JPS62105005A - Optical measuring instrument - Google Patents

Abstract

PURPOSE:To smooth mutual high-speed/low-speed switching and to correct a cumulative error by specifying the phase of next excitation based on the current excitation phase of a stepping motor and information of a driving program and also correcting the position shift of a mount table. CONSTITUTION:An enlarged image of an object of measurement on a mount table which is moved by a driving device is obtained through an optical system and an edge detecting circuit 22 finds its edge to find the shape, size, etc., of the object of measurement. A high-speed driving circuit 42 which drives a stepping motor 41 coupled with the driving shaft of the mount table at intervals of a reference step angle and a low-speed driving circuit 43 which drives it at intervals of a mini step angle are switched by a drive switching circuit 44 to drive the motor. The current excitation phase of the motor 41 is detected by a current phase detecting circuit 45 and compared with the information of the drive program and a next phase specifying circuit 46 specifies the starting excitation phase of a next process by the high-speed or low-speed driving circuit 42 or 43. Further, the number of driving pulses is corrected corresponding to the position shift of the current position from a command position by a displacement detecting device to correct the cumulative error.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical measuring device that measures the shape, dimensions, etc. of a measurement target by evaluating an enlarged image of the measurement target. Specifically, the present invention relates to an improvement in a drive device that drives a stage on which a measurement target is placed so as to automatically select a measurement region of an enlarged image to be evaluated.

[Background technology and its problems]

Optical measuring devices optically magnify all or part of the object to be measured on the stage and evaluate the enlarged image to measure the shape and dimensions of the object. Due to its advantages, it is becoming more and more popular in the era of precision.

Conventionally, such an optical measuring device, for example, in the case of a magnifying projector, includes a stage on which the object to be measured is placed, a displacement detection device that detects the amount of movement of the stage, and a position on the stage. A magnifying optical system that optically magnifies the object to be measured and projects it onto a screen, an edge detection circuit that detects the edges of the enlarged image obtained by this expanding optical system, and an edge detection circuit that detects the shape and dimensions of the object to be measured. It consists of a measuring circuit that performs calculations and an output device that displays or prints the shape, dimensions, etc. determined by this measuring circuit. When the enlarged image of the object to be measured crosses the edge detection sensor, the predetermined dimensions of the measurement step are automatically calculated from the edge detection signal output from the edge detection circuit and the output signal of the displacement detection device. It looks like this.

In order to operate this type of measurement device efficiently, it is necessary to speed up the movement of the magnified image, that is, the movement of the stage in the case of a magnification projector, and to speed up the movement of the magnified image, and to also speed up the movement of the stage in the case of a magnification projector. , the edge detection direction, the number of pieces to be measured, the dimension calculation method, etc. are determined for each measurement step).

For this reason, it has been proposed that a drive device for moving the stage be composed of a DC servo motor, a step motor, or the like.

By the way, this type of measuring device does not precisely control positioning to a target value like an NC@ machine, but rather controls a wide range of rough target areas that include the target value if! It is generally advantageous to employ a step motor in terms of drive control, since there are reasons specific to the measuring device that must be controlled, and an oven loop is sufficient.

However, the conventional drive device employing a step smoke has the following problems.

■For example, the step angle per pulse is 1°8@1
- When using the two-phase excitation force method, the moving speed is proportional to the number of pulses supplied per unit time, but the target value is not fixed, so know when to slow down the pulse supply cycle and slow amplify. is difficult. As a result, if the timing of switching to slowdown is too early, the low-speed movement period is long and workability is lacking, while if it is too late, the speed at which the edge detection area passes is too fast, resulting in failure to detect.

■The 1-2 phase excitation method described above has a large step angle of 1.8° per pulse and a coarse movement resolution, which narrows the range in which edges can be detected and limits the objects to be measured to which it can be applied. This caused vibrations during low-speed movement and reduced edge detection accuracy.

Furthermore, since the excitation method uses a constant current chopper, heat is generated due to the constant flow of the rated current, so a special burden must be placed on the structure of the measuring device itself to avoid this effect. This problem becomes worse as the speed increases, resulting in larger current or lower torque due to changes in internal inductance.

■On the other hand, in order to solve the above-mentioned problems ■ and ■, a so-called mini-step drive method is known in which the current ratio of adjacent coils is changed stepwise and the step angle is made smaller. In this case, the original high speed cannot be achieved,
It was only used in extremely small measuring devices.

[Purpose of the invention]

Here, the purpose of the present invention is to solve a problem inherent in measuring devices, that is, in general, switching from high speed to low speed and from low speed to high speed is performed in the same direction, whereas in a measuring device, the changeover must simultaneously move in the opposite direction. The object of the present invention is to solve the above-mentioned problems while taking into consideration the problem that the movement of the robot may sometimes occur, and the problem that an accumulated error occurs in the actual movement position relative to the commanded position due to the open loop control.

[Means and actions for solving problems] Therefore,
The present invention includes a workpiece table that is moved by a drive device, a displacement detection device that detects the amount of movement of the workpiece table, and an optical system that obtains an enlarged image of the object to be measured on the workpiece table. An optical measuring device comprising an edge detection circuit for detecting edges of an image, and configured to determine the shape, dimensions, etc. of an object to be measured using output signals from both the displacement detection device and the edge detection circuit, The drive device includes a step motor connected to a drive shaft of the object table, a high-speed drive circuit that advances the step motor by a reference step angle, and a low-speed drive circuit that advances the step motor by mini-step angles smaller than the reference step angle. a drive switching circuit that switches between the high-speed drive circuit and the low-speed drive circuit based on commands of a drive program; a current phase detection circuit that detects the current excitation phase of the step motor; and a current phase detection circuit that detects the current excitation phase of the step motor. a next phase specifying circuit that compares the excitation phase with the next process command information of the drive program to specify the initial excitation phase of the next process by the high speed drive circuit or the low speed drive circuit; A correction means is provided for correcting the number of drive pulses for the next process supplied to the high-speed drive circuit or the low-speed drive circuit by a number equivalent to the positional deviation between the current position of the stage and the command position detected by the displacement detection device. It is characterized by

In short, the high-speed drive circuit and low-speed drive circuit that drive the step motor are switched based on the commands of the drive program, the current excitation phase of the step motor at this time is detected by the current excitation phase detection circuit, and this and the information of the drive program are combined. The next phase of the step motor to be excited is determined from the information, thereby smoothly switching from high speed to low speed and from low speed to high speed, solving each of the above problems. The number of drive pulses is corrected by the number equivalent to the positional deviation between the command position and the command position, thereby correcting the cumulative error.

〔Example〕

An embodiment in which the present invention is applied to an enlarged projection apparatus will be described below. FIG. 1 shows the front of the entire apparatus, and FIG. 2 shows the side of the projector body.

The device includes a projector main body 11, a control box 21 that controls the driving of the movable parts of the projector main body 11, and a control box 21 that moves the movable parts in a preset order while making measurements. It consists of a data processing device 31 that calculates the shape, dimensions, etc. of an object.

The projector main body 11 includes a stage 1 on which an object to be measured is placed.
2, a screen 13, and a screen 1 that magnifies the reflected light or transmitted light from the object to be measured on the document table 12.
and an enlargement optical system 14 for projecting the image onto 3. Loading table 12
As shown in FIG. 3, the X-table 15 is moved in the axial direction (X-axis direction) orthogonal to the optical axis by the X-axis drive device 23, and the optical axis and It includes a Y table 16 that is moved in an axial direction (Y-axis direction) perpendicular to the X-axis. Each of these tables 15.
The displacements of 16 are detected by the respective displacement detection devices 17 and 18, and then provided to the data processing device 31. As shown in FIG. 4, each displacement detection device 17.18 detects the relative distance between the main scale provided on one of the fixed side member and each table 15.16 and the index scale provided on the other. An amplifier 20A that amplifies the signal from the detection head 19 that detects the amount of movement as an electrical signal, a waveform shaping circuit 20B that shapes the output from the amplifier 20A, and a counter that counts the signal from the waveform shaping circuit 20B. 20C.

The control box 21 is provided with an edge detection circuit 22 in addition to the X-axis drive device 23 and the X-axis drive device 24. The edge detection circuit 22 detects an edge of an enlarged image by capturing a change in light N detected by an edge detection sensor 22A, for example, and detects an edge of an enlarged image.
When the edge of the enlarged image of the object to be measured passes through the edge detection sensor 22A, an edge detection signal is provided to the data processing device 31.

The data processing device 31 includes a keyboard 32 and a CRT.
33 and a data processing section 34. Data processing section 34
When the X table 15 and the Y table 16 are driven via the X axis drive device 23 and the Y axis drive bag N24 according to a preset drive program, and an edge detection signal is given from the edge detection circuit 22, ,
X-axis displacement detection device 17 and Y-axis displacement detection device 18
The data from the CRT 33 are taken in, the shape and dimensions of the object to be measured are calculated based on these data, and the results are output to the CRT 33.

FIG. 4 shows a specific circuit configuration of the data processing section 34 and the X-axis drive device 23. Note that since the X-axis drive device 24 and the X-axis drive device 23 have the same configuration, only the X-axis drive device 24 will be described in the following description.

The data processing unit 34 drives the memories 6IA and 61B that store preset measurement programs and drive programs, and drives the drive values 223 and 24 based on the programs in these memories 61A and 61B. Detection signal and displacement detection device! 17
．． The central processing unit 62 includes a central processing unit 62 that calculates the shape, dimensions, etc. of the object to be measured based on data from the After stopping, when moving to the next target position,
A correction means is added that corrects the number of drive pulses required to reach the target position by the number equivalent to the positional deviation between the current position of the table 17.18 detected by the displacement detection device 17.18 and the command position. .

The X-axis drive device 23 includes a step motor 41 connected to the feed screw shaft 15A, which is the drive shaft of the X-table 15.
a high-speed drive circuit 42 that advances the step motor 41 by a reference step angle in response to drive pulses provided from the central processing unit 62 of the data processing unit 34; a low-speed drive circuit 43 that advances the step motor 41 by mini-step angles smaller than a reference step angle in response to drive pulses generated by the drive; and a drive switch that switches between the high-speed drive circuit 42 and the low-speed drive circuit 43 based on commands of a drive program. circuit 44, a current phase detection circuit 45 that detects the current excitation phase of the step motor 41, and this current phase detection circuit 4.
5 and the next process command information of the drive program given from the central processing unit 62 to identify the initial excitation phase of the next process by the high speed drive circuit 42 or the low speed drive circuit 43. It is composed of a specific circuit 46.

The high-speed drive circuit 42 includes a chopper high-voltage power supply 42A and a constant current chopper drive circuit 42B of a constant current excitation type in which the reference step angle of the step motor 41 is θm. In addition, the low-speed drive circuit 43 has a mini-step power supply 43A and a step angle of the step motor 41 that is smaller than the reference step angle θm.
A mini-step drive circuit 43 that excites the step motor 41 by switching stepwise the current ratio of the adjacent coils of the step motor 41 so as to obtain a mini-step angle θm dividing into n equal parts.
Including B.

As shown in FIG. 5, the mini-step drive circuit 43B is preset to a predetermined value by a preset signal given from the central processing unit 62 of the data processing section 34, and the number of drive pulses given from the data processing section 34 is set to the preset value. a ring counter 51 that re-counts each time the ring counter 51 reaches a count value of
A D/A converter 53 converts a digital signal output from the D/A converter 53 into a corresponding analog signal, and the drive switching circuit 44 amplifies the analog signal converted by the D/A converter 53.
and an amplifier 54 that applies voltage to a predetermined coil of the step motor 41 through the step motor 41. The output from the ring counter 51 is given to the current phase detection circuit 45 as position information for identifying the current excitation phase during low speed operation of the progressive motor 41 by the low speed drive circuit 43.

The current phase detection circuit 45 switches the drive switching circuit 44 to i during high-speed operation of the step motor 41 by the high-speed drive circuit 42.
il to detect the current excitation phase from the excitation phase of the step motor 41, while the mini-step drive circuit 43 detects the current excitation phase from the excitation phase of the step motor 41.
The current excitation phase is detected based on the position information from the ring counter 51 of B.

Next, the operation of this embodiment will be explained. Assume that, with the object to be measured set on the stage 12, the positional relationship between the magnifying optical system 14 for enlarging a part of the object and the stage 12 is in an initial state.

Here, when the first measurement step is selected from the measurement program stored in the memory 61A, the central processing unit 62
The constant current chopper drive circuit 42 of the high-speed drive circuit 42 sends a predetermined number of drive pulses and a rotation direction command corresponding to the distance to the next target value according to the corresponding drive program.
Give to B.

The constant current chopper drive circuit 42B performs double 1-2 phase excitation drive (0,
45°/pulse). Then, the step motor 41
By the rotation of the feed screw shaft 15A connected to the X-table 15, the X-table 15 is moved and moved at high speed in the X-axis direction.

Eventually, when the X-table 15 reaches a point predetermined by the drive program (before the edge detection point of the measurement target), the central processing unit 62 gives a switching command to the drive switching circuit 44, and switches from the high-speed drive circuit 42 to the low-speed drive circuit 42. At the same time, the high-speed drive circuit 42 stops sending drive pulses to the constant current chopper drive circuit 42B. Around this time, the current phase detection circuit 45 detects the drive switching circuit 44.
The current excitation phase of the step motor 41 is detected through the step motor 41, and this ii a is supplied to the next phase identification circuit 46. The next phase specifying circuit 46 specifies the next excitation phase from the information from the current phase detecting circuit 45 and the next process command information given from the central processing unit 62, and instructs the drive switching circuit 44 to specify the next excitation phase.

Here, the central processing unit 62 provides a drive pulse and a rotation direction command to the mini-step drive circuit 43B of the low-speed drive circuit 43. Then, the mini-step drive circuit 43B drives the step motor 41 at a low speed via the drive switching circuit 44 based on the number of drive pulses and the rotation direction command given from the central processing unit 62. As a result, the step motor 41 is smoothly switched from high speed to low speed without skipping pulses, and is moved at low speed without vibration or heat generation.

That is, the stop position of the step motor 41 is as shown in FIG.
As shown in A), in the case of double 1-2 phase excitation drive, the positions are 1 to I6 in the figure, but in the case of mini-step drive, one cycle is further subdivided, and the positions of double 1-2 phase excitation drive are There is also a stop position between the two stop positions.

Now, when switching from double 1-2 phase excitation drive to mini-step drive, if the drive of the step motor 41 is completed in the pull 1-2 phase excitation drive method, its stop position will be at any one of 1 to 16. It will stop at that position. If we stop at point A in Figure 6 (B), that point A is included in the stop position of the mini-step drive, so after setting the excitation pattern of the mini-step drive to the excitation pattern of the point A position, the high-speed From the drive circuit 42 to the low speed drive circuit 4
By switching to 3, it is possible to smoothly switch from high-speed movement to low-speed movement without skipping pulses in the commanded direction.

Conversely, when switching from mini-step drive to double 1-2 phase excitation drive, if the drive of the step motor 41 is completed in mini-step drive, temporarily A in FIG. 6(C)
Assuming that it stops at point °, when switching from mini-step drive to double 1-2 phase excitation drive, after setting the excitation pattern of double 1-2 phase excitation drive to stop position C or By switching from the low-speed drive circuit 43 to the high-speed drive circuit 42, it is possible to smoothly switch from high-speed movement to low-speed movement without skipping pulses in the command direction.

Now, during low-speed movement without vibration or heat generation, when the edge detection sensor 22A crosses a predetermined edge within the relevant measurement step of the enlarged image of the object to be measured, the edge detection circuit 22 detects the time of the crossing, An edge detection signal is provided to the central processing unit 62. Then, the central processing unit 62 determines the displacement detection device 17 at the time when the edge detection signal is applied.
．． 18 output signals are captured and stored. Then, after detecting the corresponding edges of the object to be measured in the same manner, the dimensions of the measurement point of the object to be measured are determined from the re-stored data, and this is displayed on the CRT 33. This completes the processing of the first measurement step.

Subsequently, when the second measurement step is selected from the measurement program stored in the memory 61A, the central processing unit 62
corrects the number of drive pulses supplied to the high-speed drive circuit 42 or the low-speed drive circuit 43 according to the corresponding drive program by the number equivalent to the positional deviation between the current position of the X-table 15 detected by the displacement detection device 17 and the program commanded position. After that, the corrected number of drive pulses and rotational direction command are given to the high speed drive circuit 42 or the low speed drive circuit 43.

Thereafter, the second measurement step is processed in the same manner as the first measurement step. In this case, the switching signal sent from the central processing unit 62 to the drive switching circuit 44 is also corrected by the number equivalent to the positional deviation between the current position of the stage 12 and the program commanded position.

In this way, measurements are carried out in the same manner up to the last measurement step, and the series of measurement operations is completed.

Therefore, according to this embodiment, for example, the current phase detection circuit 45 detects the current excitation phase of the step motor 41, and compares this with the next process command information to identify the initially excitation phase of the next process. Since the drive circuit 42 and the low-speed drive circuit 43 are switched, the above-mentioned conventional problem can be solved while also dealing with the problem unique to the measuring device that it may be necessary to move in the opposite direction at the same time as switching.

That is, high speed can be achieved by the high speed drive circuit 42, while during low speed operation by the low speed drive circuit 43, the step angle is small and high resolution movement is possible, so the edge detectable range is not limited and the edge detection accuracy is improved. The problem of vibration and heat generation can also be solved.

In addition, the current position of the table 15.16 detected by the displacement detection device 17.18 is compared with the command position, and the number of drive pulses in the next process is corrected by the amount of the positional deviation. This solves the problem inherent to measuring devices, that is, the problem of cumulative errors. This means that although the current position may exceed the commanded position due to cumulative errors, this can be kept at the target position, thereby shortening the movement trajectory and contributing to improving work efficiency.

In addition, in carrying out the present invention, the stage is not limited to the structure of the X, Y table described in the above embodiment, but may be any structure as long as it can move in at least one direction.

Furthermore, the displacement detection device is not limited to the photoelectric type described in the above embodiments, but may be of any type, such as an electromagnetic type or a capacitance type.

Furthermore, the edge detection circuit is not limited to the method of detecting the edges of the object to be measured from changes in the amount of light as described in the above embodiments, but any circuit that can detect the edges of the object to be measured without contact may be used. .

Furthermore, the step motor is not limited to the rotary type described in the above embodiment, but may also be a linear step motor.

Further, in the above embodiment, the current excitation phase of the step motor 41 is determined from the excitation phase of the step motor 41 during high speed operation by the high speed drive circuit 42, and from the position information from the ring counter 51 during low speed operation by the low speed drive circuit 43. Although the current excitation phase may be determined based on the number of supplied drive pulses based on the drive program.

Although the above embodiment describes an enlarged projection device, the present invention is not limited to this. For example, the present invention can be applied to an optical system that enlarges an object to be measured and evaluates the enlarged image to determine the shape, dimensions, etc. of the object. Can be applied to general type measuring devices.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to provide an optical measuring device that can achieve high-speed movement and low-speed, high-resolution movement while addressing the problems unique to optical measuring devices.

[Brief explanation of drawings]

The figures show one embodiment of the present invention, in which Fig. 1 is a front view showing the whole, Fig. 2 is a side view showing the main body of the projector, Fig. 3 is a block diagram showing the circuit configuration of the entire device, and Fig. 4 is a block diagram showing the main parts in FIG. 3, FIG. 5 is a block diagram showing a mini-step drive circuit, and FIG. 6 is an explanatory diagram of the operation of the step motor. 12... Stage, 14... Magnifying optical system, 15A...
- Feed screw shaft as a drive shaft, 17... X-axis displacement detection device, 18... Y-axis displacement detection device, 22... Edge detection circuit, 23... X-axis drive device, 24 ...
Y-axis drive device, 31...data processing device, 41...
・Step motor, 42...High speed drive circuit, 43...
-Low speed drive circuit, 44... Drive switching circuit, 45...
Current phase detection circuit, 46...Next phase identification circuit, 51...
Ring counter, 52... ROM as a command circuit,
53...D/A converter, 62...Central processing unit as correction means.

Claims (4)

[Claims] (1) Includes a stage that is moved by a drive device, a displacement detection device that detects the amount of movement of this stage, and an optical system that obtains an enlarged image of the object to be measured on the stage. an edge detection circuit for detecting an edge of the object, and is configured to determine the shape, dimensions, etc. of the object to be measured using output signals from both the displacement detection device and the edge detection circuit, The drive device includes a step motor connected to the drive shaft of the object table, a high-speed drive circuit that advances the step motor by a reference step angle, and a low-speed drive circuit that advances the step motor by mini-step angles smaller than the reference step angle. , a drive switching circuit that switches between the high-speed drive circuit and the low-speed drive circuit based on commands of a drive program; a current phase detection circuit that detects the current excitation phase of the step motor; and a current phase detection circuit that detects the current excitation phase of the step motor. a next phase identifying circuit that compares the phase with next process command information of the drive program to identify an initially excited phase of the next process by the high speed drive circuit or the low speed drive circuit; A correction means is provided for correcting the number of drive pulses supplied to the drive circuit or the low-speed drive circuit for the next process by a number equivalent to the positional deviation between the current position of the stage and the command position detected by the displacement detection device. An optical measuring device characterized by: (2) In claim 1, the high-speed drive circuit is of a constant current excitation type with a reference step angle of θ_5, and the low-speed drive circuit has a step angle smaller than the reference step angle of θ_5, and Optical measurement characterized by being configured to stepwise switch the applied current ratio of adjacent coils of the step motor so as to obtain a mini-step angle θ_m that divides the reference step angle θ_5 into n equal parts. Device. (3) In claim 2, the low-speed drive circuit includes a ring counter that re-counts each time the number of input drive pulses reaches a predetermined number, and a step motor that is operated in response to the counted value of the ring counter. It is characterized by being formed including a command circuit that commands to apply a predetermined current to a predetermined coil, and a D/A converter that converts a digital signal output from the command circuit into a corresponding analog signal. Optical measuring device. (4) In claim 3, the current phase detection circuit detects the current excitation phase from the excitation phase of the step motor during high-speed operation by the high-speed drive circuit, and detects the current excitation phase from the excitation phase of the step motor during low-speed operation by the low-speed drive circuit. An optical measuring device characterized in that it is configured to detect a currently excited phase from a ring counter of a low-speed drive circuit.