JP2579102B2 - Optical information recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-light source information recording / reproducing apparatus provided with a recording light source and a reproduction light source separately.

[0002]

2. Description of the Related Art Conventionally, various types of information media such as a disk, a card, and a tape have been known as information media for recording and reproducing information using light. These optical information recording media include those capable of recording and reproduction and those capable of reproduction only. Information is recorded on a recordable medium by scanning the information track with a light beam modulated according to the recording information and narrowed down into a minute spot, and the information is recorded as an optically detectable information pit string. Is done.

In order to reproduce information from a recording medium, an information pit array on an information track is scanned with a light beam spot having a constant power so that recording is not performed on the medium. This is performed by detecting transmitted light.

[0004] The optical head used for recording and reproducing information on and from the recording medium described above is relatively movable with respect to the recording medium in the information track direction and in the direction crossing the direction. Information track scanning of the beam spot is performed. As a lens for narrowing a light beam spot in the optical head, for example, an objective lens is used. The objective lens moves independently of the optical head body in the optical axis direction (focusing direction) and the direction (tracking direction) orthogonal to both the optical axis direction and the information track direction of the recording medium. Is held so that you can. Such holding of the objective lens is generally performed through an elastic member, and the movement of the objective lens in the two directions is generally driven by an actuator utilizing magnetic interaction.

[0005] Among the above-mentioned optical information recording media, a card-shaped optical information recording medium (hereinafter, referred to as an optical card) is a small and light-weight, relatively portable, large-capacity information recording medium. Large demand is expected.

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

In FIG. 3, a large number of information tracks 2 are arranged on the information recording surface of the optical card 1 in parallel with the LF direction. On the information recording surface of the optical card 1, a home position 3 serving as a reference position for accessing the information track 2 is provided. The information tracks 2 are arranged in the order of 2-1, 2-2, 2-3,... From the side closer to the home position 3, and as shown in FIG. -1,4-2,4
-3,... Are sequentially provided. These tracking tracks 4 are used as guides for auto tracking (hereinafter, referred to as AT) for controlling the beam spot so as not to deviate from a predetermined information track when scanning a light beam spot during information recording and reproduction. . The AT servo detects a deviation (AT error) of the light beam spot from the information track in the optical head, gives a negative feedback of the detection signal to the tracking actuator, and moves the objective lens to the optical head body in the tracking direction ( (D direction) to cause the light beam spot to follow a desired information track.

In information recording and reproduction, when an information track is scanned with a light beam spot, the light beam is formed into an appropriately sized spot on the optical card surface (focusing). Focusing (hereinafter, referred to as AF) servo is performed. The AF servo detects a deviation (AF error) of the light beam spot from the in-focus state in the optical head, feeds back the detection signal to the focusing actuator, and moves the objective lens to the optical head body in the focusing direction. To focus the light beam spot on the optical card surface.

In FIG. 4, S1, S2, and S3 indicate light beam spots. Tracking is performed using the S1 and S3 light spots, and information pits during focusing and recording are performed using the S2 light spot. And read information pits during reproduction. In each information track, 6-1 and 6-2 and 7-1 and 7-2 indicate a preformatted left address portion and a right address portion, respectively. By reading these address portions, the track identification can be performed. Done. Numeral 5 (corresponding to 5-1 and 5-2 in the figure) is a data part, in which predetermined information is recorded.

Here, the method of optical information recording will be briefly described. Conventionally, there are roughly two types of optical information recording systems. One is a one light source system in which recording and reproduction are performed by the same light source, and the other is a two light source system in which recording and reproduction are performed by two different light sources. It is said that the two-light source method is more advantageous than the one-light source method in terms of reproduction light deterioration and speeding up.

FIG. 5 is a schematic view of an optical head optical system of a two light source system. The two light source system uses different light sources for recording light and reproduction light, thereby preventing deterioration of reproduction light and enabling high-speed recording. Here, two beam shaping prisms are used.

In FIG. 5, reference numerals 21 and 22 denote semiconductor lasers as light sources. The semiconductor laser 21 emits light having a wavelength of 780 nm, and the semiconductor laser 22 emits light having a wavelength of 830 nm. 23,
24 is a collimator lens, 25 is a diffraction grating for splitting a light beam, 41 and 42 are apertures 26 and 78 are P polarization components.
A dichroic prism designed to transmit 0 nm light and reflect 830 nm light, 27 and 27 ′ are beam shaping prisms, and 28 is a polarization beam splitter. 29 is a quarter-wave plate, 30 is an objective lens, 31
Is a bandpass filter that transmits only 780 nm light, 3
2 is a stopper, 33 is a toric lens, and 34 is a photodetector.

The light beams emitted from the semiconductor lasers 21 and 22 become divergent light beams and collimator lenses 23 and 2.
4 and is corrected by the lens into a parallel light beam. The light of 780 nm further enters the diffraction grating 25,
The diffraction grating divides the light into three effective light beams (0th-order diffracted light and ± 1st-order diffracted light).

The 780 nm light beam and the 830 nm light beam are respectively shaped into circular light intensity distributions by light beam shaping prisms 27 and 27 ′, and then are incident on apertures 41 and 42 to have a predetermined light intensity. Only the luminous flux of the distribution is transmitted.

The predetermined light intensity distribution means that the 780 nm light spot used as a reproduction spot has an elliptical shape, and the 830 nm light spot used as a recording spot has a circular light intensity distribution.
1 has an elliptical opening, and the aperture 42 has a circular opening.

Further, the light beam of 780 nm and 83
The 0 light beam is incident as a P-polarized light component on the dielectric multilayer film laminated on the bonding surface of the dichroic prism 26 having the spectral characteristics as shown in FIG. And 780nm
Is transmitted, the 830 nm light beam is reflected, and both light beams are combined. The light beam that has passed through the dichroic prism 26 enters the polarization beam splitter 28. Here, too, 780 and 830 with respect to the joint surface of the polarization beam splitter 28 having the spectral characteristics as shown in FIG.
Both beams of nm have a P polarization component and are transmitted.

Next, these two wavelength light beams are divided by 1 /
When transmitted through the four-wavelength plate 29, the light is converted into circularly polarized light, and is focused by the objective lens 30. Then, the 780 nm light beam forms three elliptical minute beam spots S1 (+ 1st-order diffracted light), S2 (0th-order diffracted light) on the optical card 1,
Irradiated as S3 (-1st order diffracted light), reproduced light and A
Used as signal light for T and AF control. The reason why the reproduction light spot has an elliptical shape is known because it is difficult to lose AT. The 830 nm light beam is
The light beam is irradiated onto the optical card 1 as a minute beam spot of S2 (zero-order diffracted light) and used as recording light.

The positions of the light beam spots on the optical card 1 are the same as in FIG.
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. In addition, S2 of 780 nm and 830
The positional relationship of S2 in nm is 830 nm, which is slightly
It is better that the light beam spot S2 is located in the traveling direction, but it is free in principle and coincides in this example. Thus, the reflected light from the light beam spot formed on the optical card 1 is made substantially parallel through the objective lens 30 and passes through the quarter-wave plate 29 again, so that the polarization direction is changed from that at the time of incidence. It becomes a light beam rotated by 90 °. Therefore, the beam enters the polarizing beam splitter 28 as an S-polarized beam, and the splitter 28
Since the polarized light is reflected, the light beam passes through the band-pass filter 3.
It is reflected to one side. Then, only light near 780 nm is transmitted by the bandpass filter 31 and light of other wavelengths is reflected, so that only 780 nm light is used for signals. The light transmitted through the bandpass filter 31 is focused by the toric lens 33 and enters the photodetector 34. The photodetector 34 is configured as shown in FIG. 8 and performs tracking control with the light receiving signals of the light receiving elements 11 and 13, and performs focus control and reproduction signal with the light receiving signal of the light receiving element 12 which is a four-divided element. Perform detection.

[0019]

However, in the conventional configuration as shown in FIG. 5, first, a light beam having a circular intensity distribution is converted by a beam shaping prism, and an aperture is applied to the light beam to obtain a circular and elliptical light beam. In this configuration, two beam shaping prisms must be used for the recording light and the reproducing light, and (1) the cost is increased, and (2) the space is increased. There is a problem that it becomes larger.

(Object of the Invention) An object of the present invention is to improve the arrangement positions of the aperture and the beam shaping prism so that two beam shaping prisms conventionally arranged can be constituted by one common beam shaping prism. Another object of the present invention is to provide an optical information recording / reproducing apparatus with reduced cost, and improved space efficiency.

[0021]

According to the present invention, as a means for solving the above-mentioned problems, a recording light for emitting a recording light is provided.
Source and a divergent light beam emitted from the recording light source as parallel light.
A first collimator lens for converting into a bundle and emitting a reproduction light
Light source for reproduction, and divergent light emitted from the light source for reproduction
A second collimator lens for converting the light beam into a parallel light beam;
The first collimator lens and the second collimator lens
Combining means for combining two parallel light beams from the lens,
The light beam that has passed through the combining means is shaped into a light beam having a desired light intensity distribution.
And a beam shaping prism.
Recording information by irradiating the recording medium with a light beam that has passed through the
Or in an optical information recording and reproducing apparatus for reproducing, the first
1 between the collimator lens and the combining means.
The spot shape of the recording light on the recording medium is circular.
A first aperture for forming the second collimator;
Data lens, and the recording means
The spot shape of the reproduction light on the medium is made elliptical.
And a second aperture for
Information recording and playback device.

The first aperture and the second aperture
Is characterized by having an elliptical shape.

[0023]

[0024]

According to the present invention, by arranging an aperture in consideration of a beam shaping ratio in advance in a parallel light beam having an elliptical intensity distribution after passing through a collimating lens, a beam shaping prism can be used to reproduce a recording light beam. It is possible to use one beam shaping prism instead of two conventionally required separate beam shaping prisms.

The aperture is designed to have a desired light intensity distribution when the light beam is converted by the conversion ratio of the beam shaping prism after passing through the aperture, and the aperture has a long diameter. A desired light spot can be obtained by forming the light beam emitted from the light source into an elliptical shape having a ratio of the divergence angle in the horizontal direction and the vertical direction of the light beam emitted from the light source.

As described above, the shape of the aperture is determined by the size of the spot diameter to be obtained on the medium.

[0027]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of an optical head optical system of a two light source type in the information recording / reproducing apparatus of the present invention. In FIG. 1, the same parts as those in the apparatus described in FIG. 5 are denoted by the same reference numerals.

The operation is almost the same as that described in connection with the apparatus shown in FIG. 5, so that the description will be omitted, and the operation of the apertures 41 'and 42' different from the conventional example shown in FIG. 5 will be described in detail. .

FIG. 2 is a schematic diagram comparing the operation of the apertures 41 and 42 in the conventional example shown in FIG. 5 with the operation of the apertures 41 'and 42' in the present invention.

In the example shown in FIG. 5, both the 780 nm light as the reproduction light and the 830 nm light as the recording light are expanded (doubled) in the horizontal direction of the drawing by the beam shaping prism to have a circular light intensity distribution.

Thereafter, the luminous flux is cut by an aperture designed so that the spot shape on the card is circular or elliptical.

This aperture uses an elliptical shape to obtain an elliptical spot, and a circular shape to obtain a circular spot.

On the other hand, the aperture shape used in the configuration of the present invention is a shape in consideration of the magnification factor of the beam shaping prism in advance, and is a vertically long elliptical shape in the use state of the present invention.

Still further, in the aperture, the ratio of the major axis to the minor axis (major axis / minor axis) of the opening is the ratio of the divergence angle of the light beam emitted from the light source in the horizontal direction and the vertical direction (vertical direction / horizontal direction). An elliptical shape that is almost equal to

In this embodiment, the apertures 41 'and 42' having such a shape are arranged after the collimator lenses 23 and 24, and the transmitted light is enlarged by one common beam shaping prism 27. . As shown in FIG. 2, it can be seen that the intensity distribution of the light spot on the card of the present invention is exactly the same as in the conventional example.

Therefore, by arranging the aperture designed in advance in consideration of the beam shaping ratio between the collimator lens and the beam shaping prism, and at a position where the recording light beam and the reproduction light beam are separated, as shown in FIG. The beam shaping prism can be reduced by one with the same performance as that of the conventional example.

[0038]

As described above, the aperture taking the beam shaping ratio into consideration is arranged between the collimator lens and the beam shaping prism, that is, in the light beam having a light intensity distribution having an elliptical shape. Is shared by the recording light beam and the reproduction light beam, the number of the beam shaping prisms conventionally arranged in two can be reduced to one, whereby a great effect of reducing cost and improving space efficiency can be obtained. be able to.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical head optical system of a two light source system embodying the present invention.

FIG. 2 is a diagram comparing the effects of the conventional example shown in FIG. 5 and the aperture of the present invention.

FIG. 3 is a plan view of the optical card.

FIG. 4 is a partially enlarged view of an optical card.

FIG. 5 is a configuration diagram of a conventional two-light source type optical head optical system.

FIG. 6 is a characteristic diagram showing spectral characteristics of the dichroic prism 26.

FIG. 7 is a characteristic diagram showing spectral characteristics of the polarization beam splitter 28.

FIG. 8 is an explanatory diagram showing a light receiving surface of the photodetector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical card 21, 22 Semiconductor laser (light source) 23, 24 Collimator lens 25 Diffraction grating 26 Dichroic prism 27, 27 'Beam shaping prism 28 Polarization beam splitter 29 Quarter-wave plate 30 Objective lens 33 Toric lens 34 Photodetector 41 , 42 aperture 41 ', 42' aperture

Claims (2)

(57) [Claims] A recording light source for emitting recording light;
For converting the divergent light beam emitted from the light source into a parallel light beam
1 collimator lens and a reproduction light source that emits reproduction light
And a divergent light beam emitted from the reproducing light source as a parallel light beam.
A second collimator lens for converting the
2 from the meter lens and the second collimator lens
Combining means for combining two parallel light beams;
Beam shaping that transforms the luminous flux into a luminous flux with a desired light intensity distribution
Prism, and light passing through the beam shaping prism
Recording and / or reproducing information by irradiating the bundle with a recording medium
In an optical information recording / reproducing apparatus, an optical information recording / reproducing device is provided between the first collimator lens and the synthesizing means.
And a spot shape of the recording light on the recording medium.
A first aperture for forming a circular shape, and a second aperture disposed between the second collimator lens and the combining means.
And a spot shape of the reproduction light on the recording medium.
An optical information recording / reproducing apparatus , comprising: a second aperture for forming an elliptical shape . 2. The first aperture and the second aperture.
2. The aperture according to claim 1, wherein the aperture has an elliptical shape.
The optical information recording / reproducing apparatus according to claim 1.