JPH04213053A - Photo-acoustic microscope - Google Patents

Abstract

PURPOSE:To realize a highly reliable photo-acoustic microscope which has excellent operability, can measure the surface image of a sample and the image of a defect in the inside at the same time, and can perform high-speed scanning. CONSTITUTION:The internal defect of a sample can be measured without destruction with a photo-acoustic microscope. In this photo-acoustic, microscope 1, an optical part 2 of the photo-acoustic microscope 1 is simply assembled into an optical microscope. The scanning of laser light is performed by moving the laser light using an objective-lens driving circuit in relation to the movement of a sample 3c with an x-y stage 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoacoustic microscope capable of non-destructively measuring internal defects in a sample.

0002

2. Description of the Related Art Generally, when an object is irradiated with intermittent light, the object repeatedly expands and contracts, causing pressure fluctuations in and around the object (photoacoustic effect). Using the photoacoustic signal generated by this photoacoustic effect, an image of the sample can be obtained by scanning the sample surface with intermittent light focused by an optical microscope or the like.

FIG. 4 is a block diagram showing a conventional example of a photoacoustic microscope that utilizes such a photoacoustic effect. In FIG. 4, a laser beam emitted from a laser 11 receives a modulation signal from an oscillator 13, is modulated by an acousto-optic element 12, is focused by an objective lens 14, and is transmitted to a sealed chamber of a photoacoustic cell 15. A sample 153 placed on a substrate 152 is irradiated through an optical window 151. A portion of this light is reflected by the surface and the rest is absorbed by the sample 153. The absorbed light energy is converted into heat and diffused into the sample 153. A part of the diffused heat is transmitted to the gas near the surface of the sample 153, and the gas expands and contracts. Therefore, the pressure inside the sealed chamber 152 increases,
Photoacoustic waves are generated. This is detected by the microphone 154, and the photoacoustic signal from the microphone 154 is amplified by the lock-in amplifier 17 in synchronization with the modulation frequency. The photoacoustic cell 15 receives xy2 by the xy stage 16.
Dimensional scanning is performed, and the output of the lock-in amplifier 17 at this time is taken into the computer 18, and after data processing, a photoacoustic image is displayed on the television monitor 19. Since the size of the photoacoustic signal changes depending on the presence or absence of defects inside the sample, internal defects in the sample can be measured non-destructively using a photoacoustic image.

0004

[Problems to be Solved by the Invention] However, in the photoacoustic microscope shown in the above-mentioned prior art, generally the photoacoustic image (
Because the scanning time to obtain an image of internal defects in the sample is long,
It takes too much time to search and match the area you want to measure. Furthermore, when observing in comparison with an optical microscope image (surface image of a sample), alignment is difficult because the images are measured using separate devices. Furthermore, since the position of the laser spot on the sample surface cannot be observed, it is difficult to measure the photoacoustic signal of only a specific minute point, and thus conventional photoacoustic microscopes have poor operability.

The present invention has been made in view of the problems of the prior art described above, and by incorporating the optical section of a photoacoustic microscope into an optical microscope, it is easy to operate and allows the surface image and internal defect image of a sample to be easily visualized. The purpose of this is to provide a photoacoustic microscope that can perform simultaneous measurements and scan by moving the irradiation light without changing the sample position, allowing high-speed scanning and high reliability. be.

[0006]

[Means for Solving the Problems] A first configuration of the present invention for solving the above problems is equipped with an objective lens revolver, an epi-illumination system, and a television camera, and displays an optical microscope image of a sample surface on a television monitor. an optical microscope equipped with a semiconductor laser, a collimator lens, and an objective lens, and an optical section fixed to an objective lens revolver of the optical microscope;
A photoacoustic cell equipped with an optical window and a sealed chamber in which a sample is placed, a microphone for detecting photoacoustic waves, an xy stage to which the photoacoustic cell is fixed and scans in two dimensions, and a semiconductor layer in the optical section. - an oscillator and a semiconductor laser drive circuit for modulating the output light of the photoacoustic cell; a lock-in amplifier for amplifying the output signal of the microphone of the photoacoustic cell in synchronization with the modulation frequency; stay
and a computer which receives an output signal of a lock-in amplifier when xy two-dimensional scanning is performed by a camera, and displays a photoacoustic image on the television monitor after processing the data. It is. The second configuration includes an optical section that includes a semiconductor laser, a collimator lens, an objective lens, and a driving section thereof, an optical window, a sealed chamber in which a sample is placed, and a microphone that detects photoacoustic waves. The photoacoustic cell and the objective lens of this optical section are
A lens drive circuit for driving in two dimensions, an oscillator and semiconductor laser drive circuit for modulating the output light of the semiconductor laser of the optical section, and an output signal of the microphone of the photoacoustic cell synchronized with the modulation frequency. A lock-in amplifier amplifies the sample, and the output signal of the lock-in amplifier is input. After data processing, a photoacoustic image of the sample is displayed on a television monitor, and the data is sent to the lens drive circuit. The objective lens of the optical section is driven by the lens drive circuit in two dimensions, xy, to drive the semiconductor laser of the optical section that irradiates the photoacoustic cell.
This is characterized in that the output light from the sensor is scanned.

[0007]

[Operation] According to the present invention, by attaching the optical part of the photoacoustic microscope to the objective lens revolver of the optical microscope,
The structure allows the photoacoustic microscope to be easily incorporated into an optical microscope. In addition, the beam splitter in the optical section allows simultaneous irradiation of the epi-illumination light of the optical microscope and the laser light of the photoacoustic microscope, making it possible to measure the photoacoustic image and the optical microscope image at the same time, and to simplify the measurement area. can be explored. Furthermore, by changing the scanning of the laser beam from moving the sample to moving the laser beam using a lens drive circuit,
High-speed scanning is possible, and reliability is improved because no vibration is applied to the sample or microphone.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below based on the drawings. FIG. 1 is a block diagram showing a first embodiment of the photoacoustic microscope of the present invention. In FIG. 1, reference numeral 1 denotes an optical microscope, which is composed of an objective lens revolver 1a to which an objective lens is attached, an epi-illumination system 1b, and a television camera 1c. 2 is an optical section of the photoacoustic microscope, which includes a semiconductor laser 2a, a collimator lens 2b, a beam splitter 2c, and an objective lens 2.
Consists of d. The optical section 2 of this photoacoustic microscope is fixed to the objective lens revolver 1a of the optical microscope 1 using an objective lens screw (not shown). 3 is a photoacoustic cell, which is composed of an optical window 3a, a sealed chamber 3b, a sample 3c installed in the sealed chamber 3b, and a microphone 3d for detecting photoacoustic waves. 4 is an xy stage to which a photoacoustic cell 3 is fixed, and scans the photoacoustic cell 3 in two dimensions, xy. 5 is a semiconductor laser drive circuit connected to the semiconductor laser 2a, 6 is an oscillator for modulating the output light of the semiconductor laser 2a, and 7 is an amplification of the output signal of the microphone 3d in synchronization with the modulation frequency. It is a lock-in amplifier. Note that the oscillator 6 is connected to the semiconductor laser drive circuit 5 and the lock-in amplifier 7. 8 is a computer, and 9 is a television monitor. The computer 8 is connected to the lock-in amplifier 7, the xy stage 4, and the television monitor 9, and the television monitor 9 is connected to the television camera 1c of the optical microscope 1.

In such a configuration, the illumination light from the epi-illumination system 1b of the optical microscope 1 passes through the beam splitter 2c of the optical section 2, and is directed to the photoacoustic cell 3 by the objective lens 2d.
The sample 3 installed in the sealed chamber 3b through the optical window 3a of
uniformly illuminate c. The reflected light from the sample 3c passes through the objective lens 2d of the optical section 2 and the beam splitter 2c, and forms an image on the television camera 1c of the optical microscope 1. The surface image of the sample 3c captured by the television camera 1c can be observed on the television monitor 9. On the other hand, the laser light emitted from the semiconductor laser 2a of the optical section 2 passes through the collimator lens 2b and is reflected by the beam splitter 2c. The reflected light is narrowed down by the objective lens 2d and passed through the photoacoustic cell 3.
The light passes through an optical window 3a and is irradiated onto a sample 3c placed in a sealed chamber 3b. The laser beam reflected from sample 3c is
The light passes through the objective lens 2d of the optical section 2 and the beam splitter 2c, and is imaged on the television camera 1c of the optical microscope 1. The laser spot position on the surface of the sample 3c is shown on the TV monitor 9.
It can be observed by Further, in response to the modulation signal from the oscillator 6, the laser light emitted from the semiconductor laser 2a of the optical section 2 is modulated by the semiconductor laser drive circuit 5. This modulated laser light intermittently heats the sample 3c,
The gas layer on the surface of the sample 3c expands and contracts. Therefore, the pressure inside the sealed chamber 3b increases and photoacoustic waves are generated. This photoacoustic wave is detected by the microphone 3d, and the signal from the microphone 3d is transmitted to the lock-in amplifier 7.
Amplified in synchronization with the modulation frequency. The photoacoustic cell 3 is x
The y stage 4 performs xy two-dimensional scanning, and the output of the lock-in amplifier 7 at this time is taken into the computer 8 and used as data.
After the data processing, the photoacoustic image is displayed on the television monitor 9 as a photoacoustic image. When there is a defect inside the sample 3c, the photoacoustic signal becomes large, so the internal defect can be measured non-destructively.

FIG. 2 is a block diagram showing a second embodiment of the photoacoustic microscope of the present invention, and FIG. 3 is a schematic block diagram for explaining xy scanning of the apparatus shown in FIG. Here, with the apparatus shown in FIG. 1, we were able to realize a photoacoustic microscope with good operability and the ability to simultaneously measure the surface image and internal defect image of a sample. Photoacoustic cell 3 xy
It was a method of moving by stage 4. This xy
Since it takes time to move the stage 4 and the sample 3c vibrates due to the movement, there is a problem in that high-speed scanning is not possible. The second embodiment is based on this point.

Returning to FIG. 2, 2 is an optical section of the photoacoustic microscope, which is composed of a semiconductor laser 2a, a collimator lens 2b, an objective lens 2d, and an objective lens drive section 2e that moves the objective lens 2d in the x and y directions. be done. 3 is a photoacoustic cell, which is composed of an optical window 3a, a sealed chamber 3b, a sample 3c installed in the sealed chamber 3b, and a microphone 3d for detecting photoacoustic waves. 5 is a semiconductor laser drive circuit connected to the semiconductor laser 2a, 6 is an oscillator for modulating the output light of the semiconductor laser 2a, and 7 is a microphone 3.
This is a lock-in amplifier that amplifies the output signal of d in synchronization with the modulation frequency. Note that the oscillator 6 is connected to the semiconductor laser drive circuit 5 and the lock-in amplifier 7. 8 is a calculator, 9 is a television monitor, 10 is an objective lens drive unit 2
The computer 8 is connected to the lock-in amplifier 7, the television monitor 9, and the lens drive circuit 10. Note that the computer 8 receives the output of the lock-in amplifier 7, processes the data, and then outputs a movement amount signal to the lens drive circuit 10. The lens drive circuit 10 scans the objective lens 2d in xy two dimensions via the objective lens drive unit 2e based on the input movement amount signal. 4a is a frame for fixing the optical section 2 and the photoacoustic cell 3.

In such a configuration, the laser beam emitted from the semiconductor laser 2a of the optical section 2 is made into parallel light by the collimator lens 2b, and a part of the light beam is condensed by the objective lens 2d. . The focused light passes through the optical window 3a of the photoacoustic cell 3 and reaches the sample 3 installed in the sealed chamber 3b.
c. Here, in response to the modulation signal from the oscillator 6, the laser light emitted from the semiconductor laser 2a of the optical section 2 is modulated by the semiconductor laser drive circuit 5. This modulated laser light intermittently heats the sample 3c, causing the gas layer on the surface of the sample 3c to expand and contract. Therefore, the pressure inside the sealed chamber 3b increases and photoacoustic waves are generated. This photoacoustic wave is detected by the microphone 3d, and the signal from the microphone 3d is amplified by the lock-in amplifier 7 in synchronization with the modulation frequency and output to the computer 8. The computer 8 stores the output of the lock-in amplifier 7 as a function of the irradiation position (x, y) on the surface of the sample 3c, and
After data processing, it is displayed on the television monitor 9 as a photoacoustic image. The computer 8 outputs a movement amount signal to the lens drive circuit 10 for moving the irradiation position. The lens drive circuit 10 moves the objective lens 2d via the objective lens drive section 2e in accordance with the movement amount signal output from the lock-in amplifier 7. As the objective lens 2d moves, the irradiation position on the surface of the sample 3c moves, as shown by the dotted line in FIG. By repeating this operation, the laser beam from the optical section 2 is scanned in the x and y directions, and a photoacoustic image of the sample 3c is obtained.

[0013]

[Effects of the Invention] As described above in detail together with the embodiments, according to the first embodiment of the present invention, the optical part of the photoacoustic microscope can be easily attached to the objective lens revolver of the optical microscope. , a photoacoustic microscope can be easily incorporated into an optical microscope. In addition, the beam splitter in the optical section of the photoacoustic microscope allows the epi-illumination light of the optical microscope and the laser light of the photoacoustic microscope to be irradiated onto the sample at the same time, making it possible to simultaneously measure the optical microscope image and photoacoustic image of the sample. The measurement area can be easily searched. Furthermore, it is also possible to measure photoacoustic signals at specific minute points.
A photoacoustic microscope with improved operability can be realized. Furthermore, according to the second embodiment of the present invention, scanning of the laser beam is changed from a method in which the sample is moved using an xy stage to a method in which the laser light is moved using a lens drive circuit. As a result, compared to the time required to move the xy stage, the moving part of the objective lens is lighter and no motor is used, so the movement of the objective lens can be made faster, so the scanning time can be shortened and high-speed measurements can be performed. In addition, the method of moving the sample using an xy stage applies vibration to the sample and microphone during scanning, so
The scanning time is the sum of the stage movement time and the vibration settling time, and the sample position is also likely to shift due to vibration, resulting in a lack of reliability.In contrast, the objective lens movement method Since no vibration is applied to the photoacoustic microscope, scanning time is short and reliability is improved.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a first embodiment of a photoacoustic microscope of the present invention.

FIG. 2 is a configuration diagram showing a second embodiment of the photoacoustic microscope of the present invention.

FIG. 3 is a schematic explanatory diagram of xy scanning of the device in FIG. 2;

FIG. 4 is a conventional example of a photoacoustic microscope.

[Explanation of symbols]

1 Optical microscope 1a Objective lens revolver 1b Epi-illumination system 1c TV camera 2 Optical Department 2a Semiconductor laser 2b Collimator lens 2c beam splitter 2d objective lens 2e Objective lens drive unit 3 Photoacoustic cell 3a Optical window 3b Sealed room 3c Sample 3d microphone 4 xy stage 5 Semiconductor laser drive circuit 6 Oscillator 7 Lock-in amplifier 8. Calculator 9 TV monitor 10 Lens drive circuit

Claims (2)

[Claims] Claim 1: An optical microscope comprising an objective lens revolver, an epi-illumination system, and a television camera, for displaying an optical microscope image of a sample surface on a television monitor, a semiconductor laser, a collimator lens, and an objective lens. , an optical section fixed to the objective lens revolver of the optical microscope, a photoacoustic cell equipped with an optical window, a sealed chamber in which a sample is placed, and a microphone for detecting photoacoustic waves, and this photoacoustic cell is fixed, xy2 An xy stage that scans in three dimensions, an oscillator and semiconductor laser drive circuit for modulating the output light of the semiconductor laser of the optical section, and an output signal of the microphone of the photoacoustic cell synchronized to the modulation frequency. The output signal of the lock-in amplifier when the photoacoustic cell is scanned two-dimensionally by the xy stage is input, and after data processing, the photoacoustic signal is displayed on the television monitor. A photoacoustic microscope characterized in that it is configured to include a computer that displays an image. Claim 2: A photoacoustic cell comprising an optical section including a semiconductor laser, a collimator lens, an objective lens, and a driving section thereof, an optical window, a sealed chamber in which a sample is placed, and a microphone for detecting photoacoustic waves. and a lens drive circuit that drives the objective lens of the optical section in xy two dimensions via its drive section;
an oscillator and a semiconductor laser drive circuit for modulating the output light of the semiconductor laser of the optical section; a lock-in amplifier for amplifying the output signal of the microphone of the photoacoustic cell in synchronization with the modulation frequency; a computer that receives an output signal from the lock-in amplifier, displays a photoacoustic image of the sample on a television monitor after processing the data, and inputs data to the lens drive circuit; A photoacoustic microscope characterized in that the objective lens of the optical section is driven in xy two dimensions by a circuit to scan the output light from the semiconductor laser of the optical section that irradiates the photoacoustic cell. .