JP2570756B2 - Driving method of optical shutter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical shutter driving method for driving an optical shutter by applying an electric field to an optical shutter using a material having an electro-optical effect such as PLZT. It is.

BACKGROUND OF THE INVENTION As shown in FIG. 1, an optical shutter (1) using a material having an electro-optical effect such as PLTZ has electrodes (2) and (3) on both sides thereof, When an electric field of an appropriate intensity is applied to the optical shutter (1) from (4) through these electrodes (2) and (3), light incident through the polarizer (5) is applied to the optical shutter (1). The light is polarized in (1), and the polarized light passes through the analyzer (6). Then, an appropriate electric field is applied to the optical shutter (1) to polarize the light, and the shutter is opened and closed depending on whether or not the light is transmitted through the analyzer (6).

Here, in the optical shutter shown in FIG. 1, the relationship between the intensity of the electric field applied to the optical shutter and the intensity of the transmitted light transmitted through the analyzer is represented by a characteristic curve as shown in FIG. In the figure, the horizontal axis indicates the intensity of the electric field applied to the optical shutter, and the vertical axis indicates the intensity I of the transmitted light passing through the analyzer. As shown in the figure, in the optical shutter as described above, the polarization of light in the optical shutter due to the action of the electric field is normally 90 ° polarized at a specific electric field that matches the analyzer, so Wavelength electric field Eλ / 2
Is applied, the transmitted light intensity is maximized.

For this reason, when such an optical shutter is driven, a half-wavelength electric field Eλ / 2 that maximizes the transmitted light intensity as described above is usually applied to the optical shutter.

On the other hand, the present inventors have repeated research on applying an optical shutter array having many optical shutters to an electrophotographic printer or the like by applying the characteristics of the optical shutter. here,
When such an optical shutter array is used in an electrophotographic printer or the like, it is necessary to pulse drive each optical shutter element so as to match the rotation speed of the photosensitive drum for forming an image. Therefore, when the optical shutter element is pulse-driven, if the half-wavelength electric field Eλ / 2 at which the transmitted light intensity is maximized is applied to the optical shutter element in a pulsed manner, the light is transmitted shortly. If the time is too short, the photosensitive member cannot be sufficiently exposed, and only a poorly contrasted image can be obtained. On the other hand, in order to sufficiently expose the photoconductor,
The pulse width of the half-wavelength electric field Eλ / 2 applied to the optical shutter element must be increased, which causes a problem that the system speed of a printer or the like is remarkably reduced and high-speed processing cannot be performed.

Therefore, the present inventors have further studied the characteristics of such an optical shutter when an electric field is applied. When the half-wavelength electric field Eλ / 2 is applied to the optical shutter, the transmitted light is It has been found that the rise of the intensity is poor, it takes time to obtain the predetermined transmitted light intensity, and the response speed of the optical shutter is slow.

The present invention has been made in view of such circumstances, and provides a driving method of an optical shutter that hastens the rise of transmitted light intensity in the optical shutter and improves the response speed of the optical shutter.

[Means for Solving the Problems] According to the present invention, when an electric field is applied to an optical shutter made of a material having an electro-optical effect to drive the optical shutter, the amount of transmitted light from the optical shutter in terms of electrostatic characteristics. Is applied as an initial electric field, and then an electric field near the electric field at which the amount of transmitted light becomes maximum is applied to drive the optical shutter.

[Operation] As described above, when an electric field higher than the electric field at which the transmitted light intensity from the optical shutter is maximum is applied to the optical shutter as the initial electric field, the transmitted light intensity from the optical shutter rapidly increases and becomes very short. A desired transmitted light intensity can be obtained in time, and the response speed of the optical shutter can be significantly improved.

Embodiment An embodiment of the present invention will be specifically described below with reference to the accompanying drawings.

In the optical shutter of this embodiment, PLZT was used as a material having an electro-optical effect, and the phase difference between the polarizer and the analyzer was set to 90 °.

First, a voltage (half-wave voltage) Vλ / 2 when a half-wavelength electric field Eλ / 2 is applied to the optical shutter and a voltage obtained by adding an excess voltage Vx of 10 V, 20 V, and 30 V to the half-wavelength voltage Vλ / 2 ( (Vλ / 2 + Vx), the change in transmitted light intensity over time was examined. This result is the third
Shown in the figure. In the figure, the vertical axis represents the half-wavelength electric field Eλ.
/ 2, the final transmitted light intensity (peak in Fig. 2) is 100
Represents the relative transmitted light intensity (%), and the horizontal axis represents time (msec). As is clear from the figure, the higher the excess voltage Vx applied, the faster the rise of the transmitted light intensity and the faster the response speed.On the other hand, over time, the transmitted light intensity gradually decreases. all right.

Next, an example in which the optical shutter array constituted by such an optical shutter is used in an electrophotographic printer as shown in FIGS. 12 (a) and 12 (b) will be described.

When used in such an electrophotographic printer, as shown in the figure, light from a halogen lamp (11) is led to a light guide (13) through a heat ray absorbing filter (12), and the light guide (13) The guided light is applied to the rod lens (14), and the light applied by the rod lens (14) is collected at the optical shutter array (10). An electric field having a required pulse width is applied to the optical shutter element at the location to transmit light. Then, the light transmitted through the optical shutter element is condensed by the converging rod lens array (15) and irradiated on the photosensitive drum (16) to form dots on the photosensitive drum (16). ing.

Here, the lighting time in such dot formation is:
The lighting time is at most several hundred microseconds, and the lighting time becomes shorter as the system speed of the electrophotographic printer increases. Now, assuming that the lighting time is 300 μsec,
The change in the transmitted light intensity when each voltage similar to that shown in the figure was applied to the optical shutter with a pulse having a width of 300 μsec was examined. These results are shown in FIG. 4 to FIG. FIG. 4 shows the case where the voltage is Vλ / 2, and FIG. 5 shows the case where the voltage is Vλ / 2 + 10.
In the case of V, FIG. 6 shows the case where the voltage is Vλ / 2 + 20 V, and FIG. 7 shows the case where the voltage is Vλ / 2 + 30 V. The vertical axis of each figure indicates the final transmitted light intensity by the half-wavelength electric field Eλ / 2. Represents the relative transmitted light intensity (%) and the driving voltage when is 100, the horizontal axis represents time (μsec), and the pulse of the driving voltage is indicated by a broken line. In addition, the hatched portions in each drawing represent the integrated transmitted light amount.

As a result, when the lighting time is 300 μsec,
It was found that when a voltage near Vλ / 2 + 20 V was applied, the integrated transmitted light amount was the highest, and when this voltage was applied to the optical shutter, the photosensitive member could be effectively exposed.

However, when driving this optical shutter array with a pulse voltage of 100 μsec width, it is better to use a voltage of Vλ / 2 + 30 V or more as a driving voltage. An appropriate excess voltage Vx is added accordingly.

The electric field applied to the optical shutter is a half-wavelength electric field Eλ.
The higher the value of / 2, the faster the rise of the transmitted light intensity and the faster the response speed.
Taking advantage of the fact that driving with the half-wavelength electric field Eλ / 2 is more stable, as shown in FIG. It is also possible to apply an electric field to which Ex is applied, and then eliminate the excess electric field, and drive with a half-wavelength electric field Eλ / 2. In this case, as shown in FIG.
The transmitted light intensity rises quickly, and thereafter, the transmitted light intensity is stabilized, and the integrated transmitted light amount can be maximized regardless of the lighting time. For reference, the broken line in FIG.
The change in transmitted light intensity when a half-wavelength electric field Eλ / 2 is applied to the optical shutter from the beginning of driving is shown.

Further, in driving the optical shutter as described above, as shown in FIG. 10, only when the optical shutter is started, the excess voltage Vx is applied to the half-wavelength voltage Vλ / 2 by applying a pulse to the optical shutter. Or as shown in FIG.
A half-wavelength voltage Vλ / 2 is applied to one electrode of the optical shutter, and a negative pulse voltage of −Vx is applied to the ground electrode in synchronization only at the time of startup.

[Effects of the Invention] As described in detail above, when the optical shutter is driven as in the present invention, the transmitted light intensity in the optical shutter increases very quickly, and a desired transmitted light intensity can be obtained in a very short time. As a result, the response speed of the optical shutter is significantly improved.

As a result, even when the photosensitive member is exposed in an electrophotographic printer or the like, there is an excellent effect that the contrast can be increased and the system speed can be increased.

[Brief description of the drawings]

1 is a principle diagram of the optical shutter, FIG. 2 is a characteristic diagram of the optical shutter, and FIG. 3 is a half-wave voltage Vλ / 2 and a voltage obtained by adding an excess voltage Vx to the half-wave voltage Vλ / 2. FIG. 4 to FIG. 7 are diagrams showing the change in transmitted light intensity when the voltage is applied, and FIGS. 4 to 7 show the transmission light intensity when each voltage used in FIG. FIG. 8 is an explanatory view showing the state, FIG. 8 is an explanatory view showing a case where the integrated transmitted light amount in the optical shutter is maximized regardless of the lighting time, and FIG.
FIG. 10 is an explanatory view showing the state of an electric field applied to the optical shutter to obtain the state shown in FIG. 10, and FIGS. 10 and 11 are explanatory views showing the state of the voltage applied to the optical shutter to obtain the state shown in FIG. FIGS. 12A and 12B are a schematic side view and a plan view of an electrophotographic printer using an optical shutter. (1) Optical shutter, (10) Optical shutter array

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kane Matsubara 2-30 Azuchi-cho, Higashi-ku, Osaka-shi, Osaka Inside Osaka International Building Minolta Camera Co., Ltd. (72) Hirohisa Kitano 2-30 Azuchi-cho, Higashi-ku, Osaka, Osaka Address: Osaka International Building Minolta Camera Co., Ltd. (72) Inventor: Tomohiko Masuda 2-30, Azuchicho, Higashi-ku, Osaka City, Osaka Prefecture Osaka International Building Minolta Camera Co., Ltd. (56) References: JP-A-50-51692 (JP, A) JP-A-59-128514 (JP, A) JP-A-56-62222 (JP, A)

Claims (1)

(57) [Claims] When an electric field is applied to an optical shutter made of a material having an electro-optical effect to drive the optical shutter, an electric field higher than the electric field at which the amount of transmitted light from the optical shutter becomes maximum in electrostatic characteristics is initially set. A method for driving an optical shutter, comprising: applying an electric field, and then applying an electric field near an electric field at which the amount of transmitted light is maximum to drive the optical shutter.