GB2038698A - Aspherical optical elements - Google Patents
Aspherical optical elements Download PDFInfo
- Publication number
- GB2038698A GB2038698A GB7850127A GB7850127A GB2038698A GB 2038698 A GB2038698 A GB 2038698A GB 7850127 A GB7850127 A GB 7850127A GB 7850127 A GB7850127 A GB 7850127A GB 2038698 A GB2038698 A GB 2038698A
- Authority
- GB
- United Kingdom
- Prior art keywords
- polymeric material
- profile
- aspherical
- glass substrate
- substrate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 230000003287 optical effect Effects 0.000 title claims abstract description 43
- 239000000463 material Substances 0.000 claims abstract description 49
- 239000000758 substrate Substances 0.000 claims abstract description 48
- 238000000034 method Methods 0.000 claims abstract description 35
- 239000011521 glass Substances 0.000 claims abstract description 29
- 238000000576 coating method Methods 0.000 claims abstract description 14
- 239000011248 coating agent Substances 0.000 claims abstract description 11
- 230000001788 irregular Effects 0.000 claims abstract description 4
- 229920005989 resin Polymers 0.000 claims description 19
- 239000011347 resin Substances 0.000 claims description 19
- 238000000465 moulding Methods 0.000 claims description 16
- 239000007787 solid Substances 0.000 claims description 7
- 239000011888 foil Substances 0.000 claims description 4
- 239000007788 liquid Substances 0.000 claims description 4
- 229920001169 thermoplastic Polymers 0.000 claims description 3
- 239000004416 thermosoftening plastic Substances 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 12
- 230000007547 defect Effects 0.000 abstract description 4
- 238000000227 grinding Methods 0.000 abstract description 3
- 239000003822 epoxy resin Substances 0.000 abstract description 2
- 238000003754 machining Methods 0.000 abstract description 2
- 229920000647 polyepoxide Polymers 0.000 abstract description 2
- 238000005266 casting Methods 0.000 abstract 1
- 230000000699 topical effect Effects 0.000 abstract 1
- 229920001187 thermosetting polymer Polymers 0.000 description 14
- 230000000694 effects Effects 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000003801 milling Methods 0.000 description 2
- 238000005498 polishing Methods 0.000 description 2
- 229920006352 transparent thermoplastic Polymers 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 239000004606 Fillers/Extenders Substances 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 229920006397 acrylic thermoplastic Polymers 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000001723 curing Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 239000003085 diluting agent Substances 0.000 description 1
- 238000007519 figuring Methods 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- LNEPOXFFQSENCJ-UHFFFAOYSA-N haloperidol Chemical compound C1CC(O)(C=2C=CC(Cl)=CC=2)CCN1CCCC(=O)C1=CC=C(F)C=C1 LNEPOXFFQSENCJ-UHFFFAOYSA-N 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 238000013035 low temperature curing Methods 0.000 description 1
- VIKNJXKGJWUCNN-XGXHKTLJSA-N norethisterone Chemical compound O=C1CC[C@@H]2[C@H]3CC[C@](C)([C@](CC4)(O)C#C)[C@@H]4[C@@H]3CCC2=C1 VIKNJXKGJWUCNN-XGXHKTLJSA-N 0.000 description 1
- 229920003229 poly(methyl methacrylate) Polymers 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920000515 polycarbonate Polymers 0.000 description 1
- 239000004417 polycarbonate Substances 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000012260 resinous material Substances 0.000 description 1
- -1 spherical or flat Substances 0.000 description 1
- ISXSCDLOGDJUNJ-UHFFFAOYSA-N tert-butyl prop-2-enoate Chemical compound CC(C)(C)OC(=O)C=C ISXSCDLOGDJUNJ-UHFFFAOYSA-N 0.000 description 1
- 229920005992 thermoplastic resin Polymers 0.000 description 1
- 238000007514 turning Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D11/00—Producing optical elements, e.g. lenses or prisms
- B29D11/0073—Optical laminates
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D11/00—Producing optical elements, e.g. lenses or prisms
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D11/00—Producing optical elements, e.g. lenses or prisms
- B29D11/00009—Production of simple or compound lenses
- B29D11/00019—Production of simple or compound lenses with non-spherical faces, e.g. toric faces
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C39/00—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor
Landscapes
- Engineering & Computer Science (AREA)
- Health & Medical Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Ophthalmology & Optometry (AREA)
- Mechanical Engineering (AREA)
- Casting Or Compression Moulding Of Plastics Or The Like (AREA)
- Surface Treatment Of Glass (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
- Lining Or Joining Of Plastics Or The Like (AREA)
Abstract
A method of producing an aspherical optical element comprising a light transmissive glass substrate having an irregular surface finish with a profile which follows in part a desired aspherical profile and a coating of a light transmissive polymeric material thereon. The glass substrate 2 is first prepared with the part aspherical profile 3 for example by casting, machining or grinding and then the substrate is supported in a mould tool in close proximity to an optically polished surface of a negative profile of the desired aspherical profile. The region between the facing surfaces of the glass substrate and mould is filled with the polymeric material 1 and the polymeric material is bonded to the surface of the glass substrate. Thereafter the topical element thus formed is released from the mould tool. The surface of the glass substrate may be produced in the first process stage by mass production methods using automatically controlled machine tools. The surface may have a tolerance defect band width of not less than 400 microns and the polymeric coating material may comprise an epoxy resin of between 100 and 450 microns thickness. <IMAGE>
Description
SPECIFICATION
Aspherical optical elements
This invention relates to a method of producing aspherical optical elements which comprise a light transmissive glass substrate with a coating of a light transmissive polymeric material thereon.
It is well known in the art than optical designers have long been inhibited in specifying optical designs which incorporate aspherical optical elements because of difficulties in producing large numbers of accurately profiled, optically polished, aspherical elements. Methods of producing high quality optical elements in large quantity production have hitherto been restricted to either the production of glass optical elements with spherical surfaces or to composite optical elements comprising glass substrates coated with a resinous material in which the glass substrate has a flat or a spherical surface form.
Aspherical optical elements which comprise a flat or a spherical light transmissive glass substrate with a layer, the outer surface of which is aspheric, of a light transmissive thermosetting resin thereon, are known from United Kingdom Patent No.1,301,551.
In this patent the glass substrate is pre-prepared by being machined, ground and polished to a convenient flat or spherical form and an accurately made, hand finished, mould tool with a moulding surface having a negative profile in cross-section of a desired aspheric profile, is used in a moulding process to mould a layer of the thermosetting plastics material thereon so that the outer surface has the desired aspherical form.
The difference in form between the pre-prepared profile of the glass, spherical or flat, substrate and the hand finished negative aspherical profile of the moulding surface of the mould tool is taken up by variations in the thickness of the thermosetting resin.
Aspherical optical elements of the aforesaid kind are subject to a number of disadvantages. The optical elements, for example, have the whole of their asphericity accommodated in the coating of the thermosetting resin. Consequently, the resin layer is
often relatively thick. In the case of an aspherical
optical element with a steeply profiled aspherical
form this thickness may amount to several milli
meters. It is frequently advantageous to have an
aspherical optical element with only a thin coating of
a light transmissive material the outer surface of which is aspheric. Thus, it has been found that
optical elements which have the whole of their
asphericity accommodated by the coatings require,
in general, a correspondingly thick substrate in
order, to reduce the effect of distortion due to the
bonding of dissimilar materials to each other.
Distortion, for example, will prevent the effective
use of such optical elements. The effects of distor
tion is greatest over wide temperature changes and
distortion may occur during the temperature
changes produced during manufacture as well as
during the use of the finished product.
Shrinkage of a comparatively thick resin coating
on curing also causes a loss in optical efficiency unless the shrinkage is uniform and can be compensated for.
Furthermore, shrinkage of a resin can cause considerable forces to be exerted on the substrate which may cause the surface of the substrate to fracture. These disadvantages have previously limited the range of light transmissive resins of thermosetting resins. Thermosetting resins of thicknesses of several millimeters thick, have a further disadvantage in that they require a low temperature cure to minimise the effects of distortion resulting in a long processing time.
Relatively thick coatings of this type therefore do not lend themselves to the production of optical elements on a large scale production run.
One object of the present invention is to provide an improved method of producing an aspherical optical element which mitigates the aforesaid disadvantages.
Another object of the invention is to provide a method by which a wider range of light transmissive materials, for example of thermosetting resins and/ or of thermoplastic resins, can be used as a coating material.
A still further object of the invention is to provide a method by which aspheric optical elements can be manufactured cheaply by mass production methods and wherein said optical elements are consistent in quality of both the surface finish and the profile form.
According to the present invention there is provided a method of producing an aspherical optical element comprising a light transmissive glass substrate with a coating of a light transmissive polymeric material thereon, characterised in that the glass substrate is formed in a first process phase with at least one surface which has an irregular surface finish and a profile which, in part, follows the profile of a desired aspherical profile and in that the polymeric material is bonded to the surface of the substrate in a second process phase so that the surface of the polymeric material accommodates the remaining part of the desired asphericity and provides an overall desired optical surface finish thereon, wherein the glass substrate is supported in a mould tool with the aspherical profile part of the surface of the glass substrate in close proximity to a moulding surface having a negative profile of the desired aspherical profile, said negative profile having a smooth, optical polished surface finish, filling the region between the said two surfaces with the polymeric material, bonding the material to the surface of the glass substrate whilst moulding the polymeric material to form the desired aspherical profile and surface finish followed by releasing the optical element from the moulding tool.
The optical elements of the invention may be used without loss of optical efficiency over a wide range of temperatures from, for example, -50 C to + 100"C.
The manufacturing time, even when thermosetting resins are used, is reduced and the finished product is not as subject to the distortion effects referred above or to as great the stress forces produced on shrinkage of the resins as is produced by the thicker coatings of thermosetting resins.
In one embodiment of the method the surface of the substrate is supported in the moulding tool at a closest distance of not less than 100 Ftm from the negative aspherical surface of the mould tool and at a farthest distance of not more than 500 ltm from the negative aspherical surface of the mould.
The substantially aspherical part of the surface of the substrate and the non aspherical part of the surface of the substrate both being previously machined and or cast to the appropriate form but not necessarily polished. The surface may therefore have a series of irregularities which can vary between not less than t 200 um of the profile.
After positioning the substrate in the moulding tool the region between the two surfaces can be filled with a polymeric material in a liquid form and the polymeric material is bonded to the surface of the substrate by causing the material to harden.
When the polymeric material is hardened the optical element is released from the mould by the application of a lateral separating force.
A release agent may be used on the surface of the mould tool In order to ensure easy release on hardening of the polymeric material. Alternatively, an evaporated inert metal layer or of amorphous carbon may be deposited on the surface of mould tool to cause a parting layer on hardening the polymeric material.
In an alternative embodiment of the method the region between the two surfaces is filled with a mouldable, solid polymeric material, for example, in foil form, and the polymeric material is bonded to the surface of the substrate by the application of heat and pressure. The substrate may in this case be brought to the desired position wherein the closest point is a distance of not less than 100 tim and at the farthest point is a distance of not more than 500 ttm from the negative aspherical surface by deforming the mouldable, solid polymeric material.On deforming the solid polymeric material it becomes bonded to the machined or ground surface of the substrate in preference to the polished surface of the mould tool which may also be treated with a release agent or have a partinq metal or carbon layer coated thereon.
As indicated above the substrate can be produced by automatic methods with a cast, machined or ground surface which closely approximates the desired aspherical profile at least in a part of its surface and the mould tool has a negative of the desired aspherical profile surface and an optical surface finish which is commonly produced by skilled workers using traditional cut and try techniques as for example, used in figuring paraboloids for use in astronomy. The automatic methods of producing the surface profile on the substrate is subject to certain infects for optical purposes both in the aspherical profile produced and irregularities of the surface finish.It has been found that these defects can not be eliminated even when the cutting, grinding and or polishing tools are controlled by a cam or a programmed controlling device, such as, a programmed punched tape. With regard to the surface profile a tolerance defect band of 400 tim or t 200 +m of a programmed profile is usual. It is therefore possible in large quantity production to produce only a part of the total desired aspheric profiled surface to within the aforesaid tolerance defect band limits.
In a further embodiment the glass substrate is cast, or machined and ground, to a surface profile which at least in part has an irregular surface finish which varies between + 200 tim of the desired aspherical surface profile part.
The region between the two surfaces of the substrate and the negative aspherical profile of the moulding tool it not less than 100 itm if direct contact between the two surfaces is to be avoided.
Conveniently the region between the two said surface is such that the polymeric material filling the region has a thickness which is between 100 to 150 itm at the thinnest part and is between 400 to 450 itm at the thickest part.
The polymeric materials which may be used as the light transmissive polymeric material is dependent upon the durability and optical performance of the resultant optical element. A wide range of transpa rent thermoplastics and thermosetting materials are suitable. Transparent thermoplastics and thermosetting materials, such as epoxy resins, polyesters, polyamides, polycarbonates and acrylics are particularly suitable.
The thermosetting resins may be cured from a liquid state to form a solid transparent polymeric coating which has good adhesion to glass, good mechanical properties, low thermal expansion coefficient and a good resistance to water. The resins selected should also have a good resistance to deterioration on exposure to ultra violet light radiations and a good reproducibility of their refractive index properties. Fillers, diluting agents and extenders may be used in the resins but preferably such additives should be kept below 10% by weight.
Suitable thermoplastics resins and thermosetting resins in the solid form when used must be capable of being moulded to take up the appropriate shape between the mould tool and the substrate during manufacture. Solid thermoplastics or thermosetting materials if mouldable are preferably used in the form of a foil of thickness greater than 500 tim and not less than 100 tim.
Embodiments of the invention will now be described by way of example, in which Figure 1 illustrates an enlarged cross-sectional view which is not drawn to scale of an aspherical optical element when prepared by the method according to the invention.
A polymeric coating 1 is bonded to the surface of a glass substrate 2. The glass substrate 2 was formed in a first process phase by conventional, cheap production techniques by machining, grinding, turning and or milling a glass blank until it had a surface with a profile 3.
The surface of profile 3 has a shape which approximates, as close as it is possible to achieve by the conventional production techniques, to the required ashperic shape of profile 4. The profile 3 made by these methods was sufficiently accurate to follow the required profile 4 over a part of its surface as indicated by 5,5' within the undermentioned limits. The profile 3 deviates from the required profile 4 over the remaining part of its surface as indicated by the broken line 6,6'. As the surface of profile 3 was produced by conventional production techniques the surface has limiting irregularities in its surface profile. These irregularities are critical and are within the range oft 200 ttm of the indicated profile 3 even when the greatest of care is taken, for example, when using automatically controlled and programmed milling and polishing machines, and
Figure 2 illustrates in three parts an enlarged cross-sectional view, which is not drawn in scale, of an alternative embodiment of an optical element when prepared by the method according to the invention. The reference numerals of Figure 2 indicates similar features to the reference numerals of
Figure 1 with the exception that the profile 3 of substrate 2 differs from the required profile 4 at the additional points 5IIl and 5"' in the cross-section shown.
Claims (10)
1. A method of producing an aspherical optical element comprising a light transmissive glass substrate with a coating of a light transmissive polymeric material thereon, characterised in that the glass substrate is formed in a first process phase with at least one surface which has an irregular surface finish and a profile which, in part, follows the profile of a desired aspherical profile and in that the polymeric material is bonded to the surface of the substrate in a second process phase so that the surface of the polymeric material accommodates the remaining part of the desired asphericity and provides an overall desired optical surface finish thereon, wherein the glass substrate is supported in a mould tool with the aspherical profile part of the surface of the glass substrate in close proximity to a moulding surface having a negative profile of the desired apherical profile, said negative profile having a smooth, optically polished surface finish, filling the region between the said two surfaces with the polymeric material, bonding the material to the surface of the glass substrate whilst moulding the polymeric material to form the desired spherical profile and surface finish followed by releasing the optical element from the moulding tool.
2. A method of producing an aspherical optical element according to Claim 1 characterised in that the surface of the substrate is supported in the mould tool at a distance of not less than 100 um from the asphencal surface of the moulding tool at its closest point and at a distance of not more than 500 lim from the aspherical surface of the moulding tool at its farthest point.
3. A method of producing an aspherical optical element according to Claim 1 or Claim 2 characterised in that the region between the two surfaces is filled with a polymeric material in a liquid form and the polymeric material is bonded to the surface of the substrate by causing the polymeric material to harden.
4. A method of producing an aspherical optical element according to Claim 1 or Claim 2 characterised in that the region between the two surfaces is filled with a solid mouldable polymeric material in foil and the polymeric material is bonded to the surface of the substrate by the application of heat and pressure.
5. A method according to any of the preceding claims characterised in that the glass substrate is cast, or machined and ground, to a surface accuracy with a surface irregularity which varies within the limits oft 200 um of the desired aspherical surface profile part.
6. A method according to any of the preceding claims characterised in that the polymeric material filling the region between the two said surfaces has a thickness which is between 100 to 450 um at its thickest part.
7. A method according to claim 3 characterised in that the polymeric material in liquid form is an expoxy resin.
8. A method according to claim 4 characterised in that the mouldable polymeric material is a foil of thermoplastics material of thickness greater than 100 ttm and on moulding the polymeric material an upsetting operation occurs which results in polymeric material moving from the closets points between the two surfaces to the farthest points between the two surfaces of the glass substrate and the negative profile of the moulding tool.
9. An aspherical optical element when produced by the method according to any one of Claims 1 to 10.
10. A method of producing one or more aspherical optical elements as claimed in Claim 1 substantially as hereinbefore described.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7850127A GB2038698A (en) | 1978-12-28 | 1978-12-28 | Aspherical optical elements |
| GB7916961A GB2040785B (en) | 1978-12-28 | 1979-05-16 | Producing polymer glass asherical optical elements |
| US06/103,681 US4319945A (en) | 1978-12-28 | 1979-12-14 | Method of producing aspherical optical elements |
| EP79200778A EP0014783A1 (en) | 1978-12-28 | 1979-12-18 | Method of producing aspherical elements and products obtained thereby |
| JP16955879A JPS5591633A (en) | 1978-12-28 | 1979-12-27 | Preparation of aspheric surface optical element |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB7850127A GB2038698A (en) | 1978-12-28 | 1978-12-28 | Aspherical optical elements |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2038698A true GB2038698A (en) | 1980-07-30 |
Family
ID=10501967
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB7850127A Withdrawn GB2038698A (en) | 1978-12-28 | 1978-12-28 | Aspherical optical elements |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5591633A (en) |
| GB (1) | GB2038698A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL9401913A (en) * | 1993-11-17 | 1995-06-16 | Asahi Optical Co Ltd | Composite optical elements of the reflection type. |
-
1978
- 1978-12-28 GB GB7850127A patent/GB2038698A/en not_active Withdrawn
-
1979
- 1979-12-27 JP JP16955879A patent/JPS5591633A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL9401913A (en) * | 1993-11-17 | 1995-06-16 | Asahi Optical Co Ltd | Composite optical elements of the reflection type. |
| US5717532A (en) * | 1993-11-17 | 1998-02-10 | Asahi Kogaku Kogyo Kabushiki Kaisha | Reflection-type compound optical elements |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5591633A (en) | 1980-07-11 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |