JPH09105605A - Edge detection apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an edge detection apparatus by which the trouble of an adjustment is excluded and by which the edge of a sample is detected always surely and with high accuracy. SOLUTION: In the edge detection apparatus, the edge of a sample 1 is detected on the basis of the output of a first photodetector 9 while the sample 1 and an optical system which is provided with the first photodetector 9 used to receive via the sample 1, while light from a light source 20 through an illumination optical system are being moved relatively. A second photodetector 24 is arranged so as to detect value which is proportional to the intensity of the light from the light source 20 used to irradiate the sample 1. In addition, a differential amplifier 26 which changes the luminance of the light source 20 is installed so as to make the output of the second photodetector 24 constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a light source, an optical system having an illumination optical system and a photodetector, and detects the edge of the sample based on the output of the photodetector while moving relative to the sample. The present invention relates to an edge detection device.

[0002]

2. Description of the Related Art As a conventional edge detecting device, there is one having a structure as shown in, for example, Japanese Patent Laid-Open No. 5-99619. FIG. 5 is a block diagram of the edge detection device shown in this publication. As shown in FIG. 5, the sample 1 is placed on a stage 2 that is movable in the direction of the double-headed arrow A, that is, in the direction orthogonal to the optical axis of the objective lens 6, and is arranged on one surface side of the stage 2. The created telecentric illumination system includes a light source 3, a fiber guide 4, and a fiber guide 4.
The optical system 5 and the mirror 13 which make parallel light the light from one point on the end face of the. The light source 3 is turned on at a voltage set via the drive amplifier 14 from the reference voltage 15.

Further, an objective lens 6, an imaging lens 7, a pinhole 8 and a photodetector 9 are arranged on the other surface side of the stage 2, and the focus of the objective lens 6 is made to coincide with the surface of the sample 1 and telecentric. The objective lens 6, the light from the illumination system,
The light is received by the photodetector 9 through the imaging lens 7 and the pinhole 8, and its output is passed through the current / voltage converter (hereinafter abbreviated as I / V converter) 16 and the reference voltage 1 in the comparator 10.
The edge detection signal is obtained by comparing with a predetermined threshold value from 1.

Here, the threshold value based on the reference voltage 11 is set by the calibration work by displaying the output of the photodetector 9 in the bright portion and the dark portion of the sample edge on the monitor 12 and based on these values.

[0005]

However, the above-mentioned conventional edge detecting device has a problem that it is difficult to keep the intensity of the sample irradiation light constant. That is,
In the conventional edge detection device, deterioration of the light source itself causes deterioration of the light source brightness and mechanical displacement of the light source peripheral parts due to heat, etc., all of which change the intensity of the irradiation light irradiating the sample with time. Will end up.

When an intensity change occurs in this sample irradiation light,
As shown in FIG. 4, the photodetector 9 at the edge of the sample 1
The output profile also changes, and the detection error is included in the edge detection by comparing with the previously set threshold value.

For this reason, the conventional edge detecting device cannot hold the value of the reference voltage 11 indicating the threshold value as a constant, and the above-described calibration work is required. Especially, when performing edge detection with high accuracy, It was necessary to frequently perform the adjustment work called the calibration work.

The present invention has been made in view of such conventional problems. By stabilizing the intensity of the sample irradiation light, the troublesomeness of the adjustment is eliminated, and the edge detection of the sample is always simple and highly accurate. It is an object of the present invention to provide an edge detection device capable of performing.

[0009]

In order to achieve the above-mentioned object, the present invention constitutes an edge detecting device by the following means. In the invention corresponding to claim 1, the sample and the optical system including a first photodetector for receiving the light from the light source through the illumination optical system through the sample are moved relatively to each other. In the edge detection device for detecting the edge of the sample based on the output of the photodetector, a second photodetector for detecting a value proportional to the intensity of light emitted from the light source to the sample; Voltage control means for changing the brightness of the light source so that the output of the second photodetector becomes constant.

According to the second aspect of the invention, the sample and the optical system having the first photodetector for receiving the light from the light source through the illumination optical system through the sample are moved relatively to each other. In an edge detection device that detects an edge of the sample based on the output of the first photodetector, a second device arranged to output a value proportional to the intensity of light emitted from the light source to the sample. Photodetector, an optical filter that is movably provided in the illumination optical system and that changes the intensity of the sample irradiation light, and the output of the second photodetector is equal to a preset set value. And an optical filter moving mechanism for moving the optical filter.

Therefore, in the edge detecting device according to the first aspect of the invention, the second photodetector detects a value proportional to the intensity of the light emitted from the light source to the sample, and the second photodetector detects the value. By changing the brightness of the light source so that the output of the photodetector is constant, the intensity of the sample irradiation light is always constant even if the light source deteriorates or mechanical displacement around the light source occurs due to heat. Therefore, once the threshold for edge detection is set by the reference voltage, it becomes possible to have that set value as a constant of the device, and always with high accuracy without the troublesome adjustment of the conventional calibration work. Edge detection can be performed.

Further, in the edge detecting apparatus of the invention according to claim 2, a value proportional to the intensity of the light emitted from the light source to the sample is detected by the second photodetector, and the second photodetector is used.
By moving an optical filter that changes the intensity of the sample irradiation light movably provided in the illumination optical system so that the output of the photodetector and a preset setting value become equal, by an optical filter moving mechanism, Even if the light source is deteriorated or mechanical displacement around the light source due to heat occurs, the intensity of the sample irradiation light is always constant, and the same effect as above can be obtained.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of an edge detecting apparatus according to the present invention, and the same parts as those in FIG. 4 are designated by the same reference numerals.

As shown in FIG. 1, the sample 1 is placed on a stage 2 which is movable in the direction of a double arrow A, that is, in the direction orthogonal to the optical axis of the objective lens 6, and one surface of the stage 2 is placed. A telecentric lighting system is provided on the side. This telecentric illumination system includes a lamp 20, a fiber guide 21, an optical system 22 that makes parallel light from a point on the end face of the fiber guide 21, and a half mirror 23, and illuminates the sample 1.

An objective lens 6, an imaging lens 7, a pinhole 8 and a photodetector 9 are arranged on the other surface side of the stage 2, and the focus of the objective lens 6 is made to coincide with the surface of the sample 1 and telecentric. The objective lens 6, the light from the illumination system,
The light is received by the photodetector 9 through the imaging lens 7 and the pinhole 8, and its output is passed through the current / voltage converter (hereinafter abbreviated as I / V converter) 16 and the reference voltage 1 in the comparator 10.
The edge detection signal is obtained by comparing with a predetermined threshold value from 1.

In the first embodiment, a photodetector 24 is provided on the transmission side of the half mirror 23 of the telecentric illumination system, and the output of this photodetector 24 is passed through a current / voltage converter 25 to a differential amplifier 26. In addition, a power supply voltage control system is configured to input the difference voltage between the output voltage of the I / V converter 25 obtained from the differential amplifier 26 and the reference voltage 27 to the lamp 20 via the differential amplifier 28. It is a thing.

In the edge detecting device having such a structure, the intensity of the light incident on the photodetector 24 is proportional to the intensity of the sample irradiation light, and the output thereof is also proportional to the intensity of the sample irradiation light.

Therefore, the differential amplifier 26 controls the brightness of the lamp 20 so that the set reference voltage 27 and the output voltage of the I / V converter 25 proportional to the sample irradiation light are always equal, and as a result, the sample irradiation is performed. The light intensity is always kept constant.

As described above, in the first embodiment, the light transmitted through the half mirror 23 of the telecentric illumination system is detected by the photodetector 2.
4 and outputs the output to the differential amplifier 26 via the I / V converter 25, and the brightness of the lamp 20 via the drive amplifier 28 by the difference voltage from the reference voltage obtained from the differential amplifier 26. Since it is controlled, even if mechanical displacement around the light source due to deterioration of the light source or heat occurs,
The intensity of the sample irradiation light is always constant, the profile of the photodetector 9 at the sample edge portion does not collapse, and the edge detection can always be performed with high accuracy while the threshold value of the reference voltage 11 remains unchanged.

Therefore, once the threshold for edge detection is set by the reference voltage 11, the set value can be held as a constant of the apparatus, so that there is no need for the conventional adjustment work such as the troublesome adjustment. Edge detection can always be performed with high accuracy.

FIG. 2 shows a second edge detection device according to the present invention.
In the configuration diagram showing the embodiment of the present invention, the same parts as those in FIG. 1 are designated by the same reference numerals. In the second embodiment, the lamp 20 that is turned on by the reference voltage 30 applied via the drive amplifier 28, the fiber guide 21 on which the light of the lamp 20 is incident, and a point on the end face of the fiber guide 21 are arranged. A telecentric illumination system is constituted by an optical system 22 that makes parallel light and a half mirror 23 that reflects the light from the optical system 22 toward the sample 1.

A continuous ND filter 33 is arranged between the fiber guide 21 and the optical system 22 of the telecentric illumination system, and the continuous ND filter 33 is rotatably connected to a motor 32.

This continuous ND filter 33 is shown in FIG.
As shown in FIG. 3, the intensity of the light incident on the optical system 22 from the fiber guide 21 can be continuously adjusted by the forward and reverse rotation by the motor 32.

The continuous ND filter 33 shown in FIG.
As shown in (b), a long one is used, and the rotation of the motor 32 is transmitted as a linear motion by a combination of a rack and a pinion so that the optical system 2 is guided by the fiber guide 21.
The intensity of the light incident on 2 may be continuously adjustable.

On the other hand, a photodetector 24 is arranged on the transmission side of the half mirror 23, and the output of this photodetector 24 is given to a differential amplifier 26 via an I / V converter 25. The obtained difference voltage between the output voltage of the I / V converter 25 and the reference voltage is input to the motor driver 31.

In the edge detecting device having such a structure, the intensity of the light incident on the photodetector 24 is proportional to the intensity of the sample irradiation light, and the output thereof is also proportional to the intensity of the sample irradiation light.

Therefore, the differential amplifier 26 compares the voltage signal proportional to the sample irradiation light with the reference voltage, and the difference voltage is given to the motor driver 31. This motor driver 3
In No. 1, the motor 32 is moved in the forward or reverse direction according to the input from the differential amplifier 26.

As a result, the set reference voltage 27 and I /
The continuous ND filter 33 is connected to the motor 32 so that the output of the photodetector 24 input via the V converter 25 becomes equal.
The result is that the intensity of the sample irradiation light is always kept constant.

Therefore, the intensity of the sample irradiation light is constant even under the occurrence of mechanical displacement around the light source due to deterioration of the light source or heat, and it is always possible to carry out the conventional calibration work without the troublesome adjustment. Edge detection can be performed with high accuracy.

[0030]

As described above, according to the present invention, since the intensity of the sample irradiation light is stabilized, the troublesomeness of the adjustment can be eliminated, and the edge detection can always be performed easily and highly accurately. An edge detection device can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an edge detection device according to the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of an edge detection device according to the present invention.

FIG. 3 is a diagram showing a configuration example of a continuous ND filter used in the same embodiment.

FIG. 4 is a curve diagram for explaining a detection error due to a change in intensity of sample irradiation light in a conventional edge detection device.

FIG. 5 is a configuration diagram showing a conventional edge detection device.

[Explanation of symbols]

1 ... Sample, 2 ... Stage, 3 ... Light source, 4 ... Fiber guide, 5 ... Optical system, 6 ... Objective lens, 7 ...
… Imaging lens, 8 …… pinhole, 9 …… photodetector, 1
0 ... Comparator, 11 ... Reference voltage, 12 ... Monitor, 2
0 ... Lamp, 21 ... Fiber guide, 22 ... Optical system, 23 ... Half mirror, 24 ... Photodetector, 25
... I / V converter, 26 ... Differential amplifier, 27 ... Reference voltage, 28 ... Drive amplifier, 30 ... Reference voltage, 31 ...
… Motor driver, 32 …… Motor, 33 …… Continuous ND
filter.

Claims (2)

[Claims] 1. An output of the photodetector while relatively moving the sample and an optical system including a first photodetector that receives light from a light source through the illumination optical system through the sample. An edge detection device for detecting an edge of the sample based on a second photodetector for detecting a value proportional to the intensity of light emitted from the light source to the sample, and an output of the second photodetector. And a voltage control means for changing the brightness of the light source so that the light source is constant. 2. The first photodetector while relatively moving the sample and an optical system including a first photodetector that receives light from a light source through the illumination optical system through the sample. An edge detection device that detects the edge of the sample based on the output of the second photodetector arranged to output a value proportional to the intensity of light emitted from the light source to the sample, An optical filter movably provided in the illumination optical system and changing the intensity of the sample irradiation light;
And an optical filter moving mechanism for moving the output of the photodetector so that it becomes equal to a preset set value.