HK1178260B - Projection apparatus, and projection method - Google Patents

Description

Projection device and projection method

Technical Field

The present invention relates to a projection apparatus, a projection method, and a storage medium storing a program, which are suitable for use in, for example, a dlp (digital Light processing) projector or the like.

Background

In recent years, DLP (registered trademark) type projectors are becoming popular.

In this DLP (registered trademark) type projector, the micromirror element reflects light from the projection light source in a direction of the projection optical system for each pixel position for a modulation operation of a time width corresponding to a gray scale, thereby forming an optical image with the entire pixel.

Light that is not reflected in the direction of the projection optical system, so-called "off light (off light)" is irradiated to a predetermined non-reflection portion, converted into heat, and finally emitted to the outside of the housing.

In this way, in DLP (registered trademark) type projectors, how to efficiently release heat closed inside to the outside by "off light" is associated with a stable projection operation, and various proposals have been made in this regard (for example, japanese patent application laid-open No. 2008-292953)

However, in the field of television sets and video recorders, techniques for displaying stereoscopic images are being applied, and projectors are also under study for two-dimensional and three-dimensional stereoscopic projection systems.

Among them, as one of the methods of alternately projecting an image for the left eye and an image for the right eye using 3D (three-dimensional) liquid crystal glasses, a technique is considered in which a field period in which an image of each color of R (red), G (green), and B (blue) is projected is set differently from a field period in which an image of each color of R (red), G (green), and B (blue) is projected for a field period in which higher illuminance, for example, a white synchronization pulse is projected in an extremely short time that cannot be perceived by the naked eye.

In this technique, all of the brighter white light is treated as "off light" except for the timing of projecting the pulse in the field period including the pulse for synchronization and the liquid crystal response time thereafter.

Therefore, in the case of forming a normal optical image, since substantially all brighter light is treated as "off light", as a result, the amount of heat to be emitted is large, and therefore, there is a problem that the heat dissipation unit has to be increased in size.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a projection apparatus, a projection method, and a storage medium storing a program, which can reduce the amount of heat generated when a stereoscopic image is projected.

The projection apparatus of the present invention includes: a plurality of light emitting elements emitting light of different kinds of wavelength bands; a light source driving unit that controls light emission states of the plurality of light emitting elements in accordance with a color image forming period in which a color image is formed by light emitted from the plurality of light emitting elements, a synchronization period in which at least 2 light emitting elements among the plurality of light emitting elements are simultaneously driven and a synchronization signal synchronized with projection timings of a left-eye image and a right-eye image is output, and a light-off period in which all the plurality of light emitting elements are turned off with the synchronization period in between; an input unit that inputs image signals for the left eye and the right eye; and a projection unit configured to project an optical image corresponding to the left-eye image signal and the right-eye image signal input by the input unit by switching between the light beams emitted by the plurality of types of light emitting elements driven by the light source driving unit.

Drawings

Fig. 1 is a diagram showing a projection environment of a data projection apparatus according to embodiment 1 of the present invention.

Fig. 2 is a perspective view showing an external configuration of 3D liquid crystal glasses according to the embodiment.

Fig. 3 is a block diagram showing a schematic configuration of a functional circuit of the data projection apparatus according to the embodiment.

Fig. 4 is a timing chart of light source driving in 3D image projection according to the embodiment.

Fig. 5 is a timing chart of light source driving in 3D image projection with color adjustment according to embodiment 2 of the present embodiment.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings, in which a DLP (registered trademark) type data projection apparatus is applied.

[ embodiment 1 ]

Fig. 1 is a diagram showing a projection environment of a data projection apparatus 10 according to embodiment 1.

As shown in fig. 1, the user US wearing the 3D liquid crystal glasses GL views the image projected from the data projection apparatus 10 to the screen SC.

Fig. 2 is a perspective view showing an external configuration of the 3D liquid crystal glasses GL.

The 3D liquid crystal glasses GL are cover glasses that can be used in a superimposed manner even if the user US is a glasses user, and a light receiving sensor LS is provided on the front side of the nose bridge portion in the center.

When facing the screen SC, the light receiving sensor LS detects a change in luminance on the screen SC surface.

The light is received by the light receiving sensor LS, and the left and right lenses are alternately shielded and transmitted in synchronization with the synchronization signal superimposed on the projection image, so that the user US can view the stereoscopic image.

The configuration of the 3D liquid crystal glasses GL itself has basically the same configuration as that of the existing liquid crystal shutter glasses of the frame sequential system, and therefore, the description of the internal circuit configuration, operation, and the like will be omitted.

Next, a schematic configuration of a functional circuit in the data projection apparatus 10 will be described with reference to fig. 3.

The input unit 11 is constituted by, for example, a contact-jack (RCA) type video input terminal, a D-sub15 type RGB input terminal, and the like.

Analog image signals of various specifications input to the input unit 11 are digitized by the input unit 11, and then sent to the image conversion unit 12 via the system bus SB.

The image conversion unit 12 is also called a "scaler" and unifies the input image data into image data of a predetermined format suitable for projection and sends the image data to the projection processing unit 13.

The projection processing unit 13 performs a drive to be displayed on the micromirror element 14, which is a spatial light modulator, by performing a higher-speed time division drive in which a frame rate according to a predetermined format, for example, 120 (frame/second), the number of divided color components, and the number of display gradations are multiplied, in accordance with the image data transmitted.

A plurality of micromirror elements 14 are arranged in an array, and for example, ON/OFF operations are performed at high speed for each tilt angle of the micromirror of wxga (wide extended Graphic array) (1280 pixels × 800 pixels in horizontal direction) to display an image, and an optical image is formed by the reflected light.

On the other hand, R, G, B of the primary color light is cyclically emitted from the light source section 15 in a time-sharing manner.

The primary color light from the light source 15 is totally reflected by the reflecting mirror 16 and is irradiated to the micromirror element 14.

Then, an optical image is formed by the reflected light of the micromirror element 14, and the formed optical image is displayed on a screen, not shown, as a projection target via the projection lens unit 17.

The light source unit 15 includes an LD (laser diode) 18 that emits blue laser light.

The blue laser beam emitted from the LD18 passes through a dichroic mirror (dichroic mirror) 19 and is then irradiated onto the circumferential surface of the fluorescent wheel 20.

The fluorescent wheel 20 is rotated by a wheel motor (M)21, and a fluorescent layer 20g is formed over the entire circumference of the circumferential surface irradiated with the blue laser beam.

A reflecting plate is provided on the rear surface of the fluorescent wheel 20 on which the fluorescent layer 20g is formed so as to overlap the fluorescent layer 20 g.

A wheel mark (not shown) indicating a reference rotational position for synchronizing with the rotation of the fluorescent wheel 20 is provided at one end of the circumferential surface of the fluorescent wheel 20.

In the present embodiment, the fluorescent wheel 20 is rotated exactly 1 to 360 ° in synchronization with the period of 1 frame of the color image, and at the start timing of the 1 frame, the wheel mark passes through the position of the mark sensor 22 disposed in the vicinity thereof.

The projection processing unit 13 receives the detection output of the marker sensor 22 and detects the rotation state of the fluorescent wheel 20.

The phosphor layer 20g of the phosphor wheel 20 is irradiated with blue laser light, and green light is excited as reflected light.

The green light is reflected by the dichroic mirror 19, passes through the dichroic mirror 23, and reaches the reflecting mirror 16.

The light source unit 15 further includes an LED (light emitting diode) 24 that emits red light and an LED25 that emits blue light.

The red light emitted from the LED24 is reflected by the dichroic mirror 26, further reflected by the dichroic mirror 23, and then reaches the reflecting mirror 16.

The blue light emitted from the LED25 is reflected by the reflecting mirror 27, passes through the dichroic mirror 26, is reflected by the dichroic mirror 23, and reaches the reflecting mirror 16.

As described above, the dichroic mirror 19 transmits blue light, while reflecting green light.

The dichroic mirror 23 transmits green light, and reflects red and blue light.

The dichroic mirror 26 reflects red light and transmits blue light.

The projection processing unit 13 executes, under the control of the CPU28 described later: based on the formation of an optical image by the image display of the micromirror device 14, the light emission of the LD18, the LEDs 24, and 25, the rotation of the fluorescent wheel 20 by the wheel motor 21, and the detection of the rotation timing of the fluorescent wheel 20 by the mark sensor 22 are performed.

The CPU28 controls the overall operation of the above circuits.

The CPU28 is directly connected to the main memory 29 and the program memory 30.

The main memory 29 is formed of, for example, SRAM, and functions as a work memory of the CPU 28.

The program memory 30 is an electrically erasable nonvolatile memory and stores an operation program executed by the CPU28, various kinds of predetermined specification data, and the like.

The CPU28 executes control operations in the data projection apparatus 10 using the main memory 29 and the program memory 30.

The CPU28 executes various projection operations in response to a key operation signal from the operation unit 31.

The operation unit 31 includes a key operation unit provided in the main body of the data projection apparatus 10 and a laser light receiving unit that receives infrared light from a remote controller, not shown, dedicated to the data projection apparatus 10, and directly outputs a key operation signal based on a key operated by a user through the key operation unit of the main body or the remote controller to the CPU 28.

The CPU28 is also connected to the audio processing unit 32 via the system bus SB.

The sound processing unit 32 includes a sound source circuit such as a PCM sound source, and simulates sound data given during a projection operation, and drives the speaker unit 33 to amplify sound or generate a warning sound as necessary.

Next, the operation of the above embodiment will be described.

Although the operations described below are repeated, all the operations described below are performed after the CPU28 expands and stores the operation program, fixed data, and the like read from the program memory 30 in the main memory 29.

For simplicity of explanation, 1 frame of each of the left-eye and right-eye color images is projected in synchronization with 1 cycle (360 °) of the rotation period of the fluorescent wheel 20.

For example, the 1 frame is constituted by 4 fields in total of 3 fields of B (blue), R (red), and G (green) for the synchronization, and the time corresponding to the center angle of 90 ° when the fluorescent wheel 20 rotates is set for each field.

Fig. 4 shows the light emission timing of the light source section 15 and the input level to the light receiving sensor LS of the 3D liquid crystal glasses GL in 2 frames constituting the 3D image 1 frame, that is, the right eye (R) image 1 frame and the left eye (L) image 1 frame.

In the right-eye (R) image frame, at the beginning of the synchronization field, all of LD18, LED24, and LED25, which are semiconductor light emitting elements serving as light sources, are turned off, and from the time when the time d1 has elapsed, LD18, LED24, and LED25 are simultaneously turned on by the projection processing unit 13 for a predetermined pulse width, for example, for a time corresponding to the rotation angle of the fluorescent wheel 20 being 2.

Therefore, the white light mixed by G, R, B is irradiated to the micromirror device 14, and during this time, the micromirror device 14 causes all the light irradiated by the total surface reflection to be reflected light in the direction of the projection lens unit 17.

Therefore, on the screen SC, the entire white high-luminance image is only imperceptible for a very short time by the projection user US.

Thereafter, all of the LD18, the LED24, and the LED25 are turned off until time e1 when the synchronization field is completed again.

The light-off period is a response time for viewing an image for the right eye by opening the liquid crystal shutter of the lens for the right eye next to the 3D liquid crystal glasses GL.

In the next B field, only the LED25 is driven to be turned on for a period corresponding to the rotation angle of the luminescent wheel 20 being 90 °.

The micromirror element 14 forms a blue optical image for the right eye by the blue light emitted from the LED25, and the optical image is projected onto the screen SC by the projection lens unit 17.

In the next R field, only the LED24 is driven to be turned on for a period corresponding to the rotation angle of the luminescent wheel 20 being 90 °.

The micromirror element 14 forms a red optical image for the right eye by the red light emitted from the LED24, and the optical image is projected onto the screen SC by the projection lens unit 17.

In the next G field, only the LD18 is lit for a period corresponding to the rotation angle of the luminescent wheel 20 being 90 °.

The micromirror element 14 forms a green optical image for the right eye by green light obtained by irradiating the phosphor layer 20g of the fluorescent wheel 20 with blue light emitted from the LD18, and the optical image is projected onto the screen SC by the projection lens unit 17.

In the next left-eye (L) image frame, at the beginning of the synchronization field, all of LD18, LED24, and LED25, which are semiconductor light emitting elements serving as light sources, are turned off, and from the time when the time d2 has elapsed, the LD18, LED24, and LED25 are simultaneously turned on by the projection processing unit 13 for a predetermined pulse width, for example, for a time corresponding to the rotation angle of the fluorescent wheel 20 being 2 °.

Therefore, the white light mixed by G, R, B is irradiated to the micromirror device 14, and during this time, the micromirror device 14 makes all the light irradiated by the total reflection be the reflected light toward the projection lens unit 17.

Therefore, the entire screen SC is a white high-luminance image, and is only invisible to the projection user US for a very short time.

Thereafter, at time e2 until the synchronization field is again completed, all of LD18, LED24, and LED25 are turned off.

The light-off period is a response time for viewing the left-eye image by opening the liquid crystal shutter of the left-eye lens next to the 3D liquid crystal glasses GL.

In the next B field, only the LED25 is driven to be lit during a period corresponding to the rotation angle of the luminescent wheel 20 being 90 °.

The micromirror element 14 forms a blue optical image for the left eye by blue light emitted from the LED25, and the optical image is projected onto the screen SC by the projection lens unit 17.

In the subsequent R field, only the LED24 is driven to be turned on during a period corresponding to the rotation angle of the luminescent wheel 20 being 90 °.

The micromirror element 14 forms a red optical image for the left eye by the red light emitted from the LED24, and the optical image is projected onto the screen SC by the projection lens unit 17.

In the next G field, only the LD18 is lit for a period corresponding to the rotation angle of the luminescent wheel 20 being 90 °.

The micromirror element 14 forms a green optical image for the left eye by green light obtained by irradiating the phosphor layer 20g of the fluorescent wheel 20 with blue light emitted from the LD18, and the optical image is projected onto the screen SC by the projection lens unit 17.

The delay time d2 for the first frame is set to a value greater than the same delay time d1 used for the right-eye (R) image frame.

Therefore, the delay time difference Δ D (D2-D1) causes the period T1 to be longer by 2 Δ D than the period T2 in the period T1 from the start of the pulse light emission for synchronization in the right-eye (R) image frame to the start of the pulse light emission for synchronization in the left-eye (L) image frame and in the period T2 from the start of the pulse light emission for synchronization in the left-eye (L) image frame to the start of the pulse light emission for synchronization in the right-eye (R) image frame which is the next 3D image 1 frame.

The 3D glass optical sensor input of fig. 4 is an example of the intensity of light incident on the light receiving sensor LS when the 3D liquid crystal glasses GL are directed to the screen SC in image projection.

In each field B, R, G, the incident light amount becomes an optical image formed by emitting light to each of the monochromatic semiconductor light emitting elements, and for example, the incident light amount becomes higher in the order of B < R < G depending on the luminance of the color component.

In contrast, since the first synchronization pulse of each frame is the amount of light for the mixed color based on the 3-color simultaneous light emission, it is easy to recognize only the synchronization pulse.

By sequentially measuring and comparing the periods T between these synchronization pulses, it is possible to easily determine whether an image for the right eye or an image for the left eye is projected following the synchronization pulses.

In the data projection apparatus 10, in the field including the synchronization pulse, the 3 types of light emitting elements, the LD18, the LED24, and the LED25 are simultaneously caused to emit light only for the period of the synchronization pulse, and in synchronization with the synchronization pulse, the entire surface is displayed in full gray scale by the micromirror element 14, and the light emission is projected onto the screen SC by the projection lens unit 17.

Therefore, there is almost no thermal load due to simultaneous driving of the plurality of light emitting elements in a field including the synchronization pulse, and all the light emitting elements before and after the synchronization pulse are turned off with the synchronization pulse interposed therebetween, so that the amount of heat generation can be simply reduced.

In addition, the temperature of each light emitting element is reduced by turning off the lamp, and the light emission efficiency of each light emitting element can be improved.

[ 2 nd embodiment ]

Hereinafter, embodiment 2 of the present invention will be described.

The projection environment of the data projection apparatus 10 according to the present embodiment is basically the same as that of fig. 1, the external configuration of the 3D liquid crystal glasses GL is basically the same as that of fig. 2, the schematic configuration of the functional circuits in the data projection apparatus 10 is basically the same as that of fig. 3, the same reference numerals are used for the same parts, and the illustration and description thereof are omitted.

Next, the operation of the above embodiment will be described.

Fig. 5 is a timing chart for explaining an operation in the case of adjusting the halftone.

In fig. 4, the boundary between the field for synchronization and the field for color image projection B, G, R is clearly divided, and although the timing of switching the light sources of the respective colors is not mentioned, the adjustment is considered.

That is, in the present embodiment, the LD18, the LED24, and the LED25, which are light source elements for emitting G, R, B color light, are provided separately.

Therefore, by adjusting the width and timing of the light emission period of each element, the dynamic range of luminance and the halftone can be adjusted.

The frame and field configuration of fig. 5 shows the configuration of the frame and field when the 3D image is projected, and the 3D image 1 frame is configured by a right-eye (R) image frame and a left-eye (L) image frame, as in fig. 4.

A period indicated by a broken line in the drawing across a boundary of each field period is referred to as a "Spoke Period (SP) by the name of a DLP (registered trademark) type projector using a general color wheel.

In the present embodiment, in each of the synchronous fields and G, R, B, each element needs to be turned on in addition to the spoke period SP, and the time width and timing of lighting of each light source element in the spoke period can be adjusted.

By performing such adjustment, the dynamic range and halftone expression of each color can be variably set.

In particular, by adjusting the light emission timing of each color in the front-rear direction, the color balance in gray scale expression can be finely adjusted.

The 3D glass optical sensor input of fig. 5 illustrates the intensity of light incident on the light receiving sensor LS when the 3D liquid crystal glasses GL are faced to the screen SC for image projection in a state where the color adjustment is correctly performed.

On the other hand, the timing cannot be accurately adjusted, and variations in light emission timing of each color are considered.

As described above with reference to fig. 4, in a round-trip period between a synchronization field and a subsequent B field, particularly during a period from immediately after the synchronization pulse to the next B field, when none of the light emitting elements is turned off, projection light by light emission is projected via the projection lens unit during the round-trip period, and as a result, a false pulse FP that is exactly similar to the synchronization pulse shown in the 3D glass photosensor input (false) of fig. 5 may be detected by the light receiving sensor LS.

In this case, the 3D liquid crystal glasses GL recognizes the dummy pulse FP as a synchronization pulse to perform ON/OFF control of the left and right liquid crystal shutters, and the 3D image cannot be correctly viewed.

Therefore, as described above with reference to fig. 4, even when the LD18, the LED24, and the LED25 are all reliably turned off at the timing other than the synchronization pulse in the synchronization field and the timing of the next B field is adjusted by being shifted in the forward direction due to an error, the occurrence of the above-described false pulse FP can be reliably avoided, and the 3D liquid crystal glasses GL side can be prevented from erroneously recognizing the projection timing of the 3D image.

[ embodiment 3 ]

In addition, although the above-described embodiments 1 and 2 have described the case where the 3D image is projected, in the case where the two-dimensional image is projected, it is not necessary to alternately project the right-eye image frame and the left-eye image frame as described above.

Therefore, a field including the synchronization pulse may be excluded, and instead, a luminance image in which the luminance of the projection image is increased may be projected.

In this case, the CPU28 recognizes whether the projected image is a two-dimensional image or a 3D image, and switches the projection control using the projection processing unit 13.

In the projection of a two-dimensional image, instead of the synchronization field, a W (white) field may be provided, in which the LD18, the LED24, and the LED25 are all turned on during the field period, and an image corresponding to the luminance signal Y is displayed using the micromirror element 14.

In this case, the luminance signal Y is given by matrix operation.

Y＝0.2988R+0.5868G+0.1144B

In this way, by providing a field for projecting an image for increasing the brightness at the time of projection of a two-dimensional image, the brightness can be increased at the time of projection of a two-dimensional image, and in the case of projection of a 3D image, switching of the projection mode can be easily realized without changing the timing at the time of projection of the original color image.

Further, if the CPU28 switches the projection control using the projection processing unit 13 by recognizing whether the projected image is a two-dimensional image or a 3D image, the user can optimally perform the projection of the two-dimensional image and the projection of the 3D image without switching the projection mode one by one.

According to the present embodiments 1 to 3 described above in detail, driving control of the light emitting elements is performed using a field including a synchronization pulse, and the amount of heat generated during projection of a stereoscopic image can be reduced.

[ 4 th embodiment ]

In the above-described embodiments 1 to 3, a description has been given of a case where 3 types of light emitting elements, such as LD18, LED24, and LED25, are simultaneously turned on at the timings of a synchronization field for 3D image projection and a luminance-increasing field for two-dimensional image projection, and a light source for obtaining white light by mixing these light sources is obtained.

However, the present invention is not limited to this, and for example, 2 types of light emitting elements, that is, LD18 that emits blue light and LED24 that emits red light, may be simultaneously turned on for green light excitation to emit a Ye (yellow) field that is a mixture of these light emitting elements, and the yellow light may be used as a synchronization pulse.

It is important that the input level of the light receiving sensor LS of the 3D liquid crystal glasses GL, which mix a plurality of color lights, is sufficiently higher than that in the case of emitting monochromatic light, and that these can be accurately recognized.

In the above-described embodiment, the description has been given of the case where blue light for green excitation is emitted from the LD18, and red and blue light is emitted from the LEDs 24 and 25.

However, the present invention is not limited to specific light emission colors, light emitting elements, and the like as long as the present invention uses a plurality of types of semiconductor light emitting elements.

For example, the same applies to a system in which a blue LED25 is not provided as a plurality of types of semiconductor light emitting elements that emit light in different wavelength bands from each other, a blue LD and a red LED are provided, a phosphor layer 20G for G and a diffusion plate region that diffuses and transmits blue light are provided as a color wheel, a reflector is arranged at the position of the blue LED25, R light generated by the red LED is generated in a time-sharing manner, and G light and B light generated by the blue LD are used to project a color image.

The present invention is not limited to the above-described embodiments, and various modifications can be made in the implementation stage without departing from the spirit thereof.

Further, the functions performed in the above embodiments may be implemented in combination as appropriate as possible.

The above embodiments include various stages, and various inventions are obtained by appropriate combinations based on a plurality of disclosed constituent elements.

For example, even if several components are reduced from all the components shown in the embodiments, a configuration in which the components are reduced can be obtained as an invention as long as the effect can be obtained.

Claims (5)

1. A projection device is characterized by comprising:

a plurality of light emitting elements emitting light of different kinds of wavelength bands;

a light source driving unit that controls light emission states of the plurality of light emitting elements in accordance with a color image forming period in which a color image is formed by light emitted from the plurality of light emitting elements, a synchronization period in which at least 2 light emitting elements among the plurality of light emitting elements are simultaneously driven and a synchronization signal synchronized with projection timings of a left-eye image and a right-eye image is output, and a light-off period in which all the plurality of light emitting elements are turned off with the synchronization period in between;

an input unit that inputs image signals for the left eye and the right eye; and

a projection unit configured to project an optical image corresponding to the left-eye image signal and the right-eye image signal input by the input unit by switching between the optical images using light emitted from the plurality of types of light emitting elements driven by the light source driving unit;

the light source driving unit controls the light emission states of the plurality of light emitting elements such that a width of a light-off period immediately before a synchronization period corresponding to the left-eye image is different from a width of a light-off period immediately before a synchronization period corresponding to the right-eye image.

2. The projection apparatus according to claim 1,

the light source driving unit adjusts at least one of a width and a timing of driving the various light emitting elements during the color image forming period;

the projection unit adjusts at least one of the width and the timing of a period in which an optical image corresponding to the image signals for the left eye and the right eye input by the input unit is formed and projected, using the light emitted by the plurality of types of light-emitting elements driven by the light source driving unit.

3. The projection apparatus according to claim 1,

a switching unit that switches between projection of the left-eye and right-eye images and projection of the two-dimensional image;

in the case of switching to the projection state of the two-dimensional image by the switching unit, the light source driving unit sets a luminance increasing period for simultaneously driving the plurality of types of light emitting elements, instead of the synchronization period and the light-off period;

when the switching means switches to the projection state of the two-dimensional image, the projection means forms an optical image corresponding to the two-dimensional image for luminance improvement by using the image signal input by the input means during the luminance improvement period, and projects the optical image.

4. The projection apparatus according to claim 3, wherein,

a recognition unit for recognizing whether the projected image is a two-dimensional image or a 3D image;

the light source driving unit performs switching control of the switching unit according to the recognition result of the recognition unit.

5. A projection method of an apparatus using, as a light source, a plurality of light emitting elements that emit light in different types of wavelength bands, the method comprising:

a light source driving step of controlling light emission states of the plurality of light emitting elements in accordance with a color image forming period in which a color image is formed by light emitted from the plurality of light emitting elements, a synchronization period in which at least 2 light emitting elements among the plurality of light emitting elements are simultaneously driven to output a synchronization signal synchronized with projection timings of a left-eye image and a right-eye image, and a light-off period in which all the plurality of light emitting elements are turned off with the synchronization period interposed therebetween;

an input step of inputting image signals for the left eye and the right eye; and

a projection step of switching and projecting an optical image corresponding to the image signal for the left eye and the image signal for the right eye input in the input step, using light emitted from the plurality of types of light emitting elements driven in accordance with the light source driving step;

in the light source driving step, the light emission states of the plurality of types of light emitting elements are controlled so that a width of a light-off period immediately before a synchronization period corresponding to the left-eye image is different from a width of a light-off period immediately before a synchronization period corresponding to the right-eye image.