JPH07128014A - Position detector - Google Patents

Abstract

PURPOSE:To rapidly and accurately obtain the amount of deviation and the deviation direction from a specific position of an object to be measured with a simple configuration. CONSTITUTION:The title detector is provided with a light source 1, a collimator lens 2, a pin hole 3, a half mirror 6, and an objective lens 7, thus projecting a flux of spot light within a specific range on an object to be measured. Further, a polarization prism 4 for performing displacement in circular and elliptical shape without relatively stopping the flux of spot light for the object and a first light reception element 21 and a second light reception element 22 for receiving the flux of reflection light from the object where the spot is projected for a focusing position at forward and backward position, respectively are provided. For example, it is determined that the object is located at a specific position, for example, when the output of the first light reception element 21 and that of the second light reception element 22 are virtually equal within a specific period where the spot scans.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device used for an autofocus mechanism or the like.

[0002]

2. Description of the Related Art Accurate and quick position detection is essential for an autofocus mechanism. Conventionally, various position detecting devices for use in a focusing operation have been proposed, but a representative one is a device using a light spot and a device using an image contrast.

[0003]

In the former device utilizing a light spot, since light is scattered by unevenness or steps on the surface of the work, it is difficult to detect the position with high accuracy when the surface condition of the work is poor. there were.

The latter device utilizing image contrast is a device in which a stripe pattern is projected on the surface of a work and the contrast of the image is detected by a photodiode array or a CCD camera. This device is configured to perform position detection and focusing by, for example, capturing a signal related to a projected fringe pattern while changing the distance between the microscope unit and the work and processing the signal. For this reason,
It has a drawback that it takes a lot of time until the final focusing is achieved.

An object of the present invention is to provide a position detecting device which can quickly and accurately determine the deviation amount and deviation direction of a measured object from a predetermined position.

[0006]

The first invention of the present application is as follows. That is, a position detection device having the following configuration.

Projecting optical means for projecting a spot in a predetermined range on the object to be measured, and first light receiving for receiving a reflected light beam from the object to be measured on which the spot is projected at a position ahead of a predetermined position by a predetermined distance. The element, the second light receiving element for receiving the reflected light flux from the object to be measured on which the spot is projected at a position ahead of the predetermined position by a predetermined distance, and the relative position between the object to be measured and the spot is displaced without stopping. Scanning means.

The second invention of the present application is as follows. That is, a position detection device having the following configuration.

A projection optical means having a light source, a collimator lens, a pinhole, a half mirror and an objective lens, which forms a light beam and projects a spot on the object to be measured by the light beam, and an object on which the spot is projected. The first light receiving element that receives the light flux reflected from the measurement object at a first position that is a predetermined distance ahead of the condensing position, and the light flux reflected from the measurement object on which the spot is projected are A second light receiving element that receives light at a second position that is behind the light position by a predetermined distance, and a scanning unit that displaces the spot within the predetermined range relative to the object to be measured without stopping.

[0010]

According to the position detecting apparatus of the present invention, the position can be detected by the components of the reflected light beams from different parts of the object to be measured, and the measurement accuracy can be improved.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a position detecting device in which a spot formed on an object to be measured moves without substantially stopping.

The best example is an example in which the spot moves on the object to be measured at a constant angular velocity along a shape consisting of only a curve such as a circle or an ellipse.

The illustrated example will be described below.

In the first illustrated example shown in FIG. 1, the light source 1
The light from the lens passes through the collimator lens 2 and becomes a parallel light flux, and illuminates the pinhole 3.

The light beam emitted from the pinhole 3 is deflected by the deflection prism 4 and further reflected by the half mirror 6. Then, the light flux passes through the objective lens 7 and forms a spot near the object M to be measured.

The deflecting prism 4 is, for example, by a motor 8, a gear 9 connected thereto, and an optical axis 11 via an annular gear 10 meshed with the gear 9 and arranged on the entire outer periphery of the polarizing prism 4. It is configured to be rotatable around. As the deflection prism 4 rotates, the deflection direction of the light beam passing therethrough changes, so that the locus of the spot S formed on the object M to be measured has a circular shape as shown in FIG. That is, the deflection prism 4 is rotated around the optical axis 11 at a constant speed by the motor 8,
The spot S formed on the measured object M circularly moves at a constant angular velocity.

In the first embodiment, the rotating deflection prism 4 corresponds to "scanning means". Further, the light source 1, the collimator lens 2, the pinhole 3, the half mirror 6, and the objective lens 7 correspond to “projection optical means”. The first light receiving element 21 and the second light receiving element 22 correspond to "light receiving means".

The reflected light from the surface of the object to be measured is received by the first light receiving element 21 and the second light receiving element 22, respectively. The positional relationship between the first light receiving element 21 and the second light receiving element 22 is set as follows. That is, when the object to be measured M is arranged at a predetermined position, the first position is set so as to receive the reflected light beam forward by a predetermined distance from the condensing position F of the reflected light beam from the surface of the object M to be measured. One light receiving element 21 is arranged, and the second light receiving element 22 is arranged so as to receive the reflected light flux at the same distance behind.

The first light receiving element 21 is configured to receive the reflected light beam from the object to be measured M via the half mirror 23.

The object M to be measured is placed on the stage 30. The stage 30 has a base 31 driven by a motor 32.
Is relatively movable in the optical axis direction (Z direction).

Instead of moving the stage 30 in the optical axis direction, the entire optical means such as an objective lens may move with respect to the object to be measured.

Next, an example of the position determining means will be described.

First, referring to the block diagram shown in FIG.
A method of processing the received light amount obtained by the first and second light receiving elements 21 and 22 will be described.

The integrator circuits 40a and 40b have resistors R and R, respectively.
1, a capacitor C and an amplifier AP, and integrates the outputs of the first light receiving element 21 and the second light receiving element 22.
The integration circuits 40a and 40b are connected to the subtraction circuit 50.

Output of first light receiving element 21 and second light receiving element 2
The output of No. 2 has a waveform as shown in FIG. 4, for example, where the horizontal axis represents the position in the optical axis direction (Z direction) and the vertical axis represents the output level. The arrow in FIG. 4 indicates a predetermined position.

The time constant τ (= C of the integrating circuits 40a and 40b
* R) is preferably set to a value larger than the period T in which the deflection prism makes one rotation. By setting the time constant τ in this way, the detection accuracy can be improved. This is because the reflected light flux from a relatively wide area of the object to be measured can be used for position detection.

The time constant τ of the integrating circuits 40a and 40b
Can be set to a value smaller than the rotation period T of the deflecting prism, but in that case, within a range in which sufficient accuracy can be obtained by adding signal components from parts to be measured to some extent different from each other. It is necessary to select the time constant τ.

The signals from the integrating circuits 40a and 40b are sent to the subtracting circuit 50. The subtraction circuit 50 subtracts the signal (2) of the second light receiving element 22 from the signal (1) of the first light receiving element 21 that has been subjected to integration processing, and sends the result to the control calculation unit 100. FIG. 5 shows a signal obtained by subtracting the signal (2) of the second light receiving element 22 from the signal (1) of the first light receiving element 21.
The arrow in FIG. 5 shows an example of the predetermined position, and the output of the subtraction circuit becomes zero when the measured object M is at the predetermined position.

A control calculation unit 100 is connected to the subtraction circuit 50. The control calculation unit 100 makes the following determination based on the output of the subtraction circuit 50. That is, when the output of the subtraction circuit is a positive value, the DUT M is located in front of the predetermined position, and when the output is a negative value, the DUT M is located behind the predetermined position and the output is zero. In the case of, it is determined that the measured object is at the predetermined position. Further, the control calculation unit 100 determines that the larger the absolute value of the output of the subtraction circuit is, the more it is displaced from the predetermined position. Regarding the relationship between the magnitude of the absolute value and the deviation width of the object to be measured, it is preferable to calibrate in advance and obtain the corresponding relationship.

The control calculation section 100 causes the display section 60 to display the displacement amount and the displacement direction from the predetermined position. The control calculation unit 100 gives an instruction to the operation unit 70 based on the result of the above-described determination, and drives the stage moving unit 80 to move the measured object M to a predetermined position as needed or automatically.
The control calculation unit 100 also includes a deflection prism rotation drive unit 90.
To control the deflection prism 4 around the optical axis by a predetermined period T
Rotate with.

Next, a second example of the present invention will be described with reference to FIG.

FIG. 6 shows the optical means in the second illustrated example, and the same components as those in FIG. 1 are designated by the same reference numerals. In the following, differences from FIG. 1 will be mainly described.

In the second illustrated example, the deflecting prism 4 of the first illustrated example is not provided. Instead, the stage unit 30a is arranged not only in the optical axis direction but also in the XY direction orthogonal to the optical axis.
It is also movable in the plane, and by moving the DUT M slightly in the XY plane,
The same effect as the rotation of the polarization prism 4 in the first illustrated example is obtained.

In the second illustrated example, the movement in the XY plane is performed by the driving force of the second scanning motor 33. The stage 35 mounted on the bearing 34 is moved in the XY plane by the second motor 33, and this constitutes the "scanning means". In a configuration in which the second scanning motor 33 is movable in the X and Y directions, the amplitude and period (frequency) of the movement in the X and Y directions are made equal to each other, and a phase difference of 90 ° is provided between them. As a result, the spot S formed on the object to be measured M by the light from the light source 1 makes a circular motion at a constant angular velocity.

FIG. 7 shows a third illustrated example of the present invention. A deflection prism 4a having a trapezoidal cross section is configured to rotate about the vertical axis of the drawing so as to deflect the light from the light source 1 in a direction orthogonal to the drawing. The rotation of the deflection prism 4a causes the light from the light source 1 to move in a direction (Y-axis direction) orthogonal to the paper surface. On the other hand, the stage 30 is moved by the motor 32 in the X direction (direction orthogonal to the movement of light by the deflection prism 4a). The moving range in the Y direction by the deflection prism 4a and the moving range in the X direction by the stage 30 are set to have the same period (frequency) of movement, and a 90 ° phase difference is given to both. As a result, the spot S formed on the object to be measured M by the light from the light source 1 makes a circular motion at a constant angular velocity with respect to the object to be measured M.

Next, application examples of the above-described illustrated examples 1 to 3 will be briefly described.

In the first illustrated example, the first light receiving element 2
By integrating the outputs of 1 and the second light receiving element 22, sufficient accuracy has been obtained by adding the signal components of different parts of the device under test M. However, the first light receiving element 21 and the second light receiving element 22 Is configured as a light-receiving element having a storage action such as CCD, the outputs of the first light-receiving element 21 and the second light-receiving element 22 are stored for an appropriate storage time in which signals of different portions of the device under test M can be obtained. Thus, the desired effect of the present invention can be obtained without providing an integrating circuit.

Further, in the first illustrated example, by integrating the outputs of the first light receiving element 21 and the second light receiving element 22, a sufficient accuracy can be obtained by adding the signal components of different portions of the device under test M. Although obtained, the measurement of the signals of the first light receiving element 21 and the second light receiving element 22 due to reflection at different positions of the object to be measured M is repeated a plurality of times, and the average value thereof is obtained to determine the position of the object to be measured M. Sufficient accuracy can be obtained by asking for it. Also in this case, the desired effect according to the present invention can be obtained without using an integrating circuit.

[Brief description of drawings]

Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view showing a first illustrated example of the present invention.

FIG. 2 is a block diagram showing a signal flow of the first illustrated example.

FIG. 3 is a plan view showing the appearance of spots on the object to be measured in FIG.

FIG. 4 is a graph showing an output example of the first light receiving element and the second light receiving element in FIGS. 1 and 2.

5 is a graph obtained by subtracting the two outputs of FIG.

FIG. 6 is a schematic diagram showing a second illustrative example of the present invention.

FIG. 7 is a schematic diagram showing a third illustrated example of the present invention.

[Explanation of symbols]

 1 light source 2 collimator lens 3 pinhole 4 deflection prism 6 half mirror 7 objective lens 30 stage 31 base 32 motor 21 first light receiving element 22 second light receiving element 40a, 40b integration circuit 50 subtraction circuit 60 display section 70 operating section 80 stage Drive unit 90 Deflection prism rotation drive unit 100 Control calculation unit

Claims (12)

[Claims] 1. A position detection device having the following configuration. Projection optical means for projecting a spot on the object to be measured in a predetermined range, and a first light receiving element for receiving a reflected light beam from the object on which the spot is projected at a position ahead of a predetermined position by a predetermined distance, A second light receiving element for receiving a reflected light beam from the object under measurement on which the spot is projected at a position ahead of a predetermined position by a predetermined distance, and a scanning means for displacing the relative position between the object under measurement and the spot without stopping. . 2. A predetermined position is provided when the output of the first light receiving element and the output of the second light receiving element within a predetermined period of scanning without stopping the spot are substantially equal to each other. The position detecting device according to claim 1 having a position determining means for determining. 3. Based on the output of the first light receiving element and the output of the second light receiving element when the spots are scanned at different positions, when the average values of these outputs are the same, a predetermined position is set. The position detecting device according to claim 1 having a position determining means for determining that there is. 4. The position detecting device according to claim 1, wherein the first light receiving element and the second light receiving element accumulate the amount of light received within a predetermined period of scanning without stopping the spot. 5. The position determining means substantially integrates the outputs of the first light receiving element and the second light receiving element within a predetermined period in which the scanning means scans the spot without stopping the spot, and then integrates them. The position detecting device according to claim 1, which determines that the position is a predetermined position if 6. The position detecting device according to claim 1, wherein the scanning means is a deflection prism that rotates in the middle of the light beam formed by the projection optical means. 7. The position detecting device according to claim 1, wherein the scanning means is a moving stage that moves the object to be measured relative to the projection optical means. 8. The scanning means is a combination of a deflection prism that rotates in the middle of a light beam formed by the projection optical means, and a moving stage that relatively moves an object to be measured with respect to the projection optical means. The position detecting device according to claim 1. 9. The position detecting device according to claim 1, wherein the scanning means displaces the spot with respect to the object to be measured at a substantially constant speed. 10. The position detecting device according to claim 10, wherein the scanning means displaces the spot along a shape consisting of only a curved line with respect to the object to be measured. 11. The position detecting device according to claim 1, wherein the predetermined position is a light collecting position. 12. A position detecting device having the following configuration. A projection optical unit that has a light source, a collimator lens, a pinhole, a half mirror, and an objective lens, forms a light beam by these, and projects a spot on the object to be measured by the light beam, and an object to which the spot is projected from the object to be measured. The reflected light flux,
A first light receiving element that receives light at a first position that is a predetermined distance ahead of the condensing position, and a light beam reflected from the DUT on which the spot is projected,
A second light receiving element that receives light at a second position that is behind the condensing position by a predetermined distance, and scanning means that displaces the spot relative to the object to be measured within a predetermined range without stopping.