JPH0332046B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spatial filter for removing noise components such as scattered light included in parallel light such as a laser beam.

[Conventional technology]

Generally, the laser beam emitted from a laser generator has a single mode with good coherence and a diameter of 0.6 to 1.0.
Obtained as a beam of mm. In holographic interference devices, etc., this laser light is expanded to an effective beam diameter and used, but since the laser light contains noise components such as scattered light, the noise components in the laser light are removed. However, it is necessary to create a uniform beam.

For this reason, a laser beam with a diameter of 0.6 to 1.0 mm is
~ Focus the light with a short focal length lens such as a 40x microscope objective lens, and remove noise light such as scattered light that is not focused by 10 ~
A spatial filter is known that blocks light with a 25 μm pinhole and allows only a uniform beam of light to pass through.

In this way, the spatial filter combines a short focus lens and a pinhole with a small hole diameter,
By making the hole diameter of the pinhole match the center maximum energy portion of the laser beam, a filtering effect for removing high-order diffraction patterns is exerted, and a perfect Gaussian beam energy distribution can be obtained.

[Problem that the invention seeks to solve]

However, the optical system of the spatial filter requires a short focal length lens with a focal length of about 4 to 8 mm and a pinhole with a hole diameter of 10 to 25 μm to be correctly aligned on the laser optical axis, but each positioning accuracy is required to be on the μm order, and the adjustment procedure is complicated.
It takes a lot of time.

That is, the adjustment procedure will be described with reference to FIG. In the figure, 1 is a laser beam, 2 is a short focus lens, 3 is a condensing point thereof, 4 is a pinhole having a hole 4A, and 5 is a screen.

Here, the hole 4A of the pinhole 4 has a hole diameter of 10 to 25 μm;
The condensing point 3 of the short focal length lens 2 condensed below this cannot be observed with the naked eye. Therefore, first, the pinhole 4 is fixed, and the short focal length lens 2 is moved further away from the condensing point 3A to allow weak light to pass through the hole 4A. This state is the positional relationship shown in FIG. 3, and a fringe 6 is generated on the screen 5.

Next, the short focus lens 2 moves forward a little in the direction of arrow A. At this time, since the light passing through the pinhole 4 is decentered, the pinhole 4 is slightly moved back and forth and left and right using a cross-movement holder or the like to find the point where the light is strongest.

Further, the short focus lens 2 is moved forward in the direction of arrow A, and the same adjustment is repeated 5 to 10 times. In this way, when the condensing point 3 reaches the hole 4A of the pinhole 4, the adjustment is completed, and a laser beam without fringes 6 can be obtained.

In this way, if it is based on the conventional technology,
The positional relationship between the short focus lens 2 and the pinhole 4 is manually fine-tuned so that the light passing through the pinhole 4 gradually changes from thick and weak to strong light, and the adjustment is made almost by intuition. It took 10 to 15 minutes even for an experienced person.

The present invention has been made in view of the problems of the prior art, and since there is only one correct positional relationship between the short focus lens and the pinhole, the short focus lens and the filtering pinhole must be properly aligned in advance. To provide a spatial filter capable of adjusting the position of an optical axis only by fixing the filter at a fixed position and adjusting a main cylinder so that incident light passes through two centering pinholes.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention provides a main cylinder having a desired axial dimension, and a relatively first and second centering pinholes having a large hole diameter; and a lens/pinhole mounting cylinder formed integrally with or separate from the main cylinder and having one end fixed to the other end of the main cylinder. , the lens・
a short focus lens fixedly provided at the other end of the pinhole mounting tube so as to coincide with the optical axes of the first and second centering pinholes; and the other end of the lens/pinhole mounting tube. A filtering pinhole that is located on the side and is fixedly provided at a condensing position where light is condensed by the short focus lens, and a filtering pinhole that surrounds one end and the other end in the axial direction of the main cylinder. first and second support rings attached to a fixed member; the main cylinder is supported with respect to the first and second support rings; and the main cylinder is adjusted to be vertically rotatable; 1, first and second adjustment screws provided on the second support ring, and the first and second adjustment screws are arranged such that parallel light incident from the outside passes through the first and second centering pinholes. , the main cylinder is configured to be adjusted by a second adjustment screw.

[Function] With this configuration, the main cylinder is rotated upward and downward by adjusting the first adjustment screw, and the parallel light incident from the outside is passed through the first centering pinhole, and the next By adjusting the second adjustment screw, the main cylinder is rotated upward and downward again, allowing the parallel light that has passed through the first centering pinhole to pass through the second centering pinhole. By this operation, the parallel light is focused at the focusing position of the short focal length lens and easily passes through the filtering pinhole provided in advance at this position.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 1 and 2.

In the figure, 11 is a cylindrical main cylinder, and the main cylinder 11 is formed with an axial dimension of, for example, 50 to 60 mm, and has a female threaded part 11A formed at one end thereof and a female threaded part 11B at the other end. is formed, and the cylindrical part has three observation holes 11C, 11C, ... on the top surface, left side, and right side.
is drilled.

Reference numeral 12 indicates a centering pinhole holder screwed onto the female threaded portion 11A on one side of the main cylinder 11, and reference numeral 13 indicates a first centering pinhole holder which is adjustably attached to the holder 12 via three pinhole fixing screws 14. This is a centering pinhole, and the pinhole 13 has a hole diameter of 1~
A hole 13A having a relatively large diameter of 2 mm is bored in the axial direction.

15 is a main cylinder 1 via a lens mounting cylinder 18 which will be described later.
A centering pinhole holder 16 is attached to the female threaded portion 11B on the other side of 1, and a second centering pinhole 16 is adjustably attached to the holder 15 via three pinhole fixing screws 17. A relatively large hole 16A having a hole diameter of 1 to 2 mm is also formed in the pin hole 16 in the axial direction.

Here, the first and second centering pinholes 13 and 16 are attached to the main cylinder 11 so that the optical axes O ₁ -O ₁ coincide with each other, and this is because each pinhole fixing screw 14 and 17 It is adjusted in advance by the manufacturer so that it also coincides with the optical axis of the short focal length lens 19, which will be described later.

18, one end side is the female thread part 11 on the other side of the main cylinder 11.
A lens mounting tube 18 is screwed onto B, and the lens mounting tube 18 is a cylinder having a predetermined axial length, similar to a collimator, etc., and is coaxially aligned with the axis of the main tube 11. It is fixed. On the other hand, 1
9 is a short focus lens fixedly provided on the other end side of the lens mounting tube 18, and the short focus lens 19 has, for example, a focal length of 4 to 8 mm and a magnification of 20 to 40.
Double microscope objectives are used and are configured as single lenses or compound lenses. here,
The short focus lens 19 is fixed so as to coincide with the optical axis O ₁ -O ₁ through which the holes 13A and 16A of the first and second centering pinholes 13 and 16 pass, and Each hole 1 is rotated by rotational movement.
The laser light that has passed through 3A and 16A can pass through the optical axis of the short focus lens 19.

Further, reference numeral 20 denotes a filtering pinhole attachment tube screwed onto the outer circumferential side of the lens attachment tube 18 at one end, and the other end of the attachment tube 20 is an enlarged diameter portion 20A. Reference numeral 21 denotes a ring-shaped filter ring pinhole holder mounted in the enlarged diameter portion 20A of the filter ring pinhole mounting tube 20; A filtering pinhole having a hole 22A is attached to the holder 21, and 23 indicates a pinhole holding ring screwed onto the pinhole holder 21 in order to fix the pinhole 22. Then, hole 2 of the pinhole 22
2A has a hole diameter of 10 to 25 μm in order to transmit only the central maximum energy part of the laser light focused on the condensing point of the short focus lens 19 (the hole diameter is determined by Garcian 1/e ₂ of the maximum irradiance is desirable so that the energy distribution of the beam is obtained). Moreover, the pinhole 22
The hole 22A is fixedly attached so as to be located at the condensing point (focal point) of the short focal length lens 19 and on the optical axis O ₁ -O ₁ . For this purpose, the pinhole 22 is fitted into the stepped portion 21A of the pinhole holder 21, the pinhole 22 is fixed with the pinhole holding ring 23, and after this assembly, the pinhole holder 21 is expanded into the pinhole mounting tube 20. The pinhole holder 21 is bonded so as to fit into the diameter portion 20A and maintain the above-described positional relationship.

Furthermore, 24 is a mounting shaft, 25 is a flat plate as a fixed member screwed onto the upper end of the mounting shaft 25 and having approximately the same axial length as the main cylinder 11;
Support rings 6 and 27 are fastened to both axial ends of the flat plate 25 via mounting bolts 28 and 28, and each of the support rings 26 and 27 is larger than the main cylinder 11 so as to surround the main cylinder 11. It is formed in diameter. 2
Reference numerals 9 and 30 indicate three-point adjustment screws that are screwed in and out of each support ring 26 and 27 at 120° intervals in order to support the main cylinder 11 at three points. , the main cylinder 11 can be adjusted to be rotatable in elevation and elevation.

Although the present embodiment is configured as described above, the adjustment operation will be described next.

First, there is only one correct positional relationship between the short focus lens 19 and the filtering pinhole 22, so the hole 22A of the pinhole 22 should be at the focal position when the laser beam is incident on the lens 19. , these short focal length lenses 19 and pinholes 22 are three-dimensionally fixed in advance so that their optical axes coincide. Furthermore, when the laser light that has entered through the first and second centering pinholes 13 and 16 passes through the short focal length lens 19 and is condensed, the convergence point is the hole of the filtering pinhole 22. Adjust the pinhole fixing screws 14 and 17 so that the optical axis of the first and second centering pinholes 13 and 16 and the optical axis of the filtering pinhole 22 are at the position 22A. , single optical axis O ₁
- Adjust in advance so that it is above ₁ .

Therefore, the laser beam emitted from the laser generator is filtered through the hole 22A of the filtering pinhole 22.
In order to focus the laser beam on the first and second
Hole 13 for centering pinhole 13, 16
What is necessary is to match the optical axis O ₁ -O ₁ passing through A and 16A.

For this purpose, a laser beam is generated from a laser generator, one of the three-point adjustment screws 29 is rotated and adjusted as appropriate, and the center of the laser beam passes through the hole 13A of the first centering pinhole 13. Observe. This can be easily seen if the hole 13A is viewed diagonally from behind because when the laser beam passes through, the bright area at the center disappears and the center becomes dark. Moreover, the hole 13A is formed with a relatively large diameter of 1 to 2 mm, and the beam diameter of the laser beam is 0.6 to 2 mm.
It is sufficiently large compared to 1.0 mm (in the case of He-He), so it can be easily seen.

Next, adjust the rotation of the other three-point adjustment screw 30 as appropriate to check whether the laser beam that has passed through the first centering pinhole 13 has passed through the hole 16A of the second centering pinhole 16. This is visually checked through each observation hole 11C of the main cylinder 11, and the positioning as a spatial filter is completed when the bright area in the center passes through, as described above. In the case of the embodiment, since the first centering pinhole 13 and the three-point adjustment screw 29 are slightly offset in the axial direction, when the other three-point adjustment screw 30 is rotated, the pinhole The optical axis shifts slightly on the 13 side, but
This is not a substantial error. In this case, it goes without saying that the offset may be configured to be zero.

Furthermore, a screen is finally placed in front of the filtering pinhole 22, and the three-point adjustment screws 29 and 30 are finely adjusted as necessary.

In this example, the hole diameter is 1 to 2 mm.
It is sufficient to center the laser beam with a beam diameter of 0.6 to 1.0 mm at two points using the centering pinholes 13 and 16. It is much easier to operate than the original. Furthermore, the first
Since the adjustment of the spatial filter is completed only by the centering operation for the second centering pinholes 13 and 16, the operation of driving the pinhole to the condensing point of the short focal length lens is not required as in the conventional technology. is not required, and even beginners can make adjustments in a short time.

In the embodiment, the lens mounting tube 18 and the filtering pinhole mounting tube 21 are formed separately, but they may be formed as a single mounting tube. It is sufficient that the pinhole 22 can be attached in a predetermined arrangement relationship, and is configured as a lens/pinhole attachment tube.

In addition, although it has been described that the lens/pinhole mounting tube is formed separately from the main tube 11 and is fixed to the main tube 11, the short focus lens 19, This is to make the filter ring pinhole 22 replaceable.
The main cylinder 11 and the mounting cylinder may be formed integrally.

[Effects of the Invention] The spatial filter according to the present invention is as described in detail above, and the main cylinder is provided with first and second centering pinholes so that the optical axes coincide,
A short focal length lens is provided on the lens/pinhole mounting tube so as to coincide with the optical axis of the first and second centering pinholes, and a filtering pinhole is provided at the focal point of the lens, and a filtering pinhole is provided at the focal point of the lens. , the second support ring is provided with first and second adjustment screws to support and adjust the main cylinder so that it can be rotated up and down. All you need to do is adjust the main tube so that the incident parallel light passes through each of the first and second centering pinholes, and the adjustment operation of the main tube is done by adjusting the centering for the beam diameter of the incident parallel light. This makes it possible to make highly accurate adjustments even if the hole diameters of the first and second centering pinholes are relatively large. Even beginners can make adjustments in a short time, and the centering operation is extremely easy. It becomes easy.

[Brief explanation of the drawing]

FIG. 1 is a vertical sectional view of the spatial filter according to this embodiment, FIG. 2 is a right side view in FIG. 1, and FIG.
The figure is an explanatory diagram showing a conventional spatial filter and its adjustment method. 11... Main cylinder, 12, 15... Centering pinhole holder, 13, 16... Centering pinhole, 13A, 16A... Hole, 14, 17...
Pinhole fixing screw, 18... Lens mounting tube, 1
9... Short focus lens, 20... Pinhole mounting tube for filtering, 21... Pinhole holder for filtering, 22... Pinhole for filtering, 22A... Hole, 23... Pinhole holding ring, 25... Flat plate, 26, 27... Support ring, 29, 30... 3-point adjustment screw.

Claims (1)

[Claims] 1. A main cylinder having a desired axial dimension, and first and second cores each having a relatively large hole diameter and provided at one axial end and the other end of the main cylinder so that their optical axes coincide with each other. a pinhole for ejection; a lens/pinhole mounting tube that is formed integrally with or separate from the main barrel and has one end fixed to the other end of the main barrel; and the other end of the lens/pinhole mounting tube. said first,
a short focus lens fixedly provided so as to coincide with the optical axis of the second centering pinhole; and a short focus lens located at the other end of the lens/pinhole mounting tube; A filtering pinhole fixedly provided at a light focusing position, and first and second supports attached to a fixing member so as to surround one axial end side and the other end side of the main cylinder. a first adjustment ring provided on the first and second adjustment rings for supporting the main cylinder with respect to the first and second support rings and adjusting the main cylinder so that the main cylinder can be rotated up and down. , and a second adjustment screw, the main cylinder is adjusted by the first and second adjustment screws so that parallel light incident from the outside passes through the first and second centering pinholes. A spatial filter configured as follows.