JPH05298719A - Optical disc reader - Google Patents

Abstract

PURPOSE:To provide an optical disc reader having simple constitution and can be downsized easily. CONSTITUTION:The optical disc reader comprises a hologram element 3 splitting light flux from the optical disc reader for every cross-sectional area, and am opto-electric converting element 9 for irradiating one of a plurality of divided light receiving areas with at least two split light fluxes introduced through the hologram element 3. Reflected light from a disc is split through the hologram element 3 into a plurality of lights and a plurality of light spots (a)-(f) formed thereby are introduced to a plurality of divided light receiving areas J-M of the opto-electric converting element 9. Outputs from the light receiving areas J-M are then compared and a focus error detection signal or a track error detection signal is produced thus reducing conventionally required interconnection between the light receiving areas J-M.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk reading device which outputs an error detection signal by guiding a large number of light spots formed by a hologram element from a laser beam to a plurality of photoelectric conversion elements. ..

[0002]

2. Description of the Related Art FIGS. 3 and 4 show a conventional optical disk reader having a hologram element. The light flux of the laser light emitted from the laser light source 1 is guided to the objective lens 5 via the hologram element 3 and is condensed on the disk 7. The reflected light from the disk 7 is guided to the hologram element 3 via the objective lens 5.

The hologram element 3 (FIG. 4 (a)) is divided into six reflection areas a to f. As shown in FIG. 4 (b), a light beam is d Divide into 6 to f. 6 created by being divided into 6
The divided light beams a to f are guided to the six light receiving regions a ′ to f ′ of the photoelectric conversion element 9, respectively. Then, the focus error detection signal FE is FE = (a '+ d')-(b 'by generating astigmatism in the hologram element 3.
+ C ') is detected.

In the track error detection signal TE, right and left light fluxes in the pit row direction XX 'on the disk 7 are
By being guided to the light receiving regions e ′ and f ′ of the photoelectric conversion element 9, TE = (e ′) − (f ′) is detected. It should be noted that a'to f'in the equations represent outputs from the light receiving regions a'to f '. In another conventional example, the luminous flux is divided into eight and guided to eight light receiving regions of the photoelectric conversion element.

[0005]

However, in such a conventional technique, a large number of divided luminous fluxes formed by dividing the luminous flux are guided to one light receiving region of the photoelectric conversion element, so that the photoelectric conversion element is provided. Must have independent light-receiving regions for the number of divided light beams formed by division, and thus miniaturization is difficult. Further, there is a drawback in that a large number of wirings are connected to combine outputs from a large number of light receiving regions, resulting in a complicated structure.

The object of the present invention is to remedy these drawbacks,
An object of the present invention is to provide an optical disc reading device having a simple structure and easily downsized.

[0007]

In order to achieve the above object, the present invention provides a hologram element that divides a light beam from an optical disk reading device for each cross sectional area and a divided light beam that is guided by the hologram element. Also includes a photoelectric conversion element in which two divided light beams are irradiated to one light receiving region among the plurality of light receiving regions.

Further, at least two split luminous fluxes applied to one light receiving region of the photoelectric conversion element may be overlapped.

[0009]

Since a plurality of light receiving areas which have been conventionally combined by wiring are used as one light receiving area and at least two divided light beams from the hologram element can be guided to the one light receiving area, the number of light receiving areas can be reduced. The number of wires can be reduced.

Further, by making the divided light beams applied to the light receiving region overlap, the area of the light receiving region can be reduced.

[0011]

1 shows a first embodiment of the present invention. That is, (a) shows the light receiving area of the hologram element 3. (B) is a figure which shows the light-receiving area of a photoelectric conversion element. The same parts as those in the conventional example (FIGS. 3 and 4) are designated by the same reference numerals.

The hologram element 3 is divided into six reflection areas a to f as in the conventional case (FIG. 4A). Due to the function of the hologram 3, six divided light fluxes a to f are created by the diffractive action for each cross-sectional area of the light flux corresponding to the reflection areas a to f. On the other hand, the photoelectric conversion element 9 is 4
It has two light receiving regions J, K, L and M. And the above 6
Two of the divided luminous fluxes a and d are in the light receiving region J.
It is guided to and irradiates. Similarly, the divided luminous fluxes c and b are in the light receiving region K.
It is guided to and irradiates. Further, one divided light flux e is guided to the light receiving area L, and one divided light flux f is guided to the light receiving area M to irradiate. In the figure, the divided luminous fluxes a, d or c, b are separately irradiated in the respective light receiving areas J, K, but in other embodiments, they may be irradiated in an overlapping manner. Good.

As a result, the focus error detection signal FE becomes FE = JK. In the equation, J and K represent outputs from the light receiving areas J and K, respectively. Similarly, the track error detection signal TE
Becomes TE = LM. In the equation, L and M similarly represent outputs from the light receiving regions L and M.

As described above, according to the present embodiment, there are six light receiving regions (a ', b',
c ', d', e ', f') are four light receiving regions J, K,
It becomes L and M, and the number of light receiving regions can be reduced. Further, unlike the conventional case, the wiring for gathering the light receiving regions is not required, and the number of wirings is reduced. Further, if the irradiation of the divided light beams is performed in a superposed state, the areas of the light receiving regions J and K can be reduced.

FIG. 2 shows another embodiment. As shown in FIG. 2, the hologram element 3 is divided into eight reflection regions (A to H in the figure), which allows the light flux to be divided into eight. At this time, the focus error signal is divided into the divided luminous fluxes A to H.
Output (A + C + E + G) and (B + D + F +)
It is generally known that the tracking error signal is formed by the phase difference between H) and the phase difference between (A + B + G + H) and (C + D + E + F). In the present embodiment, as shown in the figure, one light receiving region P in the photoelectric conversion element 9 is divided into two divided light beams A and G, similarly light receiving region Q is divided into light beams B and H, and light receiving region R is divided into light beams E and C. Since the divided light fluxes D and F are guided and irradiated to the light receiving area S, the focus error signal is obtained by comparing the phases of the outputs (P + R) and (Q + S) due to the irradiation of the light receiving areas P to Q by the respective divided light fluxes. The track error signal obtained is similarly obtained by comparing the phases of the outputs (P + Q) and (P + S).

Note that the separated light beams may overlap in each of the light receiving regions P to Q, as in the first embodiment.

Even when the luminous flux is divided into eight divided luminous fluxes in this manner, the number of light-receiving regions (which is conventionally eight, which is the same as the number of divided luminous fluxes) can be reduced (FIG. 2).
As shown in (b), P, Q, R and S are four), and accordingly, the wiring for collecting the light receiving regions is defective and the number of wirings is reduced.

[0018]

As is apparent from the above embodiments, the present invention can guide at least two divided light beams from the hologram element to one light receiving area of the photoelectric conversion element, so that the number of light receiving areas can be reduced. The number of wires can be reduced.
Further, the area of the light receiving region can be reduced by overlapping and guiding the two divided light beams. By thus reducing the number of light receiving regions, reducing the number of wirings, and reducing the area, the structure of the photoelectric conversion element can be simplified and downsized, and in turn, the entire device can be downsized.

[Brief description of drawings]

FIG. 1A is a diagram of a hologram element according to a first embodiment of an optical disc reading apparatus of the present invention, and FIG. 1B is a diagram of a photoelectric conversion element of the first embodiment.

2A is a diagram of a hologram element according to a second embodiment of the present invention, and FIG. 2B is a diagram of a photoelectric conversion element of the second embodiment.

FIG. 3 is a schematic diagram of a conventional optical disk reading device.

4A is a diagram of the hologram element of FIG. 3, and FIG. 4B is a diagram of the photoelectric conversion element of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 laser light source 3 hologram element 5 objective lens 7 disk 9 photoelectric conversion element a, b, c, d, e, f divided luminous flux a ', b', c ', d', e ', f' light receiving area J, K , L, M light receiving area A, B, C, D, E, F, G, H split light flux P, Q, R, S light receiving area

Claims (2)

[Claims] 1. A hologram element that divides a light beam from an optical disk reading device for each cross-sectional area, and at least two divided light beams among the divided light beams guided by the hologram element, among a plurality of light-receiving areas. An optical disk reading device comprising a photoelectric conversion element for irradiating one light receiving region. 2. The optical disk reading device according to claim 1, wherein at least two divided light beams applied to one light receiving region of the photoelectric conversion element overlap each other.