JPH04204401A - Diffraction optical element - Google Patents

Abstract

PURPOSE:To obtain a diffraction optical element of a reflection type with a surface being hard to scar, little deterioration in reflectivity and good environmental resistance by providing a reflection layer and a protective layer on a grating zone. CONSTITUTION:An optical element part 9 is provided with a multiple number of grating zones 7 formed on a substrate 1, the reflection layer 6 provided on the grating zone 7, and the protective layer 5 installed on the reflective layer 6. Incident light 2 is made incident from the side of substrate 1 in opposite to the side of the reflection layer 6, is made into condensed emitted light 3 by having its optical axis folded, and is condensed to a focus 4. By providing the protective layer 5 on the reflection layer 6, the surface of the reflection layer 6 is made hard to be scarred, and at the same time, by preventing oxidization of the reflection layer 6, the diffraction optical element with environmental resistance is obtained. Thus, the diffraction optical element with superior environmental resistance can be realized.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a diffractive optical element.

Conventional technology Diffractive optical elements (hereinafter referred to as diffractive optical elements) have a grating structure, so they have a light-concentrating effect with a film thickness of several μm at most, and they can be made into ultra-small and light-waxed materials. It is attracting attention as an important optical element.

Conventional diffractive optical elements include the reflective lenses shown in Figure 2 (for example, ■, Geo8, 49 Kawa,
K, t Fune, ■, Mizuki (T, 5hlO1
+0+ M, Itagawa, K.

5eLsune and T, Mitsuyu
): "Reflection m
1cro-Fresnellenses and th
eiruse in an integrated
d focus sensor)” Y fly t7
'Ti92 (Appl, opt,,), V
ol, Ill, Jio 15. pp.

3434-3442 (1989)). Figure (a)
1 is a plan view of the reflective lens, and FIG. 3B is a sectional view.

In the figure, a plurality of grating zones 7 each having a sawtooth cross section are provided concentrically on a substrate l, and the zones 7
7, a reflective layer 6 is provided to constitute an optical element section IO.

Note that 2 represents incident light, 3 represents condensed and emitted light, 4 represents a focal point, and 8 represents air.

Problems to be Solved by the Invention However, in the conventional diffractive optical element shown in FIG. 2, the surface of the reflective layer 6 is easily damaged, that is, the grating zone 7 is easily damaged, and the metal layer used as the reflective layer 6 is Since the surface is uneven, it is more easily oxidized than when it is deposited flat, which causes a problem in that the reflectance decreases and the light collection efficiency deteriorates.

The present invention has been made in view of the above-mentioned problems with the conventional diffractive optical probe, and an object of the present invention is to provide a reflective diffractive optical element that has a surface that is hard to be damaged, has almost no decrease in reflectance, and has good environmental resistance. With the goal.

Means for Solving the Problems The present invention provides a plurality of grating zones formed on a substrate, a reflective layer provided on the grating zones,
The diffractive optical element includes a protective layer provided on the reflective layer.

Effect In the present invention, anti-111F! By providing the flt layer on top of ', the surface of the reflective layer is hard to be damaged, and at the same time, oxidation of the reflective layer is prevented, thereby realizing a diffractive optical element with environmental resistance.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing the basic structure of a diffractive optical element according to an embodiment of the present invention, and shows how incident light is condensed.

In the figure, the optical element section 9 has a plurality of grating zones 7 formed on a substrate l, a reflection i6 provided on the grating zone 7, and a protective layer 5 provided on a reflection N6.

This example is a case of a reflective diffraction optical lens, as in the conventional example, and the planar structure of the grating zone 7 is concentric circles, and the circumference becomes smaller toward the outer periphery (as in the conventional example). (See Figure 2(a)).

The incident light 2 enters from the side of the substrate 1 opposite to the reflective layer 6, turns its optical axis, becomes condensed outgoing light 3, and is condensed at a focal point 4.

In this embodiment, the manufacturing method is as follows:
A grating zone 7 is formed. For example, use a glass substrate with a TO transparent conductive film as the substrate l, coat it with a synthetic resin sensitive to electron beams called electron beam resist, such as PMMA or CMS, and then apply electron beam resist. An electron beam was irradiated using a beam drawing device so as to correspond to the pattern shape of the optical element to be manufactured.

Thereafter, by performing a development process, the film thickness of the grating zone 7 is changed, and then the first reflective layer 6 is formed.
For example, a metal layer such as Ag, AI, Au, etc.
Approximately 0OA was deposited. By making the thickness of the reflective layer 6 larger than the maximum thickness of the grating zone 5 (for example, 0.2 μm), the reflection efficiency can be increased.

Then on top of the reflection N6 as protection N5, e.g.
Metal layers such as AI, Cu, and Cr, synthetic resins such as UV curing resins and lacquer paints, dielectric multilayer films, S io,
Sio2. The optical element portion 9 was formed by depositing MgF2, Sac, graphite, diamond, etc., for example, in a thickness of several 77 m from 100 OA.

In particular, if Ag is used as the reflective layer 6, for example, the wavelength λ''
When a 0.6328I1m He-Ne laser beam was used as the incident light 2, the reflectance was the best, and the light utilization efficiency of the diffractive optical element could be improved. Furthermore, Ag reflection N
In the case of using 6, the effect of the present invention was greater because it was more easily oxidized than in the case of using other metal layers.

At this time, when the Ag reflective layer 6 was used, there was a problem that the adhesive strength between the reflective layer N6 and the grating zone 7 was weak and it was easy to peel off, but when A1 is used as the protective layer N5, the reflectance remains high and the adhesive strength is The effect of the present invention was particularly strong.

The diffractive optical lens produced in this example has, for example, an aperture of 1 rnm, a wavelength λ=0.632811 m, and a 2% focal length M
f = 7.5 mtn (in a glass substrate with a refractive index of 1.6), the number of grating zones 5 is 34, the maximum film thickness of each grating zone 5 is 0.2 μm, and the outermost circumference opening of grating zone 5 is 6.371 m. be. The diffractive optical element of the present invention can be manufactured in any other manner in accordance with specifications in addition to those described above. For example, reflective type
Optical elements such as periodic gratings, reflective cylindrical lenses, and reflective elliptical micro Fresnel lenses can also be constructed in the same way by forming grating zones 7 to match them and depositing reflective layers 6 and protective layers 5 thereon. be.

Moreover, although the case where the protective layer 5 of the reflective layer 6 is one layer has been described, a protective layer of 2N or more may be provided.

For mass production, using the element before depositing the reflective layer 6 as a master, a mold is made by, for example, nickel electroforming, and
Replicated from mold using V-cured resin, reflective N6 and protection N
5, a diffractive optical element identical to that of the master can be manufactured at a low cost.

The substrate l only needs to be transparent to the wavelength used.
For example, glass substrates such as quartz are stable in terms of temperature,
If synthetic resin is used for the substrate, it will be lighter.

Effects of the Invention As described above, since the diffractive optical element of the present invention is provided with a protective layer, even if the surface is scratched, the effect on the reflective layer and grating zone is reduced, and furthermore, the metal reflective layer is prevented from being oxidized. This makes it possible to realize a diffractive optical element with excellent environmental resistance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a diffractive optical element according to an embodiment of the present invention, and FIG. 2 is a plan view and a sectional view of a conventional diffractive optical element. l... Substrate, 5... Protective layer, 6... Reflective layer, 7...
...Grating zone. Agent Patent Attorney Matsu 1) Tadashi Michi Diagram 2 (a”) 1 Substrate 6 Anti-l14IllI2 Great sword light 7 Grating f-n 3 Lightning output light 8 Air 4 Focus 10 Optical element part (b)

Claims (3)

[Claims] (1) A diffractive optical element comprising a plurality of grating zones formed on a substrate, a reflective layer provided on the grating zones, and a protective layer provided on the reflective layer. (2) The diffractive optical element according to claim 1, wherein the reflective layer is made of silver (Ag). (3) The diffractive optical element according to claim 2, wherein the protective layer is made of aluminum (Al). (4) The thickness of the reflective layer is larger than the maximum thickness of the grating zone. Item 1. Diffractive optical element according to item 1.