JP2020160172A - Phase modulator, and phase modulation method - Google Patents

Abstract

To provide a phase modulator capable of increasing a modulation amount of a phase without increasing voltage applied from a column data line to a pixel circuit.SOLUTION: A phase modulator that causes incident light to be reflected and sorts it into a plurality of reflected light beams whose phases are different from each other comprises: a reflection substrate 11 having a plurality of pixel circuits 21; a liquid crystal layer 12 where a plurality of liquid crystals 42, each of which has a reflection angle changed by voltage applied by each of the pixel circuits 21, are arranged; and a control circuit 22 for controlling the pixel circuits 21. Each of the pixel circuits 21 has a charge pump 31 for amplifying a control voltage. In a case where voltage corresponding to an arbitrary gradation of a plurality of preset gradations is a maximum voltage VLC or less, the control voltage is not amplified. In a case where the voltage exceeds the maximum voltage VLC, the control voltage is amplified by the charge pump 31. Further, an output voltage of the charge pump 31 is amplified by a source follower Q4, where a well region and a source are connected, and is applied to the liquid crystal 42.SELECTED DRAWING: Figure 3

Description

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

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

Japanese Unexamined Patent Publication No. 2014-56004

In a device that handles light in the infrared region, long wavelength light must be sufficiently modulated. Therefore, as a means for ensuring a high modulation factor, a liquid crystal material having a high refractive index anisotropy is basically used, but in addition, firstly, the liquid crystal layer is thickened, and secondly, to the liquid crystal. It is possible to increase the applied voltage of. The method of thickening the liquid crystal layer has a demerit that the orientation of the liquid crystal is easily disturbed.

On the other hand, in the technique disclosed in Patent Document 1 described above, since the voltage supplied to each pixel from the drive circuit is limited, it is not possible to increase the amount of modulation when the phase is modulated. When the voltage output from the drive circuit is increased, it is necessary to increase the withstand voltage of the circuit element, and further, there arises a problem that the power consumption is increased.

The present invention has been made to solve such a conventional problem, and an object of the present invention is to suppress an increase in the thickness of the liquid crystal layer and to supply a voltage supplied from a column data line to a pixel circuit. It is an object of the present invention to provide a phase modulation device and a phase modulation method capable of ensuring a sufficient phase modulation amount even in infrared light by increasing the voltage applied to the liquid crystal without increasing the voltage.

In order to achieve the above object, the phase modulator according to the present invention is a phase modulator that reflects incident light at a desired angle, and a plurality of column data lines orthogonal to each other and a plurality of row scanning lines intersect each other. A plurality of pixel circuits provided at the positions to be provided, a plurality of reflection pixels, a liquid crystal provided corresponding to the reflection pixels, and a liquid crystal whose refraction rate with respect to incident light changes depending on a drive voltage supplied from the pixel circuit, and the above. The column data line includes a control circuit for controlling the pixel circuit, the column data line outputs a control voltage changing in a range up to a predetermined maximum voltage to the pixel circuit, and the pixel circuit is a charge for amplifying the control voltage. It includes a pump and a source follower that amplifies the control voltage or the control voltage amplified by the charge pump, and further, the control circuit provides the control circuit when the drive voltage supplied to the liquid crystal is equal to or less than the maximum voltage. When the drive voltage supplied to the liquid crystal exceeds the maximum voltage, the control voltage is used as an output voltage, and the voltage amplified by the charge pump is used as an output voltage to control the supply to the liquid crystal. It is characterized in that the well of the source follower and the source are connected to each other, and the well potential and the source potential are the same potential.

Further, the phase modulation device according to another invention is a phase modulation device that reflects incident light at a desired angle, and is provided at a position where a plurality of column data lines orthogonal to each other and a plurality of row scanning lines intersect each other. Controls the plurality of pixel circuits, a plurality of reflection pixels, a liquid crystal provided corresponding to the reflection pixels, and a liquid crystal whose refraction rate with respect to incident light changes depending on a drive voltage supplied from the pixel circuit, and the pixel circuit. The column data line outputs a control voltage that changes in a range up to a predetermined maximum voltage to the pixel circuit, and the pixel circuit outputs a control voltage output from the column data line. A source follower for amplification and a charge pump for amplifying the output voltage of the source follower are provided, and the control circuit further comprises the source follower when the drive voltage supplied to the liquid crystal is equal to or less than the maximum voltage. When the drive voltage supplied to the liquid crystal exceeds the maximum voltage, the charge pump control unit that controls to supply the liquid crystal with the voltage amplified by the charge pump as the output voltage is used. It is characterized in that the well of the source follower and the source are connected, and the well potential and the source potential are the same potential.

The phase modulation method according to the present invention is a phase modulation method that reflects incident light at a desired angle, and is provided at a position where a plurality of column data lines orthogonal to each other and a plurality of row scanning lines intersect each other. A step of outputting a control voltage that changes in a range up to a predetermined maximum voltage to the pixel circuit of the above, and a liquid crystal that is provided corresponding to each of the pixel circuits and whose refractive index with respect to incident light changes according to the input drive voltage. When the drive voltage supplied to is equal to or lower than the maximum voltage, the step of amplifying the voltage at which the control voltage is not amplified by the charge pump and outputting it to the supply point by the source follower and the drive voltage supplied to the liquid crystal However, when the maximum voltage is exceeded, the voltage obtained by amplifying the control voltage by the charge pump is amplified by the source follower and output to the supply point, and the well and source of the source follower are provided. Is connected, and the well potential and the source potential are the same potential.

The phase modulation method according to another invention is a phase modulation method that reflects incident light at a desired angle, and is provided at a position where a plurality of column data lines orthogonal to each other and a plurality of row scanning lines intersect each other. A step of outputting a control voltage that changes within a range up to a predetermined maximum voltage and a step of amplifying the control voltage by a source follower are provided and input to the plurality of pixel circuits corresponding to the respective pixel circuits. When the drive voltage supplied to the liquid crystal whose refractive index with respect to the incident light changes according to the drive voltage is equal to or less than the maximum voltage, the output voltage of the source follower is output to the supply point without being amplified by the charge pump. The source includes a step and a step of amplifying the output voltage of the source follower by the charge pump and outputting it to the supply point when the drive voltage supplied to the liquid crystal exceeds the maximum voltage. It is characterized in that the well of the follower and the source are connected, and the well potential and the source potential are the same potential.

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 thicknessing of the liquid crystal layer for securing the phase modulation amount and the disorder of the liquid crystal orientation due to the thickening of the liquid crystal layer.

FIG. 1 is a plan view showing a configuration of a phase modulation device according to an embodiment of the present invention. FIG. 2 is a side sectional view showing a configuration of a phase modulation device according to an embodiment of the present invention. FIG. 3 is a circuit diagram of a phase modulation device according to an embodiment of the present invention. FIG. 4 is a circuit diagram showing a configuration of each pixel circuit provided in the phase modulation device according to the first embodiment of the present invention. FIG. 5A (a) is a circuit diagram when the well of the source follower Q4 is connected to the ground, and FIG. 5A (b) is a graph showing the relationship between Vin and Vout. FIG. 5B (a) is a circuit diagram when the well of the source follower Q4 and the source are connected, and FIG. 5B is a graph showing the relationship between Vin and Vout. FIG. 6 is an explanatory diagram showing the direction of the reflected light reflected by the pixel circuit, where sa1 shows the case where the charge pump is off and sb1 shows the case where the charge pump is on. FIG. 7A is a graph showing each pixel circuit arranged in a matrix, and FIG. 7B is a graph showing a drive voltage supplied to the liquid crystal from each pixel circuit. FIG. 8A is a graph showing the relationship between the gradation set in the liquid crystal and the control voltage supplied to the pixel circuit. FIG. 8B is a graph showing the relationship between the gradation set on the liquid crystal and the drive voltage supplied to the liquid crystal. FIG. 9A shows transistors Q2 and switches S1 to S4, first changeover switch S6, and second changeover provided in each pixel circuit when the charge pump is not operated in the phase modulator according to the first embodiment of the present invention. It is a timing chart which shows the operation of the switch S5. FIG. 9B shows transistors Q2 and switches S1 to S4, first changeover switch S6, and second changeover provided in each pixel circuit when the charge pump is operated in the phase modulator according to the first embodiment of the present invention. It is a timing chart which shows the operation of the switch S5. FIG. 10 is a circuit diagram showing a configuration of each pixel circuit provided in the phase modulation device according to the second embodiment of the present invention. FIG. 11A shows the operation of the transistors Q2, the switches S1 to S4, and the first changeover switch S6 provided in each pixel circuit when the charge pump is not operated in the phase modulation device according to the second embodiment of the present invention. It is a timing chart. FIG. 11B shows the operation of the transistors Q2, the switches S1 to S4, and the first changeover switch S6 provided in each pixel circuit when the charge pump is operated in the phase modulation device according to the second embodiment of the present invention. It is a timing chart.

[Explanation of the first embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of the phase modulation device according to the first embodiment of the present invention, and FIG. 2 is a cross-sectional view in the side direction. As shown in FIGS. 1 and 2, the phase modulation apparatus 101 according to the present embodiment has an LCOS panel structure including a reflection substrate 11, a liquid crystal layer 12, and a facing substrate 13. Then, the light incident from the opposite substrate 13 side (direction of arrow Y1 in FIG. 2) is reflected and separated into a plurality of reflected lights having different phases. In the following, the surface of the reflective substrate 11 and the opposing substrate 13 on the side where the light is incident is referred to as a “light incident surface”.

A plurality of reflective pixels formed of a metal that reflects light (for example, aluminum) are 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 in FIG. Each pixel circuit 21 operates under the control of the control circuit 22.

The facing substrate 13 is arranged in parallel with the light incident surface side of the reflective substrate 11 at regular intervals, and is formed of a transparent member (for example, a transparent glass material). That is, the opposed substrate 13 has a function as a transparent substrate. Further, the facing substrate 13 is provided with a transparent electrode. Therefore, the light incident from the light incident surface side of the opposed substrate 13 passes through the transparent member and the transparent electrode and is incident on 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. Further, for convenience of the following description, the liquid crystal layer 12 is considered to be a liquid crystal 42 (see FIG. 4 described later) divided on each reflective pixel (that is, each pixel circuit 21). The liquid crystal 42 has a pixel electrode having light reflectivity (q1 shown in FIG. 4 described later, that is, a reflective pixel) and a common electrode (q2 shown in FIG. 4 described later, that is, a transparent electrode) arranged so as to be separated from the pixel electrode. ) Is filled and sealed. Then, 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 refractive index of the liquid crystal 42 on each reflective pixel with respect to the incident light is determined by the potential difference between the drive voltage applied by each pixel circuit 21 and the common electrode voltage applied to the common electrode q2. The incident light incident from the light incident surface side of the opposing substrate 13 can be reflected in a desired direction by changing the light incident area or a predetermined number of groups.
By gradually changing the refractive index of the liquid crystal 42 on a plurality of continuous reflection pixels from large to small (or small to large), the speed of incident light (phase advance or lag) incident therein can be changed. Due to the difference, the incident light bends and travels, and reflected light at 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. In FIG. 3, the control circuit 22 includes a plurality of (m columns, n rows) pixel circuits 21 arranged in a matrix, a horizontal scanning circuit 23, a vertical scanning circuit 24, and a switch control unit 25 (charge pump control unit). , Changeover switch control unit). Then, the control circuit 22 outputs an electric signal to each pixel circuit 21 to drive each pixel circuit 21, and applies a drive voltage to the liquid crystal 42 from each pixel circuit 21. Therefore, the refractive index of the liquid crystal 42 on each reflective pixel with respect to the incident light is controlled to be a desired value.

A plurality of pixel circuits 21 are formed in a matrix (m) at each intersection (intersection position) of m column data lines (D1 to Dm) orthogonal to each other and n row scanning lines (G1 to Gn). × n) are arranged. The plurality of pixel circuits 21 are all configured in the same manner. Further, a drive line (L1 to Ln) and a control line (K1 to Kn) are provided in parallel with the row scanning lines (G1 to Gn). The drive lines (L1 to Ln) and control lines (K1 to Kn) are connected to the switch control unit 25.

Further, short-circuit lines (J1 to Jn) are provided in parallel with the row scanning lines (G1 to Gn). As shown in FIG. 4, the short-circuit lines (J1 to Jn) are provided with first changeover switches (S6, S6'in FIG. 4) for switching between short-circuiting and opening between pixel circuits 21 adjacent to each other.
In the example shown in FIG. 3, the refractive index of light is controlled to change in the vertical direction (vertical direction in the figure). Therefore, short-circuit lines (J1 to Jn) are provided in the lateral direction (left-right direction in the figure), which is a direction orthogonal to this direction.

The drive lines (L1 to Ln) are wirings for transmitting control signals for switching on / off of the transistor Q2 (short-circuit switch; see FIG. 4) provided in each pixel circuit 21. Further, the control lines (K1 to Kn) are control signals for switching on / off of switches S1 to S4 (see FIG. 4) provided in each pixel circuit 21, and the above-mentioned first changeover switch S6 and the first changeover switch S6. 2 This is a wiring for transmitting a control signal for switching on / off of the changeover switch S5 (see FIG. 4). A plurality of control lines (K1 to Kn) are provided as shown in FIG. 4 (4 lines of K1-1, K1-2, K1-3, and K1-4 in the figure), but in FIG. It is shown simply by one control line K1.

As shown in FIG. 4, the control line K1-1 outputs a control signal for controlling the on / off of the switches S1 and S4 of the charge pump 31. The control line K1-2 outputs a control signal for controlling the on / off of the switches S2 and S3 of the charge pump 31. The control line K1-3 outputs a control signal for controlling the on / off of the first changeover switches S6 and S6'. Note that S6'is a first changeover switch provided in an adjacent pixel circuit. The control line K1-4 outputs a control signal for controlling the on / off of the second changeover switch S5.
The column data lines (D1 to Dm) are wirings for supplying an analog voltage (hereinafter, referred to as “control voltage”) output from the voltage supply line X1 to each pixel circuit 21. The row scanning lines (G1 to Gn) are wirings for outputting a row selection signal (scanning signal) to each pixel circuit 21.

FIG. 4 is a circuit diagram showing a detailed configuration of the pixel circuit 21. Here, the configuration of the pixel circuit 21 (referred to as the 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 transistors Q1 and Q2, a charge pump 31, and an output capacitor C2. Further, it includes a source follower Q4 (first source follower), a load transistor Q5, a second changeover switch S5, an additional capacitor C3, and a first changeover switch S6.

The transistor Q1 is a switching transistor, and is composed of, for example, an N-channel MOSFET (field effect transistor). One terminal (for example, drain) of the transistor Q1 is connected to the column data line D1, and the other terminal (for example, source) is connected to the input terminal p1 of the charge pump 31. Further, the control terminal (for example, the 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.

The transistor Q2 is also a switching transistor like the transistor Q1 described above, and is composed of, for example, an N-channel MOSFET (field effect transistor). One terminal (for example, drain) of the transistor Q2 is connected to the input terminal p1 of the charge pump 31, and the other terminal (for example, the source) is connected to the output terminal p2 of the charge pump 31.

Further, the control terminal (for example, a gate) is connected to the drive line L1. Therefore, when a voltage of "H" level is supplied to the drive line L1, the transistor Q2 is turned on and the input terminal p1 and the output terminal p2 of the charge pump 31 are short-circuited. That is, the function of the charge pump 31 can be stopped. On the contrary, when the drive line L1 is supplied with the "L" level voltage, the transistor Q2 is turned off. Therefore, the input terminal p1 and the output terminal p2 of the charge pump 31 are opened, and the charge pump 31 can be operated.

That is, the transistor Q2 has a function as a short-circuit switch that short-circuits the input terminal p1 to which the control voltage is supplied to the charge pump 31 and the output terminal p2 to output the voltage (drive voltage) from the charge pump 31 to the liquid crystal 42. ing. Then, when the drive voltage for setting the liquid crystal 42 to a desired refractive index is equal to or less than the maximum voltage VLC (maximum voltage) supplied from the column data line D1, the switch control unit 25 (see FIG. 3) is controlled. Short-circuits the transistor Q2. That is, the control voltage is not amplified by the charge pump 31. When the drive voltage exceeds the maximum voltage VLC, the transistor Q2 is opened. That is, the control voltage can be amplified by the charge pump 31.

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

The switch S1 (first switch) and the 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. .. Further, 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. ..

Further, a capacitor C1 (first capacitor) is provided between the connection point between the switches S1 and S3 and the connection point between 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.

The output terminal p2 is connected to the ground via the output capacitor C2, and further connected to the gate of the source follower Q4. Further, as described above, the common electrode q2 of the liquid crystal 42 is a transparent electrode provided on the transparent glass. A common electrode voltage is applied to the transparent electrode.

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

Further, the pixel circuit 21 is provided with a series connection circuit of the source follower Q4 and the load transistor Q5, the output terminal p2 of the charge pump 31 is connected to the gate of the source follower Q4, and the source of the load transistor Q5 is grounded. It is connected to the.

The load transistor Q5 is controlled to be turned on when a voltage (control voltage supplied via the transistor Q1 or output voltage of the charge pump 31) is supplied to the gate of the source follower Q4. The control line for controlling the load transistor Q5 is not shown.

The connection point between the source follower Q4 and the load transistor Q5 (the output point q3 of the source follower Q4) is connected to the pixel electrode q1 (supply point) via the second changeover switch S5. Further, the pixel electrode q1 is connected to the ground via the addition capacitor C3 and is connected to the short-circuit line J1. The short-circuit line J1 is provided with a first changeover switch S6 for switching between short-circuiting (on) and opening (off) with the pixel electrodes in the adjacent pixel circuit.

The additional capacitor C3 stores the voltage output from the source follower Q4 via the second changeover switch S5.
Since the source follower Q4, the load transistor Q5, the second changeover switch S5, and the additional capacitor C3 described above are driven by being supplied with a voltage after being amplified by the charge pump 31, a high withstand voltage element is used.

The first changeover switch S6 is turned on and off by a control signal output from the switch control unit 25 via the control line K1-3. The second changeover switch S5 is turned on and off by a control signal output from the switch control unit 25 via the control line K1-4.

As the source follower Q4, MOSFET or NMOS can be used. The well region of the source follower Q4 is separated from the surrounding wells and the source is connected. Therefore, the well potential and the source potential are the same potential. With such a configuration, the depletion layer directly under the gate of the source follower Q4 is held at a voltage between (gate voltage Vin) and (source voltage Vout), so that the substrate bias effect does not occur.

The details will be described below. FIG. 5A shows a circuit when the source follower Q4 is an NMOS and the substrate potential is ground (ie, the well region and the source are not connected). When the voltage Vin input to the gate of the source follower Q4 increases, the voltage between the gate and the substrate of the source follower Q4 increases, the depletion layer formed directly under the gate increases, and the threshold voltage Vth of the source follower Q4 ( The threshold between the gate and the source) rises.

On the other hand, since the load transistor Q5 is connected to the source follower Q4 and the load transistor Q5 provides a constant current load, it is necessary to increase the voltage Vgs between Vin and Vout by the amount that the threshold voltage Vth rises. There is. That is, as shown in FIG. 5A (b), the threshold voltage Vth substantially fluctuates depending on the input gate voltage Vin (board bias effect). Therefore, Vout does not change linearly with respect to the change of Vin, and it becomes impossible to supply a voltage having an accurate gradation to the liquid crystal 42.

On the other hand, in the present embodiment, as shown in FIG. 5B (a), the well region of the source follower Q4 is separated from the surrounding wells and connected to the source. Therefore, the well potential and the source potential are the same potential. With such a configuration, the depletion layer directly under the gate of the source follower Q4 is held at the voltage between Vin and Vout, so that the above-mentioned substrate bias effect does not occur. That is, as shown in FIG. 5B (b), Vout also changes linearly with substantially the same slope with respect to the change in Vin. Therefore, a Vout that changes linearly with a change in the voltage Vin supplied to the gate of the source follower Q4 can be obtained. That is, in the present embodiment, by connecting the well region of the source follower Q4 and the source and making the well potential and the source potential the same potential, it is possible to supply a stable drive voltage to the liquid crystal 42.

Returning to FIG. 4, the liquid crystal 42 is driven according to the potential difference between the drive voltage given to the pixel electrode q1 from the pixel circuit 21 and the common electrode given 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. 6 is an explanatory diagram schematically showing the angles of the incident light incident on the pixel circuit 21 and the reflected light reflected by the reflected pixel 20 corresponding to the pixel circuit 21. In FIG. 6, reference numeral st indicates incident light incident from a direction orthogonal to the reflection pixel 20 corresponding to each pixel circuit 21, reference numeral sa1 indicates reflected light reflected by the reflection pixel 20 at an angle θa, and reference numeral sb1. Indicates the reflected light reflected at an angle θb. The same phase plane of the incident light st (the plane whose normal direction is 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. 6, the incident light st is irradiated from a direction substantially orthogonal to the reflective pixel 20, and is incident on 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 of the conventional drive voltage is the voltage Va, the reflection angle of the reflected light sa1 obtained when the voltage is gradually changed from the minimum voltage Vmin to the voltage Va in the continuous pixel circuit 21 is θa. On the other hand, when the charge pump 31 is driven, the maximum drive voltage is Vb (Vb> Va), and the reflected light sb1 reflected at a larger reflection angle θb can be obtained.

At this time, for example, a large refractive index nmax is obtained in the liquid crystal on the pixel to which Vmin is applied, and the liquid crystal on the pixel to which the maximum voltage Va is applied changes to, for example, a small refractive index na. Since the light incident on the liquid crystal having the refractive index na travels faster than the light incident on the liquid crystal having the refractive index nmax, the reflected light is emitted by bending 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 of 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 a clock signal for horizontal scanning (HCK1, HCK2). The shift register circuit 26 sequentially shifts the clock signals based on the horizontal synchronization signal and the clock signal for horizontal scanning, and outputs the switching signal (this is 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). Further, the switches SW1 to SWm are controlled to be on or off based on the switching signal (SD1 to SDm) output from the shift register circuit 26. The switches SW1 to SWm are provided corresponding to the column data lines (D1 to Dm), and the control voltage "d" corresponding to each column data line is sequentially input.

The switches SW1 to SWm selectively apply a control voltage corresponding to each column data line (D1 to Dm) to the column data line. For example, the switch SW1 is turned on when the switching signal SD1 is at a 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 the present embodiment, a double voltage (2 * VLC), which is twice the maximum voltage VLC, is set, and k gradation (k gradation (2 * VLC) is set within the range of the voltage "0" to the double voltage "2 * VLC". However, k is an integer of 3 or more). Then, by switching the drive and stop of the charge pump 31, the control voltage (voltage in the range of 0 to VLC) supplied from the column data line is in the above-mentioned k gradation voltage (range of 0 to 2 * VLC). It is controlled to be (voltage).

Hereinafter, a detailed description will be given with reference to FIG. 8A. FIG. 8A is a graph in which the horizontal axis shows the above-mentioned k gradation (5 gradations in this example), and the vertical axis shows the control voltage supplied from the voltage supply line X1 to the pixel circuit 21 via the column data line. is there.

Graph R1 shown in FIG. 8A shows the characteristics when the drive voltage supplied to the liquid crystal 42 is the maximum voltage VLC or less, and graph R2 shows the characteristics when the drive voltage supplied to the liquid crystal 42 is the maximum voltage VLC or more. It shows. Although the graphs R1 and R2 show an example in which the voltage changes linearly, the present invention is not limited to this, and the change may be monotonously increasing in the range of 0 to VLC.

For example, when the number of gradations of the drive voltage supplied to the liquid crystal 42 is "5" (that is, k = 5), the above-mentioned double voltage (2 * VLC) is divided into five equal parts and the gradations 1 to 1. Gradation 5 is set. Therefore, the double voltage (2 * VLC) is divided into five equal parts, and the gradation 1 is (1/5) * 2 * VLC voltage, and the gradation 2 is (2/5) * 2 * VLC voltage, gradation. The control voltage is (3/5) * 2 * VLC voltage as 3, the (4/5) * 2 * VLC voltage as the gradation 4, and the (5/5) * 2 * VLC voltage as the gradation 5. It suffices if it is supplied to the pixel circuit 21.

However, since the control voltage corresponding to the gradations 3 to 5 described above exceeds the maximum voltage VLC, the control voltage corresponding to the gradations 3 to 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 of each control voltage is output, and then the charge pump 31 amplifies the voltage twice. That is, the control voltage of (3/5) * VLC as the gradation 3, (4/5) * VLC as the gradation 4, and VLC as the gradation 5 is output, and the charge pump provided in each pixel circuit 21 is provided. It is amplified twice by 31.

That is, when the control voltage for obtaining the desired gradation is equal to or less than the maximum voltage VLC (in the case of gradations 1 and 2), as shown in the graph R1 of FIG. 8A, the control voltage is driven without being amplified. Get the 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 Graph R2 of FIG. 8A, half of this voltage is controlled. A desired drive voltage is obtained by supplying the voltage to the pixel circuit 21 and then amplifying the voltage twice with the charge pump 31. Therefore, the slope of the graph R2 is half the slope of the graph R1.

That is, in the switch control unit 25, the voltage corresponding to an arbitrary gradation is the maximum voltage (VLC) among a plurality of preset gradations in the range up to a voltage (double voltage) larger than the maximum voltage (VLC). ) In the following cases, the control voltage is output to the source follower Q4 and thus to the liquid crystal 42 without being amplified. On the other hand, when the voltage corresponding to an arbitrary gradation exceeds the maximum voltage (VLC) among a plurality of gradations, the control voltage is amplified by the charge pump 31 and output to the source follower Q4 and eventually to the liquid crystal 42. To control.

In this way, by controlling the on / off of each switch SW1 to SWm provided in the switch circuit 27 and controlling the drive of the charge pump 31, the pixel circuit 21 has k gradation (5 in the above example). A drive signal corresponding to the gradation) is generated and output to the source follower Q4. That is, as shown in graph R3 of FIG. 8B, it is possible to output the drive voltage of gradation 1 to gradation 5 obtained by dividing the double voltage (2 * VLC) into 5 equal parts to the source follower Q4. Become.

Further, since the drive voltage output to the output point q3 of the source follower Q4 is connected to the pixel electrode q1 via the second changeover switch S5, the source follower is turned on when the second changeover switch S5 is turned on. The drive voltage output from Q4 can be supplied to the liquid crystal 42.

Further, the short-circuit line J1 connected to the pixel circuit 21a (one pixel circuit) is switched between short-circuiting and opening with the short-circuit line J1 connected to the pixel circuit (another pixel circuit) adjacent to the pixel circuit 21a. A first changeover switch S6 for this purpose is provided. Therefore, by short-circuiting the first changeover switch S6, it is possible to short-circuit between the pixel electrode q1 of the pixel circuit 21a and the pixel electrode of the adjacent pixel circuit. By turning on the first changeover switch S6, the potential of the pixel electrode q1 between adjacent pixel circuits (pixel circuits controlled to have the same refractive index) can be made constant. The first changeover switch S6 is turned on and off by a control signal supplied from the control line K1-3.

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

The switch control unit 25 outputs a drive signal to each drive line (L1 to Ln) shown in FIG. Specifically, among a plurality of gradations (for example, gradations 1 to 5) set within a range up to a voltage (2 * VLC) larger than the maximum voltage (VLC), any gradation (for example, gradation 1 to gradation 5) For example, when the voltage corresponding to the gradation 1) is equal to or less than the maximum voltage (VLC), an "H" level signal is output to the drive line. Further, when the voltage corresponding to an arbitrary gradation (for example, gradation 3) exceeds the maximum voltage (VLC) among the plurality of gradations, an "L" level signal is output to the drive line.

That is, the switch control unit 25 uses the control voltage as the output voltage when the drive voltage supplied to the liquid crystal 42 is equal to or less than the maximum voltage VLC, and charges the switch control unit 25 when the drive voltage supplied to the liquid crystal 42 exceeds the maximum voltage VLC. It has a function as a charge pump control unit that controls to supply the voltage amplified by the pump 31 as an output voltage to the liquid crystal 42.

Further, when the switch control unit 25 supplies the output voltage of the one pixel circuit 21 to the liquid crystal 42, the switch control unit 25 opens the first changeover switch S6 and does not supply the output voltage of the one pixel circuit to the liquid crystal 42. It has a function as a changeover switch control unit that controls the first changeover switch S6 so as to short-circuit at least a part of the time.

Further, the switch control unit 25 does not drive the charge pump 31 when the drive line L1 is supplied with the “H” level signal, and is not driven when the drive line L1 is supplied with the “L” level signal. The charge pump 31 is controlled to be driven. The operation of the charge pump 31 will be described below.

When driving the charge pump 31, the switch control unit 25 transmits a control signal for controlling on / off of each of the switches S1 to S4 shown in FIG. 4 to the control lines K1 (K1-1, K1-2). Output. Specifically, in the case of driving the charge pump 31, when the control voltage is supplied from the column data line D1, the switches S1 and S4 are turned on first, and the switches S2 and S3 are turned off.

Therefore, the control voltage supplied from the column data line D1 is stored in the capacitor C1. After the elapse of a predetermined time, 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 stored in the capacitor C1 are added, and the added voltage is stored 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 is output to the source follower Q4.

Then, in the phase modulation apparatus 101 according to the present embodiment, a block composed of several pixel circuits among the (n × m) pixel circuits 21 provided in FIG. 3 is set. For example, as shown in FIG. 7A, a block composed of a pixel circuit 21 (5 rows × 6 columns) is set. In FIG. 7A, a suffix “-nm” is added to identify the rows (n) and columns (m) of each pixel circuit 21. Therefore, the 1-row, 1-column pixel circuits shown in FIG. 7A are 21-11, and the 5-row, 6-column pixel circuits are 21-56.

In FIG. 7A, 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 a control voltage corresponding to gradation 1 among gradations 1 to 5. Further, in the vertical direction, the gradation is set so as to gradually increase from the top to the bottom in the figure, and the control voltage corresponding to the gradation 5 is supplied to the pixel circuits 21-51 to 21-56 in the lowermost stage.

Specifically, as shown in FIG. 7B, in each of the pixel circuits 21-11 to 21-51 arranged in the vertical direction, the drive voltage supplied to each liquid crystal 42 corresponds to the gradation 1 to the gradation 5. It is set to change in stages. Therefore, the six pixel circuits 21 can be grouped into one group, and the reflectance can be changed in five ways, and thus the reflected light phase-modulated in five ways can be obtained.

[Explanation of operation of this embodiment]
Next, the operation of the phase modulation apparatus 101 according to the present embodiment configured as described above will be described with reference to the graphs shown in FIGS. 8A and 8B and the timing charts shown in FIGS. 9A and 9B. FIG. 8B is a graph showing the relationship between the gradation set in five stages and the drive voltage supplied to the liquid crystal 42. Further, as shown in FIG. 7A, an example in which each pixel circuit 21 arranged in a 6 × 5 matrix and a reflection pixel corresponding to each pixel circuit 21 are provided will be described below.

The horizontal scanning circuit 23 shown in FIG. 3 controls the on / off of the switches SW1 to SWm (here, m = 6) provided in the switch circuit 27, thereby supplying a control voltage from the voltage supply line X1. Is supplied to the desired column data line.

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

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 1 shown in FIG. 7 (a). The voltage "(1/5) * 2 * VLC" of gradation 1 is supplied to the pixel circuits 21-11 to 21-16 in the second line, and the gradation 2 is supplied to the pixel circuits 21-21 to 21-26 in the second line. The voltage of "(2/5) * 2 * VLC" is supplied.

Further, a voltage of gradation 3 is supplied to the pixel circuits 21-31 to 21-36 on the third line. In this case, the voltage supplied to the pixel circuit becomes "(3/5) * 2 * VLC", which exceeds the maximum voltage VLC. Therefore, as shown in FIG. 8A, "(3/5) * VLC", which is half the above voltage, is output as a control voltage, and this voltage is doubled by the charge pump 31 to "((3/5) * VLC". A voltage of "3/5) * 2 * VLC" is generated to obtain a voltage of gradation 3.

Similarly, for the pixel circuits 21-41 to 21-46 on the 4th line and the pixel circuits 21-51 to 21-56 on the 5th line, half the voltage is output as the control voltage, and then the charge pump 31 outputs 2 By amplifying twice, a voltage of gradation 4 and gradation 5 is generated.

Next, the operation in the pixel circuit 21 will be described with reference to the timing charts shown in FIGS. 9A and 9B. 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 above-mentioned gradation 1 and gradation 2, the charge pump 31 is not operated. In this case, as shown in time t0 to t1 of FIG. 9A, the switch control unit 25 outputs an H level signal to the drive line L1 to turn on the transistor Q2.

Further, as shown in FIGS. 9A (b) and 9 (c), the switches S1 to S4 are all controlled to be turned off. As a result, the transistor Q2 shown in FIG. 4 is turned on, and the input terminal p1 and the output terminal p2 of the charge pump 31 are short-circuited, so that the control voltage supplied from the column data line D1 is amplified by the charge pump 31. It is supplied to the gate of the source follower Q4 without any problem. Further, it is amplified by the source follower Q4 and accumulated in the additional capacitor C3.

After that, at time t1, the second changeover switch S5 is turned off (open), and at time t2, the first changeover switch S6 is turned on (short circuit). That is, in a state where the pixel electrode q1 in the pixel circuit 21a is cut off from the source follower Q4, the pixel electrode q1 and the pixel electrode of the pixel circuit (pixel circuit in which the refractive index is controlled to be the same) adjacent to the pixel circuit 21a are short-circuited. Will be done. Therefore, the potentials of the pixel electrodes of the adjacent pixel circuits are controlled to be the same. Then, as shown by the reference numeral z1 in FIG. 8B, a voltage of "(1/5) * 2 * VLC" can be supplied to the liquid crystal.

In this way, even when the threshold voltage between the gate and the source of the source follower Q4 provided in each pixel circuit 21 varies (this is referred to as “Vth”), the second changeover switch S5 is turned off. As a result, the source follower Q4 and the pixel electrode q1 are separated. Further, the first changeover switch S6 is turned on and connected to the pixel electrode of the adjacent pixel circuit 21. Therefore, it is possible to reduce the variation in the voltage supplied to the pixel electrodes adjacent to each other. After that, at time t3, the first changeover switch S6 is turned off.

The time t2 shown in FIG. 9A is set to be slightly later than the time t1 in order to avoid simultaneous on (a state in which the first changeover switch S6 and the second changeover switch S5 are short-circuited).

Further, also in the case where the pixel circuit 21a is set to the gradation 2, the charge pump 31 is not operated in the same manner, and as shown by the reference numeral z2 in FIG. 8B, the control voltage supplied from the column data line D1 is not amplified. Output. As a result, the voltage of "(2/5) * 2 * VLC" can be applied to the liquid crystal 42, and the variation in the potential of the pixel electrodes of the adjacent pixel circuits can be reduced.

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

Specifically, at the time t10 shown in FIG. 9B, the switch control unit 25 sets the signal supplied to the drive line L1 to the L level. As a result, as shown in FIG. 9B (a), the transistor Q2 is turned off. Further, at the time t10 in FIG. 9B (b), the switch control unit 25 sends a control signal for turning on the switches S1 and S4 shown in FIG. 4 and turning off the switches S2 and S3 to the control line K1 (K1-). Output to 1, K1-2).

As a result, the control voltage "(3/5) * VLC" is accumulated in the capacitor C1. Then, at time t11, the switches S1 and S4 are turned off, and further, as shown in FIG. 9B (c), at time t12, the switches S2 and S3 are turned on. As a result, a voltage "(3/5) * 2 * VLC" that is twice the control voltage is accumulated in the output capacitor C2, and is further supplied to the gate of the source follower Q4. Further, it is amplified by the source follower Q4 and accumulated in the additional capacitor C3.

After that, the switches S2 and S3 are turned off at time t13, the second changeover switch S5 is turned off (open) at time t14 in FIG. 9 (d), and the first switch is turned off (opened) at time t15 in FIG. 9 (e). The changeover switch S6 is turned on (short circuit). That is, in a state where the pixel electrode q1 in the pixel circuit 21a is cut off from the source follower Q4, the pixel electrode q1 and the pixel electrode of the pixel circuit (pixel circuit in which the refractive index is controlled to be the same) adjacent to the pixel circuit 21a are short-circuited. Will be done. Therefore, the potentials of the pixel electrodes of the adjacent pixel circuits are controlled to be the same. Then, as shown by the reference numeral z3 in FIG. 8B, the voltage of "(3/5) * 2 * VLC" can be supplied to the liquid crystal 42.

Therefore, even if the threshold voltage between the gate and the source of the source follower Q4 provided in each pixel circuit 21 varies (this is referred to as “Vth”), the source follower Q4 and the pixel electrode q1 are separated. Since it is connected to the pixel electrodes of the adjacent pixel circuits 21, it is possible to reduce the variation in the voltage supplied to the pixel electrodes adjacent to each other. After that, at time t16, the first changeover switch S6 is turned off.

Further, also in the case where the pixel circuit 21a is set to the gradations 4 and 5, by operating the charge pump 31 in the same manner, the control voltage supplied from the column data line D1 as shown by the reference numerals z4 and z5 in FIG. 8B. Is amplified and output. As a result, the voltages of "(4/5) * 2 * VLC" and "2 * VLC" can be applied to the liquid crystal 42, and the variation in the potentials of the pixel electrodes of the adjacent pixel circuits can be reduced.

[Explanation of the effect of this embodiment]
In this way, in the phase modulation device 101 according to the present embodiment, each pixel circuit 21 is provided with a charge pump 31. Then, when setting an arbitrary gradation among a plurality of preset gradations in the range from "0" to twice the maximum voltage (2 * VLC), the arbitrary gradation is supported. When the voltage is equal to or less than the maximum voltage (VLC), the control voltage supplied to the pixel circuit 21 from the column data line is output without being amplified.

Further, when the voltage corresponding to an arbitrary gradation exceeds the maximum voltage (VLC) among the plurality of gradations, the charge pump 31 amplifies and outputs the control voltage. Then, the output voltage is amplified by the source follower Q4 and supplied to the pixel electrode q1, and eventually 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 liquid crystal 42 is driven in the range of the voltage (2 * VLC) which is twice that voltage. It is 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, the increase in the thickness of the liquid crystal layer 12 can be suppressed, and the accuracy of phase modulation can be improved.

Further, since the well region of the source follower Q4 and the source are connected and the well potential and the source potential are the same potential, as shown in FIG. 5B (b), the voltage supplied to the gate of the source follower Q4 is adjusted. On the other hand, it is possible to obtain an output voltage that changes almost linearly. Therefore, even when the source follower Q4 is used, a stable voltage can be supplied to the liquid crystal 42, and the refractive index of the liquid crystal 42 can be set stably.

Further, 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, each component constituting the control circuit 22 and each component constituting the charge pump shown in FIG. 4 can be set. It is not necessary to increase the withstand voltage of the parts and the transistors Q1 and Q2, and it is possible to reduce the size and weight of the device.

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

Further, in the present embodiment, the refractive index of the liquid crystal 42 is set to change toward one of the directions orthogonal to each other, that is, the column direction and the row direction shown in FIG. 3, and in the other direction. , Drive lines (L1 to Ln) for switching on / off of the charge pump are arranged. Therefore, it is possible to prevent the orientation of the liquid crystal from being disturbed due to a change in the refractive index.

Further, the second changeover switch S5 provided between the output point q3 of the source follower Q4 and the pixel electrode q1 (supply point) is turned off, and the first changeover switch S6 is turned on to obtain the pixel electrode q1. , Connects to the pixel electrodes of the adjacent pixel circuit 21. Therefore, it is possible to reduce the variation in the threshold voltage of the source follower Q4 of each pixel circuit 21, and it is possible to prevent the generation of noise.

In the present embodiment, the range of the drive voltage is set to a voltage (2 * VLC) twice the maximum voltage, but the present invention is not limited to this, and it may be larger than the maximum voltage VLC.
Further, in the present embodiment, the configuration in which the load transistor Q5 is connected to the source follower Q4 has been described, but a load resistor may be provided instead of the load transistor Q5.

[Explanation of the second embodiment]
Next, the second embodiment of the present invention will be described. The overall configuration of the device is the same as in FIGS. 1 and 2 described above. Further, since the circuit diagram of the entire device is the same as that of FIG. 3 described above, the description thereof will be omitted. In the second embodiment, the configuration of the pixel circuit is different from that in the first embodiment described above. Hereinafter, the pixel circuit 21a'according to the second embodiment will be described with reference to FIG.

The pixel circuit 21a'shown in FIG. 10 is different from the above-described first embodiment in that the source follower Q4 shown in FIG. 4 is provided between the transistor Q1 and the charge pump 31. That is, in the second embodiment, a series connection circuit of the source follower Q4'(second source follower) and the load transistor Q5 is set between the transistor Q1 and the input terminal p1 of the charge pump 31. Further, a capacitor Cd provided between the gate and the ground of the source follower Q4'is provided.

The output terminal (source) of the transistor Q1 is branched into two systems, and one branch line is connected to the ground via the capacitor Cd. The other branch line is connected to the gate of the source follower Q4', and the output unit (connection point q3) of the source follower Q4'is connected to the charge pump 31. Further, the connection point q3 is connected to the ground via the load transistor Q5.

Further, as in the first embodiment described above, the well region of the source follower Q4'is separated from the surrounding wells and the source is connected. Therefore, the well potential and the source potential are the same potential.

Further, the output terminal p2 of the charge pump 31 is connected to the pixel electrode q1 and further connected to the short-circuit line J1. Further, as in the first embodiment described above, the short-circuit line J1 is provided with a first changeover switch S6 for switching between short-circuiting and opening with the pixel electrodes of the adjacent pixel circuit 21.

Then, in the pixel circuit 21a'according to the second embodiment, the control voltage supplied via the column data line D1 and the transistor Q1 is amplified by the source follower Q4'and then supplied to the charge pump 31 and the transistor Q2. .. Further, as in the first embodiment described above, when the drive voltage of the gradations 1 and 2 is output, the control voltage is not amplified by the charge pump 31 and the drive voltage of the gradations 3, 4 and 5 is output. In this case, the control voltage is amplified by the charge pump 31.

Further, the pixel circuit 21a'according to the second embodiment does not include the second changeover switch S5 shown in FIG. 4 and the control line K1-4 that outputs a control signal to the second changeover switch S5. Instead, the transistor Q2 and the switches S1 to S4 provided on the charge pump 31 are controlled on and off to move between the input terminal p1 and the output terminal p2 (pixel electrode q1) of the charge pump 31. Control to shut off.

Hereinafter, a detailed description will be given with reference to FIGS. 11A and 11B. FIG. 11A is a timing chart showing the operation of the transistors Q2, the switches S1 to S4, and the first changeover switch S6 provided in the pixel circuit 21 when the charge pump 31 is not operated.

When the pixel circuit 21a'is set to the above-mentioned gradation 1 and gradation 2, the charge pump 31 is not operated. In this case, as shown in time t0 to t1 of FIG. 11A, the switch control unit 25 outputs an H level signal to the drive line L1 to turn on the transistor Q2.

Further, as shown in FIGS. 11A (b) and 11 (c), all the switches S1 to S4 are controlled to be turned off. As a result, the transistor Q2 shown in FIG. 10 is turned on, and the input terminal p1 and the output terminal p2 of the charge pump 31 are short-circuited. Therefore, the control voltage supplied from the column data line D1 is amplified by the source follower Q4'and then supplied to the pixel electrode q1 without being amplified by the charge pump 31.

After that, at time t1, the transistor Q2 is turned off (open), and at time t2, the first changeover switch S6 is turned on (short-circuited). That is, in a state where the input terminal p1 and the output terminal p2 of the charge pump 31 are cut off, the pixel electrode q1 and the pixel electrode of the pixel circuit (pixel circuit in which the refractive index is controlled to be the same) adjacent to the pixel circuit 21a'are It will be short-circuited. Therefore, as in the first embodiment described above, the potentials of the pixel electrodes of the adjacent pixel circuits are controlled to be the same. Then, as shown by reference numerals z1 and z2 in FIG. 8B, a desired drive voltage can be supplied to the liquid crystal 42.

In this way, even when the threshold voltage Vth between the gate and the source of the source follower Q4'provided in the pixel circuit 21a'variably varies, the input terminal p1 and the output terminal p2 are cut off. 1 The changeover switch S6 is turned on and connected to the pixel electrode of the adjacent pixel circuit 21. Therefore, it is possible to reduce the variation in the voltage supplied to the pixel electrodes adjacent to each other. After that, at time t3, the first changeover switch S6 is turned off. A short circuit is prevented by setting the time t2 shown in FIG. 11A to be slightly later than the time t1.

On the other hand, when the pixel circuit 21a'is set to gradations 3, 4, and 5, the control voltage supplied from the column data line D1 is doubled by the charge pump 31.

Specifically, at the time t10 shown in FIG. 11B, the switch control unit 25 sets the signal supplied to the drive line L1 to the L level. As a result, as shown in FIG. 11B (a), the transistor Q2 is turned off. Further, at the time t10 in FIG. 11B (b), the switch control unit 25 turns on the switches S1 and S4 and turns off the switches S2 and S3.

As a result, the control voltage is accumulated in the capacitor C1. Then, at time t11, the switches S1 and S4 are turned off, and further, as shown in FIG. 11B (c), at time t12, the switches S2 and S3 are turned on. As a result, a voltage that is twice the control voltage is accumulated in the output capacitor C2 and supplied to the output terminal p2, which in turn is supplied to the pixel electrode q1.

After that, at time t13, the switches S2 and S3 are turned off. That is, since the transistor Q2 and the switches S1 to S4 are all turned off, the input terminal p1 and the output terminal p2 are cut off. Further, at the time t15 in FIG. 11D, the first changeover switch S6 is turned on (short-circuited). That is, in a state where the input terminal p1 and the output terminal p2 are cut off, the pixel electrode q1 and the pixel electrode of the pixel circuit (pixel circuit in which the refractive index is controlled to be the same) adjacent to the pixel circuit 21a'are short-circuited. become. Therefore, the potentials of the pixel electrodes of the adjacent pixel circuits are controlled to be the same.

Therefore, even if the threshold voltage Vth between the gate and the source of the source follower Q4'provided in each pixel circuit 21 varies, adjacent pixels are in a state where the input terminal p1 and the output terminal p2 are cut off. Since it is connected to the pixel electrodes of the circuit 21, it is possible to reduce the variation in the voltage supplied to the pixel electrodes adjacent to each other. After that, at time t16, the first changeover switch S6 is turned off. Then, as shown by the reference numerals z3 to z5 in FIG. 8B, a desired drive voltage can be supplied to the liquid crystal 42.

In this way, also in the phase modulation apparatus according to the second embodiment, when the maximum control voltage supplied to the pixel circuit 21 from the column data line is the maximum voltage (VLC) as in the first embodiment described above. In addition, it is possible to set the drive voltage for driving the liquid crystal 42 in the range of the voltage (2 * VLC) which is twice that. Therefore, the magnitude of the refractive index of the liquid crystal 42 can be changed in a wider range, the increase in the thickness of the liquid crystal layer 12 can be suppressed, and the accuracy of phase modulation can be improved.

Further, since the well region of the source follower Q4 and the source are connected and the well potential and the source potential are the same potential, as shown in FIG. 5B (b), the voltage supplied to the gate of the source follower Q4 is adjusted. On the other hand, it is possible to obtain an output voltage that changes almost linearly. Therefore, even when the source follower Q4 is used, a stable voltage can be supplied to the liquid crystal 42, and the refractive index of the liquid crystal 42 can be set stably.

Further, 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, it is not necessary to increase the withstand voltage of each component constituting the control circuit 22. In addition, since the source follower Q4'is provided in front of the charge pump 31 as compared with the first embodiment described above, the source follower Q4', the load transistor Q5, and the capacitor Cd are composed of low withstand voltage components. be able to. Therefore, it is possible to simplify the circuit configuration, and to reduce the size and weight.

Further, since the short circuit and open circuit of the input terminal p1 and the output terminal p2 are switched by controlling the on / off of the transistors Q2 and the switches S1 to S4, the second changeover switch of FIG. 4 shown in the first embodiment is switched. It is not necessary to provide S5 and the control lines K1-4. Therefore, the circuit configuration can be further simplified.

Although embodiments of the present invention have been described above, the statements and drawings that form part of this disclosure should not be understood to limit the invention. Various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art from this disclosure.

11 Reflective board 12 Liquid crystal layer 13 Opposing board 14 Sealing material 20 Reflective pixels 21, 21a, 21a'Pixel circuit 22 Control circuit 23 Horizontal scanning circuit 24 Vertical scanning circuit 25 Switch control unit (charge pump control unit)
26 Shift register circuit 27 Switch circuit 31 Charge pump 42 Liquid crystal 101 Phase modulator q1 Pixel electrode q2 Common electrode p1 Input terminal p2 Output terminal L1 to Ln Drive line D1 to Dm Column data line G1 to Gn line Scan line K1 to Kn Control line K1-1, K1-2, K1-3, K1-4 Control line J1 to Jn Short circuit line S5 2nd changeover switch S6 1st changeover switch Q4, Q4'Source follower

Claims (10)

A phase modulator 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 orthogonal to each other intersect each other, and a plurality of reflection pixels.
A liquid crystal provided corresponding to the reflected pixel and whose refractive index with respect to incident light changes depending on a driving voltage supplied from the pixel circuit.
A control circuit for controlling the pixel circuit is provided.
The column data line outputs a control voltage that changes in a range up to a predetermined maximum voltage to the pixel circuit.
The pixel circuit
A charge pump that amplifies the control voltage and a source follower that amplifies the control voltage or the control voltage amplified by the charge pump are provided.
Further, the control circuit
When the drive voltage supplied to the liquid crystal is equal to or less than the maximum voltage, the control voltage is used as the output voltage, and when the drive voltage supplied to the liquid crystal exceeds the maximum voltage, the voltage is amplified by the charge pump. It has a charge pump control unit that controls the supply of voltage to the liquid crystal as an output voltage.
A phase modulation device characterized in that a well and a source of the source follower are connected and the well potential and the source potential are the same potential. A phase modulator 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 orthogonal to each other intersect each other, and a plurality of reflection pixels.
A liquid crystal provided corresponding to the reflected pixel and whose refractive index with respect to incident light changes depending on a driving voltage supplied from the pixel circuit.
A control circuit for controlling the pixel circuit is provided.
The column data line outputs a control voltage that changes in a range up to a predetermined maximum voltage to the pixel circuit.
The pixel circuit
A source follower that amplifies the control voltage output from the column data line and a charge pump that amplifies the output voltage of the source follower are provided.
Further, the control circuit
When the drive voltage supplied to the liquid crystal is equal to or lower than the maximum voltage, the output of the source follower is used as the output voltage, and when the drive voltage supplied to the liquid crystal exceeds the maximum voltage, the charge pump amplifies the output. It has a charge pump control unit that controls the supply of the voltage to the liquid crystal as an output voltage.
A phase modulation device characterized in that a well and a source of the source follower are connected and the well potential and the source potential are the same potential. The pixel circuit further
It has a first changeover switch for switching between short-circuiting and opening of a supply point for supplying the output voltage in the pixel circuit and a supply point for supplying the output voltage in another pixel circuit adjacent to the pixel circuit.
The control circuit further
When the output voltage of the pixel circuit is supplied to the liquid crystal, the first changeover switch is opened, and the first changeover switch is opened during at least a part of the time when the output voltage of the pixel circuit is not supplied to the liquid crystal. The phase modulation apparatus according to claim 1 or 2, further comprising a changeover switch control unit that controls the changeover switch so as to short-circuit the changeover switch. The pixel circuit further
A first changeover switch that switches between short-circuiting and opening of a supply point that supplies the output voltage in the pixel circuit and a supply point that supplies the output voltage in another pixel circuit adjacent to the pixel circuit.
A second changeover switch for switching between short-circuiting and opening between the source follower and the supply point is provided.
The control circuit further
When the output voltage of the pixel circuit is supplied to the liquid crystal, the first changeover switch is opened, and the first changeover switch is opened during at least a part of the time when the output voltage of the pixel circuit is not supplied to the liquid crystal. The phase modulation apparatus according to claim 1, further comprising a changeover switch control unit that controls the changeover switch so as to short-circuit the changeover switch. The refractive index of the liquid crystal is set to change in one of the directions orthogonal to each other, and a drive line for switching on / off of the charge pump is arranged in the other direction. The phase modulator according to any one of claims 1 to 4. The pixel circuit includes a short-circuit switch that short-circuits an input terminal for supplying the control voltage to the charge pump and an output terminal for outputting a voltage from the charge pump to the liquid crystal.
The charge pump control unit short-circuits the short-circuit switch when the drive voltage output to the liquid crystal is equal to or lower than the maximum voltage, and short-circuits the short-circuit switch when the drive voltage output to the liquid crystal exceeds the maximum voltage. The phase modulator according to any one of claims 1 to 5, characterized in that it is open. The pixel circuit includes an output capacitor that stores a voltage supplied to the liquid crystal.
The charge pump
The first capacitor that stores electric charge and
A first switch provided between one end of the first capacitor and an input terminal to which the control voltage is supplied, and
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 one end of the output capacitor,
A fourth switch provided between the other end of the first capacitor and the other end of the output capacitor,
The phase modulation apparatus according to any one of claims 1 to 6, further comprising. The phase modulation apparatus according to any one of claims 1 to 7, wherein the maximum voltage of the drive voltage supplied to the liquid crystal is set to twice the maximum voltage. A phase modulation method that reflects incident light at a desired angle.
A step of outputting a control voltage that changes in a range up to a predetermined maximum voltage to a plurality of pixel circuits provided at positions where a plurality of column data lines orthogonal to each other and a plurality of row scanning lines intersect each other.
When the drive voltage supplied to the liquid crystal, which is provided corresponding to each pixel circuit and whose refractive index with respect to the incident light changes according to the input drive voltage, is equal to or less than the maximum voltage, the control voltage is applied to the charge pump. The step of amplifying the voltage that is not amplified by the source follower and outputting it to the supply point,
When the drive voltage supplied to the liquid crystal exceeds the maximum voltage, the step of amplifying the control voltage by the charge pump and amplifying the voltage by the source follower and outputting it to the supply point is provided.
A phase modulation method characterized in that a well and a source of the source follower are connected and the well potential and the source potential are the same potential. A phase modulation method that reflects incident light at a desired angle.
A step of outputting a control voltage that changes in a range up to a predetermined maximum voltage to a plurality of pixel circuits provided at positions where a plurality of column data lines orthogonal to each other and a plurality of row scanning lines intersect each other.
The step of amplifying the control voltage by the source follower and
When the drive voltage supplied to the liquid crystal, which is provided corresponding to each pixel circuit and whose refractive index with respect to the incident light changes according to the input drive voltage, is equal to or less than the maximum voltage, the output voltage of the source follower is used. The step of outputting to the supply point without amplifying with the charge pump,
When the drive voltage supplied to the liquid crystal exceeds the maximum voltage, the step of amplifying the output voltage of the source follower by the charge pump and outputting it to the supply point is provided.
A phase modulation method characterized in that a well and a source of the source follower are connected and the well potential and the source potential are the same potential.

Images