JPS60205303A - Optical measuring instrument for displacement - Google Patents

Abstract

PURPOSE:To enable stable and accurate measurement of displacement quantity by calculating digitally the peak-to-peak values of a pair of output signals from a semiconductor position detector and detecting and calculating the displacement quantity by using such values. CONSTITUTION:The light emitted from a semiconductor laser 2 is projected onto an object 4 to be measured and part of the light scattered by said object is detected by a semiconductor position detecting element 7. A pair of the output current signals are subjected to AC amplification 22a, 22b to signals V133, V234 which are alternately changed over at every one period of the timing signal 29 for lighting the laser 2 by a signal change-over device 23 and are inputted to a sample and hold circuit 24. The difference between the two digital signals obtd. when the laser 2 is lighted or put out and the peak-to-peak value V'1 and V'2 of the signals V133 and V234 are determined in an arithmetic processor 26. The calculation of (V'1-V'2)/(V'1+V'2) is made in the processor 26, by which the distance up to the light spot 5 on the object 4 is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical displacement measurement value +111 (4/') for non-contact measurement of the shape of an object to be measured.

[Prior art]

Conventionally, there has been a device of this type as shown in FIG. In FIG. 1, the drive circuit of the fll i4 light source, +2
1 is a light source and a semiconductor laser, (3) is a light projection lens that condenses the light from the semiconductor laser (2) and irradiates it, (4)
) is an object to be measured, (5) is a light spot projected onto the object to be measured (4), (6) is a light receiving lens that images the scattered light from the light spot (5) on a position detection element, (7) is a semiconductor device detection element (hereinafter abbreviated as PSD) which is a light receiving element;
(8a) (8b) are preamplifiers, (9a) (9b) are amplifiers, (10a) (10b) are rectifier circuits, (11a)
is the output signal Va, (llb) is the output signal Vb, (2) is the subtraction circuit, (2) is the addition circuit, 04 is the subtraction output signal Va
-Vb, (to) is the addition output signal Va+Vb.

019 is a division circuit, Oη is a division output signal (Va −Vb
)/ffa + Vb), (to) is the A/D converter, and 0 is the output signal of the digitized displacement measurement result.

FIGS. 2(a) and 2(b) are timing diagrams showing an example of control signals used in the device shown in FIG. is an enlarged view of the time axis.

Next, the operation will be explained. In FIG. 1, light emitted from a semiconductor laser (2) driven by a light source drive circuit ill is condensed by a light projecting lens (3), and is focused on the object to be measured (
4) Project a light spot (5) onto it. semiconductor laser 1
21, light emitting lens (3), light receiving lens +61 and PS
The optical system consisting of PSD (71) uses the principle of triangulation to determine the distance from the projection lens (3) to the light spot (5), so that the light focused on PSD (7) It is arranged to detect and measure the position of the received light image of the spot (6). At this time, P S D (7
), the position of the received light image of the light spot (6) is PSD
f7) Amplifying circuits (8a) each outputting a pair of output current signals.

(sb), (9a) and (9b) convert to voltage, amplify it, rectify it through rectifier circuits (10a) and (10b), and rectify it to form a pair of voltage signals Va(lla) and Vb.
(llb), it is given by the following formula, where l: the known value of the distance from the center to the edge of PSD(7) The displacement of the object (4), that is, the distance from the light projecting lens (3) to the light spot (5), is based on the arrangement of the optical system determined by J) and the two signals, VauJ, VbQθ. , the subtraction signal (Va −Vb )04 and the addition signal (Va+V
b) Add O12, (Va - Vb )/(Va + V
b), the divided output signal Oη can be obtained. Finally, Qη was digitized by an A/D converter (to) to obtain measurement result 01.

Since the conventional optical displacement meter is configured as described above, the output signal of the PSD (7), which has information on the distance to the object to be measured (4), must be rectified, and the offset of the circuit elements must be rectified. It is susceptible to negative effects such as voltage and temperature drift or noise, and furthermore, because it requires calculations using an analog division circuit, it is difficult to secure S/N and has drawbacks such as unstable measurement results. .

[Summary of the invention]

This invention was made to eliminate the drawbacks of the conventional ones as described above, and uses an AC amplifier to amplify the output signal of the light receiving element, and uses an arithmetic processor to digitally convert the peak-to-peak value of each output signal of the PSD. By using these peak-to-peak values to perform displacement detection calculations, it is possible to perform stable and accurate displacement measurement that is less susceptible to the effects of offset voltage and humidity drift that may occur in amplifier circuits, etc. The purpose is to provide an optical displacement meter that can

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 8th
In the figure, the same symbols as in Figure 1 indicate the same parts, (22a
), (22b) are AC amplifier circuits, ni) are signal switchers, ■
is a sample hold circuit, (2) is an A/D converter, (e) is an arithmetic processor, (c) is an output of the arithmetic processor (e), (2) is a timing pulse generation circuit, (2) is a semiconductor laser (2) ) is the lighting timing signal, (to) is the control signal for the signal switch (to), 0 or is the control signal for the sample and hold circuit (c), (2) is the A/D converter (e)
(to) is the output signal of the AC amplifier circuit (22a), ■ is the output signal of the AC amplifier circuit (22b), (to) is the output signal of the signal switching circuit, (to) is the sample hold circuit ( This is the output signal of c).

FIGS. 4(a) to 4(h) are timing charts showing an example of the temporal operation of each part of the apparatus shown in FIG. 8.

The lighting timing signal 4 for the semiconductor laser +21 shown in FIG. (d) of the same figure shows a control signal (7) for the signal switch (0) indicates switching to vI (to), and 1 indicates switching control to V2 (present). The figure (f) is
In the sample and hold control signal OI), 0 indicates sample and 1 indicates hold. Note that other parts in the same figure indicate their outputs using symbols corresponding to the symbols of each part in FIG.

Next, the details of the operation will be explained. In Fig. 8, the light emitted from the semiconductor laser (2) that is turned on in synchronization with the semiconductor laser turn-on timing signal passes through the projection lens (3) and is illuminated as a light spot on the object to be measured (4). (5), and a part of the scattered light is transmitted to the PS by the light receiving lens (6).
A pair of current signals imaged on D(7) and output from PSD(7) are eJTII! The amplifier (8a) (8b)
The voltage is converted and amplified by the AC amplifier (22a
), (22b) AC amplified signal Mn,
It will become V2. 2 signal vl (1, vI sardine is signal switch -
Accordingly, the sample and hold signals are alternately switched every cycle of the semiconductor laser lighting timing signal and input to the sample and hold signal. First, the sample hold ■ input is 41 j
To describe the operation when it is switched to tV+a, the sample hold
The semiconductor laser outputs the lighting timing signal (2
) is turned on in synchronization with V, and when the signal V, (to) has converged to a sufficiently stable state, it is sampled and held. A/D converter (c)
This sampled and held signal e is A/D converted and sent to an arithmetic processing unit. Similarly, when the semiconductor laser (2) is turned off, when the signal vlso has sufficiently stabilized and converged, it is sampled and held, A/D converted, and sent to the arithmetic processor. The calculation process sensor (e) calculates the difference between two digital signals obtained when the semiconductor laser 12) turns on and off, and calculates the peak-to-peak value VI/ of the signal V1 (to). Next, sample hold (
The peak-to-peak input of the signal v204 (ti V
Worth 2'. From the peak-to-peak values of the two signals obtained in this way, (vl"h')/(V+'10■')
The distance to the light spot (5) on the object to be measured (4) is obtained by performing the calculation in the arithmetic processor ().

In addition, in the embodiment, the sample hold circuits ◆, and r
Although one A/D converter) is shown, a plurality of these may be provided. In this case, effects such as faster sampling, simultaneous sampling, and omission of a signal switch can also be obtained.

Furthermore, in the above embodiment, a semiconductor laser (2
) is shown as a rectangular wave as the lighting timing signal 4 (7, an example of on/off control of lighting and extinguishing is shown). The amplified output of the output signal of PSD (7) is sampled in accordance with the timing of a certain change in the output intensity of the PSD (7), and the difference between the sampling data obtained at each timing is calculated to calculate the peak-to-peak signal. Even if it is regarded as a value and the same processing as in the above embodiment is performed, the same effect as in the above embodiment is obtained.

〔Effect of the invention〕

As described above, according to the present invention, the semiconductor device detection element (
・The output signal of the PSD was digitized by the A/D converter, the peak-to-peak values were calculated by the arithmetic processor, and the displacement detection calculation was performed using these values, so the output signal of the PSD It has the effect of being stable and highly accurate displacement measurement that is not easily affected by offset voltages and temperature drifts generated in amplifier circuits and other parts.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a conventional non-contact displacement measuring device.
FIG. 2 fa) (b) is a diagram showing an example of a drive signal for a semiconductor laser used in the device shown in FIG. 1, FIG. 8 is a block diagram showing a non-contact displacement measuring device according to an embodiment of the present invention,
FIG. 4 is a timing diagram showing an example of control signals used in the device of FIG. 8. In the figure, (2) is a semiconductor laser as a light source, (
3) is the light emitting lens, (4) is the object to be measured, (6; is the light receiving lens, (7) is the position detection element, (8a), (8b) is the front 81a width gauge, (22a) and (22b) are (2) is an A/D converter, (2) is an arithmetic processor, and (C) is a timing pulse generation circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts. Agent Masuo Oiwa

Claims (1)

[Claims] Utilizing the principle of ill triangulation, an optical system arranged to measure the distance to an object to be measured, a light source, a light receiving element as a position detection element, and position detection of the light receiving element. an AC amplifier that amplifies the signal; a signal switcher that switches the output signal of the AC amplifier and inputs it to the sample and hold circuit;
An A/D converter for A/D converting the output of the sample and hold circuit above.
A D converter, an arithmetic processor that processes the digitized signal, and a timing pulse generation circuit that supplies control i11 hals to the driving timing pulse of the light source, the signal switch, the sample hold circuit, and the A/D converter. An optical displacement measuring device comprising: The light receiving element 121 is a semiconductor device detecting element, which AC amplifies the output signal containing the two position information of the detecting element, performs data sampling and A/D conversion according to the timing of the output change of the light source, and converts these digital signals. From the converted multiple sampling data, 2
2. The optical displacement measuring device according to claim 1, wherein the peak-to-peak values V/ and %// of the two output signals are calculated by digitally calculating the respective peak-to-peak values V/ and %//. (3) 2 of the above semiconductor device detection element digitized
The peak-to-peak value V'l of the two output signals. V/, difference (V'+ -V'!) and sum (V',
10V'2) and (V'+ -V'! )/(V'l +
2. The optical displacement measuring device according to claim 1, wherein the optical displacement measuring device is configured to calculate the amount of change in distance to the object to be measured by digitally calculating V'2) in an arithmetic processor.