JPH01282515A - Beam scanning type optical microscope - Google Patents

Abstract

PURPOSE:To obtain an inexpensive, easy-to-adjust optical system for the beam scanning type optical microscope by providing an optical system which selects light beams from light sources of plural colors selectively. CONSTITUTION:This optical microscope uses the laser light sources 1, 2, and 3 of three colors as beam light sources. Light beams (a) from the light sources 1, 2, and 3 are converged by condenser lenses 4, 5, and 6 on the centers of modulation of optical modulating elements, e.g. AOMs (Acoustic Optic Modulator) 7, 8, and 9. Then a high-frequency electric signal is sent from a control circuit to the three AOMs 7, 8, and 9 to switch the light beams (a) of the three colors in order with time (select one color) according to the high-frequency electric signal. Consequently, expensive polarizing elements are reduced greatly and the detection optical system is simplified.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a beam scanning optical microscope, and particularly to a beam scanning optical microscope having an inexpensive scanning mechanism suitable for a scanning color optical microscope. Regarding.

(Prior art) Conventionally, as a means to further improve the performance of an optical microscope, a confocal optical system has been used to scan a sample with a narrowly focused light beam and obtain an optical image of the sample from the intensity distribution of the beam reflected light. Scanning optical microscopes are known. By using a confocal optical system in this way, it is possible to obtain images with good resolution and high contrast.

This beam-scanning optical microscope generally uses laser light as its light source because it is easy to obtain a narrow light beam, and also uses a polychromatic (generally three colors of red, green, and blue) light beam to create a color image. It is possible to obtain an image of

On the other hand, in order to obtain an image in real time, a scanning speed comparable to the number of frames generally used in television is required.

Known methods for scanning this light beam include scanning using a galvanometer (vibrating mirror) or polygon mirror (polygon rotating mirror), but although galvanometers are inexpensive, they generally have a low scanning speed. Although it is possible to use it for vertical scanning, it is difficult to use it for horizontal scanning.

Additionally, polygon mirrors have faster scanning capabilities than galvanometers and can also handle horizontal scanning, but they are large and relatively expensive, and the vibrations of the curved mirror degrade the screen when used at high magnification. There was a problem.

Therefore, a galvanometer is used for vertical scanning, and an acousto-optic polarizing element (hereinafter referred to as AOD), which is extremely expensive but capable of high-speed scanning and has no mechanically moving parts, is used for horizontal scanning.
A typical configuration uses an optical device (Aeoust Optical Device).

By the way, since the scanning angle (deflection angle) of an AOD depends on the wavelength of the light used, in conventional beam scanning optical microscopes, when obtaining color images, the three color light beams are separated from the AOD of different birds. After being deflected, the above-mentioned light beams are superimposed on the same optical axis, and then the light beams are made to enter a vertical scanning galvanometer.

Therefore, one detector for the reflected light from the sample was also provided, one for each of the three colors of light beams reflected from the sample.

(Problem to be Solved by the Invention) However, a deflection element for horizontal scanning, such as an AOD, is very expensive, and as described above, in the conventional beam scanning optical microscope, this expensive deflector is used for multiple colors, for example, Since it is necessary to use each color of light beam, there is a problem in that the cost of the entire device becomes very expensive. Furthermore, since the detector for the reflected light from the sample also requires a beam of three colors, for example, there is a problem in that the price increases further. Furthermore, having multiple optical systems in this manner has the drawback of complicating the device configuration and complicating the adjustment work for the optical systems.

The present invention has been made in order to solve the above-mentioned problems.The present invention has been made to reduce the number of expensive optical deflection elements as much as possible, and to simplify the detection optical system. We aim to provide a beam scanning optical microscope that can reduce costs and simplify equipment adjustment work.
purpose.

[Structure of the Invention] (Means for Solving the Problems) The beam scanning optical microscope of the present invention scans and irradiates a sample with a light beam, and scans and irradiates the sample with a light beam based on the intensity distribution of reflected light from the sample. In a beam scanning optical microscope that obtains an optical image, a beam output mechanism that outputs a plurality of color light beams is provided corresponding to each of the plurality of beams from the beam output mechanism, and the intensity of the beam is adjusted for each color. a beam combining optical system that superimposes the beams modulated in brightness by each of the brightness modulating elements at a predetermined angle with respect to the same optical axis; and a beam combined by the beam combining optical system. 2 beams of light to the sample surface
a beam deflection mechanism that scans dimensionally; a focusing optical system that focuses the beam light output from the beam deflection mechanism on the sample surface; and a reflection system that extracts beam reflected light from the sample and detects the light intensity of the reflected light. Time-divisionally controlling the drive of the photodetection mechanism and each of the brightness modulation elements at a predetermined period,
a control unit that controls driving of the beam deflection mechanism/mechanism based on the predetermined cycle to perform desired beam scanning; and a control unit that reads the output from the reflected light detection mechanism in synchronization with the beam scanning cycle to form a multicolor image. The invention is characterized in that it has an image processing mechanism that obtains.

As the beam deflection mechanism, an optical deflection element such as an AOD,
It is preferable to use it at least in a beam deflection system on the high-speed scanning side.

(Function) In the present invention, by providing an optical system that selects light beams from light sources of multiple colors at high speed, a set of vertical and horizontal scanning optical systems is provided, and furthermore, a set of vertical and horizontal scanning optical systems is provided. By time-divisionally using the optical system in synchronization with the optical system that selects the light beam, an inexpensive and easily adjustable optical system for a beam scanning optical microscope can be obtained.

(Example) Hereinafter, an example in which the present invention is applied to an optical system of a scanning color optical microscope will be described with reference to the drawings.

In this embodiment, three color laser light sources 1 and 2 are used as beam light sources.
．． For example, red is a He-Ne laser (wavelength: 833 nm); green is an Ar laser (wavelength: 5 nm).
15 nm), blue is a He-Cd laser (wavelength 441.
8 nm) may be used individually, or when obtaining laser beams having several oscillation spectra by spectroscopy, for example,
Red is 11e-Ne laser (wavelength 833nl6)
Green and blue are obtained from Ar laser (wavelength 515 run and 4
88 r+m) may be obtained by spectroscopy. Furthermore, an RGB laser capable of simultaneous oscillation of three light source colors may be used.

The light beam a output from each light source 1.2.3 is transmitted through a condenser lens 4.5.6 to an optical modulation element such as p
, OM (A OM: Acoust Optic
Modulator) 7.8.9 is focused to the modulation center. This is because, due to the nature of the AOM, the smaller the light beam diameter, the faster the brightness modulation can be performed.

A high-frequency electric signal is sent to these three AOMs 7.8.9 from a control circuit (not shown), and based on this high-frequency electric signal, the three color beams a are sequentially switched over time (one color is controlled).

This control is basically a switch operation to select one of multiple colors, but it also takes advantage of the property that the diffraction efficiency can be changed by changing the intensity of the AOM's high-frequency signal. This makes it possible to correct differences in intensity between color light sources (including changes over time), correct differences in transmittance due to the deflection angle of the AOD, and adjust illuminance in accordance with the reflectance of the sample.

In this way, the beams of each of the three colors that passed through the AOM 7.8.9 at different timings are transmitted to the lens systems 10.11 and 10.11.
．． At step 12, parallel light having a predetermined irradiation angle is shaped into a parallel light having a size that matches the entrance pupil of an optical deflection element, for example, an AOD, which will be described later. AOD 1 at angle
6. Each of the mirrors 13, 14, 15 is a guichroic mirror having wavelength selectivity that reflects only the beam light from the light beam 11iX1.2.3 and transmits light of other wavelengths.

A high frequency electric signal for deflecting the light beam is given to the AOD 16 from a control circuit (not shown), and by changing this high frequency electric signal, the incident light beam can be deflected in a predetermined direction. can.

By the way, since the deflection angle of the AOD 16 has wavelength dependence with respect to the incident light, it is necessary to determine the incident angle in accordance with the wavelength of the beam light and also change the frequency of the high-frequency electric signal for deflection. That is, in order to scan at the same angle, for example, for red, the frequency is 584 MHz to 94.7 MHz.
MHz, from 75.5MHz to 120.5MHz in green
For blue, scanning is controlled by changing the applied frequency from 82.7 MHz to 132.3 MHz. At this time, the switching of the frequency range for each color is performed using the AOM7.8 described above.
．． This is done in synchronization with the switching timing of the three color beams by 9. For example, when a red beam light is selected in AOM 7.8.9, scanning is performed using a high frequency electrical signal corresponding to the beam wavelength, for example, in a frequency range from 58.3 MIIz to 94.7 MHz.

In this way, the light beam b that has been one-dimensionally scanned, for example, in the horizontal direction, by the AODl 6 is located at its deflection center position, that is, the AODl
The beam passes through a relay lens 17 for relaying the deflection center position of No. 6 to the deflection center position of a vertical scanning system, is transmitted through a half mirror 18, and is incident on the deflection center of a vertical scanning system, for example, a galvanometer 19.

In the galvanometer 19, the incident light beam is further scanned in a direction perpendicular to the scanning direction by the AOD 16, for example, in a vertical direction, to form a two-dimensionally scanned light beam.

By the way, since the galvanometer 19 has a structure that performs mechanical scanning, it is not suitable for high-speed scanning.In this embodiment, the galvanometer 19 performs vertical scanning, which is the same as normal television scanning, and horizontal scanning is performed by AOD16. I made it happen. That is, a control circuit (not shown) rotates the galvanometer 19 so as to perform one vertical scan during a desired number of horizontal scans by the AODl 6.

In this way, the two-dimensionally scanned beam C passes through the second relay lens 20 for relaying its deflection center position, that is, the deflection center position of the galvanometer 19 to the entrance pupil position of the objective lens 22, and passes through the half mirror 21. The light passes through and enters the entrance pupil of the objective lens 22 in the form of parallel light with angular information, and is imaged by the objective lens 22 as a narrowed light spot that is scanned and irradiated two-dimensionally onto the sample 23.

The reflected light beam d from the sample 23 is transmitted through the objective lens 22 and the half mirror 21 due to the reversibility of the optical path of the beam light.
, the second relay lens 20 and the galvanometer 19, a portion of it is reflected by the half mirror 18, passes through the imaging lens 24, and forms an image on the detector 25.

Here, since the beam light passes through the galvanometer 19 both in the forward and backward directions, the vertical scanning is canceled and the locus of the light spot imaged on the detector 25 is a locus of only the horizontal scanning component.

The detector 25 is configured to detect an image (such as a photodiode), for example.
For example, it may be a monocular detector that is insensitive to the position of a spot, or it may be a CCD line sensor in which light receiving sections are arranged in a row in the scanning direction.

In the case of a monocular detector, the output of the detector is sampled a desired number of times (the number of horizontal pixels) at a predetermined timing during - times of horizontal scanning, and in the case of a CCD line sensor, etc., the output of the detector is sampled during - times of horizontal scanning. Control is performed to extract information equal to the number of horizontal pixels possessed by the sensor each time a horizontal scan is completed.

A color image is obtained by superimposing the images obtained by two-dimensional scanning while changing the colors.

By the way, the timing of switching colors, that is, AOM7.8
．． Various timings can be considered for the beam switching timing by 9, but since the response of the vertical scanning galvanometer 19 is slow, the frame speed cannot be fast if three monochromatic two-dimensional images are captured to form one color image. and AOD
Since AOM7.8.9 cannot provide a fast response, the time required for color switching cannot be ignored if three color data are taken for each pixel. It is efficient to change the color every horizontal scan. That is, a desired number of horizontal scans may be performed while sequentially switching the three colors during one vertical scan.

On the other hand, as an auxiliary observation means, in this embodiment, an auxiliary observation mechanism consisting of a white light source 27, half mirrors 21 and 26, and a trinocular tube 28 is provided.

The light output from the white light source 27 passes through the half mirror 26 and is irradiated onto the surface of the sample 23. The light reflected by the sample 23 is reflected by the half mirrors 21 and 26 in this order, and reaches the trinocular tube 28. Here, if the sample is irradiated with laser light and white light at the same time, the performance as a scanning color optical microscope will deteriorate, so the original n1 constant system using laser light and the auxiliary observation system should be used as an alternative. .

Here, an example of the operating characteristics of the AOD used in the above embodiment will be described below with reference to FIG. 3.

The AOD 16 has an optimal incident angle for each color (wavelength), but the band of high-frequency electrical signals (ultrasonic signals) necessary for scanning (deflection) differs depending on each color, and the scanning range is limited.

FIG. 3 shows an example of parameters when output scanning ranges of three colors (R, GSB) are used so as to overlap as much as possible.

■Angle of incidence■ The f (frequency) of the scanning ultrasonic waves will be changed for each color. In particular, the need to change the frequency f makes it impossible to scan RGB at the same time, so AO
The need for three-color time division using D arises.

For example, each R1G, B for a predetermined deflection surface S of the AOD
The relationship between the incident angles θR1θG1θB of the lasers is such that with the G laser at the center, the R laser is about 0.2' on the AOD side with respect to the G laser, and the B laser is about 0.2' on the opposite side of the R laser with respect to the G laser. If the angle of incidence is 1°, then
The AOD for each R, G, and B laser is set to R (50 to 100 MHz), G (75,5 to 120.5 MHz), and B (76 to 120.5 MHz), respectively.
When operated at a high frequency of 138MIIz), the deflection angle of each color is θR-
(e.g. (2o8~5.5")), θG- (e.g. (3,3~5.3°)), eD-C e.g. (3,0~5
．． 8'')), and the common portion of the deflection widths of these colors can be taken out and used as a scanning beam.

In this embodiment, as explained above, the laser beam of each color from the light source is selected at a predetermined cycle by AOM7.8.9, and the application of high-frequency electrical signals to the AOD is changed at a timing synchronized with the cycle. This method performs three-color time-division control.

By the way, the configuration of the present invention is not limited to the above-described embodiment, and for example, the configuration of the present invention is not limited to the above-mentioned embodiment.
A configuration may also be adopted in which this is performed by OD.

Hereinafter, such an embodiment will be explained with reference to FIG. 4. Note that the same parts as in FIG. 1 are given the same reference numerals, and the explanation of the overlapping parts will be omitted.

The difference from the first embodiment shown in FIG. 1 is that the AOD 29 is also used for the slower scan, that is, the vertical scan in this example.

That is, the optical beam deflected in the horizontal direction by the first AODl 6 is transmitted to the second AOD 31 by the relay lens 17.
The AOD 31 scans in the vertical direction to obtain a two-dimensionally scanned beam C.

With such a configuration, since the AOD 31 does not have optical path reversibility when efficiency is taken into account, it becomes difficult to transmit the reflected light d from the sample 23 in the opposite direction through the second AOD 31 and detect it. -18 is arranged between the half mirror 21 and the relay lens 20, and the imaging lens 24 and the detector 3 are placed on the reflection optical axis of the half mirror 18.
A detection system consisting of 2 is provided.

At this time, the locus of the light spot of the reflected light that forms an image on the detector 32 becomes a two-dimensional locus, so a CCD line sensor (-dimensional CCD element) like the embodiment in Section 1 above is used. It is not possible. For this reason, a monocular photodiode, a two-dimensional CCD sensor, or the like is used as the detector.

In other respects, the operation is the same as that of the embodiment shown in Fig. 1, but in this embodiment, both horizontal and vertical scanning are performed by AODl6.31, so the left and right scanning is simply performed in the direction from the top to the bottom of the optical path. In addition to scanning sequentially, depending on the strength of the control circuit of the AODl6.31, it is possible to scan vertically, horizontally, or upside down.
It can easily accommodate various scanning methods such as partial scanning (scanning only a part of the screen), diagonal scanning, and interlaced scanning.

In addition, in this example as well, as shown in FIG.
The 83 colors of light must be incident on the 1 m tfml(7) AOD 16i at the angle shown in FIG. 3 above.

At the same time, the first AOD 31 is arranged such that the beam scanned by the first AOD 16 is incident on the second AOD 31 scanning in the orthogonal direction at the above-mentioned angle.
1, it is necessary to adjust the angle to both AODl 6.31 three-dimensionally.

Fortunately, the AOD is almost insensitive to angles perpendicular to the scanning direction (plane) (angles projected onto the virtual reflective surface) of a few degrees, so when entering the first AOD 16, It is possible to set a predetermined angle with respect to the second AOI 31 in the orthogonal direction in advance.

In this case, if the entrance pupil of the second AOD 31 can be designed so that vignetting etc. does not occur, the two AODs 6.3
It is also possible to omit the relay lens 17 between the two.

In this way, by performing both horizontal and vertical directions at AODl 6.31, high-speed scanning irradiation of the beam is possible.
Moreover, it can easily correspond to various scanning methods.

[Effects of the Invention] As explained above, according to the beam scanning optical microscope of the present invention, the number of expensive optical deflection elements can be minimized and the detection optical system can be simplified. It is possible to reduce the overall cost and simplify the device adjustment work.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a beam scanning optical microscope according to an embodiment of the present invention, FIG. 2 is a diagram for explaining the beam scanning procedure, and FIG. 3 is an example of the operation of the AOD used in the embodiment. FIG. 4 is a diagram for explaining the configuration of another embodiment of the present invention, and FIG. 5 is a diagram for explaining an example of the operation when AODs are two-dimensionally combined. 1.2.3... Laser light source, 7.8.9...
... light modulation element (AOM), 16 ... light deflection element (AOD), 17 ... relay lens, 1
9... Galvanometer, 20... Second
Relay lens, 22...Objective lens, 23.
...Sample, 24...Imaging lens, 25.
...Detector, 27...White light source, 28.
. . . 3 spectacle tubes, 31 . . . second optical deflection element (AOD), 32 . . . detector. Applicant Tokyo Electron Co., Ltd. Agent Patent Attorney Sasa Suyama - Figure 1 Horizontal scanning sampling number Figure 2

Claims (1)

[Claims] A beam scanning optical microscope that scans and irradiates a sample with a light beam and obtains an optical image of the sample based on the intensity distribution of light reflected from the sample by the light beam, comprising: a beam output mechanism that outputs a beam, a brightness modulation element that is provided corresponding to each of the plurality of beam lights from the beam output mechanism and controls the intensity of the beam light for each color; and a brightness modulation element that is modulated by each of the brightness modulation elements. a beam combining optical system that superimposes the combined beams at predetermined angles with respect to the same optical axis; a beam deflection mechanism that two-dimensionally scans the beam beams combined by the beam combining optical system with respect to the sample surface; a focusing optical system that focuses the beam light output from the beam deflection mechanism on the sample surface; a reflected light detection mechanism that extracts the beam reflected light from the sample and detects the light intensity of the reflected light; and each of the brightness modulation elements. a control unit that time-divisionally controls the drive of the beam deflection mechanism at a predetermined cycle and controls the drive of the beam deflection mechanism based on the predetermined cycle to perform a desired beam scan; 1. A beam scanning optical microscope, comprising: an image processing mechanism that reads output from a photodetection mechanism and obtains a multicolor image.