JPH01169307A - Gap measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain a gap measuring apparatus characterized by a simple structure and less measuring errors, by forming a mirror surface of one of two parts, whose gap is to be measured, using a transparent body for the other part, vibrating the transparent body, and detecting the reflected light of laser light. CONSTITUTION:Of two parts, whose gap DELTAL is to be measured, a first part 1 is provided so as to have a mirror surface, and a second part 2 is provided as a transparent body. A laser diode 4 and an objective lens 3 are provided so that laser light can be projected on the first part 1 through the second part 2. A photodetector 5 which detects the reflected light is provided. A coil 6, a magnet 7 and an AC power source 9 are provided so as to impact vibration to the objective lens 3. The change of the reflected light when the objective lens 3 is vibrated is detected with the photodetector 5 and a current measuring device 8. The DELTAL is detected based on the detected value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gap measuring device suitable for measuring minute gaps on the order of submicrons to microns.

[Conventional technology]

A conventional gap measuring device using optical interference is disclosed in Japanese Patent Application Laid-open No. 150807/1983.

The above invention independently detects optical interference caused by two or more wavelengths, converts the detected signal into A/DK, and then uses an arithmetic and control unit to standardize the interference light intensity and obtain the interference order. This is to find the minute gap distribution.

Additionally, Japanese Patent Application Laid-Open No. 60-55804 is a device that measures the thickness of an object by detecting the focal point of a laser beam.
By irradiating the output light of the optical pickup onto the reference plane and the object to be measured placed on the reference surface, the difference in focus control signals between the two is obtained, and the thickness of the object to be measured is measured.

[Problem that the invention seeks to solve]

Among the above-mentioned conventional techniques, those using optical interference must use light of multiple wavelengths to determine the order of interference fringes, which complicates the structure of the light irradiation system and the processing of detection signals.

In addition, in devices that detect the focal point of laser light, the optical systems on the irradiation side and the light receiving side are different, so it is necessary to place the receiver accurately at the conjugate position of the emitter, making it difficult to adjust and handle the device. Caution was required, and receiver position errors could affect measurement errors.

SUMMARY OF THE INVENTION An object of the present invention is to obtain a gap measuring device that has a simple configuration and has few measurement errors.

[Means for solving problems]

The above purpose is to arrange one laser diode and a lens so that the mirror surface is irradiated with laser light through the transparent body, one of the two parts constituting the gap is a mirror surface, and the other is a transparent body. A coil, a magnet, and an AC power source are provided to vibrate the lens in the optical axis direction, and a light receiving element is placed near the laser diode to monitor the optical output of the laser diode, and the output of the light receiving element is detected. This is achieved by providing a measuring device that

[Effect]

In the gap measuring device configured as described above, the moment when the laser beam irradiated onto the mirror surface of the first component is focused on the boundary surface due to the vibration of the lens, and the moment when the laser beam irradiated on the mirror surface of the first component is focused on the boundary surface, In each case, the reflected light returns to the laser diode and refocuses at the position of the laser diode 0, as described above.
When laser light with the same frequency returns to the oscillating laser diode, the oscillation is disturbed, and as a result, the output of the light receiving element that monitors the laser light fluctuates. Therefore, the time difference between the output fluctuation of the light receiving element caused by the reflected light from the mirror surface of the first component and the output fluctuation caused by the reflected light from the mirror surface of the transparent body, which is the second component, is observed. By calculating the product of the vibration velocity and the vibration velocity of the lens determined in advance), it is possible to measure the gap between the mirror-side surfaces of the first component and the second component.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a gap measuring device according to the present invention, and FIG. 2 is a diagram showing a screen of an oscilloscope in the above embodiment. In FIG. 1, a second component 2 made of a transparent body with a half-mirror surface 2a facing the mirror surface 1a of the tenth component 1 is placed oppositely, and the second component 2 is transmitted through the second component 2 to form the first component 1. A laser diode 4, a collimating lens 12,
An objective lens 6 is provided. Furthermore, a light receiving element 5 is provided near the laser diode 4 in the same package as the laser diode 4, and an amplifier 14 and a hyoscilloscope 15 are provided as a current measuring device 8 for measuring the output of the light receiving element 5. 0 In addition, in order to vibrate the objective lens 5, a coil 6 fixed to the objective lens 3 and a permanent magnet 7 fixed to a frame (not shown) are provided, and an AC power source 9 and an AC power source 9 for passing a current through the coil 6 are provided. The laser diode 4 is provided with a DC power supply 10 for supplying current to the laser diode 4.

In the above configuration, when a current is applied to the laser diode 4 to cause it to emit light, and an alternating current is applied to the coil 6 to vibrate the objective lens 3 in the optical axis direction, the focus of the laser beam is focused on the mirror surface 1a of the first component. When the reflected light from the mirror surface 1a passes through the same path as the incident light, it reaches the laser diode 4K.
Also, when the focus of the laser beam meets the half mirror surface 2a of the second component 2, the above-mentioned half mirror surface 2a
The reflected light returns to the laser diode 4 through the same path as the incident light. In the above two cases, when the reflected light returns to the laser diode 4, the laser diode 4
The oscillation state of changes. The change in the oscillation state is captured by the light receiving element 5, amplified by the amplifier 14, and then observed with an oscilloscope (the signal capturing the change in the oscillation state due to the returned light is generally called a scoop signal).

FIG. 2 is a diagram showing the screen of the oscilloscope 15 in FIG.
The output signal 16 of shows two changes (scoop signal). The above two changes are caused by the mirror surface 1a of the first component 1.
a scoop signal 17 due to reflection from the mirror surface 2a of the second component 2, and a scoop signal 18 due to reflection from the half mirror surface 2a of the second component 2. The above two scoop signals 17. By measuring the time difference Δt of 18 and multiplying the above Δt by the pre-measured vibration speed of the objective lens 5, it is possible to accurately measure the microscopic distance ΔL.

In addition, if a liquid or adhesive is present in the micro gap JL,
When the refractive index of the second component is close to that of the transparent body 2, excellent reflected light can be obtained by forming the surface 2a of the transparent body 2 facing the first component into a half mirror.

In addition, the present invention is not limited to the measurement of gaps as described above.
Needless to say, it can also be used to measure film thickness.

〔Effect of the invention〕

As described above, the gap measuring device according to the present invention includes a first component having a mirror surface, a second component made of a transparent body placed opposite to the mirror surface of the first component, and a second component that transmits light through the second component. first
a laser diode and an objective lens arranged so as to irradiate light onto the mirror surface of the component, a light receiving element provided near the laser diode, a measuring device for measuring the output of the light receiving element, and vibrating the objective lens. Therefore, by having a coil and a magnet, one of which is fixed to the objective lens, and an AC power source that supplies current to the coil, it is necessary to use monochromatic light and take into account chromatic aberration in the lens, transparent body, etc. In addition, the irradiated light and the reflected light pass through the same optical system, and the reflected light is directly detected by the emitter laser diode, so the emitter and receiver cannot be placed at conjugate positions like in the past. It is possible to obtain a gap measuring device that does not require accurate positioning, has a simple optical system, does not require adjustment, and is easy to handle.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a gap measuring device according to the present invention, and FIG. 2 is a diagram showing a screen of an oscilloscope in the above embodiment. DESCRIPTION OF SYMBOLS 1... First component, 2... Second component, 3... Objective lens, 4... Laser diode, 5... Light receiving element, 6... Coil, 7... Magnet , 8... Current measuring device % 9... AC power supply.

Claims (1)

[Claims] 1. A first component having a mirror surface, a second component made of a transparent body placed opposite to the mirror surface of the first component, and light passing through the second component to the mirror surface of the first component. A laser diode and an objective lens arranged so as to be able to irradiate the laser diode, a light receiving element provided near the laser diode, a measuring device for measuring the output of the light receiving element, and one of which is connected to the objective lens in order to vibrate the objective lens. A gap measuring device having a coil and a magnet fixed to the coil, and an alternating current power source supplying current to the coil.