JPH0566114A - Thickness measuring device for transparent material - Google Patents

Abstract

PURPOSE:To measure the one-dimensional thickness distribution of a transparent sheet at high speed by conducting scanning in such a manner as to move an optical beam on the surface of a material to be measured by a rotating mirror and an optical system, and imaging each of the surface reflected light and bottom reflected light obtained by the scanning onto an image sensor through the rotating mirror. CONSTITUTION:A semiconductor laser 7, a rotating flat mirror 9 receiving the laser beam from the semiconductor laser 7 and emitting it according to rotation, and a projecting lens 10 and reflecting mirror 11 for radiating the optical beam from the rotating flat mirror 9 to a material 6 to be measured of a transparent sheet are provided. Further, a reflecting mirror 12 and converging lens 13 for guiding again the surface reflected light 15 and bottom reflected light 16 of the material 6 to be measured to the laser beam from the reflecting mirror 11 to the rotating flat mirror 9, and an image sensor 14 for receiving each of the two reflected lights from the rotating flat mirror 9 to the optical beam from the converging lens 13 are provided to form a thickness measuring device for transparent material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for measuring the thickness of a transparent object such as a transparent sheet, and more particularly, to the thickness of a reflected laser beam obtained by irradiating the surface of the object to be measured with a laser beam. It relates to effective techniques used to make measurements.

[0002]

2. Description of the Related Art For example, the thickness of transparent sheets used as spacers, transparent glass used in optical systems, etc. must be strictly controlled. As for the device for measuring the thickness of this type of product, all the devices currently on the market perform spot measurement.

Therefore, in order to measure the one-dimensional or two-dimensional surface condition, that is, the thickness distribution, a mechanical slide mechanism is required.

FIG. 3 is a perspective view showing a schematic structure of a conventional thickness measuring device.

The thickness measuring device 1 has an L-shaped arm 2
Is attached to one end of the XY stage 3 and the other end is fixed to the XY stage 3. This XY stage 3 includes a motor 4,
The thickness measuring device 1 is driven by 5 in two orthogonal directions.
Can be moved.

An object to be measured 6 (transparent sheet), which is an object to be measured, is arranged immediately below the thickness measuring device 1.

At the time of measurement, the DUT 6 is fixed, and the XY stage 3 is driven by the motors 4 and 5,
The thickness measuring device 1 is positioned on the measurement starting point of the DUT 6. Here, a light beam is emitted from the thickness measuring device 1 to irradiate the surface of the DUT 6, and the reflected laser light is made incident on the photodetector (for example, CCD sensor) of the thickness measuring device 1. The light detector simultaneously detects the light reflected on the surface of the transparent sheet and the light reflected on the bottom surface of the transparent sheet, and can measure the thickness of the transparent sheet from the distance between the two image formation points on the sensor. it can.

In this state, the thickness measuring device 1 is continuously moved in one direction (for example, the X direction) by the XY stage 3 to perform one-dimensional scanning. When scanning from one end to the other end of the DUT 6 is completed, the thickness measuring device 1 is moved in the Y direction by a predetermined pitch, and the thickness measuring device 1 is moved again in the X direction. Thereafter, the DUT 6 is similarly measured.
A one-dimensional thickness distribution can be measured by scanning the entire surface of.

[0009]

According to the study by the present inventor, the surface displacement measuring technique for mechanically moving the thickness measuring device to measure the displacement requires a slide mechanism.
There is a problem that the measurement takes time (that is, high speed cannot be achieved), it cannot be used in-line, and the device becomes large and heavy.

Therefore, an object of the present invention is to provide a technique capable of rapidly measuring the one-dimensional thickness distribution of a transparent sheet.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0012]

Among the inventions disclosed in the present application, a brief description will be given to the outline of typical ones.
It is as follows.

That is, a rotating mirror that is rotatably installed and that emits a light beam that is incident according to the rotation, and a first optical device that irradiates a sheet-like object to be measured with the light beam from the rotating mirror. A system, a second optical system that guides the surface reflected light and the bottom surface reflected light from the object to be measured to the rotating mirror, and two reflected light from the rotating mirror with respect to the light beam from the second optical system. An image sensor for receiving each light is provided.

[0014]

According to the above-mentioned means, the light beam is radiated through the rotary mirror to the object to be measured so as to scan according to the rotation speed of the rotary mirror, and the surface reflected light from the surface of the object to be measured accompanying this scanning. And the bottom reflected light are incident on the mirror surface of the same rotating mirror, and each of them is imaged as two spots on the image sensor. Therefore, one-dimensional thickness distribution measurement can be performed at high speed. Moreover, it is possible to reduce the size and cost of the device.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a perspective view showing the schematic construction of an embodiment of the thickness measuring apparatus for transparent objects according to the present invention.

A collimator lens 8 and a rotating plane mirror 9 (rotating mirror) are sequentially arranged on an emission optical path of a laser beam of a semiconductor laser 7 which is a measuring light source. The rotating plane mirror 9 is configured such that the rotating shaft 9a is fixed in parallel to the center of the horizontally long plane mirror and can rotate. On the reflection optical path of the rotating plane mirror 9, a light projecting lens 10 for forming an image of a laser beam on the DUT 6 (for example, a transparent sheet) is arranged. A reflecting mirror 11 for irradiating the laser beam from the light projecting lens 10 onto the DUT 6 in an oblique direction (the angle is set to be a critical angle or more with respect to the DUT 6) on the outgoing optical path. (Plane mirror) is provided. The reflecting mirror 11 and the light projecting lens 10 form a first optical system.

The laser beam emitted from the reflecting mirror 11 is reflected on the object 6 to be measured, and the reflecting mirror 12 (planar mirror) for reflecting the reflected laser light in the vertical direction is present on the optical path of the reflected laser light. ) Is provided. A condenser lens 13 for forming an image on the detection position is provided on the exit optical path.
Is arranged (the second optical system is formed by the condenser lens 13 and the reflecting mirror 12), and the emitted light is guided to the rotating plane mirror 9 and further imaged on the image sensor 14.

The formation of the path of the laser beam in the above structure will be described with reference to FIG. In addition,
In FIG. 2, the rotary plane mirror 9 is not shown for convenience of description.

The laser beam emitted from the semiconductor laser 7 is incident on the reflecting mirror 11 from the vertical direction via the light projecting lens 10. The light emitted from the reflecting mirror 11 is projected onto the surface of the DUT 6 at an angle θ equal to or greater than the critical angle (for example, 41.5 °> θ when the DUT 6 is a glass material). ..
The reflected laser light generated in response to this projection is two, that is, the surface reflected laser light 15 on the surface of the DUT 6 and the bottom surface reflected laser light 16 on the bottom surface, and the bottom surface is totally reflected. The reflected laser light of each of the surface-reflected laser light 15 and the bottom-reflected laser light 16 is imaged as a spot on a different position of the image sensor 14 via its own optical path through the reflecting mirror 12 and the condenser lens 13. Therefore, the thickness of the DUT 6 can be measured from the distance between the two spots.

In the above description, the rotary plane mirror 9 is not rotated for the sake of convenience of description, but it is actually rotated in the direction of the arrow, and the emitting angle of the rotary plane mirror 9 to the laser beam from the semiconductor laser 7 is It changes according to the rotation of the rotating plane mirror 9. The emitted light is reflected by the reflecting mirror 11.
It is reflected so that it enters the DUT 6 at an angle of θ. Therefore, the light emitted from the reflecting mirror 11 is reflected by the rotating plane mirror 9
In accordance with the rotation, the object 6 is continuously moved in the direction of the arrow on the surface of the object 6, that is, a unitary scanning is performed. Along with this, the reflected laser light (the surface reflected laser light 15 and the bottom reflected laser light 16) also moves in the same direction along with the movement of the light emitted from the reflecting mirror 11, and the reflected laser light is reflected by the reflecting mirror 12 and the condenser lens 13. The light emitted from the rotary plane mirror 9 is imaged as spots of the front surface reflection laser light 15 and the bottom surface reflection laser light 16 on the image sensor 14 at positions separated from each other. Although this image forming position interval changes according to the change in thickness, it is irrelevant to the rotating state of the rotary plane mirror 9, and is always emitted toward the image sensor 14 when the rotary plane mirror 9 rotates.

As described above, according to the above-described embodiment, it is not necessary to mechanically move the thickness measuring device, and the scanning speed is determined by the rotation speed of the rotary flat mirror 9, so that the thickness measurement can be performed at high speed. become. Further, since only the rotary plane mirror 9 is the target to be driven and the other optical elements can be fixed, the size of the apparatus can be reduced, and a slide mechanism such as a moving table is not required, so that the cost can be reduced. become.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited to the embodiments and various modifications can be made without departing from the scope of the invention. Needless to say. For example,
In order to further increase the scanning speed, a rotary polygon mirror may be used instead of the rotary flat mirror 9.

Further, in the structure of FIG. 1, the structure in which the reflecting mirror 12 is removed may be adopted.

In this case, the condenser lens 13 and the image sensor 14 are arranged in a straight line with respect to the optical path of the reflected laser light from the DUT 6.

In the above description, the case where the invention made by the present inventor is mainly applied to the sheet-shaped component of the semiconductor device which is the field of application of the invention has been described. It can be applied to all, and is not limited to a sheet-like object.

[0026]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.
It is as follows.

That is, a rotating mirror that is rotatably installed and that emits a light beam that is incident according to the rotation, and a first optical that irradiates a sheet-shaped object to be measured with the light beam from the rotating mirror. A system, a second optical system that guides the surface reflected light and the bottom surface reflected light from the object to be measured to the rotating mirror, and two reflected light from the rotating mirror with respect to the light beam from the second optical system. Since the image sensor for receiving each light is provided, the one-dimensional thickness distribution measurement can be performed at high speed. Moreover, it is possible to reduce the size and cost of the device.

[Brief description of drawings]

FIG. 1 is a perspective view showing a schematic configuration of an embodiment of a transparent object thickness measuring apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing the measurement principle of the thickness measuring device for a transparent object according to the present invention.

FIG. 3 is a perspective view showing a schematic configuration of a conventional thickness measuring device.

[Explanation of symbols]

 1 Thickness Measuring Device 2 Arm 3 XY Stage 4 Motor 5 Motor 6 Object to be Measured (Transparent Sheet) 7 Semiconductor Laser 8 Collimating Lens 9 Rotating Flat Mirror 9a Rotating Axis 10 Projection Lens 11 Reflecting Mirror (Plane Mirror) 12 Reflecting Mirror (Plane Mirror) ) 13 condensing lens 14 image sensor 15 surface reflection laser light 16 bottom reflection laser light

Claims (3)

[Claims] 1. A rotating mirror which is rotatably installed and emits a light beam incident in response to the rotation, and a first optical system which irradiates a transparent object to be measured with the light beam from the rotating mirror. A second optical system for guiding the surface reflected light and the bottom surface reflected light from the object to be measured to the rotary mirror; and two reflected lights from the rotary mirror with respect to the light beam from the second optical system. An apparatus for measuring the thickness of a transparent object, comprising: an image sensor for receiving light. 2. The thickness measuring device for a transparent object according to claim 1, wherein the rotating mirror is a rotating plane mirror or a polygon mirror. 3. An apparatus for measuring the thickness of a transparent object, wherein the incident angle of the light beam with which the object to be measured is irradiated is not less than the critical angle of the object to be measured.