KR19990020820U - Optical detection device of optical pickup - Google Patents

Abstract

The present invention relates to an optical pickup device for optical pickup that can be manufactured in a compact and compact structure by detecting two focusing error signals using two independent photodiodes. In particular, a laser beam emitted from a light source is a signal of a disk. A light detecting device having a lens for focusing on a recording surface, condensing light reflected from the disk, and detecting a focusing error signal to detect a change in intensity of the reflected light so that the lens can focus on the disk. In the above, the upper photodiode and the lower photodiode on the same axis is provided to be spaced apart by a predetermined interval and the upper photodiode is provided with a hole for sending the reflected light toward the lower photodiode.

Description

Optical detection device of optical pickup

The present invention relates to a photodetector for optical pickup, and more particularly, to a photodetector for optical pickup, in which a configuration is simplified by detecting a focusing error signal using an independent photodiode.

In general, an optical pickup apparatus focuses a light source for generating a laser light and a laser light emitted from the light source on a signal recording surface of the disk, and collects the light reflected from the disk on a photodetector and the light reflected from the disk. It is composed of a photodetector for detecting a change in intensity and reproducing a signal recorded on the disk, and detecting a focusing error signal (FES) so that the objective lens can always be focused on the disk.

FIG. 1 is a schematic diagram of a conventional photodetector, which includes a light source 1 for generating a laser light on an upper surface of a substrate 5 and a prism 4 for deflecting an exit beam from the light source 1 in both directions. do. Among the bidirectional beams reflected by the prism 4, the beam reflected upward is sent toward the lens and the disk, and the beam reflected inside the prism 4 is directed toward the multi-segment photodiode 2 and 3.

The photodiodes 2 and 3 serve as photodetectors and are mounted on the substrate 5 in a state where the focus of the lens and the disc is exactly matched and the gap between them is determined.

FIG. 2 is a schematic view of a conventional photodetector device in which a light source 1 for generating laser light is provided at the center of the substrate 5 and a multi-segment photodiode 2, 3 is provided at both sides thereof.

However, the conventional photodetector has a disadvantage in that an assembly error for mounting the multi-segment photodiodes 2 and 3 in the correct position of the substrate 5 occurs so that the focus of the lens and the disk cannot be exactly matched. (2) (3) and the light source (1) to be assembled on one substrate 5 has the disadvantage that the volume is large.

The present invention has been made in view of the conventional problems, and an object of the present invention is to detect a focusing error signal using two independent photodiodes, so that the configuration of the optical pickup of the optical pickup can be made compact and compact. In providing.

1 is a schematic view showing a conventional photodetector device;

2 is a schematic view showing a photodetector of another conventional embodiment;

3 is a schematic diagram of an optical pickup device of the present invention;

Figure 4a, b, c is a schematic view of the present invention photodetector.

<Description of Symbols for Main Parts of Drawings>

10 light source 11 lens

12: disk 14: upper photodiode

15: lower photodiode 16: hole

In order to achieve the above object, the present invention is provided with a lens for focusing the laser light emitted from the light source on the signal recording surface of the disk, condensing the light reflected from the disk and then detecting the intensity change of the reflected light A photodetector for detecting a focusing error signal so that a lens can focus on a disk, wherein the upper photodiode and the lower photodiode are provided to be spaced apart from each other on a same axis, and the upper photodiode reflects the reflected light to the lower portion. It is characterized by a hole for sending towards the photodiode.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a schematic view of the optical pickup device of the present invention. A light source 10 for generating a laser light is provided, and a lens 11 for focusing the laser light emitted from the light source 10 on the signal recording surface of the disk 12 is provided. The lens 11 is composed of an objective lens and focuses the light reflected from the disk onto the photodetector 13. The photodetector 13 detects the change in the intensity of the light reflected from the lens 11 and the disk 12 to reproduce the signal recorded on the disk 12, so that the lens 11 can always focus on the disk. Detect a focusing error signal (FES).

4 is a schematic view of a photodetector of the present invention, and FIG. 4A shows a focused state. The photodetector 13 is composed of an upper photodiode 14 and a lower photodiode 15 and the size of the hole 16 of the upper photodiode 14 in a state where the focus of the lens 11 is formed on the disk 12. And the height difference between the upper and lower photodiodes 14 and 15. The lower photodiode 15 is installed on the surface of the substrate 17, and the upper photodiode 14 is provided at a predetermined distance from the upper portion of the substrate 17 through the support 18.

The present invention configured as described above is the same as the output of the upper photodiode 14 and the lower photodiode 15 in the focused state as shown in Figure 4a, the distance between the lens 11 and the disk 12 as shown in Figure 4b The output is different when the lens 11 and the disk 12 is close when the case is lost or as shown in Figure 4c. Therefore, by comparing the output difference between the upper photodiode 14 and the lower photodiode 15, the focus distance between the lens 11 and the disk 12 can be adjusted and a focusing error signal is detected.

As described above, according to the present invention, by using two independent photodiodes without using two conventional four-segment photodiodes, an effect of price reduction is expected. In the process of fixing on the substrate, as the upper and lower diodes are located on the same axis, the assembly is accurate and miniaturization is possible because the lens and the photodiode are separated and do not use an integrated module.

Claims (2)

A lens is provided to focus the laser light emitted from the light source on the disk's signal recording surface, and collects the light reflected from the disk, and then detects a change in the intensity of the reflected light so that the lens can focus on the disk. In the photodetector for detecting a focusing error signal so that, And an upper photodiode and a lower photodiode spaced apart from each other on the same axis, and the upper photodiode has a hole for transmitting the reflected light toward the lower photodiode. The method of claim 1, wherein when the focal point of the lens and the disk are in focus, the hole size of the upper photodiode and the gap between the upper and lower photodiodes are determined so that the output of the upper and lower photodiodes is the same. Optical detection device of optical pickup.