JP2020034628A - Light source device and image projection device - Google Patents

Abstract

To minimize optical damages to light sources.SOLUTION: A light source device is provided, comprising light sources 4rc, 4rd, cooling means 6r for cooling the light sources, control means 1, 7, 33 for controlling the cooling means, and acquisition means 32 configured to acquire information having correlation to emission intensity of the light sources. The control means uses the information to control the cooling means such that emission intensity of the light sources does not exceed a maximum emission intensity that does not cause optical damage to the light sources.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light source device suitable for 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.

JP 2016-224304 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.

  The present invention provides a light source device and a projector capable of suppressing the occurrence of COD in a light source such as a red LD.

  A light source device according to one aspect of the present invention includes a light source, a cooling unit that cools the light source, a control unit that controls the cooling unit, and an acquisition unit that acquires information correlated with the light emission amount of the light source. The control means controls the cooling means using the information so that the light emission amount of the light source does not exceed an upper limit light emission amount at which the light source does not cause optical damage.

An image projection device using the light source device also constitutes one aspect of the present invention.
Further, a control method according to another aspect of the present invention is applied to a light source device having a light source and a cooling unit that cools the light source. The control method includes: obtaining information correlated with the light emission amount of the light source; and using the information, the cooling unit so that the light emission amount of the light source does not exceed an upper limit light emission amount that does not cause optical damage to the light source. Controlling).

  Note that a computer program that causes a computer of the light source device to execute a process according to the above control method also constitutes another aspect of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of COD in a light source can be suppressed.

FIG. 1 is a diagram illustrating a configuration of a projector that is Embodiment 1 of the present invention. FIG. 4 is a diagram illustrating a relationship between a drive current of an R light source and a measured temperature value in the first embodiment. 5 is a flowchart illustrating a cooling control process performed by the projector according to the first embodiment. FIG. 2 is a diagram illustrating a configuration of a projector that is Embodiment 2 of the present invention. FIG. 10 is a diagram illustrating a relationship between a drive current of an R light source and a measured light amount in the second embodiment. 9 is a flowchart illustrating cooling control processing performed by the projector according to the second embodiment. FIG. 9 is a diagram illustrating a configuration of a projector that is Embodiment 3 of the present invention. FIG. 14 is a diagram illustrating a relationship between a drive current of an R light source and a measured wavelength value in the third embodiment. 9 is a flowchart illustrating a cooling control process performed by the projector according to the third embodiment.

  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 drive current calculation unit, and 3 is a light source drive unit. 4ba and 4bb are B light sources, and 4rc and 4rd are R light sources. 5b is a heat sink for the B light source, 5r is a heat sink for the R light source, 6b is a cooling unit for the B light source, 6r is a cooling unit for the R light source, and 7 is a cooling control unit.

  8ba and 8bb are B collimating lenses, and 8rc and 8rd are R collimating lenses. Reference numeral 9 denotes a first lens, 10 denotes a second lens, 12 denotes a light reflecting member, 13 denotes a glass plate, and 14 denotes a third lens. Reference numeral 15 denotes a phosphor, 16 denotes a phosphor support member, 17 denotes a motor, and 18 denotes a motor control unit. 20a is a first fly-eye lens, 20b is a second fly-eye lens, 21 is a polarization conversion element, and 22 is a fourth lens.

  23 is a dichroic mirror, 24 is a wavelength-selective phase plate, 25RB is a RB polarizing beam splitter, 25G is a G polarizing beam splitter, 26R is a λ / 4 plate for R, 26G is a λ / 4 plate for G, and 26B is B Λ / 4 plate. 27R is a light modulation unit for R, 27G is a light modulation unit for G, and 27B is a light modulation unit for B. 29 is a color combining prism, and 31 is a projection lens. Reference numeral 32 denotes a temperature measurement unit, and 33 denotes a drive condition calculation unit.

  The drive current calculation unit 2 calculates drive currents of the B light sources 4ba and 4bb and the R light sources 4rc and 4rd according to an instruction from the system control unit 1. The light source drive unit 3 supplies each drive current calculated by the drive current calculation unit 2 to each light source to drive it.

  The B light sources 4ba and 4bb are configured using the same semiconductor laser diodes that emit B light (blue light). The peak wavelength of the B light sources 4ba, 4bb is, for example, 455 nm. The R light sources 4rc and 4rd are configured using the same semiconductor laser diodes that emit R light (red light). The peak wavelength of the R light sources 4rc and 4rd is, for example, 635 nm. The B light sources 4ba, 4bb are attached to a B light source heat sink 5b. The R light sources 4rc and 4rd are attached to the R light source heat sink 5r. 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 5b for the B light source and the heat sink 5r 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) 6b and a cooling unit for an R light source (cooling means: , R light source cooling fan) 6r.

  The cooling air from each of the cooling fan 6b for the B light source 6b and the cooling fan 6r for the R light source cools the heat sink 5b for the B light source and the heat sink 5r for the R light source. The rotation speeds (fan rotation speeds) of the cooling fan 6b for the B light source and the cooling fan 6r for the R light source are controlled by the cooling control unit 7 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. In FIG. 1, the directions of the arrows protruding from the cooling fan 6b for the B light source and the cooling fan 6r for the R light source indicate the direction of the cooling air.

  The B light source heat sink 5b and the R light source heat sink 5r average the heat generated by the B light sources 4ba and 4bb and the heat generated by the R light sources 4rc and 4rd, respectively. By cooling the B light source heat sink 5b and the R light source heat sink 5r with the B light source cooling fan 6b and the R light source cooling fan 6r, respectively, the B light sources 4ba and 4bb and the R light sources 4rc and 4rd can be simultaneously cooled. .

  The B lights emitted from the B light sources 4ba, 4bb enter the B collimating lenses 8ba, 8bb, respectively. The R lights emitted from the R light sources 4rc and 4rd enter the R collimating lenses 8rc and 8rd, 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 9 and the second lens 10 and is emitted as excitation light 11. The first lens 9 and the second lens 10 have a role of adjusting the light beam diameter of the light emitted from each collimating lens.

  The excitation light 11 is reflected by the light reflecting member 12 provided on the surface of the glass plate 13 and irradiates the phosphor 15 via the third lens 14. The light reflecting member 12 is provided only on a portion of the surface of the glass plate 13 where the excitation light 11 is irradiated. The third lens 14 collects the excitation light 11 to form a light irradiation area of a predetermined size on the phosphor 15.

  The material of the phosphor 15 is, for example, YAG: Ce. The phosphor 15 is provided in a circumferential direction around the rotation axis of the motor 17 and is supported by the phosphor support member 16. The material of the phosphor support member 16 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 17 rotates the phosphor 15 and the phosphor support member 16 in order to efficiently radiate heat from the phosphor 15. The rotation speed of the motor 17 is controlled by the motor control unit 18 in accordance with an instruction from the system control unit 1.

  The phosphor 15 converts the wavelength of a part of the B light in the excitation light 11 to generate yellow fluorescent light. The fluorescent light, the B excitation light (non-converted light) that has not been wavelength-converted by the phosphor 15 and the R light are combined to generate illumination light 19 as white (W) light.

  The illumination light 19 enters the third lens 14 and is converted into substantially parallel light. The illumination light 19 transmitted through the third lens 14 is further transmitted through a portion of the glass plate 13 other than the light reflecting member 12, and transmitted through the first fly-eye lens 20a and the second fly-eye lens 20b. Is split into a plurality of light beams and enters the polarization conversion element 21. The polarization conversion element 21 converts the illumination light 19, which is non-polarized 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 19 from the phosphor 15 is unpolarized light. Therefore, in order to efficiently perform polarization separation by a polarization beam splitter described later, the polarization conversion element 21 is provided to convert the light into linearly polarized light (S-polarized light having a polarization direction perpendicular to the plane of FIG. 1).

  The plurality of light beams as the illumination light 19 emitted from the polarization conversion element 21 are condensed by the fourth lens 22 and are superimposed on the three light modulation units 27R, 27G, and 27B. Thereby, each light modulator is uniformly illuminated.

  The illumination light 19 transmitted through the fourth lens 22 is guided to the dichroic mirror 23. The dichroic mirror 23 reflects the RB light 19RB of the illumination light 19 and transmits the G light 19G. The S-polarized G light 19G transmitted through the dichroic mirror 23 is incident on the G polarization beam splitter 25G, is reflected on the polarization splitting surface, and reaches the G light modulation unit 27G. Here, the G light modulation section 27G is a digitally driven reflective liquid crystal display element, and forms an original image for modulating the G light 19G. The system control unit 1 drives the G light modulation unit 27G to form an original image in response to an externally input video signal. At this time, the system control unit 1 drives each pixel of the G light modulation unit 27G ON / OFF during each frame period, and controls the duty of the ON / OFF drive to control the G light modulation unit 27G. Is expressed. The same applies to the R light modulator 27R and the B light modulator 27B.

  The G light modulator 27G modulates and reflects the G light 19G according to the original image. Thus, the modulated light 28G is emitted from the G light modulator 27G. The S-polarized light component of the modulated light 28G is reflected by the polarization splitting surface of the G polarization beam splitter 25G, 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 28G passes through the polarization splitting surface of the G polarization beam splitter 25G. At this time, in a state where all the polarized light 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 26G is changed to the optical axis incident on the G polarizing beam splitter 25G. And the direction perpendicular to the plane containing the reflected optical axis. Thereby, the influence of the disorder of the polarization state generated by the G polarization beam splitter 25G and the G light modulation unit 27G can be reduced. The modulated light 28G emitted from the G polarization beam splitter 25G enters the color combining prism 29.

  The RB light 19 RB reflected by the dichroic mirror 23 enters the wavelength-selective phase plate 24. The wavelength-selective phase plate 24 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 19RB transmitted through the wavelength-selective phase plate 24 enters the RB polarization beam splitter 25RB.

  The RB polarization beam splitter 25RB transmits the R light 19R that is P-polarized light and reflects the B light 19B that is S-polarized light. The R light 19R transmitted through the polarization splitting surface of the RB polarization beam splitter 25RB is modulated and reflected by the R light modulation unit 27R, and emitted as modulated light 28R. The P-polarized light component of the modulated light 28R passes through the polarization splitting surface of the RB polarization beam splitter 25RB, 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 28R is reflected by the polarization splitting surface of the RB polarization beam splitter 25RB and enters the color combining prism 29.

  The B light 19B reflected by the polarization splitting surface of the RB polarization beam splitter 25RB is modulated and reflected by the B light modulator 27B to become a modulated light 28B. The S-polarized light component of the modulated light 28B is reflected by the polarization splitting surface of the RB polarization beam splitter 25RB, 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 28B passes through the polarization splitting surface of the RB polarization beam splitter 25RB and enters the color combining prism 29. At this time, by adjusting the slow axes of the λ / 4 plates 26R and 26B in the same manner as the G λ / 4 plate 26G, it is possible to adjust the R and B full black display states. The RB light 28RB thus combined into one light flux and emitted from the RB polarizing beam splitter 25RB enters the color combining prism 29.

  The color combining prism 29 combines the RB light 28RB and the G light 19G by transmitting the RB light 28RB to generate the projection light 30. The projection light 30 is enlarged and projected through a projection lens 31 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 temperature measurement unit (acquisition unit) 32 measures the temperatures of the B light sources 4ba and 4bb and the R light sources 4rc and 4rd, respectively. The position at which the temperature measurement unit 32 measures the temperature of each light source may be any position at which a temperature correlated with the junction temperature of each light source can be measured, and may be a position close to or distant from each light source. Further, the temperature measuring section 32 may measure the environmental temperature in order to subtract a change in the environmental temperature of the projector when the temperature of each light source changes.

  The drive condition calculation unit 33 acquires the value of the drive current of each light source from the drive current calculation unit 2, and further acquires the temperature of each light source from the temperature measurement unit 32. The driving condition calculation unit 33 calculates the driving conditions of the cooling fan 6b for the B light source and the cooling fan 6r for the R light source based on the obtained driving current value and temperature of each light source, and calculates the calculated driving conditions to the system control unit 1. Is fed back to the cooling control unit 7 via the. The cooling control unit 7 controls the drive voltage of the cooling fan 6b for the B light source and the cooling fan 6r for the R light source, in other words, the number of rotations of the fan, in accordance with the fed-back driving condition. The system control unit 1, the driving condition calculation unit 33, and the cooling control unit 7 constitute a control unit.

  The graph of FIG. 2 shows the upper limit and the lower limit of the temperature with respect to the drive current of each R light source in the present embodiment. The horizontal axis in FIG. 2 indicates the driving current supplied to the R light source by the light source driving unit 3, and the vertical axis indicates the temperature of the R light source measured by the temperature measuring unit 32.

  The solid line in the graph indicates the upper limit temperature of the R light source for each drive current. This upper limit temperature is set to reduce the risk that the life of the R light source is shortened by a high temperature. Since the R light source in this embodiment is a semiconductor laser, a high junction temperature shortens the life. Since the junction temperature increases as the drive current increases when the temperature of the light source is the same, the upper limit temperature of the light source is set lower as the drive current increases.

  On the other hand, the broken line in the graph indicates the lower limit temperature of the R light source for each drive current. The temperature of the R light source is an evaluation value as information correlated with the light emission amount of the R light source. Specifically, when the driving current of the R light source is constant, the light emission amount (light output) of the R light source increases as the temperature of the R light source decreases. As a result, the lower the temperature of the R light source, the higher the risk of COD (optical damage) occurring in the R light source. Also, the risk of COD occurring in the R light source increases as the driving current of the R light source increases. For this reason, the lower limit temperature of the R light source is set higher as the drive current increases. The lower limit temperature is set as a predetermined value corresponding to the maximum value as a temperature at which the light emission amount of the R light source does not exceed a maximum value (upper limit light emission amount) at which COD does not occur in the R light source. It is desirable that the difference between the upper limit temperature and the lower limit temperature of the R light source be smaller as the drive current is larger.

  When the temperature of the R light source measured by the temperature measuring unit 32 is out of the allowable range from the upper limit temperature to the lower limit temperature shown in FIG. 2, the driving condition calculation unit 33 sets the R light source so that the temperature of the R light source falls within the allowable range. The driving condition of the light source cooling fan 6r is calculated. Then, the cooling control unit 7 obtains the driving conditions calculated via the system control unit 1, and controls the R light source cooling fan 6r based on the driving conditions.

  The flowchart of FIG. 3 illustrates a cooling control process (control method) performed by the system control unit 1, the driving condition calculation unit 33, and the cooling control unit 7 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.

  The system control unit 1 starts this processing at S1 at an arbitrary timing or at a predetermined timing determined by the user. In S2, the system control unit 1 causes the temperature measurement unit 32 to measure the temperatures of the R light sources 4rc and 4rd.

  Next, in S3, the system control unit 1 causes the drive condition calculation unit 33 to acquire the drive current values of the R light sources 4rc and 4rd from the drive current calculation unit 2.

  Next, in S4, the drive condition calculation unit 33 determines whether or not the temperature (measured temperature) measured in S2 is within the allowable range shown in FIG. 2 in the value of the drive current acquired in S3. If the measured temperature is within the allowable range, the driving condition calculating unit 33 proceeds to S8 to end the present process, and if not, proceeds to S5.

  In S5, the driving condition calculation unit 33 determines whether the measured temperature is higher than an allowable range. If the measured temperature is higher than the allowable range, that is, if the measured temperature is higher than the upper limit temperature shown in FIG. 2, the driving condition calculation unit 33 proceeds to S6. On the other hand, when the measured temperature is lower than the allowable range, that is, when the measured temperature is lower than the lower limit temperature shown in FIG. 2, the process proceeds to S7.

  In S6, the drive condition calculation unit 33 increases the drive voltage of the R light source cooling fan 6r via the cooling control unit 7 to increase the fan rotation speed. That is, the cooling for the R light sources 4rc and 4rd is enhanced. Then, the process returns to S2.

  On the other hand, in S7, the drive condition calculation unit 33 lowers the drive voltage of the R light source cooling fan 6r via the cooling control unit 7 to decrease the fan rotation speed. That is, the cooling for the R light sources 4rc and 4rd is weakened. Then, the process returns to S2.

  As described above, in the present embodiment, cooling is performed so that the measured temperature of the R light source does not fall below the lower limit temperature, that is, the light emission amount for each drive current of the R light source does not exceed the upper limit light emission amount that does not generate COD. Thereby, the risk of COD occurring in the R light source can be reduced, and the life of the R light source can be extended.

  Next, a second embodiment of the present invention will be described. FIG. 4 illustrates a configuration of the projector according to the second embodiment. In this embodiment, the same components as those of the first embodiment are denoted by the same reference numerals.

  The projector according to the present embodiment does not include the temperature measurement unit 32 described in the first embodiment (FIG. 1), but includes a light branching unit 34 and a light amount measurement unit (acquisition unit) 35. The light branching portion 34 is formed of glass, reflects a part of the R light emitted from the R light sources 4rc and 4rd, and guides the R light to the light amount measuring portion 35. The light amount measuring unit 35 is configured by a photodiode, and measures the light amount of the R light reflected by the light branching unit 34. The light amount measured by the light amount measurement unit 35 is sent to the drive condition calculation unit 33.

  The graph of FIG. 5 shows the upper limit and the lower limit of the measurement value of the light amount measurement unit 35 with respect to the drive current of each R light source in the present embodiment. The horizontal axis in FIG. 5 indicates the drive current supplied to the R light source by the light source driving unit 3, and the vertical axis indicates the light amount from the R light source measured by the light amount measurement unit 35.

  The solid line in the graph indicates the upper limit light amount for each drive current. The light amount (measured light amount) of the R light source measured by the light amount measuring unit 35 is an evaluation value as information having a correlation with the light emission amount of the R light source. Specifically, it indicates that the larger the measured light amount, the larger the light emission amount of the R light source. The upper limit light amount is set as a predetermined value corresponding to the maximum value, as a light amount at which the light emission amount of the R light source does not exceed a maximum value (upper limit light emission amount) at which COD does not occur in the R light source.

  On the other hand, the broken line in the graph indicates the lower limit light amount for each drive current. The lower limit light amount is set in order to reduce the risk that the life of the R light source is shortened by high temperature. It is desirable that the ratio between the upper limit light amount and the lower limit light amount of the R light source be smaller as the drive current is larger. When the light amount measured by the light amount measuring unit 35 is out of the allowable range from the upper limit light amount to the lower limit light amount shown in FIG. 5, the driving condition calculating unit 33 controls the cooling of the R light source so that the light amount of the R light source falls within the allowable range. The driving condition of the fan 6r is calculated. Then, the cooling control unit 7 obtains the driving conditions calculated via the system control unit 1, and controls the R light source cooling fan 6r based on the driving conditions.

  FIG. 6 is a flowchart illustrating a cooling control process performed by the system control unit 1, the driving condition calculation unit 33, and the cooling control unit 7 in the present embodiment.

  The system control unit 1 starts the present process in S11 at an arbitrary or predetermined timing determined by the user. In S12, the system control unit 1 causes the light amount measurement unit 35 to measure the light amounts from the R light sources 4rc and 4rd.

  Next, in S13, the system control unit 1 causes the drive condition calculation unit 33 to acquire the drive current values of the R light sources 4rc and 4rd from the drive current calculation unit 2.

  Next, in S14, the drive condition calculation unit 33 determines whether or not the light amount (measured light amount) measured in S12 is within the allowable range shown in FIG. 5 in the value of the drive current acquired in S13. If the measured light amount is within the allowable range, the driving condition calculating unit 33 proceeds to S18 to end this processing, and if not, proceeds to S15.

  In S15, the drive condition calculation unit 33 determines whether the measured light amount is smaller than the allowable range. When the measured light amount is smaller than the allowable range, that is, when the measured light amount is lower than the lower limit light amount shown in FIG. 5, the driving condition calculation unit 33 proceeds to S16. On the other hand, when the measured light amount is larger than the allowable range, that is, when the measured light amount exceeds the upper limit light amount shown in FIG. 5, the process proceeds to S17.

  In S16, the drive condition calculation unit 33 increases the drive voltage of the R light source cooling fan 6r via the cooling control unit 7 to increase the fan rotation speed. That is, the cooling for the R light sources 4rc and 4rd is enhanced. Then, the process returns to S12.

  On the other hand, in S17, the drive condition calculation unit 33 reduces the drive voltage of the R light source cooling fan 6r via the cooling control unit 7 to reduce the fan rotation speed. That is, the cooling for the R light sources 4rc and 4rd is weakened. Then, the process returns to S12.

  As described above, in this embodiment, cooling is performed so that the measured light amount of the R light does not exceed the upper limit light amount, that is, the light emission amount for each drive current of the R light source does not exceed the upper limit light emission amount that does not generate COD. Thereby, the risk of COD occurring in the R light source can be reduced, and the life of the R light source can be extended.

  Next, a third embodiment of the present invention will be described. FIG. 7 illustrates a configuration of a projector according to the third embodiment. In this embodiment, the same components as those of the first embodiment are denoted by the same reference numerals.

  The projector according to the present embodiment does not include the temperature measurement unit 32 described in the first embodiment (FIG. 1), but includes a light branching unit 34, a diffractive optical element 36, and a wavelength measurement unit (acquisition unit) 37. The light branching portion 34 is made of glass, and reflects a part of the R light emitted from the R light sources 4rc and 4rd to guide the R light to the diffractive optical element 36. The diffractive optical element 36 is formed of glass and has a characteristic of changing the angle at which diffracted light travels according to the wavelength of incident light. The wavelength measuring unit 37 is a line sensor in which a plurality of photodiodes are arranged in a line. The wavelength (peak wavelength) of the R light can be determined based on which photodiode on the line sensor detects the R light diffracted by the diffractive optical element 36 among the R lights from the R light sources 4rc and 4rd. The wavelength measured by the wavelength measurement unit 37 is sent to the drive condition calculation unit 33.

  The graph of FIG. 8 shows the upper limit and the lower limit of the measured value of the wavelength measuring unit 37 with respect to the drive current of each R light source in the present embodiment. The horizontal axis in FIG. 8 indicates the driving current supplied to the R light source by the light source driving unit 3, and the vertical axis indicates the wavelength from the R light source measured by the wavelength measuring unit 37.

  The solid line in the graph indicates the upper limit wavelength for each drive current. When the driving current of the R light source is constant, the wavelength of the R light emitted from the R light source increases as the temperature of the R light source increases. The upper limit wavelength is set in order to reduce the risk that the life of the R light source is shortened by a high temperature.

  On the other hand, the broken line in the graph indicates the lower limit wavelength for each drive current. The wavelength of the R light emitted from the R light source is an evaluation value having a correlation with the light emission amount of the R light source. Specifically, when the driving current of the R light source is constant, as described above, the lower the temperature of the R light source, the larger the light emission amount of the R light source, but the shorter the wavelength of the R light emitted from the R light source at the same time. Become. The lower limit wavelength is set as a predetermined value corresponding to the maximum value as a wavelength at which the light emission amount of the R light source does not exceed a maximum value (upper limit light emission amount) at which COD does not occur in the R light source.

  It is desirable that the difference between the upper limit wavelength and the lower limit wavelength of the R light source be smaller as the drive current is larger. When the wavelength measured by the wavelength measuring unit 37 is out of the allowable range from the upper limit wavelength to the lower limit wavelength shown in FIG. 8, the driving condition of the R light source cooling fan 6r is adjusted so that the wavelength falls within the allowable range. The calculation unit 33 performs calculation. The drive condition calculation unit 33 calculates the drive condition of the R light source cooling fan 6r such that the light amount of the R light source falls within the allowable range. Then, the cooling control unit 7 obtains the driving conditions calculated via the system control unit 1, and controls the R light source cooling fan 6r based on the driving conditions.

  The flowchart in FIG. 9 illustrates the cooling control process performed by the system control unit 1, the driving condition calculation unit 33, and the cooling control unit 7 in the present embodiment.

  The system control unit 1 starts the present process in S21 at a user-arbitrarily determined or predetermined timing. In S22, the system control unit 1 causes the wavelength measurement unit 37 to measure the wavelength of the R light from the R light sources 4rc and 4rd.

  Next, in S23, the system control unit 1 causes the drive condition calculation unit 33 to acquire the drive current values of the R light sources 4rc and 4rd from the drive current calculation unit 2.

  Next, in S24, the drive condition calculation unit 33 determines whether or not the wavelength (measured wavelength) measured in S22 is within the allowable range shown in FIG. 8 for the value of the drive current acquired in S23. If the measured wavelength is within the allowable range, the driving condition calculation unit 33 proceeds to S28 to end the present process, and if not, proceeds to S25.

  In S25, the drive condition calculation unit 33 determines whether the measured wavelength is longer than the allowable range. When the measured wavelength is longer than the allowable range, that is, when the measured wavelength is longer than the upper limit wavelength shown in FIG. 8, the driving condition calculation unit 33 proceeds to S26. On the other hand, when the measured wavelength is shorter than the allowable range, that is, when the measured wavelength is shorter than the lower limit wavelength shown in FIG. 8, the process proceeds to S27.

  In S26, the drive condition calculation unit 33 increases the drive voltage of the R light source cooling fan 6r via the cooling control unit 7 to increase the fan rotation speed. That is, the cooling for the R light sources 4rc and 4rd is enhanced. Then, the process returns to S22.

  On the other hand, in S27, the drive condition calculation unit 33 lowers the drive voltage of the cooling fan 6r for R light source via the cooling control unit 7 to decrease the fan rotation speed. That is, the cooling for the R light sources 4rc and 4rd is weakened. Then, the process returns to S22.

As described above, in the present embodiment, cooling is performed so that the wavelength of the R light does not fall below the lower limit wavelength, that is, the light emission amount for each drive current of the R light source does not exceed the upper limit light emission amount that does not generate COD. Thereby, the risk of COD occurring in the R light source can be reduced, and the life of the R light source can be extended.
(Other Examples)
Even when COD does not occur, the R light source has a reduced light emission amount due to a change over time and an increased heat generation amount. For this reason, the driving condition calculation unit 33 may acquire the degree of deterioration of the R light source due to aging, and change the driving condition of the R light source cooling fan 6r according to the degree of deterioration. Specifically, when the degree of deterioration exceeds a predetermined value, the fan rotation speed of the cooling fan 6r for R light source is increased, and when the degree of deterioration is lower than the predetermined value, the fan rotation speed is decreased. The degree of deterioration is expressed, for example, as a ratio between the amount of light emitted when the R light source is initially driven with a predetermined drive current at a certain temperature and the amount of light emitted when the R light source is driven with the same drive current in a state deteriorated with time. be able to. This degree of deterioration can be calculated by storing the initial light emission amount and calculating the ratio with the light emission amount in a state deteriorated due to aging.

  Alternatively, the degree of deterioration may be estimated based on the correspondence between the lighting history of the R light source and the light emission amount of the R light source assumed in advance. Further, the degree of deterioration may be obtained from the power supplied to the R light source and the temperature of the R light source without measuring the light emission amount, or may be obtained from the power supplied to the R light source and the wavelength of light emitted from the R light source. You may.

  In each of the above-described embodiments, the case where only the control of the cooling unit for the R light source is performed based on the driving condition calculated by the driving condition calculation unit 33 has been described. You may.

  Further, in each of the above-described embodiments, the case has been described where both the cooling unit 6b for the B light source and the cooling unit 6r for the R light source are fans, but using a cooling unit other than the fan, such as a liquid cooling system or a Peltier element. Is also good. 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 the projector of each embodiment described above, the lighting timing of the R light source and the driving timing of the cooling unit for the R light source may be controlled. Specifically, the cooling unit for the R light source may be controlled such that the cooling of the R light source by the cooling unit for the R light source is in a steady state after the R light source is turned on. In other words, the R light source may be turned on before the cooling of the R light source by the R light source cooling unit reaches a steady state. This is because the risk of CОD can be reduced by promoting the temperature rise of the R light source in the initial lighting period of the R light source whose temperature is still low.

  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 15 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.

  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.

Reference Signs List 1 system control unit 3 drive condition calculation unit 4ba, 4bb blue (B) light source 4rc, 4rd red (R) light source 6r R light source cooling unit (fan)

Claims (13)

Light source,
Cooling means for cooling the light source,
Control means for controlling the cooling means,
Acquiring means for acquiring information having a correlation with the light emission amount of the light source,
The light source device according to claim 1, wherein the control unit controls the cooling unit using the information so that a light emission amount of the light source does not exceed an upper limit light emission amount that does not cause optical damage to the light source.   The light source device according to claim 1, wherein the information is a temperature of the light source.   The light source device according to claim 2, wherein the control unit weakens the cooling of the light source by the cooling unit when the temperature falls below a predetermined value set according to the upper limit light emission amount.   The light source device according to claim 1, wherein the information is a light amount of at least a part of light emitted from the light source.   The light source device according to claim 4, wherein the control unit weakens the cooling of the light source by the cooling unit when the light amount exceeds a predetermined value set according to the upper limit light emission amount.   The light source device according to claim 1, wherein the information is a wavelength of light emitted from the light source.   The light source device according to claim 6, wherein the control unit weakens the cooling of the light source by the cooling unit when the wavelength falls below a predetermined value set according to the upper limit light emission amount.   The light source device according to claim 1, wherein the information is a degree of deterioration of the light source.   The light source according to claim 8, wherein the control unit weakens the cooling of the light source by the cooling unit when the degree of deterioration is lower than a predetermined value set according to the upper limit light emission amount. apparatus.   10. The cooling unit according to claim 1, wherein the control unit controls the cooling unit so that cooling of the light source by the cooling unit is in a steady state after the light source is turned on. Light source device. A light source device according to any one of claims 1 to 10,
A light modulation unit that modulates light from the light source device,
An image projection apparatus, wherein an image is displayed by projecting light from the light modulation unit onto a projection surface. A method for controlling a light source device having a light source and a cooling unit for cooling the light source,
Obtaining information having a correlation with the light emission amount of the light source;
Using the information to control the cooling unit so that the light emission amount of the light source does not exceed an upper limit light emission amount that does not cause optical damage to the light source.   13. A computer program for causing a computer of a light source device having a light source and a cooling unit for cooling the light source to execute a process according to the control method according to claim 12.