CA1063241A - Carrier provided with a spiral structure in which sound and/or image information is stored - Google Patents
Carrier provided with a spiral structure in which sound and/or image information is storedInfo
- Publication number
- CA1063241A CA1063241A CA287,701A CA287701A CA1063241A CA 1063241 A CA1063241 A CA 1063241A CA 287701 A CA287701 A CA 287701A CA 1063241 A CA1063241 A CA 1063241A
- Authority
- CA
- Canada
- Prior art keywords
- carrier
- radiation
- light beam
- record carrier
- detector
- 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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- Optical Recording Or Reproduction (AREA)
Abstract
ABSTRACT:
A carrier is described which is provided with a spiral structure in which sound and/or image information is stored in the form of frequency-modulated or phase-modulated signals. It is stated that the structure is composed of blocks of variable lengths which lie in one plane and are separated by areas of variable lengths which also lie in one plane.
It is stated that the blocks have a coefficient of reflection or of transmission which is different from that of the areas.
It is described that the two planes are spaced from one another by a constant distance.
A carrier is described which is provided with a spiral structure in which sound and/or image information is stored in the form of frequency-modulated or phase-modulated signals. It is stated that the structure is composed of blocks of variable lengths which lie in one plane and are separated by areas of variable lengths which also lie in one plane.
It is stated that the blocks have a coefficient of reflection or of transmission which is different from that of the areas.
It is described that the two planes are spaced from one another by a constant distance.
Description
1063Z4i PHN. 5497.
This application is a division of Canadian Patent Application Serial No. 136,033 filed March 2, 1972.
The invention relates to a carrier pro~ided with a spiral structure in which sound and/or image information in the form of frequency-modulated or phase- dulated signals is stored. The term "spiral structure" is to be understood to mean a structure composed of a large number of quasi-concentric or concentric tracks. The invention also relates to an apparatus for detecting information stored in the carrier by means of a beam of radiation which after inter-action with the structure is supplied to a radiation-sensitive detection system.
A carrier and an apparatus of the afore-mentioned type are known. The known carrier has a spiral groove the bottom of which has an undulating profile. Although in reproducing the known carrier the conventional gra phone disc record technology is used, manufacture of the first carrier is a time-consuming laborious process, for the information is s~ored in the form of grooves which can only be formed by means of machine tools.
When detecting the information stored in the known carrier the angle at which the surfaces of the undulating grooves are to ~eplane of the carrier plays an essential part. Moreover the lands between the consecutive tracks play an essential role in following the track. This renders it necessary to provide a complicated three-dimensional profile on the carrier.
The disadvantage to which ~he known carrier is
This application is a division of Canadian Patent Application Serial No. 136,033 filed March 2, 1972.
The invention relates to a carrier pro~ided with a spiral structure in which sound and/or image information in the form of frequency-modulated or phase- dulated signals is stored. The term "spiral structure" is to be understood to mean a structure composed of a large number of quasi-concentric or concentric tracks. The invention also relates to an apparatus for detecting information stored in the carrier by means of a beam of radiation which after inter-action with the structure is supplied to a radiation-sensitive detection system.
A carrier and an apparatus of the afore-mentioned type are known. The known carrier has a spiral groove the bottom of which has an undulating profile. Although in reproducing the known carrier the conventional gra phone disc record technology is used, manufacture of the first carrier is a time-consuming laborious process, for the information is s~ored in the form of grooves which can only be formed by means of machine tools.
When detecting the information stored in the known carrier the angle at which the surfaces of the undulating grooves are to ~eplane of the carrier plays an essential part. Moreover the lands between the consecutive tracks play an essential role in following the track. This renders it necessary to provide a complicated three-dimensional profile on the carrier.
The disadvantage to which ~he known carrier is
- 2 -PHN. 5497-sub~ect is avoided in the carrier according to the invention which hàs a quasi-two dimensional profile. The carrier according to the invention may comparatively simply and rapidly be manufactured by photographic and etching methods.
The invention is characterized in that the struc-ture is composed of blocks of variable lengths which lie in one plane and are separated by areas of variable lengths which also lie in one plane. The beam of radiation which interacts with these blocks is modulated in phase or in amplitude by the said structure. The dulated radiation beam is applied to a radiation-sensitive detection system. The recurrence of characteristic values of the signal produced in the detection system, for example the recurrence of the passages through zero of the alternating-voltage component of the signal, is detected. Variations in the luminous flux of the source of light and defocussing do not effect the mutual time differences between these passages through zero, nor do variations in the properties of the photographic material.
The blocks are advantageously given a coefficient of reflec-tion or transmission which is different from that of the areas though they may have equal coefficients of reflection.
A particularly advantageous structure for storing information in the form of frequency- dulated signals is a structure in which the planes are spaced from one another by a constant distance. The advantage of this feature is that such a structure may readily be manufactured by means of lithographic processes. In addition, detection of the stored signal is comparatively simple, for such a crenellated structure may optically be regarded as a phase structure PHN. 5497.
capable of being read by known optical means. Obviously, the transitions between successive blocks and areas may be either abrupt or smooth, both in the direction of the track and in the axial direction of the carrier. To protect the carrier provided with the information its surface on which the infor-mation is provided may be coatet with a protective layer.
Hence, according to a feature of the inven~ion an apparatus for detecting the information stored in the carrier by means of a beam of radiation which after interaction with the structure is applied to a radiation-sensitive detection system inc'udes an image-forming element inserted in the ray-path. In particular, the radiation beam which has interacted with the information in the carrier is divided by an element into two sub-beams which are relatively shifted through a small distance.
According to another feature of the invention an apparatus for detecting the information stored in the carrier by means of a beam of radiation which after inter-action with the structure is applied to a radiation-sensitive detection system includes an element which imparts a mutual phase difference to the sub-beams which are pro-duced at the structure by diffraction.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying dia-grammatic drawings, in which:
Figure 1 shows a carrier according to the invention, and Figures 2, 3, 4, 5 and 6 illustrate apparatus for detecting the information stored in the carrier shown in PHN. 5497.
1063Z4~
Figure 1.
Figure la is a plan view of part of a carrier 1.
The carrier 1 contains a spiral structure having a large number of quasi-concentric tracks. These tracks may alter-natlvely be concentric, as shown in Fig. 1. ~nly part of two ad~acent tracks (designated 12 and 13) is shown. Each track comprises~a crenellated structure the dimensions of which are shown exaggerated in Figure lb. The spacings between the upper surfaces 3 and 5, 5 and 7, and so on of the merlons are different and so are their lengths. Both spacings and lengths are determined by the information stored in the tracks. The heights 4~ 6, 8 and so on of the merlons are equal to one another and in the case of trans-mission preferably are equal to about one wavelength of the radiation by means of which the carrier is scanned. In the case of reflection they are equal to one quarter of the wavelength of the radiation by means of which the carrier is scanned.
The carrier may be made of, for example, polyvinyl acetate. The spacing between ad~acent tracks is, for example, 4 /um, and the smallest period in each track is, for example, 2.5 /um. The carrier rotates at a speed of, for example, 1,500 revolutions per minute about its axis, which in Figure la is designated by 0. The arrow in Figure lb indicates the travelling direction of the track.
In the reading apparatus shown in Figure 2 a colli-mated beam of light from a source of light 20 is incident via a polarizer 21 on the carrier 1 the tracks of which have a crenellated structure. A lens 25 produces on a detector 23 PHN. 5497-an image of the part of the carrier 1 on which the light beam falls. According to the invention a Wollaston prism 24 is inserted in the path of the light beam between the carrier 1 and the detector 23. The Wollaston prism comprises two con-gruent prisms 27 and 28 which each consist of a uniaxial bire-fringent crystal and together form a plane-parallel plane 24.
The optic axis cl of the crystal 28 is parallel to the plane of the drawing and the optic axis c2 of the crystal 27 is at right angles to the plane of the drawing. The light beam in-cident on one of the parallel larger surfaces of the Wollaston prism 24 is divided in the prism into two sub-beams which are polarized at right angles to one another and extend at a small angle to one another.
Consequently, in the plane of the detector 23 two images of the illuminated part of the carrier 1 are produced which are relatively shifted. Between the Wollaston prism 24 and the detector 23 there is arranged a polarizer 26 the direction of polarisation of which is at an angle of 45- to the optic axes cl and c2 of the crystals 28 and 27 respectively.
Thus, the differences between the intensities of the two images measured in the detector 23 have maximum values.
These differences are due to the path length differences of the light beam in the crenellated structure and, owing to the suitable choice of about one wavelength for the height of the merlons, are ~ A ~
The path length difference of the sub-beams forming the two images which is produced in the Wollaston prism 24 is com-pensated by a path length difference produced in a Wollaston prism 22 which is identical to the prism 24 and is inserted PHN. 5497-; 1063Z41 between the carrier 1 and the polarizer 21.
The Wollaston prism 24 may be replaced by a Savart plate. A Savart plate consists of two equally thick plane-parallel quartz plates the optic axes of which are at angles of 45- to the plane-parallel surfaces and are crossed. A
light beam normally incident on one of the plane~parallei surfaces o~ the Savart plate is split in the first quartz plate into an ordinary ray and an extra-ordinary ray, which at the interface between the first and the second quart~
plates are converted into an extra-ordinary ray and an ordinary ray respectively, since the optic axes of the two crystals are at right angles to one another. From the Savart plates there emerge two sub-beams which are polarized at right angles to one another and are shifted relatively to one another. An analyzer 26 again is crossed with respect to the optic axes of the Savart plate. In this embodiment also, the path difference between the two rays due to the Savart plate is compensated by the insertion of an identical Savart plate between the carrier l and the light source 20.
In the apparatus shown in Figure 3 an image of the carrier 1 is formed by a lens 31 on the detector 23. From the carrier 1 there again emerges a wave front having a phase structure due to the path length differences in the crenellated structure of the track on the carrier 1.
An interferometer 32 is arranged between the lens 31 and the detector 23. The interferometer 32 comprises two prisms made of a suitable glass and cemented together. At the semi-transmitting interface 33 of the prisms part of the beam is transmitted and part is reflected.
lO~Z41 PHN. 5497.
The transmitted and reflected sub-beams are reflected at the reflective lateral surfaces 34 and 35 respectively of the component prisms. These surfaces are al st at right angles to one another. The sub-beams reflected by the surfaces 34 and 35 after reflection at and transmission respectively through the interface 33 form closely ad~acent parallel images the intensity difference between which is again determined by the crenellated structure.
In the apparatus shown in Figure 4 a divergent light-beam emitted by a point source 65 is converted by a lens 66 into a colllmated light beam which falls on the carrier 1.
The zero-order beam which is transmitted by the carrier 1 without diffraction is converted by a lens 67 into a conver-gent beam which is focused in a point M of a phase plate 68.
The beams transmitted by the carrier 1 as diffracted beams, for example of the order ~1 and -1 (owing to its struc-ture the support may be regarded as a diffraction grating) are converged by the lens 67 in a point which, viewed in the direc-tion of propagation of the radiation beams, lies beyond the phase plate 68. These beams do not pass through the point M
of the phase plate 68. At the location at which a detector 69 is arranged the undiffracted beam (zero-order beam) and the diffracted beams (+lst-order and -lst-order beams) unite.
The phase plate is proportioned such as to introduce a 90- phase difference between the +l-order and -l-order beams on the one hand and the zero-order beams on the other. Thus, the intensity differences between the beams incident on the detector 69 are as large as possible.
The source of light used in an apparatus for detecting 1063Z41 PHN. 5497-the signals stored in the carrJer may be a source having a great brightness and a high degree of coherence, for example a laser. The light source may alternatively be an incohe-rent source of great brightness, for example a photo-emissive diode. As a further alternative the light source may be a gas discharge tube.
The detector used may be a photomultiplier or a solid-state detector, for example a silicon detector.
An advantageous apparatus for detecting the infor-mation stored in the carrier is shown in Fig. 5. A carrier 70 has a spiral structure comprising a large number of quasi-concentric tracks. The tracks may also be concentric.
Each track has a crenellated structure. The carrier rotates about an axis which in the Figure is shown as a dot-dash line.
A light beam of small aperture produced by a source of light 71 and a narrow slit in a mirror 72 is focused onto the carrier 70 by a lens 74. The crenellated or block-shaped structure on the carrier 70 reflects the focused light beam.
On the plsne portions of the crenellated structure, i.e. the portions which extend at right angles to the rotation axis, ehe light beam is incident at an angle of incidence ~hich is nearly zero degrees. The reflected light beam then has a direction which is substantially opposite to that of the incident beam and an angle of aperture which is equal to that of the beam incident on the carrier. This reflected light beam emerges through the slit in the mirror 72.
When, however, the light beam is incident on the carrier 70 at areas between the plane portions, i.e. the PHN. 5497.
upright faces of the blocks, owing to diffraction the reflected beam will have a larger aperture angle than has the incident beam. By means of an annular objective 75 this scattered light beam reflected at the upright faces of the blocks after reflec-tiOtl at the mirror 72 is focused onto a detector 73. The upright faces are imaged with a high contrast.
Another apparatus for detecting the information stored in the carrier is shown in Fig. 6. A source of light 81 is imaged by a lens 82 in a slit of a screen 83. From the slit a light beam emerges which via a mirror 84 and a lens 85 is focused onto a carrier 80. The image of the slit on the carrier 80 is smaller than, or equal to, the dimensions of the blocks in the spiral structure on the carrier 80.
The light transmitted by the transparent carrier 80 is imaged via an ob~ective 86 on a detector 87 which may be of comparatively large size. Obviously the carrier 80 may alternatively be reflecting. In this case the mirror 84 takes the form of a semitransparent mirror.
The detector 87 may alternatively be replaced by a combination of a slit and a detector which, viewed in the direction of propagation of the light, is located behind the slit. This slit is required to eliminate that portion of the light beam which has interacted with other tracks than the track to be scanned.
The invention is characterized in that the struc-ture is composed of blocks of variable lengths which lie in one plane and are separated by areas of variable lengths which also lie in one plane. The beam of radiation which interacts with these blocks is modulated in phase or in amplitude by the said structure. The dulated radiation beam is applied to a radiation-sensitive detection system. The recurrence of characteristic values of the signal produced in the detection system, for example the recurrence of the passages through zero of the alternating-voltage component of the signal, is detected. Variations in the luminous flux of the source of light and defocussing do not effect the mutual time differences between these passages through zero, nor do variations in the properties of the photographic material.
The blocks are advantageously given a coefficient of reflec-tion or transmission which is different from that of the areas though they may have equal coefficients of reflection.
A particularly advantageous structure for storing information in the form of frequency- dulated signals is a structure in which the planes are spaced from one another by a constant distance. The advantage of this feature is that such a structure may readily be manufactured by means of lithographic processes. In addition, detection of the stored signal is comparatively simple, for such a crenellated structure may optically be regarded as a phase structure PHN. 5497.
capable of being read by known optical means. Obviously, the transitions between successive blocks and areas may be either abrupt or smooth, both in the direction of the track and in the axial direction of the carrier. To protect the carrier provided with the information its surface on which the infor-mation is provided may be coatet with a protective layer.
Hence, according to a feature of the inven~ion an apparatus for detecting the information stored in the carrier by means of a beam of radiation which after interaction with the structure is applied to a radiation-sensitive detection system inc'udes an image-forming element inserted in the ray-path. In particular, the radiation beam which has interacted with the information in the carrier is divided by an element into two sub-beams which are relatively shifted through a small distance.
According to another feature of the invention an apparatus for detecting the information stored in the carrier by means of a beam of radiation which after inter-action with the structure is applied to a radiation-sensitive detection system includes an element which imparts a mutual phase difference to the sub-beams which are pro-duced at the structure by diffraction.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying dia-grammatic drawings, in which:
Figure 1 shows a carrier according to the invention, and Figures 2, 3, 4, 5 and 6 illustrate apparatus for detecting the information stored in the carrier shown in PHN. 5497.
1063Z4~
Figure 1.
Figure la is a plan view of part of a carrier 1.
The carrier 1 contains a spiral structure having a large number of quasi-concentric tracks. These tracks may alter-natlvely be concentric, as shown in Fig. 1. ~nly part of two ad~acent tracks (designated 12 and 13) is shown. Each track comprises~a crenellated structure the dimensions of which are shown exaggerated in Figure lb. The spacings between the upper surfaces 3 and 5, 5 and 7, and so on of the merlons are different and so are their lengths. Both spacings and lengths are determined by the information stored in the tracks. The heights 4~ 6, 8 and so on of the merlons are equal to one another and in the case of trans-mission preferably are equal to about one wavelength of the radiation by means of which the carrier is scanned. In the case of reflection they are equal to one quarter of the wavelength of the radiation by means of which the carrier is scanned.
The carrier may be made of, for example, polyvinyl acetate. The spacing between ad~acent tracks is, for example, 4 /um, and the smallest period in each track is, for example, 2.5 /um. The carrier rotates at a speed of, for example, 1,500 revolutions per minute about its axis, which in Figure la is designated by 0. The arrow in Figure lb indicates the travelling direction of the track.
In the reading apparatus shown in Figure 2 a colli-mated beam of light from a source of light 20 is incident via a polarizer 21 on the carrier 1 the tracks of which have a crenellated structure. A lens 25 produces on a detector 23 PHN. 5497-an image of the part of the carrier 1 on which the light beam falls. According to the invention a Wollaston prism 24 is inserted in the path of the light beam between the carrier 1 and the detector 23. The Wollaston prism comprises two con-gruent prisms 27 and 28 which each consist of a uniaxial bire-fringent crystal and together form a plane-parallel plane 24.
The optic axis cl of the crystal 28 is parallel to the plane of the drawing and the optic axis c2 of the crystal 27 is at right angles to the plane of the drawing. The light beam in-cident on one of the parallel larger surfaces of the Wollaston prism 24 is divided in the prism into two sub-beams which are polarized at right angles to one another and extend at a small angle to one another.
Consequently, in the plane of the detector 23 two images of the illuminated part of the carrier 1 are produced which are relatively shifted. Between the Wollaston prism 24 and the detector 23 there is arranged a polarizer 26 the direction of polarisation of which is at an angle of 45- to the optic axes cl and c2 of the crystals 28 and 27 respectively.
Thus, the differences between the intensities of the two images measured in the detector 23 have maximum values.
These differences are due to the path length differences of the light beam in the crenellated structure and, owing to the suitable choice of about one wavelength for the height of the merlons, are ~ A ~
The path length difference of the sub-beams forming the two images which is produced in the Wollaston prism 24 is com-pensated by a path length difference produced in a Wollaston prism 22 which is identical to the prism 24 and is inserted PHN. 5497-; 1063Z41 between the carrier 1 and the polarizer 21.
The Wollaston prism 24 may be replaced by a Savart plate. A Savart plate consists of two equally thick plane-parallel quartz plates the optic axes of which are at angles of 45- to the plane-parallel surfaces and are crossed. A
light beam normally incident on one of the plane~parallei surfaces o~ the Savart plate is split in the first quartz plate into an ordinary ray and an extra-ordinary ray, which at the interface between the first and the second quart~
plates are converted into an extra-ordinary ray and an ordinary ray respectively, since the optic axes of the two crystals are at right angles to one another. From the Savart plates there emerge two sub-beams which are polarized at right angles to one another and are shifted relatively to one another. An analyzer 26 again is crossed with respect to the optic axes of the Savart plate. In this embodiment also, the path difference between the two rays due to the Savart plate is compensated by the insertion of an identical Savart plate between the carrier l and the light source 20.
In the apparatus shown in Figure 3 an image of the carrier 1 is formed by a lens 31 on the detector 23. From the carrier 1 there again emerges a wave front having a phase structure due to the path length differences in the crenellated structure of the track on the carrier 1.
An interferometer 32 is arranged between the lens 31 and the detector 23. The interferometer 32 comprises two prisms made of a suitable glass and cemented together. At the semi-transmitting interface 33 of the prisms part of the beam is transmitted and part is reflected.
lO~Z41 PHN. 5497.
The transmitted and reflected sub-beams are reflected at the reflective lateral surfaces 34 and 35 respectively of the component prisms. These surfaces are al st at right angles to one another. The sub-beams reflected by the surfaces 34 and 35 after reflection at and transmission respectively through the interface 33 form closely ad~acent parallel images the intensity difference between which is again determined by the crenellated structure.
In the apparatus shown in Figure 4 a divergent light-beam emitted by a point source 65 is converted by a lens 66 into a colllmated light beam which falls on the carrier 1.
The zero-order beam which is transmitted by the carrier 1 without diffraction is converted by a lens 67 into a conver-gent beam which is focused in a point M of a phase plate 68.
The beams transmitted by the carrier 1 as diffracted beams, for example of the order ~1 and -1 (owing to its struc-ture the support may be regarded as a diffraction grating) are converged by the lens 67 in a point which, viewed in the direc-tion of propagation of the radiation beams, lies beyond the phase plate 68. These beams do not pass through the point M
of the phase plate 68. At the location at which a detector 69 is arranged the undiffracted beam (zero-order beam) and the diffracted beams (+lst-order and -lst-order beams) unite.
The phase plate is proportioned such as to introduce a 90- phase difference between the +l-order and -l-order beams on the one hand and the zero-order beams on the other. Thus, the intensity differences between the beams incident on the detector 69 are as large as possible.
The source of light used in an apparatus for detecting 1063Z41 PHN. 5497-the signals stored in the carrJer may be a source having a great brightness and a high degree of coherence, for example a laser. The light source may alternatively be an incohe-rent source of great brightness, for example a photo-emissive diode. As a further alternative the light source may be a gas discharge tube.
The detector used may be a photomultiplier or a solid-state detector, for example a silicon detector.
An advantageous apparatus for detecting the infor-mation stored in the carrier is shown in Fig. 5. A carrier 70 has a spiral structure comprising a large number of quasi-concentric tracks. The tracks may also be concentric.
Each track has a crenellated structure. The carrier rotates about an axis which in the Figure is shown as a dot-dash line.
A light beam of small aperture produced by a source of light 71 and a narrow slit in a mirror 72 is focused onto the carrier 70 by a lens 74. The crenellated or block-shaped structure on the carrier 70 reflects the focused light beam.
On the plsne portions of the crenellated structure, i.e. the portions which extend at right angles to the rotation axis, ehe light beam is incident at an angle of incidence ~hich is nearly zero degrees. The reflected light beam then has a direction which is substantially opposite to that of the incident beam and an angle of aperture which is equal to that of the beam incident on the carrier. This reflected light beam emerges through the slit in the mirror 72.
When, however, the light beam is incident on the carrier 70 at areas between the plane portions, i.e. the PHN. 5497.
upright faces of the blocks, owing to diffraction the reflected beam will have a larger aperture angle than has the incident beam. By means of an annular objective 75 this scattered light beam reflected at the upright faces of the blocks after reflec-tiOtl at the mirror 72 is focused onto a detector 73. The upright faces are imaged with a high contrast.
Another apparatus for detecting the information stored in the carrier is shown in Fig. 6. A source of light 81 is imaged by a lens 82 in a slit of a screen 83. From the slit a light beam emerges which via a mirror 84 and a lens 85 is focused onto a carrier 80. The image of the slit on the carrier 80 is smaller than, or equal to, the dimensions of the blocks in the spiral structure on the carrier 80.
The light transmitted by the transparent carrier 80 is imaged via an ob~ective 86 on a detector 87 which may be of comparatively large size. Obviously the carrier 80 may alternatively be reflecting. In this case the mirror 84 takes the form of a semitransparent mirror.
The detector 87 may alternatively be replaced by a combination of a slit and a detector which, viewed in the direction of propagation of the light, is located behind the slit. This slit is required to eliminate that portion of the light beam which has interacted with other tracks than the track to be scanned.
Claims (9)
1. Apparatus for detecting with a light beam infor-mation stored in a disc-shaped record carrier provided with a spiral pattern of regions having flat, substantially parallel upper surfaces of variable length separated by flat, substantially coplanar areas of variable length, where the plane of the areas is parallel to the plane of the regions and is separated therefrom by an amount sufficient to intro-duce a phase differnece of nL/2 between portions of the light beam which coact with the flat areas and those which coact with the regions, where n is a positive odd integer and L is the wavelength of the light beam; the apparatus comprising means for directing the light beam to the record carrier, whereby the beam is modulated by the stored infor-mation, and a radiation-sensitive detection system means for converting the modulated beam from the record carrier into an electrical signal corresponding to the information.
2. Apparatus as claimed in Claim 1, characterized in that a point image is produced at the location of the carrier.
3. Apparatus as claimed in Claim 1 or 2, characterized in that the carrier is imaged on a diaphragm opening behind which, viewed in the direction of propagation of the radiation, the detector is disposed.
4. Apparatus as claimed in Claim 2, characterized in that the radiation beam from the carrier is imaged on the diaphragm opening in front of the detector.
5. Apparatus as claimed in Claim 1, characterized in that the radiation beam which has interacted with the infor-mation in the carrier is divided by a beam-splitter means into two sub-beams which are relatively shifted through a small distance.
6. Apparatus as claimed in Claim 5, characterized in that the beam-splitter means is a Wollaston prism.
7. Apparatus as claimed in Claim 5, characterized in that the beam-splitter means is a Savart plate.
8. Apparatus as claimed in Claim 5, characterized in that the beam-splitter means is a Michelson interferometer the two reflectors of which, viewed from the detection system, are inclined at a small angle to one another.
9. Apparatus as claimed in Claim 1, characterized by a phase plate in the beam path between the record carrier and the radiation-sensitive detection means for passing to the radiation-sensitive detection means the zero order and first order beams diffracted by the record carrier and for introducing a 90° phase difference between the first order beams.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA287,701A CA1063241A (en) | 1971-03-04 | 1977-09-28 | Carrier provided with a spiral structure in which sound and/or image information is stored |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7102863A NL7102863A (en) | 1971-03-04 | 1971-03-04 | |
| CA136,033A CA1023855A (en) | 1971-03-04 | 1972-03-02 | Carrier provided with a spiral structure in which sound and/or image information is stored |
| CA287,701A CA1063241A (en) | 1971-03-04 | 1977-09-28 | Carrier provided with a spiral structure in which sound and/or image information is stored |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1063241A true CA1063241A (en) | 1979-09-25 |
Family
ID=27161813
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA287,701A Expired CA1063241A (en) | 1971-03-04 | 1977-09-28 | Carrier provided with a spiral structure in which sound and/or image information is stored |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1063241A (en) |
-
1977
- 1977-09-28 CA CA287,701A patent/CA1063241A/en not_active Expired
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