JP2569516B2 - Driving device for optical shutter array - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for an optical shutter array, and more particularly, to a driving device for an electro-optical shutter array expected to be applied to an optical printer.

2. Description of the Related Art A laser printer converts an electrical signal into an ON / OFF signal of a laser beam using an acousto-optic modulator, scans the laser beam with a rotating polygon mirror, records information on a photosensitive drum, and transfers the information to paper. Things. If an optical shutter array is used,
Since an acousto-optic modulator and a rotating polygon mirror are not required, a compact and highly reliable printer can be obtained. Recently, optical printers using an optical shutter array composed of liquid crystal are being put into practical use, but optical printers having an optical shutter array composed of a substance having an electro-optical effect, for example, PLZT, are expected to be faster than the above printers. it can.

Conventionally, this PLZT optical shutter array has been
As described in JP-A-8842, driving is performed by sequentially operating drive circuits individually provided for individual optical shutters constituting an optical shutter array. However, when considering application to an optical printer, the number of optical shutters is 2,000 to 2,500 in A4 size, and the length of the array is 30 cm or more. Therefore, the driving device must have a very complicated configuration, and , Even if IC is used, it is necessary for driving
ICs are as many as 10-20.

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problem, that is, the problem that the configuration of the driving device of the optical shutter array is complicated.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a plurality of blocks commonly provided in a plurality of blocks, each of which is connected to one end of a plurality of optical shutter elements included in each block. Individual electrodes, voltage applying means for selectively applying a voltage to the plurality of individual electrodes, independently provided for each block, and commonly connected to the other ends of the plurality of optical shutter elements included in each block. A plurality of common electrodes, a plurality of switching elements respectively connected to the plurality of common electrodes, and control means for sequentially activating the plurality of switching elements, and the common electrode of each block is Connected to a line for keeping the common electrode at a predetermined potential when the switching element is activated,
An optical shutter array driving device in which a current control element for interrupting a current flowing in the line when a switching element of another block is activated is provided in the line.

According to the driving device of the optical shutter array of the present invention, an electric field is formed in the optical shutter element in the block activated by the switching element, to which the voltage is applied by the voltage applying means via the individual electrode. At this time,
The common electrode in another block that is not activated is kept at a predetermined potential by a line connected to the common electrode, and a current flow is interrupted by a current control element provided on this line.

Examples Hereinafter, the present invention will be specifically described with reference to examples shown in the accompanying drawings.

FIG. 1 shows a driving device according to one embodiment. (1) is an optical shutter array composed of PLZT, and has M × N optical shutters (1).
1) are arranged one-dimensionally, and the optical shutter is equivalently shown by a condenser. M × N optical shutters (11)
Are divided in advance into M blocks (G ₁ ), (G ₂ ),..., (G _M ) with N blocks as one block in the arrangement order.

(2) is a driving IC containing N driving elements, and includes a driving bus (2B) composed of N lines connected to the output terminals of each driving element. M blocks (G ₁ ),
The N control electrodes of each of the optical shutters (G ₂ ),..., (G _M ) are individually connected to the N lines of the drive bus (2B) in a fixed relationship. A high voltage (Vh) of 50 to 100 V for driving the optical shutter (11) is supplied to the driving IC (2).

The N-bit shift register (3) to which the serial data signal (DATA) is input accepts the data signal only during the input of the strobe signal (STROBE), and the received data signal is bit by bit by the clock (CLK). Will be shifted. The latch circuit (4) is connected to the N
When the shift register (3) receives N data signals (DATA), the shift register (3) latches the N data signals. The driving IC (2) sets the N lines of the driving bus (2B) to "H" (high level) or "L" (low level) according to the N data signals latched by the latch circuit (4). I do.

The circuit (5) is composed of blocks (G ₁ ), (G ₂ ), ..., (G _M )
Are activated in this order. The ground side electrode of the optical shutter (11) constituting each block of the blocks (G ₁ ), (G ₂ ),..., (G _M ) is electrically shared and the common electrodes (11c), (12c), , (1Mc), and a circuit unit consisting of only two diodes and a transistor is connected to each of the common electrodes. Connection of this unit, when a representative of the ones of the block (G _1), connect the anode of the diode (D ₁ c) to the common electrode (11c), NPN to the cathode of the diode (D ₁ c)
Connect the collector of the type transistor (Q ₁ ) and ground the emitter. The other diode (D ₁ ) has a configuration in which the anode side is grounded and the cathode is connected to the common electrode (11c). Preferably, both the diodes (D ₁ c) and (D ₁ ) are Schottky diodes.

A transistor (Q ₁ ) as a switching element,
(Q _2), ..., each of the collectors of the (Q _M), resistance _{(R 1), (R 2} ), ..., via the (R _M) is connected to the high voltage (Vh), the base of each Base resistance (r ₁ ),
It is connected to the M output counter circuit (6) via (r ₂ ),..., (R _M ). The counter circuit (6) to which the clock (CLK) is input turns on one of the outputs of 1, 2,... M for a certain period of time, and every time a certain number of clocks (CLK) are calculated, 1, 2,. Are switched in this order. Output 1
Are connected to the transistor (Q ₁ ), the output 2 is connected to the transistor (Q ₂ ), and the output M is connected to the transistor (Q _M ). The transistors (Q ₁ ), (Q ₂ ),..., (Q _M ) are turned on in this order, and the blocks (G ₁ ), (G ₂ ),..., (G _M ) are sequentially activated. More specific operations will be described with reference to the time charts of FIGS. 2 (I), (II), (III) and FIG.

When the data signal applied to the block (G ₁ ) is latched by the latch circuit (4), the driving IC (2) changes the line of the driving bus (2B) to “H” according to the data signal.
Set to "L". At the same time, the transistor control circuit (6)
Starts only output 1. The transistor (Q ₁ ) to which the base voltage (Vb ₁ ) is applied turns on. The transistors (Q ₂ ) to (Q _M ) remain OFF. Transistor (Q ₂₎ collector voltage _{(Vc 2) ~ (Vc M} ) of ~ (Q _M) is while being held at a high voltage (Vh), the collector voltage of the transistor (Q ₁₎ (Vc ₁₎ is approximately ground Potential (GND).

As shown in FIG. 2 (I), "H" of the drive bus (2B)
Optical shutter that is connected to the line (11), as indicated by the arrow, the driving element, a shutter, a diode (D ₁ c), the transistor (Q _1), is charged by the formation of ground path, the shutter is turned ON. No optical path is formed in the optical shutter of the line “L”, and the optical shutter remains OFF. At this time, for the other blocks (G ₂ ) to (G _M ), the transistors (Q ₂ ) to
(Q _M ) collector voltage (Vc ₂ ) to (Vc _M ) is high voltage (Vh)
Because it is, the charging path is not formed, also path is blocked in diode _{(D 2 c) ~ (D} 2M) relative to the line of "L" is not formed, the optical shutter (11) all It turns off.

Next, the block (G ₁ ) is cleared in order to shift from driving the block (G ₁ ) to driving the block (G ₂ ). The transistor (Q ₁ ) is turned off, and at the same time, the outputs of all the driving elements of the driving IC (2) are set to “L”. As shown by the arrow in FIG. 2 (II), a discharge path to ground, a diode, a shutter, and a drive element is formed for the optical shutter (11) in the charged state, and the shutter in the ON state is turned off. I do.

Move on to drive the block (G ₂ ). When the data signal for the block (G ₂ ) is established in the latch circuit (4), the drive bus (2B) becomes “H” and “L” in accordance with the data signal. The transistor control circuit (6) turns on the output 2 and turns on the transistor (Q ₂ ). As shown in FIG. 2 (III), a diode (D ₂ c), a transistor (Q ₂ ),
A charging path via the ground is formed, and only the optical shutter connected to the "H" line is turned on by charging. Clear blocks (G _2), similarly to the block (G _1), the transistor by (Q ₂₎ deenergizes the OFF to drive IC (2) a diode of the discharge path through the (D ₂₎ It is performed by forming. Hereinafter, blocks (G ₃ ), (G ₄ ),
..., (G _M) control in order to proceed the complete one cycle by the clear block (G _M). This one cycle forms one line of an image in, for example, an optical printer.

Although the configuration and operation of the embodiment are as described above, one characteristic is that no resistance component is provided in either the charging path or the discharging path of the optical shutter as a capacitor. It can be said that the absence of the resistance component improves the response speed, and conversely, the response speed is high, so that block driving can be performed. Furthermore, since there is no resistance component, problems with heat can be greatly reduced, and stable operation of the optical shutter array can be ensured. That is, since PLZT is a ferroelectric material, the dielectric constant and the electro-optic effect have a large temperature dependence.For example, even if the driving voltage is set so that the amount of transmitted light is maximized in a greenhouse, the operating temperature may be reduced. If it changes, the amount of transmitted light also changes. In order to obtain stable operating characteristics, either the operating temperature must be kept constant or the drive voltage must be changed according to the operating temperature. In this embodiment, however, heat generated by the resistance around the optical shutter array is required. Need not be considered, so there is no need to take special measures.

In the above embodiment, the optical shutters are divided into blocks in the order of arrangement of the optical shutters. However, instead of this, M blocks of N optical shutters in the arrangement order may constitute one block. Good (Optical shutter in order from the end, 1,
2, 3,..., M × N, and the numbers are grouped by the remainder after dividing by M). This is preferable because crosstalk can be suppressed to a minimum.

Effects of the Invention As is apparent from the above description, according to the present invention, an electric field is applied to an element of a light shutter element in a block activated by a switching element to which a voltage is applied by a voltage applying means via an individual electrode. Is formed. At this time,
The common electrode of the other block that is not activated is kept at a predetermined potential by the line connected to the common electrode, and the current flow is interrupted by the current control element provided on this line. No electric field is formed on the optical shutter elements in the block regardless of the voltage applied from the individual electrodes. Therefore, it is possible to provide an optical shutter driving device that has a simple configuration and enables high-contrast driving when driving a capacitive load type optical shutter array for each block.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention, and FIG.
(II) and (III) are operation explanatory diagrams, and FIG. 3 is a timing chart. 1 ...... light shutter array, 11 ...... optical shutter, activation control circuit 2 ...... driving IC, 5 ...... block, 6 ...... transistor control circuit, D _1, D _2, ..., D _M ...... discharge , D ₁ c, D ₂ c,…, D _M c…
Q ₁ , Q ₂ …, Q _M … Transistors as switching elements.

Claims (2)

(57) [Claims] An optical shutter array having a plurality of capacitive load type optical shutter elements is divided into a plurality of blocks such that each block includes a plurality of optical shutter elements, and an optical shutter array for driving each block is provided. In the apparatus, a plurality of individual electrodes provided in common to the plurality of blocks and connected to one ends of a plurality of optical shutter elements included in each block, and selectively applying a voltage to the plurality of individual electrodes A voltage application unit, a plurality of common electrodes provided independently for each block, and commonly connected to the other ends of the plurality of optical shutter elements included in each block; and a plurality of common electrodes respectively connected to the plurality of common electrodes. A plurality of switching elements; and control means for sequentially activating the plurality of switching elements. A common electrode of each block is connected to a switch of another block. When the switching element of another block is activated, the common electrode is connected to a line for maintaining the common electrode at a predetermined potential when the switching element is activated. A drive device for an optical shutter array, comprising a current control element for interrupting a flowing current. 2. The driving device for an optical shutter array according to claim 1, wherein said current control element is a diode.