JP3599295B2 - Optical dimension measuring device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a scanning type optical dimension measuring apparatus that measures a dimension of a workpiece by scanning a parallel beam.
[0002]
[Background Art]
A scanning optical measuring device that scans a laser beam in parallel at a constant speed and irradiates the object to be measured (work), and measures the dimensions of the work from a light / dark pattern (scan signal) detected on the back side of the work. is there. The measurement principle of this type of measuring device is that the laser beam scans in parallel and this work interrupts this beam, and the time when the laser beam does not reach the sensor that detects the laser beam located behind the work, More specifically, the number of clock pulses having a very short period output from the clock circuit during that period is counted, and the count value is converted into a length by a microcomputer to determine the size of the work.
[0003]
FIG. 2 shows a functional block diagram of the scanning optical dimension measuring device. This apparatus includes a measurement unit 100 centered on an optical system and a display unit 200 centered on a processing system. Both are connected by a multi-core cable 300. Using this cable 300, a power supply and a motor synchronization signal are transmitted from the display unit 200 to the measurement unit 100, and a scan signal described later is transmitted from the measurement unit 100 to the display unit 200.
[0004]
In FIG. 2, reference numeral 10 denotes a laser light source. A laser beam 12 output from the laser light source 10 is converted into a rotary scanning beam by a polygon mirror 14, and is further reduced in beam diameter by an f-.theta. It is converted into a scanning beam 20. The parallel scanning beam 20 is irradiated so as to scan the measurement area including the work 22 with the rotation of the polygon mirror 14, and is incident on the measurement light receiving element 26 through the condenser lens 24. 28 is a mirror for reflecting the laser beam 12 to make it incident on the polygon mirror 14, 30 is a motor for rotating the polygon mirror 14, 32 is arranged near the boundary outside the effective scanning range of the scanning beam 16, and starts or ends one scanning Is a light receiving element for resetting which detects
[0005]
The output of the measurement light receiving element 26 is amplified by an amplifier 48 and then input to an edge detection circuit 50. The edge detection circuit 50 shapes the output of the amplifier 48 to perform edge detection. On the other hand, the output of the reset light receiving element 32 is input to the reset circuit 52. The reset circuit 52 generates a reset signal based on the output timing of the reset light receiving element 32.
[0006]
The gate circuit 56 turns on and off at the timing of the edge signal output from the edge detection circuit 50 and the reset signal output from the reset circuit 52, and the counter circuit 58 counts the clock pulse input during the ON cycle of the gate circuit 56. And measure the time between signals. The clock pulse is generated and output by the clock circuit 54, and is also used for synchronizing the rotation of the motor 30. The motor synchronization circuit 60 is a synchronization signal generator for this purpose, and 62 is a motor drive circuit. The laser output adjustment circuit 64 controls the output of the laser light source 10 so as to keep it constant. The CPU 40 performs various calculation processes and controls. The measured value obtained by the calculation process is displayed on the display device 44, and the keyboard 42 is used for setting the measurement mode. The ROM 46 stores various calculation processing programs and control programs. The RAM 45 is used to temporarily store calculation results and the like.
[0007]
As shown in FIG. 3, the output (scan signal) of the amplifier 48 becomes a bright portion having a high level when the laser beam is incident on the light receiving element 26 without being interrupted by the work. Low dark area. That is, the lower part at the center of the graph in FIG. 3 indicates the size of the work. However, this is the case where the work 22 is a light-shielding body, and if this is a light-transmitting body like a slit, the light / dark relationship is reversed. In any case, the size of the work can be measured from the width of the dark part (or the light part). To realize this principle, the edge detection circuit 50 binarizes this scan signal at a predetermined threshold level and converts it into an edge signal.
[0008]
Meanwhile, the measuring unit 100 shown in FIG. 2 has a non-uniform scanning speed due to the aberration and processing accuracy of the polygon mirror 14 and the f-θ lens 18, resulting in an error in the measured value of the length in the scanning direction Z. FIG. 4 shows an example of this error distribution. In the figure, the horizontal axis represents the count value of the clock pulse, and the vertical axis represents the error from the distance obtained by actually measuring the distance obtained by multiplying the count value by a constant as the zero value. This error means that when the same work 22 is measured, a difference occurs in the measured value if the error position in the vertical direction of the work is different.
[0009]
If the processing accuracy of this type of optical system is increased or the aberration is designed to be low, such a measurement error can be reduced, but a mirror or a lens becomes extremely expensive. In addition, for example, in order to increase the accuracy of the f-θ lens 18, the number of lenses to be combined increases and the thickness increases, which hinders miniaturization and weight reduction of the measurement unit.
[0010]
Since the above-described error is specific to the measurement unit, it must be corrected for each measurement unit. In general, as shown in FIG. 4, the error characteristic is subdivided in the scanning direction and linearly approximated, and the inverse characteristic is stored in a ROM as correction data. An inexpensive and reliable method of obtaining corrected measurement data by performing an operation such as addition is often used.
[0011]
[Problems to be solved by the invention]
Usually, the correction data is often stored in the ROM on the display unit side. However, in this case, the measuring section and the display section have a one-to-one correspondence, and a malfunction occurs if the measuring section and the display section are rearranged. Therefore, conventionally, a plate or the like marked with the same identification number or the like is stuck on the housing of the corresponding measurement unit and display unit, and an operator checks so as not to connect the measurement unit and the display unit in an incorrect combination when connecting the cable. Was like that. However, the connection may still be incorrect, and if the connection is incorrect, the measurement unit and the display unit will continue to use without noticing that they do not correspond, and the measurement data will be corrected by the incorrect correction data. Therefore, a measurement result having a large error may be output.
[0012]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a scanning-type optical dimension measuring apparatus that prevents an erroneous connection between a measurement unit and a display unit that correspond one-to-one.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention scans a predetermined measurement area on which a workpiece is arranged with a parallel beam, and synchronizes the scan obtained by receiving a beam passing through this measurement area with a light receiving element. A measurement unit that outputs a scan signal, and a display unit that is connected to the measurement unit by a cable, detects a position of a rising edge or a falling edge of the scan signal, and measures a dimension of the work. In the scanning optical dimension measuring device, a storage device (5) provided in the measuring unit for storing the identification number of the measuring unit, a storage device (46) provided in the display unit, and the storage device (46) Means for detecting and displaying that the identification number of the identification number read in advance in 46) and the corresponding correction data does not match the identification number stored in the storage device (5); Characterized by comprising a.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments using the present invention will be described with reference to the drawings. In the drawings, the same reference numerals denote the same components.
FIG. 1 shows an external view of a scanning optical dimension measuring apparatus according to the present invention, and FIG. 2 shows a functional block diagram of its internal circuit. The basic configuration of a conventional scanning optical dimension measuring apparatus and the scanning optical dimension measuring apparatus using the present invention are the same. A measuring unit 100 that scans a laser beam and irradiates the work to detect a signal on the rear side of the work, and a display unit 200 that inputs a detection signal output from the measuring unit to calculate and display a dimension value is a cable. 300 is connected. The measuring unit 100 has a built-in ROM 5 in which an identification number or the like unique to the measuring unit is stored. In addition, the display unit 200 has a built-in ROM 46 in which the identification number of the corresponding measuring unit and the like and the correction data obtained based on the characteristics of the optical system in the laser beam scanning direction of the measuring unit are stored. Correction data unique to the measuring unit 100 is obtained by detecting a scan signal by precisely feeding a sharp reference such as a knife called a knife edge by a certain amount by a fine fine feed device such as a micrometer, It is obtained by obtaining a graph as shown in FIG. The error characteristic shown in this graph is subdivided in the scanning direction and linearly approximated, and the inverse characteristic is stored in the ROM 46 as correction data, and this correction data is added to the measured data during actual measurement. By adding the above calculation processing, it is possible to correct an optical error unique to the measuring section.
[0015]
When the measuring unit 100 and the display unit 200 are connected by the cable 300 and the power is turned on, first, the identification number is read from the ROM 5 to the display unit 200 side. Next, it is checked whether the read identification number matches the identification number stored in the ROM 46 in advance. If the identification numbers match, it is determined that the data is compatible. Thereafter, the measurement data is sequentially corrected by the correction data stored in the ROM 46 in advance, and the result is displayed on the display device 44 as a measurement value.
[0016]
If the identification numbers do not match, it is determined that the combination of the measurement unit and the display unit is incorrect, and a predetermined error symbol, an error code number, and the like are displayed on the display device 44, blinking, and a warning sound is issued. Thus, the operator can be informed that the connection is incorrect, and can be prompted to reconnect the correct measurement unit 100 corresponding to the display unit 200.
[0017]
As the identification number, anything that can identify the measuring unit 100, such as a serial number or a model code of a product, can be used.
[0018]
In the ROM 46 of the display unit 200, in addition to the error correction data obtained based on the characteristics of the optical system in the scanning direction of the laser beam of the measuring unit 100, various types of measurement operations such as the resolution of the measurement data and the motor speed of the measuring unit are provided. A parameter group is stored.
[0019]
As described above, the present invention has been described with reference to the preferred embodiments. However, the present invention is not limited to the embodiments, and can be modified without departing from the scope of the present invention.
For example, the means for storing the identification number in the measurement unit 100 has been described as a ROM, but the identification number can be expressed by a combination of simple switch elements such as a dip switch.
[0020]
If the identification numbers of the plurality of measurement units 100 and the corresponding correction data, the resolution of the measurement, and the parameter group such as the speed of the motor are stored in the ROM 46, the plurality of measurement units 100 may be stored in one display unit 200. Can be used by switching.
[0021]
【The invention's effect】
As described above, according to the present invention, it is possible to eliminate a mistake in connection between a measurement unit and a display unit corresponding to one-to-one correspondence in a scanning optical dimension measuring apparatus, and to prompt an operator to make a correct connection.
[Brief description of the drawings]
FIG. 1 is an external view of a scanning optical dimension measuring apparatus according to the present invention.
FIG. 2 is a functional block diagram of a conventional scanning optical dimension measuring device according to the present invention.
FIG. 3 is a graph showing scan signals of the present invention and a conventional scanning optical dimension measuring device.
FIG. 4 is a graph showing an error distribution in a scanning direction of the scanning optical dimension measuring device.
[Explanation of symbols]
5 ROM
REFERENCE SIGNS LIST 10 laser light source 12 laser beam 14 polygon mirror 16 rotating scanning beam 18 f-θ lens 20 parallel scanning beam 22 work 24 condensing lens 26 measuring light receiving element 28 mirror 30 motor 32 reset light receiving element 40 CPU
42 keyboard 44 display device 45 RAM
46 ROM
48 Amplifier 50 Edge detection circuit 52 Reset circuit 54 Clock circuit 56 Gate circuit 58 Counter circuit 60 Motor synchronization circuit 62 Motor drive circuit 64 Laser output adjustment circuit 100 Measurement unit 200 Display unit 300 Cable

Claims (1)

A measuring unit that scans a predetermined measurement area on which a workpiece is arranged with a parallel beam, and outputs a scan signal synchronized with the scan obtained by receiving a beam passing through the measurement area with a light receiving element; and the measurement unit. And a display unit for detecting a position of a rising edge or a falling edge of the scan signal to measure a dimension of a work, and a scanning optical type dimension measuring apparatus,
A storage device (5) for storing an identification number of the measurement unit provided in the measurement unit;
A storage device (46) provided in the display unit;
Means for detecting and displaying that the identification number of the identification number previously written in the storage device (46) and the corresponding correction data does not match the identification number stored in the storage device (5). An optical dimension measuring device, comprising:

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