JP3160103B2 - Optical glass thickness measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates about the optical glass plate thickness measuring method.

[0002]

Conventionally, non-contact by measuring contact measuring how by micrometer or the like, semi-contact measuring how by ultrasound micrometer or the like, or the transmission attenuation of the radiation as a glass plate thickness measuring method Recently, a glass plate is irradiated with a laser beam that moves in parallel at a constant speed, and the time difference between the light reflected from the front surface and the light reflected from the back surface of the glass plate is measured. A method for non-contact measurement of plate thickness has been developed and put to practical use.

[0003]

THE INVENTION Problems to be Solved] Bee on a glass plate to be measured
The glass plate is illuminated by irradiating the glass plate with a laser beam that moves at a substantially constant speed, and measuring the detection time difference between the reflected light on the front surface and the reflected light on the back surface, which is detected by a light receiver installed on the receiving optical axis. In the method of measuring the thickness, a slight non-uniformity of the refractive index existing inside the glass plate to be measured causes an error in the detection time difference, which causes a decrease in measurement accuracy. As shown in FIG. 2, occurs deviation in the direction of the surface reflected light and the back surface reflected light detected in the light receiver by the non-uniformity of a small refractive index existing in the glass plate to be measured, the
This causes a measurement error .

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the inventor of the present invention has found that such a decrease in measurement accuracy is caused by a slight unevenness of the refractive index existing inside the glass plate to be measured. It has been found that the light reflected on the back surface is no longer parallel to the light reflected on the front surface due to the nature of the light, thereby leading to the present invention.

That is, the present invention relates to a glass to be measured which is parallel to the optical axis of an irradiation optical system and whose beam is substantially constant.
The laser beam moves along the surface of the plate was irradiated on the glass plate to be measured, test and its surface reflection light and the light reflected by the lower surface by the photodetector
Out, and the detection light of the front surface reflected light in the light receiver and the back surface
Measures the time difference between the detection light Shako, the glass from the difference between said time
A method of measuring the glass plate thickness by calculating the thickness of the glass plate, wherein the photodetectors provided at at least two different positions on the light receiving optical axis and the measuring optical system and the glass plate to be measured are provided.
Using a means to detect the distance,
Measuring the time difference and the distance
Optical glass characterized by calculating the thickness of a lath plate
Provide a method for measuring a thickness. Thus, a glass plate thickness measuring method to remove the decrease in measurement precision due to non-uniformity of a small refractive index existing in the glass plate to be measured is Ru are provided.

The details of the present invention will be described with reference to FIG . The laser light emitted from the laser light source LS is applied to the glass plate G as a light beam that moves in parallel by the rotating mirror RM and the scanning lens SL. The surface reflected light and the back reflected light is detected more in the light receiving optical axis of the at least two are located at different positions the optical receiver SD1 and the light receiver SD2 (located aft distance D _S of the light receiving unit SD1 in FIG. 1) You. The half mirror HM includes the light receiver SD1 and the light receiver S
D2 is used for the purpose of not interfering with detection
Normally, SD2 is a position to receive the reflected light of the half mirror HM.
Is provided .

[0007] The representative position of the measuring optical system is set to the photo detector SD1.Rank
PlaceToYou.This and the glass plate to be measuredGMeasuring pointWhenDistance
D, light receiver SD1 and light receiver SD2WhenDistanceD _S , Receiver
SD1 and photo detector SD2soDetectedEach light reception
In the vesselSurface reflected lightAnd the back reflection lightTime difference t₁, T_Two
From the time difference t on the surface of the glass plate to be measured₀ Is the expression
It is calculated by (1) and further calculated by equation (2).
A thickness T is obtained. t₀= T₁+ (T₁-T_Two) ・ D /D _S  (1) T = kt₀ (2)

[0008] There is no limitation to the specific method of measuring the distance D between the light receiving unit SD1 and the measurement point of the measurement the glass plate <br/>, although not a requirement of the present invention, non-contact optical methods is desirable For example, a reflective position sensor may be used. The constant k is a device constant determined by the refractive index of the measuring optical system and the glass plate to be measured. In FIG. 1, it is also possible to place a so-called relay lens RL between the light receiver on the light receiving optical axis and the glass plate to be measured, thereby increasing the distance between the measuring optical system and the glass plate to be measured. At the receiver SD
The position of 1 may be on the left side (D <0) of the glass plate to be measured.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG.
W helium neon gas laser, a lens with a focal length of 85 mm on the scanning lens SL, and a focal length of 25 mm on the light receiving optical axis
Using the relay lens RL, respectively photoreceiver SD1 and the light receiver SD2 from the relay lens RL 40 mm, 55
mm, the glass plate to be measured and the relay lens R
The distance from L was 55 mm. At this time, the relay lens
From the RL, the virtual positions of the light receiver SD1 and the light receiver SD2 are 66.666 mm and 45.833 mm, respectively, so that the position D of the light receiver SD1 is -11.666 m.
m, the distance D _S between the light receiver SD1 and receiver SD2 20.
833 mm. Using equation (1) and the above numerical values, t ₀
= A _{0.44 × t 1 + 0.56 × t} 2.

[0010] Table 1 is a value obtained with t _1, t ₂ from t ₀ was strange forte measured measurement position for each 1mm of polished glass plate having a thickness of 700 .mu.m. Variation of the measured values by more measurement positions on the onset bright is reduced, the t ₀ with high accuracy is obtained. Therefore, as shown in the above results , the thickness of the glass plate was determined with high accuracy.

[0011]

[Table 1]

[0012]

By using the method of the present invention in measuring the thickness of a glass plate, a decrease in measurement accuracy due to a slight non-uniformity of the refractive index existing inside the glass plate to be measured is reduced. In particular online measuring in the glass manufacturing process but unavoidable fluctuations in the position of the glass plate to be measured, the thickness of the more glass plates to the onset bright is obtained with high measurement accuracy. Particularly, by applying the method of the present invention to the manufacturing process, a great effect can be obtained in improving the productivity.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical system according to the present invention.

FIG. 2 is a model diagram showing an object of the present invention.

[Explanation of symbols]

 LS: Laser light source RM: Rotating mirror SL: Scanning lens SD1, SD2: Light receiver HM: Half mirror G: Glass plate to be measured D: Distance between light receiver SD1 and glass plate to be measured Ds: Distance between light receiver SD1 and light receiver SD2 Distance RL: Relay lens

Claims (1)

(57) [Claims] 1. A parallel to the optical axis of the illumination optical system, and irradiated with laser light beam travels along the <br/> substantially the surface of the measured glass plate at a constant speed on a glass plate to be measured, and the surface reflected light and the light reflected by the lower surface is detected by the light receiver, the light receiver
A method of measuring the time difference between the detection light of the front surface reflected light and the detection light of the back surface reflected light, and measuring the glass plate thickness by calculating the glass plate thickness from the time difference , using means for detecting a distance of at least two different light receiver provided at a position and the measuring optical system and the measured glass plate on the light receiving optical axis, the time difference in each of the light receiver and the distance <br/> away An optical glass sheet thickness measuring method, wherein the thickness of a glass sheet to be measured is calculated by measuring.