JPH0482028A - Information recording and reproducing device - Google Patents

Abstract

PURPOSE:To eliminate a need of a band-pass filter by forming a dielectric multilayered film which reflects recording light to a converging lens and allows only reproducing light to pass through. CONSTITUTION:The dielectric multilayered film having a spectral characteristic is vapor-deposited to the curvature face of a toric lens 33 on the side of a polarizing beam splitter 28. For example, light having 780nm wavelength is transmitted through but the other light is reflected by this spectral characteristic. Consequently, light having 780nm wavelength reflected by the polarizing beam splitter 28 is transmitted through a toric lens 33. Meanwhile, light having 830nm wavelength is reflected by the toric lens 33, and waveform selective transmission is performed in the same manner as a band-pass filter. Thus, the band-pass filter is unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a two-light source type information recording and reproducing apparatus that is provided with a recording light source and a reproducing light source separately.

[Prior Art] Conventionally, various types of information media such as disk-shaped, card-shaped, tape-shaped, etc. are known for recording and reproducing information using light. These optical information recording media include those capable of recording and reproduction, and those capable of only reproduction. Information is recorded on a recordable medium by scanning an information track with a light beam that is modulated according to the recording information and focused into a minute spot, and the information is recorded as a row of information pits that can be compared optically. recorded.

Furthermore, in order to reproduce information from a recording medium, the information bit string of the information track is scanned with a light beam spot of a certain power that does not cause recording on the medium, and the reflected light or transmitted light from the medium is detected. It is done by doing.

The optical head used for recording and reproducing information on the recording medium described above is movable relative to the recording medium in the direction of the information track and in a direction crossing the direction, and this movement changes the light beam spot. An information track scan is performed. For example, an objective lens is used as a lens for narrowing down the light beam spot in the optical head.

This objective lens is in its optical axis direction (focusing direction)
The optical head body is held in a direction perpendicular to both the optical axis direction and the information track direction of the recording medium (tracking direction) so as to be able to move independently in each direction. Holding such an objective lens is −
11Q via an elastic member, and the above-mentioned 2 of the objective lens
Directional movement is generally driven by an actuator using magnetic interaction.

By the way, among the above-mentioned optical information recording media, card-shaped optical information recording media (hereinafter referred to as optical cards) are
It is expected that there will be great demand in the future as a relatively large-capacity information recording medium that is small, lightweight, and convenient to carry.

FIG. 3 is a schematic plan view of the write-once optical card, and FIG. 4 is a partially enlarged view thereof.

In FIG. 3, on the information recording surface of the optical card 1, a large number of information tracks 2 are arranged in parallel in the LF direction.

Further, a home position 3 is provided on the information recording surface of the optical card 1, which serves as a reference position for accessing the information track 2. The information track 2 is arranged in order of 2-1, 2-2, 2-3, from the one closest to the home position 3. ..., and as shown in Fig. 4, tracking tracks are arranged adjacent to each of these information tracks in the order of 4-1.4-2゜4-.
3. They are set up sequentially like this. These tracking tracks 4 are used as guides for auto-tracking (hereinafter referred to as AT) that controls the beam spot so that it does not deviate from a predetermined information track when scanning the optical beam spot during information recording and reproduction. .

This AT servo detects the deviation of the optical beam spot from the information track (AT error) in the optical head,
This is done by feeding the detection signal back to the tracking actuator and moving the objective lens in the tracking direction (direction D) with respect to the optical head body to cause the light beam spot to follow the desired information track.

Additionally, when scanning an information track with a light beam spot during information recording and reproduction, autofocusing (hereinafter referred to as , AF) servo is performed. This AF servo detects the deviation of the optical beam spot from the focused state (AP error) in the optical head, feeds the detection signal back to the focusing actuator, and moves the objective lens in the focusing direction with respect to the optical head body. This is done by moving the light beam to focus the light beam spot on the surface of the optical card.

In addition, in FIG. 4, Sl, S2. S3 indicates a light beam spot, the light spots S1 and 83 are used for tracking, and the light spot S2 is used for focusing, creating information pits during recording, and reading information pits during playback. Furthermore, in each information track, 6-1, 6-2 and 7-1, 7-2 indicate the preformatted left side address field and right side address field, respectively, and by reading these address fields, the track can be identified. It is done. 5 (corresponding to 5-1 and 5-2 in the figure) is a data section in which predetermined information is recorded.

Here, the method of optical information recording will be briefly explained. Conventionally, there are two main types of optical information recording methods. One is a one-light source method in which recording and reproduction are performed using the same light source, and the other is a two-light source method in which recording and reproduction are performed using two different light sources. The two-light source method is said to be advantageous in terms of reproduction light deterioration and speedup compared to the one-light source method.

FIG. 5 shows a schematic diagram of a conventional two-light source type optical head optical system. The two-light source system uses separate light sources for recording light and reproducing light, thereby preventing deterioration of the reproducing light and enabling high-speed recording.

In FIG. 5, reference numerals 21 and 22 indicate semiconductor lasers serving as light sources. The semiconductor laser 21 emits light at a wavelength of 780 nm, and the semiconductor laser 22 emits light at a wavelength of 830 nm.

23 and 24 are collimator lenses, 25 is a diffraction grating for beam splitting, 26 is a dichroic prism designed to transmit 780 nm light of the P-polarized component and reflect 830 nm light, and 27 is a beam shaping device. Prism, 2
8 is a polarizing beam splitter. Further, 29 is a 174 wavelength plate, 30 is an objective lens, 31 is a band pass filter that transmits only light of 780 nm, 32 is a stopper, 33 is a toric lens, and 34 is a photodetector.

The light beams emitted from the semiconductor lasers 21 and 22 enter the collimator lens 2324 as a divergent light beam, and are corrected into a parallel light beam by the lens. The 780 nm light further enters the diffraction grating 25, and the diffraction grating forms three effective light beams (O-order diffraction light and ±1st-order diffraction light).
divided into The above 780 nm light beam and 830 nm
The nm light beam enters the dielectric multilayer film laminated on the adhesive surface of the dichroic prism 26 having spectral characteristics as shown in FIG. 6 as a P-polarized light component. and 780
The 830 nm light beam is transmitted, the 830 nm light beam is reflected, and both light beams are combined. The light beam passing through the dichroic prism 26 passes through the light beam shaping prism 2
7, the light is shaped into a predetermined light intensity distribution and then enters the polarizing beam splitter 28. Here again, both beams of 780.830 nm have P polarization components and are transmitted through the junction surface of the polarizing beam splitter 28 having the spectral characteristics as shown in FIG.

These two wavelength light beams are then passed through a 174-wave plate 29.
When the light passes through the light, it is converted into circularly polarized light and is focused by the objective lens 3o. And the 780 nm light beam is
Three minute beam spots Sl (+1st-order diffracted light), 52 (O-th order diffracted light), and S3 (-1st-order diffracted light) are irradiated onto the optical card 1, and are used as reproduction light and signal light for AT and AF control. Moreover, the light beam of 830 nm is 5
The light beam is irradiated onto the optical card 1 as a minute beam spot of 2nd (O-order diffracted light) and used as recording light.

The light beam spot position on the optical card l is the same as that in FIG. 4, and is the light beam spot Sl.

S3 is located on the adjacent tracking track 4, and the light beam spot S2 is located on the information track 2 between the tracking tracks. Also, 82 and 8 of 780 nm
The positional relationship of 30 nm S2 is slightly 830 which is recording light.
Although it is better for the nm light beam spot S2 to be located in the traveling direction, it is free in principle, and in this example they match. (Thus, the reflected light from the light beam spot formed on the optical card passes through the objective lens 30, becomes almost parallel, and passes through the 174-wave plate 29 again, so that the polarization direction is changed from that at the time of incidence.) The light beam is rotated by 90 degrees.Therefore, it enters the polarizing beam splitter 28 as an S-polarized beam, and this splitter 28 has an S-polarized beam as described above.
Since the polarized light is reflected, the light beam passes through the bandpass filter 3.
reflected to the first side. Then, by using the bandpass filter 31 to transmit only light around 780 nm and reflecting light at other wavelengths, only the light at 780 nm is used for signals. The light that has passed through the bandpass filter 31 is focused by the toric lens 33 and enters the photodetector 34. The photodetector 34 has a configuration as shown in FIG. 8, and performs tracking control using the light receiving signals from the light receiving elements 11 and 13, and performs focus control and reproduction using the light receiving signals from the light receiving element 12, which is divided into four elements. Perform signal detection.

[Problems to be Solved by the Invention] However, in the conventional example described above, there is a problem that the proportion occupied by the optical system becomes large, such as the need for two semiconductor lasers. That is, the optical head is required to be smaller and lighter, and thereby faster access time is desired. However, as mentioned above, the increase in the number of optical components hinders the miniaturization of the optical head and becomes an obstacle to increasing the speed.

The present invention was made in view of the above circumstances, and its purpose is to effectively reduce the number of parts even in the case of a two-light source type, thereby making the optical head smaller and lighter. The goal is to provide equipment.

[Means for solving the problem] In order to achieve the above object, two light sources are used that emit a recording light beam and a reproduction light beam with different wavelengths, and the incident light from these light sources and the reflected light from the recording medium are separated. In the information recording/reproducing apparatus, the information recording/reproducing apparatus includes a polarizing beam splitter that detects reflected light from the medium separated by the beam splitter, and a photodetector that detects reflected light from the medium separated by the polarizing beam splitter. There is provided an information recording and reproducing device characterized in that a dielectric multilayer film that reflects the recording light beam and transmits the reproduction light beam is formed on the lens surface on which the reflected light is focused and incident.

[Examples] Examples of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a two-light source type optical head optical system in an information recording/reproducing apparatus of the present invention. In FIG. 1, parts that are the same as those of the conventional device are given the same reference numerals.

In Fig. 1, 21 is 780r+ used as reproduction light.
A semiconductor laser 22 emits a light beam of 830 nm, which is used as recording light. The luminous flux of these semiconductor lasers 21°22 is
The reflected light enters the polarizing beam splitter 28 again.
However, the contents up to this point are all the same as those explained for the conventional device, so the explanation will be omitted.

This embodiment is characterized by a toric lens 33 that focuses two light beams reflected by the polarizing beam splitter 28. That is, a dielectric multilayer film having spectral characteristics as shown in FIG. 2 is deposited on the curvature surface of the toric lens 33 on the polarizing beam splitter 28 side. As is clear from FIG. 2, the spectral characteristics are such that light of 780r+m is transmitted and the rest is reflected. Therefore, the 780 r reflected by the polarizing beam splitter 28
The ON light passes through the toric lens 33 according to the spectral characteristics shown in FIG. On the other hand, the light of 830 nm is reflected by the toric lens 33, and selective transmission of wavelengths similar to a band pass filter is performed.

As a result, only the light of 780 nm can be transmitted through the toric lens 33.
The light is transmitted therethrough, where it is focused and incident on the photodetector 34.

The photodetector 34 includes the light receiving element 11 as shown in FIG.
．． It is composed of a light receiving element 12 divided into 13 and 4 parts, and these light receiving signals are used to perform reproduction of recorded information, tracking, or acushing control.

Here, since the light reflected from the toric lens 33 is reflected according to the curvature of the toric lens 33, it becomes a diverging light, and except for some light, it deviates from the optical path of the optical system. Furthermore, the amount of light remaining in the optical path of the optical system is very small, and since it is also diverging light, it gradually leaves the optical path of the optical system, and the amount of light also decreases accordingly. Furthermore, since it is a diverging light, it may not be visible on the optical card 1 or on the semiconductor laser 22.
It does not focus on the light emitting point of the light. From the above,
Since the light reflected by the toric lens 33 does not become noise, it does not interfere with the operation of the apparatus.

In the above embodiment, the dielectric multilayer film is deposited on the curved surface side of the toric lens 33, but it is more effective to deposit it on both sides.

Furthermore, a similar effect can be obtained by depositing a dielectric multilayer film on the opposite surface of the toric lens 33. In this case, the surface of the toric lens 33 may be arranged not at right angles to the optical axis (but at an angle).

[Effects of the Invention] As explained above, according to the present invention, a dielectric multilayer film is formed on the focusing lens that reflects the recording light and transmits only the reproduction light, thereby eliminating the need for a bandpass filter that was previously required. It can be made unnecessary.

Therefore, by reducing the number of parts, the spectroscopic head can be made smaller and lighter, which has the effect of increasing speed.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the optical head optical system in the information recording and reproducing apparatus of the present invention, FIG. 2 is a characteristic diagram showing the spectral characteristics of the dielectric multilayer film deposited on the focusing lens, and FIG.
4 is a partially enlarged view of the optical card, FIG. 5 is a configuration diagram of a conventional two-light source type optical head optical system, and FIG. 6 shows the spectral characteristics of the dichroic prism 26. FIG. 7 is a characteristic diagram showing the spectral characteristics of the polarizing beam splitter 28, and FIG. 8 is an explanatory diagram showing the light receiving surface of the photodetector. 1... Optical card 21.22... Semiconductor laser 23.24... Collimator lens 25... Diffraction grating 26... Dichroic prism 28... Polarizing beam splitter 29... 174 wavelength plate 30. ...Objective lens 33...Toric lens

Claims (4)

[Claims] (1) Two light sources that emit recording and reproducing light beams with different wavelengths, a polarizing beam splitter that separates the incident light from these light sources and the reflected light from the recording medium, and the beam splitter that separates the and a photodetector for detecting reflected light from the medium, the information recording and reproducing apparatus comprising: a lens surface on which the reflected light from the medium separated by the polarizing beam splitter is focused and incident on the photodetector; An information recording and reproducing device characterized in that a dielectric multilayer film is formed that reflects the recording light beam and transmits the reproducing light beam. (2) The information recording and reproducing device according to claim 1, wherein the dielectric multilayer film is formed on the curvature surface side of the focusing lens. (3) The information recording and reproducing device according to claim 1, wherein the dielectric multilayer film is formed on both surfaces of the converging lens, one on the curvature side and the other on the flat side. (4) Information recording and reproducing according to claim 1, wherein the dielectric multilayer film is formed on the plane side of the focusing lens, and the focusing lens is arranged at an angle so as not to be orthogonal to the optical axis. Device.