# US 7,072,272 B2 · Diffraction type optical pickup lens and optical pickup apparatus using the same

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- Number: US 7,072,272 B2
- Document ID: US7072272B2
- Status: Granted
- Kind: B2
- Application number: 10/075,345
- Filed: 2002-02-15
- Published: 2002-09-19
- Granted: 2006-07-04
- Earliest claimed: 2001-03-14
- Assignees: Fujinon Corporation
- Inventors: Kaneyoshi Yagi; Masato Kawabata; Toshiaki Katsuma
- Web page: https://patentgrep.com/patent/US7072272B2

## CPC

- G11B 7/1275: Two or more lasers having different wavelengths
- G02B 27/0037: {with diffracting elements (G02B27/0056 takes precedence; holographic optical elements G02B5/32; zone systems G02B5/1876)}
- G02B 27/4238: {in optical recording or readout devices (optical pick-up devices such as for CD, DVD or BD reader or recorder using diffraction optics G11B7/1353)}
- G02B 27/4288: {having uniform diffraction efficiency over a large spectral bandwidth}
- 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 7/13922: {passive}
- G11B 2007/0006: {adapted for scanning different types of carrier, e.g. CD & DVD}
- 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)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

In a diffraction type optical pickup lens, at least one surface of a convergent lens is formed with such an aspheric surface that a luminous flux having a wavelength λ1 is converged at a first predetermined position. At least one surface of the convergent lens is formed with a zone plate having such a wavelength selectivity that a luminous flux having a wavelength λ2 is converged at a second predetermined position whereas the luminous flux having a wavelength λ1 is transmitted therethrough as it is. The convergent lens is transparent to the luminous fluxes having the wavelengths λ1 and λ2.

## Claims

### Claim 1

A diffraction type optical pickup lens comprising a convergent lens having at least one surface formed with such an aspheric surface that a luminous flux having a wavelength λ1 is converged at a first predetermined position;
wherein at least one surface of said convergent lens is formed with a zone plate having such a wavelength selectivity that a luminous flux having a wavelength λ2 is converged at a second predetermined position whereas said luminous flux having said wavelength λ1 is transmitted therethrough as it is; and
wherein said convergent lens is transparent to said luminous fluxes having said wavelengths λ1 and λ2.

### Claim 2 (depends on 1)

A diffraction type optical pickup lens according to claim 1, wherein said zone plate is constituted by a concentric grating having a stepped cross section.

### Claim 3 (depends on 2)

A diffraction type optical pickup lens according to claim 2, wherein the number of steps in said stepped concentric grating is 3.

### Claim 4 (depends on 1)

A diffraction type optical pickup lens according to claim 1, wherein each of both surfaces of said convergent lens is formed with such a zone plate that said luminous flux having said wavelength λ2 is converged at said second predetermined position.

### Claim 5 (depends on 1)

A diffraction type optical pickup lens according to claim 1, wherein each of both surfaces of said convergent lens is formed with such an aspheric surface that said luminous flux having said wavelength λ1 is converged at said first predetermined position.

### Claim 6 (depends on 1)

A diffraction type optical pickup lens according to claim 1, wherein said zone plate is formed by depositing titanium dioxide into a predetermined form on a lens substrate.

### Claim 7 (depends on 1)

An optical pickup apparatus comprising the diffraction type optical pickup lens according to claim 1, said apparatus being adapted to record or reproduce two kinds of optical recording media having respective thicknesses different from each other;
wherein one of said optical recording media is recorded or reproduced by said luminous flux having said wavelength λ2, whereas the other is recorded or reproduced by said luminous flux having said wavelength λ1.

### Claim 8 (depends on 7)

An optical pickup apparatus according to claim 7, wherein a luminous flux incident on said diffraction type optical pickup lens is a substantially parallel luminous flux.

### Claim 9 (depends on 7)

An optical pickup apparatus according to claim 7, wherein NA with respect to said luminous flux for said one optical recording medium is set smaller than that with respect to said luminous flux for the other recording medium; and wherein said zone plate is formed on the surface of said convergent lens on a light source side.

### Claim 10 (depends on 9)

An optical pickup apparatus according to claim 9, wherein said one optical recording medium is CD-R, whereas the other optical recording medium is DVD.