JPS62264438A - Optical pickup device - Google Patents

Abstract

PURPOSE:To miniaturize a device, to thin in type, and to lighten in weight, by detecting dislocation between the optical axis of an objective lens, and that of a laser beam of light from a semiconductor laser by detecting a beam of light position from a deflecting element made incident on a position detecting photodetector by the said photodetector. CONSTITUTION:The outputs divided into two of photoreceiving parts A' and B are inputted to a subtractor 22, and an output difference (Pb-Pa) can be found. A position detecting photodetector 16 is mounted at a focusing moving body 14, and a deflecting element 20 has a width enough to project the spot of a laser beam possible to detect. When the optical axis of an objective lens 12, and that of the laser beam of light coincide, it goes to (Pb-Pa)=0. and when a lens holder 11 is moved in a tracking direction with the objective lens 12, the difference of the output signals of those photoreceiving parts A and B goes to Pb-Pa>0, or Pb-Pa<0. Thus, it is possible to detect the dislocation between the optical axis of the objective lens 12, and that of the laser beam of light from the value of the difference (Pb-Pa) of the output signals. In such a way, it is possible to make the device into the miniaturization, the thin type, and the lightening.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an optical big amplifier device, and more particularly to a position sensor that detects an optical axis misalignment between an objective lens and a laser beam from a semiconductor laser in an optical pinoch amplifier device. .

(Prior Art) In an optical pick amplifier device that records information signals on the recording medium and reads out the information signals by focusing laser light emitted from a semiconductor laser onto the surface of the recording medium using an objective lens, tracking is performed. The operation causes optical axis misalignment between the objective lens and the laser beam, reducing tracking detection accuracy. Therefore, in conventional general optical pickup devices, a position sensor is used to detect the movement of the objective lens in the tracking direction, and the entire optical pickup device is moved in the tracking direction by following the detected movement of the objective lens in the tracking direction. By moving it, the optical axis misalignment between the objective lens and the laser beam is minimized.

FIG. 5 shows a general example of a position sensor in a conventionally used optical pickup device.

In FIG. 5, an objective lens 2 focuses and irradiates laser light from a semiconductor laser (not shown) onto the surface of a recording medium, and is held by a lens holder 1.

The lens holder 1 is supported on a focusing moving body (not shown) via a pair of tracking leaf springs 3.3, and is driven in the direction shown by the arrow by a tracking drive device consisting of a magnet and a driving coil (not shown).
Tracking operation is now performed. An aperture 4 is bored in the side surface of the lens holder 1 in a direction perpendicular to the tracking direction. A light emitting element 5 made of an LED or the like and a PS are sandwiched between the lens holder 1 from both sides.
A position detection light receiving element 6 made of D or the like is arranged. The light emitting element 5 and the position detection light receiving element 6 are integrally provided on the focusing moving body, and the emission center axis of the light emitting element 5 and the light reception center axis of the position detection light receiving element 6 are the optical axis of the laser beam from the semiconductor laser. and coincides with the central axis of the aperture 4 at the tracking center position.

According to the above conventional example, when the objective lens 2 moves in the tracking direction together with the holder 1 due to the tracking operation,
The position of the light spot from the light emitting element 5 that is irradiated onto the position detection light receiving element 6 through the aperture 4 moves, and the output signal of the position detection light receiving element 6 changes. The deviation of the laser beam from the optical axis can be detected.

However, according to the above-mentioned conventional example, it is necessary to provide a light emitting element for a position sensor in addition to the semiconductor laser in the optical pick amplifier device, which is a factor that hinders the miniaturization, thinning, and weight reduction of the optical pick amplifier device. It had become.

(Purpose) The present invention has been made to solve the above-mentioned conventional problems, and aims to achieve miniaturization, thinning, and weight reduction by eliminating the need for a special light emitting element for a position sensor. The purpose of the present invention is to provide an optical pickup device that is capable of

(Structure) The present invention provides a deflection element that deflects a part of a laser beam from a semiconductor laser in a holder that holds an objective lens, and a position detection light receiving element is provided outside the holder to allow the deflection element to deflect a part of the laser beam from the semiconductor laser. Disposed in the deflection optical path, the position detection light receiving element detects the position of the light beam from the deflection element that enters the element, thereby detecting a deviation between the optical axis of the objective lens and the optical axis of the laser beam from the semiconductor laser. It is characterized by

Embodiments of the optical pickup device according to the present invention will be described below with reference to the drawings.

In FIGS. 1 and 2, the laser beam emitted from the semiconductor laser indicated by the reference numeral 17 is transmitted through the collimator lens 1.
8 into a parallel beam of light, and the beam splitter 19 and λ
/4 plate 1 metal plate 5 leads to the objective lens 12. The objective lens 12 focuses and irradiates the laser beam onto the recording surface of a recording medium (not shown). The reflected light from the recording medium passes through the objective lens 12, the λ/4 plate 1, the metal plate 5,
It is reflected laterally by the beam splitter 19 and reaches a detection element (not shown), and as is well known, a focusing signal,
Tracking signals and information signals can be obtained.

The objective lens 12 is held by a lens holder 11, and a deflection element 20 made of a total reflection mirror is obliquely provided at an inner portion of the lens holder 11. As shown in FIG. 2, the lens holder 11 is supported by the focusing moving body 14 via a pair of elastic supports 13.13.

Here, as shown in FIG. 3, if the cross section of the laser beam is a circular range a, and the effective diameter of the objective lens 12 is a shaded circular range, then the deflection element 20 is placed outside the effective beam range of the laser beam,
The optical path of the laser beam necessary for detecting information signals etc. is not obstructed. The light beam deflected by the deflection element 20 passes through two apertures formed on the side of the lens holder 11 and exits the holder 11 to the outside of the holder 11, and passes through the position detection light receiving element 16 arranged in the optical path deflected by the deflection element 20.
It is designed to be incident on . The aperture 21 is circular so that the beam deflected by the deflection element 20 is shaped into a circle and guided to the position detection light receiving element 16.

The position detection light-receiving element 16 is a PSD or the like, and as shown in FIG. The difference Pb-Pa is determined and output.

The position detection light receiving element 16 is attached to the focusing moving body 14 as shown in FIG. The deflection element 20 has a width sufficient to irradiate the position detection light receiving element 16 with a detectable laser beam spot.

Now, assuming that the optical axis of the objective lens 12 and the optical axis of the laser beam coincide, a part of the laser beam deflected by the deflection element 20 passes through the aperture 21 to the position detection light reception shown in FIG. Since the light is equally incident on the light receiving sections A and B of the element 16, which are divided into two, the difference between the output signals of these light receiving sections A and B is Pb-Pa=0. Next, along with the tracking operation, the objective lens 1
2, the lens holder 1 moves in the tracking direction shown by the arrow in FIG. 2, the effective diameter of the objective lens 12 shifts relative to the cross section a of the laser beam as shown by C. As the lens holder 1 moves in the tracking direction, the deflection element 20 also moves integrally in the tracking direction, and the deflection surface (reflection surface) of the deflection element 20
is also shifted relative to the cross section a of the laser beam. Therefore,
The balance of the luminous flux incident on the two divided light receiving parts A and B of the position detection light receiving element 16 via the aperture 21 is disrupted, and the difference between the output signals of these light receiving parts A and H is Pb-Pa>0 or Pb-Pa <0. In this way, the deviation between the optical axis of the objective lens 12 and the optical axis of the laser beam can be detected from the difference Pb-Pa0 value of the output signals, so the entire optical pickup device is adjusted so that the difference between the output signals becomes O. By moving it, the optical axis of the objective lens and the optical axis of the laser beam can be made to coincide.

As described above, according to the above embodiment, a part of the laser beam from the semiconductor laser is deflected by the deflection element provided in the lens holder, and the objective is deflected by utilizing the fact that this deflected light moves in the tracking direction during the tracking operation. Since the lens optical axis position is detected, there is no need to provide a special light-emitting element for position detection, and an optical pickup device that can be made smaller, thinner, and lighter can be obtained.

In the embodiment shown in FIG. 4, the deflection element 40 used to detect the optical axis position of the objective lens 32 is a half mirror and is provided on the lens holder 31. The deflection element 40 is provided obliquely over the entire range of the cross section of the laser beam from the semiconductor laser 37, and transmits a part of the laser beam to the objective lens 32 side, and transmits the other part of the laser beam to the position detection light receiving element 36. 38 is a collimator lens, 39 is a beam splitter, 35 is a λ/4 plate, and 41 is a lens holder 31 for guiding the light beam deflected by the deflection element 40 to the position detection light receiving element 36. It is a circular aperture formed in.

In the case of the embodiment shown in FIG. 4 as well, as the lens holder 31 and deflection element 40 move together with the objective lens 32 in the tracking direction, the beam pond moves on the position detection light receiving element 36. This can be detected by the output of the element, and thereby the deviation between the optical axis of the objective lens 32 and the optical axis of the laser beam from the semiconductor laser 37 can be detected. Also in this embodiment, since there is no need to provide a special light emitting element for detecting the optical axis position of the objective lens, it is possible to obtain an optical pink amplifier device that is smaller, thinner, and lighter.

(Effects) According to the present invention, a part of the laser beam from the semiconductor laser is deflected by the deflection element provided on the lens holder,
Since the objective lens optical axis position is detected by utilizing the movement of this deflected light in the tracking direction during tracking operation, there is no need to provide a special light emitting element for position detection (therefore, miniaturization is possible. Therefore, it is possible to obtain an optical pickup device that can be made thinner and lighter.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of an optical pickup device according to the present invention, FIG. 2 is a perspective view of an objective lens and its holder in the same embodiment, and FIG. 3 is a position according to the above embodiment. An explanatory diagram showing the principle of the detection operation, FIG. 4 is a longitudinal sectional view showing another embodiment of the optical pickup device according to the present invention,
FIG. 5 is a perspective view of essential parts of an example of a conventional optical pickup device. 11.31...Holder, 12.32...Objective lens,
16.36... Position detection light receiving element, 17.37... Semiconductor laser, 20.40... Deflection element, 21.41
...Aperture. (1 other person) ″″″″ ■δ 口

Claims (1)

[Claims] 1. An optical pickup device that records and reads out information signals on the recording medium by focusing and irradiating laser light emitted from a semiconductor laser onto the surface of the recording medium using an objective lens. In this method, a deflection element for deflecting a part of a laser beam from a semiconductor laser is provided in a holder that holds an objective lens, and a position detection light receiving element is provided outside the holder and placed in the optical path deflected by the deflection element. , characterized in that a deviation between the optical axis of the objective lens and the optical axis of the laser beam from the semiconductor laser is detected by detecting the position of the beam from the deflection element that is incident on the position detection light receiving element. Optical pickup device. 2. The optical pickup device according to claim 1, wherein the deflection element is a mirror that guides a part of the cross section of the laser beam from the semiconductor laser to the position detection light receiving element. 3. The deflection element is a half mirror that transmits a part of the laser beam from the semiconductor laser to the objective lens side and guides the other part of the laser beam to the position detection light receiving element. Optical pickup device. 4. The optical pickup device according to claim 1, wherein an aperture for making the deflected light beam circular is provided in the optical path deflected by the deflection element, and the aperture is provided in the holder of the objective lens.