8~3~22 B~CKGROUND OF THE INVENTION
The present invention re]at~s to the production of a design on a flat, arcuate or irregular, non-flat surface.
More particularly, the invention relates to method and ap-para~us for transerring a flat rectangular design onto an image surface, either in a foreshortened circular form on a flat image surface for subsequent formation into an arcuate surface bearing the design in relatively undis-torted form, or directly on an arcuate surfaceO
Multi-colored metal designs have been produced on flat surfaces using conventional photographic masking tech-niques to allow successive selective etching and/or metal deposition corresponding to each color effected~ Such surfaces can then be curved or pressed into a desired shape. However, this procedure is limited by the extent to which an arcuate surface can be formed without excessive distortion of the design, which would usually be in a flat rectangular-coordinate form.
It also`has been proposed to transfer a design from a flat transparency directly onto an acruate surface~
However, no prior procedure has accomplished this trans-- ference without substantial distortion of the design.
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SUMMARY OF THE INVENTION
It is a primary object o.~ this invention to provide a method of reproducing a flat r~ctangular-coordinate design on an arcuate surface with minimum distortion. Is it another object of ~he invention to provide a method of transferring a design from a flat rectangular-coordinate form to a flat polar-coordinate form, or alternati.vely to a radially dis-posed rectangular-coordinate design on an arcuate surface.
It is still another object of this invention to provide a useful means for producing an etched and/or multi-finished foreshortened circular design in a readily repeatable manner as for a production run on each of many flat pieces for subsequent format~on into arcuate shapes. A further object is to provide apparatus for readily producing designs con-forming to differently shaped surfaces and/or in different ~roportions, as for a set, or prototypes, or custom or sample items. It is a further object to provide a method for the successive application of a resist-coat on a flat or arcuate surface corresponding to the finish-separated patterns of a multi-finished design so as to allow successive corre-sponding etching and/or superimposition of different metalsor other coatings by conventional means to reproduce such a design on such surface directly or for subsequent formation into an arcuate sur:Eace bearing such design without apparent distortion.
The method of the present invention provides a means to generate design patterns either on a set of regis-trable masks or directly onto a formable flat surface or . . ~ ,.
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pxe-formed arcuate surface. In one form of th~ invention, transference ic achieved by projection o~ narrow transverse images of the design pattern onto corresponding narrow radial portions or segments of a flat mask or surface.
Light is passed through a transparency bearing the original design in rectangular-coordinate fo~m and formed into a cylinder. The light i5 then redirected by a mirror .through a lens such that the narrow transverse images of the design are projected upon and received in polar-coordinate form by corresponding narrow radial portionsof a photosensitized flat surface~ The flat surface IS
then processed and formed into an arcuate shape bearing the design in relatively undistorted form.
In another form of the invention, the redirected light is again redirected by means of conical mirrors such .~hat the design i5 projected directly upon and received by corresponding transverse poxtions of an arcuate surfaceO In another embodiment of the method of the invention, the re-directed light is projected onto a photosensitized film which is processed into a second transparency bearing the design in polar-coordinate form. The second transparency is then projected toward and received either by an arcuate image surface and is restored to substantially rectangular-`. coordinate disposition, or by a flat image surface which is ~nmed into the arcuate shape.
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In one form of the apparatus of the invention, a design in a flat rectangular form, i.e. rectangular-coordinate form, and created upon a transparency is formed into a cylindrical shape and held upon a supporting surface.
Light is passed through the transparency such that narrow transverse images of the design are projected. A mirror redirects the light through a projection lens. Radial image segments of the projected design are received by corresponding narrow radial areas of the flat surface in foreshortened circular form, i,e. polar-coordinate form.
Aftex exposure/ the coating is fixed and the unexpose~
portion dissolved. The latter area of the surface is then etched, plated or otherwise processea. Finally, the flat surface is formed into the arcuate shape.
If the image surface is a mask, it can be used for repetitive transference of the polar-coordinate design onto other flat surfaces.
If the image surface is an arcuate shape, a mirrored surface is placed between the projection lens and the arcuate surface to redirect the light so as to focus upon the arcuate surface.
In another embodiment of the apparatus of the inve~tion, the redirected light is projected onto a photo-- sensitized film, which may be contained in a camera. The film is exposed and processed into a second transparency, on which the design is in polar-coordinate form~
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D RIPTION OF DRA~INGS
Fig. 1 is a perspective view o~ apparatus for projecting narrow transverse images of a rectanyular design pattern in rotational seciuence onto ,corresponding narrow radial portions of a flat image surface in accordance with one embodiment o~ the invention.
Fig. lA is a view of a portion of the apparatus ~hown in Fig. 1.
Fig. 2 is a sectional, elevational view of the apparatus shown in Fig. 1.
Fig~ 3 is a sectional, elevational view of appara-tus for exposing a photosensitized flat surface to circular patterned masks useful in the method of the invention.
Fig. 4 is a perspective view of an arcuate surface formed in accordance with the method of the invention.
Fig. S is a sectional, elevational view of appara-tus for redirecting the design pattern projection onto an outside arcuate surace.
Fig. 6 is a sectional, elevational view of appara-tus for redirecting the design pattern projection onto aninside arcuate surface.
FigO 7 is a perspective view of apparatus or projecting a design pattern onto a flat photosensitized image surface in accordance with an alternative embodiment of the invention.
Fig. 8 is a sectional, elevational view of appara-tus for redirecting the design pattern projection onto an outside arcuate surface in accordance with the alternative embodiment of the invention shDwn in Fig, 7.
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Fig. 9 is a sectional, elevational view of appara-tus for redirecting the design patt~rn projection onto an outside arcuate surface in accordance with a further embodiment of the invention shown in Fig. 7.
Fig. 10 is a perspective view of modifie~ appara-tus for projecting transverse portions of a rectangular design pattern onto corresponding radial portions of a flat image surface in accordance with the invention.
Fig. 11 is a sectional, elevational view of the apparatus of Fig. 10 for projecting a design pattern onto a flat image surface.
Fig. 12 is a perspective view of alternative apparatus for projecting a design pattern onto an arcuate image surface in accordance with the invention.
Fig. 13 is a perspective view of modified appara-tus for projecting a design pattern onto a flat image surface in accordance with the invention.
Generally, photoetching or selective photoplating of a surface is accomplished by applying a photoresist coating to the surface to be processed and then light-exposing that portion not to be etched or plated through a corresponding transparency or mask held in close contact -to the surface. The light-exposed resist is then fixed and the unexposed resist is dissolved. When the surface is immersed in an ~etching ox plating solution, processing will take effect s~electively only where the resist has been ~' ~ ' ` .
removed, thus producing a desired pattern. This process is readily accomplished where the surface to be processed is flat and close contact with a flat: transparency or mask can be established. However, in the case of a non-cylindrical arcuate form, it is difficult to conform the desired desiyn image to any extensive area of the ar,cuate surface by the above-described conventional techniques.
Conformance of the design image from a conven-tional flat transparency or mask to an arcuate surface is accomplished in accordance with one form of ~he present invention by projecting narrow transverse images of a,d~sign from the transparency or mask. The transverse images are received in foreshortened form by corresponding narrow radial segments of a photoresist-coated or photosensitized flat surface. Subsequent processing produces a circularly distorted pattern on a flat surface, which is suitable for forming into a desired arcuate surface bearing the design without apparent distortion. This embodiment of the in-vention also contemplates projecting the narrow transverse images directly upon a photoresist-coated arcuate surface.
Referring to Figs. 1 and 2 of the drawings, a projector 1 comprises a light box 2 provided with a suitable ~' light source 3. A parallel ray mirrored surface 4 is within the light box 2. An inclined flat mirrored surface S is positioned beneath the light box 2. A light mask 6 containing an adjustable slit opening 7 is positioned at an angle to the mirrored surface 5. 'A second inclined flat mirrored surface 8 is located on the opposite side of the light mask 6 from the first mirrored surface 5 and . . .
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is substantially parallel thereto. An adjustable focusing lens 9 is pla~ed beneath the mirrorecl surface 8 and is substantially perpendicular to the light mask 6.
Light projected in a col~ lOa from the light source 3 is directed as follows through the projector 1 First, the mirror 5 reflects the light along path lOb through the slit 7 to the mirror 8. The~, the mirror 8 redirects the light along path lOc toward the lens 9, which focuses the light. The lenS 9 may be a double convex lens or any other suitable single- or multi-element focusing lens.
~ support assembly 12, which is adjustable in height, is adapted to hold a flat, rectangular transparency or mask 13 which has been formed into a cylindrical shape having a design pattern 13a thereon. The support assembly 12 rests upon a rotatable turntable 14 whose axis 15 is coincident with the axis of the cylindrical transparency 13. A motor 16 is adapted to drive the turntable 14 through suitable drive means, e.g. a belt.
The transparency 13 is adapted to be positioned on~the support assembly 12 directly in the path of radially inwardly directed light lOb. As shown in Fig. lA, light and dark transverse images 17a corresponding to the design pattern 13a at narrow transverse areas 17b of the trans-, parency 13 are projectable in the direction of the light beam path lOb. As used herein, the term "narrow trans-verse area" means one of the many portions of the trans~
parency 13 which is exposed to the light similarly to the _g_ ` .
` ' ' ' ' 1~3'~3'~;2 well-known projection technique used for slides or photographic transparencies.
In one embodiment of the inYention, the pro-jected narrow transverse images 17a ;~re displayed upon and received as narrow radial images 18a by corresponding narrow radial areas or segments 18b of a flat, substantially circular image surface 19~ The image surface 19 is located on the turntable 14 and is disposed perpendicular to the light beam axis 15~ The flat, circular image surface 19 is provided with a photoresist coating 20. Portions of the coating 20 are adapted to be exposed to the narrow radial images 18a. When the entire flat, circular surface 19 has been exposed at the narrow radial areas 18b, an entire design pattern l9a is created on the 1atr circular image surface 19 corresponding to the flat, rectangular pattern 13a on the transparency or mask 13. ~owever, the rectangular-coordinate design pattern 13a on the trans-parency 13 has been converted to a foreshortened, polar-coordinate design pattern l9a on the circular, flat image surface 19. The term "foreshortened", as used herein,means that the design pattern l9a is smaller in size than the design pattern 13a because the design pattern l9a is stretched when the flat surface 19 is formed into an arcuate shape, e.g. a bell. The amount of foreshorten-ing is determined empirically and depends upon the arcuate shape to be produced. For example, a cup requires a sub-stantial amount of foreshortening; a shallow dish requires very little. I some distortion is desired or acceptable --10-- ~
in the final shape, it may be possible to eliminate the foreshortening.
To transfer a design for subsequent etching and/or platin~, the projector 1 is positioned relative to the flat, circular surface 19 for desired image size and amount of foreshortening. The photoresist-coatea flatt circular surface 19 is centered on the turntable 14 and positioned relative to the table index mark 21.
A first transparency or mask 13 is positioned on the carrier or support 12 relative to the carrier index mark
2~ and the lens 9 is focused upon the image surface 19.
The drive motor 16 turns the turntable 14 and the image surface 19 thereon. Concurrently, the motor 16 rotates the support assembly 12 with the transparency 13 thereon~
~he design pattern 13a comprising each of the narrow transverse areas 17b is progressively and successively projected in rotational sequence towaxd each of the corresponding radial segments 18b of the photoresist-coated image surface 19~ The narrow transverse images 17a are received as narrow radial images 18a and are exposed in rotational sequence upon the corresponding narrow radial segments 18b. Ater complete exposure, . the flat, circular surfàce 19 is removed and processed for etching or plating in the conventional manner, for example, as in V.S. Patent 3,503,815. To process a suc-cessive pattern~ a new coating of photoresist 20 is applied to the flat, circular surface 19 and the above- .
described cycle is repeated. A desired etched and/or multi-finished design is thereby produced on the flat, circular image surface 19~
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The flat, circular surface 19 may be a mask, stencil or transparency. As a transparency, the image surface 19 may be a film contained within a camera. The camera would include the equivalent ~f the lens 9 and the lens shutter would be held open. The film will be exposed to the design in foreshortened, polar-coordinate form.
After processing, the film can be used as a second trans-parency for subsequent imaging.
As a mask or transparency, the image surface 19 may be used directly in mass producing a series o~ flat, circular surfaces suitable for forming into the desired arcuate articles. Also, the flat surface 19 need not be circular, although that configuration is useful for creating certain arcuate shapes, e.g. a bell.
For preparing a larger number (or more than sev-eral) of the same-shaped surfaces with the same designs, an expeditious mass-production method desirably is employed.
The modification permits the use of a simple light source and the simultaneous exposure of all areas of a flat,~cir-cular surface once the mask has been formed. As shown inFig. 3, a flat, circular transparency or mask 25 is produced by the method and apparatus shown in Figs. 1 and 2. This mask 25 is placed over a matching flat image surface 19 - onto which a photosensitized coating 20 has been deposited.
- The transparency or mask 25 and t~e surface 19 are then exposed to a light source 26 and developed and fixed by conventional photographic means to produce an image on the surface. Transparency or mask sets may be used to produce successive, registered, circular design patterns on the '~
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fl~t, formable surface. The flat, circular surface is processed in the conventional manner by successively photoresist-coatin~, contact exposing, fixin~ or develop-ing, and etching or plating as required~ It is thereafter formed, as in Fig. 4, into the desired arcuate shape 30 bearing the desired design 30a without apparent distortion.
Masks produced in this way may also be etched through to form stencils for use in coating the arcuate surface. After positioning a stencil 25 on the flat surface 19, either a final or a resist coating 20 is applied by spray, brush or other deposition means. As a resist coat, subsequent processing for etching and/or plating would be carried out in the conventional manner.
~ n alternative form of the invention contemplates the transference of the design directly to an arcuate surface. This technique is useful when preparing a large number of objects having an unusual shape. Fig. 5 shows a method of transferring a design pattern to an outside arcuate surface and is intended to be used in conjunction with the apparatus and method of Figs. l and 2, or with the projection of a radially disposed~ 1at transparency such as would be produced therefrom. An outside mirrored conical surface 31 and an inside mirrored conical surface 32 are interposed between the lens 9 and an arcuate surface 30 bearing a photoresist coating 33. The focused light following the path lOd through the lens 9 strikes the mixrored surface 31 and is directed along path lOe toward the mirrored surface 32, which redirects the light along path lOf toward the photosensitized arcuate image ~: ' ' ': ' ' ', ~
surface 30. The mirrored surface 31 partially restores the design iMage to substantially rectangular-coordinate ~orm and to right-side-up positio~. The an~les and posi-tions of the mirrored surfaces depend upon the arcuate shape to be produced and the size thereof so that the light strikes the arcuate surface substantially perpen-dicular theretoO Thus, narrow transverse images 17a projected from the transparency 13 are received by and exposed in rotational sequence upon the photoresist-coated arcuate surfac!e 30~ or all at once in the caseof a projected, flat, radially disposed image.
Fig. 6 shows a similar method for transferring the design onto an inside arcuate surface. An outside mirrored conical surface 35, which partially restores the design image to substantially rectangular-coordinate form, is placed between the lens 9 and an inside arcuate surface 36 having a photoresist coating 37. ~ Focused light following the path lOd through the lens 9 is re-directed by the mirrored surface 35 along path lOg toward the photosensitized arcuate image surface 36. The narrow - light and dark images 17a projected from the transparency 13 are exposed in rotational sequence upon the photoresist-coate~ inside arcuate surface 36, or all at once in the case of a projectecl, flat, radially disposed image.
Another preferred embodiment of the invention is illustrated in Fig. 7. In this embodiment 9 a conical mirrored surace 40 functions as an equivalent to the inclined mirror B in the Figs. 1 and 2 embodiment. Light is projected from a suitable light source or sources 41 ~, -14- ~
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and is directed through a rectangular transparenc~ 13 or reflected from a rectangular surfclce 13, which has been formed into a cylindrical shape having the rectangular design pattern 13a thereon. Light arld dark images 17a corresponding to the design pattern 13a are projectable in the direction of the light path. The outside conical mirrored surface 40 is located on the opposite side of the transparency 13 from the light source 41 such that it redirects the light passing through the transparency - 10 13 substantially perpendicular to its initial direction.
The light reflected by the conical mirrored surface 40 is directed toward and through a lens shutter 42 of a simple camera 43 positioned along the axis of the conical mirror. The lens shutter 42 is held open to receive the entire exposure. A conventional, photosensitized film within the camera thereupon is exposed to the light and dark images 17a. However, the images received by the film are in foreshortened, polar-coordinate form. The film is fixed and processed in the conventional manner. It should be noted that a single light source 41 can be used to-gether with a light mask 6 and slit 7 ~as in Fig. 1) and either the li~ht source 41 or the transparency 13 rotated with respect to the other to project all narrow transverse images 17a toward the camera 43. Alternatively, multiple light sources 41 or a radial light source can be used to project the entire transparency simultaneously without rotation of either the light sources or the transparency.
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The processed film created by the method of ~ig. 7 may then be used in production of designs ! as is, for example, the transparency 25 (Fig. 3). The processed film also may be used as a second transparency (or set of transparencies) to transfer the design directly to an arcuate or flat surface.
In Fig. 8, there is shown method and apparatus for transferring the design from the processed film or transparency to an arcuate surface. The image on film 44 is iliuminated such that light and dark images in polar-coordinate form are reflected simultaneously along a light path 45. An outslde conical mirrored surface 46 is located ; such that it redirects the light 45 passing through the film or transparency. An inside conical mirrored surface 47 again redirects the focused light toward an arcuate image surface 48, which has been or is provided with a photosensitized resist coating 49. Thus~ light and dark images projected from the transparency or film 44 are received directly ~y the arcuate surface 4~ in relatively undistorted, rectangular-coordinate form.
Fig. 9 shows another preferred method for trans~
ferring the design from the processed transparency or film 44 directly onto the photosensitized arcuate surface 48.
In this embodiment, light and dark images projected from the transparency or film are redirected by an inside mirrored conical surface 50 direc~ly onto the arcuate image surface 48. The method of Fig. 9 eliminates the use of two mirrored conical surfaces, as in the method of Fig. 8. However; to prevent the design from being ~"~
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transferred upside-down, it is nece~sary to place the first transparency 13 (Fig. 73 upside-down when commencing the method.
Referring to Figs. 10 and ]Ll, showing an alter-native embodiment of the invention, a projector or light box 101 is provided with a light source 102, a parallel ray mirrored surface 103, an outside mirrored conical surface 104, an opposing inside mirrored conical surface 105 and a second opposing inside mirrored conical surface 106. A support 107 is adapted to hold a flat, rectangular transparency or mask 108 which has been formed into a cylindrical shape having a design pattern 108 thereon.
A second outside mirrored conical surface 110 is disposed along the axis 111 of the cylindrical transparency 108.
Light projected in a column 109 from the light source 102 is redirected first radially outward by mirror 104 along path lO9a, next downwardly by mirror 105 along path lO9b, and then radially inwardly by mirror 106 along path lO9c. The light passes through cylindrical trans-parency 108, and is recolumnated downwardly ~y mirror 110 along path lO9d. A lens 112 focuses the design on an image ; sur*ace 114. The lens 112 may be a double convex type or any other suitable single- or multi-element lens.
~arrow transverse areas 115 of the transparency 108 simultaneously are directed in the path of the radially inwardly directed l:ight lO9c. Light and dark transverse images 115a corresponding to the pattern at the respective transverse areas 115 of the transparency 108 are thereupon projected simultaneously in the direction of the light beam axis 111.
- ~ , ,, ., ' 3~2;2 In this fo~n o~ the invention, the projected narrow transverse images 115a are displayed upon and re-ceived simultaneously by corresponding narrow radial areas or segments 116 of a flat, substantially circular image surface 1140 The surface 114 is held on a table 120 disposed perpendicular to the li~ht beam axis 111.
The ~lat circular surace 114 is pro~ided with a photo-resist coating 118. Portions of the coating 118 are thereby exposed to the projected images 115a. As the entire flat, circular surface 114 is simultaneously exposed at the narrow radial areas 116, an entire design pattern 116a is created on the flat circular surface 114 corresponding to the flat recta~gular pattern 108a on the transparency or mark 108. However, the rectangular-- coordinate design pattern 108a on the transparency 108 has been converted to a foreshortened, polar-coord nate design pattern 116a.on the circular flat surface 114.
To transfer a design for s~bsequent etching and/or plating, the projector or light box 101 is posi-tioned relative to the flat, circular surface 114 for ~
desired image si2e and amount of foreshortening. The photoresist-coated flat, circular surface 114 is centered :~
on the table 120 and positioned relative to the table index mark 121. A first transparency or mask 108 is po-sitioned on the carrier or support 107 relative to the carrier index mark 122 and the lens 112 is focused upon the surface 114. The design pattern 108a comprising each o~ the transverse areas 115 is projected toward each of the corresponding radial segments 116 of the photoresist coated .. -18-. . . . . . .
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3Z;2 surface 114 and the narrow transverse images 115a are exposed upon the radial se~ments 1160 The flat, circular surface 11~ is removed and processed for etching or plating in the above-described manner.
~ nother embodiment of the ;nvention is shown in Fig. 12. A projector 201 is provided with a movable carrier 202 which is adapted to hold a transparency or mask 203 having a design pattern 203a thereon. A narrow opening or slit 204 is provided in the path of a projec-tion light 205. This narrow opening 204 is about 1/8 in.
wide~ although other size openin~s may be suitable. A
motor 208 progressively drives the carrier 202 across the path of the ligh~ 205 by means of a gear train 209.
Narrow areas 206 of the transparency 203 are progres-sively and successively moved into the path of the light 205, when registered with the narrow opening 204. Light and daxk narrow images 206a corresponding to the pattern at the respective narrow areas 206 of the transparency 203 are thereupon successively projected in the direction of the light beam axis 207.
m e projected narrow images 206a from the trans-parency are displayed upon and receivPd by corresponding narrow areas 211 of arcua~e surface 212 t e.g. a bell. The arcuate surface 212 is provided with a photoresist coating 213. Portions of the coating 213 are thereby exposed to the projected images. Aftex the entire arcuate surface has been progressively and successively exposed at the narrow areas 211, an entire design pattern 212a is created --lg.--:,, :
on the arcuate surface 212 corresponding to the flat pattern 203a on the transparency or mask 203.
The arcuate surface 212 is held up on a ro-tatable table 214 having a rotation axis 215. This axis 215 is located and tiltable in the p:lane of the projected narrow images 206a. Preferably, the axis 215 is tilted to a position such that any arcuate narrow area 211 is substantially perpendicular to the axis 207 of the pro-jected narrow images 206a. This results in each point along the length of the narrow areas 211 being within the sphere of focus. The table 214 is rotatable by a motor 216, either directly or through a gear train 217. Rota-tion of the table 214 is synchronized with the linear motion of the carrier 202 for proper positioning and exposure time of the successive narrow areas 211. Syn-~hronization can be accomplished by providing carrier speed sensing means and table speed sensing means at the respective gears 209 and 217. A controller 218 of any conventional type adjustably controls the individual and relative speeds of the carrier motor 208 and the table - motor 216. The relative speeds of the carrier 202 and the table 214 depend upon the relative sizes of the transparency ;~ ' and ar,cuate surface. If there is a l:l.size relation, the peripheral movement of the surface should equal the linear .
movement of the carrier and transparency. Successive . ;
patterns may be registered by an index mark 219 and con~,- ,.
ventional start ancl stop controls (not shown). ,:. , ~
To transfer a design for etching and/or plating;' .' .
on the arcuate surfac , the projector 201 is positioned '.. . : . . ', . -: . ................. '... , ~.: : . . . : : ' ' .
3~Z;2 xelative to and focused upon the convex arcuate sur~ace 212 for desired image size~ The photoresist-coated arcuate surface 212 is centered on the table 214 and positioned relative to the table index mark 219. A
first transparency or mask 203 is positioned on the carrier 202. Synchronized motion of the carri~r 202 and the table 214 is initiated and continued through a complete exposure of successive narrow images 206a of the pattern on the photoresist coated surface 212.
10 The arcuate sur~ace 212 is removed and processed for et¢hing or plating in the above-described manner.
The apparatus of Fig. 12 also is adapted for inside or concave surface processing using a mirror positioned neax the rotation axis, in line with the - projected narrow images 206a and at a 45 angle to the axis 207 of the projected narrow images; such that the projected narrow images 206a are reflected by the mirror along their full height and are displa~ed upon and re-ceived by corresponding narrow areas on the inside surface. The rotation axis is tilted such that the reflected projection beam axis is substantially per-pendicular to the inside arcuate surface narrow area.
In another embodiment of the invention shown in Fig. 13, the projector 201 is the same as ~he pro-jector shown in Fig. 12. However, the projected narrow images 206a are displayed upon and received by corre-sponding narrow radial areas or segments 251 of a flat, substantially circular surface 252 suitable for forming ; into an arcuate surface, e~g. a bell. The flat circular ~ .~
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surface 252 is provided with a photoresist coating 253.
Portions o~ the coating 253 are thereby exposed to the projected images. After the entire ~Elat, circular surface has been progressively and successively exposed at the narrow radial areas 251, an entire design pattern 252a is created on the flat circular surface 252 corresponding to the flat rectangular pattern 203a on the transparency or mask 203. However, the rectangular-coordinate design pattern 203a on the transparency 203 has been converted to a foreshortened, polar coordinate design pattern 252a on the circular flat surface 25~.
The flat, circular surface 252 is held up on a rotatable table 254 having a rotation axis 255. ~his axis 255 is parallel to the light beam axis 207 and perpendicular to the transparency 203 and surface 252. The distance of the surface 252 from the transparency 203 is adjustable to provide the required amount of foreshortening. The table 254 is rotatable by a motor 256, either directly or through a gear train 257. Rotation o~ the table 254 is synchron-ized with the linear motion of the carrier 2~2 for properpositioning and exposure time of the successive narrow areas 251. Synchronization can be accomplished as described with reference to Fig3 12. The relative speeds of the carrier 202 and the table 254 depend upon the relative sizes of the transparency and flat, circular surface. If there is a 1:1 size relation, the peripheral movement of the flat, circular surface should equal the linear movement of the carrier and transparency.
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To transfer a design for subsequent etching and/or plating, the projector 201 is positioned relative to and focused upon the flat, circular surface 252 for desired image size and amount of oreshortening. The photoxesist-coated flat, circular surface 252 i5 centered on the table 254 and positioned relative to the table index mark 219. A first transparency or mask 203 is po-sitioned on the carrier 202. Synchronized motion of the carrier 202 and the table 254 is initiated and continued through a complete exposure of successive narrow transverse images 206a o the pattern on the photoresist-coated sur-face 252. The flat, circular surface 252 is removed and processed for etching or plating in the above-described manner.
The above descriptions are intended to be illustrative of methods for conforming a flat, rectangular-coordinate design pattern to a corresponding polar-coordinate flat design pattern suitable for formation into a desired arcuate surface bearing the design in proper proportion without apparent distortion~ Alternatively, the design may be transferred either directly to an arcuate surface or from the polar-coordinate design pattern without appar-ent distortion. The present invention has substantial use in the production of bowls, bells, jewelry and other decorated items having an arcuate or other ixregular surface. The word "arcuate" as used herein is intended to mean irregular, non-flat surfaces of various sizes and shapes. Many other uses of the invention will be apparPnt to those working in this and related fields.
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