JP2884116B2 - Dimension measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dimension measuring apparatus for measuring a dimension of an object to be measured by scanning a light beam such as a laser beam.

[0002]

2. Description of the Related Art In order to measure the outer diameter, edge position, and the like of an object to be measured with high accuracy, a light beam having good directivity such as a laser beam is scanned in a space in which the object to be measured is placed along a measuring direction. Conventionally, there has been a dimension measuring device configured to receive a light beam blocked by an object to be measured.

Conventionally, a rotating mirror method and a vibrating mirror method using sound or the like have been used as a deflection method for scanning a light beam. The vibrating mirror method has a high repetition frequency of scanning and excellent responsiveness. , And reciprocal scanning is possible,
It has the characteristic that the measurement error can be offset by the round-trip averaging.

FIG. 10 is a diagram showing a basic configuration of a dimension measuring apparatus using the oscillating mirror system. Reference numeral 1 denotes a light source for outputting a laser beam or the like;
This is a deflector that deflects light periodically in the direction.

[0005] The mirror of the deflector 2 is located at the front focal point of the lens 4, and the light beam reflected by the deflector 2 and passing through the lens 4 is periodically parallel to the optical axis of the lens 4 and along the measurement direction Y. Will be scanned.

When the deflector 2 is a vibrating mirror such as a sound or deflector, the change in the position of the light beam scanned in the Y direction is shown in FIG.
As shown in FIG. 1 (a), it changes almost sinusoidally with time.

[0007] For this reason, from the light receiver 6, (b) of FIG.
As shown in (1), a light receiving signal is output which has an H level in a portion blocked by the object A and an L level in a portion not blocked.

Reference numeral 7 denotes a reference signal generator which outputs a sine wave voltage signal synchronized with the scanning light to the arithmetic unit 8 as shown in FIG.

The arithmetic unit 8 stores in advance the amplitude ratio between the reference signal and the scanning light, and calculates the edge position from the scanning center of the DUT A from the reference signal voltage V ₁ at the time of the rise of the light receiving signal. .

However, when such an apparatus is actually constructed, the position change of the scanning light often does not become a perfect sine function due to lens aberration and mirror distortion.

For this reason, correction data specific to the measurement position measured in advance is stored in the correction data memory 9, and a correction operation between the calculated edge position and the correction data corresponding thereto is performed by the optical correction circuit 10. I'm trying to do it.

[0012]

However, this distortion of the optical system causes not only an error with respect to the sine function, but also a variation in the beam shape of the measurement light, resulting in an asymmetric intensity distribution in the scanning direction. Therefore, even if the position of the edge to be measured is the same, there is a difference between the measurement results when the edge is directed to one side of the scanning direction and when the edge is directed to the other side. There was a problem.

An object of the present invention is to provide a dimension measuring device which solves this problem.

[0014]

An optical system for receiving a measuring beam reciprocatingly scanned with a predetermined width by a light receiving device, and an edge position of an object to be measured placed at a position where a part of the measuring light is blocked, is detected by a light receiving device. Edge position detecting means for detecting based on the light receiving signal from
An optical correction unit that corrects an error of a detection position by the optical system with respect to the detected edge position using correction data for each detection position, wherein the edge to be measured faces in one scanning direction of the measurement light. First correction data storage means for preliminarily storing the correction data of the optical system when the light is present, and correction data for the optical system when the edge to be measured is oriented in the other scanning direction of the measurement light. A second correction data storage means, an edge polarity detection means for detecting which scanning direction of the measurement light the direction of the edge of the measurement object faces, and a first and a second correction data storage means. Correction data selecting means for selecting correction data for the edge position of the device under test from the correction data storage device corresponding to the direction of the edge of the device under test detected by the edge polarity detecting device. Eteiru.

[0015]

Therefore, the optical correction for the edge position of the object to be measured is made by the correction data corresponding to the direction of the edge.

[0016]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a view showing the overall configuration of a dimension measuring apparatus according to one embodiment. The same components as those in the apparatus shown in FIG.

In FIG. 1, a scanning light beam from a lens 4 is split into a measuring light and a reference light having the same amplitude by a half mirror 25, and the measuring light is received by a light receiver 6 via a lens 5,
The reference light is received by a light receiver 27 via a lens 26.

A reference rod R having a known outer diameter in the scanning direction of the reference light is fixed between the half mirror 25 and the lens 26 substantially at the scanning center of the reference light.

Here, a light receiving signal (hereinafter referred to as a monitor signal) from the light receiver 27 for receiving the reference light is at the H level while the reference light is blocked by the reference rod R, and the reference light is received. The interval is at the L level.

The monitor signal is supplied to a period measuring circuit 30, a timing detecting circuit 31, and a first phase angle calculating circuit 32.
Has been entered.

The period measuring circuit 30 receives the monitor signal shown in FIG. 2B from the light receiver 27 for receiving the reference light shown in FIG. 2A and receives the monitor signal shown in FIG. Are added to each other for two periods, and the time T ₀ is measured as the period of the scanning light.

The timing detection circuit 31 detects a timing at which T _0/4 time has elapsed from the intermediate timing of the light receiving time T ₁ in one cycle T ₀ as a zero phase timing of the reference light, and detects a timing pulse synchronized with this timing. Is output as shown in (c) of the same figure, and the level is inverted at each intermediate timing of each light receiving time, and a scanning direction signal indicating the scanning direction of the reference light at that level is output.

The first phase angle detector 32 receives a timing pulse and the monitor signal, and time T _a from the rising of the monitor signal to zero phase timing, the time from the zero phase timing to the fall of the monitoring signal detecting a T _b, the detection time, and outputs the converted phase angle _{a = -2πT a / T 0,} b = 2πT b / T 0 for zero phase timing.

A sine conversion circuit 33 stores a sine value for each phase angle in advance. The sine conversion circuit 33 stores Sina and Sinb with respect to the phase angles a and b from the first phase angle detection circuit 32. To memorize.

The sine value stored in the memory circuit 34 is subtracted by the subtraction circuit 35, and the outer diameter value r of the reference rod when the amplitude of the reference light from the scanning center is normalized to 1 is calculated.

Reference numeral 36 denotes an amplitude value of the reference light (the same is applied to the measurement light).
And calculates the amplitude value E (= D / r) from the scanning center by dividing the true outer diameter value D of the reference rod R by the calculated value r from the subtraction circuit 35.

Numeral 40 denotes a light receiving signal output from the light receiver 6 which receives the measuring light blocked by the object B as shown in FIG. 3A, as shown in FIG. Timing pulse from the timing detection circuit 31 ((c) in the figure)
Receiving, measurement light and measure the time T _c until crossing the edge of the object B, the T _c phase angle _c (= 2πT c / T
₀ ) is a second phase angle detection circuit that outputs the converted signal.

Reference numeral 41 denotes the first sine conversion circuit 33 described above.
And a sine value K (= Sin) corresponding to the phase angle c from the second phase angle detection circuit 40.
Output c).

Reference numeral 42 denotes an edge position calculating means for multiplying the output from the second sine wave conversion circuit 41 by an amplitude value E to calculate the edge position of the DUT B with respect to the scanning center of the measuring light.

Reference numeral 43 denotes a correction operation circuit for adding and correcting an edge position error due to aberration of each lens or distortion of a mirror using correction data measured in advance.

Reference numeral 44 denotes a light receiving signal from the light receiving device 6 and a scanning direction signal, and the DUT B within the scanning range of the measuring light.
Is an edge polarity detection circuit that detects whether the edge direction is directed to one side or the other side in the scanning direction.

The edge polarity detection circuit 44 detects the level of the light receiving signal at the time of rising and falling of the scanning direction signal by the inverter 45 and the flip-flops 46 and 47, as shown in FIG. The polarity determiner 48 determines the direction of the edge from the level. That is, as shown in FIG. 5, the output Q of one flip-flop 46 is
a is at the L level and the output Q of the other flip-flop 47 is
When b is at the H level, the direction of the edge of the object B is
It is determined that it is upward as shown in FIG.

On the other hand, when the output Qa is at the H level and Qb
Is L level, it is determined that the direction of the edge is downward. If both outputs are at the L level, it is determined that the entire DUT is within the scanning range of the measurement light and that there are two upward and downward edges.

Reference numerals 50 and 51 denote first and second correction data memories, respectively. The first correction data memory 50 has, as shown in FIG. The difference between the actual movement amount and the output value from the edge position calculation circuit 42 is stored using the output value as an address.

In the second correction data memory 51,
The difference between the actual movement amount when the reference gauge 60 is moved in the measurement light in the opposite direction and the output value from the edge position calculation circuit 42 is stored using the output value as an address.

Reference numeral 52 denotes a correction for outputting correction data from the first or second correction data memory 50, 51 in accordance with the direction of the edge detected by the edge polarity detection circuit 44 to the correction operation circuit 43. This is a data selection switch.

In the dimension measuring apparatus configured as described above, as shown in FIG. 3, when the edge of the object to be measured is upward, the correction data for the edge position calculated by the edge position calculating means 42 is: First correction data memory 50
And the error is corrected by the optical system.

Conversely, as shown in FIG. 7, when the direction of the edge of the DUT C is downward, the edge position calculation circuit 42
The correction data for the edge position calculated in is selected from the second correction data memory 51, and an error is corrected by the optical system.

As shown in FIG. 8, when the DUT is located within the scanning range of the measurement light, the correction data for the two edge positions are stored in the first and second correction data memories. 50 and 51 are alternately selected and optical correction is performed on two edges.

For this reason, even if the beam shape of the measurement light in the scanning direction surface is asymmetric as shown in FIG. 9, no measurement error occurs and high-accuracy position measurement can be performed.

In the above description, the case where the edge position of the object to be measured is detected has been described. However, by calculating the corrected position outputs, the outer diameter value and the inner diameter value can be measured with high accuracy. Can be.

[0045]

[Other Embodiments] In the above embodiment, the scanning cycle, the zero-phase timing pulse, and the scanning direction signal are output based on the light receiving signal (monitor signal) of the reference light. These signals may be output based on the driving signal.

In the above-described embodiment, the amplitude of the reference light is calculated from the monitor signal, and the amplitude is used as the amplitude of the measurement light. However, the amplitude of the measurement light may be actually measured in advance. The amplitude ratio between the reference light and the measurement light may be measured, and the edge position of the device under test may be calculated based on the amplitude ratio.

In the above embodiment, the description of the averaging of the respective calculated values based on the light receiving signals of the light receivers 6 and 27 is omitted. If averaging by round trip is performed, more accurate measurement can be performed.

[0048]

According to the dimension measuring apparatus of the present invention, the optical correction data when the edge is directed to one side in the scanning direction of the measuring light and the optical correction data when the edge is directed to the other side in the scanning direction of the measuring light. Optical correction data is stored in advance, and optical correction data corresponding to the direction of the edge of the measured object is selected,
Since an error due to the optical system is corrected, a measurement error due to a variation in the beam shape of the measurement light does not occur, and highly accurate dimension measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of one embodiment.

FIG. 3 is a timing chart for explaining the operation of one embodiment.

FIG. 4 is a block diagram showing a configuration of a main part of one embodiment.

FIG. 5 is a correspondence diagram for explaining the operation of the main part of one embodiment.

FIG. 6 is a diagram for explaining an operation for storing correction data.

FIG. 7 is a diagram for explaining the operation of one embodiment.

FIG. 8 is a diagram for explaining the operation of one embodiment.

FIG. 9 is a diagram illustrating an example of an intensity distribution of measurement light.

FIG. 10 is a diagram showing a basic configuration of a conventional device.

FIG. 11 is a timing chart for explaining the operation of the conventional device.

[Explanation of symbols]

 Reference Signs List 1 light source 2 deflector 6 light receiver 25 half mirror 27 light receiver 32 first phase angle detection circuit 33 first sine conversion circuit 35 subtraction circuit 36 amplitude calculation circuit 40 second phase angle detection circuit 41 second sine conversion Circuit 42 Edge position calculation circuit 43 Correction operation circuit 44 Edge polarity detection circuit 50 First correction data memory 51 Second correction data memory 52 Correction data selection switch

Claims (1)

(57) [Claims] 1. An optical system for receiving a measuring beam reciprocatingly scanned at a predetermined width by a light receiving device, and receiving an edge position of an object to be measured placed at a position blocking a part of the measuring light from the light receiving device. An edge position detection unit that detects based on the signal, and an optical correction unit that corrects an error of a detection position by the optical system with respect to the detected edge position using correction data for each detection position. First correction data storage means for storing in advance the correction data of the optical system when the edge to be measured is oriented in one scanning direction of the measurement light; A second correction data storage unit that stores in advance the correction data of the optical system when the measurement light is directed, and detects in which scanning direction of the measurement light the edge of the measured object is directed. Do Edge polarity detection means;
The correction data for the edge position of the device under test is selected from the correction data storage device of the second correction data storage device corresponding to the direction of the edge of the device under test detected by the edge polarity detection device. A dimension measuring device comprising: a correction data selecting unit.