JPH0720382A - Laser scanning microscope - Google Patents

Abstract

PURPOSE:To provide a laser scanning microscope by which a very small amount of phase change is observed with high contrast and image processing is performed at high speed. CONSTITUTION:This laser scanning type microscope is provided with a laser light beam source, an optical system for converging a light beam from the laser light beam source in a spot state on the surface of a sample, a scanning means for scanning the surface of the sample with a laser spot, and an image forming processing means for forming an image according to an electric signal being luminance information on the surface of the sample obtained from the laser spot and positional information. Then, the microscope is provided with a subtraction processing means 13 subtracting the amount equal to DC offset potential set in advance from the electric signal including the luminance information before image forming processing, and an amplification means 15 amplifying the electric signal with an amplification factor set in advance after subtracting the amount equal to the DC offset potential therefrom.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser scanning microscope.

[0002]

2. Description of the Related Art A laser scanning microscope for observing a phase object has a high resolution and a signal processing is easy because a two-dimensional image can be obtained by processing an electric signal. Are known to have the advantages of

FIG. 2 is a schematic diagram showing a system configuration of a reflection laser scanning differential interference microscope as an example of the laser scanning microscope.

In FIG. 2, light emitted from a laser light source 1 passes through a polarizer-2 and a beam splitter (BS) 3 as an optical path splitting means, and a birefringent prism 4 (here, a Nomarski). Reach the prism). The birefringent prism 4 forms polarized light in two directions. The two polarized lights are condensed by the objective lens 5 as an illumination spot on the sample surface 6 having a phase change. The sample surface is two-dimensionally scanned by this spot, and a modulated light amount signal is obtained from each point.

That is, 2 modulated by the sample surface 6
The polarized light returns to the birefringent prism 4 as reflected light, is guided to the analyzer 7 by the BS 3, and the 2-polarized interference light is detected by the detector 8.

The modulated light amount signal thus obtained from each point is converted into an electric signal, and a two-dimensional image of the sample is reproduced by synchronizing it with a scanning signal containing position information.
Through the above steps, the phase change (step) of the sample can be visualized by using the laser scanning microscope.

[0007]

However, the modulated light amount signal naturally obtained becomes small with respect to an extremely small phase change, and it becomes difficult to observe the phase change on the sample. Therefore, conventionally, the obtained two-dimensional image is subjected to appropriate image processing to make the image easy to see. However, in the method by this image processing, the image is temporarily stored in a memory such as a buffer, and the image is taken out and duplicated. Therefore, if the image duplication is repeated many times, noise and the like are mixed in proportion to the number of duplications, and the processing time is long.

The present invention has been made to solve the above problems, and an object thereof is to provide a laser scanning microscope capable of observing a minute amount of phase change with high contrast and performing image processing at high speed. To do.

[0009]

The laser scanning microscope of the present invention comprises a laser light source, an optical system for narrowing the light from the laser light source into a spot on the sample surface, and the laser. A laser scanning means for scanning the surface of the sample by the laser spot; and an image forming processing means for forming an image by the electric signal of the brightness information and the position information on the sample surface obtained from the laser spot. -In the scanning microscope,
Subtraction processing means for subtracting a predetermined DC offset potential component from the electric signal containing the luminance information before the image forming process, and predetermined amplification of the electric signal after the subtraction of the DC offset potential component. It is characterized by comprising an amplification means for amplifying at a rate.

[0010]

According to the present invention, in a laser scanning microscope, a change emphasizing process is performed by amplifying an electric signal containing luminance information before an image forming process.

That is, by performing the change emphasizing process by amplifying the electric signal including the luminance information and then performing the image forming process, noises and the like are generated as compared with the conventional case where the image is once formed and then the image process is performed. The mixing can be suppressed as much as possible, the processing time can be shortened, and high-speed processing can be performed.

Particularly, in the present invention, as the means for carrying out the change emphasizing processing, a subtraction processing means for subtracting a predetermined DC offset potential component from an electric signal containing luminance information and the DC offset potential component are subtracted. An amplification means for amplifying the electric signal at a predetermined amplification factor is provided later.

That is, the DC offset potential as an unnecessary component is subtracted from the electric signal containing the luminance information and then amplified, so that the background level is lowered by the subtracted amount, and the dynamic range of the amplifying means is made effective. By utilizing it, it becomes possible to perform amplification at a high amplification rate.
Therefore, a minute amount of phase change becomes remarkable, and it becomes possible to observe with a high-contrast image.

A differential processing means can also be used as the change emphasis processing means. . Also by the differential processing, a minute amount of phase change becomes remarkable, and it is possible to observe with a high-contrast image.

According to the present invention, the microscope image after signal processing is continuously displayed on the monitor (the speed can be adjusted by the scanning mechanism), and the background level and the signal amplification factor can be adjusted while observing the display screen. Because it can be done sequentially,
The change emphasis process can be completed in one step. Therefore, the processing can be performed on the shortest route, and the time can be shortened.

Furthermore, in the past, it was necessary to store the duplicated image each time since the image was formed and then duplicated in order to process the image. According to the present invention, since the electric signal itself before image formation is processed, it is not necessary to store a duplicate image, and a memory such as a buffer can be omitted.

As the laser scanning microscope used in the present invention, there are a laser scanning differential interference microscope, a laser scanning phase contrast microscope, etc., which scan the sample surface by a laser spot. Various microscope techniques are possible as long as they are provided with a scanning means for transmitting and continuously output signals, and the polarization processing method is not particularly limited.

As this scanning mechanism, the laser beam may be fixed, and a sample stage movable in an in-plane direction perpendicular to the optical axis may be provided to move the stage. Then
Alternatively, the sample may be fixed and the illumination spot of the laser beam may be scanned. As a method of scanning the illumination spot, there are a scanning mirror, a polygon mirror, an acousto-optic device and the like. The scanning unit is not particularly limited as long as it is a scanning unit capable of relatively scanning the condensing position of the light beam by the objective lens and the test sample.

As the optical system, either a reflective optical system or a transmissive optical system may be used. As the sample to be inspected, a minute step sample or a weak phase object can be observed.

[0020]

FIG. 1 is a schematic diagram showing the flow of image signal processing of a laser scanning microscope according to an embodiment of the present invention.

In FIG. 1, a portion surrounded by a broken line is a ray.
The scanning microscope main body 9. The light modulated by the sample is detected by the detector 10 and converted into an electric signal by the photoelectric converter 11 (a signal 12 is shown as an example of the converted electric signal). A background signal corresponding to a predetermined DC offset potential is subtracted from the converted electric signal by the subtraction processing circuit 13 (a signal 14 is shown as an example of the electric signal from which a fixed amount of the background signal is removed). . The electric signal from which the background signal has been removed is amplitude-amplified by the amplification processing circuit 15 (a signal 16 is shown as an example of the amplified electric signal).

The electrical signal subjected to such a series of signal change emphasis processing is scanned by the scanning mechanism 19 in the laser scanning microscope.
Synchronized with the sampling signal 17 extracted from
A two-dimensional image 18 of the sample surface is formed.

FIG. 3 is a partial sectional view showing an example of a weak phase object surface as a surface to be inspected. In FIG. 3, the surface to be inspected has a step-like minute step, and one step is 7.5.
~ 10.0Å.

FIG. 4 is a diagram in which one line of the luminance distribution detected by the surface to be inspected in FIG. 3 is extracted and displayed.

In FIG. 4, (a) shows an unprocessed luminance distribution, and (b) shows a luminance distribution when a subtraction process and an amplification process are performed as the signal processing according to the present invention.
Compared to (a), (b) can clearly recognize the step on the sample surface. Thereby, the contrast of the two-dimensional image can be greatly improved.

[0026]

As described above, according to the present invention, the change emphasis processing is performed in which the DC offset potential component as the background signal is subtracted from the electric signal including the luminance information before the image forming processing, and the amplified signal is amplified. There is an effect that a minute amount of phase change can be observed with high contrast and image processing can be performed at high speed.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a flow of image signal processing of a laser scanning microscope according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a system configuration of a laser scanning differential interference microscope in a conventional example.

FIG. 3 is a partial cross-sectional view showing an example of a weak-phase object surface as a surface to be inspected.

FIG. 4A is a diagram showing an unprocessed luminance distribution according to a conventional example, and FIG. 4B is a diagram showing a luminance distribution when a subtraction process and an amplification process are performed as signal processing according to the present invention. Is.

[Explanation of symbols]

 9 ... Laser scanning microscope main body 10 ... Detector 11 ... Photoelectric converter 12, 14, 16 ... Electrical signal 13 ... Subtraction processing circuit 15 ... Amplification processing circuit 17 ... Sampling signal 18 ... Two-dimensional image

Claims (1)

[Claims] 1. A laser light source, an optical system for narrowing the light from the laser light source into a spot shape on the sample surface, and a scanning means for scanning the sample surface by the laser spot. In a laser scanning microscope provided with an image forming processing means for forming an image by an electric signal and position information of brightness information on the sample surface obtained from the laser spot, the brightness before the image forming processing. A subtraction processing unit that subtracts a predetermined DC offset potential component from an electric signal containing information, and an amplification unit that amplifies the electric signal at a predetermined amplification factor after subtracting the DC offset potential component. A laser scanning microscope.