JP6135701B2 - Projector and method for controlling light emitting unit and light modulation device - Google Patents

Description

  The present invention relates to a projector.

  A projector that employs a so-called color sequential method usually includes a light emitting unit and a light modulation device including a plurality of light modulation elements. The light emitting unit sequentially emits three color lights, and the light modulation device sequentially modulates the three color lights.

  Specifically, the light emitting unit sequentially emits three color lights in three color periods within one frame period in which one image is displayed. The plurality of light modulation elements included in the light modulation device sequentially modulate the three color lights in three color periods in accordance with the plurality of pixel data constituting the image data.

  In the light modulation device, each light modulation element is set to an on state or an off state according to each pixel data. Specifically, each light modulation element is turned on in three color periods within one frame period according to three color data constituting each pixel data. That is, the gradation value of one color data is expressed by the time (or the number of times) that the light modulation element is set to the on state within the corresponding one color period.

  As the light modulation device, for example, a liquid crystal panel, DMD (digital micromirror device: trademark of TI), or the like is used.

Japanese Patent Laid-Open No. 11-305710 JP 2003-102030 A

  However, conventionally, the method for controlling the light emitting unit and the light modulation device has not been sufficiently considered, and another method has been desired.

  The present invention has been made to solve the above-described problems in the prior art, and an object thereof is to provide a new control method for the light emitting unit and the light modulation device of the projector.

SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.
[Form 1]
A projector,
A light emitting unit for emitting a plurality of colored lights;
A light modulation device that includes a plurality of light modulation elements and modulates the plurality of color lights;
A control unit that controls the light emitting unit and the light modulation device to display an image represented by image data in a frame period;
With
The image data includes a plurality of pixel data, and each pixel data includes a plurality of color data corresponding to the plurality of color lights,
The frame period includes a plurality of sub-periods, and each sub-period includes a plurality of color periods corresponding to the plurality of color lights,
The lengths of the sub-periods are equal to each other, and the lengths of the color periods corresponding to the same colored light respectively included in the plurality of sub-periods are equal to each other.
The controller is
A light emission control unit that sequentially emits the plurality of color lights in the plurality of color periods in each of the sub periods;
The modulation state of the plurality of light modulation elements is controlled according to the plurality of pixel data of the image data, and each of the sub periods according to specific color data corresponding to specific color light included in the pixel data A modulation control unit that controls a modulation state of the light modulation element in a specific color period corresponding to the specific color light included in
With
The plurality of sub-periods are:
A first type of sub-period;
A plurality of second-type sub-periods that are later than the first-type sub-periods;
Contains
The light emission control unit
A period in which the specific color light is emitted from the light emitting unit within the specific color period included in the first type sub-period is included in the specific color period included in each of the second type sub-periods. The specific color light is set to be smaller than the period in which the specific color light is emitted from the light emitting unit, and the specific color light is emitted from the light emitting unit within the specific color period included in each of the second type sub-periods. By setting the period to the same length as the specific color period, the period during which the specific color light is emitted from the light emitting unit in the plurality of second type sub-periods is set to be the same,
The projector which allocates the period when the said specific color light is inject | emitted from the said light emission part in the said 1st type sub period to the second half part of the said specific color period. According to this aspect, the specific color light is emitted from the light emitting unit in the specific color period in each sub period, and in the specific color period in each sub period, according to the specific color data, The modulation state is controlled. The gradation of specific color data is expressed by the cumulative energy of specific color light guided to the image display area in a plurality of specific color periods within a plurality of sub-periods. However, in this projector, the period in which the specific color light is emitted from the light emitting unit in the first type sub-period is set to be smaller than the period in which the specific color light is emitted from the light emitting unit in the second type sub-period. Yes. That is, a rough gradation is expressed using a period in which specific color light is emitted from the light emitting unit in the second type sub-period, and specific color light is emitted from the light emitting unit in the first type sub-period. Fine gradation is expressed using the period. Even if this control method is adopted, the image represented by the image data can be appropriately displayed. Further, according to this embodiment, since each color light can be incident on the light modulation element after the modulation state of the light modulation element is sufficiently stabilized, the gradation value of each color data can be expressed more accurately.

[Application Example 1] A projector,
A light emitting unit for emitting a plurality of colored lights;
A light modulation device that includes a plurality of light modulation elements and modulates the plurality of color lights;
A control unit that controls the light emitting unit and the light modulation device to display an image represented by image data in a frame period;
With
The image data includes a plurality of pixel data, and each pixel data includes a plurality of color data corresponding to the plurality of color lights,
The frame period includes a plurality of sub-periods, and each sub-period includes a plurality of color periods corresponding to the plurality of color lights,
The controller is
A light emission control unit that sequentially emits the plurality of color lights in the plurality of color periods in each of the sub periods;
The modulation state of the plurality of light modulation elements is controlled according to the plurality of pixel data of the image data, and each of the sub periods according to specific color data corresponding to specific color light included in the pixel data A modulation control unit that controls a modulation state of the light modulation element in a specific color period corresponding to the specific color light included in
With
The plurality of sub-periods are:
A first type of sub-period;
A plurality of second type sub-periods;
Contains
The light emission control unit
The intensity of the specific color light emitted from the light emitting unit during the specific color period included in the first type sub-period, and the light emission during the specific color period included in each of the second type sub-periods. The projector is set to be smaller than the intensity of the specific color light emitted from the unit.

  In this projector, a specific color light is emitted from the light emitting unit in a specific color period in each sub period, and the modulation state of the light modulation element is determined in accordance with specific color data in the specific color period in each sub period. Is controlled. The gradation of specific color data is expressed by the cumulative energy of specific color light guided to the image display area in a plurality of specific color periods within a plurality of sub-periods. However, in this projector, the intensity of the specific color light emitted from the light emitting unit in the first type sub-period is set smaller than the intensity of the specific color light emitted from the light emitting unit in the second type sub-period. Yes. That is, a rough gradation is expressed using the intensity of the specific color light emitted from the light emitting unit in the second type sub-period, and the specific color light emitted from the light emitting unit in the first type sub-period. Using the intensity, fine gradation is expressed. Even if this control method is adopted, the image represented by the image data can be appropriately displayed.

[Application Example 2] The projector according to Application Example 1,
The period during which the specific color light is emitted from the light emitting unit during the plurality of sub-periods is the same.

[Application Example 3] The projector according to Application Example 1 or 2,
The plurality of sub-periods includes a plurality of the first-type sub-periods,
The projectors, wherein the specific color lights emitted from the light emitting units in the plurality of first type sub-periods have different intensities.

  In this way, it is possible to express fine gradation using specific color light emitted from the light emitting unit in a plurality of first type sub-periods.

Application Example 4 The projector according to any one of Application Examples 1 to 3,
The projector, wherein the specific color light emitted from the light emitting unit in the plurality of second type sub-periods has the same intensity.

  In this way, rough gradation can be expressed using specific color light emitted from the light emitting unit in the plurality of second type sub-periods.

Application Example 5 A projector,
A light emitting unit for emitting a plurality of colored lights;
A light modulation device that includes a plurality of light modulation elements and modulates the plurality of color lights;
A control unit that controls the light emitting unit and the light modulation device to display an image represented by image data in a frame period;
With
The image data includes a plurality of pixel data, and each pixel data includes a plurality of color data corresponding to the plurality of color lights,
The frame period includes a plurality of sub-periods, and each sub-period includes a plurality of color periods corresponding to the plurality of color lights,
The controller is
A light emission control unit that sequentially emits the plurality of color lights in the plurality of color periods in each of the sub periods;
The modulation state of the plurality of light modulation elements is controlled according to the plurality of pixel data of the image data, and each of the sub periods according to specific color data corresponding to specific color light included in the pixel data A modulation control unit that controls a modulation state of the light modulation element in a specific color period corresponding to the specific color light included in
With
The plurality of sub-periods are:
A first type of sub-period;
A second sub-period;
Contains
The light emission control unit
A period during which the specific color light is emitted from the light emitting unit within the specific color period included in the first type sub-period, and a period within the specific color period included in the second type sub-period. A projector that is set to be smaller than a period in which the specific color light is emitted from the light emitting unit.

  In this projector, a specific color light is emitted from the light emitting unit in a specific color period in each sub period, and the modulation state of the light modulation element is determined in accordance with specific color data in the specific color period in each sub period. Is controlled. The gradation of specific color data is expressed by the cumulative energy of specific color light guided to the image display area in a plurality of specific color periods within a plurality of sub-periods. However, in this projector, the period in which the specific color light is emitted from the light emitting unit in the first type sub-period is set to be smaller than the period in which the specific color light is emitted from the light emitting unit in the second type sub-period. Yes. That is, a rough gradation is expressed using a period in which specific color light is emitted from the light emitting unit in the second type sub-period, and specific color light is emitted from the light emitting unit in the first type sub-period. Fine gradation is expressed using the period. Even if this control method is adopted, the image represented by the image data can be appropriately displayed.

[Application Example 6] The projector according to Application Example 5,
The projector having the same intensity of the specific color light emitted from the light emitting unit in the plurality of sub-periods.

[Application Example 7] The projector according to Application Example 5 or 6,
The plurality of sub-periods includes a plurality of the first-type sub-periods,
Projectors in which the specific color light is emitted from the light emitting unit in the plurality of first type sub periods.

  In this way, it is possible to express fine gradation using specific color light emitted from the light emitting unit in a plurality of first type sub-periods.

[Application Example 8] The projector according to any one of Application Examples 5 to 7,
The plurality of sub-periods includes a plurality of the second-type sub-periods,
A projector in which a period during which the specific color light is emitted from the light emitting unit in the plurality of second type sub periods is the same.

  By so doing, it is possible to roughly represent gradation using specific color light emitted from the light emitting section in a plurality of second type sub-periods.

[Application Example 9] The projector according to any one of Application Examples 1 to 8,
The light emitting unit
A projector comprising a plurality of light emitting devices that emit the plurality of color lights.

  If this configuration is adopted, each light emitting device only needs to emit light in each corresponding color period within each sub period, and thus the light emitting period per time of each light emitting device can be set to be relatively small. For this reason, the intensity | strength of the color light inject | emitted per time from each light emitting device can be increased, As a result, the brightness of the image displayed can be increased.

[Application Example 10] The projector according to Application Example 9,
Each of the light emitting devices includes a semiconductor light emitting element.

Other Application Example 1 In a projector including a light emitting unit that emits a plurality of color lights and a light modulation device that includes a plurality of light modulation elements and modulates the plurality of color lights, an image represented by image data is displayed. A computer program for causing a computer to control the light emitting unit and the light modulation device for displaying in a frame period,
The image data includes a plurality of pixel data, and each pixel data includes a plurality of color data corresponding to the plurality of color lights,
The frame period includes a plurality of sub-periods, and each sub-period includes a plurality of color periods corresponding to the plurality of color lights,
The program is
A function of causing the light emitting unit to sequentially emit the plurality of color lights in the plurality of color periods in each of the sub-periods;
The modulation state of the plurality of light modulation elements is controlled according to the plurality of pixel data of the image data, and each of the sub periods according to specific color data corresponding to specific color light included in the pixel data A function of controlling a modulation state of the light modulation element in a specific color period corresponding to the specific color light included in
To the computer,
The plurality of sub-periods are:
A first type of sub-period;
A plurality of second type sub-periods;
Contains
The function of sequentially emitting the plurality of color lights is as follows:
The intensity of the specific color light emitted from the light emitting unit during the specific color period included in the first type sub-period, and the light emission during the specific color period included in each of the second type sub-periods. A computer program including a function of setting the intensity of the specific color light emitted from the unit to be smaller than the intensity.

[Other Application Example 2] In a projector including a light emitting unit that emits a plurality of color lights and a light modulation device that includes a plurality of light modulation elements and modulates the plurality of color lights, an image represented by image data is displayed. A computer program for causing a computer to control the light emitting unit and the light modulation device for displaying in a frame period,
The image data includes a plurality of pixel data, and each pixel data includes a plurality of color data corresponding to the plurality of color lights,
The frame period includes a plurality of sub-periods, and each sub-period includes a plurality of color periods corresponding to the plurality of color lights,
The program is
A function of causing the light emitting unit to sequentially emit the plurality of color lights in the plurality of color periods in each of the sub-periods;
The modulation state of the plurality of light modulation elements is controlled according to the plurality of pixel data of the image data, and each of the sub periods according to specific color data corresponding to specific color light included in the pixel data A function of controlling a modulation state of the light modulation element in a specific color period corresponding to the specific color light included in
To the computer,
The plurality of sub-periods are:
A first type of sub-period;
A second sub-period;
Contains
The function of sequentially emitting the plurality of color lights is as follows:
A period during which the specific color light is emitted from the light emitting unit within the specific color period included in the first type sub-period, and a period within the specific color period included in the second type sub-period. A computer program including a function of setting a period smaller than a period in which the specific color light is emitted from a light emitting unit.

  The present invention relates to a projector and a control method thereof, a computer program for realizing the functions of these methods or apparatuses, a recording medium recording the computer program, and a data signal embodied in a carrier wave including the computer program It can be realized in various modes such as.

It is explanatory drawing which shows schematic structure of the projector PJ. It is explanatory drawing which shows the internal structure of the light emitting device control part 510 and three light emitting devices 110R, 110G, 110B. 4 is an explanatory diagram schematically showing current-light intensity characteristics of a semiconductor laser 112. FIG. It is explanatory drawing which shows a gradation conversion process. It is a timing chart which shows operation | movement of the projector PJ. It is explanatory drawing which shows the 2nd partial control data PXg corresponding to G data. It is explanatory drawing which shows the relationship between the gradation value of color data, and the presence or absence of generation | occurrence | production of the ON period in the corresponding color period in each sub period. It is explanatory drawing which shows the intensity | strength of the light in a comparative example and 1st Example. It is a timing chart which shows operation | movement of the projector PJ in 2nd Example. It is explanatory drawing which shows the 2nd partial control data PXg corresponding to G data in 2nd Example. It is explanatory drawing which shows the intensity | strength of the light in a comparative example and 2nd Example. It is explanatory drawing which shows typically the electric current-light intensity characteristic of the light-emitting device in a modification.

Next, embodiments of the present invention will be described in the following order based on examples.
A. First embodiment:
A-1. Projector configuration:
A-2. Projector operation:
A-3. Light intensity of light emitting device:
B. Second embodiment:
C. Light emitting device variations:

A. First embodiment:
A-1. Projector configuration:
FIG. 1 is an explanatory diagram showing a schematic configuration of the projector PJ. As illustrated, the projector PJ includes three light emitting devices 110R, 110G, and 110B, a light guide system 200, a light modulation device 300, a projection optical system 400, and a control circuit 500. The projector PJ displays an image on the screen SC for each frame period using sequentially provided image data.

  The three light emitting devices 110R, 110G, and 110B emit red light (color light R), green light (color light G), and blue light (color light B), respectively. In this embodiment, each light emitting device 110R, 110G, 110B includes a semiconductor laser that emits each color light R, G, B.

  The light guide system 200 includes three optical fibers 210, an integrator rod 220, two lenses 230 and 250, and two mirrors 240 and 260. The three optical fibers 210 guide the three colored lights emitted from the three light emitting devices 110R, 110G, and 110B to the integrator rod 220. The integrator rod 220 makes the intensity distribution of each color light uniform. Each color light emitted from the integrator rod 220 passes through the first lens 230 and is reflected by the first mirror 240. Each color light reflected by the first mirror 240 passes through the second lens 250 and is reflected by the second mirror 260. Each color light reflected by the second mirror 260 enters the light modulation device 300.

  The light modulation device 300 includes a plurality of light modulation elements arranged in a matrix and an SRAM including a plurality of memory cells corresponding to the plurality of light modulation elements. As the light modulation device 300, a micromirror type device including a plurality of minute mirrors can be used. For example, DMD (digital micromirror device: trademark of TI) can be used.

  The light modulation device 300 sequentially modulates the three color lights sequentially emitted from the three light emitting devices 110R, 110G, and 110B. The modulation states of the plurality of light modulation elements (that is, the postures of the plurality of mirrors) are determined according to data written in the corresponding plurality of memory cells.

  When data “1” is written in the memory cell, the light modulation element (mirror) is set to the first state (ON state). In this case, when colored light is incident on the light modulation element, the colored light is guided to the screen SC via the projection optical system 400. On the other hand, when data “0” is written in the memory cell, the light modulation element (mirror) is set to the second state (off state). In this case, even if colored light is incident on the light modulation element, the colored light is not guided to the projection optical system 400 and the screen SC. When the modulation state of the light modulation element is changed, the light modulation element (mirror) is forcibly set to the third state. In this case as well, even if colored light is incident on the light modulation element, the colored light is not guided to the projection optical system 400 and the screen SC.

  The projection optical system 400 projects the three color lights modulated by the light modulation device 300 on the screen SC and displays a color image on the screen SC.

  The control circuit 500 controls the entire projector PJ. The control circuit 500 includes a light emitting device control unit 510 and a light modulation device control unit 520. The operation of the light emitting device control unit 510 and the operation of the light modulation device control unit 520 are synchronized.

  The light emitting device control unit 510 controls the three light emitting devices 110R, 110G, and 110B to sequentially emit the three color lights.

  FIG. 2 is an explanatory diagram showing an internal configuration of the light emitting device control unit 510 and the three light emitting devices 110R, 110G, and 110B. As illustrated, the light-emitting device control unit 510 includes three voltage application circuits 511R, 511G, and 511B, and a signal generation circuit 518.

  The first and third voltage application circuits 511R and 511B have the same configuration as the second voltage application circuit 511G. Then, the first and third light emitting devices 110R and 110B have the same configuration as the second light emitting device 110G. For this reason, the following description will be given focusing on the second voltage application circuit 511G and the second light emitting device 110G.

  The second light emitting device 110 </ b> G includes a semiconductor laser 112 that emits colored light G, a switching element 114, and a temperature sensor 116 provided in the vicinity of the semiconductor laser 112.

  The second voltage application circuit 511G applies a voltage to the second light emitting device 110G. The second voltage application circuit 511G includes a constant voltage source 512, a voltage selection circuit 513, an adjustment voltage generation circuit 515, and an adder 516.

  The constant voltage source 512 generates five types of voltages V1, V2, V4, V8, and V16 (described later). The three sets of five types of voltages prepared by the constant voltage sources 512 of the three voltage application circuits 511R, 511G, and 511B are usually different from each other. This is due to the difference in the characteristics of the three light emitting devices 110R, 110G, and 110B (specifically, the semiconductor laser 112).

  The voltage selection circuit 513 includes five switches, selects one type of the five types of voltage, and outputs the selected one type of voltage.

  The adjustment voltage generation circuit 515 outputs an adjustment voltage according to the detection result of the temperature sensor 116 provided in the light emitting device 110G. Specifically, the adjustment voltage generation circuit 515 includes a table indicating a correspondence relationship between the temperature and the adjustment voltage, and outputs an adjustment voltage corresponding to the temperature by referring to the table. Note that the three adjustment voltages corresponding to specific temperatures prepared by the adjustment voltage generation circuit 515 of the three voltage application circuits 511R, 511G, and 511B are usually different from each other. This is due to the difference in the characteristics of the three light emitting devices 110R, 110G, and 110B (specifically, the semiconductor laser 112).

  The adder 516 adds one type of voltage supplied from the voltage selection circuit 513 and the adjustment voltage supplied from the adjustment voltage generation circuit 515, and applies the added voltage to the second light emitting device 110G. To do. The second light emitting device 110G emits light having an intensity corresponding to the applied voltage.

  FIG. 3 is an explanatory diagram schematically showing the current-light intensity characteristics of the semiconductor laser 112. As shown in the figure, the current-light intensity characteristic of the semiconductor laser changes almost linearly.

The above five types of voltages V1, V2, V4, V8, and V16 are such that when the semiconductor laser operates at a reference temperature, currents I1, I2, I4, I8, and I16 flow through the semiconductor laser 112, respectively. The intensity of the color light G emitted from 112 is set to be W1, W2, W4, W8, and W16. Assuming that the reference intensity is W ₀ , the intensity W 1, W 2, W 4, W 8, and W 16 are represented by W ₀ , 2 · W ₀ , 4 · W ₀ , 8 · W ₀ , 16 · W ₀ , respectively. Each voltage Vm (m is any one of 1, 2, 4, 8, and 16) is set to Vm = V1 + (m−1) · ΔV. ΔV is a value equal to (V2−V1).

  However, the current-light intensity characteristic of the semiconductor laser shifts according to the temperature of the semiconductor laser, as shown in FIG. Specifically, the higher the temperature, the more the right side shifts. For this reason, in this embodiment, an adjustment voltage corresponding to the detection result of the temperature sensor 116 is added to one selected voltage (for example, V4). At this time, the current (for example, I4) flowing through the semiconductor laser 112 increases. As a result, light having a predetermined intensity (for example, W4) corresponding to the selected one type of voltage (for example, V4) is emitted regardless of the temperature of the semiconductor laser 112. That is, the temperature dependence of the current-light intensity characteristic is eliminated by adding the adjustment voltage.

  The signal generation circuit 518 supplies a selection signal for causing the voltage selection circuit 513 of each of the voltage application circuits 511R, 511G, and 511B to select one of the five switches. Based on this selection signal, the voltage selection circuit 513 of each of the voltage application circuits 511R, 511G, and 511B can select one of the five types of voltages.

  The signal generation circuit 518 also supplies a drive signal to the switching element 114 of each light emitting device 110R, 110G, 110B. When the drive signal is set to H level, the semiconductor laser 112 emits colored light having an intensity corresponding to the applied voltage.

  In this embodiment, an adjustment voltage generation circuit 515 and an adder 516 are provided in each of the voltage application circuits 511R, 511G, and 511B. However, when the above temperature dependency can be ignored, It can be omitted. In this embodiment, each of the voltage application circuits 511R, 511G, and 511B includes a constant voltage source 512 for applying a plurality of types of voltages to the semiconductor laser 112, but the semiconductor laser 112 includes a plurality of types of constant currents. There may be provided a constant current source for flowing the current.

  The light modulation device control unit 520 (FIG. 1) controls the light modulation device 300 according to the original image data. The light modulation device controller 520 includes a gradation converter 522, a control data generator 524, and a timing signal generator 544.

  The gradation conversion unit 522 performs gradation conversion processing on the original image data to generate converted image data. The original image data includes a plurality of pixel data, and each pixel data is composed of three color data corresponding to the three color lights R, G, and B.

  FIG. 4 is an explanatory diagram showing the gradation conversion process. In the figure, the horizontal axis indicates the value (tone value) of each color data included in each pixel data in the image data before conversion (that is, original image data). The vertical axis indicates the value (tone value) of each color data included in each pixel data in the converted image data (that is, converted image data). As shown in the figure, each color data before conversion is expressed by 256 gradations (8 bits) and can take a value of 0 to 255, but each color data after conversion is 272 gradations (9 bits). It is expressed and can take values from 0 to 271. That is, in the present embodiment, the gradation conversion unit 522 converts the number of gradations of each color data from 256 to 272.

  The control data generation unit 524 (FIG. 1) generates control data for controlling the modulation state of the light modulation device 300 using the converted image data. Specifically, control data including a plurality of pixel control data for controlling the modulation states of the plurality of light modulation elements included in the light modulation device 300 using the plurality of pixel data included in the converted image data is provided. Generated.

  By the way, the modulation state of the light modulation element is changed a plurality of times within one frame period. The control data generation unit 524 uses the pixel data included in the converted image data to determine a period during which the corresponding light modulation element should be set to the on state within one frame period. Specifically, the control data generation unit 524 uses the pixel data included in the converted image data to generate a data string (“1” or “0”) to be written in the corresponding memory cell within one frame period. The pixel control data shown is generated.

  The timing signal generation unit 544 generates a timing signal for controlling a scanning line driver (row driver) and a data driver (column driver) included in the light modulation device 300 (specifically, SRAM). In this embodiment, a plurality of data indicating the modulation states of the plurality of light modulation elements are written to the SRAM for each row in accordance with the timing signal. Further, the modulation states of the plurality of light modulation elements are changed all at once according to the plurality of data already written in the SRAM according to the timing signal.

  Note that the three light emitting devices 110R, 110G, and 110B in the present embodiment correspond to the light emitting section in the present invention. Further, the control circuit 500 corresponds to a control unit in the present invention, and the light emitting device control unit 510 and the light modulation device control unit 520 correspond to a light emission control unit and a modulation control unit in the present invention, respectively.

A-2. Projector operation:
FIG. 5 is a timing chart showing the operation of the projector PJ. 5A shows the frame period PF, FIG. 5B shows the sub-period PS, and FIG. 5C shows the color period PC.

  Each frame period PF shown in FIG. 5A is a period in which one image represented by one image data is displayed. The length (time) of each frame period PF is Tf. Each frame period PF includes 20 sub-periods PS as shown in FIG. The length of each sub-period PS is Ts (= 1/20 × Tf). Each sub-period PS includes three color periods PCr, PCg, and PCb as shown in FIG. The first color period (R period) PCr is a period for displaying a red image, and the second color period (G period) PCg is a period for displaying a green image, and the third color The period (period B) PCb is a period for displaying a blue image. The length of each color period PCr, PCg, PCb is Tc (= 1/3 × Ts).

  FIG. 5D shows the intensity WR of the color light R emitted from the first light emitting device 110R. Similarly, FIG. 5E shows the intensity WG of the colored light G emitted from the second light emitting device 110G, and FIG. 5F shows the colored light B emitted from the third light emitting device 110B. Intensity WB is shown.

  As shown in FIGS. 5D to 5F, only the first light emitting device 110R emits light in the R period PCr. Similarly, in the G period PCg, only the second light emitting device 110G emits light, and in the B period PCg, only the third light emitting device 110B emits light. The color lights R, G, and B sequentially emitted from the light emitting devices 110R, 110G, and 110B sequentially enter the light modulation device 300.

  In the present embodiment, the light emission periods of the light emitting devices 110R, 110G, and 110B are set to be approximately equal to one color period PC.

In the present embodiment, the intensities WR, WG, WB of the respective color lights R, G, B emitted in one sub-period PS are set equal. Specifically, the intensity of each color light emitted by the first sub-period PS1 WR, WG, WB are _{W 0.} The intensity of each color light emitted in the second sub-period PS2 WR, WG, WB is 2 · _{W 0.} Intensity of each color light emitted in the third sub-period PS3 WR, WG, WB are 4 · _{W 0.} Intensity of each color light emitted by the fourth sub-period PS4 WR, WG, WB are 8 · _{W 0.} The intensity WR, WG, WB of each color light emitted in the fifth to twentieth sub-periods PS5 to PS20 is 16 · W ₀ , respectively. The reference intensity W ₀ indicates the intensity (W (watt)) of light emitted from each light emitting device 110R, 110G, 110B (semiconductor laser 112) per unit time.

  Note that the light emission period of each of the light emitting devices 110R, 110G, and 110B is determined by the drive signal output from the signal generation circuit 518. For example, the signal generation circuit 518 supplies the drive signal set to the H level in the G period PCg to the switching element 114 of the second light emitting device 110G.

  Further, the intensity of the light emitted from each of the light emitting devices 110R, 110G, and 110B is determined by the selection signal output from the signal generation circuit 518. For example, in the first to fourth sub-periods PS1 to PS4, the signal generation circuit 518 uses a selection signal for selecting the voltages V1, V2, V4, and V8 as the voltage selection of the second voltage application circuit 511G. This is supplied to the circuit 513. Further, the signal generation circuit 518 supplies a selection signal for selecting the voltage V16 to the voltage selection circuit 513 of the second voltage application circuit 511G in the fifth to twentieth sub-periods PS5 to PS20.

As a result, in the G period PCg in the first to fourth sub-periods PS1 to PS4, the intensities of the colored lights G emitted from the second light emitting device 110G are constant intensities (W ₀ , 2. W ₀ , 4 · W ₀ , 8 · W ₀ ). Further, in the G period PCg in the fifth to twentieth sub-periods PS5 to PS20, the intensities of the colored lights G emitted from the second light emitting device 110G are equal to each other at a constant intensity (16 · W ₀ ). Is set.

  The pixel control data PX shown in FIG. 5G is generated by the control data generation unit 524 and given to the light modulation device 300. The pixel control data PX is a data string generated using specific pixel data, and is sequentially supplied to and written in corresponding specific memory cells in the SRAM. FIGS. 5H to 5J show partial control data PXr, PXg, and PXb, respectively. The partial control data PXr, PXg, and PXb are data for displaying a red image, data for displaying a green image, and displaying a blue image, among the pixel control data PX shown in FIG. And data for. The partial control data PXr, PXg, and PXb shown in FIGS. 5H to 5J are shown for convenience of explanation, and the pixel control data PX shown in FIG. Are sequentially supplied.

  When the pixel control data PX is at the H level, data “1” is written in a specific memory cell, and as a result, the specific light modulation element is set to an on state. In addition, when the pixel control data PX is at the L level, data “0” is written in the specific memory cell, and as a result, the specific light modulation element is set in the OFF state. Similarly, a plurality of pixel control data generated using a plurality of pixel data in the converted image data are sequentially supplied and written in a plurality of memory cells in the SRAM.

  The pixel control data PX is set to H level or L level for each color period PC. When the pixel control data PX (more specifically, the first partial control data PXr shown in FIG. 5H) is at the H level and the color light R is emitted from the first light emitting device 110R. The color light R is guided to the projection optical system 400. Similarly, the pixel control data PX (more specifically, the second partial control data PXg shown in FIG. 5 (i)) is at the H level, and the color light G is emitted from the second light emitting device 110G. In this case, the color light G is guided to the projection optical system 400. Further, when the pixel control data PX (more specifically, the third partial control data PXb shown in FIG. 5J) is at the H level, and the color light G is emitted from the second light emitting device 110G. In this case, the color light B is guided to the projection optical system 400.

  5G to 5J show data when the gradation values of the three color data constituting the specific pixel data are the maximum value (271). For example, paying attention to the second partial control data PXg in FIG. 5 (i), the 20 G periods PCg included in the 20 sub-periods PS1 to PS20 include 20 ON periods.

  The length of each on period is Tc. The time Tc corresponds to a change period of the modulation state of each light modulation element, and each light modulation element is maintained in a constant modulation state (on state or off state) within this time Tc. As can be seen from this description, the modulation state of each light modulation element is changed 60 (= Tf / Tc = 3 × 20 × Tc / Tc) times in one frame period PF, and 3 in one sub-period PS. It is changed (= Ts / Tc = 3 × Tc / Tc) times, and is changed 1 (= Tc / Tc) times within one color period PC. When attention is paid to a specific color period PC (for example, G period PCg), the modulation state of each light modulation element is changed 20 (= 20 × Tc / Tc) times within one frame period PF. The time Tc is set larger than the shortest cycle in which the modulation state of the light modulation element can be changed.

The accumulated energy of the colored light G guided to the projection optical system 400 during the 20 ON periods included in the second partial control data PXg is 271 · W ₀ · Tc (= (W ₀ · Tc + 2 · W ₀ · Tc + 4 · W ₀ · Tc + 8 · W ₀ · Tc + 16 × 16 · W ₀ · Tc) This “271” is equal to the maximum gradation value (271) of the G data. In this embodiment, the gradation value of specific color data (for example, G data) is determined based on specific color light (for example, color light) guided to the projection optical system 400 during all on periods included in the corresponding partial control data (for example, PXg). In other words, in this embodiment, the gradation value of specific color data (for example, G data) is represented by 20 specific color periods (for example, 20 sub-periods). Projection optical system in G period PCg) It is expressed by the cumulative energy of specific color light (for example, color light G) guided to 00. The cumulative energy of light guided to the projection optical system 400 is the intensity (W of light emitted from the light emitting device per unit time). (Watts)) and the time (J (joules)) that the emitted light is guided to the projection optical system 400.

  FIG. 6 is an explanatory diagram showing second partial control data PXg corresponding to G data. FIGS. 6A, 6B, and 6C show the sub-period PS, the color period PC, and the intensity WG of the color light G, respectively. FIGS. Same as e).

  FIGS. 6D to 6M show the second partial control data PXg when the gradation value of the G data is 1, 2, 3, 4, 5, 6, 7, 269, 270, 271 respectively. Is shown. FIG. 6 (m) is the same as FIG. 5 (i).

When the gradation value of the G data is 1, the second partial control data PXg (FIG. 6D) includes one on period in the first sub period PS1. The intensity of the colored light G emitted during the one on period is W ₀ . Therefore, the energy of the colored light G guided to the projection optical system 400 during the one on period is W ₀ · Tc. When the gradation value of the G data is 2, the second partial control data PXg (FIG. 6E) includes one on period in the second sub period PS2. The intensity of the color light G emitted during the one ON period is 2 · W ₀ . Therefore, the energy of the colored light G guided to the projection optical system 400 during the one on period is 2 · W ₀ · Tc. When the gradation value of the G data is 3, the second partial control data PXg (FIG. 6 (f)) includes two ON periods in the first and second sub-periods PS1 and PS2. . The intensities of the colored light G emitted during the two ON periods are W ₀ and 2 · W ₀ , respectively. Accordingly, the accumulated energy of the colored light G guided to the projection optical system 400 during the two ON periods is 3 · W ₀ · Tc.

Similarly, when the gradation value of the G data is 269, the second partial control data PXg (FIG. 6 (k)) includes 19 on-periods in 19 sub-periods PS1, PS3 to PS20. including. The accumulated energy of the color light G guided to the projection optical system 400 during the 19 ON periods is 269 · W ₀ · Tc. When the gradation value of the G data is 270, the second partial control data PXg (FIG. 6 (l)) includes 19 on periods in 19 sub periods PS2 to PS20. The accumulated energy of the color light G guided to the projection optical system 400 during the 19 ON periods is 270 · W ₀ · Tc. When the gradation value of the G data is 271, the second partial control data PXg (FIG. 6M) includes 20 on periods in 20 sub periods PS1 to PS20. The accumulated energy of the colored light G guided to the projection optical system 400 during the 20 ON periods is 271 · W ₀ · Tc.

  In FIG. 6, the color light G emitted from the second light emitting device 110G and the second partial control data PXg have been described. However, the color light R emitted from the other light emitting devices 110R and 110B is described. , G and the other partial control data PXr, PXb.

  In this embodiment, with respect to each color data (for example, G data), whether or not an on period is generated in the corresponding color period (for example, the G period PCg) in each of the sub periods PS1 to PS20 (that is, the pixel control data PX is stored). Whether or not to set to the H level) is determined as follows.

  FIG. 7 is an explanatory diagram showing the relationship between the tone value of the color data and the presence / absence of the on period in the corresponding color period within each sub period. In the drawing, the gradation value of the color data (for example, G data) is shown on the left side, and the on period in the corresponding color period (for example, G period PCg) in each of the sub-periods PS1 to PS20 is shown on the right side. The presence or absence of occurrence is indicated.

  The gradation value of the color data is represented by a decimal number and a binary number. The number of bits of the gradation value expressed in binary number is 9 bits, and is divided into upper 5 bits and lower 4 bits.

  The presence / absence of the on period in the color period (for example, the G period PCg) in the first to fourth sub periods PS1 to PS4 is directly determined from the value of the lower 4 bits of the gradation value represented by a binary number. Has been. Of the lower 4 bits, the least significant bit corresponds to a color period in the first sub-period PS1. Similarly, the second lower bit corresponds to the color period in the second sub-period PS2, the third lower bit corresponds to the color period in the third sub-period PS3, and the fourth lower bit. Corresponds to the color period in the fourth sub-period PS4. Then, according to the value of the lower 4 bits, whether or not the on period is generated in the color period in each of the sub periods PS1 to PS4 is determined.

  For example, when the gradation value is “3”, the lower 4 bits are represented by 0011b. At this time, an on period occurs in the color periods in the first and second sub-periods PS1 and PS2, and no on-period occurs in the color periods in the third and fourth sub-periods PS3 and PS4. When the gradation value is “270”, the lower 4 bits are represented by 1110b. At this time, an on period occurs in the color period within the second sub-periods PS2 to PS4, and no on-period occurs in the color period within the first sub-period PS1.

  Note that the upper 5 bits of the gradation value represented by a binary number are the color periods in which the ON period is to be generated in the color periods (for example, the G period PCg) in the fifth to twentieth sub-periods PS5 to PS20. Used to determine the number of

  For example, when the gradation value is “3”, the upper 5 bits are represented by 00000b. 00000b is decimal 0. For this reason, when the gradation value is “3”, the ON period does not occur in the 16 color periods in the 16 sub-periods PS5 to PS20. When the gradation value is “270”, the upper 5 bits are represented by 10000b. 10000b is the decimal number 16. For this reason, when the gradation value is “270”, an ON period occurs in all 16 color periods in the 16 sub-periods PS5 to PS20.

A-3. Light intensity of light emitting device:
In this embodiment, the frame period PF is divided into 20 sub-periods PS, and each sub-period PS is divided into three color periods PCr, PCg, and PCb. The intensity of light emitted from the light emitting devices 110R, 110G, and 110B can be increased.

  FIG. 8 is an explanatory diagram showing the light intensity in the comparative example and the first example. FIGS. 8A and 8B respectively show the intensity WGz of light emitted from the second light emitting device 110G in the comparative example and the intensity WG of light emitted from the second light emitting device 110G in the present example. And.

  In the comparative example, as shown in FIG. 8A, one frame period PF is divided into three color periods. In the G period, light is emitted from the second light emitting device 110G.

  On the other hand, in this embodiment, as shown in FIG. 8B, one frame period PF is divided into 20 sub-periods PS, and each sub-period PS is divided into three color periods. Yes. In the G period included in each sub period, light is emitted from the second light emitting device 110G.

  As can be seen by comparing FIGS. 8A and 8B, in the comparative example, the only G period in one frame period PF is a relatively long period. On the other hand, in this embodiment, each of the plurality of G periods in one frame period PF is a relatively short period. However, the total time (1/3 × Tf) of a plurality of G periods in one frame period PF shown in FIG. 8B is the only G period in one frame period PF shown in FIG. It is the same as the time (1/3 × Tf).

  Further, as can be seen by comparing FIGS. 8A and 8B, in the comparative example, the intensity WGz of light emitted from the light emitting device 110G is set to be relatively small. On the other hand, in this embodiment, the intensity WG of light emitted from the light emitting device 110G is set to be relatively large.

  When the light emitting device emits light continuously, the intensity of light emitted from the light emitting device is set to a relatively small value. On the other hand, when the light emitting device emits light intermittently, the intensity of light emitted from the light emitting device can be set to a relatively large value. That is, when light is intermittently emitted from the light emitting device 110G (FIG. 8B), the light emitting device is more effective than when light is emitted continuously from the light emitting device 110G (FIG. 8A). The light intensity of 110G can be set large. For this reason, as shown in FIGS. 8A and 8B, in this embodiment, the light intensity WG of the light emitting device 110G is set larger than the light intensity WGz of the comparative example.

  As described above, in this embodiment, the intensity of light emitted from each light emitting device 110R, 110G, 110B can be increased, and as a result, the brightness of the image displayed on the screen SC can be increased. Can do.

  By the way, in the present embodiment, in the fifth to twentieth sub-periods PS5 to PS20, the intensity of light emitted from the light emitting device 110G is set to be relatively large. On the other hand, in the first to fourth sub-periods PS1 to PS4, the intensity of light emitted from the light emitting device 110G is set to be relatively small.

That is, in the comparative example, the intensity of the light emitted from the light emitting device 110G is not suppressed, but in the present embodiment, the intensity of the light emitted from the light emitting device 110G is the first to fourth sub-periods PS1. It can be said that it is suppressed in ~ PS4. In other words, in the comparative example, the output rate of the light emitting device 110G is 100%, but in this example, the output rate of the light emitting device 110G is about 85% (= 271 · W ₀ · Tc / (20 × 16 · W ₀ · Tc)). Here, the output rate means the ratio between the energy of light actually emitted during the G period within one frame period and the energy of light that can be output during the G period within one frame period.

  However, as described above, in the present embodiment, the intensity of light emitted from each light emitting device 110R, 110G, 110B can be increased. For example, in the present embodiment, the intensity of light emitted from each light emitting device 110R, 110G, 110B can be set to about three times the intensity of the comparative example. For this reason, in this embodiment, the light output rate is slightly inferior to that of the comparative example, but the brightness of the image can be considerably increased.

  As described above, in this embodiment, each frame period PF includes 20 sub-periods PS1 to PS20, and each sub-period PS1 to PS20 includes three color periods PCr, PCg, and PCb. Yes. In a specific color period (for example, G period PCg) in each sub-period PS1 to PS20, specific color light (for example, color light G) is emitted from a specific light-emitting device (for example, 110G), and specific in each sub-period PS1 to PS20. In the color period (for example, G period PCg), the modulation state of the light modulation element is controlled in accordance with specific color data (for example, G data). The gradation of the specific color data is expressed by the accumulated energy of the specific color light emitted from the specific light emitting device and guided onto the screen SC in the 20 specific color periods in the 20 sub-periods PS1 to PS20. Is done. However, in this embodiment, the period during which the light modulation element is maintained in the ON state is a certain period (Tc). For this reason, the gradation of the specific color data can be expressed by the sum of the intensities of the specific color light emitted from the specific light emitting device and guided onto the screen SC in the 20 specific color periods.

Then, among the 20 sub-periods PS1 to PS20, the intensity (W ₀ , 2 · W ₀ , intensity of specific color light emitted from a specific light-emitting device in a specific color period within the four sub-periods PS1 to PS4. 4 · W ₀ , 8 · W ₀ ) is greater than the intensity (16 · W ₀ ) of a specific color light emitted from a specific light emitting device in a specific color period within the other 16 sub-periods PS5 to PS20. It is set small. That is, a rough gradation is expressed using the intensity of a specific color light emitted in a specific color period in the 16 sub-periods PS5 to PS20, and a specific gradation in the four sub-periods PS1 to PS4 is expressed. Fine gradation is expressed by using the intensity of specific color light emitted in the color period. Specifically, the gradation of 16 · n (1 ≦ n ≦ 16) is expressed using the light intensity 16 · W ₀ , and the light intensity W ₀ , 2 · W ₀ , 4 · W ₀ , 8 · using the W _0, the gradation of 1 to 15 is represented.

  If the three light emitting devices 110R, 110G, and 110B and the light modulation device 300 are controlled as in the present embodiment, an image represented by image data (converted image data) can be appropriately expressed. . Specifically, the gradation corresponding to each color data can be appropriately expressed.

  In particular, in the present embodiment, the three light emitting devices 110R, 110G, and 110B sequentially emit three color lights in the three color periods PCr, PCg, and PCb in each of the sub periods PS1 to PS20. Therefore, it is possible to set a small light emission period for each light emitting device 110R, 110G, 110B. For this reason, the intensity | strength of the color light inject | emitted per time from each light emitting device 110R, 110G, 110B can be increased, As a result, the brightness of the image displayed can be increased.

  As can be seen from the above description, the four sub-periods PS1 to PS4 in this embodiment correspond to the first type sub-period in the present invention, and the 16 sub-periods PS5 to PS20 correspond to the second sub-period in the present invention. Corresponds to the species sub-period.

B. Second embodiment:
The second embodiment is the same as the first embodiment, except that the light emitting device control unit 510 is changed. Specifically, in this embodiment, the intensity of light emitted from each light emitting device 110R, 110G, 110B is set to a constant intensity. Therefore, in the three voltage application circuits 511R, 511G, and 511B (FIG. 2) of this embodiment, the constant voltage source 512 outputs only one type of voltage (specifically, V16) and the voltage selection circuit 513. Is omitted. In this embodiment, the signal generation circuit 518 does not output the selection signal, and changes the H level period included in the drive signal.

  FIG. 9 is a timing chart showing the operation of the projector PJ in the second embodiment, and corresponds to FIG. 9 (a) to (c) and (g) to (j) are the same as FIGS. 5 (a) to (c) and (g) to (j), but FIG. (F) has been changed.

  FIGS. 9D to 9F show the intensities WR, WG, and WB of light emitted from the three light emitting devices 110R, 110G, and 110B, similarly to FIGS. 5D to 5F.

However, in this embodiment, as shown in FIGS. 9D to 9F, the intensities WR, WG, WB of the respective color lights R, G, B emitted in the sub-periods PS1-PS20 are constant. Intensity W is set. The intensity W is set to 16 · W ₀ described above, for example.

Further, as shown in FIGS. 9D to 9F, the emission periods of the respective color lights R, G, and B are set to relatively short periods in the first to fourth sub-periods PS1 to PS4. The fifth to twentieth sub-periods PS5 to PS20 are set to relatively long periods. The color lights R in each sub-period PS1～PS20, G, emission period of B is expressed using a reference time _{T 0.} The length of the emission period of each color light in the first sub-period PS1 is T _0. The length of the emission period of each color light in the second sub-period PS2 is 2T _0. The length of the emission period of each color light in the third sub-period PS3 is 4T _0. The length of the emission period of each color light in the fourth sub-period PS4 is 8T _0. The length of the fifth to 20 light emission period of each color light in the sub-period PS5~PS20 of, respectively, a 16T _0. Here, the reference time T ₀ is approximately 1/16 × Tc. The reference time T ₀ is set to be longer than the shortest light emission period of each light emitting device.

Note that the light emission period of each of the light emitting devices 110R, 110G, and 110B is determined by the drive signal output from the signal generation circuit 518. For example, in the G period PCg of the first to fourth sub-periods PS1 to PS4, the signal generation circuit 518 is set to the H level only for the times T ₀ , 2 · T ₀ , 4 · T ₀ , 8 · T ₀ , respectively. The drive signal thus supplied is supplied to the switching element 114 of the second light emitting device 110G. Further, in the G period PCg of the fifth to twentieth sub-periods PS5 to PS20, the signal generation circuit 518 outputs the drive signal set to the H level for the period 16 · T _{0 to} the switching element of the second light emitting device 110G. 114.

As a result, in the G period PCg in the first to fourth sub-periods PS1 to PS4, the period in which the colored light G is emitted from the second light emitting device 110G is different from each other by a certain period (T ₀ , 2. T ₀ , 4 · T ₀ , 8 · T ₀ ). Further, in the G period PCg in the fifth to twentieth sub-periods PS5 to PS20, the period in which the colored light G is emitted from the second light emitting device 110G is a constant period (16 · T ₀ ) equal to each other. Is set.

  In FIGS. 9G to 9J, as in FIGS. 5G to 5J, data when the gradation values of the three color data constituting the specific pixel data are the maximum value (271). It is shown.

The accumulated energy of the colored light G guided to the projection optical system 400 during the 20 ON periods included in the second partial control data PXg is 271 · T ₀ · W (= T ₀ · W + 2 · T ₀ · W + 4 · T ₀ (W + 8 · T ₀ · W + 16 × 16 · T ₀ · W) This “271” matches the maximum gradation value (271) of the G data. As can be seen from this description, also in this embodiment, the gradation value of specific color data (for example, G data) is projected optically in 20 specific color periods (for example, G period PCg) in 20 sub-periods. It is expressed by the accumulated energy of specific color light (for example, color light G) guided to the system 400.

  FIG. 10 is an explanatory diagram showing the second partial control data PXg corresponding to the G data in the second embodiment, and corresponds to FIG. 10 (a) to (b) and (d) to (m) are the same as FIGS. 6 (a) to (b) and (d) to (m). FIG. 10C is the same as FIG. 9E.

When the gradation value of the G data is 1, the second partial control data PXg (FIG. 10 (d)) includes one on period in the first sub period PS1. Period color light G is emitted in said one of the on period is T _0. Therefore, the energy of the colored light G guided to the projection optical system 400 during the one on period is T ₀ · W. When the gradation value of the G data is 2, the second partial control data PXg (FIG. 10E) includes one on period in the second sub period PS2. The period during which the colored light G is emitted in the one on period is 2 / T ₀ . Therefore, the energy of the colored light G guided to the projection optical system 400 during the one on period is 2 · T ₀ · W. When the gradation value of the G data is 3, the second partial control data PXg (FIG. 10 (f)) includes two ON periods in the first and second sub-periods PS1 and PS2. . The periods during which the colored light G is emitted during the two ON periods are T ₀ and 2 · T ₀ , respectively. Therefore, the accumulated energy of the colored light G guided to the projection optical system 400 during the two ON periods is 3 · T ₀ · W.

Similarly, when the gradation value of the G data is 269, the second partial control data PXg (FIG. 10 (k)) includes 19 on-periods in 19 sub-periods PS1, PS3 to PS20. including. The accumulated energy of the color light G guided to the projection optical system 400 during the 19 ON periods is 269 · T ₀ · W. When the gradation value of the G data is 270, the second partial control data PXg (FIG. 10 (l)) includes 19 on periods in 19 sub periods PS2 to PS20. The accumulated energy of the color light G guided to the projection optical system 400 during the 19 ON periods is 270 · T ₀ · W. When the gradation value of the G data is 271, the second partial control data PXg (FIG. 10 (m)) includes 20 on periods in 20 sub periods PS1 to PS20. The accumulated energy of the colored light G guided to the projection optical system 400 during the 20 ON periods is 271 · T ₀ · W.

  Note that while FIG. 10 focuses on the color light G emitted from the second light emitting device 110G and the second partial control data PXg, the color light R emitted from the other light emitting devices 110R and 110B is described. , G and the other partial control data PXr, PXb.

  FIG. 11 is an explanatory diagram showing the light intensity in the comparative example and the second embodiment, and corresponds to FIG. FIG. 11 (a) is the same as FIG. 8 (a).

  As can be seen from a comparison of FIGS. 11A and 11B, in this embodiment as well, as in the first embodiment, the intensity of light emitted from each of the light emitting devices 110R, 110G, and 110B can be increased. As a result, the brightness of the image displayed on the screen SC can be increased.

  By the way, in the present embodiment, in the fifth to twentieth sub-periods PS5 to PS20, the period in which light is emitted from the light emitting device 110G is set to be relatively large. On the other hand, in the first to fourth sub-periods PS1 to PS4, the period in which light is emitted from the light emitting device 110G is set to be relatively small.

That is, in the comparative example, the period in which light is emitted from the light emitting device 110G is not suppressed, but in this example, the period in which light is emitted from the light emitting device 110G is the first to fourth sub-periods PS1. It is suppressed in ~ PS4. In other words, in the comparative example, the output rate of the light emitting device 110G is 100%, but in this example, the output rate of the light emitting device 110G is about 85% (= 271 · T ₀ · W / (20 × 16 · T ₀ · W)). As described above, the output rate means the ratio between the energy of light actually output during the G period within one frame period and the energy of light that can be output during the G period within one frame period. .

  However, as described above, also in this embodiment, the intensity of light emitted from each light emitting device 110R, 110G, 110B can be increased. For this reason, also in this embodiment, the light output rate is slightly inferior to that of the comparative example, but the brightness of the image can be considerably increased.

  As described above, also in this embodiment, the gradation of specific color data is emitted from a specific light-emitting device and displayed on the screen SC in 20 specific color periods in the 20 sub-periods PS1 to PS20. It is expressed by the accumulated energy of a specific color light led to However, in this embodiment, the intensity of light emitted from the light emitting device is a constant intensity W. For this reason, the gradation of specific color data can be expressed as the total of the periods during which specific color light is emitted from a specific light emitting device and guided onto the screen SC in the 20 specific color periods.

Then, among the 20 sub-periods PS1 to PS20, a period in which specific color light is emitted from a specific light-emitting device in a specific color period within the four sub-periods PS1 to PS4 (T ₀ , 2 · T ₀ , 4 · T ₀ , 8 · T ₀ ) is longer than a period (16 · T ₀ ) in which specific color light is emitted from a specific light emitting device in a specific color period within the other 16 sub-periods PS5 to PS20. It is set small. That is, a rough gradation is expressed using a period in which specific color light is emitted in a specific color period in the 16 sub-periods PS5 to PS20, and a specific gradation in the four sub-periods PS1 to PS4 is expressed. Fine gradation is expressed using a period in which specific color light is emitted in the color period. Specifically, the gradation of 16 · n (1 ≦ n ≦ 16) is expressed using the light emission period 16 · T ₀ , and the light emission periods T ₀ , 2 · T ₀ , 4 · T ₀ , 8 · using the T _0, the gradation of 15 is expressed. Also with this method, the gradation according to the color data can be appropriately expressed.

  Even if the three light emitting devices 110R, 110G, and 110B and the light modulation device 300 are controlled as in the present embodiment, they are represented by image data (converted image data) as in the first embodiment. Images can be expressed appropriately. Specifically, the gradation corresponding to each color data can be appropriately expressed.

  In particular, also in the present embodiment, the three light emitting devices 110R, 110G, and 110B sequentially emit three color lights in the three color periods PCr, PCg, and PCb in each of the sub periods PS1 to PS20. Therefore, it is possible to set a small light emission period for each light emitting device 110R, 110G, 110B. For this reason, the intensity | strength of the color light inject | emitted per time from each light emitting device 110R, 110G, 110B can be increased, As a result, the brightness of the image displayed can be increased.

  As can be seen from the above description, the four sub-periods PS1 to PS4 in this embodiment correspond to the first type sub-period in the present invention, and the 16 sub-periods PS5 to PS20 correspond to the second sub-period in the present invention. Corresponds to the species sub-period.

C. Light emitting device variations:
In the first and second embodiments, each of the light emitting devices 110R, 110G, and 110B includes a semiconductor laser that emits each color light R, G, and B. Instead, a semiconductor laser that emits infrared light. May be provided.

  In this example, each of the three light emitting devices includes a semiconductor laser that emits infrared light, a wavelength conversion element that utilizes a second harmonic generation (SHG) phenomenon, and a mirror that constitutes an external resonator. ing.

  FIG. 12 is an explanatory view schematically showing current-light intensity characteristics of the light emitting device in the modification. As shown in the drawing, the intensity of light emitted from each light emitting device of this example varies nonlinearly according to the current applied to each light emitting device (more specifically, a semiconductor laser). This is due to the wavelength conversion element. Specifically, as shown in FIG. 3, the intensity of light emitted from the semiconductor laser changes substantially linearly according to the current applied to the semiconductor laser, but the intensity of light emitted from the wavelength conversion element is It changes nonlinearly according to the intensity of light incident on the wavelength conversion element. As a result, the intensity of the light emitted from each light emitting device changes nonlinearly according to the current applied to each light emitting device.

  As can be seen from FIG. 12, the current-light intensity conversion efficiency increases as the current increases. As described above, in each of the first and second embodiments, each light emitting device emits light intermittently. Therefore, the intensity of light emitted from each light emitting device per time can be set to a large value. In other words, the current supplied to each light emitting device per light emission can be set to a large value. For this reason, if the structure of this example is employ | adopted, the intensity | strength of the light inject | emitted from each light emitting device can be increased efficiently.

  The light emitting device of this example is applicable to both the first and second examples. However, in the first embodiment, as described above, the intensity of the color light (for example, the color light G) emitted in the color period (for example, the G period) in the first to fourth sub-periods PS1 to PS4 is the fifth to fourth. It is set smaller than the intensity of the color light emitted in the color period within the twentieth sub-period PS1 to PS20. For this reason, when the light emitting device of this example is applied to the first embodiment, the configuration of the light emitting device control unit 510 is somewhat complicated. Therefore, the light emitting device of this example is preferably applied to the second example in which the intensity of the emitted color light is kept constant.

  The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

(1) In the above embodiment, each of the light emitting devices 110R, 110G, and 110B includes a semiconductor laser that emits different color lights R, G, and B, or a semiconductor laser that emits infrared light. Instead, a light emitting diode (LED) that emits different color lights R, G, and B may be provided.

  In general, each light emitting device only needs to include a semiconductor light emitting element.

(2) In the above embodiment, the projector includes the three light emitting devices 110R, 110G, and 110B that emit three color lights. Instead, one light emission that emits light including three color components. A unit (for example, a mercury lamp, a halogen lamp, or a white LED) and an extraction unit (for example, a filter) that sequentially extracts three color components from the light emitted from the light emitting unit may be provided. That is, in general, the projector only needs to include a light emitting unit that emits a plurality of color lights.

  However, as described above, when the light emitting unit includes a plurality of light emitting devices, as described above, the intensity of the colored light emitted from each light emitting device can be increased. As a result, the brightness of the displayed image can be increased.

(3) In the above embodiment, the maximum emission intensity of each color light R, G, B emitted from each light emitting device 110R, 110G, 110B is set to an equal value (16 · W ₀ ). Instead of this, different values may be set.

(4) In the first embodiment, each frame period PF includes 20 sub-periods PS. However, each frame period may include 40 sub-periods instead. In this case, the intensity of the specific color light emitted from the specific light emitting device during the 40 specific color periods in the 40 sub-periods PS1 to PS40 may be set as follows.

PS1: W ₀ , PS2: 2 · W ₀ , PS3: 4 · W ₀ , PS4 to PS40: 8 · W ₀

  In this case, the converted color data is represented by 304 gradations (9 bits) and can take a value of 0 to 303.

  In the first embodiment, the case where the number of gradations of each color data of the original image data is 256 has been described, but the number of gradations of each color data of the original image data may be another value. For example, when the number of gradations of each color data of the original image data is 1024, each frame period may include 40 sub-periods. In this case, the intensity of the specific color light emitted from the specific light emitting device during the 40 specific color periods in the 40 sub-periods PS1 to PS40 may be set as follows.

_{PS1: W 0, PS2: 2} · W 0, PS3: 4 · W 0, PS4: 8 · W 0, PS5: 16 · W 0, PS6~PS40: 32 · W 0

  In this case, each color data before conversion is expressed by 1024 gradations (10 bits) and can take a value of 0 to 1023, but each color data after conversion is 1152 gradations (11 bits). ) And can take values from 0 to 1151.

In general, it is preferable to express gradation as follows. Let N be the number of sub-periods in one frame period, Na be the number of first-type sub-periods, and Nb be the number of second-type sub-periods. Further, it is assumed that the maximum light emission intensity is 2 ^Na · W ₀ . Of the first type sub-period, the light emission intensity included in the k (1 ≦ k ≦ Na) -th sub-period is represented by 2 ^(k−1) · W ₀ . The emission intensity included in the Nb second type sub-periods is represented by 2 ^Na · W ₀ . At this time, the color data after conversion can take a value of 0 to “2 ^Na −1+ (N−Na) × 2 ^Na (= 2 ⁰ +2 ¹ ... +2 ^(Na−1) + Nb × 2 ^Na )”. , “(N−Na + 1) × 2 ^Na ” gradations are expressed. This number of gradations only needs to be larger than the number of gradations of the color data included in the original image data.

(5) In the second embodiment, each frame period PF includes 20 sub-periods PS, and each of the three color periods PCr, PCg, and PCb included in each sub-period PS has 16 criteria. it includes the time _{T 0.} However, each frame period may include 40 sub-periods, and each of the three color periods included in each sub-period may include eight reference times T ₀ instead. In this case, a light emission period in which specific color light is emitted from a specific light emitting device in 40 specific color periods in the 40 sub-periods PS1 to PS40 may be set as follows.

PS1: T ₀ , PS2: 2 · T ₀ , PS3: 4 · T ₀ , PS4 to PS40: 8 · T ₀

  In this case, the converted color data is represented by 304 gradations (9 bits) and can take a value of 0 to 303.

In the second embodiment, the case where the number of gradations of each color data of the original image data is 256 has been described, but the number of gradations of each color data of the original image data may be another value. For example, when the number of gradations of each color data of the original image data is 1024, each frame period includes 40 sub-periods, and each of the three color periods included in each sub-period is 32. it may contain a number of reference time T _0. In this case, a light emission period in which specific color light is emitted from a specific light emitting device in 40 specific color periods in the 40 sub-periods PS1 to PS40 may be set as follows.

_{PS1: T 0, PS2: 2} · T 0, PS3: 4 · T 0, PS4: 8 · T 0, PS5: 16 · T 0, PS6~PS40: 32 · T 0

  In this case, each color data before conversion is expressed by 1024 gradations (10 bits) and can take a value of 0 to 1023, but each color data after conversion is 1152 gradations (11 bits). ) And can take values from 0 to 1151.

In general, it is preferable to express gradation as follows. Let N be the number of sub-periods in one frame period, Na be the number of first-type sub-periods, and Nb be the number of second-type sub-periods. In addition, it is assumed that 2 ^Na reference times T ₀ are included in each color period. The light emission period included in the k (1 ≦ k ≦ Na) -th sub-period of the first type sub-period is represented by 2 ^(k−1) · T ₀ . The light emission period included in the Nb second type sub-periods is represented by 2 ^Na · T ₀ . At this time, the color data after conversion can take a value of 0 to “2 ^Na −1+ (N−Na) × 2 ^Na (= 2 ⁰ +2 ¹ ... +2 ^(Na−1) + Nb × 2 ^Na )”. , “(N−Na + 1) × 2 ^Na ” gradations are expressed. This number of gradations only needs to be larger than the number of gradations of the color data included in the original image data.

(6) In the second embodiment, in the first to fourth sub-periods PS1 to PS4, the emission period of each color light is assigned to the latter half of the corresponding color period, but instead, it corresponds. It may be assigned to the first half of the color period. Further, in the second embodiment, in the first to fourth sub-periods PS1 to PS4, the end of the light emission period of each color light substantially coincides with the end of the corresponding color period. The start of the light emission period may substantially coincide with the start of the corresponding color period.

  However, if the emission period of each color light is set as in the second embodiment, each color light can be incident on the light modulation element after the modulation state of the light modulation element is sufficiently stabilized. There is an advantage that the gradation value can be expressed more accurately.

(7) In the first and second embodiments, the 20 sub-periods PS1 to PS20 include four first-type sub-periods PS1 to PS4, 16 second-type sub-periods PS5 to PS20, Is included. Then, the four first type sub-periods PS1 to PS4 occur before the 16 second type sub-periods PS5 to PS20. However, instead of this, the four first-type sub-periods may occur after the 16 second-type sub-periods, or may occur in the middle of the 16 second-type sub-periods. May be. Also, the four first type sub-periods PS1 to PS4 are continuously included in the 20 sub-periods PS1 to PS20, but the four first type sub-periods are 20 pieces. It may be included discretely in the sub-period.

(8) In the above embodiment, a micromirror type light modulation device such as DMD is used as the light modulation device, but a transmission type or reflection type liquid crystal panel may be used.

(9) In the above embodiment, a part of the configuration realized by hardware may be replaced with software, and conversely, a part of the configuration realized by software may be replaced by hardware. Also good.

110R, 110G, 110B ... Light emitting device 112 ... Semiconductor laser 114 ... Switching element 116 ... Temperature sensor 200 ... Light guide system 210 ... Optical fiber 220 ... Integrator rod 230, 250 ... Lens 240, 260 ... Mirror 300 ... Light modulation device 400 ... Projection optical system 500... Control circuit 510. Light emitting device controller 511 R, 511 G, 511 B Voltage application circuit 512. Constant voltage source 513 Voltage adjustment circuit 515 Adjusted voltage generation circuit 516 Adder 518 Signal generation circuit 520 Light Modulation device control unit 522 ... gradation conversion unit 524 ... control data generation unit 544 ... timing signal generation unit PJ ... projector PCr, PCg, PCb ... color period PS1-PS20 ... sub period PF ... frame period PX ... pixel control data PXr, PX g, PXb ... Partial control data SC ... Screen WR, WG, WB ... Strength

Claims (6)

A projector,
A light emitting unit for emitting a plurality of colored lights;
A light modulation device that includes a plurality of light modulation elements and modulates the plurality of color lights;
A control unit that controls the light emitting unit and the light modulation device to display an image represented by image data in a frame period;
With
The image data includes a plurality of pixel data, and each pixel data includes a plurality of color data corresponding to the plurality of color lights,
The frame period includes a plurality of sub-periods, and each sub-period includes a plurality of color periods corresponding to the plurality of color lights,
The lengths of the sub-periods are equal to each other, and the lengths of the color periods corresponding to the same colored light respectively included in the plurality of sub-periods are equal to each other.
The controller is
A light emission control unit that sequentially emits the plurality of color lights in the plurality of color periods in each of the sub periods;
The modulation state of the plurality of light modulation elements is controlled according to the plurality of pixel data of the image data, and each of the sub periods according to specific color data corresponding to specific color light included in the pixel data A modulation control unit that controls a modulation state of the light modulation element in a specific color period corresponding to the specific color light included in
With
The plurality of sub-periods are:
A first type of sub-period;
A plurality of second-type sub-periods that are later than the first-type sub-periods;
Contains
The light emission control unit
A period in which the specific color light is emitted from the light emitting unit within the specific color period included in the first type sub-period is included in the specific color period included in each of the second type sub-periods. The specific color light is set to be smaller than the period in which the specific color light is emitted from the light emitting unit, and the specific color light is emitted from the light emitting unit within the specific color period included in each of the second type sub-periods. By setting the period to the same length as the specific color period, the period during which the specific color light is emitted from the light emitting unit in the plurality of second type sub-periods is set to be the same,
The projector which allocates the period when the said specific color light is inject | emitted from the said light emission part in the said 1st type sub period to the second half part of the said specific color period. The projector according to claim 1, wherein
The projector having the same intensity of the specific color light emitted from the light emitting unit in the plurality of sub-periods. The projector according to claim 1 or 2, wherein
The plurality of sub-periods includes a plurality of the first-type sub-periods,
Projectors in which the specific color light is emitted from the light emitting unit in the plurality of first type sub periods. The projector according to any one of claims 1 to 3 ,
The light emitting unit
A projector comprising a plurality of light emitting devices that emit the plurality of color lights. The projector according to claim 4 , wherein
Each of the light emitting devices includes a semiconductor light emitting element. In order to display an image represented by image data in a frame period in a projector including a light emitting unit that emits a plurality of color lights and a light modulation device that includes a plurality of light modulation elements and modulates the plurality of color lights A method for controlling the light emitting unit and the light modulation device,
The image data includes a plurality of pixel data, and each pixel data includes a plurality of color data corresponding to the plurality of color lights,
The frame period includes a plurality of sub-periods, and each sub-period includes a plurality of color periods corresponding to the plurality of color lights,
The lengths of the sub-periods are equal to each other, and the lengths of the color periods corresponding to the same colored light respectively included in the plurality of sub-periods are equal to each other.
The method
(A) causing the light emitting unit to sequentially emit the plurality of color lights during the plurality of color periods within each of the sub-periods;
(B) controlling modulation states of the plurality of light modulation elements according to the plurality of pixel data of the image data, and according to specific color data corresponding to specific color light included in the pixel data, Controlling a modulation state of the light modulation element in a specific color period corresponding to the specific color light included in each sub-period;
With
The plurality of sub-periods are:
A first type of sub-period;
A plurality of second-type sub-periods that are later than the first-type sub-periods;
Contains
The step (a)
A period in which the specific color light is emitted from the light emitting unit within the specific color period included in the first type sub-period is included in the specific color period included in each of the second type sub-periods. The specific color light is set to be smaller than the period in which the specific color light is emitted from the light emitting unit, and the specific color light is emitted from the light emitting unit within the specific color period included in each of the second type sub-periods. Setting the period to be the same length as the specific color period, and setting the same period during which the specific color light is emitted from the light emitting unit in the plurality of second type sub-periods ;
Assigning a period during which the specific color light is emitted from the light emitting unit in the first type sub-period to the second half of the specific color period.

Images