JPH0334771Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention constitutes a holographic optical system as an optical device that is small, lightweight, and has excellent stability and reliability.

For example, holographic optical devices have a wide range of applications. For example, deformation of an object can be determined by techniques such as double exposure holography and real-time holography.

For this purpose, materials that can be used for real-time recording, such as
Using BSO elements and BGO elements as image recording materials,
A hologram is created by making object light, which is light reflected from an object, and reference light enter a recording material at a certain angle.

The deformation measurement method using holography is extremely accurate and makes it possible to detect even minute deformations.

Holographic technology involves using a laser device and reflecting the light from the laser in a suitable direction.
Mirrors and various lenses to guide you to the position,
Requires recording materials.

Moreover, these instruments must be fixed so that their relative spacing and orientation remain strictly unchanged. Even if there is a displacement or vibration of the same degree as the wavelength of light,
Unable to create holograms properly.

Conventionally, holographic optical devices have been constructed using a magnetic stand or the like on a heavy and large iron surface plate. onto the iron surface plate,
Place the laser, and fix the lens, mirror, recording material, etc. on the surface plate using a magnetic stand.
The surface plate is elastically supported by tires, springs, etc., and blocks vibrations and shock effects from the surroundings. Instead of using magnetic stands one-on-one for each device, there are some devices in which lenses, prisms, etc. are housed in a box and this is fixed on a surface plate.

In any case, it had to be built on a heavy and large surface plate weighing about 100 kg.

All of these holographic optical devices are extremely large optical devices, and are not yet practical due to their weight and size. This is no more than a laboratory experiment.

Furthermore, since the individual optical components are arranged discretely, there are still concerns about vibration resistance. In addition, there is a possibility of spatial displacement due to carelessness, which may affect the stability of the optical system.
There was a problem with reliability.

The present invention aims to solve the problems of the conventional holographic technology.

In the optical system of the present invention, lenses, mirrors, etc. are made of small glass blocks, which are laminated together to form a block shape, and such blocks and other optical components are pre-photographed into corresponding positions to create recesses. It is fitted and adhered to a substrate that has been formed on it, and the whole is molded with a transparent material.

Hereinafter, the structure, operation, and effects of the present invention will be explained with reference to drawings showing embodiments.

FIG. 1 is a perspective view of an optical device according to an embodiment of the present invention, with the mold section removed, and FIG. 2 is a corresponding structural diagram of the optical device of FIG. 1.

These are optical devices for measuring deformation by a double exposure holography method using a Bi ₁₂ SiO ₂₀ element (BOS element) as a recording material, and the configuration shown in FIG. 2 is well known. Separate lasers with different wavelengths are used for writing and reading. For example, an argon laser is used for writing, and a helium neon laser is used for reading.

The double exposure holographic diagram of FIG. 2 is well known, but will be explained first.

The writing light (a beam) emitted from the writing laser 1 passes through the single mode fiber F1. The beam is expanded at the end to form a luminous flux with a certain degree of spread. This light beam is reflected by the first mirror M1, becomes a spread b light beam, and enters the half mirror HM.

The half mirror HM divides the b light beam into two.
The reflected light beam c illuminates the measurement object O. The measurement object O may be an object of any shape. Object light reflected from measurement object O (d light flux)
carries three-dimensional information regarding the external shape of the object to be measured. The d light flux passes through the half mirror FM, passes through the dichroic mirror DM, and enters the recording material R at right angles.

The dichroic mirror DM is a mirror having selective reflection properties, and transmits the light from the writing laser L1, but reflects the light from the reading laser L2.

The recording material R is selected to have real-time characteristics. For example, a recording material in which a DC voltage is applied to the single crystal of a BOS element (Bi ₁₂ SiO ₂₀ ) or a BGO element (Bi ₁₂ GeO ₂₀ ) is used, and unlike a photographic plate, there is no need to develop it, and it can be read out immediately after writing. be able to.

On the other hand, the e light flux that passed through the half mirror HM is
It is reflected by the second mirror M2 and becomes an f light flux. The f light flux functions as a reference light.

The object light (d light flux) and the reference light (f light flux) enter the recording material R at a constant angle. Since the light of the writing laser L1 is coherent light, interference fringes corresponding to the measurement object O are generated in the recording material R. Unlike photographic plates, interference fringes appear as a shift in the distribution of electron clouds.

This is how you can write.

Regarding the initial state of the measurement object O, the recording material R
Make a hologram. Then, the writing operation is performed again while maintaining exactly the same arrangement in the post-transformation state. By performing the exposure twice, the holograms of the measurement object O before and after deformation are recorded in the recording material R in a double manner.

Reading is performed as follows.

The reading laser L2 uses a laser with a longer wavelength than the writing laser, for example, a He-Ne laser. The readout g light flux passes through the single mode fiber F2, has its beam diameter expanded, and then enters the recording material R from the back side. In other words, the light beam is made to enter the recording material R in an almost opposite direction from the extension line of the reference light beam f.

Then, the readout light becomes an h light flux, travels in the opposite direction to the d light flux which is the original object light, and forms its real image at the position where the measurement object O is located.

However, the h luminous flux is reflected by the dichroic mirror DM on the way to become the i luminous flux, which is further reflected by the third mirror M3 and transferred to the image fiber F.
It becomes j light flux passing through 3. j Luminous flux is a TV camera
Observed in TG.

The light beam j is a reproduction light carrying a double real image of the measurement object O before and after deformation. If a real image has a deformed portion, interference fringes will occur there with a density corresponding to the amount of deformation. By making these interference fringes appear on the screen of the television camera TG, the position and amount of deformation can be directly determined. Processing of the image of the measurement object O after it is captured by the television camera TG is optional.
Instead of directly observing with the naked eye, the interference fringe density may be counted and the amount of deformation may be automatically calculated.

The above configuration is well known.

In the present invention, mirrors, half mirrors, dichroic mirrors, recording materials, etc. are not assembled as discrete components, but prism-shaped glass blocks with vapor-deposited mirror surfaces are glued together to form blocks that are easy to handle. In addition, this block and other necessary lenses, mirrors, etc. will be glued onto a single board, and in order to ensure accurate positioning, recesses are pre-formed on the board at the positions where these flock members should be fixed. I'll keep it. Furthermore, the entire structure is molded with a transparent material, increasing the stability of the optical system.

FIG. 1 is a perspective view of the optical device of the present invention, with the mold section removed;
It is constructed on a thin substrate 1 made of glass, metal, ceramic, etc., which is not wide, large, or heavy, but light and narrow.

FIG. 3 is a perspective view of the substrate 1 only. Recesses 2, 3, 4 are provided in the flat surface. The recess 2 has such a shape and size that the bottom surface of the composite block 5 fits exactly therein. The bottom of the mirror block 6 fits into the recess 3. The bottom of the glass block 7 fits into the recess 4.

In this way, recesses are made in advance for all the block members to be fixed to the substrate 1.

To provide the recesses 2, 3, and 4, for example, a photoetching method can be used. If the substrate is made of glass or metal, the recesses can be precisely formed using the photoetching method.

However, in the present invention, the method of forming the recess and the depth of the recess are arbitrary. It is also possible to machine the recesses by mechanical methods. Further, the substrate can be made of ceramic, but in this case, the recesses can be formed in the material in advance and then fired.

In FIG. 1, a writing light transmission single mode fiber F1 that transmits the light of the writing laser L1 is connected to a rod lens 8. As shown in FIG. The rod lens 8 is a cylindrical lens with a gradient index of refraction, and has the function of expanding the narrow beam of the laser L1 and making it into a parallel beam with a larger diameter.

A readout light transmission single mode fiber F2 connected to the readout laser L2 is connected to a rod lens 9. A glass block 7 is fixed onto the substrate 1 to support the rod lens 9.

An image fiber F3 for transmitting reproduction light following the television camera TC is connected to a rod lens 10. Rod lens 10 is image fiber F3
A real image of the object O to be measured is focused on the end face of the object O.

The structure of the composite block 5 is made by using suitable shaped glass blocks as they are, or by forming a mirror surface on the boundary surface by metal vapor deposition, and then bonding them together with an adhesive.

A rod lens 8 for introducing writing light is bonded to an end face of a rectangular parallelepiped transparent first elementary block 11. The writing light flux a passes through the first elementary block 11 in the longitudinal direction and passes through the triangular prism-shaped second elementary block 12.
to go into. Third elementary block 13 and second elementary block 1
2 is a triangular prism whose base is an isosceles right triangle,
The diagonal slope is the first mirror M1x. That is, metal is deposited on the diagonal slope of either the second or third elementary blocks 12, 13 to form a mirror, and this is bonded together with an epoxy resin adhesive, balsam, or other suitable adhesive.

Immediately below the second elementary block 12 are a fifth elementary block 15 and a sixth elementary block 16, which are similarly shaped like a triangular prism.
are bonded together with the first mirror M1y sandwiched therebetween. The mirrors M1x and M1y are in twisted positions with respect to each other, and together they correspond to the first mirror M1 in FIG.

The fourth elementary block 14 is a rectangular parallelepiped glass block having the same shape and size as the first elementary block. The upper surface is glued to the first elementary block 11, and the end surface is
A fifth elementary block 15 and a sixth elementary block 16 are bonded together. The fourth elementary block is only for connecting these elementary blocks. It does not transmit light. Such elementary blocks having only connection functions are also required to create a unified composite block 5.

The side surface of the seventh elementary block 17 is attached to the side surface of the fifth elementary block 5. The seventh elementary block 17 and the eighth elementary block 18 have a triangular prism shape, and are combined to form a rectangular parallelepiped. The diagonal slopes are still metal-deposited, but they are half mirrors HM instead of total reflection mirrors.

One of the two isoplanes of the eighth elementary block 18 constitutes the outer wall surface of the composite block 5, and on the extension line of the normal line erected thereto (parallel to the light flux e), the mirror block 6 is spatially It exists separately from the composite block 5.

The extension line of the normal to the plane of the seventh elementary block 17 (c
The measurement object O is located parallel to the light beam).

The light beam b becomes two light beams that are divided perpendicularly by the half mirror HM, and the light beam c irradiates the object O to be measured. The light beam e enters the second mirror M2 of the mirror block 6. d reflected from the measurement object O
The light flux (object light) returns to the seventh elementary block 17 again, this time it travels straight through the half mirror HM, and enters the ninth elementary block 19.

The ninth elementary block 19 is a rectangular parallelepiped, and has the same shape and size as the first elementary block 11 and the fourth elementary block 14. The d light flux, which is the object light, passes through the ninth elementary block 19 in the longitudinal direction.

The 10th elementary block 20 is a rectangular parallelepiped glass block pasted on top of the 9th elementary block 19, and although no light is introduced into it, it is pasted to make the structure of the block stable and robust.

An eleventh element block 21 is attached to the end face of the ninth element block 19. 11th elementary block 21,
The twelfth elementary block 22 has a triangular prism shape, and dichroic mirrors DM are provided on diagonal slopes by vapor deposition. A recording material R having real-time characteristics is pasted on the end face of the twelfth elementary block 22. This uses, for example, a BSO element or a BGO element.

Top surface of 12th elementary block 22, 10th elementary block 2
On the end face of 0, there is a triangular prism-shaped 13th elementary block 23,
A fourteenth elementary block 24 is pasted.

A third mirror M3 is provided on the diagonal slope between the 13th element block 23 and the 14th element block 24. The rod lens 10 is bonded to the end face of the fourteenth element block 24.

The reference light (f light flux) and the readout light (g light flux) enter the recording material R from opposite sides, but do not necessarily lie along the same straight line. This is because the wavelengths are different. The angle of incidence must be set so as to satisfy the Bragg condition.

In other words, the ratio of the sine of the angle between the normal to the incident surface of the recording material and the light beam is made equal to the ratio of the wavelength of the light.

Although this is a fairly severe condition, recording material R, mirror block M2, and glass block 7 are
Since the recesses 2, 3, and 4 are provided in advance on the board 1 for positioning, there is no need for fine adjustment after installation.

In this way, the composite glass block 5, the mirror block 6, and the glass block 7 are placed on the substrate 1.
After attaching it, the whole thing is molded with a transparent material.

FIG. 4 is a perspective view of the optical device of the present invention in such a state.

In this example, the optical device shown in FIG. 1 is housed in a box-shaped package 30, which is further filled with a transparent liquid molding material and solidified.

A window 31 is opened in the front of the package 30, and the measurement object O is placed in front of the window 31.

Substrate 1, composite block 5, mirror block 6,
Since the glass block 7 and the like are located in the mold section 32, there is no air or the like between these members, and they are connected by a transparent solid layer.

Although the single mode fibers F1, F2, image fiber F3, etc. can be taken out individually from the package, in this example, they are taken out all at once from the connector section 33.

The mold material is preferably transparent, has a thermal expansion coefficient close to that of the substrate or glass, and has a refractive index close to that of glass.

The purpose of molding is to physically connect these optical blocks firmly and to prevent light from being reflected on the surfaces of the glass blocks.

For example, the glass block is BK7 with a refractive index of 1.51.
(porosilicate crown gas), and the molding material may be, for example, PMMA (polymethyl methacrylate) having a refractive index of 1.49.

The optical device of the present invention can be used as shown in FIG. 4, but it may also be completed with a lid.

The package 30 and the lid may be transparent or non-transparent, and may be made of metal, plastic, glass, or any other material.

However, putting it in a package is not necessarily required for the present invention. Put it in a suitable mold, mold it, and after solidifying, take it out from the mold,
It can also be used as is.

The mirrors M1, . . . can be made by vapor depositing metal such as aluminum.

Dichroitsch mirror DM is TiO ₂ , GeO ₂ ,
It is made by vapor depositing oxides such as SiO.

The writing laser L1 is, for example, an Ar laser,
For example, a He-Ne laser can be used as the readout laser L2.

In this explanation, an example was given in which the deformation of an object is measured using the double exposure method, but a measurement system using the real-time holography method can also be constructed according to the present invention.

This invention is completely different from conventional holographic optical devices, which were constructed by placing optical equipment on a surface plate made of iron.In contrast, each optical element is made of glass blocks, which are then bonded together to form a composite block. If there is a composite block and a block that cannot be combined with the composite block, each block is placed on a substrate with appropriate recesses in advance, and then the entire block is molded, resulting in the following effects.

First, it is lightweight and small.

The approximate dimensions of the composite block 5 are approximately 10 mm x 10 mm x 50 mm. It is small and light, making it convenient to handle, opening up a wide range of uses.
It can be used for measuring deformation of IC substrates, measuring film thickness during passivation, etc.

The recess can be formed by chemical etching, plasma etching, ion beam etching, etc. in addition to photo etching.

In this example, there are three recesses, but the number of recesses is arbitrary. It is sufficient to provide the same number of recesses as the number of optical elements (glass blocks) spaced apart from each other.

Furthermore, the present invention has the advantage of being highly reliable and stable since each optical block is pasted onto the substrate and then molded to solidify it.

If the refractive index of the mold material is close to the refractive index of the glass, it has the advantage of reducing reflection losses at the mold-glass interface.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an optical device according to an embodiment of the present invention, with the mold section removed. FIG. 2 is a corresponding configuration diagram of the optical device shown in FIG. 1. FIG. 3 is a perspective view of only the board. FIG. 4 is a perspective view of the optical device placed in a package and molded. DESCRIPTION OF SYMBOLS 1... Substrate, 2, 3, 4... Concave portion, 5... Composite block, 6... Mirror block, 7... Glass block, 8, 9, 10... Rod lens, 11
~24... Elementary lens, L1... Laser for writing, L2... Laser for reading, F1... Single mode fiber, F2... Single mode fiber, F3... Image fiber, M1-M3...
...Mirror, HM...Half mirror, DM...Dichroic mirror, R...Recording material, O...Measurement object, TC...TV camera, a to j...Light flux,
d...Object light, f...Reference light, g...Reading light, 30...Package, 31...Window, 32...
Mold part.

Claims (1)

[Scope of utility model registration request] A raw glass block, a raw glass block whose predetermined surface is coated with a thin film having a predetermined wavelength transmission characteristic, a composite block formed by mutually adhering a lens and a recording material having real-time characteristics, and a glass separated from the composite block. A block, a substrate that fixes each block body in a recess provided in advance, a box-shaped package that houses the substrate, a connector section provided on the package, and a single mode fiber that connects the connector section and the plain glass block. and an image fiber, and the entire block is molded with a transparent material having a refractive index close to that of glass so that there is no air inside, and the composite block and glass block constitute a holographic optical system. When the writing light enters from the connector, the object light is taken out from the window provided in the package, reflected by the object to be measured, and then returned to the inside of the package through the window, and the reference light is transmitted to the glass block, mold, etc. inside the package. An optical device characterized in that the light passes only through a recording material, and when read light is input, an image written on the recording material is taken out to the outside through an image fiber.