JP3254465B2 - Photothermal displacement signal detection method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photothermal displacement signal detection method and apparatus capable of detecting information on the surface and the inside of a sample at a high speed with improved spatial resolution.

[0002]

2. Description of the Related Art The photoacoustic effect was created in 1881 by Tyndall, Bell,
Discovered by Rentogen and others. The photoacoustic effect means that, as shown in FIG. 17, light (intermittent light) 19 whose intensity has been modulated in advance is irradiated as excitation light onto the surface of the sample 7 while being condensed via the lens 5. , Heat is periodically generated in the light absorption region (V _op ) 21, and the heat diffusion region (V _th ) 2 given by the heat diffusion length (μ _s ) 22
3 is a phenomenon that elastic waves (ultrasonic waves) are periodically generated by the thermal strain waves. The ultrasound,
By detecting a photoacoustic signal using a microphone (acoustoelectric transducer), a piezoelectric element, or an optical interferometer, and obtaining a signal component synchronized with the modulation frequency of the excitation light, information on the surface of the sample 7 and the inside thereof is obtained. Is obtained. Incidentally, the thermal diffusion length (μ _s ) 22 depends on the excitation light 19.
Is given by the following formula 1 from the thermal conductivity k, the density ρ, and the specific heat c of the sample 7 where f _L is the modulation frequency.

[0003]

(Equation 1)

[0004] Regarding the method of detecting a photoacoustic signal,
For example, the document “Photoacoustic microscope” (Non-destructive inspection; Vol. 36, No. 10, pp. 730-736 (October 1987)
Mon)) and “IEE 1986 Ultrasonics Symposium; pp. 515-526 (19)
1986) (IEEE 1986 ULTRASONICS)
SYMPOSUM; p. 515-526 (198
6) ".

Here, a photoacoustic signal detecting apparatus according to the prior art will be described. FIG. 18 shows an example of the configuration. As shown in the figure, a parallel laser beam from a laser oscillator 1 firstly receives an acousto-optic modulator (AO modulator) 2
The intermittent light is obtained as an intermittent light by the intensity modulation by the laser beam. The intermittent light is converted into a parallel laser beam 19 having a desired beam diameter via the beam expander 3 as the excitation light. In the state where the light is reflected by the lens 5 and further condensed by the lens 5, the light is irradiated onto the surface of the sample 7 placed on the XY stage 6. As a result,
Ultrasonic waves are generated by the thermostrictive wave generated from the condensing section 21 on the sample 7, and at the same time, a minute displacement is generated on the surface of the sample 7. For example, this minute displacement is detected by a Michelson interferometer described below. Is what is being done. As shown, the parallel laser light from the laser oscillator 8 is applied to a beam expander 9.
The laser beam 20 is made into a desired beam diameter enlarged parallel laser beam 20 through the laser beam, then split into two optical paths by a half mirror 10, one of which is condensed as a probe beam 24 via a lens 5, and condensed on a sample 7. One is irradiated to the reference mirror 11 while the other is irradiated to the reference mirror 11. The reflected light from the sample 7 with respect to the probe light 24 and the reference mirror 1
The reflected light from the light source 1 interferes with each other on the half mirror 10, and the interference light is detected by a photoelectric conversion element 13 such as a photodiode in a state where the interference light is condensed via a lens 12, thereby obtaining an interference intensity signal. It is something that can be done. afterwards,
The interference intensity signal is supplied to the lock-in amplifier 16 via the preamplifier 14, and only the intensity modulation frequency component included in the interference intensity signal is used as an intensity modulation frequency signal from the oscillator 15 used for driving the acousto-optic modulator 2. Is to be extracted. This intensity modulation frequency component contains information on the surface or inside of the sample 7 corresponding to the frequency. At this time, by changing the intensity modulation frequency by the computer 17, the heat diffusion length (μ _s ) 21 can be changed accordingly, so that information on the sample 7 at various depths can be obtained. is there. If there is a defect such as a crack in the heat diffusion region (V _th ) 23, the presence of the defect is known because the amplitude of the intensity modulation frequency component in the interference intensity signal and the phase with respect to the modulation frequency signal change. is there.

The irradiation position of the laser beam on the sample 7 is X
The computer 17 controls the update via the Y stage 6 so that it can be updated.
Although known from the position detection signal from the Y stage 6, the sample 7
When the computer 17 processes the intensity-modulated frequency component from the lock-in amplifier 16 in correspondence with the actual laser light irradiation position each time the laser light is irradiated on the sample 7, Can be displayed as two-dimensional image information on a display 18 such as a monitor television.

[0007]

Generally, when two-dimensional internal information of a sample is to be obtained by a photoacoustic detection optical system using an optical interferometer, an excitation light for generating a photoacoustic effect is required. And the probe light for detecting the minute displacement of the sample surface caused by the photoacoustic effect,
The sample must be relatively two-dimensionally scanned on each sample. However, this two-dimensional scanning is a point scanning in which information is detected one point at a time, and it takes much time to scan the entire surface of the sample. Indeed, this inconvenience has been the reason why photoacoustic detection technology cannot be applied to inspection of defects inside a sample in a production line.

In order to detect a photoacoustic signal at high speed, excitation light and probe light are formed as sheet beams (defined as linear spot light), and a solid-state image sensor such as a CCD one-dimensional sensor is used as a detector. It can be used. In this case, it is extremely effective in detecting a photoacoustic signal at high speed as compared with point scanning in which information is detected one by one, but on the other hand, the resolution in the longitudinal direction of the one-dimensional sensor is deteriorated. This makes it difficult to detect the internal information of the sample with high resolution and stably at present.

To explain this situation in more detail, for example, as shown in FIG. 19, as the internal information of the sample 347, the thermal property of the sample 347, that is, the thermal impedance is different between the left and right, and the left portion 332 is It is assumed that the thermal impedance is lower than that of the portion 333. As can be seen from the above, in the case of the point scanning, the irradiation of the excitation light 19 and the movement of the excitation light 19 in the x direction cause the distribution of the thermal impedance existing in the thermal diffusion region 23 at each irradiation position of the excitation light 19. The amplitude and the phase of the distorted wave change, and the change appears as a minute displacement on the surface of the sample 347. A photoacoustic signal is obtained by detecting the minute displacement as an interference intensity signal with the probe light 24 of the interferometer. Therefore, the photoacoustic signal obtained at each irradiation position of the excitation light 19 is obtained by integrating the thermal impedance information in the heat diffusion region 23. A photoacoustic image is constructed on the assumption that the photoacoustic signal at each of the irradiation positions of the excitation light 19 is information in the heat diffusion region 23. The integration effect in the heat diffusion region 23 causes the boundary of the sample 347 to be formed. The photoacoustic signal at the position is also smoothed. FIG. 18 also shows the amplitude distribution 432 of the photoacoustic image in the x direction,
It can be seen that the photoacoustic signal at the thermal impedance boundary position of the sample 347 changes relatively gently and is smoothed due to the integration effect. On the other hand, as shown in FIG. 20, when the excitation light 46 and the probe light 145 have a certain width in the x direction and are configured as a sheet beam converged in the y direction, the excitation light 46 When the sample 347 is irradiated while straddling the left portion 332 and the right portion 333, the light absorption region 105 is straddling the left portion 332 and the right portion 333, and therefore, the heat diffusion region 106 It is clear that the sheet also spreads in the longitudinal direction of the sheet beam. As described above, the excitation light 4
6 irradiation position, that is, any excitation light 46 in the sheet beam
Since the photoacoustic signal at the irradiation point is obtained by integrating the thermal impedance information in the thermal diffusion region 106, the obtained photoacoustic image is obtained as a so-called blurred image in which the resolution is significantly deteriorated in the longitudinal direction of the sensor. It is something that can be done. This phenomenon is also shown in FIG. 19 as the amplitude distribution 433 in the x direction of the detected photoacoustic image, and the amplitude distribution 433 is different from the amplitude distribution 432 shown in FIG. It can be seen that the image is greatly smoothed, and the resolution in the longitudinal direction of the sensor is accordingly deteriorated.

An object of the present invention is to provide a photothermal displacement signal detection method and apparatus capable of detecting information on the surface and the inside of a sample at high speed and in a stable manner with improved spatial resolution.

[0011]

SUMMARY OF THE INVENTION The object of the present invention is basically to provide a light intensity-modulated at a desired intensity modulation frequency by a first light .
A first movement of the sample on the surface of the sample moving in the first direction;
First focusing irradiated as the state of the linear spot light, said first linear spot light surface of the irradiated region or inside the photoacoustic effect, which is linearly formed in a direction perpendicular to the direction or photothermal, and at the same time generating effect, the first
A second linear spot light irradiating linearly spot light irradiation region, and the reference light reflected from the said by the second linear spot light first <br/> linear spot light irradiation area interference
To form an interference light, the interference light is detected by a one-dimensional photoelectric conversion element array sensor at a position conjugate with the sample surface, and the intensity signal of the detected interference light is used to detect the interference light .
When detecting a minute thermal expansion displacement of the same frequency component as the intensity modulation frequency generated in the linear spot light irradiation area of 1 and obtaining a photothermal displacement image based on the minute thermal expansion displacement, On the other hand, by performing image processing in a predetermined manner, the deterioration of the spatial resolution on the image is obtained as a state having the restored two-dimensional spatial resolution . Further, as the apparatus configuration, a first light source, intensity modulation means for intensity-modulating light from the first light source at a desired intensity modulation frequency, and at least a sample mounted thereon
A movable table means in one direction, the direction which perpendicular to the first direction the sample is moved over <br/> surface of the sample to be moved in one direction by the table means the intensity-modulated light
Excitation that generates a photoacoustic effect or a photothermal effect on the surface or inside the first linear spot light irradiation area by condensing and irradiating the first linear spot light in the state of being linearly formed in the first direction . means and, a second light source, on the focused irradiation light from the second light source as the state of the second linear spot light to the first linear spot light irradiation region, wherein said first straight line from Jo spot light irradiation area and the second linear spot light irradiated by the reflected light and the second of
A light interference unit that interferes with reference light generated from light from the light source , and interference as a one-dimensional photoelectric conversion element array sensor that detects the interference light from the light interference unit at a position conjugate with the sample surface. a light detecting means detects a small thermal expansion displacement of the intensity modulation frequency and the same frequency components generated from the interference light intensity signal from the interference light detecting means in said first linear spot light irradiation region said detected Image forming means for forming a photothermal displacement image having a two-dimensional spatial resolution based on the obtained minute thermal expansion displacement, and spatially resolving the image by performing predetermined image processing on the photothermal displacement image from the image forming means. Resolution degradation repairing means for repairing the degradation of the image, and two-dimensional degradation-repaired from the resolution degradation repairing means
Information detecting means for detecting two-dimensional information on the surface and inside of the sample from a photothermal displacement image having a spatial resolution of

[0012]

In essence, in order to detect a photoacoustic signal (photothermal displacement image) at high speed, a sheet beam is used for excitation light and probe light, and a CCD one-dimensional sensor or the like is used for interference light detection. . At this time, the resolution in the longitudinal direction of the one-dimensional sensor is deteriorated, and this resolution deterioration is considered to be restored by image processing. That is,
From the detected interference light intensity signal, a small thermal expansion displacement having the same frequency component as the intensity modulation frequency generated in the linear spot light irradiation area is detected, and a photothermal displacement image is obtained based on the small thermal expansion displacement. At that time, the photothermal displacement image is subjected to predetermined image processing,
The photothermal displacement image is obtained as a state in which the deterioration of the spatial resolution on the image has been restored. Moreover, the photothermal displacement image whose spatial resolution has been deteriorated has its deterioration restored by various restoration methods.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to FIGS. First, the photothermal displacement signal detecting device according to the present invention will be described. FIG. 2 shows an example of the configuration. In this case, the photothermal displacement signal detection device is configured such that the excitation optical system 201, the telodyne-type Twyman-Green interference optical system 202 for photoacoustic signal detection, and the signal processing system 203 are the main components. First, starting from the excitation optical system 201, the Ar laser 31 (wavelength 51
5 nm) is incident on the acousto-optic modulator 33 and is intensity-modulated by a modulation signal from the signal combiner 88. In the signal synthesizer 88, a sine wave signal 98 having a frequency f _C0 from an oscillator 86 shown in FIG. 3A and an oscillator 87 shown in FIG.
A modulation signal 100 shown in FIG. 3C is created as a product of a square wave signal 99 having a frequency f _L (f _L <f _C0 ) from is there. As a result, the first-order diffracted light 35 frequency-shifted by f _C0 is output intermittently at the frequency f _L from the acousto-optic modulation element 33. That is, from the acousto-optic modulation element 33,
As the excitation light, in which the intensity-modulated beam modulation frequency f _L which is frequency shifted by f _C0 is obtained. By the way,
At this time, the 0-order light 34 output together is blocked by the stop 36. The beam diameter of the intensity-modulated beam 35 from the acousto-optic modulator 33 is then expanded as desired by a beam expander 38 via a beam splitter 37, and further converted to an elliptical beam 40 by a cylindrical lens (cylindrical lens) 39. In this state, the light is reflected in the direction of the objective lens 42 by a dichroic prism (reflection at a wavelength of 600 nm or less, transmission at a wavelength of 600 nm or more) 41. The intensity modulated beam 35 is
The pupil 43, that is, the rear focal point 44, is focused in the x direction, and is incident as parallel light in the y direction. In the y direction, since the cylindrical lens 39 can be regarded as a mere plate glass having no curvature, the light is incident on the rear focal position 44 of the objective lens 42 as parallel light. As a result, as shown in FIGS. 4A and 4B, on the front focal position of the objective lens 42, that is, on the surface of the sample 47, the excitation beam is focused in the y direction and having a width in the x direction. Thus, one striped beam 101 is obtained. Incidentally, in the beam splitter 37, a part (about 10%) of the intensity-modulated beam 35 is reflected as a beam light 49 for feedback control, and is detected by a photoelectric conversion element 50 such as a photodiode. The signal is sent to the oscillator 87 via the oscillator 87. In the oscillator 87, the set frequency fL from the modulation signal control circuit 90 and the photoelectric conversion element 502
Is compared with the detected measurement frequency fL ', and the oscillation frequency is finely adjusted so that the two coincide with each other. Specifically, the oscillator 87 has a so-called PL
It is configured with an L (Phase Locked Loop) circuit and the like.

FIG. 4 shows the excitation optical system 201.
More specifically, the focal position of the cylindrical lens 39 coincides with the rear focal position 44 of the objective lens 42, and the front focal position of the objective lens 42 is Coincide with the surface. Therefore, as shown in FIG. 4A, in the x direction, the beam 40 from the cylindrical lens 39 is
The beam 46 from the objective lens 42 is incident on the surface of the sample 47 in a state of being made into parallel light in order to condense the light to the rear focal position 44. On the other hand, as shown in FIG. 4B, in the y direction, the cylindrical lens 3
9 can be regarded as a plate glass having no curvature, so that the beam 40 from the cylindrical lens 39 is incident on the objective lens 42 in a parallel light state, so that the beam 46 from the objective lens 42 is collected on the surface of the sample 47. It is incident in a light state. As a result, as shown in FIG. 5, one stripe beam 101 having a width in the x direction and being focused in the y direction is irradiated as an excitation beam on the surface of the sample 47. Now, as shown in FIG. 5, consider a sample 47 in which the thermal properties at the center are different from those at the periphery. The sample 47 is formed by applying Ar ions to the central portion 103 on a silicon wafer at an acceleration energy of 300 keV and a current density of 10 mA / c.
The pattern was formed by implanting 10 ¹⁵ / cm ² under the condition of m ² . FIG. 6 is a cross-sectional view showing the internal structure of the sample 47 and the thermal diffusion region generated by the excitation beam. Here, an important point is a difference in thermal properties between the central portion 103 as the Ar ion implanted region and the other non-implanted region 102. For example, assuming that the intensity modulation frequency f _L of the excitation light is 88.235 kHz,
In Equation 1 described above, the thermophysical constant of silicon, that is, the thermal conductivity of silicon Si, k = 168 (J · m ⁻¹ · K ⁻¹ · s ⁻¹ ),
Density ρ = 2.34 (× 10 g ⁶ · m ⁻³ ), specific heat c = 0.7
If 61 (J · g ⁻¹ · K ⁻¹ ) is substituted together with the intensity modulation frequency f _L , the thermal diffusion length (μs) in the non-implanted region 102 is about 18 μm, but in the Ar ion implanted region, non-implanted Since the thermal conductivity is approximately two to three orders of magnitude lower than in the region 102, the thermal diffusion length is significantly reduced. As a result, as shown in FIG. 6, in the stripe-shaped light absorption region 105 formed by the stripe-shaped excitation beam 101, the applied heat is largely diffused in the non-implanted region 102, but the Ar ion implantation is performed. The heat diffusion region 106 is formed in such a state that the heat diffusion region 106 is diffused small in the region. As a result, as shown in FIG. 5 and FIG.
If the irradiation is performed so as to include the r ion implantation region, ultrasonic waves (thermoelastic waves) are generated along the light absorption region 105 due to the photoacoustic effect or the thermostrictive wave generated based on the photothermal effect, and the ultrasonic wave is generated on the surface of the sample 47. Indicates that a minute displacement distribution (indicated by a broken line) 110 reflecting the internal information is generated. That is, the stripe-shaped excitation beam 101 is
By irradiating the surface, it is possible to detect the two-dimensional internal information of the sample at high speed.

Next, the heterodyne type Twyman-Green interference optical system 202 for detecting the minute displacement distribution 110 on the surface of the sample 47 based on the photoacoustic effect will be described. As shown in FIG. Wavelength 63
The linearly polarized light beam 52 emitted from the (3 nm) 51 has a polarization direction set to a polarization direction 111 of 45 ° with respect to the x-axis and the y-axis as shown in FIG. (The direction perpendicular to the plane of FIG. 2 is the y-axis,
The direction orthogonal to this is the x-axis). The linearly polarized light beam 52 is incident on the polarization beam splitter 53. In the polarization beam splitter 53, of the linearly polarized light beam 52, the p-polarized light component 54 shown as 112 in FIG. 6 as it is and transmitted to the acousto-optic modulation element 62, while FIG.
The s-polarized light component 55 shown as 113 in (a) is reflected in the mirror 56 direction. Now, from the oscillator 91, a sine wave having a frequency f _C1 similar to that shown in FIG.
When the zero-order light 63 is blocked by the stop 65, the p-polarized first-order diffracted light 64 frequency-shifted by f _C1 is obtained. The p-polarized first-order diffracted light 64 is reflected by the mirror 66 and then passes through the polarization beam splitter 61 as it is. On the other hand, the s-polarized light component 55 reflected by the polarization beam splitter 53 is reflected by a mirror 56 and then incident on an acousto-optic modulation element 57, and is output from an oscillator 91 in the same manner as that shown in FIG. , Frequency f _C2 (f _C1 ≠
f _C2 ) is modulated as a modulation signal. Thus, the acousto-optic modulation element 57 outputs 0
In a state where the next light 58 is shielded by the stop 60, the s-polarized first-order diffracted light 59 frequency-shifted by f _C2 is obtained.
By being reflected by the polarization beam splitter 61, it is combined with the p-polarized first-order diffracted light 64 that has passed through the polarization beam splitter 61. This combined light 67 is a two-frequency orthogonally polarized light, that is, as shown in FIG.
As shown as 113, mutually orthogonal and f
It is not made up of two light beams having a frequency difference between _C1 -f _C2. After passing through the beam splitter 68, the combined light 67 is expanded to a desired beam diameter by a beam expander 70, and further converted to an elliptical beam by a cylindrical lens (cylindrical lens) 71. p-polarized beam 72 and s
It is separated into a polarized beam 74. Of these, the p-polarized beam 72 is frequency-shifted by f _C1 , passes through the dichroic prism 41, and is then focused on the pupil 43 of the objective lens 42, that is, the rear focal position 44 in the x direction. In the y direction, the light is incident as parallel light. For the y direction,
Since the cylindrical lens 71 can be regarded as a mere plate glass having no curvature, the rear focal position 4 of the objective lens 42 can be considered.
No. 4 is incident as parallel light. The beam emitted from the objective lens 42, after passing through the λ / 4 plate 45, is converted into a circularly polarized light beam 145 as a probe beam 145, as shown in FIG. Excitation beam 101 on 47 surfaces
And the same position. On the surface of the sample 47, the probe beam 145 has a width in the x direction and y
It is obtained as one striped beam 190 focused in the direction. As shown in FIG. 6, the reflected light from the sample 47 has a small displacement distribution 110 generated on the surface of the sample 47 by the photoacoustic effect as phase distribution information, and the reflected light from the sample 47 is λ / 4. After passing through the plate 45, the s-polarized beam is passed through the objective lens 42, again through the same optical path, and
The light is reflected in the direction of the CD one-dimensional sensor 82.

On the other hand, the s-polarized beam 74 separated by the polarizing beam splitter 73 is frequency-shifted by f _C2 , and after passing through the λ / 4 plate 75, is reflected by the reference mirror 76 in a state of being circularly polarized. It has become something. The reflected circularly polarized beam from the reference mirror 76 is again applied to the λ / 4 plate 7.
5 and p-polarized light is passed through the polarizing beam splitter 73 as reference light. FIG. 8 shows the polarization direction 114 of the reflected light from the sample 47 reflected by the polarization beam splitter 73 together with the polarization direction 115 of the reflected light from the reference mirror 76, but both are orthogonal to each other. It is clear that the two do not interfere with each other in this state of polarization. Therefore, a polarizing plate 79 is inserted after the imaging lens 78, and its polarization direction is changed to the 45 ° polarization direction 1 shown in FIG.
By setting it to 16, as an interference result of both reflected lights,
heterodyne interference light 80 having a beat frequency f _B = f _C1 -f _C2 are those obtained. The heterodyne interference light 80 includes, as optical phase distribution information, a one-dimensional distribution in the x direction of a minute displacement generated on the surface of the sample 47 due to the photoacoustic effect.
After the stray light is removed by an interference filter 81 of 33 nm, an image is formed on an accumulation type solid-state image sensor 82 such as a CCD one-dimensional sensor by an imaging lens 78.
Since the imaging surface of the storage-type solid-state imaging device 82 and the surface of the sample 47 are in an image-forming relationship, it is natural that the imaging surface thereof has the same shape as the probe beam formed on the surface of the sample 47.
The stripe-shaped interference light is imaged. In addition,
In the beam splitter 68, the combined light 6 of the two-frequency orthogonal polarization
7 (about 10%) is reflected, and the polarization direction of both polarization components of the reflected beam light is as shown in FIG.
As shown by reference numeral 6, interference light 84 is generated by interfering with each other by a polarizing plate 83 oriented at 45 °, and the interference light 84 is detected by a photoelectric conversion element 85 such as a photodiode. . The interference light 84 is detected by the photoelectric conversion element 85 as a beat signal of f _B ′ = f _C1 ′ −f _C2 ′, and is sent to the CCD one-dimensional sensor drive control circuit 93 via the amplifier circuit 92 for feedback control. Is what it is. The drive control circuit 93, and set the beat frequency f _B from the computer 96, and the actually detected measured frequency fB 'in the photoelectric conversion element 85 is compared, as they match, the computer 96, the modulation signal control circuit The frequency f _C1 or the frequency f _{C2 of} a sine wave output from an oscillator (configured from a PLL (Phase Locked Loop) circuit) 91 via a 90 is finely adjusted.

Here, the heterodyne type Twyman-Green interference optical system 202 will be described in more detail.
As shown in FIGS. 4A and 4B, similarly to the excitation optical system 201, the focal position of the cylindrical lens 71 coincides with the rear focal position 44 of the objective lens 42. The front focal position coincides with the surface of the sample 47. Therefore, as shown in FIG. 4A, in the x direction, the p-polarized beam 72 from the cylindrical lens 71 is once collected at the rear focal position 44 of the objective lens 42, Beam 14
Reference numeral 5 denotes a light beam which is irradiated on the surface of the sample 47 in a parallel light state. On the other hand, as shown in FIG. 4B, in the y direction, since the cylindrical lens 71 can be regarded as a mere plate glass having no curvature, the beam 72 from the cylindrical lens 71 is parallel to the objective lens 42. The beam 145 that is incident and exits from the objective lens 42
The light is irradiated on the surface in a condensed state. As a result, as shown in FIG. 5, on the surface of the sample 47, at the same position as the excitation beam 101, similarly to the excitation beam 101, one stripe having a width in the x direction and focused in the y direction The beam 190 is irradiated. On the other hand, as shown in FIGS. 4A and 4B, the focal position of the cylindrical lens 71 and the position of the reference mirror 76 match. Therefore, as shown in FIG. 4A, in the x direction, the s-polarized beam 74 emitted from the cylindrical lens 71 is condensed on the reference mirror 76, and as shown in FIG. Is incident in a parallel light state.

FIGS. 9A and 9B show the detection of interference light by the heterodyne interference optical system in the x and y directions.
As shown in the figure, the front focal position of the objective lens 42 is
7, the rear focal position 44 of the objective lens 42 coincides with the front focal position of the imaging lens 78, and the rear focal position of the imaging lens 78 is It matches the imaging plane. That is, this optical system is a double telecentric imaging optical system. Therefore, as shown in FIG.
After passing through the objective lens 42, the parallel reflected light from the surface of the sample 47 is once focused at the rear focal position 44, and
After eight passes, the light becomes parallel light again and is incident on the CCD one-dimensional sensor 82. On the other hand, as shown in FIG. 9B, in the y direction, the divergent reflected light from the surface of the sample 47 becomes parallel light after passing through the objective lens 42, and after passing through the imaging lens 78, the rear focal position, that is, The light is focused on the CCD one-dimensional sensor 82. As a result, a single stripe beam having a width in the x direction and focused in the y direction is obtained on the CCD one-dimensional sensor 82 in the same manner as the probe beam 190 on the sample 47. Also, as shown in FIGS. 9A and 9B, the position of the reference mirror 76 and the front focal position of the imaging lens 78 match. Therefore, as shown in FIG.
In the x direction, the divergent reflected light from the reference mirror 76 becomes parallel light after passing through the imaging lens 78, enters the CCD one-dimensional sensor 82, and as shown in FIG.
In the y direction, the light is focused on the rear focal point, that is, on the CCD one-dimensional sensor 82 after passing through the imaging lens 78. Therefore, the heterodyne interference light obtained by the reflected light from the sample 47 and the reference light from the reference mirror 76 becomes the same stripe beam as the probe beam light 72 on the CCD one-dimensional sensor 82, and the one-dimensional optical interference signal in the x direction Are detected.

Here, from the output signal from the CCD one-dimensional sensor 82, the amplitude and phase of the minute displacement on the surface of the sample 47 generated based on the photoacoustic effect can be determined by the influence of the reflectance distribution and the unevenness distribution on the surface of the sample 47. The method of extraction without receiving is described as follows. Now, the wavelength of the probe beam light 72 incident on the surface of the sample 47 is λ, its amplitude is 1, the reflection coefficient on the surface of the sample 47 is a _s ,
The reflection coefficient in the reference optical path is a _r , the optical phase difference between the optical path of the probe light including the phase change due to the unevenness on the surface of the sample 47 and the reference optical path is φ, and the minute displacement on the surface of the sample 47 due to the photoacoustic effect. Assuming that A is the phase change amount with respect to the intensity modulation signal and θ is the heterodyne interference light I that is incident on one pixel on the CCD one-dimensional sensor 82, is represented by Expression 2.

[0020]

(Equation 2)

Further, if λ is considerably larger than A, Equation 2 is approximately changed to Equation 3.

[0022]

(Equation 3)

[0023] Here, a term representing the complex amplitude of the micro displacement at _{A · cos (2πf L t +} θ) is the sample 47 surface generated based on the photoacoustic effect. Further, the detection signal I _D (n +
i) ((n + i) is the number of times of accumulation / output of the CCD one-dimensional sensor 82) is expressed by the following equation (4), where α / f _B is the accumulation time of the sensor.
Given by

[0024]

(Equation 4)

Here, with respect to Equation 4, the following items (1) to (5), ie, (1) second term ≠ 0, (2) second
Phase shift amount with respect to the number of accumulation / output times i in the term = π
/ 2, or π / 4, (3) the third term ≠ 0, (4) the phase shift amount with respect to the accumulation / output number i in the third term = π /
2. If a condition that satisfies each item of (5) fourth term = 0 is obtained, the condition is obtained as Expressions 5 and 6, where p and s are integers and α is a non-integer.

[0026]

(Equation 5)

[0027]

(Equation 6)

For example, if s = 6 and p = 2, α = 21
/ 8, f _L = 50 kHz, f _B = 210 kHz, and from Equations 5 and 6, Equation 4 is rewritten as Equation 7.

[0029]

(Equation 7)

Note that the above parameter α = 21/8, f
_L = 50 kHz and f _B = 210 kHz are all set by the computer 96 and sent to the modulation signal control circuit 90 and the CCD one-dimensional sensor drive control circuit 93, and based on the values of the parameters, drive the CCD one-dimensional sensor and the oscillator 87, Driving in each of 91 is controlled. The sensor accumulation time α / f _B is set by the CCD one-dimensional sensor drive control circuit 93 based on the set beat frequency f _B from the computer 96 and the above-mentioned parameter α and the read shift for the CCD one-dimensional sensor at the frequency f _B / α. This is realized by generating a pulse and driving the CCD one-dimensional sensor 82 by this.

In Equation 7, the first term is a DC component, the second term is a phase shift amount of π / 4 with respect to the number of accumulation / output times i, and the optical path of the probe light including the phase change due to the unevenness on the surface of the sample 47. The third term is a modulation component relating to the optical phase difference φ between the probe light path and the reference light path. The third term is that the phase shift amount with respect to the number of accumulation / output times i is π / 2, and the optical path of the probe light including the phase change due to the unevenness of the surface of the sample 47. It is a modulation component related to the optical phase difference φ with the reference optical path, the amplitude A and the phase θ of the photoacoustic signal. Here, regarding Equation 7, i = 1 to i = 8
, That is, if signals for one cycle for the second term and two cycles for the third term are obtained, equations 8 to 15 are obtained.

[0032]

(Equation 8)

[0033]

(Equation 9)

[0034]

(Equation 10)

[0035]

[Equation 11]

[0036]

(Equation 12)

[0037]

(Equation 13)

[0038]

[Equation 14]

[0039]

(Equation 15)

Actually, the detection signal I _D (n + i) from the CCD one-dimensional sensor 82 is amplified by the amplifier circuit 94 and then, as shown in FIG.
Regarding Equation 7, ten sets of data sets from i = 1 to i = 8, that is, a total of 80 accumulated / output data sets are stored in the two-dimensional memory 95. For example, if the number of pixels in the CCD one-dimensional sensor 82 is 256, 256 × 80 data is stored in the two-dimensional memory 95. Here, if the data of the w-th pixel at the time of the (n + i) -th accumulation / output is represented by (n + i, w), the order in which the data is stored in the two-dimensional memory 95 is as follows.

(N + 1,1), (n + 1,2), (n + 1,3)… ……………………… (n + 1,256), (n + 2,1) ), (N + 2,2), (n + 2,3)… ………… ………… ……… (n + 2,256), (n + 3,1), (n + 3,2) , (N + 3,3)…… ……… ……………… (n + 3,256),………………………… (n + 80,1), (n + 80,2 ), (N + 80,3)…… ……… …………… (n + 80,256) On the other hand, when reading out from the two-dimensional memory 95, 80 pixels per pixel are accumulated as follows. The output data sets are sequentially read and sent to the computer 96.

(N + 1,1), (n + 2,1), (n + 3,1)… ……… …………… ……… (n + 80,1), (n + (1,2), (n + 2,2), (n + 3,2)… ………… ………… ……… (n + 80,2), (n + 1,3), ( (n + 2,3), (n + 3,3)…………………………… (n + 80,3),……………………… (n + 1,256) , (N + 2,256), (n + 3,256)…… ………………… (n + 80,256) The computer 96 uses 80 accumulation / output data sets for each pixel, and performs the following calculation processing The reflectance a _s ^{2 of} the surface of the sample 47, the optical phase difference φ between the optical path of the probe light and the reference optical path including the phase change due to the unevenness on the surface of the sample 47,
The amplitude A of the photoacoustic signal whose reflectance on the surface of the sample 47 has been corrected and the phase θ of the photoacoustic signal whose phase change due to unevenness on the surface of the sample 47 has been corrected are obtained. First reflectance a _s ² at the sample 47 surface is by summing up equations 8-15, is given as Equation 16.

[0043]

(Equation 16)

The optical phase difference φ is given by the following formulas 8, 10, 12,
14, which is given as Expression 17.

[0045]

[Equation 17]

Further, the amplitude A of the photoacoustic signal, that is, the sample 4
The small displacement on the surface 7 is obtained by correcting the reflectance on the surface of the sample 47 from Expressions 8, 9, 12, 13, and 16 as shown in Expression 1.
Given as 8.

[0047]

(Equation 18)

Further, the phase θ of the photoacoustic signal, that is, the phase change θ of the excitation light with respect to the intensity-modulated signal is given by the following equations 8, 9,
Based on 12, 13, 16, and 17, the phase change due to the unevenness on the surface of the sample 47 is corrected and given as Expression 19.

[0049]

[Equation 19]

Therefore, the detection signal from the CCD one-dimensional sensor 82 is processed by the computer 96 while the sample 47 is sequentially scanned in the xy directions by the xy stage 48, so that the two-dimensional photoacoustic image (2 (A two-dimensional photothermal displacement image). FIG.
As shown in FIG.
By scanning a in the direction orthogonal to the longitudinal direction of the sheet beam, that is, in the y-axis direction, a photoacoustic image blurred in the horizontal (x) direction as shown in FIGS. (Photothermal displacement image) i _H (x, y) is obtained. Similarly, by scanning in the x-axis direction the excitation light 101b and the probe light 190b, which are rotated by 90 ° relative to the excitation / probe light 101a and 190a, FIGS. 13 (a) and 13 (b) As shown in FIG. 2, a photoacoustic image (photothermal displacement image) i _V (x,
y) is obtained. In this example, two photoacoustic images are obtained by scanning excitation light in each of two orthogonal directions, and these photoacoustic images are used as input data to improve the resolution of the photoacoustic image based on an iterative operation algorithm. It has been done. The principle of blurred image restoration according to the present invention will be described below.

That is, the photoacoustic image (photothermal displacement image) i (x, y) actually detected is given as Expression 20.

[0052]

(Equation 20)

Where o (x, y) is an ideal photoacoustic image b (x, y) is a thermal impulse response of the sample. Thermal impulse response b in photoacoustic effect
(x, y) is a transfer function until the heat injected into the sample by the sheet beam is converted into a small thermal expansion displacement on the surface of the sample, and is known as a point spread function (a function representing blur). It often has a Gaussian distribution or something similar. In this example, the thermoelastic impulse response b (x, y) of the sample is approximated by a Gaussian distribution function. As described above, since the photoacoustic image detected by the optical system is significantly blurred in the longitudinal direction of the sheet beam, a one-dimensional blur function is considered. That is, equations 21 and 22, respectively.
Then, a horizontal blur function b _H (x) and a vertical blur function b _V (y) satisfying the above are obtained by Gaussian distribution.

[0054]

(Equation 21)

[0055]

(Equation 22)

Next, the k-th repetitive output data of the photothermal displacement image to be repaired is set to o _k (x, y), and the data initial value o
₀ (x, y) is selected as in Expression 23 based on the photothermal displacement images i _H (x, y) and i _V (x, y).

[0057]

(Equation 23)

Based on the above input data and Expression 20, the repetitive arithmetic expressions in the horizontal and vertical directions are expressed as Expressions 24 and 25, respectively.

[0059]

(Equation 24)

[0060]

(Equation 25)

Here, α and β are correction coefficients in the horizontal and vertical directions, respectively, and the convergence condition is that α ≦ 1, β ≦ 1. That is, in the second term of Expressions 24 and 25, the photothermal displacement image obtained by performing the convolution operation with the blur function on the ( _k-1 ) -th repeated output image data ok _-1 (x, y), and the actual input The difference from the obtained photothermal displacement image is obtained as an image restoration error, multiplied by a correction coefficient, and integrated with the repetitive output image data of the first term, to obtain the next step repetitive output image data. The resolution is to be restored. In the computer 96, the detected photoacoustic images i _H (x, y) and i _V (x, y) are restored according to the flow shown in FIG. First, the blur function b _H (x) and b _V (y) are obtained by using the standard deviation σ of the Gaussian distribution inputted by the computer 96. Next, the image initial value o ₀ (x, y) of the iterative operation is obtained as an average image of the detected photothermal displacement images i _H (x, y) and i _V (x, y). In each of blocks 260a and 260b,
Alternate image restoration operations in the horizontal and vertical directions
After times repeatedly executed, repaired photothermal displacement image o _k (x,
y) is displayed on the TV monitor 97. The image shown in FIG. 14A is the result of executing the above iterative operation algorithm with k = 5. FIG.
(B) and (c) respectively show AA ′ shown in FIG.
Line, which shows line B-B 'image signal according to o _k (x, y), and it is understood that the deterioration of resolution is restored.

As described above, since the degradation of the resolution of the photothermal displacement image is repaired, it is possible to detect the photothermal displacement image stably and with high resolution, and therefore, the internal information of the sample can be accurately detected. It can be detected. In addition,
In the above example, the horizontal blur correction equation (Equation 24)
And the vertical blur correction equation (Equation 25) is alternately and repeatedly calculated k times.
It is also possible to execute by repeating the repetition operation q times in the vertical direction r times. In the above example, the thermoelastic impulse response is approximated based on the Gaussian distribution function. However, it is also possible to obtain the thermoelastic impulse response by theoretical analysis and execute the above iterative operation algorithm. Further, in the above example, the horizontal and vertical blur functions are obtained as one-dimensional functions. However, it is necessary to derive an iterative operation algorithm based on a two-dimensional blur function having standard deviations different in the xy directions to execute the restoration of a blur image. Is also possible. Furthermore, according to the above example, it is possible to detect a photothermal displacement signal in which the reflectance distribution and the unevenness distribution on the sample surface and the optical path fluctuation are corrected, and the information on the sample surface and inside is made highly sensitive, And it becomes possible to detect stably. Moreover, since the resolution degradation of the photothermal displacement image is repaired only for the photothermal displacement signal detected by the photothermal displacement signal detection device, the existing optical system according to the prior art can be used as it is.

Finally, an example different from the above is shown in FIGS.
6 will be described. Also in this example, the photoacoustic detection optical system shown in FIG. 2 is used, but the difference is the principle of blurred image restoration. The principle of this blurred image restoration will be described below. The photothermal displacement image i (x, y) actually detected is expressed by the following equation (2).
0. In this example, the blur function b (x, y) described in the previous example is approximated by a two-dimensional Gaussian distribution function, and the following equation (26) is obtained by performing a two-dimensional Fourier transform on the equation (20). ing.

[0064]

(Equation 26)

Where I (u, v): Fourier transform image of i (x, y) O (u, v): Fourier transform image of o (x, y) B (u, v): b (x, y) Fourier transform image u, v: spatial frequency in x, y directions.

Therefore, Expression 27 can be obtained by multiplying both sides of Expression 26 by using 1 / B (u, v) as an inverse filter.

[0067]

[Equation 27]

By performing a two-dimensional Fourier transform on Expression 27, an ideal photothermal displacement image o (x, y) is finally obtained.

Based on the above principle, the signal processing system 203
The computer 96 processes the detected photothermal displacement signal i (x, y) in accordance with the flow shown in FIG. In this example, the resolution degradation of the amplitude distribution 433 shown in FIG. 16 is restored. First, a thermal impulse response b (x, y) is approximately obtained by a two-dimensional Gaussian distribution function. Next, b (x,
y), the detected photothermal displacement image i (x, y) is subjected to two-dimensional Fourier transform, and the respective Fourier transform images B (u, v), I
Calculate (u, v). The Fourier transform image O (u, v) of the ideal photothermal displacement image is obtained by the inverse filter 1 / B (u, v), and the two-dimensional inverse Fourier transform is performed. (x, y) is obtained. FIG. 16 shows the effect obtained by applying the inverse filter 1 / B (u, v) to the photothermal displacement image. As can be seen from this, the signal at the boundary on the thermal impedance distribution is sharper than the photothermal displacement signal shown in FIG. In this example, the thermal impulse response is approximated by a Gaussian distribution.
It is also possible to execute the above iterative algorithm.

As described above, an inverse filter is obtained from the thermal impulse response by approximation based on a Gaussian distribution function.
By applying this to the obtained photoacoustic image, the degradation of the resolution of the photothermal displacement image can be repaired, and the photothermal displacement image can be detected stably and with high resolution. It becomes detectable. Moreover, since the resolution degradation of the photothermal displacement image is repaired only for the photothermal displacement signal detected by the photothermal displacement signal detection device, the existing optical system according to the prior art can be used as it is.

[0071]

As described above, claims 1 to 12 are provided.
According to the method, a photothermal displacement signal detection method and device capable of detecting information on the surface and the inside of a sample at high speed and in a stable manner with an improved spatial resolution can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a resolution degradation repair flow by iterative calculation of a photothermal displacement image according to the present invention.

FIG. 2 is a diagram showing a configuration of an example of a photothermal displacement signal detection device according to the present invention.

FIGS. 3A to 3C are diagrams for explaining a method of creating a modulation signal input to an acousto-optic modulator in the excitation optical system.

FIGS. 4A and 4B are diagrams showing a relationship between an excitation optical system and a heterodyne interference optical system in x and y directions.

FIG. 5 is a perspective view showing a planar structure of an example of a sample and a relationship between an excitation beam and a probe beam incident thereon;

FIG. 6 is a diagram showing a cross section of the internal structure of the sample and a thermal diffusion region generated by the excitation beam at that time.

FIGS. 7A and 7B are diagrams for explaining a polarization direction of an incident laser beam and a two-frequency orthogonal polarization state in a heterodyne interference optical system.

FIG. 8 is a diagram for explaining a method of causing reference light and reflected light from a sample to interfere with each other.

FIGS. 9A and 9B are diagrams showing a configuration of a detection unit of a heterodyne interference optical system in x and y directions.

FIG. 10 is a diagram for explaining the order in which pixels are stored in a two-dimensional memory and the order in which pixels are read from the two-dimensional memory in the signal processing system;

FIG. 11 is a diagram for explaining a case where a photothermal displacement image is detected in x and y directions.

FIGS. 12A and 12B are diagrams showing a photothermal displacement image in which the resolution is degraded in the x direction (horizontal direction).

FIGS. 13A and 13B are diagrams showing a photothermal displacement image in which the resolution is deteriorated in the y direction (horizontal direction).

FIGS. 14A to 14C are diagrams showing a blur repair effect according to the present invention on a blur photothermal displacement image.

FIG. 15 is a diagram showing a resolution degradation repair flow of the photothermal displacement image using an inverse filter according to the present invention;

FIG. 16 is a diagram showing a resolution degradation repair effect by the inverse filter;

FIG. 17 is a diagram for generally explaining the principle of the photoacoustic effect;

FIG. 18 is a diagram illustrating a configuration of an example of a photoacoustic signal detection device according to the related art.

FIG. 19 is a diagram illustrating a case where point scanning is performed;
Diagram for explaining how a photoacoustic signal changes at a thermal impedance boundary position

FIG. 20 is a diagram for explaining how a photoacoustic signal changes at a thermal impedance boundary position when sheet beam irradiation is performed;

[Explanation of symbols]

31: Ar laser, 51: He-Ne laser, 33, 5
7, 62: acousto-optic modulator, 39, 71: cylindrical lens, 42: objective lens, 82: CCD one-dimensional sensor, 50, 85: photoelectric conversion element, 96: computer, 47
…sample

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takanori Ninomiya 292, Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture Within Hitachi, Ltd. Production Engineering Laboratory (56) References JP-A-3-282253 (JP, A) JP-A-64-46644 (JP, A) JP-A-57-97416 (JP, A) JP-A-3-156362 (JP, A) JP-A-60-85363 (JP, A) JP-A-3-286750 (JP JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 29/00-29/28

Claims (12)

(57) [Claims] 1. A sample on the surface of the sample to move a desired intensity modulation frequency intensity-modulated light to a first direction movement
Formed linearly in a direction perpendicular to the first direction.
As the state of the first linear spot light irradiating condenser, said first
1 linear spot light irradiation area surface, or internal to the photoacoustic effect, or when to generate photothermal effect simultaneously,
Above first linear spot light irradiation region irradiated with the second linear spot light, on by said second linear spot light
The interference light is formed by interfering the reflected light from the first linear spot light irradiation area with the reference light , and the interference light is detected by the one-dimensional photoelectric conversion element array sensor at a position conjugate with the sample surface. Detecting a small thermal expansion displacement of the same frequency component as the intensity modulation frequency generated in the first linear spot light irradiation region from the detected intensity signal of the interference light ; When a photothermal displacement image is obtained based on the photothermal displacement image, the image processing is performed in a predetermined manner, so that a state having a two-dimensional spatial resolution in which the deterioration of the spatial resolution on the image is restored is restored. A photothermal displacement signal detection method that can be obtained. 2. A first light source, and intensity modulation means for intensity-modulating light from the first light source at a desired intensity modulation frequency;
A table on which a sample can be placed and movable in at least one direction
Means for transmitting said intensity-modulated light to said table means.
Ri second sample is moved over the surface of the sample to be moved in one direction
The first linear spot light irradiation area is condensed and radiated as a first linear spot light state linearly formed in a direction perpendicular to the direction of the first direction, thereby forming a surface or inside of the first linear spot light irradiation area. An excitation means for generating a photoacoustic effect or a photothermal effect, a second light source, and the light from the second light source .
The second linear spot in the first linear spot light irradiation area
After having focused irradiation as the state of the light, generated from light from said second linear spot light reflected light and the second light source by irradiation <br/> of from the first linear spot light irradiation area Interference means for interfering with the reference light, and interference light detection as a one-dimensional photoelectric conversion element array sensor for detecting interference light from the light interference means at a position conjugate with the sample surface Means for detecting a small thermal expansion displacement having the same frequency component as the intensity modulation frequency generated in the first linear spot light irradiation area from the interference light intensity signal from the interference light detection means.
Two-dimensional spatial content based on small thermal expansion displacement and the detected Te
Image forming means for forming a photothermal displacement image having resolution ,
Resolution degradation repairing means for repairing the spatial resolution degradation on the image by subjecting the photothermal displacement image from the image construction means to predetermined image processing; and a two-dimensional repaired degradation repairing means from the resolution degradation repairing means . An information detecting means for detecting two-dimensional information on the surface and inside of the sample from a photothermal displacement image having a spatial resolution ; 3. A sample on the surface of the sample to move a desired intensity modulation frequency intensity-modulated light to a first direction movement
Formed linearly in a direction perpendicular to the first direction.
As the state of the first linear spot light irradiating condenser, said first
1 linear spot light irradiation area surface, or internal to the photoacoustic effect, or when to generate photothermal effect simultaneously,
Above first linear spot light irradiation region irradiated with the second linear spot light, on by said second linear spot light
The reflected light from the first linear spot light irradiation region and the reference light interfere with each other to form interference light , and the interference light is accumulated at a position conjugate with the sample surface. Detecting a minute thermal expansion displacement having the same frequency component as the intensity modulation frequency generated in the first linear spot light irradiation area from the detected intensity signal of the interference light detected by the array sensor; and, when the photothermal displacement image based on small thermal expansion displacement and the detected is obtained by image processing for photothermal displacement image is subjected to a predetermined deterioration of the spatial resolution in the image is repaired 2D spatial resolution
A photothermal displacement signal detection method that is obtained as a state having : 4. A first light source, and intensity modulation means for intensity-modulating light from the first light source at a desired intensity modulation frequency;
A table on which a sample can be placed and movable in at least one direction
Means for transmitting said intensity-modulated light to said table means.
Ri second sample is moved over the surface of the sample to be moved in one direction
The first linear spot light irradiation area is condensed and radiated as a first linear spot light state linearly formed in a direction perpendicular to the direction of the first direction, thereby forming a surface or inside of the first linear spot light irradiation area. An excitation means for generating a photoacoustic effect or a photothermal effect, a second light source, and the light from the second light source .
The second linear spot in the first linear spot light irradiation area
After having focused irradiation as the state of the light, generated from light from said second linear spot light reflected light and the second light source by irradiation <br/> of from the first linear spot light irradiation area A light interfering means for interfering with the reference light, and an interference as a storage type one-dimensional photoelectric conversion element array sensor for detecting the interference light from the light interfering means at a position conjugate with the sample surface. a light detecting means detects a small thermal expansion displacement of the intensity modulation frequency and the same frequency components generated from the interference light intensity signal from the interference light detecting means in said first linear spot light irradiation region said detected 2D based on the small thermal expansion displacement
Image constructing means for constructing a photothermal displacement image having a spatial resolution , and resolution degradation repairing means for repairing degradation of the spatial resolution on the image by performing predetermined image processing on the photothermal displacement image from the image constructing means And a two-dimensional spatial resolution whose deterioration has been repaired by the resolution deterioration repairing means.
2 than photothermal displacement images for the surface and inside of the sample that
A photothermal displacement signal detection device, comprising: information detection means for detecting dimensional information. 5. An initial rotation state, and 90 degrees from the initial rotation state.
Each time the sample is set in each rotated state, the light intensity-modulated at the desired intensity modulation frequency is moved in the first direction
With respect to a first direction in which the sample moves on the surface of the sample
First linear spot formed linearly in a direction perpendicular to
Irradiating light collecting a state of the light, the first linear spot light irradiation area surface, or internal to the photoacoustic effect, or when to generate photothermal effect simultaneously, the above first linear spot light irradiation area Irradiate the linear spot light of No. 2
The reflected light from the first linear spot light irradiation area by the second linear spot light is made to interfere with the reference light so that the interference light
Is formed, and the interference light is detected by a one-dimensional photoelectric conversion element array sensor at a position conjugate with the sample surface,
A minute thermal expansion displacement having the same frequency component as the intensity modulation frequency generated in the first linear spot light irradiation region is detected from the detected intensity signal of the interference light, and a photothermal displacement based on the minute thermal expansion displacement is detected. When an image is obtained, image processing is performed on the photothermal displacement image corresponding to each of the initial rotation state and the state rotated by 90 degrees from the initial rotation state, so that a space on the image is obtained. A method for detecting a photothermal displacement signal, wherein a degradation in resolution is obtained as a state having a two-dimensional spatial resolution in which the resolution has been restored. 6. An initial rotation state, and 90 degrees from the initial rotation state.
Means for setting a sample in each of the rotated states, a first light source, intensity modulation means for intensity-modulating light from the first light source at a desired intensity modulation frequency, and
A table means movable in one direction, and a surface perpendicular to the first direction in which the sample moves on the surface of the sample in which the intensity-modulated light is moved in one direction by the table means.
First linear spotlight Jo <br/> the first by irradiating light collecting a state linear spot light irradiation area surface of or inside the photoacoustic effect, which is formed linearly in a direction or, Exciting means for generating a photothermal effect, a second light source, and condensing and irradiating light from the second light source onto the first linear spot light irradiation area as a second linear spot light state , said first of said second linear spot light the reflected light due to the irradiation of the linear spot light irradiation area
Light interference means for interfering with reference light generated from light from the second light source, and a one-dimensional photoelectric conversion element array sensor for detecting interference light from the light interference means at a position conjugated with the sample surface Detecting the minute thermal expansion displacement of the same frequency component as the intensity modulation frequency generated in the first linear spot light irradiation area from the interference light intensity signal from the interference light detection means. Based on the detected small thermal expansion displacement, a photothermal displacement image having a two-dimensional spatial resolution is obtained from the initial rotational state and the initial rotational state by 90%.
Image forming means configured corresponding to the state where the sample is set in each state rotated by degrees, and by performing a predetermined image processing on the photothermal displacement image corresponding to the two rotation states from the image forming means, Resolution degradation repairing means for repairing the spatial resolution degradation on the image, and two-dimensional information on the surface and inside of the sample from a photothermal displacement image having a two-dimensional spatial resolution that has been repaired from the resolution degradation repairing means. A photothermal displacement signal detection device comprising: 7. An initial rotation state, and 90 degrees from the initial rotation state.
Each time the sample is set in each rotated state, the light intensity-modulated at the desired intensity modulation frequency is moved in the first direction
With respect to a first direction in which the sample moves on the surface of the sample
First linear spot formed linearly at right angles
Irradiating light collecting a state of the light, the first linear spot light irradiation area surface, or internal to the photoacoustic effect, or when to generate photothermal effect simultaneously, the above first linear spot light irradiation area Irradiate the linear spot light of No. 2
The reflected light from the first linear spot light irradiation area by the second linear spot light is caused to interfere with the reference light so as to cause interference light.
Is formed, and the interference light is detected by a one-dimensional photoelectric conversion element array sensor at a position conjugate with the sample surface,
From the detected intensity signal of the interference light , a minute thermal expansion displacement having the same frequency component as the intensity modulation frequency generated in the first linear spot light irradiation area is detected, and a photothermal displacement based on the minute thermal expansion displacement is detected. When a displacement image is obtained, the initial rotation state, the average value image of the photothermal displacement images corresponding to each of the states rotated 90 degrees from the initial rotation state as the initial image, so that the image restoration error is minimized. A photothermal displacement signal obtained by performing an iterative operation alternately in the horizontal direction and the vertical direction of the initial image to obtain a state having a two-dimensional spatial resolution in which deterioration of the spatial resolution on the image has been restored. Detection method. 8. An initial rotation state, and 90 degrees from the initial rotation state.
Means for setting a sample in each of the rotated states, a first light source, intensity modulation means for intensity-modulating light from the first light source at a desired intensity modulation frequency, and
A table means movable in one direction, and a surface perpendicular to the first direction in which the sample moves on the surface of the sample in which the intensity-modulated light is moved in one direction by the table means.
First linear spotlight Jo <br/> the first by irradiating light collecting a state linear spot light irradiation area surface of or inside the photoacoustic effect, which is formed linearly in a direction or, Exciting means for generating a photothermal effect, a second light source, and condensing and irradiating light from the second light source onto the first linear spot light irradiation area as a second linear spot light state , said first of said second linear spot light the reflected light due to the irradiation of the linear spot light irradiation area
Light interference means for interfering with reference light generated from light from the second light source, and a one-dimensional photoelectric conversion element array sensor for detecting interference light from the light interference means at a position conjugated with the sample surface Detecting the minute thermal expansion displacement of the same frequency component as the intensity modulation frequency generated in the first linear spot light irradiation area from the interference light intensity signal from the interference light detection means. Based on the detected small thermal expansion displacement, a photothermal displacement image having a two-dimensional spatial resolution is obtained from the initial rotational state and the initial rotational state by 90%.
Image restoration means configured to correspond to the state in which the sample is set in each of the rotated states, and an average value image of the photothermal displacement images corresponding to the two rotation states from the image formation means as an initial image, image restoration. Resolution degradation repairing means for repairing spatial resolution degradation on an image by performing iterative operations alternately in the horizontal and vertical directions of the initial image so as to minimize errors; An information detecting means for detecting two-dimensional information on the surface and inside of the sample from a photothermal displacement image having a two-dimensional spatial resolution whose deterioration has been repaired from the means. 9. sample on the surface of the sample to move a desired intensity modulation frequency intensity-modulated light to a first direction movement
Formed linearly in a direction perpendicular to the first direction.
As the state of the first linear spot light irradiating condenser, said first
1 linear spot light irradiation area surface, or internal to the photoacoustic effect, or when to generate photothermal effect simultaneously,
Above first linear spot light irradiation region irradiated with the second linear spot light, on by said second linear spot light
The interference light is formed by interfering the reflected light from the first linear spot light irradiation area with the reference light , and the interference light is detected by the one-dimensional photoelectric conversion element array sensor at a position conjugate with the sample surface. Detecting a minute thermal expansion displacement of the same frequency component as the intensity modulation frequency generated in the first linear spot light irradiation area from the detected intensity signal of the interference light, When a photothermal displacement image is obtained based on the above, an inverse filter is obtained based on the thermoelastic impulse response of the sample, and by acting on the photothermal displacement image, deterioration of the spatial resolution on the image is repaired. And a photothermal displacement signal detection method which can be obtained as a state having two-dimensional spatial resolution . 10. A first light source, intensity modulation means for intensity-modulating light from the first light source at a desired intensity modulation frequency, and a table on which a sample is placed and which can move in at least one direction.
And Bull unit, the intensity-modulated above table means the light
Moves the sample on the surface of the sample moving in one direction .
Formed in a straight line in a direction perpendicular to the first direction.
First linear spot light irradiation area surface by focused irradiation as the state of the first linear spot light or internal to the photoacoustic effect, or an excitation means for generating the photothermal effect, a second light source , after having focused irradiation light from the second light source as the state of the second linear spot light to the first linear spot light irradiation region, above the said first linear spot light irradiation area Of the second linear spot light
Created from the light from the reflected light and the second light source by irradiation
Light interference means for causing interference with the reference light, interference light detection means as a one-dimensional photoelectric conversion element array sensor for detecting interference light from the light interference means at a position conjugate with the sample surface, to detect and small thermal expansion displacement the detected minute thermal expansion displacement of the intensity modulation frequency and the same frequency component from the interference light intensity signal generated by the first linear spot light irradiation area from the interference light detecting means Based on the two-dimensional sky
Image forming means for forming a photothermal displacement image having an inter-resolution , and obtaining an inverse filter based on the thermoelastic impulse response of the sample with respect to the photothermal displacement image from the image forming means, thereby allowing the image to act. Resolution degradation repairing means for repairing the spatial resolution degradation on the above, and two-dimensional spatial decomposition having been repaired from the resolution degradation repairing means.
An information detecting means for detecting two-dimensional information on the surface and inside of the sample from a photothermal displacement image having a function . 11. A light source, the light of which intensity is modulated at a desired intensity modulation frequency is transferred onto a surface of the sample moving in a first direction.
Linearly in a direction perpendicular to the first direction of movement.
The first linear spot light is focused and irradiated.
At the same time as generating a photoacoustic effect or a photothermal effect on the surface or inside the first linear spot light irradiation area, irradiating the first linear spot light irradiation area with a second linear spot light, the reflected light from the first linear spot light irradiation area by the second linear spot light to interfere with <br/> reference light interference light formed by, for the sample surface and the conjugate the interference light A one-dimensional photoelectric conversion element array sensor is used to detect the intensity of the detected interference light at a relevant position, and a minute frequency component having the same frequency component as the intensity modulation frequency generated in the first linear spot light irradiation area from the detected interference light intensity signal. When a thermal expansion displacement is detected and a photothermal displacement image is obtained based on the small thermal expansion displacement, the thermoelastic impulse response of the sample is approximated as a Gaussian distribution, and the approximated thermoelastic impulse response is obtained. Based in after having determined the inverse filter, perforated by exerting a light-to-heat-shifted image, the two-dimensional spatial resolution degradation has been repaired the spatial resolution in the image
A photothermal displacement signal detection method is provided which is obtained as a state in which the thermal displacement signal is obtained. 12. A first light source, intensity modulation means for intensity-modulating light from the first light source at a desired intensity modulation frequency, and a table on which a sample is placed and which can move in at least one direction.
And Bull unit, the intensity-modulated above table means the light
Moves the sample on the surface of the sample moving in one direction .
Formed in a straight line in a direction perpendicular to the first direction .
And excitation means for generating the first linear spot light surface of the irradiated region or inside the photoacoustic effect or photothermal effect by focused irradiation as the state of the first linear spot light, a second light source , after having focused irradiation light from the second light source as the state of the second linear spot light to the first linear spot light irradiation region, above the said first linear spot light irradiation area Of the second linear spot light
Created from the light from the reflected light and the second light source by irradiation
Light interference means for causing interference with the reference light, interference light detection means as a one-dimensional photoelectric conversion element array sensor for detecting interference light from the light interference means at a position conjugate with the sample surface, to detect and small thermal expansion displacement the detected minute thermal expansion displacement of the intensity modulation frequency and the same frequency component from the interference light intensity signal generated by the first linear spot light irradiation area from the interference light detecting means Based on the two-dimensional sky
Image forming means for forming a photothermal displacement image having an inter-resolution, and for the photothermal displacement image from the image forming means, an inverse filter is obtained based on a thermoelastic impulse response approximated as a Gaussian distribution. A resolution degradation repairing means for repairing the spatial resolution degradation on the image by acting on the displacement image, and a photothermal displacement image having a two-dimensional spatial resolution from the resolution degradation repairing means having been repaired from the resolution degradation repairing means; And an information detecting means for detecting two-dimensional information about the inside.