JPS58129305A - Optical position detecting device - Google Patents

Abstract

PURPOSE:To make it possible to perform optical position detection, by inputting one of photocurrents from divided parts of a two division light detecting device into the same amplifier as the other amplifier through a delay circuit, sampling and holding the outputs at a delayed time interval, thereby eliminating the effect of the gain errors in the amplifier. CONSTITUTION:When pulse light 17 is inputted into a detector 16, the photocurrents I3 and I4 are generated and passed through preamplifiers 18 and 19. One output is inputted into a delay circuit 20 and delayed by a delay time T. Both outputs are amplified by a logarithmic amplifier 22 through an adder 21, and a peak value is detected by a peak value detecting circuit 23. The peak value is sampled and held in sample hold circuits 24 and 25 by sample hold signals E16 and E17 which are shifted by a delay time T, and a difference is obtained by a subtractor 28. The output E20 is sampled and held by a signal E21, which is synchronized with the sample hold signal E17, and the output is obtaind.

Description

[Detailed description of the invention] The present invention relates to a signal processing device for an optical position detection device.

FIG. 1 shows a system diagram of an example of an optical position detection device commonly used in the past as an optical position detection device using a two-part detector 1s, and FIG. 2 shows a waveform diagram thereof.The operation thereof will be described below. When Barne light 2 enters the detector 1, the current I 1m It due to the light is input to the respective preamplifiers 3 and 4 (here Ixm
t+ system, Es side is one system), its output El* E
m are each amplified by 6 to an amplifier. Furthermore, in order to obtain a dynamic range for the intensity of the input light, this is added to the logarithmic amplifier circuit 7.8 to obtain the output Es*E4. First, use the peak detection circuit 9.10 to widen the valve width (Es
, E6), a DC voltage E7°Is is obtained by the sample hold circuit 11.12. At this time, the gate signal of the sample and hold circuit is obtained by adding the output Es*E4 of each logarithmic amplifier circuit in an adder 13, and using the output Eat which is waveform-shaped in a monostable multipipe filter 14.The output of the sample and hold circuit E y e A subtractor 15 obtains the E sO difference.

The output E1o is Eto = K (E7-Ea).J) Eta is the position of the light, and K is a gain constant for the position of the light, which is determined by the gain of the subtractor. Here, amplifiers 3, 4 . These are called signal amplification sections for the logarithmic amplifier circuit 7.8 and the peak level detection circuit 9.10t.

In this signal processing device, assuming that the light is at the center of the detector and only the intensity P of the light changes, Figures 2 and 3 OA, B,
Considering the three points C, at the input level at point A, the gain G1 of the child thread and the gain G2 of the - system match, so the angular output EIO is 0. On the other hand, at point %B, Gl>02
Therefore, the angular output Eo produces an error output El. Similarly, at point 0, since Gl<G2, an error output EC is generated.

In this way, with conventional iron weight, if the gains of the two signal amplifiers do not match over the entire input light intensity range, an angular error output will occur even though the light is at the center of the detector. Put it away.

SUMMARY OF THE INVENTION An object of the present invention is to provide a signal processing device for an optical position detection device that eliminates angle detection errors due to mismatched gains of signal amplification sections.

In a signal processing device for an optical position detection device, a device eliminates an angle detection error t due to a mismatch in the gains of the signal amplification sections by using the same signal amplification section for both systems.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

A block diagram of an embodiment of the present invention is shown in FIG. 4, and a waveform diagram thereof is shown in FIG. 5. A case where the light is at the center and the intensity of the input light changes will be described.

The photocurrents In and In generated by the incidence of the pulsed light 17 on the detector 16 are amplified by the respective preamplifiers 18 and 19, and the output thereof is set as tEuJ1. - Output E of the system
Only 1g is passed through the delay circuit 201 and delayed by time T to be 11m. Pll and ELS are added by an adder 21 (Et4), and further passed through a logarithmic amplifier circuit 22 and a peak value detection circuit 23 to obtain an output Kxst. Etst+ type sample hold circuit 24 and type 1 sample hold circuit 2
Add to 5 at the same time. At that time, the gate signal gt- of the yarn sample and hold circuit 24 is obtained by waveform-shaping the output of the preamplifier 18 using a monostable multivibrator 26, and the gate signal gt- of the - system sample and hold circuit 25 is
7 uses a delay circuit output E1st whose waveform has been shaped by a monostable multivibrator 27, and adds the respective sample and hold circuit outputs E1s and Its to a subtracter 28 to obtain a difference output Ew. In addition to this 'Ewt sample hold circuit 29, an angle output Eat is obtained. The gate signal of the sample and hold circuit 29 uses Klyt--Ezl whose waveform has been shaped in addition to the monostable multivibrator 30.

In the above explanation, the amplifiers 5 and 6 shown in FIG. 1 are not shown, but this is because their influence is small, and in FIG. 4 they are included in the preamplifiers 18 and 19, respectively. Alternatively, one amplifier may be separately provided immediately after the adder 21. As described above, in the present invention, since the signal amplification section is shared with the child thread in one system, there is no angular error output due to gain mismatch as in the prior art.

As described above, in the present invention, by sharing the signal amplifying section with the + system and the - system, angular error output due to changes in the intensity of input light is eliminated. Further, circuit adjustment becomes easier because it is not necessary to match the two systems.

[Brief explanation of the drawing]

Figures 1 and 2 are a block diagram of a conventional signal processing device and its waveform diagram, and Figure 3 shows the DC voltage output of each unit when a gain mismatch occurs in the signal amplification section of the - system. FIG. 4 is a block diagram of the signal processing device of the present invention, and FIG. 5 is a diagram showing the waveform diagram of FIG. 4. 1.16...Detector, 2.17...Light, 3-6, 18°19...Amplifier, ? ,8,
22... Logarithmic amplifier, 9°10, 23...
...Peak value detection circuit, 11.12, 24°25.2
9... Sample hold circuit, 13.21...
...Adder, 15.28...Subtractor, 20
...Delay circuit. A B
CF2゜Mine Z times J times

Claims (1)

[Claims] a delay circuit for delaying one of the photocurrents from each divided portion of the photodetector divided into two for a predetermined time; an adder for adding the output of the delay circuit and the other photocurrent; an amplifier that amplifies the summed output; a peak value detection circuit that detects the peak value of the output of the amplifier; two sampling circuits that sample and hold this peak value using sampling pulses at the predetermined time intervals; and a circuit that samples the subtracter output with a pulse synchronized with the time-delayed sampling pulse.
-Characteristic optical position detection device.