Multi-channel optical modulator

Details Multi-channel optical modulator Multi-channel optical modulator

2000-11-30

2002-09-10

Mack, Ricky (Department: 2873)

Optical: systems and elements

Optical modulator

Light wave temporal modulation

C359S305000

Reexamination Certificate

active

06449083

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a multi-channel optical modulator used an external modulator for a laser recording apparatus such as laser printer and laser plotter.
BACKGROUND ART
A multi-channel optical modulator has a plurality of elastic wave generating sources, and the number of light beams corresponding to its number can be modulated simultaneously and independently, which allows to record at a higher speed by scanning at the same speed as when recording by a single light beam. Further, at the same recording speed, the recording density is higher than when using a single light beam. Therefore, the demand for multi-channel optical modulator is increasing along with the mounting requirement for recording at higher density and higher speed.
A conventional multi-channel optical modulator is described below.
As shown in FIG.
4
and
FIG. 5
, a first electrode
103
is formed on the entire surface of one side of an acoustic-optical medium
101
, and a piezoelectric element
102
is disposed thereon. Five second electrodes
104
are provided on the piezoelectric element
102
, and thereby five transducers are formed.
A first lead wire
105
is connected nearly to the center of each second electrode
104
, and a second lead wire
106
corresponding to each first lead wire
105
is mutually connected to both ends of the first electrode
103
. The first lead wire
105
and second lead wire
106
are connected to each driving signal source
107
.
In thus constructed multi-channel optical modulator, the operation is described below.
First, the piezoelectric element
102
is oscillated by an alternating current signal supplied from the first lead wire
105
and second lead wire
106
, and becomes an elastic wave generating source. Therefore, the acoustic-optical medium
101
has as many elastic wave generating sources as the number of transducers, that is, five. The generated elastic wave propagates vertically on the transducer mounted surface of the acoustic-optical medium
101
, and acts on the light beam passing through the propagation area, thereby generating a diffracted light. This mode is shown in FIG.
7
. Herein, “I” denotes an incident light, “I
1
” is a diffracted light, and “I
0
” represents a non-diffracted transmission light. Since the diffracted light intensity is proportional to the elastic wave intensity, that is, the driving signal strength, desired optical recording is realized by varying the driving signal strength depending on the recording pattern.
Components of this multi-channel optical modulator are expressed in a circuit diagram in FIG.
6
.
Herein, the first lead wires
105
and second lead wires
106
are indicated by coil symbols because they have a very slight inductance. Reference numeral
108
indicates an output impedance of the driving signal source
107
, and the driving signal sources
107
are commonly grounded by connecting among the transducers. The first electrode
103
is commonly shared among the transducers.
In this structure, when one transducer is driven, the voltage generated by the inductance of the second lead wire
106
may drive the output impedance
108
and the first electrode
103
, or the piezoelectric element
102
of other transducer through the first electrode
103
, thereby generating a crosstalk.
DISCLOSURE OF THE INVENTION
It is hence an object of the invention to present a multi-channel optical modulator small in crosstalk.
To achieve the object, the multi-channel optical modulator of the invention comprises an acoustic-optical medium, a plurality of first electrodes provided on one side of this acoustic-optical medium, a plurality of piezoelectric elements provided on the first electrodes, a plurality of second electrodes provided on the piezoelectric elements, a plurality of first lead wires connected individually to the second electrodes, and a plurality of second lead wires connected individually to the first electrodes, in which the first electrodes are independent of individual transducers, and therefore the voltage generated in the second lead wire of any transducer may not be applied to the piezoelectric element of any other transducer, so that a generation of crosstalk may be prevented.


REFERENCES:
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patent: 4696551 (1987-09-01), Amano et al.
patent: 5657152 (1997-08-01), Kadota
patent: 5929893 (1999-07-01), Son et al.
patent: 2001/0035585 (2001-11-01), Ahn et al.
patent: 100238 (1984-02-01), None
patent: 1-131526 (1989-05-01), None
patent: 5-102297 (1993-04-01), None
patent: 5-116139 (1993-05-01), None
patent: 6-226972 (1994-08-01), None

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