JPH03293581A - Range finder - Google Patents

Abstract

PURPOSE:To simplify and miniaturize constitution by comparing the timing of the rising of the receiving signal due to the reflected light from an object to be measured with that of the falling of the control pulse signal based on a drive pulse signal. CONSTITUTION:The light emitting element 4 of a drive circuit 3 is driven in synchronous relation to the drive signal A outputted from a pulse generating circuit 2 to emit light. A photodetector 6 turns current output ON/OFF corresponding to the presence of incident light by the incidence of the reflected light from an object 5 of the light signal of the element 4 and the current output is converted to a voltage level to be amplified by an amplifier 7 and the output thereof is binarized by a comparator 8. Further, the control pulse signal B outputted from the signal A corresponding to the set resistance value of an external variable resistor circuit 9 by a multivibrator 10 and the signal C from the comparator 8 are operated by an operation circuit 11 to output a signal D and a multivibrator 13 outputs judgement output E of a high or low level on the basis of the signal D. By this method, it is judged whether the distance up to the object 5 is larger than the judgment reference distance prescribed on the basis of the resistance value of the circuit 9.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a distance measuring device that measures distance by detecting a phase difference between a generated optical signal and an optical signal reflected from a distance measurement target.

<Prior Art> In a conventional distance measuring device, an optical signal synchronized with a pulsed drive signal is projected onto an object, and the reflected light is input and waveform-shaped to obtain a received signal.

Then, based on the drive signal and the received signal, a pulse signal having a pulse width is generated without corresponding to the phase difference between them, and by measuring this pulse width, the distance to the distance measurement target is measured.

<Problems to be Solved by the Invention> In order to measure the pulse width of the above pulse signal, a counting pulse signal with a frequency higher than the frequency of this pulse signal is generated, and the pulse signal is generated during a period corresponding to the pulse width. A technique has been adopted in which the number of pulse signals for counting is measured using a counting circuit or the like. Such conventional technology requires a circuit that generates a high-frequency pulse signal for counting,
The above-mentioned counting circuit and the like are required, resulting in a problem that the circuit configuration becomes larger and more complicated, and the device also becomes larger.

This invention was made to solve the above-mentioned problems, and aims to provide a distance measuring device with a simplified configuration and a reduced size.

<Means for Solving the Problems> The distance measuring device according to the present invention includes a drive pulse signal generating means for generating a drive pulse signal with a predetermined signal period, and a drive pulse signal synchronized with the drive pulse signal from the drive pulse signal generating means. an optical signal generating means for generating an optical signal; a receiving means for inputting the reflected light from the distance measurement target of the optical signal from the optical signal generating means to generate and output a binary received signal; and the driving pulse. control pulse signal generating means for generating a control pulse signal having the same signal period as the driving pulse signal and a pulse width corresponding to the determination reference distance based on the driving pulse signal from the signal generating means; and control from the reference pulse signal generating means. and determining means for comparing the fall timing of the pulse signal and the rise timing of the received signal from the receiving means and outputting a determination result as to whether the distance to the distance measurement target is greater than the determination reference distance. It is a feature.

<Operation> A received signal is obtained by generating an optical signal synchronized with a drive pulse signal, inputting the reflected light from the object to be measured and converting it into a binary value. If the rising timing of this received signal is earlier than the falling timing of the control pulse signal,
The distance to the distance measurement target is determined to be smaller than the determination reference distance, and on the other hand, if the rise timing of the received signal is later than the fall timing of the control pulse signal, the distance to the distance measurement target is determined to be greater than the determination reference distance. .

<Embodiment> FIG. 1 shows the electrical configuration of a distance measuring device 1 according to an embodiment of the present invention.

This distance measuring device 1 includes a pulse generating circuit 2 and outputs a drive signal A having a signal period of TI and a pulse width of Wl. The drive signal A is input to a drive circuit 3, and a light emitting element 4 such as a light emitting diode is driven to emit light in synchronization with the drive signal A.

The optical signal from the light emitting element 4 is reflected by the object 5, and the reflected light enters a light receiving element 6 such as a photodiode. The current output from the light receiving element 6 is turned on and off depending on the presence or absence of incident light, and the amplifier 7 converts the current value into a voltage level, and the voltage level is amplified. The output of amplifier 7 is input to comparator 8 and binarized.

The drive signal A from the pulse generating circuit 2 is input to a monostable multivibrator 10 to which a variable resistance circuit 9 is externally attached. This multivibrator 10 outputs a control pulse signal B whose pulse width W2 changes in accordance with the set resistance value VR of the variable resistance circuit 9. The control pulse signal B and the received signal C output from the comparison circuit 8 are input to an arithmetic circuit 11 that performs an AND operation.

The output signal from the arithmetic circuit 11 is input to a multivibrator 13 to which a fixed resistor I2 is externally attached. This multivibrator 13 generates and outputs a determination output E having a pulse width W3 corresponding to the resistance value R of the fixed resistor 12. In this embodiment, as will be described later, the judgment output E of the multivibrator 13 is fixed at a high level or a low level, and the distance to the object 5 is determined by the variable resistance circuit 9 depending on which level of output is obtained. resistance value VR
Determine whether the distance is greater than the determination reference distance defined by .

FIG. 2 is a time chart explaining the operation of this embodiment.

The drive pulse signal A in FIG. 2(1) drives the light emitting element 4 to emit light with this signal waveform, and also drives the multivibrator 1.
0, and outputs the control pulse signal B shown in FIG. 2 (2) synchronized with the rising timing of this signal. On the other hand, the received signal C shown in FIG. 2(3) output from the comparator 8 has a phase difference δ with respect to the drive pulse signal A corresponding to the distance L1 to the object 5. The larger this phase difference δ is, the further away the object 5 is.

The arithmetic circuit 11 performs an AND operation between the control pulse signal B and the received signal C to obtain the output signal shown in FIG. 2 (4). The multivibrator 13 is set so that the pulse width W3 of the judgment output E is longer than the signal period T1 of the drive pulse signal A when the level of the output signal is "1". When the output signal level is "1", the judgment output E of the multivibrator 13 is at a high level, and the output signal level of the arithmetic circuit 11 is "1".
0", each is fixed at a low level.

That is, when the phase difference δ of the received signal C becomes large and the received signal C rises after the fall of the control pulse signal B (the state shown by the broken line in FIG. 2 (3)), the arithmetic circuit 11
The output signal E does not appear as a pulse waveform, and the judgment output E
is fixed at low level. On the other hand, as the phase difference δ becomes smaller, the received signal C becomes smaller before the control pulse signal B falls.
When E rises, the output signal of the arithmetic circuit 11 appears as a pulse waveform, and the judgment output E is fixed at a high level.

If the signal level of the judgment output E is detected in this way,
It can be easily determined whether the distance L1 to the object 5 is greater than the determination reference distance determined by the resistance value VR.

In this embodiment, distance can be measured without adding a complicated circuit as described in the section of the prior art, and the configuration can be simplified and miniaturized compared to the prior art. Further, the resistance value VR can be adjusted by the variable resistance circuit 9, and therefore, the criterion for determining the distance to the object 5 can be arbitrarily set by changing the resistance value VR.

FIG. 3 shows the electrical configuration of a distance measuring device 1a according to another embodiment of the invention. This distance measuring device 1a has a similar structure to that of the previous embodiment, and corresponding parts are given the same reference numerals.

The structural features of this embodiment include a basic oscillation circuit 15 that outputs a sine waveform analog signal in place of the pulse generating circuit 2 of the previous embodiment, and a local oscillation circuit 16 that outputs a sine waveform analog signal. It is at the point that I have set. That is, this embodiment includes a configuration that improves distance measurement accuracy when the phase difference δ in the first embodiment is relatively small.

The oscillation output from the basic oscillation circuit 15 and the output from the amplifier 7 based on the reflected light from the object 5 are each output from the mixer 1.
After being multiplied by the local oscillation signal in step 7.18, the signal is passed through a low-pass filter 19.20 to obtain a beat signal. The frequency of this beat signal is lowered, for example, from one to several tenths of that of the oscillation output from the basic oscillation circuit 15 and the output from the amplifier 7. This beat signal is binarized by comparators 21 and 22 to obtain signals equivalent to the drive signal A and reception signal C in the first embodiment, and the multivibrators 10 and 13 and the arithmetic circuit 11
A distance determination operation similar to that of the first embodiment is executed.

Figure 4 shows the signal waveforms of each part in this example.
This embodiment is almost the same as the embodiment described above, and its explanation will be omitted here.

<Effects of the Invention> As described above, the present invention generates a reception signal by inputting the reflected light from the distance measurement target of the optical signal generated by the drive signal, and generates the reception signal based on the rise timing of the reception signal and the drive pulse signal. Since the falling timing of the generated control pulse signal is compared to determine whether the distance to the distance measurement target is greater than the determination reference distance, the distance measurement method has a simplified and compact configuration. This has the effect of realizing a measuring device.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a distance measuring device according to an embodiment of the present invention, FIG. 2 is a time chart showing the operation of the embodiment of FIG. 1, and FIG. 3 is a block diagram of another embodiment of the present invention. Fourth
The figure is a time chart showing the operation of the embodiment of FIG. 1.18... Distance measuring device 2... Pulse generating circuit 4... Light emitting element 6... Light receiving element 8,
2L 22... Comparator 10, 13... Multivibrator 11... Arithmetic circuit

Claims (1)

[Scope of Claims] Drive pulse signal generation means for generating a drive pulse signal with a predetermined signal cycle; optical signal generation means for generating an optical signal synchronized with the drive pulse signal from the drive pulse signal generation means; and an optical signal. a receiving means that inputs the reflected light from the distance measuring object of the optical signal from the generating means, generates and outputs a binarized received signal; and a driving pulse signal based on the driving pulse signal from the driving pulse signal generating means. a control pulse signal generation means for generating a control pulse signal having the same signal period as the reference pulse width and a pulse width corresponding to the determination reference distance; and a falling timing of the control pulse signal from the reference pulse signal generation means and a reception signal from the reception means. and determining means for outputting a determination result as to whether or not the distance to the object to be measured is greater than the determination reference distance by comparing the rising timing of the distance measuring device.