JPH0672764B2 - Position detection circuit - Google Patents

Description

Description: (a) Technical Field of the Invention The present invention relates to a dimension measuring apparatus which irradiates a measured object with parallel scanning light and detects a generated shadow with a light receiving element. The present invention relates to a detection circuit for detecting the positional relationship of.

(B) Conventional Technique and Problems Next, the configuration of a conventional optical dimension measuring apparatus will be described with reference to FIG.

In FIG. 9, 1 is a light source, 2 is a rotating mirror, 3 is an fθ lens,
Reference numeral 4 is a condenser lens, 5 is a light receiving element, 6 is an object to be measured, 7 is a condenser lens, and 8A is a position sensor.

In FIG. 9, the position sensor 8A is used as a position detecting means.
Is used to detect the image formation position of the scattered light from the DUT 6.

However, in FIG. 9, even if the position of the DUT 6 in the optical axis direction does not change, if the position of the light beam in the scanning direction changes, as shown by the broken line in FIG. The image position changes.

FIG. 10 is a modification of FIG.

In FIG. 10, two sets of optical systems of a condenser lens 7A and a position sensor 8A, and a condenser lens 7B and a position sensor 8B are arranged,
The position in the optical axis direction is calculated based on the principle of triangulation.

However, the configuration shown in FIG. 10 has the following problems.

(A) The optical system becomes complicated.

(B) It takes time from the detection of the position to the end of the calculation.

(C) Object of the Invention The present invention detects a shadow signal of an object to be measured by a light receiving element,
Position where the distance between the beam waist position and the object to be measured is obtained from the rise or fall time of the detected signal, and the positional relationship before and after the object to be measured with respect to the beam waist position is known from the scattered light of the object to be measured. It is intended to provide a detection circuit.

(D) Embodiment of the Invention Next, FIG. 1 shows a block diagram of an embodiment according to the present invention.

8C in FIG. 1 is a two-divided photodiode (hereinafter simply referred to as a diode), 9.9A and 9B are image points, 10A and 10B are amplifiers, 11 is a comparator, 12 is an output, and other parts are the 9th. It is the same as the figure.

In FIG. 1, a light beam emitted from a light source 1 is scanned by a rotating mirror 2, a lens 3 forms a uniform-velocity parallel light flux, and the scanning light is applied to a DUT 6. The shadow of the DUT 6 is detected by the light receiving element 5 through the condenser lens 4.

The light receiving element 5 is for measuring dimensions, and the output of the light receiving element 5 is guided to an arithmetic unit (not shown).

Normally, the DUT 6 is placed at the beam waist position of the scanning light.

Next, detection of the positional relationship between the front and rear of the DUT 6 with respect to the beam waist position will be described.

The optical axis A of the scanning light is defined as the optical axis A in the plane of parallel light flux, and the optical axis A
An optical axis B is a line that is perpendicular to and passes through the beam waist position.
Here, the front and rear positions of the DUT 6 mean the polarity in the optical axis A direction with respect to the optical axis B.

In order to detect this polarity, condenser lens 7 and diode 8C
To use.

Then, the condenser lens 7 and the diode 8C are arranged so that the scattered light from the DUT 6 arranged at the center in the scanning direction is condensed as an image point 9 on the diode 8C so that the following relationship is established. It

(1 / L ₁ ) + (1 / L ₂ ) = (1 / f) (1) Here, the focal length of the condenser lens 7 is f, and the object to be measured 6 arranged at the center in the scanning direction is the condenser lens. The distance to 7 is L ₁ ,
The distance from the condenser lens 7 to the diode 8C is L ₂ .

The DUT 6 changes its position with respect to the direction of the optical axis A,
When it becomes 6A or 6B, it is condensed as an image point 9A for the position 6A and as an image point 9B for the position 6B.

The signal generated in the divided area of the diode 8C is an amplifier.
Amplified by 10A and 10B respectively, each output is comparator 11
Will be input.

Next, the waveform chart of FIG. 1 is shown in FIG.

FIG. 2A is an output waveform diagram of the light receiving element 5.

When the object to be measured 6 is irradiated with parallel scanning light, the light receiving element 5 can detect the shadow of the object to be measured 6.

2A shows the amplifier 10 when the DUT 6 is at the position 6A.
It is an output waveform diagram of A.

When the DUT 6 is at the position 6A, an image 9A is obtained, and the output of the amplifier 10A becomes a bright signal at the timing when scattered light is generated.

FIG. 2C shows the amplifier 10 when the DUT 6 is at the position 6A.
It is an output waveform diagram of B, and the output of the amplifier 10B is always a signal in a dark state.

FIG. 2D is a waveform diagram of the output 12 of the comparator 11 when the DUT 6 is at the position 6A.

The output 12 of the comparator 11 is set to the L level at the timing when scattered light is generated. At other timings, the same dark state signal is output from the amplifiers 10A and 10B, so the state of the output 12 can be H or L depending on various electrical conditions.

2A to 2D are waveform diagrams when the DUT 6 is at the position 6B.

FIG. 2E shows the amplifier 10 when the DUT 6 is at the position 6B.
It is an output waveform diagram of A, and the output of the amplifier 10A is always a signal in a dark state.

FIG. 2F shows the amplifier 10 when the DUT 6 is at the position 6B.
FIG. 7 is an output waveform diagram of B.

When the DUT 6 is at the position 6B, an image 9B is obtained, and the output of the amplifier 10B becomes a bright signal at the timing when scattered light is generated.

FIG. 2C is a waveform diagram of the output 12 of the comparator 11 when the DUT 6 is at the position 6B.

In the case of the position 6B as well, the output 12 is similarly set to the H level at the timing when the scattered light is generated.

Therefore, if you make a trigger signal at the timing of the scattered light and sample the output 12, you can use the H and L of that level.
You can see whether the position is 6A or 6B.

Even if the DUT 6 moves in the scanning direction, whether the DUT 6 is on the position 6A side or the position 6B side with respect to the optical axis B is the same as the image point on the diode 8C. Can be seen depending on whether the light is concentrated on 9A side or 9B side. That is,
I know the polarity.

Next, the distance detection from the beam waist position will be described.

For the light beam, if the beam diameter at the beam waist position is W ₀ and the beam diameter at a position separated by a distance x from the beam waist position is w, then the following formula is established.

w ² = w ₀ ² {1+ (4λx / πw ₀ ² ) ² } (2) where λ is the wavelength of the used light.

FIG. 3 is a graph showing the relationship of Expression (2).

Next, FIG. 4 shows a waveform diagram of a signal output from the light receiving element 5.

As the DUT 6 moves away from the beam waist position, the beam diameter crossing the DUT 6 increases according to FIG. 3, so that the signal rising from the light receiving element 5 rises at the fourth position.
It changes from the solid line to the broken line.

So, for example, assuming that the amplitude of the entire signal is 100%, 10% and 9
Assuming that the level corresponding to 0% is the reference level for comparison, the time t for reaching from 10% to 90% of the power of the entire beam at the rising portion is obtained, which is also large as shown in FIG.

If the beam changes only by the distance without changing the distribution according to the equation (2), the interval corresponding to a certain ratio of the power, for example, the interval from 10% to 90%, is the beam diameter. The calculation shows that it is proportional to w.
Therefore, when the scanning speed is constant, the time t in FIG.
It is proportional to the beam diameter w.

As is clear from the equation (2), the beam diameter w is constant regardless of the position in the scanning direction if the distance x is constant. Therefore, the distance x in the optical axis direction can be known from the time t regardless of the position of the DUT 6 in the scanning direction.

Next, FIG. 5 shows a block diagram of an embodiment for obtaining the time t in FIG.

The waveform (A) in FIG. 4 is the signal output from the light receiving element 5, but by inserting the waveform (A) into the comparison circuit 13,
The waveform (B) and the waveform (C) of FIG. 4 are obtained.

Clock generator while waveform (B) and waveform (C) are appearing
Counter 15 counts 15 clock pulses.

When the output of the counter 14 is put into the D / A converter 16, a voltage proportional to the time when the waveform (B) or the waveform (C) is generated is obtained.

When the output of the D / A converter 16 enters the linearizer 17 that linearizes the curve of FIG. 3, a voltage proportional to the distance from the beam waist position to the DUT 6 appears at the output 18.

FIG. 6 is a diagram showing the relationship between the output 18 of the linearizer 17 and the distance from the beam waist position of the DUT 6.

Next, FIG. 7 shows a configuration diagram of an embodiment in which the polarity detection and the distance detection are combined.

In contrast to FIG. 5, FIG. 7 shows an arrangement in which the counter 14 is an up / down counter 14B and the output 12 of FIG. 1 is input to the up / down control terminal.

FIG. 8 is a diagram showing the relationship between the output 18B of the linearizer 17 of FIG. 7 and the distance from the beam waist position of the DUT 6.

(E) Effect of the Invention According to the present invention, the distance between the beam waist position and the object to be measured is known from the rising or falling time of the detected signal, and the measured light from the scattered light of the object to be measured with respect to the beam waist position is measured. Since I try to know the positional relationship before and after the object,
There are the following advantages over the prior art.

(A) The circuit is simple because no arithmetic circuit is required.

(A) High speed operation because no arithmetic circuit is required.

(C) Even if the position of the DUT in the scanning direction changes, it does not affect the detection of the position in the optical axis direction.

(D) The configuration of the optical system becomes simple.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment according to the present invention, and FIG.
FIG. 3 is a waveform diagram of the figure, FIG. 3 is a diagram showing the relationship between the beam diameter w and the distance x from the waist position, FIG. 4 is a waveform diagram of the signal output from the light receiving element 5, and FIG. 6 is a diagram showing the relationship between the output of the linearizer 17 and the distance from the beam waist position of the DUT 6,
FIG. 7 is a configuration diagram of an embodiment in which polarity detection and distance detection are combined, and FIG. 8 is a diagram showing the relationship between the output of the linearizer 17 of FIG. 7 and the distance from the beam waist position of the DUT 6, FIG. 9 is a block diagram of a conventional optical dimension measuring device,
FIG. 10 is a block diagram of a conventional device improved from FIG. 1 ... Light source, 2 ... Rotating mirror, 3 ... Lens, 4 ...
Condenser lens, 5 ... Light receiving element, 6 ... Object to be measured, 6A ・ 6B
…… Position, 7 …… Condensing lens, 8A ・ 8B …… Position sensor, 8C …… Divided photodiode (diode),
9 ・ 9A ・ 9B …… image point, 10A ・ 10B …… amplifier, 11 …… comparator, 12 …… output, 13 …… comparison circuit, 14 …… counter, 14B …… up / down counter, 15 …… clock generation Vessel, 16 …… D / A converter, 17 …… linearizer.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Houji Hattori 1 Taya-cho, Sakae-ku, Yokohama-shi, Kanagawa Sumitomo Electric Industries, Ltd. Yokohama Works (72) Inventor Shuzo Suzuki, 1 Taya-cho, Sakae-ku, Yokohama, Kanagawa Sumitomo Electric Industry Co., Ltd. Yokohama Works

Claims (1)

[Claims] 1. A dimension measuring apparatus using light for irradiating an object to be measured with parallel scanning light and detecting a generated shadow by a light receiving element, wherein the scattered light from the object to be measured is imaged, and an optical axis of the object to be measured is formed. Detection circuit that detects the front-rear positional relationship with respect to the reference position in the direction, and signal generation that generates a signal proportional to the distance between the DUT and the reference position in the optical axis direction from the rise or fall time of the shadow of the DUT. A position detection circuit comprising: a circuit.