiving point, there is the following relationship, and therefore, the signal current ■6゜■8 makes the distance X (that is, the position of the light receiving point), and the distance X to the object to be measured 4 can be measured according to this distance X.

8 and 9 are light receiving circuits that output DC signal voltages vA and VB that monotonically increase in accordance with signal currents ① and ②8, respectively;
These have a configuration as shown in FIG.

Note that since the light receiving circuits 8 and 9 have the same configuration, only one of the light receiving circuits 8 is shown in FIG. By using the reference numerals in (g), illustration thereof will be omitted.

That is, in the light receiving circuit 8 shown in FIG. 3, 10a is a current input amplifier that receives a signal current, and its amplified output is sent to an AC amplifier 11a and a gate circuit 12 as a synchronizing means.
A is sequentially inputted to an integrating circuit 13a through the input circuit 13a, and an integrated output from the integrating circuit 13a forms a signal voltage 6.

Note that the gate circuit 12a receives an oscillation pulse P which is a synchronizing signal output from the pulse modulation circuit 2.

The configuration allows the signal to pass only when the signal is received.

On the other hand, 14 is the sum of the signal voltages ■6 and ■8, that is, "■yo+V
The adder calculates 8J, and the result of the calculation is sent to the pulse modulation circuit 2.

Here, the signal voltages ■e, ■8 are the signal currents ■e, ■8, respectively.
Since it increases monotonically with respect to ``■yo+V3J'', it also increases monotonically with respect to ``■□10I8J.

That is, "IA+■8" is the photocurrent ■ generated by PSD5.
Since the value is equal to the amount of light of the pulse modulated light that the PSD 5 receives, "■e+■8" also takes a value that corresponds to the amount of light that the PSD 5 receives.

The pulse modulation circuit 2 has a configuration as shown in FIG. 4.

In FIG. 4, reference numeral 15 denotes an error amplifier, which amplifies the difference between the calculation output "■Yo+■8" from the adder 14 and the reference voltage E8 to produce an error output voltage ■.

is sent to the voltage controlled oscillator 16.

In this case, the above error output voltage ■.

is designed to change in inverse proportion to rV, +V, and J.

The voltage control oscillator 16 receives the input voltage V.

An oscillation pulse P with a frequency that monotonically increases according to.

This outputs the following. Therefore, the frequency of the oscillation pulse P changes in inverse proportion to "■e+■8".

Further, as mentioned above, the oscillation pulse Po is given to the gate circuits 12a and 12b in the light receiving circuits 8 and 9, and is also given to the drive circuit 17, which is connected to the oscillation pulse Po. .

is amplified and the amplified output drives the light projecting element 1, thereby causing the light projecting element 1 to emit pulse modulated light.

Furthermore, in FIG. 1, 18 is a subtracter that calculates the difference between the signal voltages ■ and ■, that is, rV, -V8J, and 19 is a subtracter 18.
This is a distance calculation circuit as a calculation means for calculating the distance X to the object to be measured 4 based on the calculation result "vA-■8".

That is, "■yoichi■8" has a constant ratio relationship with the signal current "■yoichi■8" outputted corresponding to the position of the light receiving point of the PSD 5, and therefore, this "v - ■" Based on this, the distance X to the object to be measured 4 can be calculated.

In the above configuration, the pulse modulated light emitted from the light projecting element 1 and reflected by the object to be measured 4 is received at a light receiving point on the light receiving surface 5a of the PSD 5 corresponding to the distance X from the object to be measured 4. , PSD5 outputs signal currents (1) and (8) as position signals corresponding to such light receiving points.

In the light receiving circuit 8°9, the gate circuit 12a,
12b is an oscillation pulse P output at a timing synchronized with the pulse modulated light.

The amplified signals from the AC amplifiers 11a and 11b corresponding to the signal current (1) and (8) are passed through periodically, and the integration circuits 13a, 13b integrate the passed signals, resulting in the corresponding signal current. Continuous signal voltage ■ from the light receiving circuits 8 and 9.

vB is output respectively.

Then, the adder 14 calculates "VA+■8" and sends the result to the error amplifier 15 in the pulse modulation circuit 2, so the voltage control oscillator 16 calculates "VA+V8J".
(that is, a value corresponding to the amount of light received by the PSD 5), the oscillation pulse P whose frequency changes in inverse proportion to the amount of light received by the PSD 5.

Output.

Therefore, when the amount of light received by the PSD5 is greater than the reference value, in other words, when rv, +v, is greater than the reference voltage E8, the frequency of the oscillation pulse Po becomes lower; When the amount of received light is less than the reference value, the frequency of the oscillation pulse Po increases.

As a result, the oscillation pulse P.

So-called pulse number modulation (PNM) is applied to the light emitting element 1 driven by the light emitting element 1, so that the amount of light emitted by the light emitting element 1 decreases when the amount of light received by the PSD 5 becomes small, and
Feedback control is performed in the direction of increasing the amount of light received by D5 when it becomes small, and as a result, the pulse modulation circuit 2
The amount of light received is always maintained at a constant level.

Through the above operations, even if the distance X to the object to be measured 4 changes, the amount of light received by the PSD 5 is kept constant in response to the change, and the brightness at the pulse modulated light reflecting surface of the object to be measured 4 is maintained constant. 2. The amount of light received by the PSD 5 is kept constant regardless of the surface shape, the degree of inclination to the PSD 5, etc.

Therefore, the signal currents I, I, and the calculation results rV and V8J of the subtracter 18, which are the basis of distance measurement, always exhibit a constant relationship with the distance X from the object to be measured 4, which increases the accuracy of distance measurement. An excellent effect is obtained in that the distance does not vary regardless of the type of the object 4 to be measured and the distance from the object 4 to be measured.

Further, the light receiving circuits 8 and 9, the PSD 5, and the adder 14.
The operating level of the subtracter 18 and the like can also be kept substantially constant, and the dynamic range of these components can be made small, thereby simplifying the structure.

And, since the amount of light received by PSD5 is constant,
Due to the nature of the PSD 5, the photocurrent (2) generated by the PSD 5 is also constant, so that the influence of changes in the photocurrent (2) can be ignored during calculation in the distance calculation circuit 19.

That is, since there is no variation in the scale factor due to changes in the photocurrent (2), there is no need for calculations to normalize the signal currents I, , I, from the PSD 5.

Therefore, the distance calculation circuit 19 only needs to have the function of simply converting "■□-■8" into distance X, and from this point of view as well, the structure can be simplified.

Furthermore, since pulse modulated light is used in the optical system for distance measurement, the adverse effects of disturbance light can be suppressed as much as possible, thereby further stabilizing the accuracy of distance measurement.

Incidentally, in place of the pulse modulation circuit 2 and the light receiving circuits 8 and 9 in the above embodiment, a pulse modulation circuit 20 serving as a control means having the structure shown in FIG. 5 and a light receiving circuit 21 having the structure shown in FIG. 6 are applied, respectively. It's okay.

That is, in FIG. 5, 22 amplifies the difference between the calculation output rV+VJ from the adder 14 and the reference voltage Es to produce an error output voltage .
24 is an oscillation pulse P which is a synchronizing signal.

25 is a self-excited oscillation circuit that outputs an oscillation pulse P.

It is a transistor that is turned on only during the falling period of
This transistor 25 grounds the gate of FET 23 when it is on.

The drain and source of the FET 23 are connected between the power supply +■ and the ground terminal via the light emitting element 1 (in this case, a light emitting diode).

Such a pulse modulation circuit 20 has "V1+V2J=
The peak value of the current flowing through the light emitting element 1 is controlled so that E
5. Keep the amount of light received at a constant level.

Further, in FIG. 6, 26 is a current input amplifier receiving signal current ■A (or more), 27 is a variable gain AC amplifier, 28 is a gate circuit as a synchronizing means, 29 is an integrating circuit, and 30 is an error amplifier. The output of this error amplifier 30 is fed back to the variable gain AC amplifier 27 as a variable gain signal.

Even in the light receiving circuit 21 having such a configuration, a signal voltage V (or VB) having a predetermined ratio relationship with the signal current ■ (or ■B) is output from the error amplifier 30, and especially with this configuration, a dynamic It has the advantage of having a large range.

According to the present invention, as is clear from the above description, the light emitting means emits light so that the amount of light received by the light receiving means is always constant regardless of the distance to the object to be measured or the surface condition of the object to be measured. It is possible to provide a distance measuring device that can perform feedback control of the amount of light, prevent fluctuations in distance measurement accuracy, simplify the structure, and reduce the adverse effects of ambient light.

[Brief explanation of drawings]

1 to 4 relate to an embodiment of the present invention,
FIG. 1 is a diagram illustrating the overall configuration, FIG. 2 is a diagram illustrating the functions of the light receiving means, and FIGS. 3 and 4 are block diagrams showing different main parts. Further, FIGS. 5 and 6 are views corresponding to FIGS. 4 and 5, respectively, showing other embodiments of the present invention. In the figure, 1 is a light projecting element (light projecting means), 2 and 20 are pulse modulation circuits (control means), 4 is an object to be measured, 5 is a semiconductor device detector (light receiving means), 8.9 is a light receiving circuit, 12a, 12b
, 28 is a gate circuit (synchronization means), 16 is a voltage control oscillator, and 19 is a distance calculation circuit (calculation means).

Claims (1)

[Scope of Claims] 1. A light projecting means for emitting pulse modulated light onto an object to be measured; A light receiving means is provided to receive light at a light receiving point corresponding to a distance from the object to be measured, and outputs a position signal corresponding to the position of the light receiving point, and a distance to the object to be measured is calculated according to the position signal. a synchronizing means for supplying the position signal to the calculating means at a timing synchronized with the pulse modulated light; and a synchronizing means for feeding back the amount of light emitted by the light emitting means in accordance with the amount of the pulse modulated light received by the light receiving means. 1. A distance measuring device comprising: control means for controlling and maintaining the amount of light received by the light receiving means always at a constant level. 2. The control means has an oscillator that outputs an oscillation pulse of a frequency corresponding to the amount of light received by the light receiving means, controls the amount of light emitted by the light emitting means by modulating the number of pulses by the oscillation pulse, and transmits the oscillation pulse to the synchronizing means. 2. The distance measuring device according to claim 1, wherein the distance measuring device is configured to be used as a synchronization signal for.