JPH04310815A - Laser type height measuring apparatus - Google Patents

Abstract

PURPOSE:To eliminate an error in measurement due to a change in the quantity of reflected light from the surface of a substance to be measured. CONSTITUTION:A laser light from a linear polarization laser light source 1 is projected by a projecting lens 4 onto a substance 5 to be measured. A reflected light from the surface of the substance 5 is condensed on a one- dimensional PSD sensor 7 by a light-sensing lens 6. Output signals from the opposite ends of the one-dimensional PSD sensor 7 are computed by a subtracter 8, an adder 9 and a divider 10 and thereby a height signal (b) is determined. Between the linear polarization laser light source 1 and a light-projecting lens 4, an electro-optical crystal element 2 rotating the direction of polarization of the laser light according to a light qnantity signal (a) and a polarizing plate 3 disposed in combination with the electro-optical crystal element 2 so that all of the laser lights be transmitted when the light quantity signal (a) is zero are interposed, and thereby a change in the quantity of the reflected light due to the state of the surface of the substance 5 to be measured and others is reduced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser height measuring device.

0002

[Prior Art] A conventional laser height measuring device includes a light projection lens for projecting laser light from a laser light source onto an object to be measured, and a light receiving lens for condensing the reflected light from the surface of the object to be measured. A lens, a one-dimensional position detection element that detects the focused beam spot position by the light receiving lens, a subtracter that subtracts output signals from both ends of the one-dimensional position detection element, and output signals from both ends of the one-dimensional position detection element. and a divider that calculates a height signal from the output of the subtracter and the output of the adder.

Next, a conventional laser height measuring device will be explained in detail with reference to the drawings. FIG. 2 is an optical path diagram showing an example of a conventional laser height measuring device.

The conventional laser height measuring device shown in FIG. a light-receiving lens 6 that focuses light; a one-dimensional position detection element 7 that detects the position of the focused beam spot by the light-receiving lens 6;
A subtracter 8 that subtracts the output signals from both ends of the one-dimensional position detection element 7, an adder 9 that adds the output signals from both ends of the one-dimensional position detection element 7 and outputs a light amount signal a, and a subtracter 8.
and a divider 10 that calculates a height signal b from the output of the adder 9 and the output of the adder 9.

[0005]

[Problems to be Solved by the Invention] The above-described conventional laser-type height measuring device uses one-dimensional position detecting element 7 to prevent deterioration in height measurement accuracy due to changes in the amount of light reflected from the surface of object 5.
The output signals from subtracter 8, adder 9, and divider 1
The structure is configured to prevent this by normalizing using 0. However, if there is a large change in the amount of reflected light from the surface of the object to be measured 5, the range of the input signal to the divider 10 becomes large, and the There was a drawback that it became difficult to guarantee the accuracy of height measurement.

[0006]Also, in order to prevent the above-mentioned drawbacks, it is possible to use a semiconductor laser as a laser light source and adjust the light intensity by changing its output. If the aperture is too narrow, the oscillation becomes unstable, causing fluctuations in the amount of light, and the thermal equilibrium is disrupted, causing the optical axis to change, making accurate measurements impossible.

[0007]

[Means for Solving the Problems] The laser height measuring device of the present invention includes a projection lens for projecting laser light from a linearly polarized laser light source onto an object to be measured; A light receiving lens that collects reflected light, a one-dimensional position detecting element that detects the position of the focused beam spot by the light receiving lens, a subtractor that subtracts output signals from both ends of the one-dimensional position detecting element, and a one-dimensional position detecting element. An adder that adds the output signals from both ends of the element and outputs a light intensity signal, a divider that calculates a height signal from the output of the subtracter and the output of the adder, and a divider that rotates the polarization direction of the laser beam using the light intensity signal. It is configured to include an electro-optic crystal element and a polarizing plate arranged in combination with the electro-optic crystal element so that all laser light is transmitted when the light amount signal is zero.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained in detail with reference to the drawings. FIG. 1 is an optical path diagram showing an embodiment of the present invention.

The laser-type height measuring device shown in FIG. A light receiving lens 6 that collects light, a one-dimensional position detecting element 7 that detects the position of the focused beam spot by the light receiving lens 6, and a subtracter 8 that subtracts output signals from both ends of the one-dimensional position detecting element 7. an adder 9 that adds output signals from both ends of the one-dimensional position detection element 7 and outputs a light amount signal a; a divider 10 that calculates a height signal b from the output of the subtracter 8 and the output of the adder 9; an electro-optic crystal element 2 having a property of rotating the polarization direction of the laser beam according to the light amount signal a;
It is configured to include a polarizing plate 3 arranged in combination with an electro-optic crystal element 2 so that all the laser beams are transmitted when the light amount signal a is zero.

0010

[Effects of the Invention] The laser height measuring device of the present invention measures the amount of light reflected from the object to be measured to the one-dimensional position detection element, and measures the amount of light incident on the object according to the magnitude of the light amount signal using an electro-optical method. By changing the amount of reflected light with a type of variable filter that is a combination of a crystal element and a polarizing plate, it is possible to suppress changes in the amount of reflected light due to the surface condition of the object to be measured. This has the effect of making it possible to perform high-precision measurements.

[Brief explanation of drawings]

FIG. 1 is an optical path diagram showing one embodiment of the present invention.

FIG. 2 is an optical path diagram showing a conventional example.

[Explanation of symbols]

1 Laser light source 2 Electro-optic crystal element 3 Polarizing plate ４　　　　　　Flooding lens 5 Object to be measured 6. Condensing lens 7 One-dimensional position detection element 8 Subtractor 9 Adder 10 Divider a Light amount signal b Height signal

Claims (1)

[Claims] 1. A light projecting lens for projecting laser light from a linearly polarized laser light source onto an object to be measured, a light receiving lens for condensing reflected light from the surface of the object to be measured, and a light receiving lens configured by the light receiving lens. A one-dimensional position detection element that detects the focused beam spot position, a subtracter that subtracts the output signals from both ends of the one-dimensional position detection element, and a light amount signal that adds the output signals from both ends of the one-dimensional position detection element. an adder for outputting an output, a divider for calculating a height signal from the output of the subtracter and the output of the adder, an electro-optic crystal element for rotating the polarization direction of the laser beam according to the light amount signal, and a light amount signal of zero. 1. A laser height measuring device comprising: a polarizing plate arranged in combination with an electro-optic crystal element so that all laser light passes through in the case of .