JPS5928517Y2 - optical reproduction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reproducing device that optically reproduces signals from a disc-shaped recording medium on which information signals are recorded as phase patterns.

In recent years, in order to increase the recording density of information, storage media have been developed that have blocks on the surface of a disk-shaped medium that have an apparently two-dimensional contour.

On this disc-shaped medium, frequency-modulated or phase-modulated sound and image information are encoded into block-shaped structures and recorded.

These block-like structures have a constant depth and various lengths on the medium surface of the disc, and are separated from each other by regions of various lengths (both of these lengths correspond to information signals). corresponding), arranged concentrically or spirally.

The depth of these block-like structures is such that the optical path difference between the light transmitted or reflected through the block-like structure and the light transmitted or reflected elsewhere is an odd number multiple of the half wavelength of the light used for reading. It is intended to be.

In order to read out signals encoded in the block-like structure of this disk-like medium, light with a good coherence range is irradiated onto the block-like structure, and the transmitted or reflected light is transmitted to the block-like structure. That is, the phase image of the phase pattern is guided to a photodetector via a device that converts it into a grayscale image.

There is a method using a Wollaston prism shown in FIG. 1 as a device for converting this phase pattern into a grayscale image and reproducing a signal.

Light emitted from a light source 1 passes through a polarizer 2 and is irradiated onto a transparent disc-shaped medium 3a having a phase pattern.

Lens 4 images the irradiated phase pattern onto photodetector 5 .

A Uniraston prism 6 is provided on the optical axis between the lens 4 and the photodetector 5.

The incident light is split into two sub-rays that are polarized at right angles to each other and sandwiched by a small angle from each other.

As a result, two phase images slightly shifted from each other are formed on the photodetector 5, and a grayscale image converted from the phase images appears.

The polarization direction of the polarizer 7 provided between the Wollaston prism 6 and the photodetector 5 forms an angle of 45° with the optical axis of each of the two crystals constituting the Wollaston prism 6.

The optical path difference between the two images passing through the Wollaston prism 6 is determined by the Wollaston prism 8 which is homologous to the Wollaston prism 6.
This is corrected by providing between the polarizer 2 and the disc-shaped medium 3a.

The above methods have various drawbacks.

For example, two Wollaston prisms and two polarizers are used, which increases the number of parts.

Therefore, a great deal of effort is required to align the respective optical axes.

Furthermore, a homologous Wollaston prism is required to optimize the shift between the two images, and high manufacturing precision is also required.

Furthermore, it is quite difficult to maintain a state in which the recorded surface of the block-like structure of the disk-like medium 3a is kept in focus, and information detection is also difficult.

In order to eliminate the drawbacks of the above-mentioned prior art, the present invention aims to irradiate light with a shifted focus onto the surface of a medium on a disk having concentric or spiral information recorded by a phase pattern. This information is read and reproduced with a simple configuration.

An embodiment of the present invention will be described below.

In FIG. 2, parallel light rays 9 emitted from a light source pass through a mirror 10 having an aperture 12 on the optical axis, and are focused by a lens 11 on the right side in the diagram of the phase pattern of the reflective disc-shaped medium 3b. and then irradiate the phase pattern.

An image of the phase pattern is created by lens 11 through aperture 12 on photodetector 13 .

Since the aperture 12 is provided in the vicinity of the focal point of the reflected light from the disk-shaped medium 3b, the image is formed on the photodetector 13 as a grayscale image with high frequency components cut off.

The light detection device 13 detects the disc-shaped medium 3b from the grayscale image.
Read the information recorded in the.

The light source may be a diverging or converging light source.

Next, a different embodiment of the apparatus shown in FIG. 3 will be described.

Parallel light rays emitted from the light source 14 pass through a half mirror 15 and are focused on the left side of the phase pattern by a lens 16.

The reflected light from the reflective disc-shaped medium 3b is still a diverging light even after passing through the lens 16.

Therefore, the image of the phase pattern is formed by the diverging light that has passed through the half mirror 15 being collected by the lens 17, passing through the aperture 19 provided near the focal point of the lens 17, and being formed as a gray scale image on the photodetector 18. .

The aperture 19 blocks high frequency components of the phase image, as described above.

The light source 14 may have diverging light or converging light.

A further different embodiment) will be explained in detail in FIG.

In FIG. 4, the parallel light emitted from the light source 20 is focused by the lens 21 on the left side of the phase pattern of the transparent disc-shaped medium 30, and then irradiates the phase pattern.

An image of the phase pattern is formed by lens 22 through aperture 23 onto photodetector 24 .

Since the aperture 23 is provided near the focal point of the lens 22, as described above, the high frequency components of the phase image are blocked and the image is detected as a concentrated image.

The light source 20 may be a diverging light source or a converging light source.

As described above, according to the present invention, there is provided a disk-shaped recording medium in which information signals are sequentially recorded as a phase pattern along concentric or spiral recording loci, and a disk-shaped recording medium in which information signals are guided and recorded on the recording medium. a condensing means arranged to irradiate a trajectory; a means for forming an image of reflected light or transmitted light from the recording medium of the light irradiated by the condensing means; and converting the formed light beam into an electrical signal. By providing a photoelectric conversion element that performs a photoelectric conversion, and an aperture means that removes a high frequency component of the reflected light or transmitted light between the recording medium and the photoelectric conversion element, the configuration of the optical system can be greatly simplified and the number of components can be reduced. Manufacturing costs can be reduced due to cost reduction and ease of assembly, making it possible to mass-produce at low cost.The reproduced phase pattern information is of very high quality, and signal reproduction is also easy. It has excellent effects.

Note that contrary to the configuration of the present invention, it is also possible to obtain a reproduced signal by blocking the zero-order light of the reflected light or transmitted light from the recording medium and then forming an image on the photoelectric conversion element. In this configuration, low frequency components with large optical energy are blocked, so the S/N ratio is degraded compared to the present invention.

In addition, if the focal point of the reflected or transmitted light shifts due to surface wobbling of the recording medium during playback, if the configuration is such that the low frequency component is blocked, the low frequency that passes through without being cut off due to the shift. The component mixes with the high frequency component with weak optical energy.

It is undesirable.

In this regard, in this invention, even if high-frequency components that should be cut off due to the shift of the focal point pass through, they will be mixed in with low-frequency components that include zero-order light with strong optical energy, so the effect will be small. It is.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a reproducing device characterized by using a conventional Wollaston prism, FIG. 2 is a block diagram of a reproducing device according to an embodiment of the present invention, and FIGS. 3 and 4 are respectively These are the constituent countries of a playback device according to another embodiment of the present invention. 10...mirror, 11, 16, 17, 21.22.
...Lens, 12,19,23...Aperture, 13°18.24...Photodetector, 3b...
...disk-shaped medium.

Claims (1)

[Scope of utility model registration request] A recording medium on a disk in which information signals are sequentially recorded as a phase pattern along a concentric or spiral recording trajectory;
a condenser arranged to guide light from a light source and irradiate a recording locus of the recording medium; and a means for forming an image of reflected light or transmitted light from the recording medium of the light irradiated by the condenser; The invention is characterized by comprising a photoelectric conversion element that converts the imaged light flux into an electric signal, and an aperture means that removes high frequency components of the reflected light or transmitted light between the recording medium and the photoelectric conversion element. optical reproduction device 3