JPS60501131A - Improvements in zone plate manufacturing - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Name: Improvement of zone plate ff structure Technical field The present invention relates to zone plate manufacturing.

Technology background Zone grates act in the same way as lenses, but in principle, lenses rely on refraction. , which brings light to the focal point, whereas zone grates do so by diffraction. There is a difference. In fact, zone plates are widely used because they suffer from two disadvantages: Not used. First, zone plates produce large chromatic aberrations; λ is its low efficiency. In other words, given the incident light energy, In other words, the amount of light formed by the zone plate is greater than the amount of light formed by the lens. This means that there are fewer Early zone plates were alternately opaque and transparent. It consisted of a pair of concentric rings. This n is one that corresponds to both positive and negative focal lengths. Create a diffracted order for a series Ru. The maximum ratio of projected energy towards a given order is approximately /θ%. after that, Instead of making the rings alternately opaque, the distance between the light from adjacent rings is /gO°. It was revised to create a zone grade that provides a phase difference. This zone plate The maximum efficiency for the first order diffraction is θ%. Currently, to improve the above efficiency is a blazed zone grate, i.e. the cross section of the ring that makes up the zone grate is Triangular in shape, each ring serves as a zone prism that directs light towards the focal point. This has been achieved by However, the above effect is related to diffraction, and In other words, the contribution of light from the zone must be in the same phase. . It is difficult to manufacture the blazed zone grate, and the present invention makes it easy and inexpensive. A method for manufacturing a blazed zone plate according to the present invention includes the following steps: In other words: (1) Appropriate Providing a single substrate; (11) A layer of photosensitive material that can be selectively removed depending on the amount of projected light is provided on the substrate. to run, (＋＋＊＞Monochromatic diffraction) A light image forming a concentric ring of turns is placed on the photosensitive material layer and the radius of each ring of each diffraction zone of the zone grade to be manufactured. radius of all rings of the above pattern simultaneously over a range equal to the width of the direction By changing the intensity of the light image projected onto the photosensitive material, exposing the material with an intensity varying in the radial direction, (1v) at least also processes said photosensitive layer such that a radial cross-section of at least one of said layer and said substrate is , the circumference of the concentric zone/g turn forming the blazed zone plate is constant. 3 due to the intensity change in the radial direction, which is the light intensity. It consists of changing things.

The method includes treating the photosensitive layer and substrate to form a zone grade thereon. It encompasses what is done.

The diffraction and turns of the same knob ring mentioned above can be created using a Fapley-Perot interferometer. and the radius of each of the above diffraction patterns is the optical radius of the interferometer plate. Can be changed by changing the spacing.

The optical spacing of the interferometer plates changes the refractive index of the medium between the plates. It can be changed depending on the situation. Optionally, the optical spacing of the plates is such that one plate It cannot be changed by physical movement of a great, such as moving it closer to or farther away from another great. child Such movements may be made, for example, by piezoelectric transducers.

Optionally, the radius of each of the rings of diffraction-generating turns is projected onto the interferometer. This can be done by changing the wavelength of light.

The above method also reduces the intensity of the light image projected onto the photosensitive material and all of the above gloss turns. The radius of the ring is varied in discrete steps to encompass features that approximate the desired shape. Contains.

The invention extends to zone plates made by the method described above.

The present invention is further described by way of example only and with reference to the accompanying drawings in which FIG. FIG.

Figure 2 schematically shows an apparatus for changing the refractive index of the stages in the method for manufacturing blazed zone plates. Shown schematically.

Figure 9 shows the Pezometer used to change the optical spacing of the gratings of the Fabry-Perot interferometer. 1 schematically shows an electrical device;

The present invention uses a Fapley-Bello interferometer. Diffusing the interferometer from one side When illuminated by a monochromator, the light emitted from the other side is connected to the ring of the zone plate. Make flat turns of geometrically similar concentric rings. Such an interferometer is The ring formed by the internal reflection is therefore very narrow. Ru. The ratio of the radial width of the length to the radial separation distance is It is known as finesse. In Figure 1, d is radial width measured at half height It is shown as . Therefore, the fines in this pattern is d/Δ.

The finets are a function of the internal reflections of the zone grates that make up the interferometer. centre High values of Inetus are desirable for purposes of the present invention.

FIG. 1 also shows the manufacturing steps of a zone plate according to the invention. For example, glass Such substrates are indicated by 10-n. For example, on the substrate 10 there is a photoresist. A layer 12 of photosensitive material is provided. The narrow groove 14 provides continuous illumination in the radial direction. A cross section of the ring projected onto the photoresist from the Fapley-Bello interferometer is shown. centre Photorenost can be changed within a certain range depending on the exposure time and illumination intensity. 14 is created by subsequent chemical treatment of the photoresist. This chemical treatment The theory itself is publicly known.

Alternatively, if desired, the grooves can extend into the substrate 10 as shown at 16. Chemical treatments can also be used.

Figure Ω shows another step in the method of the invention. As already mentioned, the first exposure Changes are made in the resist to create the cross section shown at 14. However, the desired The new objective is to create a cross-section for the blaze, which is a triangular cross-section as shown by the plumb line 18. It is to do so. Such a triangular cross-section can be further This is done by exposing the photorenost to light. All three exposures are shown. However, by controlling the exposure time and illumination brightness, more A number of more closely spaced exposures are made to achieve the final shape shown at 18. [ru. 14, 20.22 consecutive exposures can be carried out according to the method described below, thus The concentric rings of light produced by the interferometer move each other through turns. It is necessary to do so.

In Figure 3, the substrate and photorenost are shown in 10.12. The purpose is to form a blaze zone plate on the n et al. The light source for monochromatic lighting is N1, indicated at 24, is conveniently a laser device. The light from the light source is diffused through the screen 26 and proceed to an interferometer, generally designated 28. Emitted light from interferometer (shown on the right) is provided by a lens system designated by 30. Focused on layers 1 and 2 of photoresist, the optical image of the concentric rings, i.e. 1 in Fig. 4. Image the object corresponding to 4. This light image is the interferometer play) 32.34 optical By changing the interval, the pattern can be changed to correspond to 20 and 22. This n. One apparatus for accomplishing this is shown in FIG. The space 36 between the greats 32 and 34 is Constructed to follow pre-adjusted gas pressure. The gas pressure in the space 36 increases. As the plate increases, the refractive index of the gas between plate 32.34 increases and the plate In order to achieve an optical separation of 0.5 times the wavelength of monochromatic light, Each ring in the pattern moves outward ( or inside). Due to the change in gas pressure in the space 36, 14,20 A continuous ring pattern corresponding to ゜22 is made at or near the middle of each position. As a result, exposure is increased for that position.

In order to obtain the shape 18, the exposure is done continuously and for a short time, or the illumination light is The intensity is 38 and is roughly shown as 7 It is reduced using a squeezing device. The gas pressure in space 36 is pressurized NFC gas The vacuum pulp unit 42 is supplied from a source 40 and controlled by a vacuum pulp unit 42. The leakage to the atmosphere (not shown) is controlled by a leakage control (not shown).

The necessary pattern of concentric circles and mother turns of the light image formed in 12 is based on the light used. It is formed in a dynamic manner by changing the wavelength. For this reason, the optical image 24 has an output wavelength of It is a laser that is adjustable over a small range. Change the mother turn for the above The method is such that one grate is geometrically adjustable relative to the other plate. The purpose is to construct an interferometer. This is shown schematically in FIG. one side of the interferometer The plate 34 is fixed to the casing 44 while the other plate 32 is fixed to the casing 44. The plate 32 and the ring 46 are fixed to the plate casing 44 in the ring 44. A cylinder 48 made of piezoelectric material is arranged in between. Electric power (illustrated) An adjustable DC voltage is applied to the cylinder 48 through the axial and the position of plate 32 relative to plate 34 is changed so that both plates are The optical spacing of ports 32, 34 changes.

A pattern of concentric circles of light on the cyst 12 is shown. (for example) The illumination intensity is controlled by continuously changing the optical spacing of the interferometer plates and by controlling the diaphragm 38. It is also possible to change the pattern by making continuous changes at the same time.

After the above exposure, the photoresist is deposited in the irradiated areas in a conventional manner. The method is then removed to create a blaze shape 18 (FIG. 2). moreover , chemical treatment transfers the required cross section to a mechanically more resistant substrate than the photosensitive layer. Can be done. If a reflective zone plate is required, the substrate should be made of a suitable metal. or a metal coating is applied to the remaining photosensitive layer, for example by vacuum evaporation. I get kicked. For transmission zone plates, the substrate is glass. if you need it For example, blazed zone plates made as described above may be cast or otherwise The zone plate may be used as a master replica by the method.

With the zone plate according to the invention it is possible to increase the efficiency to 60%.

Efficiency can be further improved by using even better quality interferometers. Possible investigation report PCT/GB 83100485

Claims (1)

[Claims] l A method for manufacturing a blazed zone plate, comprising: (i) shaping the zone plate; preparing a suitable substrate (1o) to be carried out; (11) Layer Cl2 of photosensitive material that can be selectively removed depending on the amount of projected light is provided on the surface of the substrate (1o), (ii 2) Project each blaze zone of the zone grate to be created onto the layer of simultaneously over an area equal to the radial width (18) for each ring of the ring. A light image that changes the radius of all the rings of the turn and simultaneously projects it onto the photosensitive material In order to change the intensity of the light, the photosensitive material can be I was exposed to light, and furthermore, (1v) At least the photosensitive layer (12) is treated so that the layer and its substrate (10 ) is changed by the above change in the intensity of the light. A pattern of two concentric zones with a constant perimeter to form a blazed zone plate. thing A method characterized by comprising; λ, in the method according to claim 1, the photosensitive layer (12) and the substrate (10) are treated. the cross-section created in the photosensitive layer is substantially within the substrate (within 10' A method characterized by being played to form a zone great there. 3. In the method described in claim 1 or 2, the diffraction/glue of the concentric ring The turn is characterized by being produced by a Fapley-Bello interferometer (28). Method. Hiroshi: In the method according to claim 3, each of the diffraction i4 turns is The ringing radius is the change in the optical spacing of the interferometer (28)' (32,341). A method characterized in that it can be changed by. Left The method according to claim 7, the plate method. In the method described in item 7, the optical Spacing physically moves one plate perpendicular to the other A method characterized in that it is particularly variable. 7. The method according to claim 6, wherein the movement is performed using a piezoelectric transformer. A method characterized in that the method is performed by a user (48). g. In the method according to claim 3, each of the diffraction and mother turns The radius of the ring can be changed by changing the wavelength of the incident light (24) on the interferometer. A method characterized by: --Go to Exit 1~! α h N Δ1 ■ - Do Tsume Misfortune 1-11 In the method described in Section 1, the intensity of the light image projected onto the photosensitive material and the above-mentioned turns are All ring radii of A method characterized by the fact that it can be brought close to surfaces. 10 By the method described in any one of claims 1 to 9. A plain zone great that is characterized by a forest of trees.゛ /l An apparatus for making a plain zone plate on a substrate having a photosensitive material layer, comprising: A Fapley-Bello interferometer ( 28) and each of the diffracted R-turns created by the interferometer (28) A device characterized in that the radius of the ring (14) can be changed; /2. The device according to claim 1/1, in which the optics of the plates (32, 34) The distance between the plates can be changed by changing the refractive index of the medium between the plates. Device. 13. In the device according to claim 12, between the plates (32, 34,) The medium is a gas, and its refractive index can be changed by changing the pressure of the gas. A device characterized by: /'A In the apparatus according to claim 1, the plate "" ("32, 3 An optical spacing of 41 means that one plate approaches the other plate in its perpendicular direction. A device characterized in that it can be changed by physical movement, such as moving away. /In the device according to claim 11, the physical movement is performed by playing) (3). Changing the dimensions of the piezoelectric current transducer (48) acting between 2 and 31) By ■