JP7208510B2 - PHASE MODULATION DEVICE AND PHASE MODULATION METHOD - Google Patents

Description

The present invention relates to a phase modulation device and a phase modulation method.

Conventionally, a phase modulation device using LCOS (Liquid Crystal On Silicon) has been proposed as disclosed in Patent Document 1, for example. Paragraph [0015] of Patent Document 1 and the like disclose controlling the voltage applied to each pixel of the LCOS element to phase-modulate the incident light.

JP 2014-56004 A

Devices that handle infrared light must sufficiently modulate long-wavelength light. Therefore, as a means to secure a high modulation factor, it is basically possible to use a liquid crystal material having a high refractive index anisotropy. For example, the applied voltage of is increased. The method of increasing the thickness of the liquid crystal layer has the disadvantage that the orientation of the liquid crystal tends to be disturbed.

On the other hand, in the technique disclosed in the above-mentioned Patent Document 1, since the voltage supplied to each pixel from the drive circuit is limited, the amount of modulation when modulating the phase cannot be increased. If the voltage output from the drive circuit is increased, it is necessary to increase the withstand voltage of the circuit elements, which causes a problem of increased power consumption.

SUMMARY OF THE INVENTION The present invention has been made in order to solve such conventional problems. An object of the present invention is to provide a phase modulation device and a phase modulation method capable of securing a sufficient phase modulation amount even for infrared light by increasing the voltage applied to the liquid crystal without increasing the voltage.

In order to achieve the above object, a phase modulation device according to the present invention is a phase modulation device for reflecting incident light at a desired angle, wherein a plurality of column data lines and a plurality of row scanning lines orthogonal to each other intersect each other. a plurality of pixel circuits and a plurality of reflective pixels provided at positions corresponding to the reflective pixels; wherein the column data line outputs a control voltage to the pixel circuit that varies up to a predetermined maximum voltage, the pixel circuit including a bridge circuit consisting of a plurality of switches and amplifying the control voltage. A charge pump is provided, and when the driving voltage supplied to the liquid crystal is equal to or lower than the maximum voltage, the plurality of switches short-circuit the input terminal and the output terminal of the charge pump to amplify the control voltage. When the driving voltage supplied to the liquid crystal exceeds the maximum voltage, the control voltage is amplified by controlling the short-circuiting and opening of the plurality of switches, and is output to the liquid crystal. A charge pump controller is provided.

Further, the phase modulation method according to the present invention is a phase modulation method for reflecting incident light at a desired angle, and is provided at positions where a plurality of mutually orthogonal column data lines and a plurality of row scanning lines intersect each other. a step of outputting a control voltage that varies within a range up to a predetermined maximum voltage to the plurality of pixel circuits; When the driving voltage supplied to the liquid crystal to be supplied to the liquid crystal is equal to or lower than the maximum voltage, the plurality of control switches included in the bridge circuit of the charge pump are controlled to short-circuit the input terminal and the output terminal, thereby amplifying the control voltage. and if the drive voltage supplied to the liquid crystal exceeds the maximum voltage, the control voltage is amplified by controlling the short-circuiting and opening of the plurality of switches, and the control voltage is amplified to the liquid crystal. and a step of outputting.

According to the present invention, it is possible to set a large amount of phase modulation of reflected light without increasing the control voltage supplied from the column data line to the pixel circuit. As a result, it is possible to suppress the thickening of the liquid crystal layer for securing the phase modulation amount and the disturbance of the liquid crystal alignment due to the thickening of the liquid crystal layer.

FIG. 1 is a plan view showing the configuration of a phase modulation device according to an embodiment of the invention. FIG. 2 is a side sectional view showing the configuration of the phase modulation device according to the embodiment of the present invention. FIG. 3 is a circuit diagram of a phase modulation device according to an embodiment of the invention. FIG. 4 is a circuit diagram showing the configuration of each pixel circuit provided in the phase modulation device according to the embodiment of the invention. FIG. 5 is an explanatory diagram showing the direction of reflected light reflected by the pixel circuit, where sa1 indicates the case when the charge pump is off and sb1 indicates the case when the charge pump is on. FIG. 6(a) shows pixel circuits arranged in a matrix, and FIG. 6(b) is a graph showing drive voltages supplied from each pixel circuit to the liquid crystal. FIG. 7A is a graph showing the relationship between the gradation set in the liquid crystal and the control voltage supplied to the pixel circuit. FIG. 7B is a graph showing the relationship between the gradation set to the liquid crystal and the drive voltage supplied to the liquid crystal. FIG. 8A is a timing chart showing the ON/OFF states of the switches S1 to S4 when the control voltage is not amplified by the charge pump. FIG. 8B is a timing chart showing the ON/OFF states of the switches S1 to S4 when the control voltage is amplified by the charge pump.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of a phase modulation device according to an embodiment of the present invention, and FIG. 2 is a side cross-sectional view. As shown in FIGS. 1 and 2, a phase modulation device 101 according to this embodiment has an LCOS panel structure including a reflective substrate 11, a liquid crystal layer 12, and a counter substrate 13. FIG. Then, the light incident from the counter substrate 13 side (the direction of the arrow Y1 in FIG. 2) is reflected and separated into a plurality of reflected lights having different phases. In the following, the surfaces of the reflecting substrate 11 and the opposing substrate 13 on which light is incident are referred to as "light incident surfaces".

A plurality of reflective pixels made of a metal that reflects light (for example, aluminum) is provided on the light incident surface of the reflective substrate 11, and a pixel circuit is provided for each reflective pixel. A plurality of pixel circuits 21 are arranged in the horizontal direction and the vertical direction, respectively, as will be described later with reference to FIG. Each pixel circuit 21 operates under the control of the control circuit 22 .

The opposing substrate 13 is arranged parallel to the light incident surface side of the reflecting substrate 11 at a constant interval, and is made of a transparent member (for example, a transparent glass material). That is, the counter substrate 13 has a function as a transparent substrate. Furthermore, the counter substrate 13 is provided with a transparent electrode. Therefore, the light incident from the light incident surface side of the opposing substrate 13 passes through the transparent member and the transparent electrode and enters the liquid crystal layer 12 and the reflective substrate 11 .

The liquid crystal layer 12 is arranged in a space sandwiched between the reflective substrate 11 and the opposing substrate 13, and the periphery thereof is sealed with a sealing material 14. As shown in FIG. For the convenience of the following explanation, the liquid crystal layer 12 is considered as a liquid crystal 42 (see FIG. 4 described later) divided on each reflective pixel (that is, each pixel circuit 21). The liquid crystal 42 includes a pixel electrode having light reflectivity (q1 shown in FIG. 4 to be described later, i.e., reflective pixel) and a common electrode (q2 shown in FIG. 4 to be described later, i.e., transparent electrode ) and are filled and sealed. A voltage output from the pixel circuit 21 (hereinafter referred to as "driving voltage") is supplied to the pixel electrode q1, and a preset common electrode voltage is supplied to the common electrode q2.

Therefore, the potential difference between the driving voltage applied by each pixel circuit 21 and the common electrode voltage applied to the common electrode q2 changes the refractive index of the liquid crystal 42 on each reflective pixel with respect to the incident light to the individual liquid crystal. By changing every 42 or every predetermined number of groups, the incident light incident from the light incident surface side of the counter substrate 13 can be reflected in a desired direction.

By changing the refractive index of the liquid crystal 42 on a plurality of continuous reflective pixels stepwise from large to small (or from small to large), the speed of the incident light (advance or delay in phase) will change. Because of the difference, the incident light travels in a curved manner, and reflected light with a certain angle can be obtained.

Next, the configuration of each pixel circuit 21 and the control circuit 22 that controls each pixel circuit 21 will be described with reference to the block diagram shown in FIG. 3 and the circuit diagram shown in FIG. 3, the control circuit 22 includes a plurality of pixel circuits 21 (m columns, n rows) arranged in a matrix, a horizontal scanning circuit 23, a vertical scanning circuit 24, and a charge pump control section 25. ing. Then, the control circuit 22 outputs an electric signal to each pixel circuit 21 to drive each pixel circuit 21 and applies a driving voltage to the liquid crystal 42 from each pixel circuit 21 . Therefore, the refractive index for incident light of the liquid crystal 42 on each reflective pixel is controlled to a desired value.

A plurality of pixel circuits 21 (m ×n) are arranged. The plurality of pixel circuits 21 are all configured identically. Furthermore, control lines (K1 to Kn) are provided in parallel with the row scanning lines (G1 to Gn). The control lines (K1-Kn) are connected to the charge pump controller 25. FIG.

The control lines (K1 to Kn) are wirings for transmitting control signals for switching ON/OFF of the switches S1 to S4 (see FIG. 4) provided in each pixel circuit . As shown in FIG. 4, a plurality of control lines (K1-Kn) are provided (four lines K1-1, K1-2, K1-3, and K1-4 in the figure). 3, the control line K1 is simply shown as one control line.

The column data lines (D1 to Dm) are wirings for supplying analog voltages (hereinafter referred to as “control voltages”) output from the voltage supply line X1 to the respective pixel circuits 21 . The row scanning lines (G1 to Gn) are wirings for outputting row selection signals (scanning signals) to each pixel circuit 21 .

FIG. 4 is a circuit diagram showing a detailed configuration of the pixel circuit 21. As shown in FIG. Here, the configuration of the pixel circuit 21 (referred to as pixel circuit 21a) arranged at the intersection of the column data line D1 and the row scanning line G1 shown in FIG. 3 will be described. As shown in FIG. 4, the pixel circuit 21a includes a transistor Q1, a charge pump 31, and an output capacitor C2.

The transistor Q1 is a switching transistor, and is composed of, for example, an N-channel MOSFET (field effect transistor). One terminal (eg, drain) of the transistor Q1 is connected to the column data line D1, and the other terminal (eg, source) is connected to the input terminal p1 of the charge pump 31. FIG. A control terminal (for example, gate) of the transistor Q1 is connected to the row scanning line G1. Therefore, when the row scanning line G1 is selected and the control voltage is input from the column data line D1, this control voltage is supplied to the input terminal p1 of the charge pump 31. FIG.

The charge pump 31 includes four switches S1 to S4 and a capacitor C1 (first capacitor) for storing charges, amplifies a control voltage supplied to the input terminal p1, and outputs the amplified control voltage to the output terminal p2.

The switch S1 (first switch) and switch S3 (third switch) are connected in series with each other, the end on the switch S1 side is connected to the input terminal p1, and the end on the switch S3 side is connected to the output terminal p2. . Also, the switch S2 (second switch) and the switch S4 (fourth switch) are connected in series with each other, the end on the switch S2 side is connected to the input terminal p1, and the end on the switch S4 side is connected to the ground. .

Furthermore, a capacitor C1 is provided between the connection point of the switches S1 and S3 and the connection point of the switches S2 and S4. That is, one end of the capacitor C1 is connected to the switches S1 and S3, and the other end of the capacitor C1 is connected to the switches S2 and S4. Thus, the four switches S1-S4 and the capacitor C1 form a bridge circuit. That is, the charge pump 31 includes a bridge circuit composed of a plurality of switches S1-S4. By controlling the ON (short circuit) and OFF (open) states of the switches S1 to S4, the control voltage can be amplified. By simultaneously turning on the switches S1 and S3, the input terminal p1 and the output terminal p2 of the charge pump 31 can be short-circuited.

The output terminal p2 is grounded via an output capacitor C2 and is connected to the pixel electrode q1 of the liquid crystal 42 . Further, as described above, the common electrode q2 of the liquid crystal 42 is a transparent electrode provided on transparent glass. A common electrode voltage is applied to the transparent electrode.

Further, the switch S1 is connected to the control line K1-1, the switch S2 is connected to the control line K1-2, the switch S3 is connected to the control line K1-3, and the switch S4 is connected to the control line K1-4. is connected. The on/off of the switches S1 to S4 are controlled by control signals supplied from the control lines K1-1, K1-2, K1-1, and K1-2.

By outputting control signals for turning on the switches S1 and S3 from the control lines K1-1 and K1-3, the switches S1 and S3 are turned on at the same time, so that the operation of the charge pump 31 is stopped. , the control voltage supplied from the column data line can be supplied to the pixel electrode q1 and thus to the liquid crystal 42. FIG. That is, the control lines K1-1 and K1-2 function as drive lines for switching the charge pump 31 on (short circuit) and off (open). The switches S1 and S3 also function as short-circuit switches that short-circuit the input terminal p1 and the output terminal p2 of the charge pump 31 .

The liquid crystal 42 is driven according to the potential difference between the drive voltage applied to the pixel electrode q1 from the pixel circuit 21 and the common electrode applied to the common electrode q2. Therefore, the incident light incident on the liquid crystal 42 is phase-modulated according to the potential difference and reflected.

FIG. 5 is an explanatory diagram schematically showing angles of incident light incident on the pixel circuit 21 and reflected light reflected by the reflective pixel 20 corresponding to the pixel circuit 21 . In FIG. 5, symbol st indicates incident light incident from a direction orthogonal to the reflective pixel 20 corresponding to each pixel circuit 21, symbol sa1 indicates reflected light reflected at the angle θa by the reflective pixel 20, and symbol sb1. indicates reflected light reflected at an angle θb. The same phase plane of the incident light st (a plane normal to the direction of the incident light st) is r1, the phase plane of the reflected light sa1 is ra1, and the same phase plane of the reflected light sb1 is rb1.

As shown in FIG. 5, incident light st is applied from a direction substantially perpendicular to the reflective pixel 20 and enters the liquid crystal 42 . Further, the refractive index of the liquid crystal 42 changes according to the drive voltage applied to the liquid crystal 42 by the pixel circuit 21 . For example, when the maximum drive voltage in the conventional art is the voltage Va, the reflection angle of the reflected light sa1 obtained when the voltage is changed stepwise from the minimum voltage Vmin to the voltage Va in the continuous pixel circuits 21 is θa On the other hand, when the charge pump 31 is driven, the maximum driving voltage becomes Vb (Vb>Va), and reflected light sb1 reflected at a larger reflection angle θb is obtained.

At this time, although Vmin is applied, the liquid crystal on the pixel has a large refractive index nmax, and the liquid crystal on the pixel to which the maximum voltage Va is applied changes to a small refractive index na. Since the light incident on the liquid crystal with the refractive index na travels faster than the light incident on the liquid crystal with the refractive index nmax, the reflected light is emitted at an angle θa. On the other hand, since the liquid crystal on the pixel to which the voltage Vb is applied has a refractive index nb smaller than na, the incident light travels even faster. Therefore, the reflected light is emitted at a larger angle θb.

Returning to FIG. 3, the horizontal scanning circuit 23 provided in the control circuit 22 includes a shift register circuit 26 and a switch circuit 27 including switches SW1 to SWm.

The shift register circuit 26 inputs a horizontal synchronization signal (HST) and horizontal scanning clock signals (HCK1, HCK2). The shift register circuit 26 sequentially shifts the clock signal based on the horizontal synchronizing signal and the clock signal for horizontal scanning, thereby outputting switching signals (which are referred to as "SD1 to SDm") to the switch circuit 27. It is generated in a cycle of one horizontal scanning period.

The switch circuit 27 includes m switches SW1 to SWm for switching ON/OFF of each column data line (D1 to Dm). The switches SW1 to SWm are controlled to be on or off based on switching signals (SD1 to SDm) output from the shift register circuit . The switches SW1 to SWm are provided corresponding to the column data lines (D1 to Dm), and sequentially input the control voltage "d" corresponding to each column data line.

The switches SW1 to SWm selectively apply control voltages corresponding to the respective column data lines (D1 to Dm) to the column data lines. For example, the switch SW1 is turned on when the switching signal SD1 is at high level, selects a control voltage corresponding to the column data line D1, and outputs the selected control voltage to the column data line D1.

The control voltage "d" supplied from the voltage supply line X1 to each column data line (D1 to Dm) is an analog voltage from "0" (minimum voltage) to "VLC" (maximum voltage). In this embodiment, a double voltage (2*VLC) that is twice the maximum voltage VLC is set, and k gradations ( However, k is an integer of 3 or more). By switching between driving and stopping the charge pump 31, the control voltage (voltage in the range of 0 to VLC) supplied from the column data line is changed to the voltage of the k gradation (voltage in the range of 0 to 2*VLC). voltage).

A detailed description will be given below with reference to FIG. 7A. FIG. 7A is a graph in which the horizontal axis indicates the above-mentioned k gradation (5 gradations in this example), and the vertical axis indicates the control voltage supplied from the voltage supply line X1 to the pixel circuit 21 via the column data line. be.

Graph R1 shown in FIG. 7A shows characteristics when the driving voltage supplied to the liquid crystal 42 is equal to or lower than the maximum voltage VLC, and graph R2 shows characteristics when the driving voltage supplied to the liquid crystal 42 is equal to or higher than the maximum voltage VLC. showing. Although the graphs R1 and R2 show an example in which the voltage changes linearly, the present invention is not limited to this, and any change that monotonously increases within the range of 0 to VLC is acceptable.

For example, when the number of gradations of the drive voltage supplied to the liquid crystal 42 is set to "5" (that is, k=5), the double voltage (2*VLC) is equally divided into 5 to give gradations 1 to 5. Set gradation 5. Therefore, the voltage doubled (2*VLC) is divided into 5 equal parts, the voltage of (1/5)*2*VLC as gradation 1, the voltage of (2/5)*2*VLC as gradation 2, and the gradation A voltage of (3/5)*2*VLC for 3, a voltage of (4/5)*2*VLC for gradation 4, and a voltage of (5/5)*2*VLC for gradation 5 are used as control voltages. It suffices to supply it to the pixel circuit 21 .

However, since the control voltage corresponding to the gradation 3 to gradation 5 exceeds the maximum voltage VLC, the control voltage corresponding to the gradation 3 to gradation 5 is applied to the pixel circuit from the voltage supply line X1 shown in FIG. 21 cannot be supplied. In the present embodiment, for gradations 3 to 5, half the control voltage is output, and then the charge pump 31 amplifies the voltage by a factor of two. That is, (3/5)*VLC for gradation 3, (4/5)*VLC for gradation 4, and VLC for gradation 5 are output. 31 amplifies it twice and outputs it to the liquid crystal 42 .

That is, when the control voltage for obtaining the desired gradation is equal to or lower than the maximum voltage VLC (in the case of gradations 1 and 2), as shown in the graph R1 in FIG. 7A, the control voltage is driven without being amplified. It is output to the liquid crystal 42 as a voltage.

On the other hand, when the voltage for obtaining the desired gradation exceeds the maximum voltage VLC (in the case of gradations 3, 4, and 5), as shown in the graph R2 in FIG. 7A, half this voltage is controlled. A desired drive voltage is obtained by supplying the voltage to the pixel circuit 21 as a voltage and then amplifying it twice by the charge pump 31 . Therefore, the slope of graph R2 is half the slope of graph R1.

That is, the charge pump control unit 25 sets the voltage corresponding to an arbitrary gradation to the maximum voltage ( VLC) In the following cases, the control voltage is output to the liquid crystal 42 without being amplified. On the other hand, when the voltage corresponding to an arbitrary grayscale among a plurality of grayscales exceeds the maximum voltage (VLC), the charge pump 31 is controlled to amplify the control voltage and output it to the liquid crystal 42 .

In this way, by controlling the on/off of each of the switches SW1 to SWm provided in the switch circuit 27 and controlling the driving of the charge pump 31, the pixel circuit 21 has k gradations (5 gradations in the above example). It is possible to generate a drive signal corresponding to the gradation) and supply it to the liquid crystal 42 . That is, as shown in the graph R3 of FIG. 7B, it is possible to output to the liquid crystal 42 drive voltages of gradations 1 to 5 obtained by equally dividing the voltage doubled (2*VLC) into five. .

Returning to FIG. 3, the vertical scanning circuit 24 is connected to row scanning lines (G1 to Gn). The vertical scanning circuit 24 inputs a vertical synchronization signal (VST) and vertical scanning clock signals (VCK1, VCK2). The vertical scanning circuit 24 sequentially supplies row selection signals (scanning signals), for example, from the row scanning line G1 to the row scanning line Gn at a cycle of one horizontal scanning period based on the vertical synchronization signal and the clock signal for vertical scanning. .

The charge pump control unit 25 outputs control signals to control lines (K1-1, K1-3) for controlling ON/OFF of the switches S1 and S3 shown in FIG. Control is performed to short-circuit the terminal p2. Specifically, an arbitrary gradation ( For example, when the voltage corresponding to gradation 1) is lower than the maximum voltage (VLC), a control signal is output to the control lines K1-1 and K1-3 to simultaneously turn on the switches S1 and S3. Further, when the voltage corresponding to an arbitrary gradation (for example, gradation 3) among a plurality of gradations exceeds the maximum voltage (VLC), the switches S1 and S3 are not turned on at the same time, and a normal charge pump is applied. 31 outputs a control signal according to the operation. The operation of the charge pump 31 will be described in detail below.

When the charge pump control unit 25 drives the charge pump 31, the control signal for controlling the on/off of the switches S1 to S4 shown in FIG. -3, K1-4). Specifically, when the control voltage is supplied from the column data line D1, the switches S1 and S4 are first turned on, and the switches S2 and S3 are turned off. Thereby, the control voltage supplied from the column data line D1 is stored in the capacitor C1.

After a predetermined time has elapsed, the switches S1 and S4 are turned off and the switches S2 and S3 are turned on. As a result, the control voltage supplied from the column data line D1 and the voltage accumulated in the capacitor C1 are added, and the added voltage is accumulated in the output capacitor C2. Therefore, a voltage that is twice the control voltage supplied from the column data line D1 is accumulated in the output capacitor C2 and output to the pixel electrode q1.

Then, in the phase modulation device 101 according to the present embodiment, blocks made up of some of the (n×m) pixel circuits 21 shown in FIG. 3 are set. For example, as shown in FIG. 6A, a block composed of (5 rows×6 columns) pixel circuits 21 is set. In FIG. 6A, the suffix "-nm" is added to specify the row (n) and column (m) of each pixel circuit 21, respectively. Accordingly, the pixel circuit of row 1 and column 1 shown in FIG. 6A is 21-11, and the pixel circuit of row 5 and column 6 is 21-56.

In FIG. 6A, the same voltage is supplied to the six pixel circuits 21-11 to 21-16 in the same row. For example, the pixel circuits 21-11 to 21-16 are supplied with control voltages corresponding to gradation 1 among gradations 1 to 5. FIG. Also, the gradation is set so that the gradation gradually increases from top to bottom in the vertical direction, and a control voltage corresponding to gradation 5 is supplied to the pixel circuits 21-51 to 21-56 in the bottom row.

Specifically, as shown in FIG. 6B, in each pixel circuit 21-11 to 21-51 arranged in the vertical direction, the driving voltage supplied to each liquid crystal 42 corresponds to the gradation 1 to gradation 5. Set to change step by step. Accordingly, six pixel circuits 21 are grouped into one group, and the reflectance can be changed in five ways, and thus it is possible to obtain reflected light phase-modulated in five ways.

[Explanation of operation of the present embodiment]
Next, the operation of the phase modulation device 101 according to this embodiment configured as described above will be described with reference to the graphs shown in FIGS. 7A and 7B and the timing chart shown in FIG. FIG. 7B is a graph showing the relationship between the gradation set in five stages and the driving voltage supplied to the liquid crystal 42. In FIG. In the following, an example in which each pixel circuit 21 is arranged in a matrix of 6×5 and reflective pixels corresponding to each pixel circuit 21 as shown in FIG. 6A will be described.

The horizontal scanning circuit 23 shown in FIG. 3 controls the ON/OFF of each switch SW1 to SWm (here, m=6) provided in the switch circuit 27 to control the control voltage supplied from the voltage supply line X1. to the desired column data lines.

Further, by driving the vertical scanning circuit 24, the scanning line corresponding to the desired pixel circuit 21 is selected from the row scanning lines (G1 to Gn) (here, n=5). As a result, the desired pixel circuit 21 can be supplied with the control voltage.

For example, the voltage "0 to 2*VLC" in the range from "0" to twice the maximum voltage is divided into five gradations (that is, k = 1 to 5), and the 1 A voltage of gradation 1 "(1/5)*2*VLC" is supplied to the pixel circuits 21-11 to 21-16 of the row, and a voltage of gradation 2 is supplied to the pixel circuits 21-21 to 21-26 of the second row. of voltage "(2/5)*2*VLC".

Furthermore, the voltage of gradation 3 is supplied to the pixel circuits 21-31 to 21-36 of the third row. In this case, the voltage supplied to the pixel circuit is "(3/5)*2*VLC", which exceeds the maximum voltage VLC. Therefore, as shown in FIG. 7A, half the above voltage "(3/5)*VLC" is output as the control voltage, and the charge pump 31 further amplifies this voltage by two times to obtain "( 3/5)*2*VLC" is generated to be the voltage of gradation 3.

Similarly, for the pixel circuits 21-41 to 21-46 in the fourth row and the pixel circuits 21-51 to 21-56 in the fifth row, half voltages are output as control voltages. Voltages of gradation 4 and gradation 5 are generated by amplifying by a factor of two.

Next, the operation of the pixel circuit 21 will be described with reference to the timing chart shown in FIG. As an example, the operation of the charge pump 31 in the pixel circuit 21a connected to the column data line D1 and the row scanning line G1 will be described.

When the pixel circuit 21a is set to the gradation 1 described above, the charge pump 31 is not operated. In this case, the charge pump control unit 25 turns on the switches S1 and S3 at the same time, as shown from time t0 to t1 in FIG. Also, the switches S2 and S4 are turned off. As a result, the input terminal p1 and the output terminal p2 of the charge pump 31 are short-circuited via the switches S1 and S3, so that the control voltage supplied from the column data line D1 is not amplified by the charge pump 31 and is applied to the liquid crystal. 42. Therefore, a voltage of "(1/5)*2*VLC" can be supplied to the liquid crystal as indicated by symbol z1 in FIG. 7B.

Similarly, when the pixel circuit 21a is set to gradation 2, the charge pump 31 is not operated, and the control voltage supplied from the column data line D1 is not amplified as indicated by symbol z2 in FIG. 7B. Output. As a result, a voltage of "(2/5)*2*VLC" can be applied to the liquid crystal.

When the pixel circuit 21 is set to gradation 3, a voltage "(2/5)*VLC", which is half the voltage "(2/5)*2*VLC" corresponding to gradation 3, is applied to the column data line D1. ” as the control voltage. Furthermore, this control voltage is doubled by the charge pump 31 .

Specifically, when setting the pixel circuit 21a to gradations 1 and 2, as shown in (a) to (d) of FIG. It is controlled to turn off, S3 on, and S4 off.
On the other hand, when setting the pixel circuit 21a to gradation 3 to 5, as shown in (a) and (d) of FIG. S2 and S3 are turned off. As a result, the control voltage "(3/5)*VLC" is stored in the capacitor C1.

After that, the switches S2 and S3 are turned on and the switches S1 and S4 are turned off during the period from time t12 to t13. As a result, the voltage "(3/5)*2*VLC", which is twice the control voltage, is accumulated in the output capacitor C2. Therefore, as indicated by symbol z3 in FIG. 7B, the driving voltage "(3/5)*2*VLC" of gradation 3 can be supplied to the liquid crystal 42 .

Also, when the pixel circuit 21a is set to the gradation 4, the charge pump 31 is similarly operated to drive the liquid crystal to "(4/5)*2*VLC" as indicated by symbol z4 in FIG. 7B. voltage can be supplied.

Further, when the pixel circuit 21a is set to the gradation level 5, the charge pump 31 is operated in the same manner to supply the driving voltage of "2*VLC" to the liquid crystal as indicated by symbol z5 in FIG. 7B. can.

[Description of effects of the present embodiment]
Thus, in the phase modulation device 101 according to this embodiment, each pixel circuit 21 is provided with the charge pump 31 . When setting an arbitrary gradation among a plurality of gradations preset in the range from "0" to twice the maximum voltage (2*VLC), When the voltage is lower than the maximum voltage (VLC), the control voltage supplied from the column data line to the pixel circuit 21 is output to the liquid crystal 42 without being amplified.

Further, when the voltage corresponding to an arbitrary gradation out of a plurality of gradations exceeds the maximum voltage (VLC), the control voltage is amplified by the charge pump 31 and controlled to be output to the liquid crystal 42 .

Therefore, when the maximum control voltage supplied to the pixel circuit 21 from the column data line is the maximum voltage (VLC), the voltage for driving the liquid crystal 42 is within the range of the voltage (2*VLC) which is twice the maximum voltage (VLC). It becomes possible to set the drive voltage. Therefore, the magnitude of the refractive index of the liquid crystal 42 can be changed in a wider range, an increase in the thickness of the liquid crystal layer 12 can be suppressed, and the precision of phase modulation can be improved.

Also, the control voltage supplied from the column data line is supplied to the liquid crystal 42 by simultaneously turning on the switches S1 and S3 provided in the charge pump 31 . Therefore, it is not necessary to separately provide a wiring for connecting between the column data line and the pixel electrode q1, and the circuit configuration can be simplified.

Furthermore, since the gradation can be set in a wide voltage range without increasing the maximum voltage VLC of the control voltage supplied to the pixel circuit 21, there is no need to increase the breakdown voltage of each component constituting the control circuit 22, and the device can be made smaller. , it becomes possible to achieve weight reduction.

Further, since the voltage range for setting the drive voltage of the liquid crystal 42 is set to a voltage that is twice the maximum voltage VLC, a desired drive voltage can be obtained by a simple process of doubling the control voltage. can be obtained, and the circuit configuration can be simplified.

Further, in this embodiment, the refractive index of the liquid crystal 42 is set to change in one of the directions orthogonal to each other, ie, the column direction and the row direction shown in FIG. 3, and changes in the other direction. , drive lines (that is, control lines K1-1 and K1-3) for switching on and off of the charge pump. Therefore, it is possible to prevent the alignment of the liquid crystal from being disturbed due to the change in the refractive index.

In this embodiment, the drive voltage range is set to twice the maximum voltage (2*VLC), but the present invention is not limited to this, as long as it is greater than the maximum voltage VLC.

Although embodiments of the present invention have been described above, the statements and drawings forming part of this disclosure should not be construed as limiting the present invention. Various alternative embodiments, implementations and operational techniques will become apparent to those skilled in the art from this disclosure.

Reference Signs List 11 reflective substrate 12 liquid crystal layer 13 counter substrate 14 sealing material 20 reflective pixels 21, 21a, 21' pixel circuit 22 control circuit 23 horizontal scanning circuit 24 vertical scanning circuit 25 charge pump control section 26 shift register circuit 27 switch circuit 31 charge pump 42 Liquid crystal q1 Pixel electrode q2 Common electrode p1 Input terminal p2 Output terminal D1 to Dm Column data lines G1 to Gn Row scanning lines K1 to Kn Control lines K1-1, K1-2, K1-3, K1-4 Control line S1 First switch (bridge circuit)
S2 Second switch (bridge circuit)
S3 third switch (bridge circuit)
S4 fourth switch (bridge circuit)

Claims (6)

A phase modulation device that reflects incident light at a desired angle,
a plurality of pixel circuits provided at positions where a plurality of column data lines and a plurality of row scanning lines that are orthogonal to each other intersect, and a plurality of reflective pixels;
a liquid crystal provided corresponding to the reflective pixel and having a refractive index with respect to incident light that changes according to a driving voltage supplied from the pixel circuit;
the column data line outputs a control voltage to the pixel circuit that varies up to a predetermined maximum voltage;
the pixel circuit includes a bridge circuit consisting of a plurality of switches and has a charge pump that amplifies the control voltage;
Further, when the driving voltage supplied to the liquid crystal is equal to or lower than the maximum voltage, the plurality of switches are controlled to short-circuit the input terminal and the output terminal of the charge pump, and the control voltage is not amplified. When the drive voltage output to the liquid crystal and supplied to the liquid crystal exceeds the maximum voltage, the plurality of switches are short-circuited and opened to amplify the control voltage and output the control voltage to the liquid crystal. A phase modulation device comprising: the pixel circuit includes an output capacitor that stores a voltage supplied to the liquid crystal, one end of the output capacitor being connected to the output terminal;
The bridge circuit is
a first capacitor that stores electric charge;
a first switch provided between one end of the first capacitor and an input terminal to which the control voltage is supplied;
a second switch provided between the other end of the first capacitor and the input terminal;
a third switch provided between the one end of the first capacitor and the output terminal;
a fourth switch provided between the other end of the first capacitor and the other end of the output capacitor;
2. The phase modulation device according to claim 1, wherein the charge pump control section simultaneously short-circuits the first switch and the third switch to short-circuit the input terminal and the output terminal. After short-circuiting the input terminal and the output terminal, the charge pump control section short-circuits the first and fourth switches, opens the second and third switches, and then closes the second and third switches. 3. The phase modulation device according to claim 2, wherein control is performed to short-circuit and open the first and fourth switches, and the voltage accumulated in the output capacitor is output from the output terminal. setting the refractive index of the liquid crystal to change in one of the mutually orthogonal directions, and arranging a driving line for switching between shorting and opening of the charge pump in the other direction; The phase modulation device according to any one of claims 1 to 3, characterized by: 5. The phase modulation device according to any one of claims 1 to 4, wherein the maximum voltage of the driving voltage supplied to the liquid crystal is set to twice the maximum voltage. A phase modulation method for reflecting incident light at a desired angle,
a step of outputting a control voltage that varies within a range up to a predetermined maximum voltage to a plurality of pixel circuits provided at intersections of a plurality of column data lines and a plurality of row scanning lines that are orthogonal to each other;
In each of the pixel circuits , when the driving voltage supplied to the liquid crystal whose refractive index for incident light changes according to the input driving voltage is equal to or lower than the maximum voltage, the plurality of switches included in the bridge circuit of the charge pump are turned off. a step of controlling to short-circuit an input terminal and an output terminal, and outputting the control voltage to the liquid crystal without amplifying it;
when the driving voltage supplied to the liquid crystal exceeds the maximum voltage, controlling the short-circuiting and opening of the plurality of switches to amplify the control voltage and output it to the liquid crystal;
A phase modulation method, comprising:

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