JPH0829131A - Optical measuring apparatus - Google Patents

Abstract

PURPOSE:To perform a highly accurate measurement for the part between the outer pattern of a substance to be measured and the step difference in the longitudinal direction by moving the substance to be measured in the direction perpenticualarly intersecting parallel scanning light rays, and measuring the distance between the step differences in the moving direction of the substance to be measured. CONSTITUTION:A polyhedron rotary mirror 3 is controlled to the specified number of rotation and rotated with a motor driving circuit 8. Light rays 2 projected based on a synchronous signal 10 have the constant scanning angles with the mirror 3 and are converted into parallel scanning light rays 6 having the effecting measuring range. After the scanning for the constant distance, the light rays 6 are condensed with a collimator lens 11 and converted into a received signal 13 with a light receiving circuit 12. A substance to be measured 9 is positioned in the effective range of the light rays 6 between the collimater lenses 5 and 11, and moved so as to cintersect the scanning direction at a right angle. The difference between bright and dark intensities of the lights, which are screened with the light rays 6, is operated with an outer-pattern measuring part 22. The distance between the step differences is operated from the moving speed of the substance to be measured 9 by recognizing the intermediate level of the intensity of the light at the step difference part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical measuring device for measuring the outer shape or the like of an object to be measured using parallel scanning light rays.
In particular, the present invention relates to an optical measuring device capable of accurately measuring a distance between steps of an object to be measured in a direction orthogonal to the scanning direction of parallel scanning light rays.

[0002]

2. Description of the Related Art Conventionally, in order to measure the outer shape in the width direction and the longitudinal direction of an object to be measured, the object to be measured is scanned with a parallel scanning light beam, and the parallel scanning light beam is blocked by the object to be measured. 2. Description of the Related Art There is known an optical measuring device that measures the outer dimension of an object to be measured according to the length of time in a dark area. As an example of a light projecting device used for this optical measuring device, the light projecting device is
It is composed of a light source, a polyhedral rotating mirror that converts a light beam from the light source into a fan-shaped rotation scanning light beam, and a collimator lens that converts the rotation scanning light beam into a parallel scanning light beam. The light beam emitted from the light source is projected on all surfaces of the polyhedral rotating mirror that rotates at a constant speed and at high speed. The light beam reflected by the polygon mirror rotating mirror is converted into a rotational scanning light beam, and a parallel scanning light beam is obtained through a collimator lens. The effective measurement range of the parallel scanning light beam is determined by the optical design of the collimator lens and the polyhedral rotating mirror.

In the above apparatus, the outer shape of the object to be measured can be measured by positioning the object to be measured within the effective measurement range of the parallel scanning light beam. That is, as shown in FIG. 3 as an example of the object to be measured, when the object to be measured is a shaft having steps 30, 31, the diameter d of the shaft is within the effective measurement range L of the parallel scanning light beam 6. The diameter d can be measured. When measuring the distance e between the steps, which is the outer shape in the longitudinal direction of the object to be measured, the object to be measured is rotated to be positioned in the longitudinal direction, but the effective measurement range L of the parallel scanning light beam 6 is L.
The object to be measured cannot be measured with the above distance between the steps. Further, as shown in another example of the object to be measured in FIG. 4, when the steps 32, 33 of the shaft or the like have a shape that becomes narrow in one direction, the diameter d of the shaft can be measured as in FIG. The parallel scanning light beam 6 for measuring the distance f between the steps
Even if is scanned in the longitudinal direction of the object to be measured, the step 33 is not recognized and the distance f cannot be measured.

In order to measure the steps of these objects to be measured in a non-contact manner, image processing is performed using another measuring device such as a CCD camera to detect the steps of the objects to be measured. By combining the optical measuring device and the CCD camera, it becomes possible to measure the outer shape of the object to be measured and the distance between the steps.

[Problems to be Solved by the Invention]

As described above, in order to measure an object to be measured that has a complicated shape and is long in the axial direction, it is necessary to use different measuring devices in combination or to construct a system combining these. I won't. For this reason,
The equipment or system becomes complicated and expensive. Further, in order to measure the step of the shaft by the optical measuring device, the effective measurement range of the parallel scanning light beam must be widened, and the device main body becomes large as the collimator lens and the polyhedral rotating mirror become large. .

Further, as shown in FIG. 5, the mirror surface of the polyhedral rotating mirror 3 arranged in the optical measuring device has a surface tilt θ due to manufacturing variations and the like. For this reason,
The light beam 2 projected on the polygon mirror rotating mirror 3 is reflected as a rotational scanning light beam 4 at an angle of 2θ. Since the surface tilt of each mirror surface is unique, when the rotary scanning light beam 4 is converted into the parallel scanning light beam 6 by the collimator lens or the like, the parallel scanning light beam 4 is not irradiated from a certain position, and the parallel scanning light beam is scanned in the scanning direction. On the other hand, an error occurs in the direction orthogonal to the above.

The present invention has been made in view of the above-mentioned problems, and the outer shape of the object to be measured located within the effective measurement range of the parallel scanning light beam and the parallel scanning light beam of the parallel scanning light beam are measured by using only one optical measuring device. An object of the present invention is to provide a compact and low-priced optical measuring device that enables highly accurate measurement of a distance between steps of a measured object in a direction orthogonal to the scanning direction.

[0008]

In order to solve the above-mentioned problems, the present invention converts a light beam emitted from a light source into parallel parallel scanning light beams in a certain scanning range by an optical scanning device, and converts the parallel scanning light beam. The object to be measured is located within the effective measurement range, and the light receiving device detects a light receiving signal of a length of time of a bright portion or a dark portion in which the object to be measured has a parallel scanning light beam, and the parallel scanning light beam of the object to be measured is detected. In the optical measuring device for measuring the dimension in the scanning direction, the moving means for moving the object to be measured in the direction orthogonal to the parallel scanning light beam and the distance between the steps in the moving direction of the object to be measured are The measuring means is provided, and the measuring means recognizes a received signal in which the light intensity of the parallel scanning light beam stays at an intermediate level when the parallel scanning light beam passes through the step, and measures the moving distance of the measured object. Constant to and measuring the distance between the step. More specifically, the step detecting means includes a peak hold circuit for detecting an upper limit output signal, a bottom hold circuit for detecting a lower limit output signal, a window comparator for comparing whether the received light signal is within a window, and a window. And a filter circuit that outputs an output signal when the light receiving signal of the intermediate level is stagnant for a predetermined time.

Further, the optical scanning device has a polyhedral rotating mirror for converting a light beam from a light source into a rotational scanning light beam, and selects at least one mirror surface of the polyhedral rotating mirror to be specified, and the mirror surface is selected. Is used as a parallel scanning light beam for detecting the step, and an N-ary counter and a gate circuit are provided as selecting means of a mirror surface used for detecting the step. The optical scanning device and the light receiving device are moved to the moving means to measure the size of the object to be measured and the distance between steps.

[0010]

In this structure, the light beam emitted from the light source controlled by the synchronizing signal is reflected by at least one surface of the polyhedral rotating mirror rotating at a predetermined rotation speed and converted into a rotational scanning light beam. Then, the rotary scanning light beam is converted into a parallel scanning light beam in the effective measurement range by the collimator lens and scanned toward the light receiving device. The object to be measured is positioned within the effective measurement range of the parallel scanning light beam, and the light receiving signal corresponding to the bright portion or the dark portion blocked by the object to be measured is detected to measure the outer dimension of the object to be measured.

On the other hand, in order to measure the distance between the steps of the object to be measured, the object to be measured is moved at a predetermined speed in a direction orthogonal to the scanning direction of the parallel scanning light beam. The parallel scanning light beam is scanned while moving the object to be measured, and the beam diameter of the parallel scanning light beam detects the relationship between the light intensity blocked by the object to be measured and time. When reaching the position of the step of the object to be measured, the beam diameter of the parallel scanning light beam is blocked by the step almost half with respect to the moving direction of the object to be measured. Therefore, the light intensity maintains the intermediate level. By detecting this intermediate level signal, the step difference of the object to be measured is recognized and the distance between the step differences is measured.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings. As shown in the perspective view of FIG. 2, the optical measuring device according to the present invention includes an optical scanning device 36, a light receiving device 37, and a direction (arrow X) orthogonal to the scanning direction of the parallel scanning light beam 6.
Direction) and moving means for moving the object to be measured at a predetermined speed. Optical scanning device 36 and light receiving device 37
Has a control circuit for controlling the parallel scanning light beam 6 incorporated therein or is connected to an external control circuit.

FIG. 1 shows a block diagram of the above-mentioned optical measuring device. The optical scanning device 36 synchronizes with the laser light source 1 that emits a laser beam 2 based on a signal output from a light emission control circuit 38 described later, the polyhedral rotating mirror 3 that rotates at a predetermined rotation speed by a motor drive circuit 8, and the synchronization. And a collimator lens 5 for converting the fan-shaped rotating scanning light beam 4 reflected and scanned by the polyhedral rotating mirror 3 into a parallel scanning light beam 6.

Light receiving device 3 of the optical measuring device according to the present invention
Reference numeral 7 denotes a collimator lens 11 that collects the parallel scanning light beam 6.
And a light receiving circuit 12 for converting the light beam condensed by the collimator lens 11 into a light receiving signal 13 according to the brightness of the light.

The control circuit of the optical measuring apparatus according to the present invention comprises an outer shape measuring section 22 for measuring the outer shape of the object 9 to be measured in the scanning direction of the parallel scanning light beam 6 and a direction (object to be measured) orthogonal to the parallel scanning light beam 6. Measured object 9 (moving direction of measured object 9)
Step distance measuring circuit 39 for measuring the step 30 (31) of the
Consists of The step distance measuring circuit 39 includes a peak hold circuit 15 that detects an upper limit output signal and a bottom hold circuit 16 that detects a lower limit output signal. Light reception signal 13 transmitted from light receiving device 37 by these circuits
It sets a reference level for comparison with. Further, the step distance measuring circuit 39 has a window with respect to the center value of the reference level, and the window comparator circuit 17 for comparing whether the received light signal 13 is in the window, and the received light signal 13 is stagnant in the window. The filter circuit 18 outputs an output signal according to a set value of time. Further, the control circuit has a gate circuit 21 and a counter 14 for selecting a parallel scanning light beam from a specific surface of the polyhedral rotating mirror.

With such a configuration, the principle of measuring the outer shape of the parallel scanning light beam 6 on the object to be measured 9 in the scanning direction and the step difference e in the direction orthogonal to the parallel scanning light beam 6 will be described. A case of measuring the outer shape of the DUT 9 will be described with reference to FIG. By positioning the DUT 9 within the effective measurement range L of the parallel scanning light beam 6 scanned by the optical scanning device 36, a shadow d blocked by the DUT 9 is formed. The outer shape of the DUT 9 can be measured by obtaining the time length of the dark portion or the light portion of the received light signal 13 by the outer shape measuring unit 22 with the synchronization signal 10 as a reference.

Next, the measurement of the step distance in the direction orthogonal to the parallel scanning light beam 6 on the object to be measured 9 will be described.
FIG. 6 shows an enlarged view of the step portion of the DUT 9. In the figure, a state in which the parallel scanning light beam 6 is scanned from the top to the back as the diameter of the scanning beam at regular time intervals from the top is shown. The DUT 9 is moving in the arrow X direction at a constant speed on a stage (not shown) as a moving unit. Parallel scanning light beam 6a,
6c is not located on the stepped portion of the DUT 9, and the parallel scanning light beam 6b is located on the stepped portion. 7 (a), (b), and (c) show the relationship between the light reception level and time at each position of the parallel scanning light beams 6a, 6b, and 6c shown in FIG. Level and time are plotted on the horizontal axis. For example, the light receiving level is 10 at a position where the scanning beam is not blocked by the DUT 9.
0% is shown, and the light reception level is 0% at the position where the scanning beam is blocked by the object to be measured. As shown in FIGS. 7A and 7C, the light reception signals 13A and 13C of the bright portion and the dark portion according to the outer shape of the DUT 9 are obtained. Here, the time of the dark portion corresponding to the diameter d of the DUT 9 in FIG. 6 is d in FIG.
The time in the dark portion corresponding to the diameter g of the object to be measured is indicated by g in FIG. 7 (c). Further, as shown in FIG. 7B, the scanning beam of the parallel scanning light beam 6b located at the step portion is not completely shielded due to the step, and the light reception signal level is as shown at the point Y during the time spent on the step portion. Stagnate. Therefore, it is possible to recognize the step portion of the DUT 9 by detecting that the received light signal 13 becomes the graph of FIG. 7B.

A preferred control method for recognizing the step portion of the object 9 to be measured will be described. The peak hold circuit 15 and the bottom hold circuit 16 set a reference level for comparison with the received light signal 13. It is compared whether the center value of the reference level is within the window range of the window comparator circuit 17. The compared light receiving signal 13 passes through the filter circuit 18, and is output as an output signal only when the light receiving signal 13 is present in the window for a set time or longer, and the step is recognized.

The width of the window can be determined from the required measurement accuracy. For example, when the beam diameter of the parallel scanning light beam is 0.5 mm and the accuracy of the step difference is 10 μm, the width of the window needs to be set to about 2%. That is, by setting the allowable range of the intermediate level to be 49% to 51% and outputting the time when the light receiving level is stagnant during this period as an output signal, the accuracy of 10 μm can be guaranteed.

The stagnation time set by the filter circuit 18 can be determined from the minimum level difference detected. For example, if the minimum step of the object to be measured is 1 mm and the scanning speed of the parallel scanning light beam is 100 mm / sec, the stagnation time at the intermediate level is set to less than 10 msec. If the stagnation time of the intermediate level is set to 10 msec or more, 1 m
It becomes impossible to recognize the step of m. The step is
To be precise, it is measured based on the resultant force between the scanning speed of the parallel scanning light beam 6 and the moving speed of the measured object, but the moving speed of the measured object 9 is sufficiently slower than the scanning speed of the parallel scanning light beam 6. Therefore, the moving speed of the DUT 9 can be practically ignored and the measurement can be performed.

A suitable control method for eliminating the influence of the surface tilt of the polyhedral rotating mirror 3 will be described. A light beam 2 emitted from a light source 1 is reflected by a polyhedral rotating mirror 3 and converted into a fan-shaped rotating scanning light beam 4. A part thereof is sent to the light receiving element 7 for synchronization, controlled by the light beam emission control circuit 38, and the timing of the light beam 2 emitted from the light source 1 is adjusted. Thus, the scanning angle of the polyhedral rotating mirror 3 is controlled to control the parallel scanning light beam 6 within a predetermined effective measurement range. In the above-mentioned state, the light beam 2 from the light source 1 is projected onto each mirror surface of the polyhedral rotating mirror 3, and the influence of surface tilt inherent in each mirror surface occurs. Therefore, the synchronization signal 10 is counted by the N-adic counter 14 to count N synchronization signals 10 corresponding to the number of mirror surfaces of the polyhedral rotating mirror 3,
The gate circuit is released individually. In the embodiment, since the six-sided rotating mirror is used, the N-ary counter counts every six and the gate circuit 21 is released. As described above, since only one surface of the polyhedral rotating mirror 3 is used, it is possible to eliminate the influence of surface tilt. Also, N
By controlling the count number of the advance counter, the number of mirror surfaces to be used can be set and a desired use environment can be set.

Next, the measuring operation will be described with reference to FIG. The polyhedral rotating mirror 3 is controlled by a motor drive circuit 8 to rotate at a predetermined number of rotations. The light beam 2 from the light source 1 is projected on the polygon mirror rotating mirror 3 based on the synchronization signal 10 set by the control method described above. The light beam 2 thus projected is converted into a rotary scanning light beam 4 having a constant scanning angle by the polyhedral rotating mirror 3, and is converted into a parallel scanning light beam 6 having a desired effective measurement range through the collimator lens 5. The parallel scanning light beam 6 is condensed by the collimator lens 11 after scanning a certain distance.
The light receiving circuit 12 converts the received signal 13 into a received signal 13.

On the other hand, the object to be measured is the collimator lens 5,
Located within the effective measuring range of the parallel scanning light beam 6 between 11
The parallel scanning light beam 6 moves at a constant speed in a direction orthogonal to the scanning direction. On the basis of the above-described measurement principle, in the contour measurement of the DUT 9, the contour measurement unit 22 calculates the difference in the light intensity of the bright portion or the dark portion interrupted by the parallel scanning light beam 6, and the result is displayed on a display device (not shown). In addition, the DUT 9
The step-to-step distance is measured by recognizing the intermediate level of the light intensity in the step portion, detected by the filter circuit 18, and calculated from the moving speed of the DUT 9 by an arithmetic circuit (not shown). Is displayed in.

In the embodiment, the bottom hold circuit 16 is used to cancel the drift of the reference potential of the light receiving circuit 12, so-called offset drift. However, if it is confirmed that the offset drift is sufficiently small, the bottom hold circuit 16 can be omitted, and a reference level for comparison is set between the output of the peak hold circuit 15 and the reference potential. It becomes possible.

Although the window comparator circuit 17 is composed of an open collector output type comparator, it may be composed of a known type of comparator. Further, although the filter circuit 18 for detecting the stagnation time at the intermediate level is an analog filter, it may be a digital filter using a counter and a reference clock.

Furthermore, although the filter circuit 18 is provided in the preceding stage of the gate circuit 21, the same effect can be obtained by providing it in the latter stage of the gate circuit 21.

The light beam 2 emitted from the light source 1 used in the present invention is preferably a laser beam in the visible light region, and examples thereof include a semiconductor laser. Also, L
It is also possible to use an ED light source or the like, and it is also applied to light rays outside the visible light region. In addition, the present invention can also measure the eccentricity of the shaft axis by scanning the parallel scanning light beam 6 while rotating the shaft, which is the object to be measured, in the above-described measuring method and rotating the shaft in the axial direction to calculate the light intensity. Become.

[0028]

According to the present invention, the optical measuring device having only one parallel scanning light ray enables non-contact measurement of the contour of the object to be measured and the step-to-step distance measurement by detecting the step difference. Since it is not necessary to add a device, the device can be downsized and the cost can be reduced. Further, by using at least one surface of the polyhedral mirror, it becomes possible to scan the parallel scanning light beam from a predetermined position, and the measurement accuracy of the optical measuring device is improved.

Further, the width of the window and the filter circuit can be set so as to be measured with desired accuracy. For example, the surface roughness of the object to be measured, the accuracy of the step, etc.
The measurement accuracy can be freely selected for the measurement environment of the object to be measured.

[0034]

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an optical measuring device according to the present invention.

FIG. 2 is a perspective view of an optical measuring device according to the present invention.

FIG. 3 is a diagram showing an example of an object to be measured.

FIG. 4 is a diagram showing another example of the object to be measured.

FIG. 5 is a diagram showing a state in which a polyhedral rotating mirror is tilted.

FIG. 6 is a diagram showing a state in which the object to be measured is scanned with parallel scanning light rays.

FIG. 7 is a diagram showing a relationship between a light reception level of a parallel scanning light beam and time.

[Explanation of symbols]

 1 Light Source 2 Rays 3 Polyhedral Rotating Mirror 4 Rotating Scanning Rays 5 and 11 Collimator Lens 6 Parallel Scanning Rays 7 Synchronous Light-Receiving Element 8 Motor Drive Circuit 9 DUT 10 Synchronous Signal 12 Light-Receiving Signal 13 Counter 15 Peak-Holding Circuit 16 Bottom hold circuit 17 Window comparator circuit 18 Filter circuit 21 Gate circuit 22 Outer shape measuring section 30 to 33 Step 36 Optical scanning device 37 Light receiving device 38 Ray emission control circuit 39 Distance measuring circuit between steps

Claims (5)

[Claims] 1. A light scanning device converts a light beam emitted from a light source into parallel parallel scanning light beams having a constant scanning range, and positions the measured object within an effective measurement range of the parallel scanning light beam to measure the measured object. In the optical measuring device for detecting the light receiving signal of the time length of the bright portion or the dark portion in which the parallel scanning light beam is blocked by the light receiving device, and measuring the dimension of the measured object in the scanning direction of the parallel scanning light beam, A moving means for moving the object to be measured in a direction orthogonal to the parallel scanning light beam and a measuring means for measuring a distance between steps in the moving direction of the object to be measured are provided. When the light beam passes through the step, the received signal in which the light intensity of the parallel scanning light beam stagnates at an intermediate level is recognized, and the moving distance of the measured object is measured to measure the distance between the steps. Do Optical measuring device. 2. A means for detecting the step, a peak hold circuit for detecting an upper limit output signal, a bottom hold circuit for detecting a lower limit output signal, and a window comparator for comparing whether the received light signal is within a window, The optical measuring device according to claim 1, further comprising: a filter circuit that outputs an output signal when the received light signal at the intermediate level is stagnant for a predetermined time in the window. 3. The optical scanning device has a polyhedral rotating mirror that converts a light beam from a light source into a rotational scanning light beam, and selects at least one mirror surface of the specified polyhedral rotating mirror, and the mirror surface is selected. The optical measuring device according to claim 1 or 2, wherein the light beam from is used as a parallel scanning light beam for detecting the step. 4. The optical measuring device according to claim 1, further comprising an N-ary counter and a gate circuit as a mirror surface selecting unit used for detecting the step. 5. The optical measurement according to claim 1, wherein the moving means moves the optical scanning device and the light receiving device to measure the size of the object to be measured and the distance between steps. apparatus.