JPS62254003A - Scanning optical edge discriminator - Google Patents

Abstract

PURPOSE:To accurately discriminate the end part of an article to be measured even if the number of rotations of a motor vary and the article to be measured displaces, by correcting the interval of the output pulse of a binarization circuit during scanning in a correction circuit. CONSTITUTION:The light from a light projection element 1 is scanned plural times and the end part of an article 6 to be measured is discriminated from the output signal of a photodetector 7 generated by shielding the article 6 to be measured arranged between the element 1, and photodetector 7. At this time, the light receiving signal (a) of the photodetector 7 reaching from the element 1 is amplified and binarized by an amplifier 8 and inputted to a pulse converter 19 as a pulse (g). The pulse group (h) outputted from the pulse converter 19 corresponding to the rising and falling of the pulse (g) is constituted of four extremely short pulses. The clock pulse outputted from an oscillation circuit 11 is counted by a count circuit 12 and the signal thereof is transmitted to a latch circuit 20. The latch circuit 20 latches the count signal on the basis of the pulse group (h) to transmit the same to a correction circuit 21 where correction is performed on the basis of the difference between the count values of previous and present signals to measure the accurate outer diameter of the article 6 to be measured.

Description

[Detailed description of the invention] [Industrial application field] This invention is for measuring the outer diameter of the object to be measured and identifying the edges.

The present invention relates to a scanning optical end discriminator for measuring hollow parts, etc., and in particular to a miniaturized scanning optical end discriminator that measures minute objects.

[Conventional technology]

A scanning optical end discriminator is commonly used to measure outer diameter. Therefore, a scanning optical outer diameter measuring device, which is one usage form of a scanning optical end discriminator, will be explained below as an example.

Since a scanning type optical outer diameter measuring device can measure the outer diameter without contact, it is often used when the object to be measured is a moving object, a high-temperature object, or the like. Hereinafter, the principle of this scanning type optical outer diameter measuring instrument will be explained based on FIG. 3.

The laser beam projected from the laser tube l passes through the fixed mirror 2.
The beam is reflected by the rotating mirror 3 and converted into a scanning beam. The scanning beam is converted into a parallel scanning beam by the collimator lens 4, and scans the object to be measured 6 placed between the collimator lens 4 and the condenser lens 5 at high speed. At this time, the outer diameter of the object to be measured 6 is measured from the length of the dark or bright portion of the parallel scanning beam caused by the shielding of the object to be measured 6.

That is, the brightness or darkness of the parallel scanning beam due to the shielding of the measurement object 6 is detected as a change in the output signal a of the light receiving element 7 placed at the focal position of the condenser lens 5. This output, No. 1 a, is amplified and binarized by an amplifier 8 and transmitted to a segment selection circuit 9. The segment selection circuit 9 is
The light reception signal of the light receiving element 7 is transmitted to the gate circuit 10 for a scanning time corresponding to the outer diameter of the object 6 to be measured. Since the gate circuit 10 also receives the clock pulse CP from the beam 1 cock pulse oscillation 2% 11, the gate circuit 10 inputs the clock pulse P at the scanning time t to the counting circuit 12.
to communicate. The counting circuit 12 counts the input clock pulses 1) and transmits the counted value to the display 136.

The display 13 displays the outer diameter of the object to be measured 60) based on this counted value.

However, 2. this scanning optical outer diameter measuring instrument does not take into account any countermeasures when the rotational speed of the motor (not shown) that rotates the rotary mirror 3 changes. As a result, errors occur in the measured values. If a high-precision motor is used, the fluctuations will be small and the measurement error will be small. However, 8
Since each of these motors is expensive, large, and large, it is impossible to provide an inexpensive and compact scanning optical outer diameter measuring instrument using this motor. In addition, extremely precise measurements (1
Even if this motor is used, it is difficult to perform a line (in μm).

In order to solve this problem, a method has been proposed for correcting measurement errors due to variations in the rotational speed of the motor.

As shown in FIG. 4, a scanning optical outer diameter measuring instrument using this method has two light receiving elements 14a near the collimator lens 4 of the scanning optical outer diameter measuring instrument (see FIG. 3).
, 14b are fixedly installed, and the fixed mirror 3 is linked to a motor.
There is a difference in the configuration for monitoring the rotation of the A waveform shaper 15 binarizes the output signal of the light receiving element 14a into a pulse b', and a waveform shaper 16 binarizes the output signal C of the light receiving element 14b into a pulse C'. Free knob flop 1 due to pulse b°
7 is set and reset by pulse C'.

Therefore, the flip-flop 17 outputs a pulse d which rises in response to the rise of the pulse b' and falls in response to the fall of the pulse C'.

Inputting this pulse d and the clock pulse CP from the clock pulse oscillator 11, the gate circuit 10b outputs the pulse e. By inputting this pulse e, the counting circuit 1
2b measures the scanning time from the light receiving element 14a to the light receiving element 14b.

On the other hand, the light-receiving signal a of the light-receiving element 7 is transmitted to the gate circuit 10a via the amplifier 8 and the segment selection circuit 9. The gate circuit 10a outputs a pulse f based on the clock pulse CP. Inputting this pulse f, the counting circuit 12a measures the scanning time (corresponding to the outer diameter) of the dark area caused by the shielding of the measuring object 6.

An arithmetic correction circuit 18, which receives the output signals of the counting circuits 12a and 12b, corrects the output signal of the counting circuit 12a using the output signal of the counting circuit 12b. That is, the light receiving element 14
The scanning time from a to the light receiving element 14b is always a constant time if the rotational speed of the motor is constant. Therefore, by correcting the scanning time of the dark area due to the shielding of the object 6 to be measured using this scanning time, it is possible to always accurately measure the outer diameter even if the rotational speed of the motor varies.

[Problems that the invention attempts to solve] However, this method has the following two serious problems. First, the first problem will be described. The diameter of the scanning beam is determined by collimator lens 4 and condensing lens 5 (fourth
Since the diameter is set to be the most minute at the point corresponding to the central part of these lenses, which is located in the middle of the center of the lens (see figure), the diameter of the light-receiving elements 14a and 14b is considerably larger than that at the indicated point. . Then, the light receiving element 14a,
14b light reception signal.

C rises and falls slowly.

Therefore, the waveform of the output pulse d of the Frisobuf 1 tip 17 becomes inaccurate, and the opening time of the gate of the gate circuit 10b cannot be set accurately.

In order to solve this problem, the light receiving elements 14a, 14
It has been proposed to provide a lens, knife, etc. in front of the light receiving signal (b) to sharpen the rise and fall of the light receiving signals (a) and (c). However, this increases the number of parts and complicates the configuration, making it difficult to downsize the scanning optical outer diameter measuring instrument.

Next, the second problem is that when the measurement object 6 itself is displaced,
Even if the above-mentioned method is employed to correct errors caused by fluctuations in the rotational speed of the motor, measurement errors caused by the displacement will occur, making accurate measurement impossible.

This idea was made in view of the problem described in L, and is intended to eliminate measurement errors caused by fluctuations in the rotational speed of the motor in scanning optical edge discriminators such as scanning optical outer diameter measuring instruments. It is an object of the present invention to provide a scanning optical end discriminator that can correct the end of the object to be measured and can accurately determine the end of the object to be measured even if the object itself is displaced.

[Means for solving problems]

A concrete means for solving the problem described in F and achieving this objective is to scan the light from the light emitting element multiple times, and place the light U between the light emitting element and the light receiving element on the object to be measured. #; In a scanning optical edge discriminator that discriminates the edge of the object to be measured from the output signal of the light receiving element generated by shielding, an oscillation circuit that outputs a clock pulse and a a binarization circuit that outputs pulses in response to rising and falling edges of the output signal of the light receiving element;
The present invention includes a latch circuit that latches this pulse based on the clock pulse, and a correction circuit that corrects the output signal of this latch circuit for each scan by the output signal of the latch circuit of the previous scan and the current scan. be.

[For production]

Since this invention employs the above-mentioned means, the following effects are brought about. When fluctuations in the rotational speed of the motor or displacement of the object to be measured occur, the above-mentioned occurrence does not occur in the intervals between the pulses of the binarization circuit that are output in response to the rising and falling edges of the output signal of the light receiving element. An error will occur.

Therefore, in order to correct this error, the correction circuit performs arithmetic processing on the count values of these pulses in the scans before the current scan latched by the latch circuit and the count values of the pulses currently being scanned. That is, the interval between corresponding pulses in the scan before the current scan and the current scan corresponds to an integral multiple of l scan time.

Therefore, from this interval, fluctuations in the rotational speed of the motor and displacement of the object to be measured itself can be ascertained. Therefore, by correcting the interval between the output pulses of the binarization circuit during the current scan in the correction circuit, it is possible to accurately determine the edge of the object to be measured.

〔Example〕

The present invention will be described in detail below based on an embodiment in which the invention is used as a scanning optical outer diameter measuring device.

Note that the same parts as in the conventional example are given the same symbols to simplify the explanation.

As shown in FIG. 1, the configuration of the scanning optical end discriminator according to the present invention is different from that of the conventional example (see FIG. 3) until the laser light from the laser tube 1 reaches the light receiving element 7. The components of are the same. The light-receiving signal a of the light-receiving element 7 is sent to the amplifier 8.
The signal is amplified and binarized, and a pulse g as shown in FIG. 2(g) is output.

The pulse converter 19 inputs this pulse g and outputs a pulse group as shown in FIG. This pulse group is 4
It consists of extremely short pulses with a pulse width of 1°2.3.4. In this embodiment, the interval A from pulse 2 to pulse 3 corresponds to the outer diameter of the object 6 to be measured.

Further, the interval from pulse 1 to pulse 4 corresponds to one scanning time of the laser beam.

On the other hand, the clock pulses output from the oscillator 11 are transmitted to the counting circuit 12 and counted there. This count value is transmitted to the latch circuit 2o as a count signal. The latch circuit 20 latches this count signal based on the output pulse group of the pulse converter 19. The latched count signal is transmitted to the correction circuit 21, and as shown in FIG. Based on the difference (c) between the counts of pulse 2 in the pulse group, the difference (a) between the counts of pulse 2 and pulse 3, which is the outer diameter of the measurement object 1716, is corrected.

In other words, the difference between the count values of pulse 2 and pulse 2 is:
It fluctuates in response to fluctuations in the rotational speed of the motor and displacement of the object 6 to be measured. This difference becomes larger due to a delay in the rotational speed of the motor or a movement of the object to be measured 6 in the laser beam scanning direction (downward in FIG. 1). On the other hand, this difference C becomes smaller by increasing the rotational speed of the motor or by moving the object to be measured 6 in a direction opposite to the laser beam scanning direction. Therefore, by comparing this difference C with the standard set value, the fluctuation in the rotation speed of the motor and the displacement of the object 6 to be measured are detected, and based on that, the pulse 2 and the pulse corresponding to the outer diameter of the object 6 to be measured are detected. By correcting the difference A in the count values of 3, it is possible to accurately measure the outer diameter of the object to be measured.

In this example, the difference between the count values of pulse 2° and pulse 2 was used to correct measurement errors due to fluctuations in motor rotation speed, etc., but other pulses in the pulse group may also be used. . However, the method of this embodiment is the most suitable one for reasons that will be explained later.

First, in the method of using pulses 1 and 1 or pulses 4 and 4, which correspond to each other in the pulse group, as explained in the conventional example, the diameter of the scanning beam is the same as that between the collimator lens 4 and the condenser lens. Since the distance from the center of the light receiving element 5 increases, the rise and fall of the light receiving signal a of the light receiving element 7 become somewhat slow, resulting in inaccurate measurements compared to this embodiment.

Next, the method using pulse 3 and pulse 3° corresponding to the pulse group is suitable for measuring the outer diameter of the object to be measured or the diameter of the hollow part of the ring-shaped object. does not cause any problems.

However, a problem arises when simply measuring the position of the edge of the object to be measured. That is, in this case, the pulse variation JA
The output pulse group of the device 19 generates only two pulses in one scan. Therefore, since the third pulse is not generated, this method cannot be used for the above purpose.For more than one reason, it is difficult to perform the correction using the second pulse of the pulse group in any measurement. It is also ideal when performing this as a target.

In this example, the measurement error was corrected using the pulses of the corresponding pulse groups of the previous scan and the current scan. There is no need to compare with previous scans.

〔Effect of the invention〕

As is clear from the above description, the present invention scans the light from the light emitting element multiple times, and the light receiving element that is generated by the shielding of the measurement object placed between the light emitting element and the light receiving element. In a scanning optical edge discriminator that determines the edge of the object to be measured from an output signal, an oscillation circuit that outputs a clock pulse and a rising edge of output No. 8 of the light receiving element at the edge of the object to be measured are provided. and a binarization circuit that outputs a pulse in accordance with the falling edge of the clock pulse, a latch circuit that latches this pulse based on the clock pulse, and an output signal of this latch circuit that outputs a pulse in accordance with the current scan and the current scan. Since a correction circuit is provided for correction based on the output signal of the latch circuit, even if fluctuations in the rotational speed of the motor or displacement of the object to be measured occur, the number of parts will increase and the configuration will become more complicated. Therefore, it is possible to accurately measure the edge of the object to be measured. Therefore, since it is possible to use an inexpensive motor, a reduction in cost can be achieved. Note that it is possible to correct measurement errors due to displacement of the measurement object itself, which was difficult to correct even with the use of an expensive motor in the past. Further, since the measurement is performed using the light from the light projecting element with a small diameter, more accurate measurement is possible. Furthermore, since the fluctuation of the motor rotation speed and the displacement of the object to be measured are essentially equivalent,
Even if these occur simultaneously, it is possible to correct the measurement error.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams of one embodiment of the scanning optical end discriminator according to the present invention, FIG. 1 is a functional explanatory diagram of this embodiment, and FIG. 2 is an explanatory diagram of this embodiment. The operation waveform diagrams of each part, FIGS. 3 and 4 are explanatory diagrams of a conventional example. FIG. 3 is a diagram explaining the principle of the scanning type optical outer diameter measuring instrument, and FIG. 4 is a diagram explaining the functions of the scanning type optical outer diameter measuring instrument with a correction function. l... Laser tube (light emitting element), 3... Rotating mirror,
6... Measurement object, 7... Light receiving element, 8... Amplifier (binarization circuit), 11... Oscillator circuit, 19... Pulse converter (binarization circuit), 20... ...Latch circuit, 2
1... Correction circuit.

Claims (2)

[Claims] (1) The light from the light emitting element is scanned multiple times, and the output signal of the light receiving element generated by the shielding of the measurement object placed between the light emitting element and the light receiving element is detected at the edge of the object to be measured. A scanning optical edge discriminator for discriminating an object includes: an oscillation circuit that outputs a clock pulse; and a binary circuit that outputs a pulse in response to the rise and fall of an output signal of the light receiving element at the edge of the object to be measured. a latch circuit that latches this pulse based on the clock pulse, and a correction circuit that corrects the output signal of this latch circuit for each scan by the output signal of the latch circuit of the scan before the current scan and the current scan. A scanning optical end discriminator comprising: (2) Scanning according to claim 1, which is a correction circuit that corrects the pulse output in response to the falling edge of the first light reception signal in one scan by the number of clock pulses from the previous scan to the current scan. Type optical end discriminator.