JPH11119039A - Manufacture of optical plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical plate including columnar structures which each have the refractive index larger in itself than at its border by filling a removed part area so that the core area refractive index is larger than the cladding area refractive index. SOLUTION: A columnar structure forming the core area 64 is extended substantially from a light entrance surface 30 to a light exit surface 32. At the time of use, light enters the core area 64 normally from the light entrance surface 30, travels in the core area 64, and exits normally from the light exit 32. The core area 64 has the larger refractive index enough to internally reflect the light entering the core area 64 than the cladding area 66. Namely, the refractive index of the glass, etc., in the cladding area 66 is made smaller than that of the core area 64 to cause total internal reflection in the core area 64, and an etching part is filled for the purpose.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to fiber optic faceplates, and more particularly, to a photoform glass that is etched and the etched portion is filled with a fused low refractive index glass, plastic or colored matrix material to form an optical fiber faceplate. A method for producing a fiber faceplate equivalent.

[0002]

2. Description of the Related Art An optical fiber face plate (FOF)
P) is disclosed in U.S. Patent No. 5,44, filed March 21, 1994 by Silverstein et al.
It is useful for manufacturing a liquid crystal display (LCD) as disclosed in US Pat. No. 2,467. U.S. Pat. No. 5,442,467 discloses a backlight source, a back diffusion layer, a back polarizer, a back glass layer with an addressing element and an indium tin oxide (ITO) transparent pixel electrode. LC layer and LC (liquid crystal)
An LC cell including a front FOFP as a front containing element of the LC cell disposed in direct contact with the upper surface of the layer;
A direct-view back-illuminated LCD device comprising a mosaic array of color-absorbing filters stacked on the front of an OFP or placed on a separate but adjacent substrate, and a front polarizer or analyzer is disclosed. . Alternatively, the front polarizer or analyzer is composed of a thin film material,
It may be arranged between the upper surface or the light exit surface of the C layer and the lower surface or the light incident surface of the FOFP.

[0003] FOFPs comprise an array of optical fibers that are melted together with a gap cladding material and then cut and polished to a desired thickness to form a plate. Generating FOFPs with different optical properties is a well-known technique. The optical fiber is designed to transmit the totally internally reflected light incident at the designed input or allowable angle, and to reject or absorb the light incident at a larger angle. Light incident on the fiber from the entrance surface of the FOFP has a high numerical aperture (NA) F
Collected over a large allowable angle θ _max IN using coupling with OFP and / or low index (eg, air) boundaries. Light exiting the optical fiber at the exit face of the FOFP is made to diffuse or exit over a relatively large angle θ _max OUT, again using final coupling with high NA and / or low index boundaries. FOFPs with low NA and / or bonding with relatively high index materials (eg, plastic, polyimide or optical glass)
The light emission angle θ _max OUT of the exit surface of the FOFP and the FOFP
The light incident permissible angle θ _max IN at the entrance surface of the FP is limited.

[0004] These relationships are shown in FIG. 1 for a typical optical fiber 10. The optical fiber 1 within the receiving cone 20 defined by the angle θ _max measured from the reference line N
The light beam 16 that has entered the optical fiber 10
In the optical fiber 10, the light is totally internally reflected and propagates in the direction in which the optical fiber 10 extends without essentially causing any loss. The reference line N corresponds to the entrance surface 30 and the exit surface 32 of the optical fiber 10.
Perpendicular to If the relative index of refraction of the material surrounding the optical fiber 10 at the surface (N ₀ ) of the entrance face 30 and the exit face 32 is the same, the light beam 16 will emit light at the same angle as incident, here θ _max . Exit fiber 10.
The light beam 18 entering the optical fiber 10 from outside the light receiving cone 20 defined by the angle θ _max is not completely guided along the extension direction of the optical fiber 10,
0 leaks into the adjacent cladding material 14.
That is, light beam 16 is a guided light beam, while light beam 18 is a non-guided light beam. Unguided or partially guided light beam is cladding material 1
4 and into the fiber optic bundle or other fibers in the fused faceplate. However, unguided or partially guided light beams also typically leak from these fibers and continue to traverse the fiber bundle or faceplate.

FIGS. 2 and 3 show the effect of changing the numerical aperture of the optical fiber 10. FIG. FIG. 2 shows an optical fiber 10 having a small numerical aperture and a correspondingly small light receiving cone 20. FIG. 3 shows an optical fiber 10 having a large numerical aperture and a correspondingly large light receiving cone 20. That is, as the numerical aperture of the fiber 10 increases, θ _max at the entrance surface 30 and the exit surface 32 increases.

Normally, the light entering the optical fiber 10 is as shown in FIG.
As shown in FIG. 7, the optical fiber 10 rotates around the central axis of the optical fiber 10 as it propagates along the extension direction of the optical fiber 10. In this example, the central axis of the optical fiber 10 has an angle θ
_It coincides with the reference line N used to measure _max . Therefore, light that enters the fiber incident surface at a predetermined angle from the reference line N exits the optical fiber 10 at the same angle, but the azimuthal position is rotated. This rotation depends on the number of reflections in the optical fiber 10 and the inner surface of the fiber. Oblique rays usually undergo more rotation than meridian rays. For applying FOFP to LCD,
Most of the light incident on the fiber is oblique light.

In FIG. 4, rays 24 and 26
Is the entrance surface 3 at the angle θ _max measured with respect to the reference line N.
It looks as if it is incident on the optical fiber 10 from zero. Ray 24 is parallel to ray 26 and these rays are
Enter the optical fiber from another point of zero. Each ray 24,
When the beam 26 reaches the exit surface 32 of the optical fiber 10, each ray 24, 26 is at an angle θ _max ,
Has undergone an azimuthal rotation of an angle φ about the central axis of.

As described above, in the fused optical fiber bundle and the face plate, both the guide and non-guide rays undergo azimuthal rotation. As shown in FIG. 4, as a result of this rotation, the optical fiber 10 sets the azimuthal position of all the incident light incident at a predetermined inclination angle to the solid angle whose output is twice the incident angle on average. A hollow exit cone 22 having the same. In FIG. 4, the illustrated incident rays 24, 26 are incident on the optical fiber 10 at an angle θ _max and the solid angle of the hollow exit cone 22 is 2θ.
_max . Since the light emerging as hollow exit cone 22 is averaged for azimuth position, the transmitted light intensity is equal at all azimuth angles. This property of azimuthal averaging allows a FOFP to produce symmetric visual characteristics over a wide angle when combined with an LCD that has intrinsic anisotropy in brightness and contrast.

FIGS. 5 (a) and 5 (b) show a FOFP 28 consisting of an array of individual optical fibers that is melted with a gap cladding material and then cut and polished to a desired thickness to form a plate. . Core 12 and cladding material 14 can be seen on the surface of FOFP 28.

Therefore, the total internal reflection, the numerical aperture (NA) at the entrance surface and the exit surface can be controlled, the rotation direction can be averaged, and the target surface can be moved from the back surface of the plate to the front surface of the plate. All plates with a columnar structure in the direction of propagation of light are optical equivalents of FOFP.

[0011] Diffraction is the refraction from linear propagation that occurs when a light wave travels past some obstacle or boundary. The obstacle may be opaque, such as in the case of a knife edge or pinhole, or it may be the boundary between two transparent materials with different refractive indices. When light hits a boundary or obstacle, it is reflected, refracted, or diffracted and deviates from a straight path, so the intensity distribution of a light spot that is diffracted, when projected on a plane somewhat distant from the boundary, is due to the spread function or diffraction pattern Characterized. For light transmitted through an aperture, the degree of diffraction or angular refraction of the optical path is determined by the size and shape of the aperture and the wavelength of the light from the light source. The diffraction pattern at some distance from the aperture is additionally a function of the distance from the aperture to the viewing plane. Diffraction patterns at remote or distant points are commonly referred to as Fraunhoffer diffraction patterns. In optical systems where the circular aperture, which is typically comprised of a lens, an aperture, and a pupil, is constrained, the Fraunhofer diffraction pattern is often airy.
y) It is called a disk. The Airy disk resulting from light passing through a circular aperture is well described by a first-order Bessel function, with the central bright region being surrounded by a series of blurred rings of rapidly decreasing intensity. About 84% of the light intensity from the diffraction point source is contained within the first dark circle of the Airy disk. Thus, Airy disks characterize blurred toroids produced by diffraction limited optical systems.

As shown in FIG. 6, the FOFP is:
It consists of a fusion plate of optical fibers consisting of a core 12 and a gap cladding 14, which optical fibers constitute two different distributions of very small apertures. The inlet face 30 and the outlet face 32 of the core 12 can both be considered small circular openings. The cladding 14 at the inlet and outlet surfaces 30, 32 is somewhat irregular in shape and size. However, for purposes of discussion, cladding 14 has
In the following, a circular opening having a diameter estimated from the average diameter of 4 will be described. The guide beam 16 incident on the FOFP is diffracted according to the angular distribution of the optical path. The degree of diffraction, that is, the width of the angular distribution of the optical path is inversely proportional to the diameter of the aperture. Therefore, when the opening becomes smaller, the FOFP
The angle at which light propagation through is diffracted increases. Core 12
A much smaller cladding 14 diffracts the incident light to large angles. FIG. 6 shows the core 1 on the retina of the observer 34 at a fixed position somewhere from the FOFP.
2 shows a relative Fraunhofer diffraction pattern or Airy disk 38 resulting from the projection of the diffraction angle distribution of 2 and cladding 14. The angular spread caused by diffraction can be estimated from the following equation:

Q _diffr = 1.22 [(λ) (180)] /
[(D) (π)] Here, q _diffr = half angle (°) corresponding to the first dark circle of the Airy pattern D = diameter of circular aperture λ = wavelength of light

Referring to the above equations and assuming nominal diameters of core 12 and cladding 14 of 7 μm and 0.5 μm, respectively, for incident light of 550 nm, the first dark circle of Airy disk 38 The corresponding diffraction angle is expected to be about 5.49 ° at the core 12 opening and about 76.9 ° at the cladding 14 opening. For the on-axis illumination and on-axis vision of an LCD with a combined FOFP, the diffraction effects at the FOFP appear mainly as a slight decrease in display brightness. This is largely due to the small receiving cone of the eye and many photometric instruments.

[0015]

FOFP diffraction causes an irregular decrease in the on-axis contrast of the LCD coupled to it. By confirming this causal relationship, effective measures can be developed to reduce these observed reductions in on-axis LCD contrast. To describe this problem, the conventional twisted nematic (TN) or super twisted nematic (ST) described above
N) Consider the angle-dependent contrast performance of an LCD. The contrast ratio of such displays is very high when viewed on-axis (on-axis), but progressively decreases for off-axis observations and light propagation angles. The gradual decrease in contrast observed in this way is not isotropic for the reasons described above. At some extreme angles, the contrast of the display is actually reversed, producing a negative image. Such off-axis contrast reduction does not affect the high on-axis contrast performance of the display due to the small receiving cone of the eye or many photometric instruments. However,
When a FOFP is coupled to such an LCD, the FOFP
The on-axis contrast performance of the combined display is substantially reduced below the level achieved in the absence of the FOFP. Thus, improving the on-axis contrast performance of FOFP-coupled LCDs has significant benefits.

Since the light propagating at off-axis angles degrades the on-axis contrast performance of the LCD with the FOFP, the angular orientation is such that some of this light is coupled into the eye or into the small receiving cone of the measurement instrument. Must be changed. FIG. 7 shows a FOF generated from a source (ie, backlight) at an angle that is off-axis from reference line N.
Shows a guide ray 16 to the P input plane. Exit surface 32
In, the light is diffracted by the openings in the core 12 and the cladding 14 in an angular distribution with respect to the light propagation direction. Because the aperture of the core 12 is large, the diffraction angle is relatively small and does not diffract much light into the observer 34 or the receiving cone of the instrument. However, since the aperture of the cladding 14 is small, the angular distribution of the diffracted off-axis light is very large and a large amount of off-axis light is diffracted into the observer 34 or into a small receiving cone of the measurement instrument. Thus, LC
Off-axis light from D (and corresponding contrast reduction)
Is diffracted by the aperture in the FOFP cladding 14 into the observer 34 or into the small receiving cone of the instrument, resulting in a significant decrease in the on-axis contrast performance of the FOFP-coupled LCD.

The on-axis contrast performance of the FOFP-coupled LCD is shown in FIG.
It can be dramatically improved by masking the openings in the P cladding 14. This figure shows, together with a FOFP with a masked cladding 36, how such a mask prevents the aperture of the cladding 14 from diffracting off-axis light into the observer's visual cone. ing. The evaluation of the FOFP-coupled LCD with the masked cladding 36 was confirmed by the effect of this improvement, resulting in a dramatic improvement in the on-axis contrast performance of the FOFP-coupled LCD.

Because these essential optical properties can be realized within the limits of the material, an optical equivalent of FOFP is produced. The present application uses light-sensitive glass to create adjacent areas having different indices of refraction, resulting in a substrate comprising a plurality of cylindrical structures whose boundaries are defined by refractive index discontinuities, wherein the cylindrical structures A method is discussed in which the inner refractive index is greater than the cylindrical structure boundary and outer refractive index. In another embodiment, a substrate is obtained that includes a plurality of columnar structures whose boundaries are defined by a light blocking material.

Therefore, a main object of the present invention is to provide a cylindrical structure in which the refractive index is larger than the refractive index at the boundary of the cylindrical structure.
The goal is to create an optical plate whose boundaries include a plurality of cylindrical structures defined by a refractive index discontinuity.

Further advantages of the present invention will become clear from the description hereinafter.

[0021]

SUMMARY OF THE INVENTION Briefly and in accordance with the present invention, total internal reflection, controllable numerical aperture (NA) at the entrance and exit surfaces, averaging of rotational orientation and plate sizing are provided. A method is described for making an optical plate that has a columnar structure in the direction of light propagation that is capable of moving the target surface from the back to the front of the plate and that is the optical equivalent of a FOFP. These plates are made from a composition of photosensitive glass that has been etched into either a cylindrical or enclosed structure. If etched into the surrounding structure, the etched area
Filled with either low melting glass, epoxy or plastic, liquid, or light blocking material such as black synthetic material. If etched into a columnar structure, the etched area is filled with low melting glass, epoxy, liquid or plastic. The resulting plate includes a plurality of adjacent areas with different indices of refraction such that the index of refraction within the columnar structure is greater than the boundary of the columnar structure and the index of refraction outside the columnar structure. A substrate including a plurality of columnar structures defined by continuity is obtained.

While the invention will be described in conjunction with a preferred embodiment and its use, it will be understood that the invention is not intended to be limited to this embodiment or procedure. On the contrary, the intent is to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.

[0023]

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 9, a photosensitive (photoreactive) glass substrate 40 is shown. An important property of photosensitive glass is that it is sensitive to light that alters the properties of the glass, such as the etch rate of the glass in areas exposed to UV light. An example of such a glass is Peg-3 glass or Photofoam (Fotofor
m) glass (both from Hoya Corporat in Tokyo, Japan)
ion), which, upon exposure to light, changes the amorphous or amorphous structure into a crystalline structure. The etching rate of crystalline glass is about 50 times that of amorphous glass.

The glass substrate 40 is divided into two types of areas, a core area 64 and a cladding area 66. In order for the glass substrate 40 to function as a FOFP, the core area 64 needs to totally reflect all light incident thereon. For total internal reflection to occur within core area 64, the refractive index of core area 64 (n _core ) must be greater than the refractive index of cladding area 66 (n _clad ). The difference in the refractive index between the core area 64 and the cladding area 66 is 2
It is represented by the numerical aperture (NA), which is the square root of the difference between the squares of the two refractive indices, and is described by the following equation:

NA = [n ² _core −n ² _clad ] ^1/2 A fiber optic faceplate having a numerical aperture in the range of about 0.4 to 1.0 is suitable for use in various liquid crystal display applications. I have.

In order to cause a difference in the refractive index between the core area 64 and the cladding area 66, the glass substrate 4
0 is irradiated with parallel UV radiation 62 through a mask 60. A plan view of the mask 60 is shown in FIG. The mask 60 is divided into an opaque core non-irradiation area 68 and a transparent cladding illumination area 70. Parallel U
The V radiation 62 does not pass through the core non-irradiation area 68 of the mask 60, and therefore does not hit the glass substrate 40 in the core area 64. Therefore, the core area 64 is maintained as amorphous glass.

However, the collimated UV radiation 62 passes through the cladding illumination area 70 of the mask 60 and strikes the substrate 40 in the cladding area 66, changing the characteristics of the cladding area 66. In this example, the cladding area 66 is a crystalline glass having a higher etching rate than the amorphous glass in the core area 64.

Then, the glass substrate is placed in an etching bath, and the result is shown in FIG. The largest known etch rate difference is a 5% hydrofluoric acid solution (5%
HF), which results in a 50: 1 etch rate difference between the cladding area 66, which is a crystalline glass, and the amorphous glass, the core area 64. The glass substrate 40 is, as shown in FIG.
The cladding area 66 is immersed in an etchant bath for a period of time sufficient to partially etch and remove the cladding area 66 so as to produce a remaining portion 72 of the cladding area 66 and an etched portion 74 of the cladding area 66. The cladding area 66 is not completely etched away so that the remaining portion 72 of the cladding area 66 can serve as a structural support.

When the cladding area 66 is partially etched, the glass substrate 40
Etched portion 74 of cladding area 66 in 0
May be annealed to smooth the edges. The details of the annealing step vary depending on the type of the glass substrate 40 used. However, if PEG-3 glass available from Hoya is used, a suitable annealing step should be performed in four steps.

In the first stage, the glass substrate 40 is heated from room temperature to about 350 ± 50 ° C. for about 150 ± 50 per hour.
Heat at a rate of ° C. In the second stage, the glass substrate 40
Is heated from 350 ° C. to at least 590 ° C. at a rate of about 60 ± 20 ° C. per hour. The different heating rates are used to avoid problems due to internal stress caused by rapid heating of the glass.

Once the glass substrate 40 has been heated to about 590 ° C., in the third stage of the annealing step, the temperature is held constant for at least 45 minutes so that annealing occurs. After the glass substrate 40 has been annealed, it may be cooled to room temperature at a rate of about 150 ± 50 ° C. per hour in the next step.

After annealing and cooling, the etched portion 74 of the glass substrate 40 is filled with molten low refractive index glass, plastic, or light blocking material 76, as shown in FIG. Various materials can be used, such as plastic, epoxy, or low melting glass. If a black material is desired, a plastic having carbon black particles embedded therein can be used.

In another embodiment, as shown in FIG. 13, the etched portion 74 may be filled with a suitable low index liquid. However, in this case, it is necessary to add a thin glass or plastic liquid holding plate 84 in contact with the glass substrate 40 on the etched surface of the glass substrate to hold the liquid. If an opaque cladding opening is desired, the liquid holding plate may be coated with a thin layer of light blocking material 86 over the cladding area 66, thereby providing an opaque cladding as is known in the art. A locking opening is provided. FIG. 14 is a perspective view of the liquid holding plate 84 including the light blocking member 86 applied to one surface of the liquid holding plate 84. The core area 64 is not covered with the light blocking material 86. When the liquid holding plate 84 is assembled on the etched surface of the glass substrate 40, as shown in FIG. 13, the light blocking material 86 is attached to the outer surface of the assembly, as shown in FIG. Therefore, it is preferable not to face the etched surface of the glass substrate 40. If the light blocking material 86
The apparatus would work if the liquid holding plate 84 with the light blocking material 86 was assembled so that
Is preferably on the outer surface.

Most importantly, liquid, glass, plastic or light blocking material 76 in cladding area 66 so that total internal reflection occurs in core area 64.
Has a smaller refractive index than the core area 64. If the liquid, glass, plastic or light blocking material 76 in the cladding area 66 is a light blocking material such as a black matrix material, the FOFP
The additional benefit of improving the on-axis contrast performance of the combined LCD can also be obtained. Not all of the etched portion 74 of the cladding area 66 need be filled with light blocking material to obtain this benefit,
Only a small portion of the etched portion 74 need be filled, which is preferably the portion closest to the light exit surface of the completed device.

FIG. 15 (a), (b) or FIG.
(A) and (b) show the resulting product.
FIGS. 15A and 15B show a glass substrate 40 divided into a columnar structure forming a core area 64 and a surrounding material forming a cladding area 66. The cylindrical structure forming the core area 64 is substantially equivalent to the light entrance surface 30.
To the light exit surface 32. In use, light usually enters the core area from the light entrance surface 30 and is
4 and exits from the normal light exit surface 32. The core area 64 and the cladding area 66 have a refractive index such that the core area 64 has a greater refractive index than the cladding area 66 enough to internally reflect light that has entered the core area 64. . It should also be noted that the cladding area 66 has two parts. That is, the remaining portion 72 of the unetched source material that serves as a structural support and the low refractive index glass or plastic 76 used to fill the etched portion 74.

FIGS. 16A and 16B show the core area 64.
Is shown, and a glass substrate 40 divided into a columnar structure forming a cladding area and a surrounding material forming a cladding area 66 is shown. The columnar structure forming the core area 64 is substantially
It extends from the light entrance surface 30 to the light exit surface 32. In use, light usually enters the core area through the light entrance surface 30,
The light propagates in the core area 64 and exits from the normal light exit surface 32. Core area 64 and cladding area 66
Has a refractive index such that the core area 64 has a greater refractive index than the cladding area 66 enough to internally reflect light that has entered the core area 64.
Cladding area 66 is at least partially light blocking material, which is preferably at exit surface 32 to avoid off-axis light diffracting into the observer's visual cone. This improves the on-axis contrast performance of the FOFP-coupled LCD. It should also be noted that the cladding area 66 has two parts. That is, the remaining portion 72 of the unetched source material that serves as a structural support and the low refractive index glass or plastic 76 used to fill the etched portion 74.

A structure constructed as described above using the materials listed above has a core area 64 having a refractive index of about 1.5 if glass is used, and a refractive index of the cladding area 66. Is about 1.42 if trifluoroisopropyl methacrylate is used.
From these refractive indices, the numerical aperture NA = [n ² _core− n ² _clad ]
^1/2 = [1.5 ² -1.42 ² ] ^1/2 = 0.48. These examples are for illustration only, and any glass or plastic having an index of refraction between about 1.45 and about 1.12. May be used.

If a fluid and liquid holding plate 84 is used as shown in FIG. 13, a suitable liquid is water. If water having a refractive index of 1.33 is used, the numerical aperture NA = [n ² _core− n ² _clad ] ^1/2 = [1.5 ² −
1.33 ² ] ^1/2 = 0.69. Again, water is used for illustrative purposes only, and any fluid having an index of refraction between about 1.45 and about 1.12 may be used with photoform glass. Such fluids include dark or opaque fluids that have light blocking properties to the cladding area 66.

As shown in FIGS. 17-22, it is possible to perform the same process by etching the core area 64 instead of the cladding area 66 and obtain similar results. 17 to 22, the same reference numerals are shown, and the reference numerals are appended with an extension code "a" to indicate the equivalent structure.

Referring to FIG. 17, a photosensitive glass substrate 40a is shown. The glass substrate 40a is divided into two types of areas, a core area 64a and a cladding area 66a. Glass substrate 40a is FOFP
In order to function as, it is necessary for the core area 64a to totally internally reflect all light incident thereon. For total internal reflection to occur within core area 64a, the refractive index (n _core ) of core area 64a must be greater than the refractive index (n _clad ) of cladding area 66a.

The glass substrate 40 is irradiated with parallel UV radiation 62a through a mask 60a to cause a difference in the refractive index between the core area 64a and the cladding area 66a. A plan view of the mask 60a is shown in FIG. The mask 60a is divided into a transparent core illuminated area 78 and an opaque non-cladding non-illuminated area 80. The parallel UV radiation 62a does not pass through the non-cladding area 80 of the mask 60a, and thus does not strike the glass substrate 40a in the cladding area 66a. Therefore, the cladding area 66a is maintained as amorphous glass.

However, the parallel UV radiation 62a passes through the core irradiation area 78 of the mask 60a, hits the substrate 40a in the core area 64a, and changes the characteristics of the core area 64a. In this example, the core area 64a is a crystal glass having a higher etching rate than the amorphous glass in the cladding area 64a.

Then, the glass substrate was put into an etching bath, and the result is shown in FIG. The largest known etch rate difference is a 5% hydrofluoric acid solution (5%
HF), whereby the difference in etching rate between the cladding area 66a, which is amorphous glass, and the core area 64a, which is crystalline glass, is 50: 1.

As shown in FIG. 19, the glass substrate 40a is partially etched to remove the core area 64a so that the remaining portion 72a of the core area 64a and the etched portion 74a of the core area 64a are formed. For a sufficient time. Core area 6
4a is not completely etched away so that the remaining portion 72a of the core area 64a can serve as a structural support.

Once the core area 64a is partially etched, the glass substrate 40a is annealed to smooth the edges of the etched portion 74a of the core area 64a in the glass substrate 40a. The details of the annealing step vary depending on the type of the glass substrate 40a used. However, if the P available from Hoya
If EG-3 glass is used, a suitable annealing step should be performed in the four steps described above.

After annealing and cooling, the etched portion 74 of the core area 64a of the glass substrate 40a is
Is filled with molten low refractive index glass, epoxy or plastic 82 as shown in FIG. Various materials such as naphthalic methacrylate or vinyl carbazole can be used.

Alternatively, as shown in FIG. 21, the etched portion 74a may be filled with a suitable high index fluid such as cassia oil or carbon disulfide. However, in this case, a thin glass or plastic liquid holding plate 84 that contacts the glass substrate 40a on the etched surface of the glass substrate to hold the liquid.
a needs to be added. If an opaque cladding opening is desired, the liquid retaining plate may be coated with a thin layer of light blocking material over the cladding area 66a, thereby providing an opaque cladding as is known in the art. An opening is provided. The liquid holding plate 84a is the same as that shown in FIG. The core area 64a is not covered with the light blocking material 86a. When the liquid holding plate 84a is assembled on the etched surface of the glass substrate 40a as shown in FIG. 21, the light blocking material 86a is attached to the outer surface of the assembly as shown in FIG. Therefore, it is preferable not to face the etched surface of the glass substrate 40a. If the light blocking material 86a is the glass substrate 4
Optical block material 86 so as to face the etched surface 0a.
The device will still function when the liquid holding plate 84a with a is assembled, but the light blocking material 86a is preferably on the outer surface.

Most importantly, the glass or plastic in the core area 64a is removed from the cladding area 66a so that total internal reflection occurs in the core area 64a.
Has a higher refractive index.

FIGS. 22 (a) and (b) show the resulting product. FIGS. 22A and 22B show a glass substrate 40 divided into a columnar structure forming a core area 64a and a surrounding material forming a cladding area 66a.
a. The columnar structure forming the core area 64a extends substantially from the light entrance surface 30 to the light exit surface 32. In use, light enters the core area from the normal light entrance surface 30, propagates in the core area 64a, and exits from the normal light exit surface 32. The core area 64a and the cladding area 66a have a refractive index such that the core area 64a has a greater refractive index than the cladding area 66a enough to internally reflect light that has entered the core area 64a. . It should also be noted that the core area 64a has two parts. That is, the remaining portion 72a of the unetched original material serving as a structural support portion and the etched portion 74a
Is the high refractive index glass, epoxy or plastic 82 used to fill the substrate.

The structure constructed as described above using the materials listed above has a refractive index of the core area 64a of about 1.68 if naphthal methacrylate is used.
3, the refractive index of the cladding area 66a is about 1.5 if photoform glass is used. From these refractive indices, the numerical aperture NA = [n ² _core −n ² _c
lad ] ^1/2 = [1.64 ² -1.5 ² ] ^1/2 = 0.66.
However, these examples are for illustration only, and any suitable clear glass or plastic having an index of refraction between about 1.55 and about 1.80 will provide a suitable numerical aperture. It may be used together with a photoform glass.

A suitable liquid is cassia oil if a fluid and liquid holding plate is used, as shown in FIG. If cassia oil having a refractive index of 1.7 is used, the numerical aperture NA = n ² _core− n ² _clad ] ^1/2 =
[1.7 ² -1.5 ² ] ^1/2 = 0.8. Here, cassia oil is used only for the purpose of explanation, and about 1.55
Any fluid having a refractive index between 間 の 1.80 may be used with the photoform glass. This allows
An appropriate numerical aperture can be obtained.

[0052]

As described above, according to the present invention,
A substrate can be produced that includes a plurality of columnar structures, where the index of refraction within the columnar structure is greater than the index of refraction at the boundaries of the columnar structures, the boundaries being defined by refractive index discontinuities.

[Brief description of the drawings]

FIG. 1 is a side view of an optical fiber depicting a permissible cone of light incident on the optical fiber and guide and non-guide rays.

FIG. 2 is a side view of an optical fiber depicting a narrow tolerance cone.

FIG. 3 is a side view of an optical fiber depicting a wide allowable cone.

FIG. 4 is a side view of the optical fiber depicting the azimuth average.

FIG. 5 is a plan view of a conventional FOFP.

FIG. 6 is a diagram illustrating diffraction of light on an optical fiber faceplate with respect to off-axis light incidence.

FIG. 7 illustrates the reduction in contrast with respect to diffraction on a fiber optic faceplate having a transparent cladding aperture.

FIG. 8 illustrates a reduction in contrast loss for diffraction on a fiber optic faceplate with opaque cladding.

FIG. 9 is a side view of a plate of photosensitive glass in a first manufacturing step for making an optical equivalent of a FOFP according to the present invention.

FIG. 10 is a plan view of a mask used in the manufacturing process shown in FIG.

FIG. 11 is a side view of a plate of photosensitive glass in a second manufacturing step for making an optical equivalent of a FOFP according to the present invention.

FIG. 12 is a side view of a plate of photosensitive glass in a third manufacturing step for making an optical equivalent of a FOFP according to the present invention.

FIG. 13 is a side view of a plate of photosensitive glass in an optical fourth fabrication step for making an optical equivalent of a FOFP according to the present invention.

FIG. 14 is a perspective view of a liquid holding plate.

FIG. 15 is a perspective view of a FOFP manufactured by using the manufacturing process described in any of FIGS.

FIG. 16 is a perspective view of another FOFP made using the manufacturing process described in FIGS.

FIG. 17 is a side view of a plate of photosensitive glass in another first manufacturing step for making an optical equivalent of a FOFP according to the present invention.

18 is a plan view of a mask used in the manufacturing process shown in FIG.

FIG. 19 is a side view of a plate of photosensitive glass in another second manufacturing step for making an optical equivalent of a FOFP according to the present invention.

FIG. 20 is a side view of a plate of photosensitive glass in another third manufacturing step for making an optical equivalent of a FOFP according to the present invention.

FIG. 21 is a side view of a plate of photosensitive glass in an optical fourth fabrication step for making an optical equivalent of a FOFP according to the present invention.

FIG. 22 is a perspective view of a FOFP manufactured using the manufacturing process described in any of FIGS.

[Explanation of symbols]

40 photosensitive glass substrate, 60 mask, 62 parallel UV radiation, 64 core area, 66 cladding area, 68 core non-irradiation area, 70 cladding illumination area, 72 remaining part, 74 etched part,
84 liquid holding plate, 86 light blocking material.

Claims (1)

[Claims] 1. A method of manufacturing an optical plate having a front surface and a back surface, comprising: At least one substantially cylindrical core area having a core area refractive index and extending substantially from the front surface to the rear surface; and a cladding area refractive index and the at least one core area. Providing a substrate divided into at least one substantially surrounding cladding area; b. B. removing a portion of one of said at least one core area or said at least one cladding area to create a removed partial area; Filling the removed portion area such that the core area refractive index is greater than the cladding area refractive index.