JP2788695B2 - Hologram laser unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram laser unit used as a light source for reading an optical disk such as a compact disk, and more particularly to a method for bonding and fixing hologram glass.

[0002]

2. Description of the Related Art A conventional hologram laser unit 1 comprises:
The one shown in FIG. 4 is known. This will be described below with reference to the drawings. The hologram element 2 is made of a single glass substrate. A hologram 3 is formed on the upper surface, and a tracking beam generating diffraction grating (hereinafter, referred to as a hologram pattern) 4 is formed on the lower surface.

In addition, a laser diode (hereinafter referred to as an LD) as a light source
5) and a photodiode for signal detection (hereinafter P
D) 6 are mounted on a common stem 7 and housed in one package 8.

[0004] hologram element 2 which is made from a glass substrate of one described above, as shown in FIG. 5, are fixed with an adhesive 9 to the top of the package 8. The adhesive 9 is applied to the entire circumference of the glass substrate.

[0005] A cap 10 is welded to the inside of the package 8, that is, a lower portion of the hologram element 2, with a low-melting glass 11 to hermetically seal the cap 10 and the package 8. As a result, a gap 12 is formed between the glass substrate 2 and the cap 10 by a thickness substantially equal to the thickness of the package 8.

[0006] holographic pickup 13 using the hologram unit 1 constructed as described above, has been known as shown in Figure 6. The optical system of the hologram pickup 13 will be described below. The light emitted from the LD 5 is divided into three light beams of two tracking sub-beams and an information signal reading main beam by the hologram pattern 4 formed on the back surface of the hologram element 2.

Then, the light passes through the hologram 3 on the upper surface as 0-order light, is converted into parallel light by the collimator lens 14, and is then focused on the disk 16 by the objective lens 15. The reflected light modulated by the pits on the disk 16 is diffracted by the hologram 3 after passing through the objective lens 15 and the collimator lens 14, and is guided as a first-order diffracted light onto a 5-division PD.

The hologram 3 is composed of two regions having different grating periods. The reflected light of the main beam is such that the light that has entered one region of the hologram 3 is on the dividing line of the photodetectors D ₂ and D ₃ and the other is those incident on the area is converged on the light detector D _4.

[0009] The reflected light of the sub-beam is focused on the photodetectors D ₁ and D ₅ , respectively. These focused beams
According to the convergence state on the disk, as shown in FIG. 7 , if the distance is too far (a), the focus will be changed (b), and if the distance is too close, it will change as (c).

[0010]

The hologram unit 1 constructed as described above is placed in, for example, a high temperature and high humidity state (65).
If left at (° C., 95% absolute humidity), moisture enters the gap 12 through the adhesive 9 that bonds the glass substrate. If left as it is, the inside of the gap 12 will be in the same state as the outside atmosphere at 65 ° C. and 95% absolute humidity.

From this state, the atmosphere is changed to, for example, 25.degree.
When the humidity is changed to the absolute humidity, the inside of the space 12 becomes a dew point before the moisture escapes outside through the adhesive 9 and adheres to the hologram pattern 4 in the form of water droplets. As a result, the pattern grooves are filled with water droplets.

As a result, the light does not bend at the normal diffraction efficiency, the modulated signal from the disk is weakened, and in the worst case, the signal cannot be read.

For this reason, in a device that attaches importance to environmental resistance, such as a compact disk player mounted on a vehicle, which is equipped with an optical pickup using the hologram unit 1 as described above, noise occurs during use or a regular sound is output. There was no problem.

In view of the above, the present invention provides a hologram laser unit having improved moisture resistance.

[0015]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides an optical disc in a semiconductor laser package.
Built-in light-receiving element that reads signals modulated by
Bending the laser light on the package to the light receiving element
Hologram glass and airtight inside the package
And a hologram glass,
A hologram having a gap formed with a cap glass.
In the ram laser unit, the hologram glass and
Cap glass is partially adhered and fixed with an adhesive.
The area without adhesive is used as an air passage,
And a hologram laser unit that communicates with the outside of the package .

[0016]

[Function] Since the gap formed between the hologram element and the cap glass communicates with the outside of the package, even if the surrounding environment changes, moisture accumulates in the gap and water drops adhere to the hologram element and the cap. I will not do it.

[0017]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a top view of a hologram laser unit according to the present invention, and FIG. The difference between the hologram laser unit 21 of the present invention and the conventional hologram laser unit 1 is that the gap between the hologram element 2 and the cap 10 is different from that of the adhesive. 9, the gap 12 in the hologram unit 21 of the present invention is in communication with the outside.

That is, the glass substrate of the conventional hologram element 2 is adhered all around the package 8, but the hologram element 2 of the present invention is different in that the hologram element 2 is adhered in place to the package 8.

Since the configuration is the same as that of the conventional hologram unit 1 except for the above-mentioned bonding method, detailed description is omitted. The same parts are denoted by the same reference numerals.
The hologram element 2 of the hologram laser unit 21 according to the present invention is configured such that the four corners of the glass substrate are
The gap 12 formed between the hologram element 1 and the cap glass 10 is communicated with the outside without being sealed by the adhesive 22.

The bonding method may be at two locations on a diagonal line as shown in FIG. 3 , and is not limited to the method described in the above embodiment.

Hologram laser unit 21 of the present invention
Is left in an atmosphere of, for example, 65 ° C. and 95% absolute humidity, the space 12 immediately becomes the same atmosphere. If the atmosphere is changed from that state to, for example, 25 ° C. and 50% absolute humidity, the moisture becomes moisture and adheres. I do. This moisture is in the gap 1
2, but the gap 12 is easily communicated with the outside because the gap 12 communicates with the outside. Therefore, moisture does not remain in the gap 12.

[0022]

Since the present invention is configured as described above, it has the following effects. Since the gap formed in the hologram laser unit is communicated with the outside, water drops do not adhere to the gap even if the gap is repeatedly left in an atmosphere of high temperature and high humidity and normal temperature and normal humidity.

Therefore, by using the hologram laser unit of the present invention in an optical pickup such as a compact disk player for a vehicle, which emphasizes environmental resistance, light is bent at a regular diffraction efficiency and converted into sound regardless of the surrounding atmosphere. Practicality that no abnormality occurs is improved.

[Brief description of the drawings]

FIG. 1 is a top view of one embodiment of a hologram laser unit of the present invention.

FIG. 2 is a sectional view of a main part of the hologram laser unit.

FIG. 3 is a top view of another embodiment of the hologram laser unit of the present invention.

FIG. 4 is a sectional view of a main part of a conventional hologram laser unit.

FIG. 5 is an enlarged sectional view of a main part of a conventional hologram laser unit.

FIG. 6 is an explanatory diagram illustrating a signal detection principle of a hologram pickup using a hologram laser unit.

FIGS. 7A and 7B are explanatory diagrams showing a change in a beam shape on a signal detecting photodiode due to a displacement of a disk, wherein FIG. 7A shows a case where the focus is too far, FIG.
(C) illustrates the case where the focus is too close.

[Explanation of symbols]

Reference Signs List 2 hologram element 2a glass substrate 3 hologram 4 diffraction grating (hologram pattern) for tracking beam generation 5 laser diode (LD) 6 photodiode for signal detection 7 stem 8 package 10 cap 12 gap 21 gap 21 hologram laser unit 22 adhesive

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G11B 7/125 G11B 7/135

Claims (1)

(57) [Claims] 1. A built-in light receiving elements for reading the signal being modulated by the optical disk in the semiconductor laser package, and the hologram glass for bending the laser beam to the light receiving element on the package, hermetically said package A cap glass for holding, and the hologram glass
A hologram laser unit having a gap formed in the cap glass , wherein the hologram glass and the cap glass are bonded to each other.
Vacant areas that are partially glued and fixed with adhesive
A hologram laser unit , wherein the gap is communicated with the outside of the package as an air passage .