JPS626104A - Dimension measuring instrument by light - Google Patents

Abstract

PURPOSE:To erase a measuring error by dividing into two an output of a photodetector, which has been condensed, when an object to be measured exists in an optical path of parallel scanning rays, and when said object does not exist, and comparing a value which has been added by sample holding, and the output of the photodetector. CONSTITUTION:Parallel scanning rays 1 are condensed by a lens 3, and an output of a photodetector 4 is divided into two by ad dividing device 11. In this state, an output V of the time when an object to be measured 2 does not exist s divided into two and V/2 is sample-held 12 by a signal 17. Also, an output V0 of the time when the object to be measured 2 exists is divided into two and V0/2 is sample-held 13 by a signal 18. By adding both sample values, V1=(V-V0) is derived. Next, the output V of the photodetector 4 is compared with the output V1 by a comparator 15, and a voltage VC corresponding to V/2 is derived by an expression. In this way, an output to a dimension 10 which has eliminated an error caused by a shadow is obtained, and a measuring error caused by the shadow can be eliminated.

Description

Detailed Description of the Invention (a) Technical Field of the Invention This invention measures the dimensions of a measured object by irradiating the measured object with parallel scanning light and detecting the shadow caused by the measured object with a photodetector. This invention concerns a light-based dimension measuring device that measures .

(b) Prior art and problems An example of a configuration diagram of a conventional device in such a case is shown in FIG.

In FIG. 2, 1 is a parallel scanning beam, 2 is an object to be measured, 3 is a condenser lens, and 4 is a photodetector.

When the parallel scanning light 1 is applied to the object 2 to be measured, a shadow 5 is formed by the object 2 to be measured.

A photodetector 4 detects the parallel scanning light 1 and generates a detection voltage V. In this case, the detection voltage V is output from the part where the parallel scanning light 1 hits the condenser lens 3, but the detection voltage V is 0 because the parallel scanning light 1 does not hit the part due to the shadow 5.

The conventional apparatus shown in FIG. 2 performs measurements by replacing the dimension 6 of the shadow 5 caused by the object to be measured 2 with the dimension 7 at which the detection voltage V is generated.

Next, FIG. 3 shows an enlarged view of the detected voltage V in FIG. 2.

Vl and V2 in FIG. 3 are voltages detected by the photodetector 4 by the condenser lens 3 in FIG. 1.

As is clear from FIG. 3, the detection voltage v1 and the detection voltage v
The ends of 2 are tapered down, and have a relationship of dimensions 7>dimensions 9>dimensions 8.

Dimension 8 is the dimension when the detection voltage V of the photodetector 4 is 0, and dimension 9 is the dimension at the intermediate portion between dimension 7 and dimension 8.

Dimension 7 is dimension 6 of shadow 5 in Figure 2, dimension 7> dimension 6
There is a relationship between

Therefore, it can be seen that among dimensions 7 to 9, dimension 9 is closest to actual dimension 6. This is a special request made in the 1970s.
It is also included in the specification of No.-40140.

These phenomena occur because the parallel scanning light 1 has a certain diameter.

Furthermore, the beam diameter of the parallel scanning light 1 may change depending on the horizontal position, and the optical power of the parallel scanning light 1 and the photodetector 4 may vary depending on the horizontal position.
Since the detection sensitivity of V changes due to aging, etc., the detection voltage V also changes.

Therefore, when trying to determine the dimension 6 of the object to be measured 2 from the detection voltage V of the photodetector 4, a measurement error may occur.

(c) Purpose of the Invention The purpose of the present invention is to reduce the measurement error caused by the conventional HK shown in FIG. 2 by adding an auxiliary circuit to the photodetector 4 shown in FIG. 172.

(d) Examples of the invention First, a block diagram of an embodiment according to the present invention is shown in FIG.

In FIG. 1, 11 is a divider, 12 and 13 are sample and hold circuits, 14 is an adder, and 15 is a comparator.

The divider 11 divides the detection voltage V of the photodetector 4 in half.

The sample and hold circuit 12 samples and holds the output of the divider 11 using a hold signal from a terminal 17.

The sample and hold circuit 13 samples and holds the output of the divider 11 using a hold signal from the terminal 18 .

Adder 14 adds the output of sample and hold circuit 12 and the output of sample and hold circuit 13.

The comparator 15 uses the output of the adder 14 and the detection voltage V of the photodetector 4 as human power, and outputs it when the value of the detection voltage V decreases and becomes equal to or less than the output of the adder 14.

Next, the operation of FIG. 1 will be explained with reference to FIG. ttE4.

First, the voltage V detected by the photodetector 4 due to the parallel scanning light 1 is input to the divider 11 .

The detection voltage V is obtained when the parallel scanning light l is focused by the condenser lens 3 and enters the photodetector 4 without the object to be measured 2 .

This detected voltage V is halved by a divider 11 and input to a sample and hold circuit 12.

The hold signal from the terminal 17 is applied to the sample and hold circuit 12 while the photodetector 4 is detecting the detection voltage V.

Therefore, the sample and hold circuit 12 holds the value of half of the detection voltage V.

The detection voltage V· in the m4 diagram is the output of the photodetector 4 when the parallel scanning light 1 is blocked, such as by a shadow 5 of the object to be measured 2, so it is theoretically zero. However, in reality, due to temperature drift of components used in the photodetector 4, a detection voltage V. as shown in FIG. 4 occurs.

This detected voltage V. is halved by a divider 11 and enters a sample and hold circuit 13.

A hold signal from terminal 18 is applied to sample and hold circuit 13 while photodetector 4 is detecting detection voltage V.

However, the sample hold circuit 13 detects the detection voltage V,
Hold half the value.

In FIG. 3, the dimension 0 at which the detection voltage v1 is halved is set to the dimension 6 of the object to be measured 2, but when the same means is applied to FIG. 4, the following results are obtained.

In FIG. 4, even when the parallel scanning light l in FIG. % Therefore, the addition T1. which adds the output of the sample hold circuit 12 and the output of the sample hold circuit 13 is required. The output of the device 14 corresponds to the voltage Vc from equation (1).

The voltage V, which is the output of the photodetector W4, and the output of the adder 14 are input to the comparator 15, and the comparator 15 outputs an output in the voltage range VC shown in FIG.

That is, the embodiment of FIG. 1 is for detecting the dimension 10 of FIG. 4.

(e) Effects of the Invention According to the present invention, an auxiliary circuit is added to the photodetector 4, and the detected voltage V is determined by the shadow 5 of the object to be measured 2.

Since the dimensions are determined in consideration of the above, it is possible to provide a dimension measurement V# position with less measurement error.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment according to the present invention, FIG. 2 is a block diagram of a conventional device, FIG. 3 is an enlarged view of the detected voltage V in the m2 diagram, and FIG. 4 is an explanatory diagram of the action of the m1 diagram. 1...Parallel scanning light, 2...Object to be measured,
3...Condensing lens, 4...Photodetector,
5...Shadow, 6~lO...Dimensions, 11.
...Divider, 12...S/Pull-hold circuit, 13...Sample-hold circuit, 14.
...-mg device, 15... comparator. Agent Patent Attorney Kin Omata Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. Dimensions by light, in which the dimensions of the object to be measured are measured by irradiating parallel scanning light onto the object to be measured and detecting the shadow caused by the object with a photodetector. The measuring device includes: a divider that halves the peak value of the output of the photodetector; a first sample hold circuit that holds the output of the divider due to a portion other than the shadow of the object to be measured; and the parallel scanning light. a second sample-and-hold circuit that holds the output of the divider when the signal is interrupted; an adder that adds the output of the first sample-and-hold circuit and the output of the second sample-and-hold circuit; and the peak value and the sum. 1. A dimension measuring device using light, comprising: a comparator that receives the output of the comparator as an input, and measures the dimension of the object from a position where the output of the comparator is output.