JPS638403B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dimension measuring device using an optical system.

This type of device includes an objective lens 2 that images an object 1 located at a point P on the optical axis at a point P' as shown in Fig. 1, and a focal position of this lens 2 on the point P' side. A telecentric optical system consisting of an aperture 3 installed is used. According to this optical system, the object 1 moves from point P to point m and the image forming point
When the image 1' of P' is blurred, the correct size can be determined by taking 1/2 of the amount of blur. Therefore, the scanning signal output of the image of point P' is the second
If it is a continuous quantity as shown in figure a, its peak value
By finding the 1/2 point of V _P using a comparison circuit, the correct dimensions (b in the same figure) can be obtained.

By the way, as shown in FIG. 3, an apparatus for measuring the dimension l of the object to be measured 33 by detecting the positions of both ends of the object to be measured 33 using array type photoelectric detectors 31 and 32 consisting of a plurality of photoelectric elements is as follows. Already known. That is, in this device, each detector 31, 32
This is done by counting the pulse output signals (Fig. 4a). However, in reality,
For example, a pulse output signal as shown in FIG. 4B is output due to unevenness in the light emission energy of the object to be measured 33, fluctuations in the path line, or characteristics of the photoelectric conversion element. Therefore, depending on the value of the comparison level V _L , the number of pulses counted varies greatly, resulting in an error. It is hardly practical to always set this comparison level V _L to a correct value because it is almost impossible to properly capture the above-mentioned unevenness in sensitivity of each element, unevenness in the amount of incident light, etc.

Furthermore, in the method of determining the dimensions of each photoelectric element based only on the presence or absence of output, its resolution is limited by the shape of each element and the number of bits of the elements in the detectors 31, 32. To deal with this limitation in resolution due to element shape, as seen in Japanese Patent Application Laid-Open No. 51-9864, each element is used in an unsaturated region, and each element is There is a measurement method that is not affected by the shape of the However, this method does not take into account blurred images, uneven sensitivity of each photoelectric element, or gaps between each photoelectric element, and measurement errors may occur due to these factors.

The present invention has been made to address the above-mentioned problems, and it distinguishes between pulse output signals output from a group of photoelectric conversion elements at a set value level, and output signals exceeding the set value and those below the set value. The purpose of the present invention is to provide a dimension measuring device that can measure appropriate dimension values with few measurement errors by separating the output signals of the two, converting them into corresponding digital quantities, and adding them.

An embodiment of the present invention will be described below with reference to FIGS. 5 and 6. 50 is a drive circuit that scans an array type photoelectric detector 51 configured by arranging a plurality of photoelectric conversion elements in a straight line. This detector 51
receives an optical image of the object to be measured 53 from the objective lens 52, and outputs a pulse signal _S51 as shown in FIG. 6a based on the scanning signal of the drive circuit 50.
Both ends A and B of this signal _S51 are optical images of both ends of the object to be measured 53, and hereinafter these parts will be referred to as blurred parts. The signal S ₅₁ having the blurred portions A and B is amplified by the amplifier 54 and then supplied to the sample-and-hold circuit 55, where it is converted into a step-like signal S ₅₂ as shown in FIG. 6b. That is, this signal S ₅₂ is
By holding the peak value of the pulse _S51 , the blurred portions A and B become stepwise signal components.

This signal S ₅₂ is supplied to an AGC circuit 56 and two comparison circuits 57 and 58. AGC circuit 5
6 adjusts, for example, the scanning frequency of the drive circuit 50 in response to the signal _S52 , and adjusts the optical energy accumulation time in each photoelectric conversion element. Further, one comparison circuit 57 compares the signal S ₅₂ with a set value level S ₅₃ of the setting circuit 60, and outputs a rectangular signal S ₅₄ shown in FIG. 6c corresponding to the portion exceeding the set value. This outputs the following. This set value level _S53 is set to a level higher than the sensitivity unevenness of each photoelectric conversion element. In other words, the output peak value when an unblurred image is detected over the entire surface of each element is set to a value that allows discrimination, taking into consideration the sensitivity unevenness of each element. Further, the other comparison circuit 58 receives the signal S ₅₂
and a comparison signal _S55 from the time function generation circuit 61, and outputs a signal _S56 with a pulse width proportional to the peak value of each photoelectric conversion element. This comparison signal _S55 is a signal that matches the scanning period of the photoelectric conversion element.

The output signal S ₅₄ of one comparison circuit 57 is sent to one input terminal of the AND circuit 63 via the NOT circuit 62, and the output signal S ₅₆ of the other comparison circuit 58 is
The signals are respectively supplied to the other input terminals of the AND circuit 63. That is, this AND circuit 63 performs an AND operation on the signal S ₅₄ ' shown in FIG. 6e and the signal S ₅₆ shown in FIG. 6 d, and outputs the signal S ₅₇ shown in FIG.
Therefore, this signal _S57 corresponds to the blurred portions A and B of the signal _S51 . This signal S ₅₇ is supplied to the OR circuit 64 together with the signal S ₅₄ from the one comparison circuit 57.

That is, the comparison circuit 57 separates and extracts the signal of the photoelectric conversion element portion that received the unblurred image, and the signal of the photoelectric conversion element portion that received the blurred image is separated and extracted by the comparison circuit 58 and the AND circuit 63, respectively.
Then, the separated signal S ₅₄ and signal S ₅₇ are supplied to the OR circuit 64, and a combined signal shown in FIG.
_S58 is supplied to the subsequent AND circuit 65.

Then, the AND circuit 65 converts the composite signal into pulses per unit from the count clock generation circuit 66, and the signal _S60 is counted by the counter 67 to detect the dimensions of the object to be measured 33. .

By the way, the composite signal S ₅₈ is similar to the output signal S ₅₆ of the other comparison circuit 58, but for the following reason, this output signal S ₅₆ is not used, and the signal S ₅₄ and the signal S ₅₇ are combined. output. In other words, if each photoelectric conversion element that detects a non-blurred image has uneven sensitivity or a dead space between the elements, the corresponding output portion of the other comparison circuit 58 will not be the same as the signal _S54 of one comparison circuit 57. First, it becomes a pulse-like signal similar to the blurred portion. Therefore, if this signal is directly converted into a pulse signal by the AND circuit 65 as the signal of the object to be measured 33, it will be assumed that there is no image of the object to be measured 33 in areas such as dead space, and an error will inevitably occur. Become. On the other hand, according to the present invention which uses the signal _S54 , it is possible to extract a signal that is not affected by uneven sensitivity of each photoelectric conversion element or dead space between elements. Furthermore, the present invention can also be used in a dimension measuring apparatus that uses two detectors 31 and 32 to detect both ends of an object to be measured 33, respectively, as shown in FIG. Further, the present invention is not limited to measuring the width of an object to be measured, and can be used for measuring dimensions such as thickness and length.

In the present invention, in this way, the pulse signal output from the photoelectric converter is discriminated and separated at the set value level, and each is converted into a digital quantity.
Each can be converted into digital quantities under optimal conditions, making it possible to measure accurate dimensions without errors. In addition, after converting the pulse output signal exceeding the set value into a rectangular signal and the pulse output signal below the set value into a pulse signal with a width corresponding to the output of each element, both signals are combined and converted into a digital quantity. Therefore, it is possible to perform accurate dimension measurements without being affected by uneven sensitivity of each element or dead space between elements.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic diagrams and waveform diagrams for explaining the principle of optical dimension measurement, Figures 3 and 4 are schematic configuration diagrams for explaining the actual dimension measurement device,
5 and 6 are a circuit configuration diagram and a waveform diagram for explaining an embodiment of the present invention. In the figure, 51 is a photoelectric detector, 55 is a sample and hold circuit, 57 and 58 are comparison circuits, 60 is a setting circuit, 61 is a time function generation circuit, 62 is a negative circuit,
63 and 65 are AND circuits, 64 is an OR circuit, 66
is a count clock generation circuit, and 67 is a counter.

Claims (1)

[Claims] 1. In an apparatus for measuring the dimensions of the object to be measured by forming an image of the object to be measured on a plurality of photoelectric conversion elements arranged in a straight line and scanning these elements one after another using pulse outputs obtained, The pulse output of the element is discriminated and separated by a set value level, and the pulse output exceeding the set value level is made into a continuous rectangular wave signal, and all the pulse outputs are made into pulse width signals corresponding to their respective peak values. , by subtracting the square wave signal from the pulse width signal,
After once separating the pulse output that exceeds the set value level and the pulse output that does not exceed the set value level into a rectangular wave signal and a pulse width signal, both signals are combined, this combined signal is converted to a digital quantity, and the digital quantities are added. A dimension measuring device characterized by measuring the dimensions of an object to be measured.