JP2020034894A - Image projection device - Google Patents

Abstract

To provide an image projection device capable of projecting bright images in a short time while suppressing the occurrence of optical damage in a light source.SOLUTION: An image projection device for projecting images on the basis of input image signals, includes: first light sources 5rd, 5rd that emit first light used for projecting visible images; light source control means 1, 3 that control the driving current to be supplied to the first light sources; and switching means 2 that switches the image projection device between a first state in which visible images are projected on the basis of the image signals and a second state in which no visible images are projected on the basis of image signals. In the second state, the light source control means supply the driving current that is lower than that in the first state and not zero to the first light sources.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image projection device such as a liquid crystal projector.

  2. Description of the Related Art A laser diode (LD) is used as a light source in an image projection apparatus (hereinafter, referred to as a projector) that modulates an image of light emitted from a light source by a light modulation element such as a liquid crystal panel and projects the light on a projection surface such as a screen. There is something. Some of such projectors use a plurality of LDs (blue LD and red LD) that emit light of different wavelengths, as disclosed in Patent Document 1.

  Patent Document 2 discloses a projector that controls a lighting state of a light source according to whether an image signal is input. This projector operates in a projection (normal) mode in which the light source is turned on when an image signal is input, and when no image signal is input, that is, when there is no image to be projected, the light source is turned off to waste power. Switch to non-projection (blank) mode to reduce consumption.

JP 2016-224304 A JP 2003-5147 A

  However, the red LD has a property of easily causing optical damage (COD: Catastrophic Optical Damage) when the temperature is particularly low, as compared with the blue LD. In the projector disclosed in Patent Document 2, when the mode is switched from the blank mode to the normal mode, the red LD is turned on in a state where the temperature of the red LD is low, so that COD may occur. When switching from the blank mode to the normal mode, there is a method of gradually increasing the drive current of the red LD. However, in this method, it takes a long time until the projected image reaches a desired brightness after switching to the normal mode.

  The present invention provides a projector capable of projecting a bright image in a short time after switching from the non-projection mode to the projection mode while suppressing the occurrence of COD in a light source such as a red LD.

  An image projection device according to one aspect of the present invention projects an image based on an input image signal. The image projection device includes a first light source that emits first light used for projecting a visible image, a light source control unit that controls a drive current supplied to the first light source, and a light source control unit that controls the image projection device based on an image signal. Switching means for switching between a first state of projecting a visible image and a second state of not projecting a visible image based on an image signal. In the second state, the light source control unit supplies a drive current lower than the first state and not zero to the first light source.

  A control method according to another aspect of the present invention is applied to an image projection device that projects an image based on an input image signal. The control method includes a step of controlling a drive current supplied to a first light source that emits a first light used for projecting a visible image, and a first step of projecting a visible image based on an image signal by an image projection apparatus. Switching to a second state in which a visible image is not projected based on the state and the image signal. In the second state, a drive current lower than the first state and not zero is supplied to the first light source.

  Note that a computer program that causes a computer of the image projection apparatus to execute a process according to the above control method also constitutes another aspect of the present invention.

  According to the present invention, generation of COD in the first light source can be suppressed, and a bright image can be projected in a short time after switching from the second state to the first state.

FIG. 1 is a diagram illustrating a configuration of a projector that is Embodiment 1 of the present invention. 5 is a flowchart illustrating processing performed by the projector according to the first embodiment. 9 is a flowchart illustrating processing performed by the projector according to the second embodiment of the present invention. FIG. 9 is a diagram illustrating a configuration of a projector that is Embodiment 3 of the present invention. 9 is a flowchart illustrating processing performed by the projector according to the third embodiment. 9 is a flowchart illustrating processing performed by a projector that is Embodiment 4 of the present invention. 9 is a flowchart illustrating processing performed by a projector that is Embodiment 5 of the present invention. FIG. 13 is a diagram illustrating a configuration of a projector that is Embodiment 6 of the present invention. 13 is a flowchart illustrating processing performed by a projector that is Embodiment 6 of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration of a projector as an image projection device according to a first embodiment of the present invention. In the following description, R, G, and B mean red, green, and blue, respectively. 1 is a system control unit, 2 is a mode switching unit, 3 is a drive current calculation unit, and 4 is a light source drive unit. 5ba and 5bb are B light sources, and 5rc and 5rd are R light sources. 6b is a heat sink for the B light source, 6r is a heat sink for the R light source, 7b is a cooling unit for the B light source, 7r is a cooling unit for the R light source, and 8 is a cooling control unit.

  9ba and 9bb are B collimating lenses, and 9rc and 9rd are R collimating lenses d. Reference numeral 10 denotes a first lens, 11 denotes a second lens, 13 denotes a light reflecting member, 14 denotes a glass plate, and 15 denotes a third lens. 16 is a phosphor (wavelength conversion element), 17 is a phosphor support member, 18 is a motor, and 19 is a motor control unit. 21a is a first fly-eye lens, 21b is a second fly-eye lens, 22 is a polarization conversion element, and 23 is a fourth lens.

  24 is a dichroic mirror, 25 is a wavelength-selective phase plate, 26RB is a RB polarizing beam splitter, 26G is a G polarizing beam splitter, 27R is a λ / 4 plate for R, 27G is a λ / 4 plate for G, and 27B is B Λ / 4 plate. 28R is a light modulation unit for R, 28G is a light modulation unit for G, and 28B is a light modulation unit for B. Reference numeral 30 denotes a color combining prism, and 32 denotes a projection lens.

  The drive current calculation unit 3 calculates drive currents of the B light sources 5ba and 5bb and the R light sources 5rc and 5rd according to an instruction from the system control unit 1. The light source drive unit 4 supplies each drive current calculated by the drive current calculation unit 3 to each light source to drive it. The system control unit 1 and the drive current calculation unit 3 constitute a light source control unit.

  The B light sources (second light sources) 5ba and 5bb are configured using the same semiconductor laser diodes that emit B light (blue light). The peak wavelength of the B light sources 5ba and 5bb is, for example, 455 nm. The R light sources (first light sources) 5rc and 5rd are configured using the same semiconductor laser diodes that emit R light (red light: first light). The peak wavelength of the R light sources 5rc and 5rd is, for example, 635 nm. The B light sources 5ba, 5bb are attached to a B light source heat sink 6b. The R light sources 5rc and 5rd are attached to an R light source heat sink 6r as a heat transfer member. As each heat sink, a copper plate or the like provided with a radiation fin is used. It is preferable that each light source and each heat sink be in close contact with a heat transfer member such as a heat conductive sheet. In addition, the number of each of the B light source and the R light source may not be two.

  On the back of the heat sink 6b for the B light source and the heat sink 6r for the R light source, a cooling unit for a B light source (hereinafter referred to as a cooling fan for a B light source) 7b and a cooling unit for an R light source (cooling means: , R light source cooling fan) 7r.

  The cooling air from each of the B light source cooling fan 7b and the R light source cooling fan 7r cools the B light source heat sink 6b and the R light source heat sink 6r. The rotation speeds (fan rotation speeds) of the cooling fan 7b for the B light source and the cooling fan 7r for the R light source are controlled by the cooling control unit 8 based on an instruction from the system control unit 1. Increasing the drive voltage of each cooling fan increases the fan rotation speed, and decreasing the drive voltage decreases the fan rotation speed. The system control unit 1 and the cooling control unit 8 constitute a cooling control unit. In FIG. 1, the directions of the arrows protruding from the cooling fan 7b for the B light source and the cooling fan 7r for the R light source indicate the direction of the cooling air.

  The B light source heat sink 6b and the R light source heat sink 6r average the heat generated by the B light sources 5ba and 5bb and the heat generated by the R light sources 5rc and 5rd, respectively. By cooling the B light source heat sink 6b and the R light source heat sink 6r with the B light source cooling fan 7b and the R light source cooling fan 7r, respectively, the B light sources 5ba and 5bb and the R light sources 5rc and 5rd can be simultaneously cooled. .

  The B light emitted from the B light sources 5ba, 5bb respectively enter the B collimating lenses 9ba, 9bb. The R lights emitted from the R light sources 5rc and 5rd enter the R collimating lenses 9rc and 9rd, respectively. Each collimating lens converts light from each light source into substantially parallel light. The direction of the arrow from each light source in FIG. 1 indicates the optical path and traveling direction of the light. This is the same in the subsequent optical paths.

  Light emitted from each collimating lens enters the first lens 10 and the second lens 11 and is emitted as excitation light 12. The first lens 10 and the second lens 11 have a role of adjusting the beam diameter of light emitted from each collimating lens.

  The excitation light 12 is reflected by the light reflecting member 13 provided on the surface of the glass plate 14 and irradiates the phosphor 16 via the third lens 15. The light reflecting member 13 is provided only on a portion of the surface of the glass plate 14 where the excitation light 12 is irradiated. Further, the third lens 15 condenses the excitation light 12 to form a light irradiation area of a predetermined size on the phosphor 16.

  The material of the phosphor 16 is, for example, YAG: Ce. The phosphor 16 is provided in a circumferential direction around the rotation axis of the motor 18 and is supported by a phosphor support member 17. The material of the phosphor support member 17 is typically a metal plate such as aluminum. However, it is not limited to a metal plate as long as it has the same function as the metal plate. The motor 18 rotates the phosphor 16 and the phosphor support member 17 in order to efficiently radiate heat from the phosphor 16. The rotation speed of the motor 18 is controlled by the motor control unit 19 in accordance with an instruction from the system control unit 1.

  The phosphor 16 converts the wavelength of a part of the B light in the excitation light 12 to generate yellow fluorescent light. The fluorescent light, the excitation light of B (non-converted light) that has not been wavelength-converted by the phosphor 16 and the R light are combined to generate the illumination light 20 as white (W) light.

  The illumination light 20 enters the third lens 15 and is converted into substantially parallel light. The illumination light 20 transmitted through the third lens 15 is further transmitted through a portion of the glass plate 14 other than the light reflecting member 13, and transmitted through the first fly-eye lens 21a and the second fly-eye lens 21b. Is split into a plurality of light beams and enters the polarization conversion element 22. The polarization conversion element 22 converts the illumination light 20 that is unpolarized light into linearly polarized light having one specific polarization direction. Generally, the light beam from the LD is linearly polarized light, but the illumination light 20 from the phosphor 16 is unpolarized light. For this reason, in order to efficiently perform the polarization separation by the polarization beam splitter described later, the light is converted into linearly polarized light (S-polarized light having a polarization direction perpendicular to the paper surface of FIG. 1) by providing the polarization conversion element 22.

  The plurality of light beams as the illumination light 20 emitted from the polarization conversion element 22 are condensed by the fourth lens 23 and are superimposed on the three light modulating units (light modulating means) 28R, 28G, 28B. Thereby, each light modulator is uniformly illuminated. As described below, the R light, the G light, and the B light separated from the illumination light 20 correspond to the third light.

  The illumination light 20 transmitted through the fourth lens 23 is guided to the dichroic mirror 24. The dichroic mirror 24 reflects the RB light 20RB of the illumination light 20 and transmits the G light 20G. The S-polarized G light 20G transmitted through the dichroic mirror 24 is incident on the G polarization beam splitter 26G, is reflected by the polarization splitting surface, and reaches the G light modulation unit 28G. Here, the G light modulation section 28G is a digitally driven reflective liquid crystal display element, and forms an original image for modulating the G light 20G. The system control unit 1 as a modulation control unit drives the G light modulation unit 28G to form an original image based on a video signal (image signal) input from the outside. At this time, the system control unit 1 drives each pixel of the G light modulation unit 28G ON / OFF during each frame period, and controls the duty of the ON / OFF drive to control the G light modulation unit 28G. Is expressed. The same applies to the R light modulation unit 28R and the B light modulation unit 28B.

  The G light modulator 28G modulates and reflects the G light 20G according to the original image. Thus, the modulated light 29G is emitted from the G light modulator 28G. The S-polarized light component of the modulated light 29G is reflected by the polarization splitting surface of the G polarization beam splitter 26G, returned to the light source side, and removed from the projection light. On the other hand, the P-polarized light component of the modulated light 29G passes through the polarization splitting surface of the G polarization beam splitter 26G. At this time, in a state where all the polarization components are converted into S-polarized light (hereinafter, referred to as an all black display state), the slow axis or the fast axis of the λ / 4 plate 27G is changed to the incident optical axis to the G polarizing beam splitter 26G. And the direction perpendicular to the plane containing the reflected optical axis. Accordingly, it is possible to suppress the influence of the disorder of the polarization state generated in the G polarization beam splitter 26G and the G light modulation unit 28G. The modulated light 29G emitted from the G polarization beam splitter 26G enters the color combining prism 30.

  The RB light 20 RB reflected by the dichroic mirror 24 enters the wavelength-selective phase plate 25. The wavelength-selective phase plate 25 converts the R light into P-polarized light by rotating its polarization direction by 90 degrees, and transmits the B light as S-polarized light without rotating its polarization direction. The RB light 20RB transmitted through the wavelength-selective phase plate 25 enters the RB polarizing beam splitter 26RB.

  The RB polarization beam splitter 26RB transmits the P light R light 20R and reflects the S light B light 20B. The R light 20R transmitted through the polarization splitting surface of the RB polarization beam splitter 26RB is modulated and reflected by the R light modulation unit 28R and emitted as modulated light 29R. The P-polarized light component of the modulated light 29R passes through the polarization splitting surface of the RB polarization beam splitter 26RB, returns to the light source side, and is removed from the projection light. On the other hand, the S-polarized light component of the modulated light 29 </ b> R is reflected by the polarization splitting surface of the RB polarization beam splitter 26 RB and enters the color combining prism 30.

  The B light 20B reflected by the polarization splitting surface of the RB polarization beam splitter 26RB is modulated and reflected by the B light modulation unit 28B to become a modulated light 29B. The S-polarized light component of the modulated light 29B is reflected by the polarization splitting surface of the RB polarization beam splitter 26RB, returned to the light source side, and removed from the projection light. On the other hand, the P-polarized light component of the modulated light 29B passes through the polarization splitting surface of the RB polarization beam splitter 26RB and enters the color combining prism 30. At this time, by adjusting the slow axes of the λ / 4 plates 27R and 27B in the same manner as in the G λ / 4 plate 27G, it is possible to adjust each of the R and B full black display states. The RB light 29RB thus combined into one light beam and emitted from the RB polarizing beam splitter 26RB enters the color combining prism 30.

  The color synthesis prism 30 transmits the RB light 29RB and reflects the G light 29G to combine them to generate projection light 31. The projection light 31 is enlarged and projected through a projection lens 32 onto a projection surface (not shown) such as a screen. Thereby, a color image is displayed as a projection image. The optical path shown in FIG. 1 is when the projector is displaying an all-white image. Also in the following embodiments, it is assumed that the projector displays an all-white image unless otherwise specified.

  The mode switching unit (switching means) 2 switches the mode of the projector in the operation state where the power is turned on between the normal mode (first state) described below and the blank mode. In this embodiment, the mode switching unit 2 is provided in the system control unit 1, but may be provided separately from the system control unit 1. The normal mode is a projection mode for projecting a visible image based on an image signal input to the projector. A visible image is an image formed by light having a wavelength shorter than 700 nm. However, the upper limit of the wavelength used for the visible image is not limited to this.

  On the other hand, the blank mode is one of the non-projection modes in which an image is not projected when no image signal is input to the projector. However, by inputting a black image signal during the blank mode, a state equivalent to non-projection may be set regardless of whether the light source is turned on or off. Further, the projector of the present embodiment is different from the blank mode in that even when an image signal is input to the projector, a mode in which the image is not projected when the user instructs not to project the image based on the image signal temporarily. Have. The mode in which image projection is not performed and the blank mode according to the user instruction correspond to the non-projection mode (second state).

  The flowchart in FIG. 2 illustrates a light source control process (control method) performed by the system control unit 1 (and the drive current calculation unit 3) in the present embodiment. The system control unit 1 executes this processing according to a computer program. In the following description, “S” means a step. The same applies to other embodiments described later.

  When the power of the projector is turned on (ON) in S1, the system control unit 1 performs a startup process in S2. The start-up process is a process for performing settings necessary for the projector to project an image, and for waiting until the temperature of elements inside the projector is stabilized.

  Next, in S3, the system control unit 1 determines whether or not the blank mode is set and whether or not the user has issued a non-projection instruction through an operation unit (not shown). However, the blank mode may be selectable between setting and non-setting, or may always be set. The system control unit 1 proceeds to S4 when the blank mode is set or when a non-projection instruction is given by the user, and otherwise proceeds to S8.

  In S4, the system control unit 1 determines whether or not an image signal has been input from outside the projector. If the image signal has been input, the process proceeds to S5. If the image signal has not been input, the process proceeds to S11. move on. If a non-projection instruction is given by the user, the process proceeds to S11 regardless of the presence or absence of an input image signal.

  In S5, the mode switching unit 2 in the system control unit 1 sets the mode of the projector to the normal mode.

  Next, in S6, the system control unit 1 causes the drive current calculation unit 3 to calculate a normal mode drive current as a drive current for the R light sources 5rc and 5rd. The normal mode drive current is a drive current for obtaining the light emission amount (light output) of the R light sources 5rc and 5rd suitable for projecting an image based on the input image signal. In addition, the system control unit 1 supplies the drive current calculation unit 3 with the B light sources 5ba and 5bb with the light emission amounts (light amount) of the B light sources 5ba and 5bb suitable for projecting an image based on the input image signal. Output) is calculated.

  Next, in S7, the system control unit 1 causes the light source drive unit 4 to supply the normal mode drive current calculated by the drive current calculation unit 3 in S6 to the R light sources 5rc and 5rd and the B light sources 5ba and 5bb.

  Then, in S8, the system control unit 1 determines whether or not there is a command to turn off (turn off) the power of the projector. If there is a command to turn off the power, the process proceeds to S9, and if not, to S3. Return.

  In S9, the system control unit 1 performs a projector shutdown process. The shut-down process includes a setting process of the projector, a saving process of the lighting history of each light source, presence / absence of abnormality, and the like.

  Then, in S10, the system control unit 1 turns off the power of the projector.

  On the other hand, in S11, the mode switching unit 2 sets the mode of the projector to the blank mode.

  Next, in S12, the system control unit 1 causes the drive current calculation unit 3 to set a drive current for the blank mode determined in advance by the system control unit 1 according to a program as the drive current for the R light sources 5rc and 5rd. The blank mode drive current is a current that is lower than the normal mode drive current and is not zero. The drive current for the blank mode is obtained by increasing the temperature of the R light sources 5rc and 5rd in order to raise the drive current for the R light sources 5rc and 5rd to the drive current for the normal mode in a short time when an image signal is input in the blank mode. Is to keep it higher than when it is not supplied.

  This is because if a high drive current is applied to the R light source while the temperature of the R light source is low, the risk of COD occurring in the R light source increases. In the blank mode, a blank mode drive current lower than the normal mode drive current is supplied to the R light source, and the R light source is weakly lit and warmed. As a result, the risk of COD occurring in the R light source that has been switched from the blank mode to the normal mode and supplied with the normal mode drive current can be reduced. Moreover, since the R light source is already warmed at the time of switching to the normal mode, it is possible to shorten the time until the supply of the normal mode drive current is permitted.

  The drive current for the blank mode is lower than the drive current for the normal mode as described above. In addition, it is preferable that the blank mode drive current is set so that unnecessary R light is not emitted outside the projector in the blank mode. . For example, the blank mode drive current is desirably set to a current at which the R light source emits LD light and is smaller than a current at which the R light source emits LD.

  In the blank mode, the system control unit 1 may supply a non-zero drive current to the B light sources 5aa and 5ab, which is lower than that in the normal mode similarly to the R light sources 5rc and 5rd. The supply of the drive current to 5aa and 5ab may be stopped.

  Next, in S13, the system control unit 1 causes the light source drive unit 4 to supply the blank mode drive current set by the drive current calculation unit 3 in S12 to the R light sources 5rc and 5rd. Thereafter, the system control unit 1 returns to S3.

  In the present embodiment, by turning on the R light source weakly in the blank mode and warming it, it is possible to suppress the occurrence of COD in the R light source when switching to the normal mode, and further project a bright image in the normal mode. It is possible to shorten the time until the operation can be performed.

  Next, a second embodiment of the present invention will be described. The configuration of the projector according to the present embodiment is the same as that of the projector according to the first embodiment (FIG. 1), and the same components as those in the first embodiment are denoted by the same reference numerals.

  The flowchart of FIG. 3 shows a light source control process performed by the system control unit 1 (and the drive current calculation unit 3) in the present embodiment. The processing from S1 to S13 is the same as in the first embodiment (FIG. 2).

  When the blank mode drive current is supplied to the R light sources 5rc and 5rd in S13, the system control unit 1 controls the R light modulation unit 28R so that the R light is not guided to the projection lens 32 in S20. Specifically, the R light modulator 28R is driven such that the R light 20R incident on the R light modulator 28R is reflected as P-polarized light. The P-polarized light reflected by the R light modulator 28R passes through the RB polarization beam splitter 26RB, and is not guided to the projection lens 32 and is not projected on the projection surface. Thereafter, the system control unit 1 returns to S3.

  In the present embodiment, since the R light from the R light source that is weakly lit during the blank mode is not guided to the projection lens 32, it is possible to prevent unnecessary R light from being projected onto the projection surface.

  In the present embodiment, an example has been described in which the R light modulator 28R reflects the R light 20R as P-polarized light in the blank mode. However, even if the reflected light from the R light modulator 28R is not completely P-polarized light, it is possible to make the R light projected on the projection surface inconspicuous. The R light modulation unit 28R may be controlled to include this. That is, the R light modulator 28R may be controlled so that the R light attenuated in the normal mode is guided to the projection lens 32.

  Next, a third embodiment of the present invention will be described. FIG. 4 illustrates a configuration of a projector according to the third embodiment. The projector of this embodiment has a configuration in which a shutter 33 is added to the projector of the first embodiment (FIG. 1).

  The shutter 33 is provided between the fourth lens 23 and the dichroic mirror 24, that is, on an optical path toward the light modulators 28R, 28G, and 28B. The shutter 33 originally has a role of blocking a part of the illumination light 20 and adjusting the amount of light incident on each light modulation unit for the purpose of improving the contrast of the projected image. The shutter 33 adjusts the light amount of the illumination light 20 by an opening and closing operation, but a shutter having another function having the same function may be used. The drive of the shutter 33 is controlled by the system control unit 1 as a shutter control unit.

  The flowchart in FIG. 5 illustrates the light source control processing performed by the system control unit 1 (and the drive current calculation unit 3) in the present embodiment. The processing from S1 to S13 is the same as in the first embodiment (FIG. 2). In the normal mode, the system control unit 1 drives the shutter 33 to open (open the optical path to illuminate the light modulation unit).

  When the drive current for blank mode is supplied to the R light sources 5rc and 5rd in S13, the system control unit 1 controls the shutter 33 in S30 so that the R light is not projected on the projection surface. Specifically, driving is performed so as to close the shutter 33 (block the optical path so as not to illuminate the light modulation unit). The control of the R light modulator 28R described in S20 of the second embodiment may be performed together with the closing drive of the shutter 33.

  Also in the present embodiment, since the R light from the R light source that is weakly lit during the blank mode is not guided to the projection lens 32, unnecessary R light can be prevented from being projected onto the projection surface.

  In the present embodiment, an example in which the shutter 33 completely blocks the illumination light 20 has been described. However, even if the shutter 33 does not completely block the illumination light 20, it is possible to make the R light projected on the projection surface inconspicuous, so that the shutter 33 may be slightly opened.

  Note that the shutter 33 may be provided on an optical path that is emitted from the light modulation unit and that is directed toward the projection surface.

  Next, a fourth embodiment of the present invention will be described. The configuration of the projector according to the present embodiment is the same as that of the projector according to the first embodiment (FIG. 1), and the same components as those in the first embodiment are denoted by the same reference numerals.

  The flowchart in FIG. 6 illustrates a light source control process performed by the system control unit 1 (and the drive current calculation unit 3) in the present embodiment. The processing from S1 to S13 is the same as in the first embodiment (FIG. 2).

  When the drive current for the blank mode is supplied to the R light sources 5rc and 5rd in S13, the system control unit 1 programs the rotation speed (fan rotation speed) of the R light source cooling fan 7r in advance in S40. Is controlled to the blank mode rotation speed determined in accordance with the above. Specifically, the system controller 1 cools the R light sources 5rc and 5rd more than in the normal mode in order to increase the temperature of the R light sources 5rc and 5rd as much as possible by supplying a blank mode drive current lower than the normal mode drive current. The rotation speed of the R light source cooling fan 7r is set low so that Thereafter, the system control unit 1 returns to S3.

  The processing of S20 of the second embodiment or the processing of S30 of the third embodiment may be performed between S13 and S40.

  In this embodiment, by setting the rotation speed of the cooling fan 7r for the R light source in the blank mode to be lower than the rotation speed in the normal mode, the temperatures of the R light sources 5rc and 5rd tend to rise. As a result, it is possible to suppress the occurrence of COD in the R light sources 5rc and 5rd when switching to the normal mode, and to further shorten the time until a bright image can be projected in the normal mode. Further, since the number of rotations of the cooling fan 7r for the R light source is low, noise can be reduced.

  Next, a fifth embodiment of the present invention will be described. The configuration of the projector according to the present embodiment is the same as that of the projector according to the first embodiment (FIG. 1), and the same components as those in the first embodiment are denoted by the same reference numerals.

  The flowchart of FIG. 7 shows a light source control process performed by the system control unit 1 (and the drive current calculation unit 3) in the present embodiment. The processing from S1 to S13 is the same as in the first embodiment (FIG. 2).

  When the drive current for blank mode is supplied to the R light sources 5rc and 5rd in S13, the system control unit 1 controls the rotation speed (motor rotation speed) of the motor 18 in advance via the motor control unit 19 in S50. The unit 1 controls the rotation speed for the blank mode determined according to the program. Specifically, the system control unit 1 sets a blank mode rotation speed lower than the normal mode rotation speed of the motor 18. This is to reduce noise caused by rotation of the motor 18 in the blank mode. The system control unit 1 and the motor control unit 19 constitute a motor control unit.

  If the effect of heat generated by the phosphor 16 or the phosphor support 17 absorbing a part of the R light from the R light sources 5rc and 5rd can be ignored, the rotation of the motor 18 may be stopped. Thereafter, the system control unit 1 returns to S3.

  The processing of S20 of the second embodiment, the processing of S30 of the third embodiment, and the processing of S40 of the fourth embodiment may be performed between S13 and S50.

  In S50, the system control unit 1 changes the rotation speed of the motor 18 to the rotation speed for the blank mode, and then completes the processing in S6 and S7 in the normal mode switched in S5, and then performs the processing in S60. In S60, the system control unit 1 changes the rotation speed of the motor 18 via the motor control unit 19 to the normal mode rotation speed determined in advance by the system control unit 1 according to a program. Then, the process proceeds to S8.

  In the present embodiment, when the mode is switched from the blank mode to the normal mode, before the rotation speed of the motor 18 is controlled to the normal mode rotation speed in S60, the normal mode drive current is supplied to the R light sources 5rc and 5rd in S7. Start supplying. The time from the start of supply of the normal mode drive current to the R light sources 5rc and 5rd to the stabilization of the light output of the R light sources 5rc and 5rd is required until the rotation speed of the motor 18 is stabilized at the normal mode rotation speed. Longer than time. For this reason, by starting supply of the normal mode drive current to the R light sources 5rc and 5rd before changing the rotation speed of the motor 18 to the normal mode rotation speed, a bright image is projected after switching to the normal mode. The time it takes to complete.

  Next, a sixth embodiment of the present invention will be described. FIG. 8 shows a configuration of a projector as an image projection device according to a sixth embodiment of the present invention. The projector according to the present embodiment is different from the projector according to the first embodiment (FIG. 1) in that an IR (Infrared) light source 5i, an IR light source heat sink 6i, an IR light source cooling unit 7i, an IR collimating lens 9i, and an IR light 20i. And a light combining unit 34.

  The IR light source 5i is configured using a light emitting diode that emits IR light. The peak wavelength of the IR light source 5i is, for example, 800 nm. The IR light source 5i is attached to an IR light source heat sink 6i. As the heat sink, a copper plate or the like provided with a radiation fin is used. It is preferable that the IR light source and the heat sink for the IR light source are adhered to each other by a heat transfer member such as a heat conductive sheet. Note that the number of IR light sources need not be one.

  An IR light source cooling unit 7i configured by a cooling fan is disposed on the back surface of the IR light source heat sink 6i. The cooling heat from the cooling fan 7i for the IR light source cools the heat sink 6i for the IR light source. The rotation speed (fan rotation speed) of the IR light source cooling fan 7 i is controlled by the cooling control unit 8 based on an instruction from the system control unit 1. Increasing the drive voltage of the cooling fan increases the fan speed, and decreasing the drive voltage decreases the fan speed. The system control unit 1 and the cooling control unit 8 constitute a cooling control unit. In FIG. 8, the direction of the arrow coming out of the cooling fan 7i for the IR light source indicates the direction of the cooling air. The IR light emitted from the IR light source 5i enters the IR collimating lens 9i. The IR collimating lens converts light from the IR light source into substantially parallel light.

  The IR light 20i emitted from the IR collimating lens enters the light combining unit 34 and is reflected in the direction of the first fly-eye lens 21a. Here, the light combining section 34 is a flat glass, and is designed to transmit the illumination light 20 and reflect the IR light 20i.

  The IR light 20i reflected by the light combining unit 34 subsequently travels on the same optical path as the G light 20G. The dichroic mirror 24 transmits the IR light 20i. The IR light 20i transmitted through the dichroic mirror 24 is incident on the G polarization beam splitter 26G, is reflected on the polarization separation surface, and reaches the G light modulation unit 28G. The G light modulator 28G modulates and reflects the IR light 20i according to the original image. As a result, the modulated IR light is emitted from the G light modulator 28G. The S-polarized light component of the modulated IR light is reflected by the polarization splitting surface of the G polarization beam splitter 26G, returned to the light source side, and removed from the projection light.

  On the other hand, the P-polarized light component of the modulated IR light passes through the polarization splitting surface of the G polarization beam splitter 26G. The modulated IR light emitted from the G polarizing beam splitter 26G enters the color combining prism 30. The modulated IR light is reflected by the color combining prism 30 and is enlarged and projected through a projection lens 32 onto a projection surface (not shown) such as a screen. Thus, an IR image is displayed as a projection image. The projected IR image can be viewed through a viewer or the like that converts IR light into visible light.

  The mode switching unit (switching means) 2 switches the mode of the projector in the power-on operating state between a normal mode (first state) and an IR mode (second state) described below. In this embodiment, the mode switching unit 2 is provided in the system control unit 1, but may be provided separately from the system control unit 1. The normal mode is a projection mode in which an image (visible image) is projected using an R light source, a B light source, and fluorescent light based on an image signal input to the projector. On the other hand, the IR mode is a projection mode in which an image (IR image) is projected using an IR light source based on an image signal input to the projector. The IR image can be visually recognized using goggles that convert infrared light into visible light.

  The flowchart in FIG. 9 illustrates a light source control process (control method) performed by the system control unit 1 (and the drive current calculation unit 3) in the present embodiment. The system control unit 1 executes this processing according to a computer program. The processes from S1 to S2 and S5 to S10 are the same as those in the first embodiment (FIG. 2).

  In S14 after S2, the system control unit 1 determines which of the normal mode and the IR mode is set. The system control unit 1 proceeds to S5 when the normal mode is set, and proceeds to S15 when the IR mode is set.

  In S15, the mode switching unit 2 in the system control unit 1 sets the mode of the projector to the IR mode.

  Next, in S16, the system control unit 1 causes the drive current calculation unit 3 to calculate a drive current for the IR mode as a drive current for the R light sources 5rc, 5rd and the IR light source 5i. The driving current for the IR mode is a driving current for obtaining a light emission amount (light output) of the IR light source 5i suitable for projecting an image based on the input image signal. The system control unit 1 causes the drive current calculation unit 3 to set a drive current for the IR mode determined in advance by the system control unit 1 according to a program as the drive current for the R light sources 5rc and 5rd. The drive current for the IR mode is lower than the drive current for the normal mode and is not zero. The drive current for the IR mode is obtained by raising the temperature of the R light sources 5rc and 5rd in order to increase the drive current for the R light sources 5rc and 5rd to the drive current for the normal mode in a short time when an image signal is input in the IR mode. Is to keep it higher than when it is not supplied.

  This is because if a high drive current is applied to the R light source while the temperature of the R light source is low, the risk of COD occurring in the R light source increases. In the IR mode, a drive current for the IR mode lower than the drive current for the normal mode is supplied to the R light source, and the R light source is weakly lit and warmed. As a result, the risk of COD occurring in the R light source to which the normal mode drive current is supplied after switching from the IR mode to the normal mode can be reduced. Moreover, since the R light source is already warmed at the time of switching to the normal mode, it is possible to shorten the time until the supply of the normal mode drive current is permitted.

  The drive current for the IR mode is lower than the drive current for the normal mode as described above. In addition, it is preferable that the IR mode drive current is set so as not to emit unnecessary R light outside the projector in the IR mode. . For example, the drive current for the IR mode is desirably set to a current at which the R light source emits LD light and is smaller than a current at which the R light source emits LD light.

  In the IR mode, the system control unit 1 may supply a non-zero driving current to the B light sources 5aa and 5ab to the B light sources 5aa and 5ab, which is lower than that in the normal mode, like the R light sources 5rc and 5rd. The supply of the drive current to 5aa and 5ab may be stopped.

Next, in S17, the system control unit 1 causes the light source driving unit 4 to supply the IR mode drive current calculated by the drive current calculation unit 3 in S16 to the R light sources 5rc, 5rd, and the IR light source 5i.
Thereafter, the system control unit 1 returns to S14.

  In this embodiment, by turning on the R light source weakly in the IR mode and warming it, it is possible to suppress the occurrence of COD in the R light source when switching to the normal mode, and to project a bright image in the normal mode. It is possible to shorten the time until the operation can be performed.

  As described in the previous embodiment, the R light modulator is controlled to reduce the ratio of the amount of light emitted from the projection lens 32 to the amount of light emitted from the red light source during the IR mode. Alternatively, a separate shutter may be provided for control.

  In each of the above-described embodiments, the case where both the cooling unit for the B light source 6b and the cooling unit for the R light source 6r are fans is described. . The cooling unit for the B light source and the cooling unit for the R light source may be an integrated cooling unit.

  Further, in each of the above-described embodiments, the drive current for the blank mode, the fan rotation speed, and the motor rotation speed are determined in advance by the system control unit 1 according to the program, but, for example, are calculated with reference to the lighting history of the R light source. Is also good. Alternatively, the light amount from the R light source may be measured, and the light amount may be calculated according to the measured light amount.

  In each of the above-described embodiments, the semiconductor laser that emits B light and the semiconductor laser that emits R light are used. However, a semiconductor laser that emits G light may be combined.

  Further, in each of the embodiments described above, the case where the phosphor 16 rotates is described, but the phosphor does not necessarily need to rotate. The phosphor may be of a transmission type instead of a reflection type as in each embodiment.

  Further, in each of the above-described embodiments, the case where a digitally driven reflective liquid crystal display element is used as the light modulation unit has been described. However, an analogly driven reflective liquid crystal display element or a transmission type liquid crystal display element may be used. Alternatively, a digital micromirror device may be used.

Further, in each of the above-described embodiments, the example in which the mode of projecting a visible image, the mode of not projecting a visible image, the mode of projecting a black image, and the mode of projecting an IR image are maintained over a plurality of frames has been described. However, it is not limited to this. For example, a mode for projecting a visible image and a mode for not projecting a visible image may be switched for each frame in order to improve the visibility of a moving image. Further, the mode of projecting a visible image and the mode of projecting a black image may be switched for each frame, or the mode of projecting a visible image and the mode of projecting an IR image may be switched for each frame.
(Other Examples)
The present invention supplies a program for realizing one or more functions of the above-described embodiments to a system or an apparatus via a network or a storage medium, and one or more processors in a computer of the system or the apparatus read and execute the program. This processing can be realized. Further, it can also be realized by a circuit (for example, an ASIC) that realizes one or more functions.

  Each of the embodiments described above is only a typical example, and various modifications and changes can be made to each embodiment when the present invention is implemented.

DESCRIPTION OF SYMBOLS 1 System control part 2 Mode switching part 3 Drive current calculation part 5ba, 5bb Blue (B) light source 5rc, 5rd Red (R) light source 5i IR light source

Claims (12)

An image projection device that projects an image based on an input image signal,
A first light source that emits first light used for projecting a visible image;
Light source control means for controlling a drive current supplied to the first light source;
Switching means for switching the image projection device between a first state of projecting a visible image based on the image signal and a second state of not projecting a visible image based on the image signal,
The image projection apparatus according to claim 2, wherein the light source control unit supplies a drive current lower than the first state and not zero to the first light source in the second state. The first light is light having a different wavelength from the first light, and has a second light source that emits second light used for projecting the visible image,
2. The image projection apparatus according to claim 1, wherein the light source control unit stops supplying a drive current to the second light source in the second state. Light modulating means for modulating third light generated using the first and second lights;
Modulation control means for controlling the driving of the light modulation means,
The modulation control unit drives the light modulation unit based on the image signal in the first state, and does not guide the third light to a projection surface in the second state, or The image projection apparatus according to claim 1, wherein the image projection apparatus is driven such that the light is guided by being dimmed from the state of 1. Light modulating means for modulating third light generated using the first and second lights;
A shutter that opens and closes an optical path toward the light modulation unit or an optical path from the light modulation unit toward the projection surface;
Shutter control means for controlling the driving of the shutter,
The shutter control means drives the shutter to open the optical path in the first state, and drives the shutter to block the optical path in the second state. The image projection device according to claim 1. Cooling means for cooling the first light source;
Cooling control means for controlling the cooling means,
5. The image projection apparatus according to claim 1, wherein the cooling control unit weakens the cooling of the first light source in the second state more than in the first state. 6. . A wavelength conversion element that converts the wavelength of the second light;
A motor for rotating the wavelength conversion element,
Motor control means for controlling the rotation of the motor,
5. The motor control device according to claim 2, wherein the motor control unit sets a rotation speed of the motor in the second state to be lower than a rotation speed in the first state. 6. Image projection device.   When the light source control unit switches from the second state to the first state, the first light source control unit performs the first light source control before the rotation speed of the motor increases to the rotation speed in the first state. The image projection apparatus according to claim 1, wherein supply of the drive current in the first state to the light source is started.   The image projection device according to any one of claims 1 to 7, wherein the first light is red light.   9. The light source according to claim 1, further comprising a third light source that emits fourth light used for projecting an IR image, the light having a different wavelength from the first or second light. An image projection device according to claim 1.   The second state includes a state in which the image signal is not input to the image projection apparatus, a state in which there is a user instruction not to perform image projection based on the image signal, and a state in which an IR image signal is input to the image projection apparatus. The image projection device according to claim 1, wherein the image projection device is in at least one of a state in which the image is projected. A control method of an image projection device that projects an image based on an input image signal,
Controlling a drive current supplied to a first light source that emits a first light used for projecting a visible image;
Switching the image projection device between a first state of projecting a visible image based on the image signal and a second state of not projecting a visible image based on the image signal,
In the second state, a drive current lower than the first state and not zero is supplied to the first light source.   A computer program for causing a computer of an image projection device to execute a process according to the control method according to claim 11.