JP2890649B2 - Driving method of optical shutter device and optical shutter device using this method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving an optical shutter device using an electro-optical material such as PLZT for optical modulation and an optical shutter device using the same.

[Conventional technology]

An optical shutter device using an electro-optical material such as PLZT for light modulation has been proposed for application as, for example, an optical writing device of an optical printer. In such an optical printer, the amount of light transmitted through the optical material changes according to the drive voltage applied to each electro-optical material of the optical shutter device, and this changes the density of the recording.

However, the plurality of electro-optical materials are constantly irradiated with light from a light source, and when a driving voltage is applied to a necessary portion of the electro-optical material, the light modulating portion at that portion transmits the recording light. However, in long-term use, the internal polarization of the electro-optical material due to the repetition of the application of the drive voltage for recording in the state of light irradiation,
That is, it has been found that the drive voltage at which the transmittance is maximized, that is, the so-called half-wavelength voltage is changed by the occurrence of light fatigue.

In order to prevent the change in the half-wavelength voltage by eliminating the above-mentioned internal polarization and recovering the light fatigue, the present applicant firstly sets each electric voltage during a standby period in which no recording is performed. It has been proposed that an optical material is applied with a photo-fatigue recovery voltage that generates an electric field in the direction opposite to the electric field generated by the drive voltage applied during the recording period (see, for example, Japanese Patent Application No. 1-170965). ).

[Problems to be solved by the invention]

However, the optical shutter device in the optical printer of the prior application described above may cause the following inconvenience, and there is still room for improvement.

In other words, when recording is performed, a plurality of electro-optical materials for light modulation need to be adhered to toner based on the recording information, for example, in a negative-positive type optical printer. A driving voltage is applied to the electro-optical material corresponding to (1), and the frequency of application of the driving voltage differs for each electro-optical material.
Therefore, the degree of light fatigue naturally differs for each electro-optical material. On the other hand, in the above-described optical shutter device of the optical printer of the prior application, since the photo-fatigue recovery voltage is uniformly applied to all the electro-optical materials during the standby period, the driving voltage is reduced. If a light fatigue recovery voltage sufficient to recover light fatigue is applied to an electro-optical material that is frequently applied, the light-fatigue recovery of the electro-optical material to which the drive voltage is applied less frequently results in light fatigue. Conversely, a light fatigue recovery voltage that does not cause light-fatigue of an electro-optical material to which a drive voltage is not frequently applied cannot sufficiently recover light-fatigue of an electro-optical material to which a drive voltage is frequently applied.

In view of the above circumstances, it is an object of the present invention to provide a method of driving an optical shutter device capable of accurately recovering from light fatigue regardless of the frequency of application of a driving voltage to each of a plurality of electro-optical materials, and an optical shutter using the same. It is to provide a device.

[Means for solving the problem]

In order to achieve the above object, the optical shutter device according to claim 1, after the end of the image projection operation by the control unit,
An optical shutter device provided with light fatigue compensation means for applying a voltage to each of a plurality of electro-optical materials to generate an electric field in a direction opposite to that in the image projection operation based on image information in the image projection operation.

Further, in the driving method of the optical shutter device according to the present invention, after the image projection operation is completed by the control means, a voltage for generating an electric field in a direction opposite to that during the image projection operation is applied to each of the plurality of electro-optical materials. This is a driving method of an optical shutter device that is applied based on image information at the time of a projection operation and compensates for optical fatigue of a plurality of electro-optical materials.

(Operation)

In other words, optical fatigue caused by internal polarization of the electro-optical material caused by applying a driving voltage for generating a unidirectional electric field for recording can be recovered by applying a voltage for generating an electric field in a direction opposite to that during recording, and Since the application of the voltage for recovering from light fatigue is performed based on the recording information at the time of the recording operation at the end of the recording operation, the electro-optical material which performs a large amount of recording during the recording operation and has a high frequency of application of the drive voltage For the electro-optical material, the voltage for photo-fatigue recovery is applied over a long period of time or with a large voltage value, while the frequency of application of the drive voltage is small without performing much recording during the recording operation. , Such as applying a voltage for light fatigue recovery in a short time or with a small voltage value,
The application of the voltage for light fatigue recovery can be made different according to the frequency of application of the drive voltage for recording, and the recovery can be performed in accordance with the degree of light fatigue.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 2, a charging device (2) for uniformly charging the surface of the photoconductor (1) around a drum-shaped photoconductor (1) driven and rotated in a fixed direction, An optical print head (PH) as a light modulator for forming an electrostatic latent image corresponding to recorded information on the photoreceptor (1), and a toner attached to the electrostatic latent image for visualization. And a toner image formed on the photoreceptor (1) by the operation of the developing device (3) is transferred onto a recording paper (not shown), and the recording paper is transferred to the photoreceptor (1). ), A main eraser (5) for eliminating residual charges on the photoconductor (1), and cleaning for scraping off residual toner on the photoconductor (1). And an optical pre-recorder for recording recording information on recording paper in an electrophotographic manner. It has configured data.

The optical print head (PH) includes a light source (7), a reflecting mirror (8), and a PLZT array (9), which is a plurality of electro-optical materials arranged side by side along the longitudinal direction of the photoconductor (1). , A pair of polarizers (1
(0) and (11), and a gradient index lens array (1) for irradiating and imaging the light passing through the optical shutter (S) onto the surface of the photoconductor (1).
2) and

The PLZT array (9) is obtained by arranging a plurality of PLZT chips of a transparent sintered body in one row.
As shown in FIG. 1, a plurality of PLZT micro-sections (shown by capacitors in FIG. ₁ ) are arranged along the direction in which the PLZT chips are arranged in units of dots which are units of image formation.
To form a (9 _n), the plurality of micro-compartments _{(9 1) ~ (9 n} ) each minute section for applying a driving voltage for modulation to _{(9 1) ~ (9 n} ) for each of the Individual electrode (E ₁ )
And (E _n), is formed with a common electrode is shared microcompartments all _{PLZT (9 1) ~ (9} n) (E c).

Wherein the plurality of PLZT of microcompartments _{(9 1) ~ (9 n} ), via a respective separate individual electrodes _{(E 1) ~ (E n} ), the driving pulse is selectively applied from the driver (13) It is configured to be performed. The drive (13) is supplied with a drive voltage [V _h ] from a drive power supply and transferred from a recording memory (M) via an EX-OR circuit (14) by operation control of a CPU (C). Then, the recording information stored in the shift register (15) and collectively held in the latch circuit (16) is input. The drive (13) is configured to apply the drive voltage at a predetermined pulse rate to a required minute section of PLZT based on the above-described recording information.

An optical print head (P) equipped with this PLZT array (9)
In H), as shown in FIG. 2, the light from the light source (7) passes through the polarizer (10) on the light source (7) side of the optical shutter (S). The polarizer (10) transmits only a polarized light component in a certain direction. The PLZT constituting the PLZT array (9) has birefringence, and when a predetermined voltage is applied, rotates the plane of polarization of the incident light by an angle corresponding to the applied voltage and transmits the light. The polarizer (11) on the photoconductor (1) side of the optical shutter (S) has an orthogonal Nicol arrangement in which the plane of polarization for transmitting light is different by 90 ° from the polarizer (10) on the light source (7) side. The individual electrodes (E ₁ ) to (E _n )
PLZT micro-compartment where no voltage was applied to (9 ₁ ) ~
The light transmitted through (9 _n ) is converted into a polarizer (11) on the photoconductor (1) side.
On the other hand, the light transmitted through the micro-sections (9 ₁ ) to (9 _n ) of the PLZT in which a predetermined voltage is applied to the individual electrodes (E ₁ ) to (E _n ) depends on the magnitude of the applied voltage. At the ratio, the light passes through the polarizer (11) on the photoconductor (1) side, is irradiated and imaged on the photoconductor (1) by the gradient index lens array (12), and the electric charge in that portion disappears. An electrostatic latent image is formed. Thereafter, in the developing device (3), the electrostatic latent image is visualized by attaching toner to the charge-disappearing portion, and a toner image is obtained. After that, the toner image is transferred and fixed on the recording paper to obtain a recording.

The first input terminal of the EX-OR circuit (14) has a first input terminal.
Of the EX-OR circuit (1) when the output of the flip-flop circuit (17) is input and this output is at “H” level.
The output (DATA2) of 4) becomes a signal having the same phase as the recording signal (DATA1) from the recording memory (M), and EX is output when the output of the first flip-flop circuit (17) is at “L” level. −
The output (DATA2) of the OR circuit (14) is configured to be input to the shift register (15) as a signal having a phase opposite to that of the recording signal (DATA2) from the recording memory (M). Then, a clock signal (CLK2) from the CPU (C) for switching the output of the first flip-flop circuit (17) is input to the second flip-flop circuit (18). And the common electrode (E _c ) according to the output from the second flip-flop circuit (18).
A switch (19) is provided for switching between a state in which the power supply is grounded and a state in which the drive voltage [V _h ] is supplied from the drive power supply.

The operation of the optical printer configured as described above will be described with reference to the time chart of FIG. During the recording period [P _R ], the output of the first flip-flop (17) is at “H” level, and the recording signal (DATA1) from the recording memory (M) is output.
Is input to the shift register (15) and latched by the latch circuit (16) according to the latch pulse (LATCH), and then the necessary electro-optical material (9 ₁ ) is selected according to the gate signal (CL). ) To (9 _n ), the driving voltage [V _h ] is applied to the individual electrodes (E ₁ ) to (E _n ). At this time, the common electrode (E _c ) is grounded, and an electric field in one direction is applied to a selected _{one of the} electro-optical materials (91) to (9 _n ). Thereby, as described above, the optical shutter (S)
In this case, selective transmission of recording light occurs, and recording for one line is performed.

If the recording of one page is completed by repeating the above operation,
That is, when the recording operation for a predetermined period is completed, a standby period [P _W ] is set, and the clock signal (CLK2) is changed to the first and second clocks.
And the flip-flops (17) and (18) are switched, and their outputs are switched, so that a signal having the opposite phase to the recording signal (DATA2) from the recording memory is input to the shift register (15). At the same time, the drive voltage [V _h ] from the drive power supply is supplied to the common electrode (E _c ). In this standby period [P _W ], the signal having the opposite phase to the recording signal (DATA1) from the recording memory input to the shift register (15) is applied to the latch pulse (LATCH) in the same manner as during the recording operation. Accordingly, the data is latched by the latch circuit (16).
Then, the drive voltage to the individual electrodes _{(E 1) ~ (E n} ) of the required electro-optic material in response to the gate signal _{(CL) (9 1) ~} (9 n) [V h] is applied.

The recording signal (DATA1) described above is a binary signal,
For example, when one page is simplified and expressed as being composed of five dots in the width direction and seven dots in the longitudinal direction,
The contents of the data are as shown in the figure. During the recording period [P _R ], the recording signal (DATA1) is input to the shift register (15) in the same phase, that is, with the same value for each line. Then, this recording signal (DA
When TA1) is “1”, the driving voltage [V _h ] is applied to the corresponding _{one of} the individual electrodes (E ₁ ) to (E _n ) via the driver (13), and the grounded common electrode An electric field having a magnitude of [V _h ] is generated between (E _c ) and (E _c ), and recording is performed as described above.

On the other hand, during the standby period [P _W ], the recording signal (DATA1)
Are input to the shift register (15) line by line with the opposite phase, that is, as shown in FIG. 5 in which "1" and "0" are reversed. When this signal is “1”, the driving voltage [V _h ] is applied to the corresponding _{one of} the individual electrodes (E ₁ ) to (E _n ) via the driver (13). The drive voltage [V _h ] is applied to the common electrode (E _c ) during the period [P _W ].
Is supplied, the electric field becomes [0]. On the other hand, when the signal input to the shift register (15) is “0”, the corresponding _one of the individual electrodes (E ₁ ) to (E _n ) is grounded, so that the common electrode (E _c ) An electric field having a magnitude of [−V _h ] is generated between the two.

The magnitude of the electric field in the recording period [P _R ] and the standby period [P _W ] are summarized in Table 1 below.

Therefore, the electro-optical material which participated in the recording in the recording period [P _R ], that is, the electric field having the magnitude of [V _h ] was applied to the recording at a timing corresponding to the information, is in the standby period [P _W ].
, An electric field having a magnitude of [−V _h ], that is, an electric field in a direction opposite to that in the recording operation is applied at the same timing.
On the other hand, no electric field is applied to the electro-optical material that has not been involved in the recording even during the standby period [P _W ]. This is shown in FIG.

In the embodiment of FIG. 6, the length of the recording period [P _R ] and the length of the standby period [P _W ] are the same, and in any period, the duty ratio, which is the ratio between the voltage application cycle and the pulse width, is [50%]. During the standby period [P _W ], the recording paper that has already been recorded is discharged, and a new recording paper that has not been recorded is introduced.

That is, the electric field of [−V _h ] is applied to the standby period [P _W ] by the same number of times as the number of times the electric field of [V _h ] is applied to the recording period [P _R ]. Therefore, the internal polarization of the electro-optical material caused by applying the electric field in one direction a predetermined number of times to perform recording is eliminated by applying the electric field in the opposite direction the same number of times, and the internal polarization, so-called light fatigue, is reduced. Accumulation can be prevented, and a change in the half-wavelength voltage in the electro-optical material due to light fatigue can be eliminated, so that high-quality recording without any unevenness can always be obtained.

That is, the CPU (C), the two flip-flop circuits (17) and (18), and the EX-OR circuit (14) constitute an optical fatigue compensation unit.

The operation for recovering from light fatigue may be performed after the end of the recording operation over a plurality of pages, and the period and the frequency are irrelevant as long as the end of the recording operation.

Next, another embodiment of the present invention will be described.

<1> In the embodiment shown in FIG. 8, the length of the standby period [P _W ] is shorter than the length of the recording period [P _R ]. The premise is that light fatigue can saturate at a certain level,
This is because, in such a case, when an electric field is applied in the opposite direction to recover from light fatigue, the same length as that at the time of recording may not always be required. In this embodiment, the standby period [P _W ] does not need to be excessively long for recovery from light fatigue, and the total recording time can be shortened when recording is performed continuously. In this embodiment, the duty ratio in both periods is set to [50%].

<2> The embodiment shown in FIG. 9 is an improvement of the embodiment shown in FIG. 8, and when the standby period [P _W ] is shorter than the recording period [P _R ], the recovery from light fatigue is insufficient. In this case, the duty ratio in the recording period [P _R ] is kept at [50%], while the duty ratio in the standby period [P _W ] is set to [100%].
%]. In this embodiment, the overall recording time can be reduced without causing insufficient recovery from light fatigue. Note that the duty ratio in the standby period [P _W ] can be set to any value other than [100%].

<3> In the above embodiment, the drive voltage [V _h ] is applied to the individual electrode (E _a ) using the signal obtained by inverting the recording signal (DATA 1), and the same drive voltage [E _c ] is applied to the common electrode (E _c ). _Vh ], but instead of this, although not shown, the same recording signal (DATA1) is used to apply a supply voltage from another drive power supply to the electro-optical material. An electric field in a direction opposite to that during recording may be applied.

〔The invention's effect〕

As described above, in the driving method of the optical shutter device according to the present invention and the optical shutter device using the same, each of the electro-optical materials is recovered in order to recover the light fatigue generated in a plurality of electro-optical materials due to long-time use. The frequency of application of the drive voltage according to the recorded information for, that is, it is possible to perform recovery corresponding to the degree of light fatigue, it is possible to prevent the recovery of light fatigue becomes insufficient or adverse effect, It has become possible to provide an optical printer capable of always accurately recovering from light fatigue and reliably preventing the occurrence of recording unevenness even after long-term use.

[Brief description of the drawings]

1 to 6 show an embodiment of the present invention, FIG. 1 is a schematic structural diagram, FIG. 2 is a schematic diagram around a photoreceptor, FIG. 3 is a time chart of a recording operation, FIG. 4 and FIG. FIG. 6 is an explanatory diagram of data, and FIG. 6 is a time chart of driving voltage application. 7 and 8 are time charts corresponding to FIG. 6 showing another embodiment. (1) ... photoconductor, (7) ... light source, (9 ₁₎ ~ (9 _n) ...
... electro-optic materials.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Koji Wakamiya, Investigator, Osaka International Building Minolta Camera Co., Ltd. 2-3-3 Azuchicho, Chuo-ku, Osaka-shi, Osaka, Japan Toshiaki Tsuda (56) References JP-A-51- 141650 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G02F 1/055 502

Claims (2)

(57) [Claims] 1. A light modulation section in which a plurality of electro-optic materials for light modulation are arranged in a row, and a driving voltage for light modulation according to image information is applied to each of the plurality of electro-optic materials. Control means for modulating light from a light source and projecting an image on a projection surface, after the image projection operation by the control means is completed, the image projection operation on each of the plurality of electro-optical materials. An optical shutter device comprising: a light fatigue compensating means for applying a voltage for generating an electric field in a direction opposite to the time based on image information at the time of the image projection operation. 2. A light modulating section in which a plurality of electro-optical materials for light modulation are arranged in a row, and a driving voltage for light modulation according to image information is applied to each of the plurality of electro-optical materials. A driving means for an optical shutter device that modulates light from a light source and projects an image on a projection surface, wherein after the image projection operation by the control means is completed, each of the plurality of electro-optical materials is provided. An optical shutter device, comprising: applying a voltage that generates an electric field in a direction opposite to that during the image projection operation, based on image information during the image projection operation, and compensating for light fatigue of the plurality of electro-optical materials. Drive method.