JP2918995B2 - Confocal optics - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a confocal optical system.

(Prior art)

Confocal optics have been known for a long time, and USPatent30
Proposed in 13467. FIG. 7 shows the optical system.
The light 2 emitted from the light source 1 passes through the half mirror 3 and is irradiated on the sample 5 by the condenser lens 4 in a spot shape. The reflected light from the sample 5 passes through the lens 4 and is reflected by the half mirror 3 to be collected again. This light condensing position is a position conjugate with the light condensing position of the lens 4, and an optical system having the pinhole 6 at this position is called a confocal optical system. Reference numeral 7 denotes a photoelectric detector which receives collected light and converts it into an electric signal.

A confocal scanning optical microscope applies such a confocal optical system to a scanning optical microscope.

FIG. 8 shows an example of an optical system of a confocal scanning optical microscope, which will be described. The laser beam 12 emitted from the light source 11 is
The beam is expanded by the beam expander 13 to a required beam diameter. The expanded laser beam 12 passes through the half mirror 14 and enters an optical deflector 15 provided at a position conjugate to the pupil position of the objective lens 21. As the optical deflector 15 rotates, the laser beam 12 is deflected in the X direction. The laser beam 12 reflected by the optical deflector 15 passes through pupil transmission lenses 16 and 17, and then enters an optical deflector 18 provided at a position conjugate to the pupil position of the objective lens 21. The laser beam 12 is deflected in the Y direction by turning the optical deflector 18 in a direction orthogonal to the turning direction of the optical deflector 15. The laser beam 12 two-dimensionally scanned by these optical deflectors passes through a pupil projection lens 19 and an imaging lens 20, and is incident on an objective lens 21. Then, a spot limited by diffraction is generated on the sample 22, and the sample 22 is two-dimensionally scanned with the spot. If the sample 22 is a reflective object, the laser beam 12 returns to the optical path at the time of incidence, is reflected by the half mirror 14, and is condensed by the condenser lens 23. There is a pinhole 24 at the condensing position, and only light that has passed through the pinhole 24 enters the photoelectric detector 25. A sample image is obtained by processing the electric signal output from the photoelectric detector 25.

FIG. 9 is another example of a confocal scanning optical microscope. 8th
The same components as those in the figure are denoted by the same reference numerals, and description of the operation is omitted. In this example, the reflected light from the sample 22 is reflected by the half mirror 14 placed between the optical deflector 18 and the pupil transmission lens 17 and collected by the condenser lens 26. Scans linearly, a one-dimensional CCD 27 is used as a photoelectric detector. A confocal optical system is obtained by reducing the width of the light receiving surface of the one-dimensional CCD 27 to a linear scanning area as compared with the spot diameter.

Such a confocal scanning optical microscope can obtain an image with good contrast as compared with a normal optical microscope.

-There is resolution in the optical axis direction.

And so on.

[Problems to be solved by the invention]

The greatest feature of the confocal optical system is that it has a resolution in the optical axis direction. The resolution in the optical axis direction depends on the size of the spot diameter on the pinhole and the size of the pinhole diameter. This is analyzed by "Optics.18.8" and "Optical Scanning Microscope" (published by Japan Optical Society). According to this, when the pinhole diameter is smaller than the spot diameter, the resolution in the optical axis direction increases, and when the pinhole diameter is larger than the spot diameter, the resolution in the optical axis direction decreases. Therefore, it is desirable to reduce the pinhole diameter as much as possible in order to increase the resolution in the optical axis direction.

However, when the diameter of the pinhole is reduced, the amount of light passing through the pinhole decreases, so that, for example, an image cannot be obtained with a sample having a low reflectance or a fluorescent sample. In order to solve such a problem, the diameter of the pinhole may be increased in order to increase the amount of light passing through the pinhole at the expense of resolution in the optical axis direction. In this case, it is more convenient to be able to continuously change the pinhole diameter because the amount of light returning from the sample depends on the sample to determine how much light passes.

However, since the pinhole diameter is about several tens of μm, it is very difficult to continuously change the diameter. Also, in the case of a one-dimensional CCD, the size of the light receiving surface is constant and cannot be changed continuously.

In view of the above problems, the present invention confocals such that the same effect as when the pinhole diameter or the size of the light receiving surface is continuously changed while the pinhole diameter or the size of the light receiving surface is kept constant is obtained. It is intended to provide an optical system.

[Means and actions to solve the problems]

One of the confocal optical systems according to the present invention is configured such that light emitted from a light source is condensed on a sample by an objective lens, and the light generated by the sample is collected by an aperture arranged in a conjugate relationship with the condensing position of the objective lens. A condensing lens for condensing return light from the sample on the opening in a confocal optical system that receives light by a photoelectric detection element via a light-receiving element, and a spot of the return light from the sample condensed by the condensing lens. A spot diameter conversion optical system for changing the diameter is provided.

Another one of the confocal optical systems according to the present invention is such that light emitted from a light source is condensed on a sample by an objective lens, and light generated by the sample is disposed at a position conjugate with a condensing position of the objective lens. In a confocal optical system that receives light with at least a one-dimensional recognizable photoelectric detection element, a condensing lens that condenses return light from the sample on the photoelectric detection element, and condensed by the condensing lens A spot diameter conversion optical system for varying the spot diameter of the return light from the sample.

Further, the present invention is characterized in that the spot diameter conversion optical system varies the diameter of the incident light beam of the condenser lens or varies the focal length of the condenser lens.

According to the present invention, the pinhole diameter or the size of the light receiving surface is changed by continuously changing the spot diameter focused on the opening or the light receiving surface with respect to the size of the opening or the light receiving surface of the photoelectric detection element. The same effect as that obtained by continuously changing the length can be obtained.

Embodiment FIG. 1 shows a first embodiment according to the present invention. The same components as those in FIG. 8 are denoted by the same reference numerals, and their operations are omitted.

In this embodiment, the spot diameter is changed without changing the pinhole diameter or the size of the light receiving surface.

The diameter φ of a spot formed when parallel rays are collected by a lens is given by f = 1.22 × f × λ / d, where f is the focal length of the lens, d is the radius of a light beam incident on the lens, and λ is the wavelength of light. (1)

As is apparent from the equation (1), at least one of f, d, and λ may be changed to change the spot diameter.

Therefore, in this embodiment, the spot diameter is changed, and a method of changing the value of d in the equation (1) is used to change the spot diameter. As shown in FIG. 1, an afocal zoom optical system 30 is arranged in front of the condenser lens 23 in order to change the value of d.

FIG. 2 is an example of an afocal zoom optical system. The lenses 31 and 33 are convex lenses, and the lenses 32 and 34 are concave lenses. The lenses 32 and 33 are configured to move continuously between X1 and X2 and between X3 and X4, respectively. When the lens 32 is at the position of X1 and the lens 33 is at the position of X4 as shown in FIG. 2 (A), the incident light beam converges at the lens 31, but the beam diameter between the lenses 31 and 32 is so small that it is too small. No. But the lens
Since the beam is wide between 32 and 33, the light beam that has passed through the lens 32 spreads during this time.The spread light beam has a narrow space between the lenses 33 and 34, so the light beam diameter does not become very small during this time.
The beam diameter d1 emerging from the incident light beam system is d <d
It becomes d1. On the other hand, as shown in FIG.
When X2 and lens 33 are at the position of X3, the luminous flux is
And 32, and the luminous flux between the lenses 33 and 34 becomes smaller, so that the luminous flux diameter d2 coming out of the lens 34 is d> d2. Therefore, as the lenses 32 and 33 move continuously, the diameter of the light beam coming out of the lens changes continuously between d1 and d2.

 Let's specifically substitute a numerical value.

For example, when f = 50 mm, λ = 0.5 μm, and d = 2 mm, if the magnification of the afocal zoom is 0.25 × to 2 ×,
The diameter of the luminous flux emerging from the lens 34 is 2 × d1 = 4 mm 0.25 × d2 = 0.5 mm Therefore, the diameter of the spot formed on the pinhole 24 by the lens 23 is 2 × φ1 = 7.6 μm 0.25 When x, φ2 = 61 μm.

If the diameter of the pinhole 24 is about 15 μm, the spot diameter becomes smaller than the pinhole diameter by setting the magnification of the afocal zoom to 1 × to 2 × when the amount of light returning from the sample is small. The loss of light quantity at the pinhole is reduced, and an image is obtained. However, in this case, the resolution in the optical axis direction can hardly be obtained.

If the amount of light returning from the sample is large,
By setting the magnification of the afocal zoom to 0.25 × to 0.7 ×, the spot diameter becomes larger than the pinhole diameter, so that although there is a light amount loss at the pinhole, an image can be obtained while having axial resolution.

As described above, by continuously changing the magnification of the afocal zoom according to the amount of light returning from the sample,
An optimal state for obtaining an image is realized.

Although the present embodiment has been described using specific numerical values, the present invention is not particularly limited to these numerical values. Similarly, there is no limitation on the type and number of lenses of the afocal zoom optical system.

FIG. 3 shows a second embodiment according to the present invention. The same components as those in FIG. 9 are denoted by the same reference numerals, and description of the operation is omitted.

In this embodiment, the spot diameter is changed similarly to the first embodiment.

In this embodiment, in order to change the diameter of the spot,
A method of changing the value of f in equation (1) is used. Therefore, here, a variable focal length optical system 40 is arranged in front of the one-dimensional CCD 27 in order to change the value of f.

FIG. 4 shows an example of a variable focal length optical system. The lens 41 is a concave lens, and the lens 42 is a convex lens. When the composite focal length f of the two lenses of the variable focus optical system is determined by paraxial theory, if the focal lengths of the two lenses are f1 and f2 and the distance between the two lenses is t, then 1 / f = 1 / f1 + 1 / f2-t / (f1 × f2). Therefore, in order to change f, the lens interval t may be changed.

That is, as shown in FIG.
Assuming that the distance between the light spots is 1,2 and the distance between the lenses is t2, the focal point of the light spot is far away and the focal length is long, and as shown in FIG.
If t1, the focal length becomes shorter.

As described above, when the lens interval changes, the focal length changes and the focal position changes, so that the position of the light receiving surface of the one-dimensional CCD 27 does not match the spot position. Therefore, a moving mechanism for moving the lenses 41 and 42 in parallel with a fixed focal length is required so that the position of the light receiving surface of the one-dimensional CCD and the spot position match in accordance with the change in the lens interval.

 Next, a specific numerical value will be substituted.

 For example, when the focal length of the lens 41 is f1 = −20 mm, the focal length of the lens 42 is f2 = 20 mm, the lens interval is t1 = 25 mm, and t2 = 5 mm. When t1 = 25 mm, f = 16 mm. The spot diameter is φ1 = 4.9 μm when t1 = 25 mm and φ2 = 24.4 μm when t2 = 5 mm.

By continuously moving the lens 41 in this manner, the spot diameter can be continuously changed from 4.9 μm to 24.4 μm.

Therefore, even if the size of the light receiving surface of the one-dimensional CCD is set to about 10 μm, an optimum state for obtaining an image according to the amount of light from the sample is realized as in the first embodiment.

FIG. 3 shows a one-dimensional CCD 27 when the sample 22 is a transmission sample.
In the figure, there is shown an example for returning transmitted light, and reference numerals 44 and 46 denote examples of an optical system therefor. The lens 46 is arranged so that the front focal position coincides with the condensing position of the lens 21 in order to convert the light transmitted through the sample 22 into a parallel light beam. The parallel light beam emitted from the lens 46 enters the corner cube 44. The corner cube 44 is arranged such that its vertex P coincides with the rear focal position of the lens 46. Therefore, the light reflected by the corner cube returns along the same optical path as the incident light, so that the transmitted light is also detected by the one-dimensional CCD 27.

FIG. 5 shows a modification of the present embodiment. A variable focus lens 50 is used to change the focal length. The variable focus lens 50 changes the refractive index of the lens material by applying a voltage to the lens material by a voltage source 51. Therefore, by continuously changing the voltage from V1 to V2, the focal length can be changed continuously with one lens.
As in the case of FIG. 4, the focus variable lens 50 is adjusted so that the spot comes on the one-dimensional CCD 27 when the focal length is changed.
A moving mechanism for moving is necessary.

Although the present embodiment has been described using specific numerical values, the present invention is not particularly limited to these numerical values. Also, the type and number of lenses are not limited as long as the same effects can be obtained for the lens configuration of the optical system.

FIG. 6 shows a third embodiment according to the present invention. The same reference numerals are given to the same components as those in FIG. 8, and the description of the operation will be omitted.

In this embodiment, the light from the sample 22 is incident on the photoelectric detector 25 as a parallel light beam without being collected. Light from a position that is not conjugate with the sample 22 does not become a parallel light beam, so that it can hardly pass through the stop 61. For this reason, it has the same function as the case where the pinhole is placed at the light condensing position in FIG.

In this embodiment, an afocal zoom 60 similar to that shown in FIG. 2 is used in the beam expander in order to change the diameter of the light beam incident on the stop 61. The diameter of the light beam entering the stop 61 is the same as the light beam exiting the afocal zoom 60. Therefore, by continuously changing the luminous flux exiting the afocal zoom 60, an optimal state for obtaining an image according to the amount of light from the sample can be realized. However, since the light from the sample 22 is determined by the size of the pupil of the condenser lens 21, the range in which the diameter of the light beam exiting the afocal zoom 60 is changed
It must be smaller than the size of the 21 eyes.
In the present embodiment, the diameter of the diaphragm 61 is several mm,
Its diameter can also be varied. Therefore, by using the function of changing the light beam diameter by the afocal zoom 60, a wide range of light amount adjustment can be realized.

Although the embodiments of the present invention have been described above, the afocal zoom optical system and the variable focal length optical system can be used in any of the embodiments.

〔The invention's effect〕

The confocal optical system according to the present invention can easily realize the same effect as continuously changing the pinhole diameter or the size of the light receiving surface while keeping the pinhole diameter or the size of the light receiving surface constant. is there.

[Brief description of the drawings]

1 and 2 are diagrams showing an optical system of a first embodiment of the present invention, FIGS. 3 and 4 are diagrams showing an optical system of a second embodiment, and FIG. 5 is a diagram of the second embodiment. FIG. 6 is a diagram showing a modification, FIG. 6 is a diagram showing an optical system of a third embodiment, FIG. 7 is a diagram showing the principle of a confocal optical system, and FIGS. 8 and 9 are conventional examples of a confocal optical system. FIG. 1,11 light source, 6,24 pinhole 7,25 photoelectric detector, 27, one-dimensional CCD 30,60 afocal zoom optical system 40, variable focal length optical system, 61 … Aperture

Claims (4)

(57) [Claims] A light emitted from a light source is condensed on a sample by an objective lens, and light generated by the sample is photoelectrically detected through an opening arranged in a conjugate relationship with a condensing position of the objective lens. A condensing lens for condensing the return light from the sample on the aperture, and a spot diameter for varying the spot diameter of the return light from the sample condensed by the condensing lens A confocal optical system comprising a conversion optical system. 2. A light emitted from a light source is condensed on a sample by an objective lens, and light generated by the sample is recognizable in at least a one-dimensional direction disposed at a position conjugate with a condensing position of the objective lens. In a confocal optical system that receives light with a simple photoelectric detection element,
A condenser lens for condensing the return light from the sample on the photoelectric detection element, and a spot diameter conversion optical system for changing a spot diameter of the return light from the sample condensed by the condenser lens. A confocal optical system. 3. The confocal optical system according to claim 1, wherein the spot diameter conversion optical system changes an incident light beam diameter of the condenser lens. 4. The apparatus according to claim 1, wherein the spot diameter conversion optical system changes a focal length of the condenser lens.
Or the confocal optical system according to 2.