JPH01235036A - Optical pickup device - Google Patents

Abstract

PURPOSE:To eliminate the optical limitation and to increase a range of accesses in the viewfield of an objective lens with shift of this lens by setting a polarizing means in a radiating optical path covering a laser light source through the objective lens and also in a return optical path covering the objective lens through a photodetector and moving the beams sent from the laser light source in parallel according to the shift of the objective lens. CONSTITUTION:A polarizer 30 contains a glass block 31 having its both sides set in parallel with each other and a coil 32 and is set between an objective lens 15 of an optical pickup 10A and a 1/4 wavelength plate 14. The coil 32 is wound round the block 31 of the polarizer 30 and then set into the magnetic field of a permanent magnet 34 with a shaft 33 kept in parallel. A deflecting current is supplied to the coil 32 form a displacement/rotational angle converter 48. Then the light beams sent from a laser light source 11 are moved in parallel and by an equal extent in accordance with the shift of the lens 15. As a result, a range of accesses is increased in the viewfield of the lens 15.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to optical pink-up devices.

[Summary of the invention]

The present invention provides an optical pickup device in which an optical deflection means is provided in the overlapping portion of the output optical path and the return optical path, and the optical beam from the laser light source is moved in parallel according to the movement of the objective lens, thereby widening the range of access within the field of view. It is designed to expand.

[Conventional technology]

In a well-known optical audio disc, a so-called compact disc, digital audio signals are recorded as a series of recesses called bits on the surface of a substrate made of, for example, polycarbonate.

Aluminum is deposited over the entire surface of the disk to form a reflective film. The depth of focus is set to 174 wavelengths of the laser beam used to read the signal, and due to the diffraction phenomenon of the laser beam, the recorded information is effectively read as a change in the intensity of the reflected light.

The optical pink-up 001 for reading uses a laser diode 01 as a light source, for example, as shown in FIG.
1 and a photodetector Qω that detects reflected light from the disk +11. The laser light emitted from the diode Oυ is formed into a parallel light beam (light beam) by a collimating lens, and is formed into a parallel light beam (light beam) by the deflection beam splitter 03. The light passes through a quarter-wave plate Oa and an objective lens θ, and is focused onto the disk (1).

This objective lens α is mounted on a two-axis device 0[0, and is arranged in two directions parallel and perpendicular to the optical axis, that is, the disk +1
1 and in the radial direction of the disk +11. For this movement, the two-wheeled device Q61 has a focus coil (17f) and a tracking coil (17t).

The return light from the disk (1) is transmitted through objective lenses α and 1.
74 wavelength plate 04], enters the polarizing beam splitter α, is reflected by its slope (+3r), and reaches the photodetector node via the lens 0 and the cylindrical lens Qgl.

As shown in FIG. 6, this photodetector (2m) has light receiving areas (20A) to (20D) divided into four parts in a square shape.

During reproduction of the disc (1), the focus error signal Sf and tracking error signal St formed from each detection output Sa - Sd of the photodetector (2) are sent to the coils (17f) and (17t) of the two-axis device. Servo control such as focusing and tracking is performed so that the spot of laser light from the pickup 0ω is always focused on the trunk.

(Problem to be Solved by the Invention) By the way, when the above-mentioned optical pink-up scream attempts to access a desired track of disk i11,
Depending on the distance between this desired track and the currently accessed trunk, the optical binoqua 710ω moves as follows.

First, the entire optical pickup O[9 is roughly moved (moved) to the vicinity of a desired track by a near motor or the like (not shown).

Next, the two-axis device QG performs a multi-track jump in which only the objective lens QSI moves over a range of several tens to hundreds of tracks.

Furthermore, objective lens a! several trunks to the desired track! Only 9 performs single track jumps, moving one tree at a time.

In addition, whether the entire optical pickup 0ω or only one objective lens is moved as described above, a system control device (not shown) controls fine and coarse movements based on the seven dresses of each track within the movement range. Mode switching and movement amount control are performed.

However, as mentioned above, the optical pickup αω has a complicated configuration and is large in shape and weight, so it takes a lot of time to move the entire device, which poses the problem of slow access to the desired trunk. there were.

In order to solve this problem, it is possible to expand the range of access within the field of view by moving the objective lens QSI, but in conventional optical pickups, the range of movement of the objective lens is optically restricted, and the field of view is There was a problem in that it was difficult to expand the access range within the network.

That is, when the objective lens 051 moves to the right from the neutral position shown by the solid line in FIG. 5 as shown by the broken line in the same figure,
The optical path of the return beam from the disk (1) is the objective lens 0.
5) is shifted by the amount moved, and after being reflected on the slope (13r) of the deflection beam splitter q1, the spot on the photodetector (2Ql) moves downward, as shown in Figure 6, and the servo It affects the error signal.

In addition, since the aperture of the objective lens 09 is selected to be, for example, 5 mm, and the diameter of the light beam is slightly larger than this, for example, about 6 m1, if the objective lens haze moves further to the right in FIG. A part of the lens QSI comes out of the light beam, reducing the amount of light focused on the disk (1) and causing aberrations due to "vignetting", resulting in an S/ of the detection output of the photodetector 112IfI. N and phase characteristics deteriorate. For this reason, the objective lens! ! Mechanically, the movable range of 9 exceeds, for example, ±las, but optically it is limited to about 10-odd 100 μm.

Increasing the diameter of the light beam will solve the above-mentioned problems such as reduced visibility for read-only optical discs, but for write-once and rewritable discs, a laser beam with low energy is required. In the case of optical discs, the problem arises that the coupling efficiency decreases, making it impractical.

In view of this, an object of the present invention is to provide an optical pickup device that eliminates optical constraints and expands the range of access within the field of view by moving the objective lens.

[Failure to solve the problem]

The present invention provides a laser light source αυ and two parallel and perpendicular to the optical axis.
an objective lens a9 that is supported movably in a direction and focuses a light beam emitted from a laser light source onto an optical recording medium (li); and a photodetector that receives return light from the optical recording medium through this objective lens. In an optical pink-up apparatus (IOA) comprising a laser light source, a light deflection means (30) is provided in the exit light path from the laser light source to the objective lens and in the return light path from the objective lens to the photodetector. This is an optical pink-up device that moves the light beam from the mirror in parallel according to the movement of the objective lens.

[Effect]

According to this configuration, the light beam from the laser light source follows the movement of the objective lens and moves in parallel by an equal amount, thereby expanding the range of access within the field of view.

〔Example〕

Hereinafter, an embodiment of an optical pickup device according to the present invention will be described with reference to FIGS. 1 to 3.

FIG. 1 shows the configuration of an embodiment of the present invention. In FIG. 1, parts corresponding to those in FIG. 4 are given the same reference numerals and redundant explanation will be omitted.

In FIG. 1, (30) is an optical deflector, which is equipped with a glass block (3I) and a coil (32) with parallel surfaces, and is equipped with an objective lens (151 and 174 of a wavelength plate 041) of an optical pickup (10^). As shown in Fig. 2, the glass block (31) of the optical deflector (30) has a coil (32) wound around it, and the axis (33) is set horizontally. , are arranged in the magnetic field of the permanent magnet (34).

The coil (32) is equipped with a displacement/rotation angle converter (48), which will be described later.
Deflection current is supplied from Optical pink up (IOA)
) The rest of the structure is the same as that shown in FIG. 4 above.

(41) is a matrix circuit, which includes a photodetector (2I1
Detection output S of each light receiving area (2OA) to (20D) of 1
a = Sd is supplied, and calculations as shown in the following equations (11 to (3)) are performed to obtain a high frequency signal sh, a focus error signal Sf, and a tracking error signal St.

Sh = Sa + Sb + Sc + Sd
mouth) Sf= (Sa+Sc) −(
Sb+Sd) (21St= (Sa+Sb) −
(Sc+Sd) (31) The high frequency signal sh is supplied to the signal processing circuit (42), where it undergoes processing such as demodulation and DA conversion, and reproduces the audio signal SAF.

The focus error signal Sf is supplied to the coil (17f) of the two-axis device via the servo amplifier (23).

The tracking error signal St is generated by a switch (45) which is switched in the opposite direction to that shown in the figure during reproduction, and a servo amplifier (44).
and is supplied to the coil (17t).

Reference numeral 46 denotes a jump pulse generator, which is controlled by the aforementioned system control device (not shown) and outputs a jump pulse Pj of an appropriate pulse width in accordance with the number of tracks to be jumped to. This pulse Pj is the switch (4
5) and a servo amplifier (44), it is supplied to the coil (17t) of the two-axis device OQ, and is also supplied to a displacement/rotation angle converter (hereinafter referred to as an X-θ converter) via a switch (47). (48).

Next, referring also to FIG. 3, the intra-field-of-view access operation of this embodiment will be described.

In the jump mode, switches (45) and (47) are switched to the illustrated state in conjunction with each other, and the tracking servo is rendered inactive. A jump pulse Pj from the pulse generator (46) is supplied to the coil (17t) of the two-axis device a61 via the amplifier (44), and the objective lens 09 is displaced, for example, to the right as shown.

At the same time, the jump pulse Pj from the amplifier (44)
-θ converter (48) and ×-θ converter (48)
A deflection current from is supplied to the coil (32) of the optical deflector (30), and the glass block (31) is rotated, for example, clockwise.

As shown in Figure 3, the glass block (31
) is incident from below on the lower surface (31
1) and the upper surface (31u), the light beam is refracted twice, moves parallel to the rotating direction, and is emitted upward.

If the refractive index of the glass block (31) is n, the thickness is L, and the rotation angle is θ, then the incident angle is θ, and the refraction angle is φ, and the parallel shift of the exiting ray with respect to the incident ray tJ]ff1X is as follows. It is expressed as equation (4) below.

X = t (tanθ-tanφ) cosθCOSφ According to Snell's law, between the incident angle θ and the refraction angle φ,
The following equation (5) holds true.

sinθ=nsinφ (5)+4
1. By eliminating φ from both f51 equations, the following equation (6) is obtained.

The conversion characteristic expressed by this equation (6) is
O! If the amount of parallel movement of the emitted light by the optical deflector (30) is made equal to the amount of displacement of the objective lens 051, the above-mentioned optical constraints are removed and the objective lens QSI is The range of access within the visual field by movement is expanded.

For example, a glass block with a refractive index of n=1.51 (31
) is rotated by ±30° or ±45°, the movable range of the objective lens α9 is expressed by the following equations (7a) and (7b), respectively.

[±X) zo-±0.19t (7a) [±x)
,, #±0.33t (7b) Glass block (
31) is, for example, 15n, the total movement range according to equation (7b) reaches 9.9711, which is smaller than the conventional large number 100.
Compared to μm, it is significantly enlarged.

In the above embodiment, for the sake of simplicity, an integrated optical pickup device was described which is suitable for playing digital audio discs, but it can be modified as appropriate and is also suitable for recordable and rewritable optical discs. The present invention can be similarly applied to optical pickup devices.

Furthermore, by supplying the optical deflector (30) according to the present invention with a DC fluctuation component of a push-pull type tracking error signal caused by the eccentricity of the disk or the inclination (skew) of the optical axis of the pickup, it is possible to reduce the skew. It is also possible to create an optical pickup device that is resistant to eccentricity and eccentricity.

〔Effect of the invention〕

As described in detail above, according to the present invention, a light deflecting means is provided in the overlapping portion of the output optical path and the return optical path, and the light beam from the laser light source is moved in parallel according to the movement of the objective lens. , an optical pickup device with an expanded range of in-field access can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of an optical pickup device according to the present invention, FIG. 2 is a perspective view showing the configuration of essential parts of an embodiment of the present invention, and FIG. FIG. 4 is a cross-sectional view showing a configuration example of a conventional optical pickup device, and FIGS. 5 and 6 are a cross-sectional view and a front view for explaining the present invention. (1) is an optical recording medium, 001. (], OA) is an optical pickup, 00 is a laser diode, 09 is an objective lens, 0ω is a two-axis device, QllD is a photodetector, (3
0) is an optical deflector, (46) is a jump pulse generator, (
4) is a displacement/rotation angle converter.

Claims (1)

[Scope of Claims] A laser light source, an objective lens that is supported movably in two directions parallel and perpendicular to the optical axis and that focuses a light beam emitted from the laser light source onto an optical recording medium, and this objective lens. an optical pickup device comprising a photodetector that receives return light from the optical recording medium via a lens, in an emission optical path from the laser light source to the objective lens and from the objective lens to the photodetector An optical pickup device, characterized in that a light deflecting means is provided in the return optical path of the laser light source, and the light beam from the laser light source is moved in parallel according to the movement of the objective lens.