JPH02176601A - Projection lens and its manufacture - Google Patents

Abstract

PURPOSE:To realize image formation which is small in aberration add distortion by forming an optical element having a layer which varies in refractive index between its center part and peripheral part. CONSTITUTION:The optical element 21 as the projection lens is formed of the optical element which is formed of a converging lens whose surface is plane and has the layer 22 varying in refractive index between its center part and peripheral part. The refractive index of the optical element 21 is larger at part 23 nearby the center than at the peripheral part 24 and has such a gradient that the refractive index decreases gradually from the center part to the peripheral part. For thus constituted projection lens, an optical path difference is generated in the optical element 21 owing to the difference in refractive index to change the traveling direction of a light beam, so the optical element 21 whose surface shape is flat is securely obtained. Consequently, the image formation which is small in aberration and distortion is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a generally used converging/diverging projection lens in an optical system and a method for manufacturing the same.

[Conventional technology]

Conventionally, as this type of projection lens, a convex lens 1 and a concave lens 2 shown in FIGS. There is.

These lenses are homogeneous and have two spherical polished surfaces to form an optical path difference, converging light 3 (A).

This is caused by divergence (B).

Next, a method for manufacturing this type of projection lens will be explained with reference to FIG.

First, the glass 11 is heated and melted. Next, this is poured into the lens forming hole 13 of the mold 12 formed in advance and cooled. After that, the lens material 14 is subjected to surface treatment.

In this way, a projection lens can be manufactured.

[Problem to be solved by the invention]

By the way, in conventional projection lenses and their manufacturing methods, the surface of the lens material 14 is spherically polished to form an optical path difference, so the surface shape is subject to restrictions, and compared to spherical polishing, the lens There was a problem in that it made manufacturing and processing difficult. Furthermore, when the surface of the lens is spherical, it is not possible to obtain an image with less aberrations and distortion than when the surface is polished flat, and there is also the problem that reliability in terms of lens quality is lowered.

The present invention has been made in view of the above circumstances, and provides a projection lens and a method for manufacturing the same, which can facilitate lens manufacturing and processing and improve reliability in terms of lens quality. It is something.

[Means to solve the problem]

The projection lens according to the present invention is an optical element through which light rays pass, and is formed by an optical element having a layer whose refractive index changes between a central portion and a peripheral portion.

Further, a method for manufacturing a projection lens according to another aspect of the present invention includes the steps of sequentially forming layers each consisting of a plurality of different impurities on a substrate, applying pressure and heat treatment to the layers, and then applying pressure and heat treatment to the layers. The method includes a step of performing a treatment.

[Function] In the present invention, an optical path difference occurs due to the difference in refractive index within the optical element, and the traveling direction of the light ray can be changed.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, the structure etc. of this invention will be explained in detail by the Example shown in the figure.

FIG. 1 is a sectional view showing a projection lens according to the invention, and FIG. 2 is a diagram showing a refractive index distribution within the projection lens according to the invention. In the figure, an optical element as a projection lens indicated by reference numeral 21 is formed of a condensing lens whose surface is flat. This optical element 21 is formed of an optical element having a layer 22 whose refractive index changes between the central part and the peripheral part. The refractive index of this optical element 21 is configured such that a portion 23 near the center has a larger refractive index than a peripheral portion 24. That is, the refractive index is set to have a gradient that decreases continuously from the center toward the periphery. In addition, the reference numeral 25 in the figure
and 26 are incident light and outgoing light.

In the projection lens configured in this way, an optical path difference occurs due to the difference in refractive index within the optical element 21, and the traveling direction of the light ray can be changed. You can definitely get it.

Furthermore, in the present invention, since the lens surface is flat, it is possible to obtain an image with fewer aberrations and distortions than when the lens surface is spherical.

Here, to explain the progress of light rays passing through the projection lens of the present invention with reference to FIG.
4, the radius of the component wave 27 of the incident light 25 is smaller in the portion 24 near the center than in the peripheral portion 25. For this reason, the equiphase surface 28 that was linear at the time of incidence becomes a curved equiphase surface 29, and the light beam is directed to this equiphase surface 29.
The output light 26 travels in the normal direction and becomes converged. Incidentally, the incident light 25 is a plane wave that travels with a linear equiphase surface 28, and the equiphase surface 28 of the incident light 25 that has entered the lens surface 30 is linear.

Next, regarding the method of manufacturing a projection lens according to the present invention, the fourth
This will be explained using figures (al to (f)). In the figure, reference numeral 31
32 is a flux as a first and second impurity doped into the glass substrate 33 (the types of both fluxes 31 and 32 are different from each other), 34 and 35 are deposits due to each flux 3L and 32, and 36 is a compressed device 37
a vacuum system 39 and 4 that evacuates the inside of the processing container 38;
0 is a diffusion furnace and a heater.

First, by injecting flux 31 into the surface of a thin glass substrate 33 as shown in FIG.
A deposit 34 is formed as shown in FIG. At this time, if a focused ion beam (FIB) is used, the distribution of fluxes can be precisely controlled. Next, by injecting the flux 32 onto the deposit 34 as shown in the figure (bl), a deposit 35 is formed as shown in the figure (C1). Board 3
Formed on the front and back surfaces of 3. Thereafter, one or more glass substrates 33 are prepared, and as shown in FIG. 3D, the glass substrates 33 are housed in a processing container 38 of a compression device 37 and evacuated by a vacuum system 36.

Then, after compressing this, it is annealed by a heater 40 in a diffusion furnace 39 as shown in the same figure (el).
The surface of fl is treated as shown by arrow 41.

In this way, a projection lens can be manufactured.

The production of the projection lens in this example is shown in Figure 5 (a).
) and (VAI) method, which is a glass fiber manufacturing method as shown in bl, or FICVD method. In the figure, 70 is oxygen gas, 71 is 5iC14, 72 is GeCl4.73 is a rotary connector,
74 is a chuck, 75 is a quartz tube, 76 is a sooty glass deposit, 77 is an oxygen-hydrogen burner, 78 is a transparent glass layer, 7
9 is a glass lathe, 80 is a quartz base material, 81 is a ring-shaped heater, 82 is a porous base material, 83 is a burner, 84 is a 5iC
14 is a raw material gas, and 85 is an oxygen-hydrogen gas.

The MCVD method is carried out by introducing carbon tetrachloride (CC14,) 71, a raw material for quartz glass, into a quartz tube 75 together with carbon gas 70, as shown in FIG. Since it is rotated by a glass lathe 79, glass fine particles 76 become soot-like and accumulate on the inner wall of the quartz tube 75 as the oxygen burner 77, which is the heating source, moves, and then the temperature reaches a high temperature of about 1500°C. This process is repeated to control the refractive index distribution by changing the additive gas concentration for each layer.Then, after the deposition process is completed, the glass layer is heated to about 2000°C. The hollow part inside the quartz tube 75 is crushed at high temperature.

On the other hand, the νAD method is carried out by spraying 5iC1a 84 together with oxygen-hydrogen gas 85 from below the quartz rod 80 that is being pulled up while rotating, causing a chemical reaction by a burner 83, and depositing soot-like glass particles in the axial direction. be exposed. Then, this deposit is transferred to a ring-shaped heater 8.
By heating according to step 1, a transparent vitrified base material is formed. In this case, since the equilibrium state differs depending on the temperature distribution in the flame of the burner 83, a concentration distribution of the additive occurs, and a refractive index distribution can be obtained by controlling the temperature distribution of the burner flame.

The base material formed by such a method is formed into a cylindrical shape, as seen in the transparent glass 78 and the porous base material 82. Thereafter, the projection lens of the present invention is formed by slicing (cross-cutting) into a desired cross-sectional shape, and then polished into a desired cross-sectional shape. In this case, any cross-sectional shape can be selected because the optical path difference can be compensated for by controlling the refractive index.

Further, although the surface shape of the projection lens in this embodiment is a flat surface, the present invention is not limited to this, and the surface shape and lens thickness distribution can be arbitrarily selected. Desired contact lenses and other eyeglass lenses can be manufactured.

Furthermore, in this embodiment, the optical element 21 has a gradient in which the refractive index changes continuously, but the present invention is directed to an optical element 21 having a gradient in which the refractive index changes discontinuously. There is no problem with that.

Furthermore, although this embodiment shows an example of application to a condensing projection lens, the present invention is not limited to this.
By reversing the magnitude of the refractive index at the center and the periphery of the lens, it can be applied to a diverging projection lens.

〔Effect of the invention〕

As explained above, according to the present invention, the optical element transmits light rays and is formed of an optical element having a layer in which the refractive index changes between the central part and the peripheral part. The method includes a step of sequentially forming layers made of multiple impurities with different impurities on a substrate, and a step of applying pressure and heat treatment to the layers, and then surface treatment. The difference causes an optical path difference, and the traveling direction of the light beam can be changed. Therefore, since it is possible to reliably obtain an optical element with a flat surface, it is possible to obtain an image with less aberration and distortion compared to an optical element with a spherical surface, improving quality reliability. can be done. Further, the fact that the surface shape of the optical element is flat has the advantage that manufacturing processing can be easily performed.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a projection lens according to the present invention, FIG. 2 is a diagram showing a refractive index distribution within the projection lens according to the present invention, and FIG. 3 is a diagram showing the progress of light according to an embodiment of the present invention. Figures 4 (al to (fl) are cross-sectional views showing the manufacturing process of the projection lens according to the present invention, Figures 5 (a) and (bl) are views for explaining other methods of manufacturing the projection lens, 6(a) and (bl) are diagrams showing a conventional convex lens and a concave lens, and FIG. 7 is a schematic diagram showing the manufacturing process of a conventional projection lens. 21... optical element, 22... layer , 23...
Part near the center, 24... Surrounding part, 25...
・Incoming light, 26... Outgoing light, 31.32... Flux, 33... Glass substrate, 34.35...
- Deposit, 36... Vacuum system, 37... Compression device, 38... Processing container, 39... Diffusion furnace, 40...
···heater. Deputy Masuo Oiwa＼t Kihiso61

Claims (2)

[Claims] (1) A projection lens, which is an optical element through which light rays pass, and is formed by an optical element having a layer whose refractive index changes between a central portion and a peripheral portion. (2) A projection characterized by comprising a step of sequentially forming layers each consisting of a plurality of different impurities on a substrate, and a step of applying pressure and heat treatment to the layers, and then surface treatment. How to manufacture lenses.