Optical information reproduction apparatus using homodyne phase diversity detection with improved SNR

Patent metadata

Field	Value
Publication number	US-8958278-B2
Application number	US-201313875350-A
Country	US
Kind code	B2
Filing date	May 2, 2013
Priority date	Jul 30, 2012
Publication date	Feb 17, 2015
Grant date	Feb 17, 2015

Abstract

In the optical information reproduction apparatus using Homodyne phase diversity detection, the S/N ratio of a reproduced signal is deteriorated due to the influence of a quantization noise generated in an A/D converter for digitalizing a differential signal. The optical information reproduction apparatus is arranged to have the A/D converter for digitalizing the differential signal having a vertical resolution equal to or higher than 9 bits.

First claim

What is claimed is:

1. An optical information reproduction apparatus using Homodyne phase diversity detection comprising:
a light source adapted to irradiate an optical information recording medium with light;
a plurality of detectors adapted to detect a plurality of interference lights different from each other in a phase relationship between a signal light from the optical information recording medium and a reference light branched from the light source;
a differential circuit adapted to generate a differential signal from the detectors; and
an A/D converter having a vertical resolution of greater than or equal to 9 bits, and adapted to digitalize the differential signal,
wherein the number of bits of the vertical resolution is determined based on a minimum modulation.

2. The optical information reproduction apparatus according to claim 1 , wherein
the number of bits of the vertical resolution fulfills the following denoting the number of bits with R, and the minimum modulation with m min

R
≥

7
+

log
2

(

2
⁢

2

1
-

1
-

m
min

)

.

(
12
)

3. An optical information reproduction apparatus using Homodyne phase diversity detection comprising:
a light source adapted to irradiate an optical information recording medium with light;
a plurality of detectors adapted to detect a plurality of interference lights different from each other in a phase relationship between a signal light from the optical information recording medium and a reference light branched from the light source;
a differential circuit adapted to generate a differential signal from the detectors;
an A/D converter having a vertical resolution of greater than or equal to 9 bits, and adapted to digitalize the differential signal; and
an absolute value calculator adapted to obtain an absolute value of the differential signal disposed between the differential circuit and the A/D converter.

4. The optical information reproduction apparatus according to claim 3 , wherein
the number of bits of the vertical resolution fulfills the following denoting the number of bits with R, and the minimum modulation with m min

R
≥

7
+

log
2

(

2
⁢

2

1
-

1
-

m
min

)

-
1.

(
13
)

5. The optical information reproduction apparatus according to claim 1 , further comprising:
a gain/offset adjustment circuit adapted to perform a gain adjustment and/or application of an offset on the differential signal disposed between the differential circuit and the A/D converter.

6. The optical information reproduction apparatus according to claim 1 , further comprising:
a gain/offset adjustment circuit adapted to perform a gain adjustment and/or application of an offset disposed in a posterior stage of the A/D converter.

7. An optical information reproduction apparatus using Homodyne phase diversity detection comprising:
a light source adapted to irradiate an optical information recording medium with light;
a plurality of detectors adapted to detect a plurality of interference lights different from each other in a phase relationship between a signal light from the optical information recording medium and a reference light branched from the light source;
a differential circuit adapted to generate a differential signal from the detectors;
an A/D converter having a vertical resolution of greater than or equal to 9 bits, and adapted to digitalize the differential signal; and
an optimization circuit adapted to obtain coefficients of the following denoting the differential signals with Sig 1 , Sig 2

Sig
⁢

⁢

1
2

+

r
2

⁢
Sig
⁢

⁢

2
2

-

2
⁢
rs
⁢

⁢
sin
⁢

Assignees

• Hitachi Consumer Electronics

Inventors

• Kurokawa Takahiro
• Kikugawa Atsushi

Classifications

• G11B7/005 Primary

  Reproducing (G11B7/0065 takes precedence) · CPC title

• G11B20/10481 Primary

  optimisation methods · CPC title

• G11B20/10009

  Improvement or modification of read or write signals · CPC title