# US 5,708,643 A · Multiple focus optical pickup system for alternatively reading a multiple number of optical disks

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- Number: US 5,708,643 A
- Document ID: US5708643A
- Status: Granted
- Kind: A
- Application number: 08/719,809
- Filed: 1996-09-25
- Granted: 1998-01-13
- Earliest claimed: 1995-09-29
- Assignees: Daewoo Electronics Co., Ltd.
- Inventors: Yang-Oh Choi; Ki-Tae Kim
- Web page: https://patentgrep.com/patent/US5708643A

## CPC

- G11B 7/1353: Diffractive elements, e.g. holograms or gratings {(diffraction gratings per se G02B5/18; holograms per se G02B5/32; grating systems G02B27/44)}
- G11B 7/1374: Objective lenses {(optical objectives per se G02B9/00)}
- G11B 2007/0006: {adapted for scanning different types of carrier, e.g. CD & DVD}
- G11B 2007/13727: {Compound lenses, i.e. two or more lenses co-operating to perform a function, e.g. compound objective lens including a solid immersion lens, positive and negative lenses either bonded together or with adjustable spacing}
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)

## Abstract

An optical pickup system for alternatively detecting an information signal from, e.g., a pair of optical disks loaded on a disk tray is described, wherein each of the optical disks may have a different thickness. The optical pickup system includes a light source for generating a light beam and an optical device provided with a first and a second parts, wherein a portion of the light beam impinging onto the first part is focused onto the first optical disk, and the remaining portion of the light beam impinging onto the second part is focused onto the second optical disk, thereby allowing the optical pickup system to detect an information signal from the respective optical disk.

## Claims

### Claim 1

An optical pickup system for selectively reading one of N optical disks loaded on a disk tray, wherein each of the optical disks has a respective recording surface and thickness different from each other, N being a positive even integer, said system comprising:
means for generating a light beam;
beam splitting means for partially reflecting the light beam to the recording surface of a selected optical disk; and
an optical device provided with N parts, each of the parts having a different focal length from each other to be able to focus light beam onto a corresponding optical disk, for dividing the reflected light beam into N portions, wherein one of N portions of the reflected light beam is focused on the recording surface of the selected optical disk after being transmitted through a part selected from the N parts of the optical device and then is reflected onto a part opposite to the selected part.

### Claim 2 (depends on 1)

The optical pickup system of claim 1 which further comprises detecting means, wherein the detecting means has a pair of reception surfaces capable of measuring a light beam intensity.

### Claim 3 (depends on 2)

The optical pickup system of claim 2, wherein each portion of the divided light beams, reflected from the recording surface of the selected optical disk to the optical device is impinged via the beam splitting means onto the pair of reception surfaces.

### Claim 4 (depends on 3)

The optical pickup system of claim 3, wherein the beam splitting means is disposed between the optical device and the detecting means.

### Claim 5

An optical pickup system for reading an information signal recorded on a recording surface of a selected one of a first and a second optical disks, the optical disks being disposed such that distances between the optical pickup system and the recording surfaces of the optical disks are different from each other, said optical pickup system comprising:
means for generating a light beam;
means for detecting an intensity of a light incident thereon; and
an optical device provided with a first and a second optical means, each of the optical means being divided by a central line and having different focal length, wherein a fraction of the light beam is delivered to the recording surface of the selected optical disk via one of the optical means and a reflected light beam from the recording surface of the selected optical disk is delivered to the detection means via the other optical means.

### Claim 6 (depends on 5)

The optical pickup system of claim 5, further comprising beam splitting means for partially reflecting the light beam from the generation means, thereby providing said fraction of the light beam.

### Claim 7 (depends on 6)

The optical pickup system of claim 6, wherein said beam splitting means is disposed between the optical device and the detection means.

### Claim 8 (depends on 5)

The optical pickup system of claim 5, wherein said detection means has a pair of reception surfaces.

### Claim 9 (depends on 5)

The optical pickup system of claim 5, wherein the central line of the optical device serves as a knife edge.