JPH0614259Y2 - Optical pickup device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to an optical pickup device used in a device or the like for optically recording and reproducing information by irradiating a disc-shaped recording medium with a light spot.

<Prior Art> As an optical pickup device of this type, the entire optical system is housed in a single housing, and the housing is integrally driven with respect to the recording medium to retrieve information on the recording medium. The form of doing is common.

However, such a device causes a problem that the weight of the housing becomes large, which becomes a cause of hindering the reduction of information retrieval time. Therefore, as shown in FIG. 2, an optical pickup device has been used in which the optical system is divided into a driving portion and a non-driving portion, and the driving portion is lightened.

In the figure, reference numeral 1 denotes a first housing which accommodates a semiconductor laser light source 2, a collimator lens 3, a beam splitter 4 and a first optical system in which the objective lens 5 is arranged in a row, and which faces the objective lens 5. Laser light emission ports 1a and 1b are formed on the upper surface and the side surface facing the beam splitter 4, respectively. The first housing 1 is provided in a cabinet (not shown), and is parallel to a disk-shaped recording medium 10 arranged close to the upper surface while maintaining a constant space therebetween by a driving means (not shown). Arrow
It is designed to be driven in the A and B directions. Reference numeral 9 denotes a second housing fixedly provided in the same cabinet as the first housing 1, and an entrance 9a is formed on the side surface of the first housing 1 facing the exit 1b. The second optical system in which the converging lens 6, the cylindrical lens 7, and the photodetector 8 are arranged in a line is housed.

The laser light from the semiconductor laser light source 2 is collimated by the collimator lens 3 and then radiated as a light spot on the disc-shaped recording medium 10 by the objective lens 5 via the beam splitter 4 to be emitted on the disc-shaped recording medium 10. The reflected light reflected is collimated by the objective lens 5 and then reflected by the beam splitter 4 at right angles to the direction of the emission port 1b, and is incident on the incidence port 9a of the second casing 9 in the state of parallel light. Then, it passes through the converging lens 6 and the cylindrical lens 7 and is irradiated as a light spot on the photodetection element 8, and the information signal and the error signal are detected by the photodetection element 8.

<Problems to be Solved by the Invention> In the conventional device shown in FIG. 2, only the reflected light 11 reflected at a right angle by the beam splitter 4 is incident on the second housing 9 through its entrance 9a. In this case, there is no problem, but as shown in the figure, light other than the reflected light 11, such as stray light 1 from the outside of the insertion
When 1 ′ enters the second housing 9 through the entrance 9a and the photodetector 8 detects it, the S / N ratio of the reflected light 11 as an information signal and an error signal decreases. There was a problem.

The present invention has been made in view of these problems, and was made for the purpose of preventing unnecessary light from entering the second housing and preventing a decrease in S / N ratio.

<Means for Solving the Problems> In order to achieve the above-mentioned object, in the optical pickup device of the present invention, other than the wavelength of the laser light from the laser light source is provided in front of the photodetection element in the second housing. An optical filter that blocks light having a wavelength of is provided.

<Operation> Since light other than the reflected light from the first housing is blocked by the optical filter, even if stray light enters the second housing, it does not reach the photodetector. Moreover, the S / N ratio does not decrease due to stray light.

<Example> Next, an example shown in FIG. 1 will be described. The second
The same parts as those in the figure are shown by the same reference numerals, and only different parts will be described.

In the figure, 21 is a second corresponding to the second housing 9 in FIG.
The cabinet is fixedly provided in a cabinet (not shown). An entrance 21a is formed in the side surface of the second housing 21 facing the exit 1b of the first housing 1, a filter 12 is attached to the entrance 21a, and a converging lens 6 is provided inside. A second optical system is configured by arranging the cylindrical lens 7 and the light detection element 8 in a line. Filter 12 above
Has a characteristic that blocks light other than the laser light from the laser light source 2, and the wavelength of the semiconductor laser light is 780 nm ± 1.
Since it is 5 nm, for example, an interference filter or a colored glass filter that absorbs light other than this wavelength is used.
The filter 12 is not limited to one, and may be a combination of a plurality of filters. The place where the filter 12 is installed is not limited to the illustrated place, as long as it is a position in front of the photodetector 8 that can prevent unnecessary light from entering the photodetector 8.

This embodiment is configured as described above, and when detecting information recorded on the disc-shaped recording medium 10, the disc-shaped recording medium 10 is irradiated with laser light from the emission opening 1a of the first housing 1. However, the first housing 1 may be driven in the direction of arrow A or B, and the reflected light reflected by the disk-shaped recording medium 10 is emitted from the emission port 1b as in the case of FIG. Then, the light enters from the entrance 21a of the second housing 21, and the filter 1
2, the photodetector 8 through the converging lens 6 and the cylindrical lens 7.
An optical signal is formed on the disc-shaped recording medium 10, and an information signal and an error signal are detected.

At this time, in addition to the reflected light 11, stray light 11 ′ from the outside of the device or the like may reach the entrance 21a, but the stray light 11 ′ is generally not the laser light emitted by the semiconductor laser light source 2. Due to the different wavelengths, these stray light 11 'are filtered
All are removed by 12 and the original reflected light is detected by the photodetector element 8.
Only 11 is incident, and the information signal and the error signal are detected with a good S / N ratio.

<Effect of Device> As is apparent from the above-described embodiments, the optical pickup device of the present invention has a wavelength other than the wavelength of the laser light from the laser light source in front of the photodetector element in the second housing. An optical filter that blocks light is provided.

Therefore, the influence of stray light, which is likely to occur when the optical system is divided into the first casing that is the driving portion and the second casing that is the non-driving portion, is extremely effectively removed, and the driving weight is reduced. It is possible to easily prevent a decrease in the S / N ratio due to unnecessary light in the optical pickup device including the portion.

[Brief description of drawings]

FIG. 1 is a schematic side sectional view of an embodiment of the present invention, and FIG. 2 is a schematic side sectional view of a conventional example. 1 ... 1st case, 1a, 1b ... Emitting opening 2 ... Semiconductor laser light source, 8 ... Photodetector 10 ... Disc-shaped recording medium, 11 ... Reflected light 11 '... Stray light, 12 ... … Filter 21 …… Second housing, 21a …… Inlet

Claims (1)

[Scope of utility model registration request] 1. An optical system which is movably provided with respect to a recording medium and has an optical system for irradiating a laser beam from a laser light source onto the recording medium and for guiding the reflected light out of the case. In an optical pickup device including a first housing and a second housing having an optical system that guides the reflected light from the first housing to a photodetection element, the light detection in the second housing is performed. An optical pickup device characterized in that an optical filter for blocking light having a wavelength other than the wavelength of laser light from a laser light source is provided in front of the element.