WO1986003875A1

WO1986003875A1 - Method and apparatus for handling information

Info

Publication number: WO1986003875A1
Application number: PCT/GB1985/000595
Authority: WO
Inventors: Paul Jerome Banks
Original assignee: Paul Jerome Banks
Priority date: 1984-12-21
Filing date: 1985-12-20
Publication date: 1986-07-03
Also published as: GB2179193A; GB2179193B; GB8619803D0; EP0205533A1; GB8432563D0

Abstract

Photochromic material is contained in microscopic capsules (9) on a substrate (10) and is irradiated with information-containing radiation (12a) from a record laser (12) to darken certain of the capsules corresponding to the information. The darkening is fixed by heating with microwaves (16). The recorded information can be read using another or read laser (17) and the darkening can be removed using an erase laser (20). The arrangement may form part of information handling apparatus.

Description

METHODS AND APPARATUS FOR HANDLING INFORMATION

TECHNICAL FIELD

This invention relates to methods and apparatus for handling information.

BACKGROUND ART

United States Patent Specification 2953454 describes a data storage device using photochromic material and the disclosure is incorporated herein by reference. In the device a web sheet is coated with microscopic capsules each containing a tiny drop of oil in which is dissolved a small amount of a compound whose molecules in solution can be changed in their electromagnetic wave absorption characteristics, in controlled desired areas, by a certain wavelength band of electromagnetic waves applied thereto for a short time and will remain in the changed state under ordinary conditions, but can be reversed, when desired, to return the molecules to the original waveband absorption characteristics by application of another waveband of electromagnetic radiation.

US Specification 2953454 describes several ways of sensitizing the sheet with the compounds. US Patent specification 2730457 which is incorporated herein by reference describes ways of making such capsules. The capsules can adhere to the sheet to form a so-called film and US Patent specification 2374862, the disclosure of which is incorporated herein by reference, discloses such a film.

It is known to use electromagnetic radiation from a laser to record information on a substrate and to use electromagnetic radiation from a laser to read the information recorded on the substrate. Magneto-optic or phase-change discs, sometimes known as compact discs, are examples. Other examples are given in "photochromism" edited by Glenn H. Brown, published (1971) by John Wiley & Sons, Inc. of New York, USA for example Chapter X, for example pages 744-802, see 796-802 and 744-756, which also describes the use of an erase laser. Chapter III describes various photochromic compounds including (p270) ones involving stabilizing by heat. Reference may also be made to Chapter V of

"Photochromism" by G.H. Dorion and A.P. Wiebe published by Focal Press, London (1978).

One problem with stabilizing by heat is that heating in an oven causes the substrate to be heated and users of information handling equipment may not have, or wish to have, an oven. DISCLOSURE OF INVESTION

According to one aspect of the invention a method of handling information comprises irradiating areas of photochromic material by information-containing electromagnetic radiation to change the radiation absorption characteristic of the areas, and heating the areas by electromagnetic radiation to make the change effectively Stable. The heating may be by microwaves. The material may be incorporated in capsules forming a layer on a substrate. The method may include reading the recorded information by irradiating the areas with further electromagnetic radiation, and sensing the radiation after it has irradiated the areas. The method may include removing the change by irradiating said areas with electromagnetic radiation. According to another aspect of the invention apparatus for handling information comprises a body having photochromic material, a laser for emitting radiation on the material to produce areas of changed radiation absorption characteristic in the material, means for effecting relative movement between the laser and the body, and means for heating the areas by electromagnetic radiation to make the change effectively Stable . There may be means for producing microwaves to effect said heating. There may be a further laser for irradiating the areas, means for reflecting the radiation after the radiation has irradiated the areas, and means for sensing the reflected radiation and deriving information therefrom. There may be a third laser for irradiating the areas to remove the change. BRIEF DESCRIPTION OF DRAWINGS

The invention may be performed in various ways and one specific embodiment with possible modifications will now be described by way of example with reference to the accompanying schematic drawings, in which:

Fig. 1 is a side view of one apparatus;

Fig. 2 is a plan view of a disc and holder; and

Fig. 3 is a plan view of other apparatus.

BEST MODE OF CARRYING OUT THE INVENTION In the present arrangement information is handled using a photochromic body and the information can be recorded, stored, erased and read.

A photochromic body will darken on exposure to appropriate radiation i.e. the absorption characteristic of the material for electromagnetic radiation is changed. Different photochromic materials may respond to different wavelengths or ranges of wavelengths. In the present case this effect is used to handle information. Referring to Fig. 1, a parallel-sided body 10, for example rectangular in plan, is of material essentially transparent to electromagnetic radiation of the wavelengths concerned and one face of the body 10 is coated with a reflective material 11, for example silver. The other face of the body 10 is coated with microscopic capsules formed in known manner, for example as in US Specification 2730457. The coating is applied in known manner, for example as in US Specification 2374862. In the present case the photochromic material in the capsules requires to be heated to be stabilized in a darkened condition. Examples of such material are:

derivatives of 1',3',3' - trimethyespiro-[2H-1-benzopyran-2,2'-indoline] (BIPS) having in the 8-position a (CH₂ NR₃)⁺ group.

Each capsule contains an emulsion of water and a photochromic compound. When irradiated with electromagnetic radiation of the appropriate wavelength or within a range of appropriate wavelengths the photochromic material darkens i.e. its absorption characteristic increases. It is thought that as this occurs the emulsion to some degree separates into water and compound. Each capsule may have a lateral dimension of say 1 micron.

A first laser 12 which emits radiation of an appropriate wavelength is moved in a scanning mode in relation to the body 10. Thus the laser 12 is moved to and fro in the direction of arrows A and in steps at right angles thereto. The laser 12 is energized by known means to emit radiation 12a in pulses so as to produce spaced darkened zones 13 in the coating. The zones 13 are merely illustrative. There are thus produced in the coating one or more rows of darkened zones, each row having darkened and undarkened zones which are arranged to represent digital information in a binary form. Each zone may be one or more capsules. The pulsing of the laser and the speed of the laser relative to the coating are arranged to produce the required zones of dark and clear.

The digital information represented by the zones may originate from any suitable apparatus producing electrical signals for energizing the laser and may represent audio, video, data processing, word processing or other information. Methods of energizing the laser in the desired manner are known and may include a data input or receiving device 14 and a data handling device 15 including an encoder. It is believed devices 14, 15 are well known to the skilled man and further details are not required.

In some cases, dependent on the selected photochromic material, it may be necessary to heat the irradiated capsules in order to fix the darkened zones to prevent them fading. The present arrangements are concerned with this. The coating is exposed to microwave energy (electromagnetic radiation) from a magnetron 16, for example, suitably energized. This heating is continued for a period to raise the temperature of the water in the irradiated capsules, for example to between 100°C and 150°C, to fix the darkening. The capsules which have not been irradiated by laser 12 remain clear.

In order to read the information stored in the coating another laser 17, with a different wavelength to the record laser 12, is moved in a scanning mode relative to the coating; radiation from the laser 17 passes into the body 10 and is reflected by surface 11 but may be interrupted or affected by dark zones. The dark zones thus affect the radiation reflected back to the laser 17 and this is sensed using known apparatus 17a to produce an electrical output signal corresponding to the digital information being read by laser 17. Thus a photomultiplier 17b may receive and amplify the reflected radiation signal and provide an output signal to a decoder 17c which has an ouτput signal which could be in audio or visual form or in the form of signals for data transmission. Means for obtaining information from the output signal of a laser are known and it is believed further details are not required. Methods of supplying information to a "write" laser such as laser 12 and of obtaining information from a "read" laser such as laser 17 are described for example in "Philips Technical Revue" No. 40 pages 151-172, 1982, No. 6, to which reference can be made and the disclosure of which is incorporated by reference. Reference may also be made the "photochromism" above. The information stored in the body 10 can be erased by using a third or erase laser 20, emitting radiation of a wavelength different from the radiation from lasers 12, 17, and passing the laser 20 in a scanning mode across the coating to erase such information as desired, the radiation from laser 20 causing the selected dark zones to become clear again.

The body 10 could be a disc 21 with central aperture 21a which can be housed in a radiation or light-proof flat sleeve 22.

In Fig. 2 the disc 21 is mounted for rotation in suitable apparatus and the record, read and erase lasers are angularly spaced and traverse radially.

One form of photochromic material in the form of an emulsion of a BIPS derivative and water darkens on exposure to ultraviolet light, and is erased by visible light from an erase laser and is read by infrared light from the read laser.

The size of the disc 10 can be varied and in some cases up to 600 megabytes of information can be stored. It is not necessary for the beam from the read laser to be reflected; the layer 11 can be omitted and the read laser and associated sensor be on opposite sides of the substrate 10, using transmitted radiation. In another example a second photochromic body 10a with coating 9a similar to coating 9 is provided on the other side of the layer 11, which layer itself is reflective on both sides, so that the assembly of body 10, surface 11, body 10a can receive light from two opposite sides if required or can be turned over, thus effectively doubling the storage capacity. The information stored in the coating 9 or 9a may be in analogue form. In this case the laser 12 is not pulsed but produces a line of darkening in the capsules; the width, or intensity of darkening, of the line corresponding to the analogue information and this is read by a continuously energized read laser 17 whose output signal may pass to an analogue to digital convertor.

When the darkened zones have been cleared the coating 9 or 9a can be used again for storing further information.

INDUSTRIAL APPLICABILITY

The apparatus finds use in information handling. For example the recording medium or coating 9 and support 10 could be used to replace the so-called compact disc or could be used to record information on a tab or card or other label to be subsequently read by a read laser. The invention may find use in holography.

Claims

1. A method of handling information comprising irradiating areas of photochromic material by information-containing electromagnetic radiation to change the radiation absorption characteristic of the areas, and heating the areas by electromagnetic radiation to make the change effectively stable.

2. A method as claimed in Claim 1, in which the heating is by microwaves.

3. A method as claimed in Claim 1, in which the material is incorporated in capsules forming a layer on a substrate.

4. A method as claimed in Claim 1 or Claim 2, including reading the recorded information by irradiating the areas with further electromagnetic radiation, and sensing the radiation after it has irradiated the areas.

5. A method as claimed in Claim 1 or Claim 4, including removing the change by irradiating said areas with electromagnetic radiation.

6. Apparatus for handling information comprising a body having photochromic material, a laser for emitting radiation on the material to produce areas of changed radiation absorption characteristic in the material, means for effecting relative movement between the laser and the body, and means for heating the areas by electromagnetic radiation to make the change effectively

7. Apparatus as claimed in Claim 6, including means for producing microwaves to effect said heating.

8. Apparatus as claimed in Claim 6, including a further laser for irradiating the areas, means for reflecting the radiation after the radiation has irradiated the areas, and means for sensing the reflected radiation and deriving information therefrom.

9. Apparatus as claimed in Claim 7, including a third laser for irradiating the areas to remove the change.