JPH0455706A - Work-position detector - Google Patents

Abstract

PURPOSE:To make it possible to detect a position highly accurately by providing an operation controlling part which operates the difference in digital voltage values based on the digital signals of corresponding probes and judge whether the difference is within a preset allowance or not. CONSTITUTION:Probes 14a and 14b are arranges so as to stride on the edge parts of a work 10. Then, the amount of received reflected light is decreased by a part which is broken in the work 10. Therefore, the position of the work 10 in the direction X can be judged by comparing the amounts of the received reflected light beams at the two probes 14a and 14b which are provided in the direction X. In AD converter 22, the analog voltages corresponding to the amounts of the received reflected light beams are outputted as the 12-bit digital signals. In an operation controlling part 24, the digital values corresponding to the digital signals from both converters 22 are compared. The difference is operated, and whether the difference is located within the allowance range or not is discriminated. When the difference is located within the preset allowance range, it is discriminated that the work 10 is arranged on an X-Y table 12 in the intended accuracy, and the fact is displayed on a display part 26.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a workpiece position detection device.

(Conventional technology) Various means for detecting the position of various workpieces are known.

A common example of these detection devices is an image processing device equipped with a camera device.

However, when using the above-mentioned apparatus, there is a problem that resolution is limited due to aberrations of the lens of the camera apparatus, and image processing such as evaluation using OTF becomes complicated.

(Objective of the Invention) The present invention has been made to solve the above-mentioned problems, and its purpose is to detect a workpiece position with a simple mechanism, high resolution, and improved detection accuracy. We are in the process of providing equipment.

(Means for Solving the Problems) In the workpiece position detection device according to the present invention for the above purpose,
It is equipped with a workpiece resting section on which a workpiece is placed, an optical fiber for transmitting light, and an optical fiber for light reception, with the end face facing the edge of the workpiece placed on the workpiece resting part, and with the end face facing the edge of the workpiece placed on the workpiece resting part. at least two probes that are fixedly arranged at positions where the amount of light received by the workpiece is approximately the maximum; and a photoelectric sensor that is connected to the light-receiving optical fiber of each of the probes and generates an analog voltage according to the amount of light received from the workpiece. a converter, an AD converter connected to the photoelectric converter and converting the analog voltage into a digital signal of predetermined bits according to the voltage value; a digital signal from the AD converter is input, and each of the corresponding The present invention is characterized by comprising a calculation control section that calculates a difference between digital voltage values based on the digital signal of the probe and determines whether the difference is within a set allowable range.

(Function) The probe is fixedly placed at a position with its end face facing the edge of the workpiece and where the amount of light reflected from the workpiece is approximately maximized. The amount of light received by this type of probe is
The peak occurs at a position where the probe is a certain distance MM from the workpiece. This peak can be seen to be approximately constant within a certain allowed range, and within this range, even if the distance to the workpiece changes, the amount of received light remains approximately constant. Therefore, by arranging the probe at a position where the amount of received light is approximately at its peak, it is possible to detect the position of a workpiece even if the thickness of the workpiece has some variation.

For example, when there is a difference in the amount of reflected light received from the work edge portions of two probes arranged in the X direction, it can be seen that the work is deviated toward the probe that receives a larger amount of light in the X direction.

The reflected light that passes through the probe is converted into an analog voltage according to the amount of light in a photoelectric converter, and this analog voltage is A
A D converter converts the signal into a digital signal of predetermined bits, for example, 12 bits, and inputs the signal to the arithmetic control section. The arithmetic control section compares the input digital values from each AD converter, calculates the difference, and determines whether this difference is within a set allowable range. If the setting is within the permissible range, it means that the workpiece is placed at the desired position on the workpiece placement section.

If the setting is outside the permissible range, a message will be displayed to that effect or the position of the workpiece will be corrected.

For example, when the diameter of the probe is 3 mm and the AD converter is 2 bits per month, a resolution of 1 μm or less can be obtained, and position detection can be performed with high accuracy.

(Embodiment) A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram of a position detection device according to the present invention.

In the figure, reference numeral 10 denotes a workpiece whose position is to be detected, which is placed on a workpiece mounting section, for example, an XY child table 2. The XY table 2 can be freely moved within a two-dimensional plane by a drive source 13.

14a and 14b are probes whose end faces are connected to the workpiece 1.
For example, they are arranged so as to face each other so as to straddle the edge portions at both ends in the X direction of the workpiece 10, and to be separated from the workpiece 10 by a predetermined distance. As illustrated in FIG. 2, the probe 14 is composed of a group of optical fibers 16a for projecting light and a group of optical fibers 16b for receiving light. A light projecting section 16 is connected to the end of the light emitting side of the group of optical fibers for projecting light, and a light receiving section 18 and a photoelectric converter 20 such as a photodiode are connected to the end of the group of optical fibers for receiving light. Ru. The photoelectric converter 20 receives light that has passed through a group of optical fibers for light reception, and converts it into an analog voltage according to the amount of light.

22.22 is a 12-bit AD converter connected to the output side of the photoelectric converter 20.20. This AD converter 22 converts the analog voltage into a digital signal and removes noise. This digital signal is input to the calculation control section 24.

As will be described later, the arithmetic control section 24 compares the digital values input from each AD converter 22 to calculate the word multi-position, displays the calculation result on the display section 26, and displays the XY child table for position correction. A command is issued to the second drive source 13.

FIG. 3 is a curve showing a change in the amount of reflected light entering the group of light receiving optical fibers when the distance of the end face of the probe 14 from the workpiece 10 is changed. At displacement 0, the amount of reflected light is O
From this point on, it rises linearly to a single peak, and as you move further away, the amount of received light decreases linearly. Using the straight line portion of this curve, the distance of the workpiece IO from the probe 14 or from an appropriate object located at a constant distance from the probe 14 can be determined.

In the present invention, such a distance between the workpiece IO is not determined.

In the present invention, the position of the workpiece 10 in the X, Y, or XX direction is determined. In other words, the position of the center of the workpiece 10 on a certain plane is determined. For that purpose, workpiece 10 and probe 1
4. Fix the distance to the end face.

The probe 14 is fixed at a position where the amount of reflected light from the workpiece to which it receives light is approximately maximum. Unlike the straight section, the probe 14 has a peak amount of received and reflected light.
A certain width can be seen in the distance from the workpiece.

For example, in the case of a probe with a diameter of about 3 mm, 2
A width of about 00 to 300 μm is allowable. In other words, near the peak, the distance between the workpiece and the probe end face is 20
Even if there is a deviation of about 0 to 300 μm, the amount of received and reflected light can be considered to be approximately constant. Therefore, even if the thickness of the workpiece varies by a maximum of about 200 to 300 μm, it can be used.

When the probes 14a and 14b are arranged so as to straddle the respective edges of the work 10 as described above, the amount of received and reflected light decreases by the amount of the missing part of the work 10. For example, if the work edge portion covers only 50% and 30% of the entire end surface of the probe 14, respectively, the area of the work edge portion is 50% and 30% of the entire end surface of the probe 14, respectively, as shown by the broken line in FIG.
%, a curve of the amount of reflected light of 30%. However, the peak position remains unchanged.

Therefore, the two blowers 4a and 1 arranged in the X direction
The position of the workpiece 0 in the X direction can be determined by comparing the amount of light received and reflected by the light beam 4b.

In other words, when the amount of light received by one probe is greater than that of the other, the workpiece 10 is placed on the side of the probe that receives more light.
If they are equal, work 1
The center of 0 will be located at the center between both probes.

The AD converter outputs an analog voltage corresponding to the amount of received and reflected light as a 12-bit digital signal. Therefore, if the diameter of the probes 14a and 14b is 3 mm,
The deviation (in the X direction) of the edge portion of the workpiece 10 with respect to the probes 14a and 14b can be accommodated with a resolution of 3/4096 (mm), that is, lum or less.

The calculation control unit 24 compares the digital values corresponding to the digital signals from both AD converters 22, calculates the difference between them, and determines whether the difference is within a set allowable range. If the difference is within the set range, it is determined that the workpiece is placed on the χY child table 2 with the desired accuracy, and this fact is displayed on the display unit 26.

If the difference is outside the set tolerance range, either a message to that effect is displayed, or the drive unit 13 of the XY child table 2 calculates how much and in which direction the workpiece 10 should be moved.
This command is used to move the workpiece IO in a predetermined direction. In this way, the position of the workpiece 10 can be detected.

In the above, two probes 14a, 1 are arranged in the X direction.
4b was placed. In this case, when the workpiece 10 is transported along a predetermined transport line, it can be effectively used to detect whether the workpiece 10 is being transported with its center accurately positioned at the center of the transport line.

By arranging two probes in the X direction as well as in the X direction, the position of the center of the workpiece in the XY plane can be detected. In this case, for example, when a CD (compact disc) is installed in a surface inspection device and the CD surface condition is inspected while rotating the CD, check whether the center of the CD is accurately installed at the center of rotation of the surface inspection device. It can be effectively used for position detection, etc.

Although various preferred embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the invention. be.

(Effects of the Invention) As described above, the present invention has the remarkable effect of being able to accurately detect the position of a workpiece with a simple configuration.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing an overview of the position detection device, Figure 2 is an explanatory diagram showing an example of the arrangement of the probe's light emitting optical fiber group and light receiving optical fiber group, and Figure 3 is the distance of the probe from the workpiece. 2 is a graph showing changes in the amount of received and reflected light. 10... Work, 12... XY child table work placement part), 14a, 1
4b...-probe, 20... photoelectric converter, 22... AD converter, 2
4... Arithmetic control unit. Distance from workpiece

Claims (1)

[Claims] 1. A workpiece resting section on which a workpiece is placed, and an optical fiber for transmitting light and an optical fiber for receiving light, each having an end face facing an edge of a workpiece placed on the workpiece resting part. at least two probes that are fixedly arranged at positions where the amount of light reflected from the workpiece is approximately the maximum; a photoelectric converter that generates a corresponding analog voltage; an AD converter that is connected to the photoelectric converter and converts the analog voltage into a digital signal of predetermined bits that corresponds to the voltage value; and a digital signal from the AD converter. and a calculation control unit that calculates the difference between the digital voltage values based on the digital signals of the respective corresponding probes, and determines whether the difference is within a set tolerance range. Device.