GB2162333A - Recording spatially modulated light patterns - Google Patents
Recording spatially modulated light patterns Download PDFInfo
- Publication number
- GB2162333A GB2162333A GB8418632A GB8418632A GB2162333A GB 2162333 A GB2162333 A GB 2162333A GB 8418632 A GB8418632 A GB 8418632A GB 8418632 A GB8418632 A GB 8418632A GB 2162333 A GB2162333 A GB 2162333A
- Authority
- GB
- United Kingdom
- Prior art keywords
- layer
- temperature
- liquid crystal
- smectic
- crystal layer
- 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.)
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Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/132—Thermal activation of liquid crystals exhibiting a thermo-optic effect
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
- B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
- B41M5/00—Duplicating or marking methods; Sheet materials for use therein
- B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
- B41M5/28—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using thermochromic compounds or layers containing liquid crystals, microcapsules, bleachable dyes or heat- decomposable compounds, e.g. gas- liberating
- B41M5/281—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used using thermochromic compounds or layers containing liquid crystals, microcapsules, bleachable dyes or heat- decomposable compounds, e.g. gas- liberating using liquid crystals only
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- Physics & Mathematics (AREA)
- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Optics & Photonics (AREA)
- Nonlinear Science (AREA)
- General Physics & Mathematics (AREA)
- Liquid Crystal (AREA)
Abstract
A smectic liquid crystal layer 15 in the vicinity of or just below its isotropic phase transition temperature is illuminated with a spatially modulated pulse of high intensity radiation whose absorption gives rise to the formation of an equivalent thermal image. The radiation intensity is such that at least parts of the layer are taken by the radiation into the isotropic phase. During the ensuing cooling of the layer an electric field is applied. Those areas which have already reverted to the smectic phase remain optically scattering while those still in the isotropic remain optically clear when reverting to the smectic phase and thus the thermal image becomes 'frozen'. The initial temperature of the smectic liquid crystal layer is set by application of a pulse of light to the layer, or by ohmic heating of electrodes 13, 14, or by a combination of both. <IMAGE>
Description
SPECIFICATION
Recording spatially modulated light patterns
This invention relates to the recording of spatially modulated light patterns in smectic liquid crystal cells, and finds particular though not necessarily exclusive application in the recording of holograms in such cells. For the purposes of this specification the term 'light' is used in its broad sense that includes, not only electromagnetic radiation at wavelengths within the visible part of the spectrum, but also electromagnetic radiation at wavelengths on either side thereof.
It is already known that smectic display cells can be addressed thermally by writing with a focussed laser beam. The liquid crystal layer is temperature stabilised to a temperature in the vicinity of its isotropic transition temperature, and in this instance to a temperature that is a few degrees Celsius below that transition temperature. A impulse of laser light, typically of about 20 micitoseconds duration, locally heats the elemented volume in the liquid crystal layer upon which it is focussed to an extent sufficient to convert that localised region of the layer into the isotropic phase.
After the light pulse has terminated, or the light has been directed to another point in the cell, the elemental volume cools back into the smectic phase. If this cooling proceeds in the absence of any applied electric field across the thickness of the liquid crystal layer, then the elemental volume will relax back into a smectic phase state which is optically scattering. If on the other hand it cools in an electric field of sufficient magnitude, then it will relax back into a different smectic phase state which is optically clear. Cooling back into the smectic phase typically takes in the region of 200 microseconds.
The present invention is also concerned with thermal addressing but, whereas the above-described laser scanning technique is essentially a serial technique which requires temporal modulation of the laser beam intensity to build up an image over the period of a complete scan, the present invention is concerned with thermal addressing on a parallel basis.
According to the present invention there is provided a thermally excited positive dielectric anisotropy smectic liquid crystal display device including an internally electroded smectic liquid crystal display cell, means for setting the temperature of the liquid crystal layer of the cell to a temperature in the vicinity or significantly beneath its isotropic phase transition temperature, means for illuminating the layer with a spatially modulated light pattern whereby the temperature of at least the relatively more highly illuminated regions of the layer are raised by optical absorption to temperatures above the isotropic phase transition temperature, and means for applying a potential between the electrodes of the cell to develop an electric field through the thickness of its liquid crystal layer.
The invention also provides a method of recording a spatially modulated light pattern in a positive dielectric anisotropy smectic liquid crystal cell which method includes the steps
of setting the temperature of the liquid crystal layer of the cell to a temperature in the vicinity of, or significantly beneath its isotropic phase transition temperature,
of exposing the layer to a pulse of said spatially modulated light pattern, whereby the temperature of at least the relatively more highly illuminated regions of the layer are raised by optical absorption to temperatures above the isotropic phase transition temperature.
and of cooling the layer to a temperature in the smectic phase range, after the beginning of which cooling step a voltage pulse is applied across the thickness of the layer which voltage pulse commences at a time after the termination of the light pulse and before the entire layer has cooled into the smectic state, whereby said relatively more highly illuminated regions of the layer are caused to relax back into an optically clear smectic phase state while other less highly illuminated regions of the layer, having, before the commencement of the voltage pulse, relaxed into the smectic phase state that is optically scattering, remain in that optically scattering smectic phase state.
There follows a description of the recording of a hologram in the liquid crystal layer of a smectic cell using methods embodying the invention in preferred forms.
The description refers to the accompanying drawings, in which:
Figure 1 is a schematic cross-section of a smectic liquid crystal cell,
Figure 2 is a diagram of the temperature profile across the thickness of the cell when subjected to a preheating light pulse, and
Figure 3 is a diagram of the temperature profile across the thickness of the cell when subjected to an ohmic preheating pulse applied to the cell electrodes.
Referring to Fig. 1 a liquid crystal cell is formed by sealing together two sheets 10, 11 with a perimeter seal 1 2. The inward facing surfaces of the two sheets are provided with electrode layers 1 3 and 14 respectively. At least one of the sheets and its electrode layer are transparent. The two sheets and the peripmeter seal combine to form an envelope of well-defined thickness which is filled with a liquid crystal material to provide a liquid crystal layer 1 5 of well defined thickness. Typically the liquid crystal filling will be one exhibiting a smectic A phase, but materials exhibiting other smectic phases, may alternatively be used, particularly those exhibiting the smectic phase.Uniformity of thickness of the layer may be assisted, particularly in the case of the large area cells, by the trapping of a scattering of short lengths of glass fibre (not shown) of uniform diameter between the two electroded pulses. (In certain instances it may be desirable to provide electrically insulating layers (not shown) to cover the electrode layers and prevent direct electrical contact between them and the liquid crystal layer.)
Since the liquid crystal layer 1 5 is to be heated by incident light, either it must absorb that light, or it must be heated by conduction by material in close contact with that layer that absorbs the light. Preferably it is the liquid crystal layer itself which is arranged to absorb the light because in this way the problems of impaired resolution resulting from lateral thermal spreading effects are not so severe.If the cell is to be illuminated with light of one wavelength for recording purposes, and with light of a different wavelength for viewing purposes, it is possible to incorporate an isotropic dye for absorbing the recording wavelength light, provided that the dye does not absorb significantly at the viewing light wavelength. In many sitations however, the same wavelengths will be used for both recording and viewing, in which case a pleochroic dye is incorporated into the liquid crystal layer. This will be effective in absorbing the recording wavelength light provided that the liquid crystal material is in the isotropic state or in the optically scattering focalconic smectic phase state, but will not be absorbed to any appreciable extent when the material is in the homeotropically aligned optically clear smectic phase state.For a holographic application, the finding of a suitable pleochroic dye is simplified by the fact that generally it will be required to absorb only at one sharply defined wavelength, whereas for a typical display application the dye will need to absorb over the whole of the visible spectrum in order to appear black.
For use in recording a hologram the cell incorporating a pleochroic dye in its liquid crystal layer may be placed in the spatial frequency or Fourier transform plane of a
Vander Lugt íilter and temperature stabilised to a temperature a few degrees below the isotropic transition temperature. Ohmic heat
ing for this temperature stabilisation is provided by passing an electric current through each electrode layer 13, 14 from one side edge to the opposite.
Prior to this temperature stabilisation the whole liquid crystal layer needs to be in the scattering state so that the dye can absorb the
light later to be directed upon it. One way of providing this scattering state is to use the ohmic heating to provide a temperature pulse to cause the layer to make an excursion into the isotropic state and relax back again into the smectic state in the absence of an aligning field. Alternatively, if the liquid crystal layer is suitably doped, it may be set into the scattering state by using its electrodes to induce electrohydrodynamic stability within the layer.
The resulting dynamic scattering state will relax back into a static scattering state which is focal conic. A certain disadvantage to this approach is that restricts the range of dyes that are compatible with the system because, not only does the dye have to be stable against photochemical degradation, but also against electrochemical degradation having regard to the relatively high field strengths and current densities involved in inducing electrohydrodynamic instability. Some examples of dyes which are relatively resistant to these effects are described in the specification of our Patent Application No. 8416416 (identified by us as D. Coates 14).
Once the temperature has been stabilised the cell is ready for recording a 'page' of information, or in the case of a volume hologram several pages. For this purpose the cell is illuminated with the Fourier transforms of the reference beam and the page or pages of information. For a volume hologram these pages will be set at different angles to the reference axis of the system. illumination is provided by a very high energy pulse of coherent light which is applied to the system and split between the reference beam and the illumination of the material to be recorded.
This pulse typically lasts for no longer than 10 to 20 microseconds, and its energy density is required to be sufficient in that time for the optical absorbtion occurring in the illuminated areas of the liquid crystal layer to cause the temperature of those regions to rise from the stabilisation temperature to temperatures above the isotropic transition temperature. Local variations in illumination intensity across the area of the liquid crystal layer that results from interference effects between the reference and 'data' beams produces correspond
ing variation in the temperature of the layer at the end of the illumination pulse. Very
brightly illuminated regions will be well above the mean temperature of the layer while the
least brightly illuminated regions may still
remain beneath the isotropic transition tem
perature.
At the end of the light pulse the layer is
allowed to cool as quickly as possible, and
hence the ohmic heating for temperature sta
bilisation is terminated coincident with the
end of the light pulse. Rapid cooling is highly
desirable so that lateral heat flow within the
liquid crystal layer is minimised because such
flow reduces the resolution of the record. The
least intensely illuminated and hence initially
cooled regions of the liquid crystal layer are the first to revert into the smectic phase. In the absence of any applied field this reversion is into the focal conic state which is optically scattering.Shortly after commencement of the rapid cooling, at some instant in time by which some, but not all of the liquid crystal layer has reverted into the optically scattering smectic state, a voltage is applied between the two electrode layers to set up an electric field across the thickness of the liquid crystal layer that is strong enough to induce homeotropic alignment of any regions reverting to the smectic phase while that field is maintained. This field is maintained until the whole of the liquid crystal layer has reverted to the smectic phase. Those regions that revert in the presence of the field remain optically clear during their reversion, but the applied field is designed to leave in an optically scattering focal conic state those regions that have reverted in that state before the field is applied.
The appropriate temperature at which to stabilise the cell before it is illuminated with the light pulse depends primarily upon the power available in that light source. If that power is relatively small the temperature needs to be very close beneath, or perhaps even just above the isotropic phase transition temperature so that there is sufficient power to create the requisite isotropic spatial temperature field.The relatively high initial temperature of the cell does however militate against its rapid cooling immediately after exposure to the light pulse, and hence, because rapid cooling is highly desirable in order to minimise the lateral heat spreading effects which will impair resolution, it is desirable to work at as low a temperature as is possible consistent with there being sufficient energy in the light pulse to generate the requisite spatial temperature field in the isotropic phase.
Assuming a density for the liquid crystal medium of 0.95 gm cm-3, and a specific heat of 0.17 cal gm-1 C-l, and also assuming no heat loss during illumination, it is calculated that a 1 2 micron thick layer will require an energy input of 0.81 x 10-3 Joules/cm2 to raise its temperature by one degree Celsius.
The turning off of the ohmic heating temperature stabilisation current after exposure of the liquid crystal layer to the laser pulse is only significant if the heat loss in a time of the order of 10 microseconds is comparable with the heat input. Maximising the heat loss will normally involve subjecting the outward facing surfaces of sheets 10 and 11 to some form of forced cooling. Typically the size of smectic cell used for this application will have a display area in the region of 1 Ocm by 1 Ocm which size of cell can readily be made using glass sheets no more than 1 mm thick for the sheets 10 and 11.Assuming a value of 10-2
Joules sec-1 cm-1 C-1 for the thermal conductivity of the glass, an ambient temperaure of 30"C, and a stabilisation temperature of 60"C, it can be shown that the heat loss through both sheets will amount in total to 6
Joules per cm2, that is 0.06 X 10-3 Joules in 10 microseconds, a quantity that is small compared with the power input to raise the mean temperature of the liquid crystal layer by say 4"C. For the purposes of the above computation it was also assumed that, on cessation of heating, heat flow to the outer surface remains substantially constant for the duration in question.Thus the heat generated by the ohmic heating will, to a first approximation be equal to the heat flow from the liquid crystal to cell wall interface region of the removal of heating.
Better materials from which to make the sheets 10 and 11 are quartz (7 to 1 2 times the thermal conductivity of glass), rutile (9 to 1 3 times the thermal conductivity of glass) and sapphire (20 to 30 times the thermal conductivity of glass). For a reflective system in which only one of the sheets 10 and 11 is transmissive while the other is reflective, copper has a thermal conductivity about 40 times that of glass, but against this it must be remembered that only one of the sheets can be made of copper. Potentially copper offers a further advantage in that a sheet of copper can be thinner than its glass, quartz, rutile, or sapphire equivalent, and it is easier to fabricate with stiffening ribs.
From the foregoing it is evident that it will generally be preferable for the two sheets 10 and 11 confining the liquid crystal layer to be maintained at as low a temperature as possible consistent with the requirement that the power in the pulse of coherent illumination is sufficient to take at least the more brightly illuminated regions of the liquid crystal layer into the isotropic phase. In this context it should be appreciated that a potential lowering of the sheet temperature is possible if the pulse of coherent illumination possessing the required spatial information is preceded by a pulse of spatially uniform brightness, The earlier pulse in this way forms a kind of temperature 'pedestal' for the information content of the later pulse.A potential limitation of this approach is that the first pulses disturbs the thermal equilibrium in such a way that heat will immediately start to leak away from the liquid crystal layer into the two confining sheets, and thus produce a non-uniform temperature profile measured through the thickness of the layer as depicted in the diagram of
Fig. 2.
An alternative way of providing a temperature pedestal for the spatially modulated light pulse is given by pulsing the ohmic heating current through the elctrode layers 1 3 and 14 on the confining sheets 10 and 11. This will produce a temperature profile of the general shape depicted by the curve 30 in the diagram of Fig. 3. In this instance a slight lapse of time between the ohmic heating pulse and the spatial information containing light pulse is beneficial because the thermal spreading effects will tend to smear out the temperature profile measure through the thickness of the liquid crystal layer to give the general shape depicted by the curve 31. Thus if pulsed ohmic heating is used to produce the requisite temperature 'pedestal', there will be an optimum time after its termination for commencement of the spatial information containing light pulse.
It will also be noted from Figs. 2 and 3 that, whereas the first light pulses of the Fig.
2 regime produces a temperature profile in which the hottest region is at the centre of the liquid crystal layer, the initial effect of the ohmic heating pulse of the Fig. 3 regime is to produce a profile in which the hottest regions are at the two major surfaces of the layer.
Hence the two regimes can usefully be combined, so that the temperature profiles they produce will tend to cancel each other out.
With relatively large thermal excursions, as outlined above, the instantaneous temperature of the liquid crystal at the commencement of the spatial information containing light pulse needs to be known either by instantaneous measurement or by reference to previous calibration having regard to such factors as changes in ambient temperature. For instantaneous measurement an infra-red detector is preferred.
Although the foregoing specific description has related exclusively to the use of the liquid crystal layer for the recording of holographic information, it should be clearly understood that the invention is applicable also to the recording of conventional real images. Such an image can be recorded using coherent or incoherent light. For example, the output of a microfilm microfiche reader can be 'fixed' in the liquid crystal layer for direct reading or subsequent processing.
Similarly, although the foregoing specific description has related to a cell having a liquid crystal layer thickness of approximately 1 2 microns, there can be advantages, particularly for the recording of planar rather than volume holograms, in changing to a significantly reduced thickness of liquid crystal layer.
Claims (6)
1. A thermally excited positive dielectric anisotropy smectic liquid crystal display device including an internally electroded smectic liquid crystal display cell, means for setting the temperature of the liquid crystal layer of the cell to a temperature in the vicinity or significantly beneath its isotropic phase transition temperature, means for illuminating the layer with a spatially modulated light pattern whereby the temperature of at least the relatively more highly illuminated regions of the layer are raised by optical absorption to temperatures above the isotropic phase transition temperature, and means for applying a potential between the electrodes of the cell to develop an electric field through the thickness of its liquid crystal layer.
2. A method of recording a spatially modulated light pattern in a positive dielectric anisotropy smectic liquid crystal cell which method includes the steps
of setting the temperature of the liquid crystal layer of the cell to a temperature in the vicinity of, or signficiantly beneath its isotropic phase transition temperature,
of exposing the layer to a pulse of said spatially modulated light pattern, whereby the temperature of at least the relatively more highly illuminated regions of the layer are raised by optical absorption to temperatures above the isotropic phase transition temperature,
and of cooling the layer to a temperature in the smectic phase range, after the beginning of which cooling step a voltage pulse is applied across the thickness of the layer which voltage pulse commences at a time after the termination of the light pulse and before the entire layer has cooled into the smectic state, whereby said relatively more highly illuminated regions of the layer are caused to relax back into an optically clear smectic phase state while other less highly illuminated regions of the layer, having, before the commencement of the voltage pulse, relaxed into the smectic phase state that is optically scattering, remain in that optically scattering smectic phase state.
3. A method as claimed in claim 2, wherein said step of setting the temperature of the liquid crystal layer is to a temperature beneath the isotropic phase transition temperature of that liquid.
4. A method as claimed in claim 2 or 3, wherein said step of setting the temperature of the liquid crystal layer is provided at least in part by the application of a pulse of light to the layer that is at least partially absorbed by the layer.
5. A method as claimed in claim 2, 3 or 4, wherein said step of setting the temperature of the liquid crystal layer is provided at least in part by the application of ohmic heating current pulses to electrodes facing the major surfaces of the liquid crystal layer.
6. A method of recording a spatially modulated light pattern in a smectic liquid crystal cell which method is substantially as hereinbefore described with reference to Fig.
1, Figs. 1 and 2, Figs. 1 and 3, or Figs. 1, 2 and 3 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8418632A GB2162333B (en) | 1984-07-20 | 1984-07-20 | Recording spatially modulated light patterns |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8418632A GB2162333B (en) | 1984-07-20 | 1984-07-20 | Recording spatially modulated light patterns |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2162333A true GB2162333A (en) | 1986-01-29 |
| GB2162333B GB2162333B (en) | 1987-10-28 |
Family
ID=10564245
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8418632A Expired GB2162333B (en) | 1984-07-20 | 1984-07-20 | Recording spatially modulated light patterns |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2162333B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2173625A (en) * | 1985-04-10 | 1986-10-15 | Race Electronics Limited | A liquid crystal display device |
| GB2188743A (en) * | 1986-03-19 | 1987-10-07 | Gen Electric Plc | Thermal-imager testing device |
| GB2188748A (en) * | 1986-04-05 | 1987-10-07 | Stc Plc | Liquid crystal mask for semiconductor circuit manufacture |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1433130A (en) * | 1972-11-09 | 1976-04-22 | Secr Defence | Substituted biphenyl and polyphenyl compounds and liquid crystal materials and devices containing them |
| EP0012651A1 (en) * | 1978-12-15 | 1980-06-25 | Thomson-Csf | Liquid crystal display device |
| GB2090673A (en) * | 1981-01-02 | 1982-07-14 | Hewlett Packard Co | Memory system |
| EP0065397A2 (en) * | 1981-05-07 | 1982-11-24 | Minnesota Mining And Manufacturing Company | Thermal barrier for thermally addressed liquid crystal devices |
| EP0066965A1 (en) * | 1981-06-05 | 1982-12-15 | The Secretary of State for Defence in Her Britannic Majesty's Government of the United Kingdom of Great Britain and | Liquid crystal displays |
| EP0073701A1 (en) * | 1981-08-21 | 1983-03-09 | Thomson-Csf | Smectic liquid crystal display device |
| EP0087477A1 (en) * | 1981-09-07 | 1983-09-07 | Sony Corporation | Liquid crystal display device |
-
1984
- 1984-07-20 GB GB8418632A patent/GB2162333B/en not_active Expired
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1433130A (en) * | 1972-11-09 | 1976-04-22 | Secr Defence | Substituted biphenyl and polyphenyl compounds and liquid crystal materials and devices containing them |
| EP0012651A1 (en) * | 1978-12-15 | 1980-06-25 | Thomson-Csf | Liquid crystal display device |
| GB2090673A (en) * | 1981-01-02 | 1982-07-14 | Hewlett Packard Co | Memory system |
| EP0065397A2 (en) * | 1981-05-07 | 1982-11-24 | Minnesota Mining And Manufacturing Company | Thermal barrier for thermally addressed liquid crystal devices |
| EP0066965A1 (en) * | 1981-06-05 | 1982-12-15 | The Secretary of State for Defence in Her Britannic Majesty's Government of the United Kingdom of Great Britain and | Liquid crystal displays |
| EP0073701A1 (en) * | 1981-08-21 | 1983-03-09 | Thomson-Csf | Smectic liquid crystal display device |
| EP0087477A1 (en) * | 1981-09-07 | 1983-09-07 | Sony Corporation | Liquid crystal display device |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2173625A (en) * | 1985-04-10 | 1986-10-15 | Race Electronics Limited | A liquid crystal display device |
| GB2188743A (en) * | 1986-03-19 | 1987-10-07 | Gen Electric Plc | Thermal-imager testing device |
| US4861992A (en) * | 1986-03-19 | 1989-08-29 | The General Electric Company, P.L.C. | Testing of thermal imagers |
| GB2188743B (en) * | 1986-03-19 | 1989-11-29 | Gen Electric Plc | Thermal imager testing |
| GB2188748A (en) * | 1986-04-05 | 1987-10-07 | Stc Plc | Liquid crystal mask for semiconductor circuit manufacture |
| GB2188748B (en) * | 1986-04-05 | 1989-12-13 | Stc Plc | Semiconductor device manufacture |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2162333B (en) | 1987-10-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |