JPH0526627A - Open type cell for measuring photo-acoustic signal - Google Patents

Abstract

PURPOSE:To provide an open type cell for measuring the photo-acoustic signal capable of performing the on-line measurement of a sample. CONSTITUTION:An open type cell for measuring the photo-acoustic signal has a cell main body 107a storing a microphone 108, a quartz glass tube 105a fitted to the cell main body 107a, and a laser light source 101 installed at the outside of the quartz glass tube 105a and projecting a modulated laser beam. The inner face of the quartz glass tube 105a is formed into a taper shape shrunk at an opening section 105b. The laser beam is projected to a sample 106 face at the opening section 105b through the quartz glass tube wall 105a, and the acoustic signal generated from the sample 106 face is measured with a microphone 108.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cell used for non-contact film thickness measurement and physical property measurement utilizing the photoacoustic effect.

[0002]

2. Description of the Related Art In measurement of film thickness and physical properties utilizing the photoacoustic effect, a closed cell has been conventionally used. Its structure is shown in FIG. The light emitted from the laser 101 is modulated by the chopper 102, condensed by the lens 104, transmitted through the quartz glass 105, and incident on the sample 106. The sound wave generated from the sample travels through the passage inside the cell 107, is detected by the microphone 108, is amplified by the preamplifier 109 and the lock-in amplifier 110, and is transmitted to the personal computer 111.
Is processed by.

[0003]

The above-mentioned prior art has the following problems. Since the sample is enclosed in the cell, the measurement target is greatly limited. This constraint not only limits the size of the measurement object, but also denies the possibility of online measurement.

An object of the present invention is to provide an open type photoacoustic signal measuring cell which enables online measurement of a sample.

[0005]

In the conventionally used closed cell, the sample chamber and the microphone chamber are connected by a passage and are sealed from the outside. Therefore, the sample chamber and the microphone chamber are integrated into one body, and the structure is such that the outside is not sealed. Therefore, quartz glass is used as the material of the cell near the sample to facilitate the introduction of laser light. further,
The inside of the quartz glass tube is tapered in order to minimize the volume of the part where the generated sound waves are collected by the microphone.

[0006]

The use of quartz glass as the material of the cell near the sample facilitates the introduction of laser light from the outside. Furthermore, the volume of the sound collecting part is reduced by adding a taper inside the sound collecting part that shrinks toward the sample surface,
Acoustic signals can be detected with higher sensitivity.

[0007]

EXAMPLE A laser beam emitted from an Ar ion laser 101 is modulated by a chopper 102 and introduced into an optical fiber 103. The light emitted from the fiber 103 is the lens 104.
Is collected by the sample glass 1 and transmitted through the quartz glass tube 105a.
It is incident on 06. The generated sound wave is detected by the microphone 108 fixed in the cell 107a, amplified by the preamplifier 109, measured by the lock-in amplifier 110, and processed by the personal computer 111.

The inner surface of the quartz glass tube 105a is attached to the sample 106.
To the microphone 1 from the surface of the sample 106 by reducing the taper shape toward the open part 105b at the lower end facing the.
The volume of the sound collecting section reaching 08 is reduced and the microphone 10
8 improves the measurement accuracy.

[0009]

The open cell for photoacoustic signal measurement according to the present invention is a cell body having a built-in microphone, a quartz glass tube attached to the cell body, and a laser installed outside the quartz glass tube and modulated by a chopper. A laser light source for projecting light, the inner surface of the quartz glass cylinder is formed into a tapered shape in which the opening is reduced, and the laser light is transmitted through the quartz glass cylinder wall and projected onto the sample surface of the opening, and the sample surface The following effects are obtained by the configuration in which the acoustic signal generated from the microphone is measured by the microphone.

In the prior art, since the closed type was used, the size of the object to be measured was limited and the sample capable of measuring the photoacoustic signal was limited, but by using the open type cell according to the present invention, what size It is possible to detect photoacoustic signals even for the sample, and online measurement of film thickness and physical property values becomes possible.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a configuration of an embodiment of the present invention.

FIG. 2 is a vertical cross-sectional view showing the structure of a conventional closed cell.

[Explanation of symbols]

 101 Ar Ion Laser 102 Chopper 105a Quartz Glass Tube 105b Opening 107a Cell Main Body 108 Microphone

Claims (1)

Claim: What is claimed is: 1. A cell main body having a microphone built therein, a quartz glass cylinder mounted on the cell main body, and a laser beam which is installed outside the quartz glass cylinder and modulated by a chopper. A laser light source is provided, and the inner surface of the quartz glass cylinder is formed into a tapered shape in which the opening is reduced, the laser light is transmitted through the quartz glass cylinder wall and projected onto the sample surface of the opening, and is generated from the sample surface. An open type cell for photoacoustic signal measurement, characterized in that the microphone is configured to measure an acoustic signal.