JPS5977642A - Optical head - Google Patents

Abstract

PURPOSE:To generate a signal indicating the presice position of a condenser lens to an optical head by moving the condenser lens, a beam splitter and a mirror simultaneously in the tracking direction and by detecting the reflected light through the beam splitter by two-divided optical sensors. CONSTITUTION:The laser light from a semiconductor laser 2 is made incident to the beam splitter 21 through a polarized beam splitter 5 and divided into two light rays by the reflected surface 23 and the transmitted light is changed at its optical path rectangularly and condensed on a recording medium 17 through a condenser lens 7 as an optical spot 16. The reflected light from the recording medium 17 is made incident from the reflecting surface 8 of a polarized beam splitter to two-divided optical sensors 19, 20 through a half mirror 9 to detect a focal position error and a tracking position error. On the other hand, the reflected light from the beam splitter 21 is made incident to a two-divided optical sensor 18 and the output of the sensor 18 moves the condenser lens 7, the beam splitter 21 and the mirror 22 simultaneously in the tracking direction.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical device for recording information on a recording medium or for reading information already recorded on a recording medium using optical means.

A laser beam is used as a light source, and this laser beam is modulated with a pulsed signal from an external information source and recorded on the recording medium on the disk surface in a 211f manner, or the already recorded eyebrow 7
In order to accurately read out the information recorded by the optical head (in this case, information recording or +!-), the focal point of the condensing lens is adjusted to the surface of the recording medium using focus control. , C
, :r position, the device control of the condensing lens in the Ms41+ direction is performed.In addition, the trasokink position control r wholesale that appears on the information track of the light spot is controlled so that the condensing lens is positioned at A guide groove with a width suitable for the light spot and a depth suitable for the wavelength of the laser beam used is provided, and the condenser lens is placed perpendicular to the guide groove so that the light spot follows the guide groove. This is done by driving in the tracking drive direction.

Furthermore, track access of the optical spot is normally performed within a narrow range by moving only the condensing lens in the tracking drive direction φ by a tracking actuator inside the optical head, and conversely, in a wide range, the tracking actuator inside the optical head moves only the condensing lens in the tracking drive direction. This is done by moving the entire optical head using an actuator. In such a two-stage automatic system, when the optical spoiler is following the information track, the position of the optical head is controlled so that the condenser lens is located at the center of the opening range of the tracking actuator. Furthermore, when accessing a wide range of tracks, in order to suppress the vibration of the condensing lens near the stop position, the condensing lens should be fixed at a certain position within the optical haird. Is it desirable to move the optical head? However, in order to achieve such a two-stage ZARPO method, it is necessary to accurately detect the position of the condenser lens relative to the optical head, and in the conventional two-stage ZARPO method, the position of the condenser lens relative to the optical head must be accurately detected. Since it is impossible to accurately detect the position of the focusing lens, a position sensor dedicated to the external actuator is usually used, and the external γ actuator and the optical head driven by it are the output of this position sensor. Position control is performed based on the position signal, and position control of the condenser lens is performed based on the position signal of the light spot relative to the guide groove. In this way, the condenser lens and optical head are
Because each position is controlled independently, the movement of the internal actuator does not reflect the movement of the external actuator, making it impossible to follow a track over a wide range.Furthermore, when accessing a track, the optical head is directed toward the target track at high speed. When the condenser lens is moved in the vicinity of the stop position, vibrations occur in the condensing lens, and the trunk following operation cannot be performed until the vibrations subside, which has the drawback of requiring additional track access time due to the waiting time. As explained above, it has been impossible to improve the performance of an optical information recording/reproducing device using conventional optical heads.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a new optical head capable of generating accurate position signals of the condenser lens relative to the optical head, in order to eliminate the above-mentioned drawbacks.

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a block diagram showing a first embodiment of an optical head according to the present invention. The laser beam emitted from the semiconductor laser 2 passes through a collimator lens 3 and a polarizing beam splitter 5.
, % wavelength plate 6, enters the beam splitter 21, and is split into two at the reflecting surface 23. Of the two split lights, the transmitted light passes through a mirror 22 that changes the optical path that was almost parallel to the recording medium 7 to a perpendicular direction, and a condensing lens 7 to form a light spot 1 on the recording medium 17.
6, and information is recorded or read out.

On the other hand, the reflected light from the recording medium 7 passes through the condensing lens 7, the mirror 22, the beam splitter 21, and the wavelength plate 6, enters the polarizing beam splitter 5, and passes through the reflecting surface 8. At this point, it is separated from the incident light from the semiconductor laser 2. The reflected light separated from the incident light enters the half mirror 9, where it is further divided into two parts. Ru. One of the divided lights passes through a convex lens 10 and a knife edge 11, and enters a two-split optical sensor 19, where a focus error is detected. This focus error detection method is a well-known technique known as the knife edge method, and the detected focus error signal is fed back to the focus control actuator 13 via a focus control circuit (not shown). the beano splitter 21 so that the focal point of the condensing lens 7 is always on the recording medium 17;
Only the condenser lens 7 in the tracking movable section 4 including the mirror 22 and the condenser lens 7 is driven in a direction substantially perpendicular to the recording medium 17 as indicated by an arrow 15.

Divided by the half mirror 911. The other reflected light is incident on the two-split optical sensor 20, and the tracking position error of the optical spot 16 with respect to the 1.7 knocking guide groove provided on the recording medium 17 (not shown) is detected. Action a1. Ru. This tracking position error detection method is a well-known method that has been known since the Pushinible method. The tracking position error signal is fed back to the tracking actuator 12 via a tracking control circuit (not shown), and the tracking actuator is adjusted so that the optical spot 16 is located at the center of the tracking guide groove. The unit 4 is driven in a tracking drive direction ζ parallel to the recording medium and equal to the optical axis of the incident light by an arrow 14. Said 1-ra, -Fng possible d
Ih Part 41 Kohaj) 11th Bi-no Suburi,, Evening 2
1. The mirror 22 is fixed, and the electric light/lens 7 is not fixed in the direction of the tracking driving force as indicated by the front ff1L arrow 14. Therefore, the racking movable part 15: As shown by the arrow 14, moves in the king driving direction (!:, the condensing lens 7 also moves in the same direction, and the front [, (- The light spot 16 is not shown by the arrow 14) 67 , , 4 tanta I, y; moving direction (this can be moved).

On the other hand, with the incidence from −11 semiconductor L---Li°2,
It was not reflected by the brick 21 where the beam entered at t'+i4.

W; enters into two divided beams - 18i. By doing this ζ, as will be explained in detail later, the arrow j
21.
f) Due to the χ1 difference, the last month that is incident on the two optical sensors of tijJi4 self-splitting optical sensor 18 is different, and 2
By calculating the difference between the two optical sensors, it is possible to obtain a signal proportional to the position. In other words, the position of the condensing lens 7 in the direction of the arrow 14 with respect to the optical head I including the above-mentioned semiconductor laser 2, etc. (Q) optical components can be detected, and as described above (4i)
1. The condenser lens 7 is connected to the tracking actuator 9-, J
Ni-ta 12? The center of the movable range ζ can be positioned, and the condensing lens 7 can be fixed at a fixed position within the optical system during dragging access, and track access is completed. It is possible to suppress the vibration of the condensing lens 7 during the time.

2(a) and 2(b) are enlarged views of the tracking movable part 4 and the two-split optical sensor 8 in FIG.
FIG. 4 is a diagram for easily explaining the position detection of the focusing lens 7 in the tracking direction relative to the optical head 1. FIG. 2(a) shows a case where the condenser lens 7 is located at the center of the movable range σ with respect to the optical head 1, and FIG. Indicates a case where there is a deviation.

In the same figure (a), the incident light 30 is transmitted to the beam splitter 2.
1, the recording medium 17 passes through the mirror 22 and the condensing lens 7
The light is focused on the upper spot 16, and the reflected light here follows the above-mentioned optical path in reverse, and as explained in FIG.
No. detection is performed. At this time, the reflected light from the beam splitter 21 is incident on the laser 18. In this figure, the above as −)'+'; Ii
Since the angle 7 is located at the center of the range, the incidence on the two-split optical sensor 18 is 5't;
~Jltl is (3
', fF-j-d), the amount of light received by the two optical sensors becomes very different, and the difference in output between the two optical sensors becomes extremely large). That is, place 1r1 - error fraction (',!
This indicates that there is no position error.

On the other hand, as shown in FIG.
If the beam splitter 2 is misaligned,
Since most of the incident light reflected by 1 is directed to one of the optical sensors in the 2-split human sensor → 18, the difference in output between the two 9 sensors is not zero; On the other hand, although it is not shown in the figure, if the condensing lens 7 is shifted in the opposite direction to the direction indicated by the arrow 31, Polarity indicates a value of opposite polarity.

As explained above, the condenser lens 7 and the beam splitter 2
1 and mirror 22 at the same time in the tracking direction,
By detecting the light reflected by the beam splitter 21 with the two-split optical sensor 18, the position of the condenser lens 7 in the tracking direction with respect to the optical head 1 can be detected.

Further, the wavelength plate 6 may be placed in the optical path from the beam splitter 21 to the condensing lens 7, and in this case, the property of polarization is used to direct the reflected light from the recording medium 17 to the beam splitter. The transmission efficiency in 21 can be increased.

FIG. 3 is a block diagram showing a second embodiment of the optical head according to the present invention. The laser beam emitted from the semiconductor laser 2 passes through a collimator lens 3 and a polarizing beam splitter 5, and enters a splitter 21 (which also has the function of a splitter 21) diagonally with respect to the optical axis, and is partially reflected at the incident surface. and the rest is passed through. This transmitted light is the recording medium 1
The light passes through a mirror 22 that changes the optical path that was almost parallel to the light beam 7 to a perpendicular direction, and a condenser lens 7, and is focused on a light spot 16 on the recording medium 17, thereby recording or reading information. On the other hand, the reflected light from the recording medium 17 passes through the condenser lens 7, the mirror 22, and the % wavelength plate 6, enters the polarizing beam splitter 5, and enters the reflective surface 8.
It is separated from the incident light from the semiconductor laser 2 at the point. The reflected light separated from the incident light is sent to the half mirror 9.
, where it is further divided into two parts. The split beam of light passes through a convex lens 10 and a knife edge 11, and enters a two-split optical sensor 1-19, where a focus error is detected.

This focus error detection method is a well-known technique known as the knife etching method, and the detected focus error signal is sent to the hot spot control actuator 13 via a focus control circuit (not shown in 1). returned and the recording medium 17
Only the condenser lens 7 in the tracking movable part 4 including the wavelength plate 6, the mirror 22, and the condenser lens 7 is indicated by an arrow 15 so that the focal position of the condenser lens 7 is always at the top. The recording medium 17 is driven in a direction substantially perpendicular to the recording medium 17.

The other reflected light split by the half mirror 9 is
The light is incident on the two-split optical sensor 20, and a tracking position error of the light spot 16 with respect to a tracking guide groove provided on the recording medium 17 (not shown) is detected. This tracking position error detection method is a conventionally well-known push-pull method, and the detected tracking position error signal is fed back to the tracking actuator 12 via a tracking control circuit (not shown). , the tracking movable section 4 is driven in a tracking drive direction parallel to the recording medium and equal to the optical axis of the incident light, as indicated by an arrow 14, so that the light spot 16 is located at the center of the tracking guide groove. The tracking movable part 4 includes the % wavelength plate 6,
Since the mirror 22 is fixed and the condenser lens 7 is fixed in the tracking drive direction shown by the arrow 14, the tracking movable part 4 is moved in the direction indicated by the arrow 14.
When the light spot 16 is moved in the tracking drive direction shown by arrow 14, the condenser lens 7 also moves in the same direction, and the light spot 16 can be moved in the tracking drive direction shown by arrow 14.

On the other hand, the incident light from the semiconductor laser 2 that is reflected by the % wavelength plate 6 enters the two-split optical sensor 18 .

By doing this, depending on the position of the % wave plate 6 in the direction shown by the arrow 14, the two parts of the two-part sensor 18 are
The amounts of light incident on the two optical sensors are different, and by calculating the difference between the two optical sensors, a signal proportional to the position can be obtained. In other words, the position of the condenser lens 7 in the tracking direction indicated by the arrow 14 with respect to the optical head 1 including the optical components such as the semiconductor laser 2 described above can be detected, and as described above, the position of the condenser lens 7 in the tracking direction indicated by the arrow 14 can be detected. The focusing lens 7 can be positioned at the center of the movable range by the tracking actuator 12, and the focusing lens 7 can be fixed at a fixed position within the optical head 1 during tracking access, and the focusing lens 7 can be fixed at a fixed position within the optical head 1 at the time of tracking access. 7 vibration can be suppressed.

As explained above, according to this configuration, the condenser lens 7, the % wave plate 6, and the mirror 22 are simultaneously moved in the tracking direction, and the reflected light from the wavelength plate 6 is detected by the two-split optical sensor 18. , the optical head 1 of the condenser lens 7
The two-split optical sensor 18 is used for this detection.
There is no need to add any extra optical elements other than that. Furthermore, compared to the first embodiment, the number of parts can be reduced while maintaining the same overall function.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a first embodiment of the optical head according to the present invention, and FIGS. 2(a) and 2(b) are enlarged views of the tracking movable part and two-split optical sensor in FIG. FIG. 3 is a block diagram showing a second embodiment of the optical head according to the present invention. In Fig. 1, 2, ■... to optics, 2... semiconductor laser, 3... collimating lens, 4... tracking movable part, 5... polarizing beam splitter, 6...
% Wave plate, 7... Condenser lens, 8.23... Reflective surface, 9... Nof mirror, 10... Convex lens, 11
...Knife etching, 12-...Tracking actuator, 13...Focus control actuator, 16-...
・・Original spot, 17・Recording medium, is, 19.20
...Two-split optical sensor, 21... Beam split 'J y
22...mirrors are shown respectively. Sacrifice 1 Leap figure 2 Trout 3 figure

Claims (2)

[Claims] (1) In an optical head that records or reads information by condensing light emitted from a semiconductor laser onto the surface of a recording medium using a condensing lens, the light emitted from the semiconductor laser travels approximately parallel to the surface of the recording medium. a beam splitter that transmits a portion of the incident light in a straight direction substantially equal to the direction of the incident light and reflects the part in a second direction different from the direction of the incident light; a mirror that reflects light in a perpendicular direction; a condensing lens that focuses the light reflected by the mirror onto a minute spot on the recording medium surface; and a two-split mirror that receives the light reflected in the second direction. an optical sensor, the beam splitter, the mirror, and the condensing lens are driven in the same direction as the incident light, and the two-split optical sensor drives the optical head in the same direction as the incident light of the condensing lens. To optics characterized by detecting the position of. (2) An optical system that records or reads information by condensing light emitted from a semiconductor laser onto the surface of a recording medium using a condensing lens (here, the light travels approximately parallel to the surface of the recording medium). 21. In this installation state, the light is carefully installed so that the incident light from the body is partially reflected in the direction of M2, which is different from the direction of the incident light, at the incident surface. A functioning long wavelength plate, a mirror that transmits the light transmitted through the temporary long plate in a perpendicular direction (in the opposite direction), and a mirror that directs the light reflected by the mirror to the recording medium surface. It has a condensing lens that condenses light onto a minute spot, and a two-split optical sensor that receives the second light reflected in one direction, and includes the wavelength plate, the mirror, and the condensing lens. An optical head characterized in that human incident light is driven in one direction, and the two-split optical sensor l collectively detects a position of the condenser lens in the same direction as the 4t1 iij'+ incident light with respect to the optical head.