GB2277998A - Mask and apparatus for producing microlenses - Google Patents

Abstract

A mask for producing microlenses comprising an opaque layer which has a plurality of openings of different sizes and at different locations which conform to the microlenses to be produced, the mask preferably being formed of an array of subpixels 55 of various grey scale elements 57 (see also Fig 12), the array preferably being 40 x 40. This mask 51 is used to produce microlenses in a single exposure via shutter and lens a silicon chip which is coated with a photoresist which is developed after exposure. The exposure can be repeated by moving the XY stage in either the X or Y directions. <IMAGE>

Description

METHOD AND APPARATUS FOR FABRICATING MICROLENSES This invention relates to methods and apparatus for fabricating microlenses, micro-optical and other components.

Individual microlenses fabricated in accordance with the present invention may typically range in size from a diameter of 50 microns to a few millimetres.

Binary fabrication processes have been used to fabricating microlenses in the prior art.

A series of masks, masking steps, exposure steps and etching steps are used in binary fabrication.

In conventional binary fabrication a photoresist is applied on top of a substrate, and a series of masks are used in sequence to produce the final microlens configuration. The process involves applying a mask, exposing the photoresist through the mask, developing the photoresist, and then etching the exposed substrate.

This sequence of operations is repeated for a second mask. It is usually necessary to repeat this masking, exposing, developing, etching sequence three or more times in order to obtain a microlens having the desired optical performance.

Maintaining the required registration of the masks during the successive masking, exposing, developing and etching sequences can be a problem.

Producing complex microlens designs can become difficult using binary fabrication.

Some lens designs cannot be fabricated by binary fabrication techniques.

The method and apparatus of the present invention permit a microlens of any designed configuration to be fabricated.

The invention provides a method of fabricating a component having a surface which varies in height relative to a notional datum plane, which includes the step of exposing a material to radiation to which it is sensitive through a mask having an array of openings corresponding to the area of the surface, the size of the openings being related to the height of the respective area of the surface above the datum plane.

The invention also provides apparatus for fabricating a component having a surface which varies in height relative to a material datum plane, comprising means for exposing a material to radiation to which it is sensitive using a mask having an array of openings corresponding to the area of the surface, the size of the openings being related to the height of the respective area of the surface above the datum plane.

The method and apparatus of the present invention use only a single exposure mask.

In the present invention a replica of the designed microlens is produced in a photoresist material with a grey scale mask, and the replica is subsequently used for producing the designed microlens in a substrate material.

In the present invention an exposure mask is constructed with a plurality of precisely located and sized light transmitting openings. The openings are formed with sufficiently small specific opening sizes and are located at a sufficiently large number of specific locations, which locations are correlated to related locations on the configuration of the designed microlens, to enable a replica image of the designed microlens to be produced in a photoresist material.

The replica image is produced by exposing the photoresist material to light through a grey scale mask, of a selected wavelength (usually ultra violet), transmitted through the openings in the exposure mask for a selected duration of time. The exposed photoresist material is then processed to produce a replica in the photoresist material of the designed microlens. This replica is subsequently used for producing the designed microlens in a substrate material by differential ion milling.

In a specific embodiment of the present invention the photoresist material replica is placed on a substrate material, and ion milling is used to reproduce the replica directly in the substrate material utilizing differential ion milling for the particular substrate.

Microlens fabrication methods and apparatus which incorporate the features described above and which are effective to function as described above constitute specific objects of the present invention.

The invention will now be described in greater detail by way of example with reference to the accompanying drawings, in which: Figure 1 is a photograph, greatly enlarged, of a dispersive microlens fabricated by the grey scale, single exposure mask, microlens fabrication method and apparatus of the present invention.

Figure 2 is a photograph, greatly enlarged, of an array of identical dispersive microlenses (like the dispersive microlens shown in Figure 1) fabricated by the grey scale, single exposure mask, microlens fabrication method and apparatus of the present invention.

Figure 3 is an isometric view of a wideband microlens fabricated by a binary, multiple masking steps, multiple etching steps, fabrication process used in the prior art.

Figure 4 is an isometric view showing how three separate binary masks are used in three separate exposure and etching steps used in the prior art to produce the binary fabricated wideband microlens shown in Figure 3.

Figure 5 is an elevation view, in cross section, taken generally along the line and in the direction indicated by the arrows 5-5 in Figure 3, showing how the prior art, binary fabricated lens has a series of distinct step surface contours formed by flat surfaces 39 and vertical surfaces 37. In Figure 5 the smooth surface configuration indicated by the reference numeral 41 indicates how this same microlens can be formed with a substantially smooth surface contour when the microlens is fabricated by the grey scale, single exposure mask, microlens fabricating method and apparatus of the present invention.

Figure 6 is a view in cross section through a dispersive microlens. Figure 6 shows how the dispersive microlens has distinct step surface contours formed by flat surfaces 39 and vertical surfaces 37 when fabricated in accordance with prior art binary, multiple masking steps and multiple etching steps fabrication. Figure 6 shows how the microlens has substantially smooth surface contours 41 when fabricated by the grey scale, single exposure mask, microlens fabrication method and apparatus of the present invention.

Figure 7 is an isometric view showing how a dispersive microlens is designed to have any desired configuration, as represented by the microlens 21 shown within the three dimensional plot. The three dimensional plot includes a fine two dimensional length and width grid to provide a fine resolution of the height of the lens surface at each grid line intersection. This also provides a fine gradation of the information on the change of configuration in the surface of the microlens. That fine gradation of information enables a smooth surface to be produced on the fabricated microlens.

Figure 8 is a table listing the height of the lens surfaces at the various grid line intersections shown in Figure 7. The values of the table shown in Figure 8 are used in conjunction with a calibration curve shown in Figure 16. The calibrated values are then used to determine the mask opening size which will pass the proper light intensity at each location corresponding to a related grid line intersection. The proper light intensity at each location produces a thickness of cured photoresist material which replicates the height of designed microlens at that location. This will be described in greater detail in the description below.

Figure 9 is an isometric view (showing the designed microlens illustrated in Figure 7) as finally fabricated in a substrate material, using the grey scale, single exposure mask, microlens fabricating method and apparatus of the present invention.

Figure 9 is a drawing view of the dispersive microlens shown in the Figure 1 photograph.

Figure 10 is an isometric view showing how an exposure mask is positioned above a layer of photoresist, which in turn is positioned on a substrate material in accordance with the present invention. In Figure 10 the exposure mask is shown as a single pixel mask which is used to produce a single microlens.

Figure 11 is a fragmentary plan view of a portion of the single pixel exposure mask 51 shown in Figure 10. Figure 11 shows how the single pixel exposure mask is subdivided into subpixels and also shows how each subpixel is in turn further subdivided into grey scale resolution elements 57.

Figure 12 is a plan view showing a number of subpixels of the exposure mask.

Figure 12 shows how a subpixel may have no opening at all to provide zero transmission of the exposure light through the pixel. Figure 12 shows how the subpixels may be formed with progressively larger openings to transmit progressively greater percentages of exposure light through the subpixels. Figure 12 also illustrates how each opening in a subpixel is formed as a multiple of a single grey scale resolution element.

Figure 13 is a photograph, in plan, of a single pixel exposure mask used to fabricate the dispersive microlens shown in Figure 1 and in Figure 9. The single pixel exposure mask shown in Figure 13 will be referred to as a reticle in the description which follows.

Figure 14 is an isometric view illustrating how an optical system may be used to replicate a single reticle into a staged array by a series of exposures and by moving the XY stage in increments in the X and Y directions between exposures. Figure 14 also illustrates how the optical system may be used to photoreduce the size of the reticle. The optical system of Figure 14 may also be used to photoenlarge the size of the reticle, either as a single reticle replication or in the course of making a staged array of enlarged reticles.

Figure 15 is a fragmentary side elevation view, in cross section, showing how, in accordance with the present invention, a replica of the designed microlens is formed in photoresist material at an intermediate stage of fabrication of the designed microlens in the substrate material. Figure 15 also shows how a subpixel is comprised of a grey scale resolution provided by the number of resolution elements contained within the size of the exposure opening in the particular subpixel.

Figure 16 is a curve showing how the size of the opening in a subpixel is calibrated with respect to process parameters. The process parameters may include variations in the exposure time (shown in Figure 16), the wavelength of the exposing light and the characteristics of the photoresist material. The calibration helps to ensure that the size of the exposure opening in each subpixel transmits enough light intensity to produce the desired replication (first in the photoresist material and ultimately in the substrate material) of the height of the designed microlens at the location corresponding to that particular subpixel.

Figures 17, 18 and 19 are progressive views showing the stages, respectively, of (Figure 17) exposure of the photoresist material through the openings in the single, grey scale exposure mask, (Figure 18) replication of the designed microlens in the photoresist material following processing of the photoresist material after exposure, and (Figure 19) processing (in this case differential ion milling) the photoresist material replica of the designed microlens into the substrate material to reproduce the replica directly in the substrate material.

Figures 20 to 26 illustrate improvements to the embodiment illustrated in Figures 5 to 19.

In greater detail, Figure 1 is a photograph (greatly enlarged) of a single, dispersive, microlens 21 which was fabricated by the grey scale, single exposure mask, microlens fabrication method and apparatus of the present invention.

As can be seen by inspecting Figure 1, the method and apparatus of the present invention produce a microlens with substantially smooth surface contours and without the distinct, step surface contours which are produced by prior art binary (multiple masking steps and multiple etching steps) fabrication processes.

The grey scale, single exposure mask, method and apparatus of the present invention enable, as will be described in more detail below, any configuration of microlens to be designed and to be fabricated.

The grey scale fabricated microlens can be wideband, dispersive, Fresnel, non Fresnel, spherical, cylindrical, toroidal or completely asymmetric in configuration.

In the method and apparatus of the present invention only a single exposure mask is needed.

Multiple masks, as required for conventional binary fabrication method and apparatus, are not needed for fabricating a microlens in the present invention.

In the present invention a single exposure, grey scale, mask is used to produce a replica of a designed microlens in a photoresist material.

That photoresist material replica is then used to reproduce the replica directly in a substrate material.

The single exposure mask method and apparatus of the present invention eliminate problems of misalignment of multiple masks.

Misalignment of the multiple masks (during the multiple masking and etching operations required for prior art binary fabrication) can produce defects in the fabricated microlenses.

The conventional photolithographic technique is somewhat better than 1 micron feature size. For the long wavelength applications, i.e., 10 micro wavelength applications, the conventional photolithographic technique will produce somewhat better than lambda divided by ten (All 0) quality equivalent performance lens.

For shorter wavelength applications, i.e. 1 micron or visible 0.5 micron, (All 0) quality performance requires X-Ray photolithography quality, which is quite expensive and time consuming, especially for non-spherical surfaces.

The present invention can readily achieve (All 0) quality lens for microlenses operating in the infrared.

For microlens operating in the visible the present invention can readily achieve (at3) quality.

The present invention can reduce the time and expense involved in fabricating certain configurations of microlenses as compared to the time and expense required for binary techniques.

The present invention enables certain lens configurations to be designed and fabricated which cannot be fabricated by binary techniques.

The present invention enables certain microlens configurations to be designed and produced which would be too costly to be produced by binary techniques.

For purposes of comparison with the present invention Figures 3 and 4 show, in summary form, how the prior art binary fabrication technique is used to produce a relatively simple wideband microlens 23 is a substrate material 25.

The first step in the prior art binary process is to use a mask 27 for exposing a layer of photoresist 33 on top of the substrate 25. This exposed photoresist is then developed and then chemically removed, exposing the substrate for subsequent etching. The underlying exposed substrate 25 is etched or milled to the required depth.

The substrate is then recoated with photoresist for a second masking, exposing and etching step.

This masking, exposing and etching procedure is then repeated for a second mask 29.

The masking, exposing and etching procedure is then repeated for the third mask 31 to finally obtain the relatively simple wideband binary fabricated microlens 23 shown in Figure 3.

For a non symmetrical lens, seven or eight masks may be required.

The grey scale fabrication method and apparatus of the present invention (as summarized in the showings of drawing Figures 17, 18 and 19 and as will be described in more detail below) uses a single exposure mask 51 (Figure 17), replicates a designed microlens 61 in a photoresist material 33 in a single exposure and development sequence (Figures 17 and 18) and reproduces the replica 61 directly in the substrate material 25 to produce the finished microlens 21 (Figures 18 and 19).

The binary fabrication technique can become more complex and time consuming as the complexity of the microlens increases.

Some microlens configurations are therefore not suitable for fabrication by binary techniques.

Also, some microlens configurations cannot be produced by binary fabrication techniques.

The quality of a microlens fabricated by binary techniques if dependent upon maintaining accurate registry of the various masks with respect to the substrate component 25. Misalignment can produce ridges and other defects in the fabricated microlens, and the effect on optical performance is dependent on the operating wavelength.

Microlenses fabricated by binary techniques characteristically have a series of distinct step surface contours. See Figures 5 and 6 in which the step surface contours are formed by the flat surfaces 39 and vertical surfaces 37.

Depending upon the relative sizes of the step surface contours, the number of masks used in fabrication, and the wavelength of the light transmitted through the fabricated microlenses, the step surface contours may degrade the optical performance of the binary fabricated microlens.

Microlenses fabricated in accordance with the present invention can be produced with substantially smooth configurations. These smooth surfaces are indicated by the reference numeral 41 in Figures 5 and 6.

Microlenses fabricated in accordance with the present invention eliminate the series of distinct step surface contours resulting from binary fabrication techniques.

Relatively smooth surface configurations can enhance the optical performance of the microlens.

The present invention enables a microlens of any configuration to be designed and fabricated.

The design, for example, may be generated by a computer using a three dimensional modelling program.

As shown in Figure 7 a dispersive microlens 21 may be modeled and contained within a three dimensional plot having X, Y and Z co-ordinates as illustrated in Figure 7.

As illustrated in Figure 7 the X and Y co-ordinates are subdivided by lines into a plurality of equal size increments (80 increments of 0.2 micrometres in each co-ordinate direction in the specific embodiment illustrated in Figure 7) so that the lines form a fine grid for locating precise points on the surface of the microlens 21 and for indicating the height (thickness) of the microlens at each precise point.

By way of example, the height of one corner of the darkened square indicated by the reference numeral 44 in Figure 7 is 5.76 micrometres (as indicated by the rectangle also denoted by the reference numeral 44 in Figure 8). The table shown in Figure 8 lists the Z dimension (thickness or height) of the designed microlens at each point of intersection of X and Y grid lines shown in Figure 7.

In the embodiment of the invention shown in Figures 7-13, the microlens 21 is formed within a single pixel 53 (see Figure 10). Each pixel 53 is subdivided into subpixels 55. See Figure 11. Each subpixel is subdivided into grey scale resolution elements 57. See Figure 11.

In a specific embodiment of the present invention the pixel is 80 micrometres (microns) on each side, each subpixel is 2 microns on each side, and each grey scale resolution element 57 is 0.2 microns on each side. The exposing light is ultra violet light of 0.3 micron wavelength. The resolution elements 57 can be arranged in groups of three in alignment so as to enable a full wavelength of the ultra violet light to pass through an opening formed by three such aligned resolution elements.

The darkened square indicated by reference numeral 44 in Figure 7 is two microns long, so that the darkened square 44 corresponds to a single subpixel 55 as shown in Figure 11.

By using the precise subpixel location information (provided by the fine grid shown in Figure 7) and by using the precise lens height or thickness information for that subpixel location (provided by the Figure 7 plot and the Figure 8 table) the size of a mask opening for that subpixel can be selected. By using an appropriate mask opening transmission pattern (as shown in Figure 12) an exposure in a photoresist material can be created which will cause the height of the hardened photoresist material to replicate the exact height of the designed microlens shown in Figure 7.

Thus, by using a specific size mask opening in each subpixel area of a pixel mask, a pattern of light transmission can be generated through the pixel mask to create a replica image of the designed microlens in a layer of photoresist immediately below the composite mask.

The exposed photoresist material can then be processed using known photoresist processing to produce in the photoresist material a replica of the desired microlens, and this replica can be used subsequently (as will be described in more detail below with reference to Figures 18 and 19) for producing the desired microlens in a substrate material with the application of known differential ion milling technology.

Figure 15 further illustrates details of how the replica image of a designed microlens is produced in a particular photoresist material in accordance with one specific embodiment of the present invention.

In this specific embodiment the hardening of the photoresist material starts at the interface between the substrate 25 and the photoresist and grows upwardly in relation to increased intensity of light transmitted to the photoresist material through the exposure mask.

If only a low intensity of exposure light is transmitted through a particular mask opening to the photoresist material, then the upward extent of the hardening is limited and the thickness of the replica is very thin.

If the intensity of the light (transmitted through a particular mask opening in a particular subpixel) is large, then the height to which the photoresist material hardens is also correspondingly large. In that case only a small amount of unhardened photoresist material is removed from that location in the processing of the photoresist material following exposure.

The amount of unhardened material removed from a particular subpixel area following exposure is indicated by the letter g in Figure 15.

When the unhardened material is removed, the replica 61- of the designed microlens is then formed in the remaining hardened photoresist material as illustrated in Figure 15.

Figure 15 also illustrates how the size of the mask opening in each subpixel 55 provides a grey scale resolution dependent upon the number of resolution elements 57 incorporated within that mask opening. The gradation of the grey scale resolution proceeds from a very light gradation at the left hand side of the upper bar shown in Figure 15 (when the size of the mask opening comprises only a few resolution elements) to a relatively dark grey scale gradation (when the size of the mask opening includes the maximum number of grey scale resolution elements for maximum exposure).

The experimental device shown in Figure 1 was produced with 128 shades in the grey scale. Presently a 9000 grey scale resolution element is being used. The line produced by the 128 grey scale resolution is good enough for the long infrared regime (b10) micron.

However, for the short infrared or visible regime the 9000 grey scale is mandatory.

Figure 13 is a photograph, in plan, of a single pixel exposure mask or reticle 51 which is made up as a composite of the individual subpixel masks described above. The opening in each subpixel portion of the exposure mask or reticle 51 shown in Figure 13 has the specific size needed for passing the intensity of the exposure light required to produce the desired height or thickness of the photoresist replica at that specific location. The photograph of the reticle 51 in Figure 13 clearly shows the variation and gradation of light transmitted through the reticle for producing the structure and smooth surface configuration of the dispersive microlens 21 shown in Figure 7.

The final step in the fabrication of the microlens in the substrate material is to use the photoresist material replica 61 (see Figure 18) as a grey scale mask for reproducing the replica directly in the substrate material 25.

In one embodiment of the present invention (and as illustrated in Figures 18 and 19) the grey scale replica 61 is processed directly into the substrate 25 by known differential ion milling.

The height measurements of the designed microlens (as taken directly from the three dimensional plot illustrated in Figure 7 and the table information illustrated in Figure 8) need, in most cases, to be calibrated for certain processing parameters involved.

Thus, as illustrated in Figure 16, the amount of material removed from a particular photoresist material (in the processing of the photoresist material following exposure through the exposure mask) will be dependent upon the exposure power of the ultra violet lamp used to make the exposure. The sizes of the mask openings in the various subpixel masks may therefore require some modification depending upon the specific parameters used.

Other process parameters, such as, for example, different photoresist materials, may also require some appropriate calibration of the sizes of the individual mask openings.

The fidelity of reproduction of the fabricated microlens (with respect to the designed microlens) can also usually be improved by making a number of test microlenses, inspecting the surface smoothness of each test microlens, and then making some appropriate adjustment in the size of one or more of the subpixel mask openings, until a substantially smooth curvature of all of the lens surfaces is obtained.

When that is achieved, the single pixel reticle 51 structure is finalized.

At that point the reticle 51 can be reproduced (using an optical system as illustrated in Figure 14) to produce a two dimensional, single pixel, array.

The reticle can be replicated into the two dimensional array by making a number of exposures and by moving the XY stage in X and/or Y directions between exposures.

The reticle 51 can also be photoreduced or photoenlarged, alone or as part of a staged array.

In some cases it might be desirable to make the initial reticle somewhat oversized. This can facilitate forming the specific size openings in the subpixels. The oversize mask can then be photoreduced to produce the exact size reticle needed for contact printing at the particular wavelength of exposure light to be used.

In other cases it may be desirable to photoenlarge the reticle to enable the reticle to be used with an exposing light having wavelengths longer than the minimum size mask openings in the original reticle mask.

A preferred way of fabricating the grey scale openings in each subpixel of Figure 11 is by using a half-tone variable transmission mask (Figure 20). This was produced by using an electron beam reticle writer with positional increments of 0.1 m in X and Y co-ordinate directions. The mask is exposed along the diagonal lines, by shuttering an electron beam of constant intensity, and moving the reticle appropriately.

The reticle is electron-resist covering a chromium film on glass. The exposed areas enable the chromium to be etched. The dark diagonal lines correspond to removed chromium. The pattern on the reticle corresponds to the desired micro-lens shape.

A change in transmission could be realised in two ways (Fig. 21).

Figure 21a) Vary the size of an aperture to achieve control of intensity and place them at regular intervals in the X and Y directions, or Figure 21 b) Keep the aperture size constant and vary the x,y spacing to give control of intensity.

With either option a large amount of data is needed to define the e-beam's spatial write program. To minimise the write time, Figure 21a) combined with the minimum number of co-ordinates to define the aperture shape and method of area increase, produced an acceptable write time.

The pitch of the apertures and their incremental changes in size is governed by the following considerations (see Fig. 22). The pitch is determined on the large side by a requirement to preserve a smooth surface on the resist image. The smallest size is limited by diffraction effects within the optics. Within the pitch chosen from the above, the range of aperture sizes is confined by the need to resolve the chrome border and aperture dimensions at either extreme.

The diffraction limit of the stepper equipment used can be calculated using the relationship: 1.22 * N.A./Lambda = limit (where N.A. is the numerical aperture of the stepper optics). This limit is a guide to the minimum size of an aperture that will just expose the resist. Experiments have shown that a pitch size between this limit and the micron level can give excellent smoothing and at the same time, produce no observable inter aperture diffraction effects.

A typical size for the e-beam reticle is 100 mm by 100 mm. The next stage is for a photomask (Figure 24) to be produced. This is U-V resist on a chromium film on glass, typically 100 mm by 100 mm. The reticle pattem is reproduced one tenth of its actual size using U-V light. Having produced one image of the reticle on the photomask, the photomask is stepped in the X and Y directions to record an array of images, for example, a hundred by one hundred.

The final im however the surface of the photoresist coincided with the dotted lines, adjacent cones would just begin to overlap, so that the desired smoothing is obtained. Consequently, the final image is positioned, not at the focus of the lens, but a little distance to either side of the focus, to produce a degree of blur which just negates the digitisation into discrete windows.

As for the embodiments described in Figures 5 to 19, when the thick film of positive photoresist is exposed through this mask, the different levels of transmission are transformed into varying depths of exposure. The masking system provides the opportunity to fabricate shapes of enormous complexity.

To calibrate the aperture size to exposure depth, a progressively stepped e-beam reticle grey scale with a range of 50 equally spaced steps was prepared. The working master produced from this mask was used to calibrate both depth and repeatability of the final image stage. The resulting calibration curve produced the mathematical base for converting the design depth into an aperture size at each ebeam address.

The type of positive photoresist needed for work of this nature is one formulated to give thick layers in excess of 10 pm to be of maximum use. All samples of resist were coated onto 75 mm diameter substrates and the pre-bake performed in a free flowing air oven. The thickness was adjusted during application to achieve a layer which just exceeds the depth range required by the design. The transmission value for a given aperture dimension was defined as the theoretical window area divided by the pixel area. The measured relationship between depth and the product of transmission value and time using the above definition approximate to a straight line.

The resulting calibration curve is shown in Figure 23. The slope increases with exposure time which provides the means by which a fixed range of transmission values can yield any range of depths required by the shape being produced. Current work has demonstrated a range of depth from 0.5 pm to 1 5pm below the original resist surface using the stepped grey scale mask.

The current technology has dimensional limits in all three axes. These are set, in X and y, by the minimum size of masks that can be handled by the equipment used and the mechanical scan of X and Y during final exposure of the images on the substrate. The z limit is controlled by the resist thickness.

The resulting photoresist shapes can be used in a number of ways to provide the required components. The use of ion beam etching to transfer the shape into the substrate directly yields a permanent and useable product in a range of materials. In many applications this process is uneconomic for the final product and there are a number of well known moulding or embossing techniques which can be applied to the original photoresist pattern or to the ion milled replica.

Of course variations may be made to the improvement described without departing from the scope of the invention. Thus, different reductions or 1:1 or even enlargements are possible for the processes illustrated in Figures 24 and 25. Contact printing may also be used. Different photomask and final image areas are possible, as are different number of step and repeat operations.

The components fabricated have been described as microlenses, but more generally, any micro-optic component may be made, or any other micro-component, whether for optical or other purposes.

Claims (27)

1. A method of fabricating a component having a surface which varies in height relative to a notional datum plane, which includes the step of exposing a material to radiation to which it is sensitive through a mask having an array of openings corresponding to the area of the surface, the size of the openings being related to the height of the respective area of the surface above the datum plane.

2. A method as claimed in claim 1, in which the array is a two-dimensional array with regular spacing in each dimension, and the size of the openings is related to the height of the respective area of the surface.

3. A method as claimed in claim 1, in which the array is an array with openings of regular size but variable spacing related to the height of the respective area of the surface.

4. A method as claimed in any one of claims 1 to 3, in which the component is a micro-optic component.

5. A method as claimed in any one of claims 1 to 4, in which the sensitive material is a resist sensitive to the exposing radiation.

6. A method as claimed in any one of claims 1 to 5, in which the mask is derived from the exposure of a substrate-mounted resist layer to an electron beam writer.

7. A method of fabricating in a photoresist material a replica of a microlens of any designed configuration, using a single exposure mask, said method comprising, constructing an exposure mask with a plurality of precisely located and sized light transmitting openings formed with sufficiently small specific opening sizes and located at a sufficiently large number of specific locations, correlated to related locations on the configuration of the designed microlens, to enable a replica image of the designed microlens to be produced in a photoresist material, exposing a related photoresist material to light of a selected wavelength and transmitted through said openings in said single mask for a selected duration of time, and processing the exposed photoresist material to produce a replica in the photoresist material of the designed microlens, which replica can be used subsequently for producing the designed microlens in a substrate material.

8. A method as claimed in claim 7 including, placing the photoresist material replica on a substrate material and processing the replica and the substrate material to reproduce the replica directly in the substrate material.

9. A method as claimed in claim 8 wherein the processing operation is a differential ion mill processing operation.

10. A method as claimed in claim 7 including, designing a desired microlens configuration on a three dimensional plot, applying a fine two dimensional length and width grid to the three dimensional plot of the designed lens to provide a fine resolution of the curvature of the designed lens surfaces by determining of the height of the lens surface at each grid line intersection, constructing a table listing the heights of the lens surfaces at each of the grid line intersections, and constructing the exposure mask based on the table with each of the openings having a specific size and a specific location effective to pass the light intensity required to produce the thickness of cured photoresist material needed to replicate the designed microlens at the location of each opening corresponding to a particular grid line intersection.

11. A method as claimed in claim 10 wherein each opening is a multiple of a minimum, resolution element size opening and wherein the size of the minimum, resolution element opening may be less than the wavelength of the light used to expose the photoresist material through the mask.

12. A method as claimed in claim 11 including calibrating the listings in the table for certain processing parameters involved, including the exposing light and the characteristics of the photoresist material.

13. A method as claimed in claim 7 including duplicating the exposure mask optically to make an array of exposure masks which can be used to make a corresponding array of microlens in the substrate material.

14. A method as claimed in claim 7 wherein the exposure mask is produced by photoreduction of a larger scale mask.

15. A method as claimed in claim 8 wherein both the designed microlens and the microlens reproduced in the substrate material have substantially smooth surface contours rather than step surface contours as produced by binary microlens production techniques.

16. A method of making an exposure mask to be used for producing in a photoresist material a replica of a microlens of any designed configuration1 said method comprising, forming a mask of a material which blocks transmission of light through the material, constructing the mask material with a plurality of precisely located and sized light transmitting openings formed with sufficiently small specific opening sizes and located at a sufficiently large number of specific locations, correlated to related locations on the configuration of the designed microlens, to enable a replica image of the designed microlens to be produced in a photoresist material so that, after exposure of the photoresist material to light transmitted through the openings and after processing the exposed photoresist material, the photoresist material replica can be obtained.

17. Apparatus for fabricating in a photoresist material a replica of a microlens of any designed configuration, using a single exposure mask, said apparatus comprising, exposure mask means having a plurality of precisely located and sized light transmitting openings formed with sufficiently small specific opening sizes and located at a sufficiently large number of specific locations, correlated to related locations on the configuration of the designed microlens, to enable a replica image of the designed microlens to be produced in a photoresist material, exposing means for exposing a related photoresist material to light of a selected wavelength and transmitted through said openings in said single exposure mask means for a selected duration of time, and photoresist processing means for processing the exposed photoresist material to produce a replica in the photoresist material of the designed microlens, which replica can be used subsequently for producing the designed microlens in a substrate material.

18. Apparatus as claimed in claim 17 wherein the photoresist material replica is positioned on a substrate material and including substrate processing means for processing the replica and the substrate material to reproduce the replica directly in the substrate material.

19. Apparatus as claimed in claim 18 wherein the substrate processing means are a differential ion milling processing means.

20. A method as claimed in claim 7 including, computer means for designing a desired microlens configuration on a three dimensional plot and for applying a fine two dimensional length and width grid to the three dimensional plot of the designed lens to provide a fine resolution of the curvature of the designed lens surfaces by determining of the height of the lens surface at each grid line intersection, table means for constructing a table listing the heights of the lens surfaces at each of the grid line intersections, and mask constructing means for constructing the exposure mask based on the table with each of the openings having a specific size and a specific location effective to pass the light intensity required to produce the thickness of cured photoresist material needed to replicate the designed microlens at the location of each opening corresponding to a particular grid line intersection.

21. A method as claimed in claim 20 wherein each opening is a multiple of a minimum, resolution element size opening and wherein the size of the minimum, resolution element opening may be less than the wavelength of the light used to expose the photoresist material through the mask.

22. A method as claimed in claim 21 including calibrating means for calibrating the listings in the table for certain processing parameters involved, including the exposing light and the characteristics of the photoresist material.

23. A method as claimed in claim 17 including photo duplicating means for duplicating the exposure mask optically to make an array of exposure masks which can be used to make a corresponding array of microlens in the substrate material.

24. A method as claimed in claim 17 wherein the exposure mask is produced by photoreduction of a larger scale mask.

25. A method as claimed in claim 17 wherein both the designed microlens and the microlens reproduced in the substrate material have substantially smooth surface contours rather than step surface contours as produced by binary microlens production techniques.

26. A method as claimed in claim 17 wherein the designed microlens is located within a single pixel, and wherein the pixel is divided into subpixels which measure 2 microns by 2 microns and wherein each subpixel is divided into equal size resolution elements related to the wavelength of the exposing light to be transmitted through the openings in the exposure mask means and wherein a minimum size opening in a subpixel may need to be larger than one resolution element in order for the entire energy of the wavelength of the exposing light to be passed through the opening.

27. An exposure mask to be used for producing in a photoresist material a replica of a microlens of any designed configuration, using a single exposure mask, said exposure mask comprising, a layer of mask material which blocks transmission of light through the material, a plurality of precisely located and sized light transmitting openings formed with sufficiently small specific opening sizes and located at a sufficiently large number of specific locations, correlated to related locations on the configuration of the designed microlens, to enable a replica image of the designed microlens to be produced in a photoresist material so that, after exposure of the photoresist material to light transmitted through the openings and after processing the exposed photoresist material, the photoresist material replica can be obtained.