JPS626446A - Optical information processor - Google Patents

Abstract

PURPOSE:To increase capacity recorded on an information medium and a reproducing rate by providing the titled processor with at least two light sources different in wavelength and a grating type objective lens for converging and irradiating optical beams from the light sources to an information surface. CONSTITUTION:A beam with wavelength lambda1 radiated from the 1st light source 21 is turned to a parallel beam by a collimater lens 23, converged and irradiated to the 1st information pit surface of an information medium 5 as a fine spot by an objective lens 25, modulated by the pit, reflected by a filter layer 2, converged again by the objective lens 25, lead into the detecting side by a beam splitter 24, and then converged and detected by the 1st photodetector 27. A beam with wavelength lambda2 radiated from the 2nd light source 22 is turned to a parallel beam by a lens 23, passed through the filter layer 2, converged and irradiated on the 2nd information pit surface as a fine spot, modulated by the pit, reflected, separated through a filter 26, and then converged and detected by the 2nd photodetector 25. Consequently, the capacity recorded on the medium and the reproducing rate can be increased.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to an optical information processing device.

[Technical background of the invention and its problems]

Conventionally, in order to increase the information density of optical discs known as information media such as video discs and digital audio discs, two methods have been used: one method is to attach the front and back sides together and irradiate each surface with a light beam to read out each surface individually. A method has been proposed in which pit rows are formed on the front and back sides of a sheet and read out using transmitted light.

However, both are single-wavelength light sources, and each surface is read out separately. Therefore, the amount of information that can be read out within a unit time (reproduction rate) has not increased.In the conventional method, in order to increase this reproduction rate, the size of the pits is reduced (the spatial frequency increases), but the pit size The only option is to increase the scanning speed (increase the rotational speed of the optical disc).

However, the former requires increasing the NA of the ninth objective lens for reading out or shortening the wavelength of the light source used, and is particularly limited by the wavelength of the light source. Moreover, the latter is the total amount of information (
Since the capacity (capacity) does not increase, playback time decreases.

[Purpose of the invention]

In view of the above conventional problems, an object of the present invention is to provide an optical information processing device capable of increasing both the capacity recorded on an information medium and the reproduction rate without increasing the spatial frequency thereof. That's true.

[Summary of the invention]

This invention provides information sound recorded on the information surface of an optically readable information medium having at least two information surfaces, a light source of at least two cumulative wavelengths, and a light beam from the light source. This is an optical information processing device that reads out information using a reproducing optical system that includes a grating type objective lens that condenses and irradiates the information surface onto the information surface.

[Embodiments of the invention]

The optical information processing device according to the present invention is shown in FIGS.
First, the information medium configured as shown in the figure and used in the present invention will be explained.

That is, this information medium 5 is configured as shown in FIG.
The protective cover layer includes a filter layer 2 in which a first information pit is formed, which reflects a first wavelength shown by a solid line and transmits a second wavelength shown by a broken line, and a grating type objective lens (
(described later) and the first and second wavelengths λl, λ:
A transparent layer 3 having a desired thickness tt determined from tt and a second information pit are formed, and a reflective film 4ftllj that reflects at least the second wavelength is laminated.

The thickness t of the transparent layer 3 is determined by the wavelength λ1 of the grating type objective lens and the focal length f1mf2 for each wavelength λ1.
The relationship is fl x λ13f x λ, and fzy4tmaλz=0.78μm.

If it is 21w0.8, f1m3.9sam),
t W 0. It becomes I Ill.

Next, the optical system (
For example, an optical pickup head) is constructed as shown in FIG.
The light sources 22 are arranged adjacent to each other. A collimating lens 23, a beam splitter 24, and a grating type objective lens 25 are sequentially disposed at predetermined intervals on a coaxial line with each of the light sources 21 and 22.

Further, in a direction perpendicular to the beam splitter 24, a filter 26, a second detection lens system 30. Second photodetectors 28 are sequentially arranged at predetermined intervals. or,
In the direction orthogonal to the filter 26, a first detection lens system 29 and a first photodetector 27 are sequentially arranged at a predetermined interval.

In the above case, the collimating lens 23 is connected to each light source 21.2.
This is to collimate the output beam from 2. or,
The filter 26 is for separating the reflected light from the information medium 5 into wavelengths λl and λ1 after being separated by the beam filter 24. Furthermore, photodetectors 27 and 28 detect reflected beams of wavelengths λ1 and λ, and are composed of, for example, photodiodes. In addition, the detection lens system 2
Reference numeral 9.30 is for condensing the reflected beam onto the photodetector 21.28, and at least one of these detection lens systems 29.30 is designed to detect the misalignment (deviation) between the focal plane of the information medium 5 and the objective lens 25. The lens includes an optical system for detecting focus (focus), for example, an astigmatic optical system.

Now, during operation, the wavelength λ emitted from the first light source 21
The first beam is converted into a parallel beam by the collimating lens 23, is focused into a minute spot on the first information pit surface of the information medium 5 by the objective lens 25, is modulated by the pit, is reflected by the filter layer 2, and is then transformed into a parallel beam by the objective lens 25. The reflected beam, which is focused by the objective lens) e25 and guided to the detection side by the beam sinter 24, passes through the first detection lens system 29 to the first photodetector (P
DI) 27 and detected.

At this time, simultaneously with the information signal, the aforementioned defocus amount (focus error) and the deviation of the irradiation spot from the center of the pit row (track) (tracking error) are detected, and the obtained error signal is transmitted to the objective lens 25 on two axes. Feedback is sent to the driving mechanism to correct each error.

Further, as in the case of wavelength λ1, the wavelength λ beam emitted from the second light source 22 is converted into a parallel beam by the collimating lens 23, passes through the filter layer 2 by the objective lens 25, and is transmitted to the information medium 5. The second information pit surface is convergently irradiated with a minute spot, modulated by the pit, reflected by the reflective surface, and separated by the filter 26 as in the case of the wavelength λl,
A second photodetector (PD
2),? The light is focused on s and detected.

At this time, if the thickness t of the transparent layer 3 is maintained at the accuracy of the depth of focus Δf of the objective lens 25, and the relative positions of the first and second tracks are maintained at a sufficiently small value compared to the pit width. , wavelengths λ1 and λ.

emit light at the same time, and use the error signal of wavelength λ1 as a focus sensor? If you apply tracking surge, you can detect both types of information at the same time.

Therefore, the amount of information per unit time can be reduced by 2 without reducing the pit size or increasing the scanning speed.
Can be doubled.

[Modified example of the invention]

By applying this invention, it is possible to create an optical memory with a large recording capacity by pre-recording information such as subcodes on one information surface and making the other information surface a recordable surface.

Further, the present invention is applicable to the above-mentioned embodiments as long as it is an optical information processing device comprising an optical system including a multi-wavelength light source, a grating type objective, and an information medium having a multilayer structure. It is not limited to.

Furthermore, the optical system is not limited to the configuration shown in the above embodiment.

〔Effect of the invention〕

According to this invention, both the capacity recorded on the information medium 5 and the reproduction rate can be increased without increasing its spatial frequency.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an information medium in an optical information processing apparatus according to an embodiment of the present invention, and FIG. 2 is a configuration diagram showing the optical system. DESCRIPTION OF SYMBOLS 1... Protective cover, 2... Filter layer, 3... Transparent layer, 4... Reflective layer, 5... Information medium, 21...
First light source, 22... Second light source, 23... Collimating lens, 24... Beam splitter -125.-
- Objective lens, 26... filter, 27... first photodetector, 28... second photodetector, 29... first
detection lens system, 30... second detection lens system. Applicant's agent Patent attorney Takehiko Suzue Figure 1

Claims (3)

[Claims] (1) Information recorded on the information surface of an optically readable information medium having at least two information surfaces is transmitted to the information surface using a light source of at least two different wavelengths and a light beam from the light source. What is claimed is: 1. An optical information processing device characterized in that reading is performed using a reproducing optical system comprising a grating type objective lens that condenses and irradiates light onto a target. (2) Optical information processing according to claim 1, characterized in that information recorded on each information surface of the information medium can be simultaneously read out using light beams of different wavelengths. Device. (3) The information medium has a multilayer structure in which information is recorded in concave or convex pit rows on both sides of a single transparent plate, one side of which is a reflective surface, and the other side of which is a transparent protective cover. The first claim characterized in that
The optical information processing device described in Section 1.