JPH06300645A - Temperature measuring equipment - Google Patents

Abstract

PURPOSE:To provide a temperature measuring equipment in which the measurement of the temperature variation of a substrate is linearized while allowing decision of the incremental/decremental direction of temperature. CONSTITUTION:The temperature measuring equipment comprises a laser light source 1, and a photoelectric converter 5 for receiving the lights 4 reflected on the parallel surface 3a and the rear 3b of a substrate 3 when laser light 2 from a laser light source 1 impinges on the substrate 3 at an angle theta thus detecting the fringe intensity (Ir/Ii). Temperature variation of the substrate 3 is detected based on the variation of fringe intensity. A fringe intensity signal 6 outputted from the photoelectric converter 5 is proportional to the fringe intensity. An oscillation wavelength control circuit 7 receives the fringe intensity signal 6 from the converter 5 and delivers a wavelength control signal 8 for compensating the variation of the intensity signal 6 to the laser light source 1 thus varying the oscillation wavelength of the laser light 2. A temperature variation calculating circuit 9 receives the wavelength control signal 8 and calculates the temperature variation of the substrate 3 based on the variation of oscillation wavelength which is varied by the wavelength controller 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature measuring device for measuring the temperature of a substrate having parallel front and back surfaces without contacting the substrate.

[0002]

2. Description of the Related Art Conventionally, as a temperature measuring device, a laser light source, a substrate which transmits the laser light from the laser light source and whose front surface and back surface are parallel to each other, and a laser light from the laser light source are used. A photoelectric conversion unit that receives reflected light from the front surface and the back surface of the substrate when the light is incident on the substrate at a predetermined angle and detects the interference fringe intensity of the reflected light. It is known to detect the temperature change of the substrate from the change.

This conventional temperature measuring device can measure the temperature of the substrate itself, which is an object, without touching the substrate, and therefore there is no element that disturbs the measurement, and accurate measurement is possible. If there is a window glass or the like that allows laser light to pass through, it can be applied to temperature measurement in a special environment such as inside a vacuum chamber, and is extremely useful in industry.

Next, the principle of the conventional temperature measuring device will be described in detail with reference to FIG.

As shown in FIG. 2, the front surface 21a and the back surface 21
When laser light (incident light) 22 is incident on the substrate 21 parallel to b with a predetermined incident angle θ, the reflected light 23 from the front surface 21a and the back surface 21b of the substrate 21 interfere with each other. Let Ii be the intensity of the incident light 22 on the substrate 3,
Moreover, when the intensity of the reflected light 23 is Ir, the reflected light 2
The interference fringe intensity (Ir / Ii) of 3 is expressed by the following equation 1.

[0006]

[Equation 1]

The phase difference δ is expressed by the following equation 2.

[0008]

[Equation 2]

The change Δδ _T of the phase difference δ caused by the temperature change ΔT of the substrate is expressed by the following equation 3.

[0010]

[Equation 3]

Therefore, the change Δδ _T in the phase difference δ can be calculated from the change in the interference fringe intensity (Ir / Ii), and the temperature change can be calculated backward from this change.

This conventional temperature measuring device can perform highly accurate measurement without causing an error due to a temperature change of the surrounding air and a position shift of the substrate.

[0013]

However, in the conventional temperature measuring device, since the phase difference δ is an argument of a sine function as shown in equation 1, the interference fringe intensity (Ir / I
There is a problem that the relationship between the change i) and the change Δδ _T of the phase difference δ (hence the substrate temperature change ΔT) is non-linear, and the direction of increase / decrease of change cannot be determined.

An object of the present invention is to provide a temperature measuring device capable of linearizing measurement of a temperature change of a substrate and determining the direction of increase or decrease of this change.

[0015]

According to the present invention, there is provided a laser light source, a substrate for transmitting laser light from the laser light source, the front surface and the back surface of which are parallel to each other, and the laser from the laser light source. Photoelectric conversion means for receiving the reflected light from the front surface and the back surface of the substrate when the light is incident on the substrate at a predetermined angle, and detecting the interference fringe intensity of these reflected light; In a temperature measuring device that detects a temperature change of the substrate from a change in intensity, an oscillation of the laser light of the laser light source is received so as to receive the interference fringe intensity signal from the photoelectric conversion means and compensate the change in the interference fringe intensity signal. It has an oscillation wavelength control means for changing the wavelength and a temperature change calculation means for calculating the temperature change of the substrate from the change amount of the oscillation wavelength changed by the oscillation wavelength control means. Temperature measuring device is obtained.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, the temperature measuring device of the present invention includes a laser light source 1 and a substrate 3 which transmits a laser beam 2 from the laser light source 1 and whose front surface and back surface are parallel to each other.
And receiving reflected light 4 from the front surface 3a and the back surface 3b of the substrate 3 when the laser light (incident light) 2 from the laser light source 1 is incident on the substrate 3 at a predetermined angle θ. A photoelectric converter 5 for detecting the interference fringe intensity (Ir / Ii) of the reflected light 4;
The temperature change of the substrate 3 is detected from the change of Ii). The interference fringe intensity signal 6 output from the photoelectric converter 5 is proportional to the interference fringe intensity (Ir / Ii) shown in the equation (1).

The oscillation wavelength control circuit 7 includes the photoelectric converter 5
The interference fringe intensity signal 6 from the
The wavelength control signal 8 is applied to the laser light source 1 so as to compensate the change of the laser light source 1 to change the oscillation wavelength of the laser light 2 of the laser light source 1. The temperature change calculation circuit 9 receives the wavelength control signal 8 and calculates the temperature change of the substrate 3 from the change amount of the oscillation wavelength changed by the oscillation wavelength controller 7.

The temperature change calculation circuit 9 calculates the temperature change of the substrate 3 based on the following equation.

A phase change Δδ _T caused by the temperature change ΔT of the substrate 3 and a phase change Δδ caused by the change Δλ of the wavelength λ of the laser light oscillated by the laser light source 1.
_The relationship expressed by the following equation 4 is established between _w and _w .

[0021]

[Equation 4]

The phase change Δδ _w caused by the change Δλ in the wavelength λ of the laser light can be expressed by the following equation 5.

[0023]

[Equation 5]

Therefore, the temperature change ΔT can be expressed by the following equation 6 by the equations 3, 4, and 5.

[0025]

[Equation 6]

As is clear from the equation 6, the temperature change Δ
Since T is proportional to the wavelength change Δλ, the wavelength change Δ
If λ can be measured, the temperature change ΔT can be measured in a linearized form, and the increase / decrease in temperature can be determined.

Change in the interference fringe intensity signal 8 and laser light 2
If the relationship with the wavelength change Δλ of is known, the wavelength change Δλ can be calculated based on the interference fringe intensity signal 8. Based on such a relationship, the temperature change calculation circuit 9
Calculates the temperature change of the substrate 3 from the change amount of the oscillation wavelength changed by the oscillation wavelength controller 7.

A beam splitter 10 is arranged between the laser light source 1 and the substrate 3, a part of the laser light 2 from the laser light source 1 is taken out by the beam splitter 10, and a wavelength is measured by a wavelength meter 11. You can also get the value.

[0029]

The temperature measuring device of the present invention can linearize the measurement of the temperature change of the substrate and determine the direction of increase or decrease of this change.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram for explaining the principle of a conventional temperature measuring device.

[Explanation of symbols]

 1 laser light source 2 laser light 3 substrate 4 reflected light 5 photoelectric converter 6 interference fringe intensity signal 7 oscillation wavelength control circuit 8 wavelength control signal 9 temperature change calculation circuit

Claims (1)

[Claims] 1. A laser light source, a substrate that transmits laser light from the laser light source, and has front and back surfaces parallel to each other, and laser light from the laser light source at a predetermined angle with respect to the substrate. A photoelectric conversion unit that receives reflected light from the front surface and the back surface of the substrate when incident and detects the interference fringe intensity of the reflected light is provided, and changes in the temperature of the substrate due to the change in the interference fringe intensity. In the temperature measuring device for detecting, an oscillation wavelength control means for receiving the interference fringe intensity signal from the photoelectric conversion means and changing the oscillation wavelength of the laser light of the laser light source so as to compensate for the change in the interference fringe intensity signal, And a temperature change calculation means for calculating the temperature change of the substrate from the change of the oscillation wavelength changed by the oscillation wavelength control means.