Light intensity measuring device, projection device, light intensity measuring method, and control program

Abstract

To provide a light quantity measurement apparatus capable of accurately measuring the quantity of light of each of lighted multiple semiconductor lasers.SOLUTION: In a light quantity measurement apparatus, a drive circuit supplies, in video projection mode, a current of a first current value to each of semiconductor lasers, and periodically executes, in light quantity measurement mode, a process of a predetermined period including first and second periods. In the process of the predetermined period, in the first period, the drive circuit sequentially selects the semiconductor lasers by group of one or more semiconductor lasers, stops supplying a current to the semiconductor lasers in the selected groups, supplies a current of the first current value to the other semiconductor lasers not selected. In the second period, the drive circuit supplies a current of a second current value, which is higher than the first current value, to each of the semiconductor lasers. An arithmetic processing circuit calculates the quantity of light of each of the groups of the semiconductor lasers on the basis of a result detected by an optical sensor in the first period of the predetermined period.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a light quantity measurement device, a projection device, a light quantity measurement method, and a control program, and relates to a light quantity measurement device, a projection device, a light quantity measurement method, and a control program suitable for accurately measuring the light quantity of each of a plurality of semiconductor lasers having different wavelengths as light sources during lighting.

Background Art

[0002] There is known a projection device that reflects and modulates light from a light source by a reflective light modulation element based on video data, and selectively reflects the modulated light by a reflective polarizing plate to project an image onto a projection medium. In such a projection device, a light sensor is arranged in the optical path of the light emitted from the light source or the like to detect the light quantity of the light source, and the light quantity of the light source can be stabilized by performing feedback control on the light source based on the detected light quantity.

[0003] Patent Document 1 discloses a detection device for detecting the light quantity of light from a light source of a projection device that irradiates light emitted from a light source onto a reflective light modulation element that modulates and reflects the irradiated light based on video data, and projects the light reflected by the light modulation element. This detection device includes a light sensor provided between the light source and the light modulation element, a ratio calculation unit that calculates, based on video data, the ratio of the return light returning from the light modulation element toward the light source to the light irradiated on the light modulation element, and a light quantity calculation unit that calculates the light quantity of the light emitted from the light source using the detection output of the light sensor and the ratio calculated by the ratio calculation unit. Thereby, this detection device detects the light quantity of the light from the light source with high accuracy.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The detection device disclosed in Patent Document 1 can measure the amount of light each of multiple semiconductor lasers with different wavelengths that are used as light sources while they are lit. For example, this can be done by sequentially selecting and illuminating each of the multiple semiconductor lasers with different wavelengths that are used as light sources. However, this detection device has a problem in that, during the period in which the amount of light of the lit semiconductor laser being measured is being measured, the temperature of the non-lit semiconductor lasers that are not being measured becomes lower than the temperature during image projection (normal operation). Therefore, it is not possible to accurately measure the amount of light each of the multiple semiconductor lasers while they are lit.

[0006] This disclosure has been made in view of the above points, and aims to provide a light intensity measuring device, projection device, light intensity measuring method, and control program suitable for accurately measuring the light intensity of multiple semiconductor lasers with different wavelengths that serve as light sources while they are lit. [Means for solving the problem]

[0007] A light intensity measuring device according to one aspect of the present disclosure includes a drive circuit that individually drives each of a plurality of semiconductor lasers included in a light source, a photosensor that detects light emitted from the light source, and a calculation processing circuit that calculates at least the light intensity of each of the plurality of semiconductor lasers based on the detection result by the photosensor, wherein the drive circuit, when the operating mode is image projection mode, supplies a current of a first current value to each of the plurality of semiconductor lasers, and when the operating mode is light intensity measuring mode, periodically performs processing for a predetermined period consisting of a first period and a second period, in which processing for the predetermined period, in the first period, sequentially selects the plurality of semiconductor lasers for each group of semiconductor lasers, stops supplying current to the semiconductor lasers of the selected group, and supplies current of the first current value to the remaining semiconductor lasers that have not been selected, and in the second period, supplies current of a second current value higher than the first current value to each of the plurality of semiconductor lasers, and the calculation processing circuit calculates the light intensity of each group of the plurality of semiconductor lasers based on the detection result by the photosensor in the first period of each predetermined period.

[0008] A method for measuring light intensity according to one aspect of the present disclosure is a method for measuring light intensity using a light intensity measuring device comprising: a drive circuit for individually driving each of a plurality of semiconductor lasers included in a light source; a photosensor for detecting light emitted from the light source; and a calculation processing circuit for calculating at least the light intensity of each of the plurality of semiconductor lasers based on the detection result by the photosensor, wherein when the operating mode is image projection mode, a current of a first current value is supplied to each of the plurality of semiconductor lasers; when the operating mode is light intensity measurement mode, processing for a predetermined period consisting of a first period and a second period is periodically executed, in the processing of the predetermined period, in the first period, the plurality of semiconductor lasers are selected sequentially for each group of semiconductor lasers, the supply of current to the semiconductor lasers of the selected group is stopped, and the current of the first current value is supplied to the remaining semiconductor lasers that have not been selected; and in the second period, a current of a second current value higher than the first current value is supplied to each of the plurality of semiconductor lasers, and the light intensity of each group of the plurality of semiconductor lasers is calculated based on the detection result by the photosensor in the first period of each predetermined period.

[0009] A control program according to one aspect of the present disclosure is a control program that causes a computer to perform light intensity measurement processing in a light intensity measuring device comprising: a drive circuit for individually driving each of a plurality of semiconductor lasers included in a light source; a photosensor for detecting light emitted from the light source; and a calculation processing circuit for calculating at least the light intensity of each of the plurality of semiconductor lasers based on the detection result by the photosensor, wherein when the operating mode is image projection mode, the program performs processing for supplying a current of a first current value to each of the plurality of semiconductor lasers; and when the operating mode is light intensity measurement mode, the program performs processing for a predetermined period composed of a first period and a second period. In the periodically executed process and the predetermined period process, the computer is instructed to perform the following in the first period: sequentially select the plurality of semiconductor lasers for each group of one or more semiconductor lasers, stop supplying current to the selected group of semiconductor lasers, and supply a current of the first current value to the remaining unselected semiconductor lasers; and in the second period, supply a current of a second current value higher than the first current value to each of the plurality of semiconductor lasers; and calculate the amount of light for each group of the plurality of semiconductor lasers based on the detection results by the optical sensor in the first period of each predetermined period. [Effects of the Invention]

[0010] According to this disclosure, it is possible to provide a light intensity measuring device, a projection device, a light intensity measuring method, and a control program suitable for accurately measuring the light intensity of multiple semiconductor lasers with different wavelengths that are light sources while they are lit. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows an example of the optical system configuration in the projection device according to Embodiment 1. [Figure 2] This diagram shows an example of the configuration of the projection device according to Embodiment 1, focusing on the signal processing system. [Figure 3] This is a timing chart showing the method for measuring the light intensity of each laser diode LD1 to LD3 using the projection device according to Embodiment 1. [Figure 4] This is a flowchart showing the method for measuring the light intensity of each laser diode LD1 to LD3 using the projection device according to Embodiment 1. [Figure 5] This is a timing chart showing the method for measuring the light intensity of each laser diode LD1 to LD3 using the projection device according to Embodiment 2. [Figure 6] This is a flowchart showing the method for measuring the light intensity of each laser diode LD1 to LD3 using the projection device according to Embodiment 2. [Figure 7] This is a timing chart showing a chromaticity measurement method using a projection device according to Embodiment 3. [Figure 8] This is a conceptual diagram illustrating the chromaticity adjustment method using a projection device according to Embodiment 3. [Figure 9] This flowchart shows a method for measuring the chromaticity of light before deterioration over time using a projection device according to Embodiment 3. [Figure 10] This flowchart shows a method for measuring the chromaticity of light before deterioration over time using a projection device according to Embodiment 3. [Figure 11] This flowchart shows a method for measuring the brightness of light before deterioration over time using a projection device according to Embodiment 3. [Figure 12] This flowchart shows a method for measuring and adjusting the chromaticity of light after aging using a projection device according to Embodiment 3. [Modes for carrying out the invention]

[0012] <Embodiment 1> Figure 1 shows an example of the optical system configuration in the projection device 1 according to Embodiment 1. In the following, blue light will be referred to as B light, green light as G light, red light as R light, yellow light as Y light, and white light as W light, as appropriate.

[0013] As shown in FIG. 1, the projection device 1 is, for example, a projector, and as a configuration of the optical system, it includes a light source unit 2 and an illumination optical unit 3. The light source unit 2 includes a light source 500 that includes a plurality of laser diodes (semiconductor lasers) and emits light (B light) in a predetermined wavelength band that is visually recognized as blue, and a phosphor wheel 600 coated with a phosphor that emits yellow light (Y light) when excited by the B light emitted from the light source 500, and emits B light and Y light. Note that the light emitted from the light source unit 2 is actually white light (W light) in which B light and Y light are combined. The configuration of the light source unit 2 will be described later.

[0014] The B light and Y light emitted from the light source unit 2 are incident on the illumination optical unit 3 and are reflected by the mirror 110 to change their directions. Depending on the layout of the light source unit 2 and the illumination optical unit 3, this mirror 110 can be omitted.

[0015] The Y light and B light emitted from the mirror 110 are incident on the lens 114 via the fly-eye lenses 111, 112 and the polarization conversion element 113. The fly-eye lenses 111, 112 constitute a uniform illumination optical system that disperses each light based on the Y light and B light so that each light is uniformly irradiated onto each of the light modulation elements 119, 125, 128 described later when irradiating each light modulation element 119, 125, 128.

[0016] The polarization conversion element 113 is configured by combining a polarization beam splitter and a λ / 2 plate, and is for converting ordinary light into polarized light or aligning the polarization of polarized light. In this example, the polarization conversion element 113 is assumed to convert the incident light into polarized light of S polarization. Also, in the example of FIG. 1, an optical sensor 10 for detecting light is provided in proximity to the side surface of the polarization conversion element 113. The optical sensor 10 is a white light receiving sensor having sensitivity over the entire wavelength region of visible light. The optical sensor 10 in FIG. 1 detects the light of the B light and Y light incident on the polarization conversion element 113 that has leaked from the polarization conversion element 113, and outputs a detection result according to the amount of light (and chromaticity) of the detected light.

[0017] The Y and B light, converted to S-polarized light, are emitted from the polarization conversion element 113 and incident on an optical separator 115 that separates the B and Y light via a lens 114. The optical separator 115 includes, for example, a first dichroic mirror that reflects light in the wavelength band of the B light and transmits light in the wavelength band of the Y light, and a second dichroic mirror that reflects light in the wavelength band of the Y light and transmits light in the wavelength band of the B light. The B light separated by the optical separator 115 is emitted from the optical separator 115 and incident on a mirror 116. The Y light separated by the optical separator 115 is emitted from the optical separator 115 and incident on a mirror 121.

[0018] The B light incident on the mirror 116 is incident on the reflective polarizer 118 via the lens 117. The reflective polarizer 118 transmits one of the S-polarized and P-polarized light and reflects the other. Here, the B light emitted from the lens 117 is S-polarized, and the light reflected at the white level (maximum gradation) by the reflective optical modulation element 119, which is driven based on the B-color video data among the RGB video data described later, is P-polarized, and the reflective polarizer 118 has the characteristic of transmitting S-polarized light and reflecting P-polarized light.

[0019] The B light transmitted through the reflective polarizer 118 is incident on the reflective optical modulator 119. The reflective optical modulator 119 is driven according to the B-color image data and modulates and reflects the incident light pixel by pixel before emitting it. As the reflective optical modulator 119, a reflective liquid crystal element such as LCOS (Liquid crystal on silicon) can be used. This is also true for the other reflective optical modulators 125 and 128 described later.

[0020] The B light, which is modulated pixel by pixel according to the B-color image data by the reflective light modulation element 119, is reflected by the reflective polarizer 118, its direction is changed, and it is emitted and incident on the photosynthetic prism 120 from the first surface.

[0021] The Y light separated by the light separator 115 and incident on the mirror 121 is reflected by the mirror 121, its direction is changed, and it is emitted from the mirror 121. The Y light emitted from the mirror 121 is incident on the color component separator 122, where the green light component and the red light component are separated from the Y light. For example, the color component separator 122 is constructed using a dichroic mirror that reflects light in the green light wavelength band and transmits light in the red light wavelength band.

[0022] The green component light (green light; hereinafter referred to as G light) separated from the Y light by the color component separator 122 is incident on the reflective polarizer 124 via the lens 123. Assuming that the G light is S-polarized, similar to the B light described above, the G light passes through the reflective polarizer 124 and is incident on the reflective optical modulator 125, which is driven according to the G-color image data. The reflective optical modulator 125 modulates and reflects the incident G light pixel by pixel according to the G-color image data and emits it. The G light emitted from the reflective optical modulator 125 is reflected by the reflective polarizer 124 and incident on the photosynthetic prism 120 from a second surface.

[0023] The red component light (red light; hereinafter referred to as R light) separated from the Y light by the color component separator 122 is incident on the reflective polarizer 127 via the lens 126. Assuming that the R light is S-polarized, similar to the B light described above, the R light passes through the reflective polarizer 127 and is incident on the reflective optical modulator 128, which is driven according to the R-color image data. The reflective optical modulator 128 modulates and reflects the incident R light pixel by pixel according to the R-color image data and emits it. The R light emitted from the reflective optical modulator 128 is reflected by the reflective polarizer 127 and incident on the photosynthetic prism 120 from a third surface.

[0024] The photosynthetic prism 120 combines B light, G light, and R light incident from the first, second, and third surfaces, respectively, and emits them as a single beam of light from the fourth surface. The beam of light, including R light, G light, and B light, emitted from the photosynthetic prism 120 is then emitted to the outside via the projection optical system (projection optical unit) 129.

[0025] Figure 2 is a block diagram showing an example configuration of the projection device 1 according to Embodiment 1, focusing on the signal processing system. In the optical system configuration shown in Figure 2, the light source 11 corresponds to the light source 500 in Figure 1, and other components of the light source unit 2 in Figure 1 are omitted in Figure 2. Also, in Figure 2, the reflective optical modulation element 13 corresponds to the reflective optical modulation element 119 to which light B is irradiated in Figure 1, and the reflective polarizer 12 corresponds to the reflective polarizer 118 in Figure 1. Furthermore, the projection optical system 14 in Figure 2 corresponds to the projection optical system 129 in Figure 1.

[0026] In Figure 2, light 20 emitted from a light source 11, which includes, for example, multiple laser diodes (semiconductor lasers), is incident on the first surface of the reflective polarizer 12. As explained in Figure 1 with respect to the reflective polarizer 118, the reflective polarizer 12 transmits S-polarized light and reflects P-polarized light. When light 20 is S-polarized, it passes through the reflective polarizer 12 and irradiates the reflective optical modulation element 13. The reflective optical modulation element 13 is driven by a display element drive unit 31, which will be described later, according to the video data, and modulates and reflects the incident light 20 according to the video data, emitting it as light 21.

[0027] In this case, the light 21 is modulated according to the video data by a reflective light modulation element 13 driven based on the video data of each RGB color. When the video data is at the white level (maximum gradation), the light 21 is emitted as P-polarized light. When the video data is at the black level (minimum gradation), the light 21 is emitted as S-polarized light. Furthermore, when the video data is at a gray level between the white and black levels, the light 21 is emitted with a mixture of P-polarized and S-polarized components according to the gradation.

[0028] Light 21 is incident on the second surface of the reflective polarizer 12, and in accordance with the modulation of the reflective optical modulator 13, the P-polarized component is incident on the projection optical system 14 as light 22 and projected onto the projection medium 15, such as a screen. The S-polarized component of light 21 passes through the reflective polarizer 12 and returns to the light source 11 as light 23. This light 23 that passes through the reflective polarizer 12 and returns to the light source 11 will be referred to as "reflected light" below. As described above, reflected light occurs when the gradation of the video data is not at the white level.

[0029] In the example shown in Figure 1 above, for example, the S-polarized component of the light reflected by the reflective optical modulator 119 passes through the reflective polarizer 118 as reflected light and enters the lens 117. From there, it follows the reverse of the optical path it took when it entered the light, passing through the mirror 116, optical separator 115, lens 114, polarization conversion element 113, and fly-eye lenses 112 and 111 before entering the mirror 110. The reflected light is then reflected by the mirror 110 and emitted towards the light source 2. In the polarization conversion element 113 in the optical path of this reflected light, the leaked light from the reflected light, along with the leaked light from the light source 2, is detected by the light sensor 10.

[0030] In Figure 2, the projection device 1 includes, as part of its signal processing system, an image processing unit 30, a display element drive unit 31, a light source intensity calculation block (arithmetic processing circuit) 32, a light source drive control unit (adjustment circuit) 33, a light source drive unit (drive circuit) 34, and an intensity storage unit (storage circuit) 35. Of these, for example, the image processing unit 30, the light source intensity calculation block 32, and the light source drive control unit 33 may be configured by programs running on a CPU (Central Processing Unit) mounted on the projection device 1, or some or all of them may be configured by hardware circuits that work together.

[0031] The video processing unit 30 receives input video data from, for example, an external device connected to the projection device 1. The input video data includes, for example, pixel data for each of the R, G, and B colors, and is input in frame units at a predetermined frame rate. The video processing unit 30 applies predetermined video processing, such as gamma correction processing using a gamma value γ, to the supplied input video data and outputs it. The video data output from the video processing unit 30 is supplied to the display element drive unit 31 and the light source light intensity calculation block 32.

[0032] The display element drive unit 31 generates a drive signal for driving the reflective optical modulation element 13 based on the video data supplied from the video processing unit 30. This drive signal is supplied to the reflective optical modulation element 13. The reflective optical modulation element 13 is driven pixel by pixel according to the drive signal supplied from the display element drive unit 31.

[0033] The light source intensity calculation block 32 receives video data from the video processing unit 30, as well as the detection result from the light sensor 10. The detection result from the light sensor 10 is a signal corresponding to the light intensity (and chromaticity) of the light detected by the light sensor 10. Here, the light sensor 10 detects light 20 emitted from the light source 11 and light 23 that is reflected by the reflective light modulation element 13 and transmitted through the reflective polarizer 12. The detection result from the light sensor 10 is a signal corresponding to the total light intensity obtained by adding the light intensity of light 20 and light intensity of light 23.

[0034] The light source intensity calculation block 32 calculates a value indicating the amount of reflected light based on the video data supplied from the video processing unit 30, and uses the calculated value indicating the amount of reflected light and the detection result of the light sensor 10 to determine the light intensity Lo of the light 20 from the light source 11. The light source intensity calculation block 32 then supplies the light intensity Lo to the light source drive control unit 33.

[0035] The light source drive control unit 33 generates a drive control signal to control the light intensity of the light source 11 and supplies the generated drive control signal to the light source drive unit 34. The light source drive unit 34 drives the light source 11 according to this drive control signal and emits light 20 at a light intensity corresponding to the drive control signal.

[0036] Here, the light intensity memory unit 35 is connected to the light source drive control unit 33. The light intensity memory unit 35 is, for example, a non-volatile memory built into the projection device 1, which stores in advance a reference value Lref that indicates the reference light intensity of the light source 11. The value is stored in the light intensity memory unit 35, for example, when the projection device 1 is shipped from the factory or when the system is set up.

[0037] The light source drive control unit 33 compares the light intensity Lo supplied from the light source light intensity calculation block 32 with a reference value Lref of light intensity stored in the light intensity storage unit 35, and generates a drive control signal so that the light intensity of the light source 11 becomes equal to the light intensity according to the reference value Lref. In this way, the light intensity of the light source 11 is feedback controlled based on the detection result of the light sensor 10 and the reference value Lref stored in the light intensity storage unit 35.

[0038] Incidentally, the amount of light emitted by each of the multiple laser diodes included in the light source 11 decreases over time due to degradation, but the amount of decrease varies depending on the emission wavelength and individual variations. Therefore, the projection device 1 is required to individually measure the amount of light emitted by each of the multiple laser diodes included in the light source 11 when they are lit using the light sensor 10, and to individually feedback control the amount of light emitted by each of the multiple laser diodes when they are lit.

[0039] Therefore, the projection device 1 individually measures the light intensity of each of the multiple laser diodes included in the light source 11 by sequentially selecting and lighting each of them. Furthermore, to prevent the temperature of the non-measured laser diodes from becoming too low compared to the temperature during image projection (normal operation) while the light intensity of the lit laser diodes being measured is being measured, the projection device 1 temporarily supplies a current value higher than that used during image projection to each laser diode outside of the measurement period. As a result, the projection device 1 can accurately measure the light intensity of each of the multiple laser diodes while they are lit under temperature conditions close to (ideally the same as) those used during image projection. A detailed explanation follows below.

[0040] First, the method for measuring the light intensity of each laser diode LD1 to LD3 by the projection device 1 according to Embodiment 1 will be explained using Figure 3. Figure 3 is a timing chart showing the method for measuring the light intensity of each laser diode LD1 to LD3 by the projection device 1 according to Embodiment 1. In this embodiment, the case in which the light source 11 has laser diodes LD1 to LD3 that emit blue light with different wavelengths, such as 435 nm, 445 nm, and 455 nm, will be explained as an example. Here, the light source drive unit 34, the light sensor 10, the light source light intensity calculation block 32, the light source drive control unit 33, the light source drive unit 34, and the light intensity storage unit 35 constitute a light intensity measuring device.

[0041] Figure 3 shows the timing chart of the current values ​​supplied to each of the laser diodes LD1 to LD3 when the operating mode is light intensity measurement mode. Figure 3 also shows the timing chart of the current values ​​supplied to each of the laser diodes LD1 to LD3 when the operating mode is image projection mode.

[0042] Here, the image projection mode is the operating mode in which an image is projected onto the projection medium by the projection device 1, and the light intensity measurement mode is the operating mode in which the light intensity of each of the laser diodes LD1 to LD3 contained in the light source 11 is measured when they are lit.

[0043] First, when the operating mode is image projection mode, the light source drive unit 34 drives each laser diode LD1 to LD3 by continuously supplying a current of value I0 to each laser diode LD1 to LD3 (time t0 to t12). As a result, each laser diode LD1 to LD3 lights up (emits light).

[0044] Next, when the operating mode is light intensity measurement mode, the light source drive unit 34 periodically executes a process for a predetermined period T. Here, during the predetermined period T, the light source drive unit 34 drives the laser diodes LD1 to LD3 one by one by supplying a current of current value I0 to each of them in sequence. As a result, the laser diodes LD1 to LD3 light up (emit light) one by one in sequence. The light sensor 10 detects the lit laser diodes LD1 to LD3 one by one in sequence. The light source light intensity calculation block 32 individually measures the light intensity of each laser diode LD1 to LD3 while it is lit, based on the detection results from the light sensor 10. Then, the light source light intensity calculation block 32 individually calculates the average value of the light intensity of each laser diode LD1 to LD3 while it is lit, based on multiple measurement results from calculation processes over multiple predetermined periods T.

[0045] More specifically, the predetermined period T consists of a first period in which light intensity is measured (times t0-t3 and t6-t9) and a second period in which light intensity is not measured (times t3-t6 and t9-t12).

[0046] During the first period, the light source drive unit 34 first supplies a current of value I0 to the laser diode LD1 and stops supplying current to the laser diodes LD2 and LD3 (times t0 to t1). As a result, only the laser diode LD1 lights up. At this time, the light sensor 10 detects the light intensity of only the lit laser diode LD1. The light source light intensity calculation block 32 calculates the light intensity of only the lit laser diode LD1 based on the detection result from the light sensor 10.

[0047] During the first period, the light source drive unit 34 then supplies a current of value I0 to the laser diode LD2 and stops supplying current to the laser diodes LD1 and LD3 (times t1 to t2). As a result, only the laser diode LD2 lights up. At this time, the light sensor 10 detects the light intensity of only the lit laser diode LD2. The light source light intensity calculation block 32 calculates the light intensity of only the lit laser diode LD2 based on the detection result from the light sensor 10.

[0048] During the first period, the light source drive unit 34 then supplies a current of value I0 to the laser diode LD3 and stops supplying current to the laser diodes LD1 and LD2 (times t2 to t3). As a result, only the laser diode LD3 lights up. At this time, the light sensor 10 detects the light intensity of only the lit laser diode LD3. The light source light intensity calculation block 32 calculates the light intensity of only the lit laser diode LD3 based on the detection result from the light sensor 10.

[0049] Furthermore, the illumination time for each laser diode LD1 to LD3 is set to be at least the shortest time during which the light sensor 10 can detect the amount of light.

[0050] During the second period, the light source drive unit 34 supplies a current value I1 higher than the current value I0 to each laser diode LD1 to LD3 (from time t3 to t6). This suppresses the temperature drop caused by the turning off of the laser diodes LD1 to LD3 during the first period, allowing the projection device 1 to accurately measure the light intensity of each laser diode LD1 to LD3 when lit, under temperature conditions close to those during image projection. Note that no light intensity measurement is performed during the second period.

[0051] Furthermore, it is preferable that the current value I1 be set such that the average current value supplied to each laser diode LD1 to LD3 over a predetermined period T is substantially the same as the current value I0. This allows the projection device 1 to accurately measure the light intensity of each laser diode LD1 to LD3 when lit, under substantially the same temperature conditions as when projecting an image.

[0052] Next, using Figure 4, the method for measuring the light intensity of each laser diode LD1 to LD3 using the projection device 1 according to Embodiment 1 will be explained. Figure 4 is a flowchart showing the method for measuring the light intensity of each laser diode LD1 to LD3 using the projection device 1 according to Embodiment 1.

[0053] First, the projection device 1 sets its operating mode to light intensity measurement mode (step S101). For example, the projection device 1 switches its operating mode from image projection mode to light intensity measurement mode. Accordingly, the projection device 1 switches the image display pattern output as video data from the video processing unit 30 to a fixed pattern for measurement (step S102). For example, the projection device 1 switches the image display pattern output as video data from the video processing unit 30 to a fixed pattern of all white. This suppresses reflected light.

[0054] Subsequently, during the first period of a predetermined period T, the projection device 1 supplies a current of value I0 to each of the laser diodes LD1 to LD3 in sequence, and measures the light intensity of each of the laser diodes LD1 to LD3 that are lit by the current, in sequence (steps S103 to S105). The measurement results, along with additional information such as the cumulative usage time of the light source, are stored in the light intensity storage unit 35 (step S106).

[0055] Subsequently, during the second period of the predetermined period T, the projection device 1 supplies a current value I1 higher than the current value I0 to each of the laser diodes LD1 to LD3 (step S107). This suppresses the temperature drop caused by the turning off of the laser diodes LD1 to LD3, allowing the projection device 1 to accurately measure the light intensity of each laser diode LD1 to LD3 when lit, under temperature conditions close to those during image projection. Note that no light intensity measurement is performed during the second period.

[0056] Subsequently, if the number of processing cycles for the predetermined period T has not reached a preset number (NO in step S108), the projection device 1 returns to the processing in steps S103 to S107. If the number of processing cycles for the predetermined period T has reached a preset number (YES in step S108), the light intensity measurement mode processing is terminated. The preset number of cycles is basically two or more, but it may be one cycle if the temperature is stable. The projection device 1 calculates the average value of the light intensity measurement results for the preset number of cycles and stores it in the light intensity storage unit 35 as the final measurement result.

[0057] As described above, the projection device 1 according to this embodiment individually measures the light intensity of each laser diode LD1 to LD3 when it is lit by sequentially selecting and lighting each laser diode LD1 to LD3 included in the light source 11. Furthermore, in order to prevent the temperature of the unlit laser diodes (not being measured) from becoming too low compared to the temperature during image projection (normal operation) while the light intensity of the lit laser diodes being measured is being measured, the projection device 1 temporarily supplies a current value higher than that used during image projection to each laser diode LD1 to LD3 outside of the measurement period. As a result, the projection device 1 can accurately measure the light intensity of each laser diode LD1 to LD3 when it is lit under temperature conditions close to (ideally the same as) those used during image projection.

[0058] The timing at which the operating mode is set to the light intensity measurement mode can be arbitrary, but it is preferable to set it at the timing when the power is turned off after the projection device 1 has been operating in the image projection mode. This allows the projection device 1 to measure the light intensity of each of the laser diodes LD1 to LD3, which are in a state where their temperature has stabilized by operating in the image projection mode. Furthermore, this makes it easier for the projection device 1 to switch the image display pattern output as image data from the image processing unit 30 to a fixed pattern of all white that suppresses reflected light.

[0059] Furthermore, although this embodiment describes an example where the light source 11 is composed of three laser diodes LD1 to LD3, it is not limited to this. The light source 11 may be composed of any number of laser diodes, two or more.

[0060] Furthermore, in this embodiment, the case where the current value supplied to each laser diode LD1 to LD3 is constant when the operating mode is image projection mode has been described as an example, but the invention is not limited to this. Even when the operating mode is image projection mode, current may be supplied to each laser diode LD1 to LD3 by the same current control as when the operating mode is light intensity measurement mode. As a result, the projection device 1 can drive each laser diode LD1 to LD3 by a common current control regardless of the operating mode. In this case, it is preferable to set the predetermined period T to 14 ms or less in order to suppress image flicker.

[0061] Furthermore, in this embodiment, the current values ​​supplied to each laser diode LD1 to LD3 are described as constant during the second period of a predetermined period T, but the embodiment is not limited to this, and the current values ​​do not have to be constant. However, it is preferable for the current values ​​to be constant in order to suppress image flicker.

[0062] Furthermore, although this embodiment describes the case where the light intensity measurements of each laser diode LD1 to LD3 are performed continuously without intervals, it is not limited to this. The light intensity measurements of each laser diode LD1 to LD3 may be performed sequentially with intervals in between. This allows the projection device 1 to perform processing by the light sensor 10 and the light source light intensity calculation block 32, communication between the light sensor 10 and the light source light intensity calculation block 32, and saving the measurement results to the light intensity storage unit 35 during periods when light intensity measurements are not being performed.

[0063] Furthermore, in this embodiment, the projection device 1 was described as measuring the light intensity of each laser diode LD1 to LD3 individually when they are lit by sequentially selecting and lighting each laser diode LD1 to LD3 included in the light source 11, but the invention is not limited to this. The projection device 1 may also measure the light intensity of each group of laser diodes individually when they are lit by sequentially selecting and lighting each group of laser diodes that have a common wavelength. As a result, the projection device 1 can reduce the number of light intensity measurements compared to the case where each laser diode is selected sequentially, thereby shortening the measurement period and suppressing the temperature drop of the multiple laser diodes. Consequently, the projection device 1 can measure the light intensity of each group of laser diodes with greater accuracy.

[0064] For example, if the light source 11 is composed of laser diodes LD1 to LD4 with an emission wavelength of 435 nm, laser diodes LD5 to LD8 with an emission wavelength of 445 nm, and laser diodes LD9 to LD12 with an emission wavelength of 455 nm, first, the projection device 1 measures the light intensity of the group of laser diodes LD1 to LD4 by selecting and lighting up the group of laser diodes LD1 to LD4 that have a common wavelength. Then, the projection device 1 measures the light intensity of the group of laser diodes LD5 to LD8 by selecting and lighting up the group of laser diodes LD5 to LD8 that have a common wavelength. Then, the projection device 1 measures the light intensity of the group of laser diodes LD9 to LD12 by selecting and lighting up the group of laser diodes LD9 to LD12 that have a common wavelength.

[0065] <Embodiment 2> In Embodiment 2, the method for measuring the light intensity of each of the laser diodes LD1 to LD3 included in the light source 11 is different from that in Embodiment 1. This will be explained in detail below.

[0066] First, the method for measuring the light intensity of each laser diode LD1 to LD3 by the projection device 1 according to Embodiment 2 will be explained using Figure 5. Figure 5 is a timing chart showing the method for measuring the light intensity of each laser diode LD1 to LD3 by the projection device 1 according to Embodiment 2. In this embodiment, the case in which the light source 11 has laser diodes LD1 to LD3 that emit blue light with different wavelengths, such as 435 nm, 445 nm, and 455 nm, will be explained as an example. Here, the light source drive unit 34, the light sensor 10, the light source light intensity calculation block 32, the light source drive control unit 33, the light source drive unit 34, and the light intensity storage unit 35 constitute a light intensity measuring device.

[0067] Figure 5 shows the timing chart of the current values ​​supplied to each of the laser diodes LD1 to LD3 when the operating mode is light intensity measurement mode. Figure 5 also shows the timing chart of the current values ​​supplied to each of the laser diodes LD1 to LD3 when the operating mode is image projection mode.

[0068] First, when the operating mode is image projection mode, the light source drive unit 34 drives each laser diode LD1 to LD3 by continuously supplying a current of value I0 to each laser diode LD1 to LD3 (time t0 to t12). As a result, each laser diode LD1 to LD3 lights up (emits light).

[0069] Next, when the operating mode is light intensity measurement mode, the light source drive unit 34 periodically performs processing for a predetermined period T. Here, during the predetermined period T, the light source drive unit 34 sequentially selects laser diodes LD1 to LD3 one by one, stops supplying current to the selected diode, and supplies a current of current value I0 to the two unselected diodes, thereby driving pairs of laser diodes LD1 to LD3 sequentially. As a result, laser diodes LD1 to LD3 light up (emit light) one pair at a time. The light sensor 10 sequentially detects the light intensity of the paired laser diodes LD1 to LD3. The light source light intensity calculation block 32 individually calculates the light intensity of each laser diode LD1 to LD3 while they are lit, based on the detection results from the light sensor 10. Then, the light source light intensity calculation block 32 individually calculates the average value of the light intensity of each laser diode LD1 to LD3 while they are lit, from multiple calculation results obtained from calculation processing over multiple predetermined periods T.

[0070] More specifically, the predetermined period T consists of a first period in which light intensity is measured (times t0-t3 and t6-t9) and a second period in which light intensity is not measured (times t3-t6 and t9-t12).

[0071] During the first period, the light source drive unit 34 first stops supplying current to the laser diode LD1 and supplies a current of value I0 to each of the laser diodes LD2 and LD3 (times t0 to t1). As a result, the laser diodes LD2 and LD3 light up. At this time, the light sensor 10 detects the combined light from the lit laser diodes LD2 and LD3. The light source light intensity calculation block 32 calculates the combined light intensity K23 of the lit laser diodes LD2 and LD3 based on the detection result from the light sensor 10.

[0072] During the first period, the light source drive unit 34 then stops supplying current to the laser diode LD2 and supplies a current of value I0 to each of the laser diodes LD1 and LD3 (times t1 to t2). As a result, the laser diodes LD1 and LD3 light up. At this time, the light sensor 10 detects the combined light from the lit laser diodes LD1 and LD3. The light source light intensity calculation block 32 calculates the combined light intensity K13 of the lit laser diodes LD1 and LD3 based on the detection result from the light sensor 10.

[0073] During the first period, the light source drive unit 34 then stops supplying current to the laser diode LD3 and supplies a current of value I0 to each of the laser diodes LD1 and LD2 (times t2 to t3). As a result, the laser diodes LD1 and LD2 light up. At this time, the light sensor 10 detects the combined light from the lit laser diodes LD1 and LD2. The light source light intensity calculation block 32 calculates the combined light intensity K12 of the lit laser diodes LD1 and LD2 based on the detection result from the light sensor 10.

[0074] Then, the light source intensity calculation block 32 calculates the respective light intensity of laser diodes LD1, LD2, and LD3 from the sum of the above light intensity values ​​K23, K13, and K12.

[0075] Furthermore, the illumination time for each laser diode LD1 to LD3 is set to be at least the shortest time during which the light sensor 10 can detect the amount of light.

[0076] Here, if we let K1 be the light intensity of laser diode LD1, K2 be the light intensity of laser diode LD2, and K3 be the light intensity of laser diode LD3, then the sum of the light intensity of laser diodes LD2 and LD3, K23, the sum of the light intensity of laser diodes LD1 and LD3, K13, and the sum of the light intensity of laser diodes LD1 and LD2, K12, can be expressed as shown in equations (1), (2), and (3) below, respectively.

[0077] K23 = K2 + K3 ... (1) K13 = K1 + K3 ... (2) K12 = K1 + K2 ... (3)

[0078] Furthermore, from equations (1), (2), and (3), the light intensities K1 to K3 of the laser diodes LD1 to LD3 can be expressed as shown in equations (4), (5), and (6) below.

[0079] K1 = (K12 + K13 - K23) / 2 ... (4) K2 = (K12 + K23 - K13) / 2 ... (5) K3 = (K23 + K13 - K12) / 2 ... (6)

[0080] Therefore, the light source light intensity calculation block 32 can calculate the light intensities K1 to K3 of the laser diodes LD1 to LD3 from the light intensities K23, K13, and K12 using equations (4), (5), and (6).

[0081] During the second period, the light source drive unit 34 supplies a current value I2 higher than current value I0 to each laser diode LD1 to LD3 (times t3 to t6). This suppresses the temperature drop caused by the turning off of the laser diodes LD1 to LD3 during the first period, allowing the projection device 1 to accurately measure the light intensity of each laser diode LD1 to LD3 when lit, under temperature conditions close to those during image projection. Note that no light intensity measurement is performed during the second period.

[0082] Furthermore, it is preferable that the current value I2 be set such that the average current value supplied to each laser diode LD1 to LD3 over a predetermined period T is substantially the same as the current value I0. This allows the projection device 1 to accurately measure the light intensity of each laser diode LD1 to LD3 when lit, under substantially the same temperature conditions as when projecting an image.

[0083] Next, the method for measuring the light intensity of each laser diode LD1 to LD3 using the projection device 1 according to Embodiment 2 will be explained with reference to Figure 6. Figure 6 is a flowchart showing the method for measuring the light intensity of each laser diode LD1 to LD3 using the projection device 1 according to Embodiment 2.

[0084] First, the projection device 1 sets its operating mode to light intensity measurement mode (step S201). For example, the projection device 1 switches its operating mode from image projection mode to light intensity measurement mode. Accordingly, the projection device 1 switches the image display pattern output as video data from the video processing unit 30 to a fixed pattern for measurement (step S202). For example, the projection device 1 switches the image display pattern output as video data from the video processing unit 30 to a fixed pattern of all white. This suppresses reflected light.

[0085] Subsequently, during the first period of a predetermined period T, the projection device 1 sequentially supplies a current of current value I0 to the laser diodes LD1 to LD3 in pairs, and measures the light intensity of each pair of laser diodes LD1 to LD3 that have been lit together (steps S203 to S205). Then, the projection device 1 calculates the light intensity of each laser diode LD1 to LD3 from the light intensity K23, K13, and K12 of each pair, for example, by using equations (4), (5), and (6) (step S206). The calculation results are stored in the light intensity storage unit 35 along with additional information such as the cumulative usage time of the light source (step S207).

[0086] Subsequently, during the second period of the predetermined period T, the projection device 1 supplies a current value I2 higher than the current value I0 to each of the laser diodes LD1 to LD3 (step S208). This suppresses the temperature drop caused by the turning off of the laser diodes LD1 to LD3, allowing the projection device 1 to accurately measure the light intensity of each laser diode LD1 to LD3 when lit, under temperature conditions close to those during image projection. Note that no light intensity measurement is performed during the second period.

[0087] Subsequently, if the number of processing cycles for the predetermined period T has not reached a preset number (NO in step S209), the projection device 1 returns to the processing in steps S203 to S208. If the number of processing cycles for the predetermined period T has reached a preset number (YES in step S209), the light intensity measurement mode processing is terminated. The preset number of cycles is basically two or more, but it may be one cycle if the temperature is stable. The projection device 1 calculates the average value of the light intensity measurement results for the preset number of cycles and stores it in the light intensity storage unit 35 as the final measurement result.

[0088] As described above, the projection device 1 according to this embodiment individually measures the light intensity of each laser diode LD1 to LD3 when it is lit by sequentially selecting and lighting up pairs of laser diodes LD1 to LD3 included in the light source 11. Furthermore, in order to prevent the temperature of the unlit laser diodes (not being measured) from becoming too low compared to the temperature during image projection (normal operation) while the light intensity of the lit laser diodes being measured is being measured, the projection device 1 temporarily supplies a current value higher than that used during image projection to each laser diode LD1 to LD3 outside of the measurement period. As a result, the projection device 1 can accurately measure the light intensity of each lit laser diode LD1 to LD3 under temperature conditions close to (ideally the same as) those used during image projection.

[0089] The timing at which the operating mode is set to the light intensity measurement mode can be arbitrary, but it is preferable to set it at the timing when the power is turned off after the projection device 1 has been operating in the image projection mode. This allows the projection device 1 to measure the light intensity of each of the laser diodes LD1 to LD3, which are in a state where their temperature has stabilized by operating in the image projection mode. Furthermore, this makes it easier for the projection device 1 to switch the image display pattern output as image data from the image processing unit 30 to a fixed pattern of all white that suppresses reflected light.

[0090] Furthermore, although this embodiment describes an example where the light source 11 is composed of three laser diodes LD1 to LD3, it is not limited to this. The light source 11 may be composed of any number of laser diodes, two or more.

[0091] Furthermore, in this embodiment, the case where the current value supplied to each laser diode LD1 to LD3 is constant when the operating mode is image projection mode has been described as an example, but the invention is not limited to this. Even when the operating mode is image projection mode, current may be supplied to each laser diode LD1 to LD3 by the same current control as when the operating mode is light intensity measurement mode. As a result, the projection device 1 can drive each laser diode LD1 to LD3 by a common current control regardless of the operating mode. In this case, it is preferable to set the predetermined period T to 14 ms or less in order to suppress image flicker.

[0092] Furthermore, in this embodiment, the current values ​​supplied to each laser diode LD1 to LD3 are described as constant during the second period of a predetermined period T, but the embodiment is not limited to this, and the current values ​​do not have to be constant. However, it is preferable for the current values ​​to be constant in order to suppress image flicker.

[0093] Furthermore, although this embodiment describes the case in which the light intensities K23, K13, and K12 are measured continuously without intervals, it is not limited to this. The light intensities K23, K13, and K12 may be measured sequentially with intervals in between. This allows the projection device 1 to perform processing by the light sensor 10 and the light source light intensity calculation block 32, communication between the light sensor 10 and the light source light intensity calculation block 32, and saving the measurement results to the light intensity storage unit 35 during periods when light intensity measurements are not being performed.

[0094] Furthermore, in this embodiment, the projection device 1 was described as measuring the light intensity of each laser diode LD1 to LD3 individually when lit by sequentially selecting each laser diode LD1 to LD3 included in the light source 11, stopping the supply of current to the selected laser diode, and lighting up the remaining unselected laser diodes. However, the invention is not limited to this. The projection device 1 may sequentially select multiple laser diodes included in the light source 11 in groups of two or more laser diodes having a common wavelength, stopping the supply of current to the selected group of laser diodes, and lighting up the remaining unselected laser diodes, thereby measuring the light intensity of each group of multiple laser diodes individually when lit. As a result, the projection device 1 can reduce the number of light intensity measurements compared to the case where multiple laser diodes are selected one by one, thereby shortening the light intensity measurement period and suppressing the temperature drop of the multiple laser diodes. Consequently, the projection device 1 can measure the light intensity of each group of multiple laser diodes with greater accuracy.

[0095] For example, if the light source 11 is composed of laser diodes LD1 to LD4 with an emission wavelength of 435 nm, laser diodes LD5 to LD8 with an emission wavelength of 445 nm, and laser diodes LD9 to LD12 with an emission wavelength of 455 nm, first, the projection device 1 selects the group of laser diodes LD1 to LD4 that have a common wavelength, stops the supply of current to the selected laser diodes LD1 to LD3, and turns on the remaining unselected laser diodes LD4 to LD12 to measure the light intensity K23'. Subsequently, the projection device 1 selects the group of laser diodes LD5 to LD8 that have a common wavelength, stops the supply of current to the selected laser diodes LD5 to LD8, and turns on the remaining unselected laser diodes LD1 to LD4 and LD9 to LD12 to measure the light intensity K13'. Subsequently, projection device 1 selects a group of laser diodes LD9 to LD12 that share a common wavelength, stops supplying current to the selected laser diodes LD9 to LD12, and turns on the remaining unselected laser diodes LD1 to LD8 to measure the light intensity K12'. Then, projection device 1 calculates the light intensity of each laser diode LD1 to LD12 from the measured values ​​of light intensity K23', K13', and K12'. The method for calculating the light intensity at this time is basically the same as the calculation method using equations (1) to (6) described above, so its explanation is omitted.

[0096] <Embodiment 3> As mentioned above, the amount of light emitted by each of the multiple laser diodes in the light source 11 decreases over time due to degradation, but the amount of decrease varies depending on the emission wavelength and individual variations. Therefore, in projection devices of related technologies, there was a problem that the emission spectrum of the light source 11 changed due to degradation over time, and consequently, the color (chromaticity) of the image changed from the color before degradation.

[0097] Therefore, the projection device 1 according to Embodiment 3 compares the measurement results of the chromaticity of the light emitted from the light source 11 before and after aging degradation, and adjusts the current supplied to each of the multiple laser diodes individually based on the comparison results, so that the chromaticity of the light emitted from the light source 11 after aging degradation becomes close to the chromaticity before aging degradation. Here, in order to prevent the temperature of the off-light laser diodes, which are not the target of measurement, from becoming too low compared to the temperature during image projection (normal operation) while the chromaticity of the lit laser diodes, which are the target of measurement, is being measured, the projection device 1 temporarily supplies a current with a higher current value than that during image projection to specific laser diodes outside the measurement period. As a result, the projection device 1 can accurately measure and adjust the chromaticity of the light emitted from the light source 11 under temperature conditions close to (ideally the same as) those during image projection. A detailed explanation follows below.

[0098] First, the chromaticity measurement method using the projection device 1 according to Embodiment 3 will be explained using Figure 7. Figure 7 is a timing chart showing the chromaticity measurement method using the projection device 1 according to Embodiment 3. In this embodiment, the example will be described in which the light source 11 has laser diodes LD1 to LD3 that emit blue light of different wavelengths, such as 435 nm, 445 nm, and 455 nm. Here, the light source drive unit 34, the light sensor 10, the light source light quantity calculation block 32, the light source drive control unit 33, the light source drive unit 34, and the light quantity storage unit 35 constitute a chromaticity adjustment device.

[0099] Figure 7 shows the timing chart of the current values ​​supplied to each of the laser diodes LD1 to LD3 when the operating mode is chromaticity measurement mode. Figure 7 also shows the timing chart of the current values ​​supplied to each of the laser diodes LD1 to LD3 when the operating mode is image projection mode.

[0100] Here, the image projection mode is the operating mode in which an image is projected onto the projection medium by the projection device 1, and the chromaticity measurement mode is the operating mode in which the chromaticity of the light emitted from the light source 11 is measured. In addition, the brightness of the light emitted from the light source 11 may also be measured in the chromaticity measurement mode. The operating modes further include a chromaticity adjustment mode in which the chromaticity of the light emitted from the light source 11 is adjusted. In addition, the brightness of the light emitted from the light source 11 may also be adjusted in the chromaticity adjustment mode.

[0101] The following describes the case where the measurement and adjustment of chromaticity after a specified period has elapsed since the product was shipped or before it deteriorated over time (the reference point).

[0102] First, when the operating mode is image projection mode, the light source drive unit 34 drives each laser diode LD1 to LD3 by continuously supplying a current of value I0 to each laser diode LD1 to LD3 (time t0 to t10). As a result, each laser diode LD1 to LD3 lights up (emits light).

[0103] Next, when the operating mode is chromaticity measurement mode, the light source drive unit 34 periodically performs processing for a predetermined period T. Here, during the predetermined period T, the light source drive unit 34 first supplies a current of current value I0 to each of the laser diodes LD1 and LD2, and then supplies a current of current value I0 to each of the laser diodes LD1 and LD3. As a result, first the laser diodes LD1 and LD2 light up, and then the laser diodes LD1 and LD3 light up. The light sensor 10 first detects the combined light from the lit laser diodes LD1 and LD2, and then detects the combined light from the lit laser diodes LD1 and LD3. The light source light quantity calculation block 32 calculates the chromaticity of the lit laser diodes LD1 and LD2 based on the detection results from the light sensor 10, and then calculates the chromaticity of the lit laser diodes LD1 and LD3. The light source intensity calculation block 32 then calculates the average value of the chromaticity of laser diodes LD1 and LD2 while they are lit, and the average value of the chromaticity of laser diodes LD1 and LD3 while they are lit, from multiple calculation results obtained from calculation processes over multiple predetermined periods T.

[0104] More specifically, the predetermined period T consists of a first period in which chromaticity measurements are taken (times t0-t2 and t5-t7) and a second period in which chromaticity measurements are not taken (times t2-t5 and t7-t10).

[0105] During the first period, the light source drive unit 34 first supplies a current of value I0 to each of the laser diodes LD1 and LD2, and stops supplying current to the laser diode LD3 (times t0 to t1). As a result, the laser diodes LD1 and LD2 light up. At this time, the light sensor 10 detects the combined light from the lit laser diodes LD1 and LD2. The light source light intensity calculation block 32 calculates the chromaticity C12 of the combined light from the lit laser diodes LD1 and LD2 based on the detection result from the light sensor 10.

[0106] During the first period, the light source drive unit 34 then supplies a current of value I0 to each of the laser diodes LD1 and LD3, and stops supplying current to the laser diode LD2 (times t1 to t2). As a result, the laser diodes LD1 and LD3 light up. At this time, the light sensor 10 detects the combined light from the lit laser diodes LD1 and LD3. The light source light intensity calculation block 32 calculates the chromaticity C13 of the combined light from the lit laser diodes LD1 and LD3 based on the detection result from the light sensor 10.

[0107] Furthermore, the illumination time for each laser diode LD1 to LD3 is set to be at least the shortest time during which light can be detected by the light sensor 10.

[0108] During the second period, the light source drive unit 34 continues to supply a current of value I0 to the reference laser diode LD1, as in the first period (times t2 to t5). In addition, during the second period, the light source drive unit 34 supplies a current of value I3, which is higher than the current value I0, to each of the laser diodes LD2 and LD3, which were not lit during the first period (times t2 to t5). As a result, the temperature drop caused by the extinguishing of laser diodes LD2 and LD3 during the first period is suppressed, and the projection device 1 can accurately measure the chromaticity of the light emitted from the light source 11 under temperature conditions close to those during image projection. Note that no measurement of the chromaticity of the light is performed during the second period.

[0109] Furthermore, it is preferable that the current value I3 be set such that the average current value supplied to each laser diode LD1 to LD3 over a predetermined period T is substantially the same as the current value I0. This allows the projection device 1 to accurately measure the chromaticity of the light emitted from the light source 11 under substantially the same temperature conditions as when projecting an image.

[0110] In this embodiment, the case where the reference laser diode is laser diode LD1 was described as an example, but it is not limited to this. The reference laser diode may be any of laser diodes LD1 to LD3. However, it is preferable that the reference laser diode is the laser diode with the shortest wavelength or the longest wavelength among laser diodes LD1 to LD3. This increases the difference in chromaticity between the light chromaticity of the reference laser diode and the light chromaticity of the laser diode paired with the reference laser diode during chromaticity measurement, making it easier to detect changes in chromaticity before and after aging.

[0111] Furthermore, if the chromaticity of each laser diode LD1 to LD3 is known, the reference laser diode is preferably the laser diode with the shortest wavelength and the laser diode with the longest wavelength that has the largest chromaticity difference with the other laser diodes. Also, if the spectral sensitivity characteristics of the light sensor 10 are known, the reference laser diode is preferably the laser diode with the shortest wavelength and the laser diode with the longest wavelength that has the highest sensitivity to the light sensor 10. Moreover, if the peak sensitivity wavelength of the light sensor 10 is known, the reference laser diode is preferably the laser diode with the shortest wavelength and the laser diode with the longest wavelength that is close to the peak sensitivity wavelength of the light sensor 10. These measures make it even easier to detect changes in chromaticity before and after aging.

[0112] When measuring brightness, the light source drive unit 34 supplies a current of value I0 to each of the laser diodes LD1 to LD3. This causes the laser diodes LD1 to LD3 to light up. At this time, the light sensor 10 detects the combined light from the lit laser diodes LD1 to LD3. The light source light intensity calculation block 32 calculates the brightness of the combined light from the lit laser diodes LD1 to LD3 based on the detection result from the light sensor 10.

[0113] Next, the chromaticity adjustment method using the projection device 1 according to Embodiment 3 will be explained with reference to Figure 8. Figure 8 is a conceptual diagram for explaining the chromaticity adjustment method using the projection device 1 according to Embodiment 3.

[0114] The light intensity memory unit 35 stores information on the chromaticity C12_ini of the combined light from laser diodes LD1 and LD2 at a point in time before aging (reference point), such as before product shipment, the chromaticity C13_ini of the combined light from laser diodes LD1 and LD3 at the reference point, and the light intensity BA_ini of the combined light from laser diodes LD1 to LD3 at the reference point. The chromaticity C12_ini, chromaticity C13_ini, and light intensity BA are measured at the reference point before aging using the same method as the measurement method for chromaticity C12, C13, and light intensity BA after aging.

[0115] Here, the ratio of the light intensity of each laser diode LD1 to LD3 is different before and after aging. Therefore, projection device 1 brings the chromaticity of the light emitted from light source 11 closer to the state before aging by bringing the ratio of the light intensity of each laser diode LD1 to LD3 after aging closer to the ratio before aging.

[0116] Specifically, first, the light source drive control unit 33 of the projection device 1 adjusts the current supplied to laser diode LD2 while keeping the current value supplied to the reference laser diode LD1 fixed, thereby bringing the combined chromaticity C12 of the light from laser diodes LD1 and LD2 closer to the chromaticity C12_ini at the reference time. Ideally, the light source drive control unit 33 makes the combined chromaticity C12 of the light from laser diodes LD1 and LD2 substantially the same as the chromaticity C12_ini at the reference time. Subsequently, the light source drive control unit 33 adjusts the current supplied to laser diode LD3 while keeping the current value supplied to the reference laser diode LD1 fixed, thereby bringing the combined chromaticity C13 of the light from laser diodes LD1 and LD3 closer to the chromaticity C13_ini at the reference time. Ideally, the light source drive control unit 33 makes the combined chromaticity C13 of the light from laser diodes LD1 and LD3 substantially the same as the chromaticity C13_ini at the reference time. As a result, the ratio of the light intensity of each laser diode LD1 to LD3 approaches the state before aging, and therefore the chromaticity of the light emitted from the light source 11 approaches the state before aging. Ideally, the ratio of the light intensity of each laser diode LD1 to LD3 becomes the same as the state before aging, and therefore the chromaticity of the light emitted from the light source 11 becomes the same as the state before aging.

[0117] When adjusting the brightness, the light source drive control unit 33 adjusts the light intensity of each laser diode LD1 to LD3 while maintaining the ratio of the light intensity of each laser diode LD1 to LD3, thereby bringing the brightness BA of the light emitted from the light source 11 closer to (ideally the same as) the brightness BA_ini at a reference point.

[0118] Next, Figures 9 to 11 will be used to explain the method for measuring the chromaticity of light before aging degradation using the projection device 1 according to Embodiment 3. Figures 9 to 11 are flowcharts showing the method for measuring the chromaticity of light before aging degradation using the projection device 1 according to Embodiment 3. In addition to the method for measuring the chromaticity of light before aging degradation, Figures 9 to 11 also show the method for measuring the brightness of light before aging degradation.

[0119] First, the projection device 1 determines whether the chromaticity of the light from the light source 11 at a reference point before aging degradation is stored in the light intensity storage unit 35 (step S301). If the chromaticity of the light from the light source 11 at a reference point is stored in the light intensity storage unit 35 (YES in step S301), the process proceeds to step S303. If the chromaticity of the light from the light source 11 at a reference point is not stored in the light intensity storage unit 35 (NO in step S301), the projection device 1 measures the chromaticity of the light from the light source 11 at a reference point and stores the measurement result (step S302).

[0120] Figure 10 shows the detailed processing of step S302, namely the detailed processing related to chromaticity measurement and saving of the measurement results. As shown in Figure 10, first, the projection device 1 sets the operating mode to chromaticity measurement mode (step S401). Accordingly, the projection device 1 switches the image display pattern output as video data from the video processing unit 30 to a fixed pattern for measurement (step S402). For example, the projection device 1 switches the image display pattern output as video data from the video processing unit 30 to a fixed pattern of all white. This suppresses reflected light.

[0121] Subsequently, during the first period of a predetermined period T, the projection device 1 supplies a current of value I0 to each of the laser diodes LD1 and LD2, then supplies a current of value I0 to each of the laser diodes LD1 and LD3, and measures the chromaticity C12_ini of the combined light from the lit laser diodes LD1 and LD2, and then measures the chromaticity C13_ini of the combined light from the lit laser diodes LD1 and LD3 (steps S403 to S405). These measurement results are stored in the light quantity storage unit 35 (step S406).

[0122] Subsequently, during the second period of the predetermined period T, the projection device 1 supplies a current value I3 higher than the current value I0 to each of the laser diodes LD2 and LD3, excluding the laser diode LD1 that remained lit during the first period (step S407). This suppresses the temperature drop caused by the extinguishing of the laser diodes LD2 and LD3, allowing the projection device 1 to accurately measure the chromaticity of the light emitted from the light source 11 under temperature conditions close to those during image projection. Note that no measurement of the chromaticity of the light is performed during the second period.

[0123] Subsequently, if the number of processing cycles for the predetermined period T has not reached a preset number (NO in step S408), the projection device 1 returns to the processing in steps S403 to S407. If the number of processing cycles for the predetermined period T has reached a preset number (YES in step S408), the chromaticity measurement mode processing is terminated. The preset number of cycles is basically two or more, but it may be one cycle if the temperature is stable. The projection device 1 calculates the average value of the chromaticity measurement results for the preset number of cycles and stores it in the light intensity storage unit 35 as the final measurement result.

[0124] Returning to Figure 9, the explanation continues. Next, the projection device 1 determines whether the brightness of the light from the light source 11 at a reference point before aging degradation is stored in the light intensity storage unit 35 (step S303). If the brightness of the light from the light source 11 at a reference point is stored in the light intensity storage unit 35 (YES in step S303), the projection device 1 terminates the measurement and storage process of the chromaticity and brightness of the light from the light source 11 at a reference point. On the other hand, if the brightness of the light from the light source 11 at a reference point is not stored in the light intensity storage unit 35 (NO in step S303), the projection device 1 measures the brightness of the light from the light source 11 at a reference point and stores the measurement results (step S304).

[0125] Figure 11 shows the detailed processing of step S304, namely the detailed processing related to brightness measurement and saving of the measurement results. As shown in Figure 11, first, the projection device 1 sets the operating mode to chromaticity measurement mode (step S501). Accordingly, the projection device 1 switches the image display pattern output as video data from the video processing unit 30 to a fixed pattern for measurement (step S502). For example, the projection device 1 switches the image display pattern output as video data from the video processing unit 30 to a fixed pattern of all white. This suppresses reflected light.

[0126] Subsequently, the projection device 1 supplies a current of value I0 to each of the laser diodes LD1 to LD3 included in the light source 11, and measures the total brightness BA_ini of the light from the lit laser diodes LD1 to LD3 (steps S503, S504). The measurement results are stored in the light intensity storage unit 35 (step S505). Then, the projection device 1 completes the measurement and storage process of the chromaticity and brightness of the light from the light source 11 at the reference time.

[0127] Next, using Figure 12, the method for measuring and adjusting the chromaticity of light after aging using the projection device 1 according to Embodiment 3 will be explained. Figure 12 is a flowchart showing the method for measuring and adjusting the chromaticity of light after aging using the projection device 1 according to Embodiment 3. In addition to the method for measuring and adjusting the chromaticity of light after aging, Figure 12 also shows the method for measuring and adjusting the brightness of light after aging.

[0128] First, the projection device 1 sets its operating mode to chromaticity adjustment mode (step S601). Accordingly, the projection device 1 switches the image display pattern output as video data from the video processing unit 30 to a fixed pattern for measurement (step S602). For example, the projection device 1 switches the image display pattern output as video data from the video processing unit 30 to a fixed pattern of all white. This suppresses reflected light.

[0129] Subsequently, projection device 1 determines whether or not to adjust the chromaticity of the light from the light source 11 after aging (step S603). If projection device 1 determines not to adjust the chromaticity of the light from the light source 11 after aging (NO in step S603), it proceeds to step S607. If it determines to adjust the chromaticity of the light from the light source 11 after aging (YES in step S603), it measures the chromaticity C12 and C13 after aging in the same manner as the chromaticity measurement method before aging (step S604).

[0130] Subsequently, projection device 1 adjusts the current supplied to laser diode LD2 while keeping the current supplied to the reference laser diode LD1 fixed, thereby bringing the combined chromaticity C12 of the light from laser diodes LD1 and LD2 closer to the chromaticity C12_ini before aging degradation (ideally, making them substantially the same) (step S605). Also, projection device 1 adjusts the current supplied to laser diode LD3 while keeping the current supplied to the reference laser diode LD1 fixed, thereby bringing the combined chromaticity C13 of the light from laser diodes LD1 and LD3 closer to the chromaticity C13_ini at the reference time (ideally, making them substantially the same) (step S606). As a result, the ratio of the light intensity of each laser diode LD1 to LD3 approaches the state before aging degradation (ideally, they become substantially the same). After that, projection device 1 proceeds to the process in step S607.

[0131] Subsequently, projection device 1 determines whether or not to adjust the brightness of the light from the light source 11 after aging (step S607). If projection device 1 determines not to adjust the brightness of the light from the light source 11 after aging (NO in step S607), it proceeds to the process in step S610. If it determines to adjust the brightness of the light from the light source 11 after aging (YES in step S607), it measures the brightness BA after aging using the same method as the brightness measurement method before aging (step S608).

[0132] Subsequently, projection device 1 adjusts the light intensity of each laser diode LD1 to LD3 while maintaining the ratio of the light intensity of each laser diode LD1 to LD3, thereby bringing the brightness BA of the light emitted from light source 11 closer to (ideally, substantially the same as) the brightness BA_ini at a reference time (step S609). After that, projection device 1 proceeds to the process in step S610.

[0133] Subsequently, projection device 1 determines whether or not to adjust the RGB values ​​of the light from the light source 11 after aging (step S610). If projection device 1 determines that it does not need to adjust the RGB values ​​of the light from the light source 11 after aging (NO in step S610), it finishes adjusting the chromaticity, etc., of the light from the light source 11 after aging. If it determines that it needs to adjust the RGB values ​​of the light from the light source 11 after aging (YES in step S610), it performs the RGB adjustment (step S611). The RGB adjustment is performed by adjusting the RGB gain of the image, the RGB offset of the image, and the RGB output of the light source 11. In this case, the RGB adjustment may be performed by referring to the detection results from the light sensor 10, the measured values ​​of the light projected onto the projection medium, and the color and brightness settings input by the user using means such as OSD menus and communication commands. Subsequently, projection device 1 finishes adjusting the chromaticity, etc., of the light from the light source 11 after aging.

[0134] As described above, the projection device 1 according to this embodiment compares the measurement results of the chromaticity of the light emitted from the light source 11 before and after aging degradation, and adjusts the current supplied to each of the multiple laser diodes individually based on the comparison results, so that the chromaticity of the light emitted from the light source 11 after aging degradation becomes close to the chromaticity before aging degradation. Here, in order to prevent the temperature of the off-light laser diodes, which are not the target of measurement, from becoming too low compared to the temperature during image projection (normal operation) while the chromaticity of the lit laser diodes, which are the target of measurement, is being measured, the projection device 1 temporarily supplies a current with a higher current value than that during image projection to specific laser diodes outside the measurement period. As a result, the projection device 1 can accurately measure and adjust the chromaticity of the light emitted from the light source 11 under temperature conditions close to (ideally the same as) those during image projection.

[0135] The timing at which the operating mode is set to chromaticity measurement mode can be arbitrary, but it is preferable to set it at the timing when the power is turned off after the projection device 1 has been operating in image projection mode. This allows the projection device 1 to measure the chromaticity from the laser diodes LD1 to LD3, which are at a stable temperature due to operating in image projection mode. Furthermore, this makes it easier for the projection device 1 to switch the image display pattern output as image data from the image processing unit 30 to a fixed pattern of all white where reflected light is suppressed.

[0136] Furthermore, although this embodiment describes the case where the light source 11 is composed of three laser diodes LD1 to LD3, it is not limited to this. The light source 11 may be composed of any number of laser diodes, two or more. In any case, one of the laser diodes included in the light source 11 is used as the reference laser diode. Also, in this embodiment, as in embodiments 1 and 2, multiple laser diodes having a common wavelength may be driven together to measure the amount of light.

[0137] Furthermore, in this embodiment, the case where the current value supplied to each laser diode LD1 to LD3 is constant when the operating mode is image projection mode has been described as an example, but the invention is not limited to this. Even when the operating mode is image projection mode, current may be supplied to each laser diode LD1 to LD3 by the same current control as when the operating mode is chromaticity measurement mode. As a result, the projection device 1 can drive each laser diode LD1 to LD3 by a common current control regardless of the operating mode. In this case, it is preferable to set the predetermined period T to 14ms or less in order to suppress image flicker.

[0138] Furthermore, in this embodiment, the current values ​​supplied to each laser diode LD1 to LD3 are described as constant during the second period of a predetermined period T, but the embodiment is not limited to this, and the current values ​​do not have to be constant. However, it is preferable for the current values ​​to be constant in order to suppress image flicker.

[0139] Furthermore, although this embodiment describes the case where the measurements of chromaticity C12 and C13, and chromaticity C12_ini and C13_ini are performed consecutively without intervals, it is not limited to this. The measurements of chromaticity C12 and C13, and chromaticity C12_ini and C13_ini may be performed sequentially with intervals in between. This allows the projection device 1 to perform processing by the light sensor 10 and the light source light intensity calculation block 32, communication between the light sensor 10 and the light source light intensity calculation block 32, and saving the measurement results to the light intensity storage unit 35 during periods when chromaticity measurements are not being performed.

[0140] This disclosure is not limited to the embodiments described above, and may be modified as appropriate without departing from its spirit.

[0141] Furthermore, this disclosure can be realized by having a CPU (Central Processing Unit) execute a computer program to perform some or all of the control processing in the projection device 1.

[0142] The program described above includes, when loaded into a computer, a set of instructions (or software code) for causing the computer to perform one or more of the functions described in the embodiments. The program may be stored in a non-temporary computer-readable medium or a physical storage medium. Examples, but not limited to, include RAM (Random-Access Memory), ROM (Read-Only Memory), flash memory, SSD (Solid-State Drive), or other memory technologies, CD-ROM, DVD (Digital Versatile Disc), Blu-ray® disc, or other optical disc storage, magnetic cassette, magnetic tape, magnetic disk storage, or other magnetic storage devices. The program may be transmitted over a temporary computer-readable medium or a communication medium. Examples, but not limited to, include temporary computer-readable medium or a communication medium that includes electrically, optically, acoustically, or otherwise propagating signals. [Explanation of Symbols]

[0143] 1 Projection device 2 Light source section 3 Illumination optics section 10 Light Sensors 11 Light source 12 Reflective polarizer 13 Reflective optical modulation element 14 Projection optical system 15 Projection medium 20~23 light 30 Video Processing Section 31 Display element drive unit 32 Light source intensity calculation block 33 Light source drive control unit 34 Light source drive unit 35 Light intensity memory unit 110 Mirror 111 Fly-eye lenses 112 Fly-eye lenses 113 Polarization conversion element 114 lenses 115 Optical separator 116 Mirror 117 Lens 118 Reflective polarizing plate 119 Reflective optical modulation element 120 Photosynthesis Prism 121 Mirror 122 Color component separator 123 Lens 124 Reflective polarizing plate 125 Reflective optical modulation element 126 lenses 127 Reflective polarizing plate 128 Reflective optical modulation element 129 Projection optical system 500 light sources 600 Phosphor Wheel LD1~LD3 Laser Diodes

Claims

1. A drive circuit that individually drives each of the multiple semiconductor lasers contained in the light source, A light sensor that detects light emitted from the aforementioned light source, A processing circuit that calculates at least the amount of light from each of the plurality of semiconductor lasers based on the detection results from the optical sensor, Equipped with, The aforementioned drive circuit is When the operating mode is image projection mode, a current of the first current value is supplied to each of the plurality of semiconductor lasers. When the operating mode is light intensity measurement mode, processing for a predetermined period consisting of a first period and a second period is performed periodically. In the processing for the predetermined period, during the first period, the plurality of semiconductor lasers are sequentially selected for groups of one or more semiconductor lasers having a common wavelength, the supply of current to the selected group of semiconductor lasers is stopped, and a current of the first current value is supplied to the remaining unselected semiconductor lasers, and during the second period, a current of a second current value higher than the first current value is supplied to each of the plurality of semiconductor lasers. The calculation processing circuit calculates the light intensity of each group of the plurality of semiconductor lasers based on the detection results from the optical sensor during the first period of each predetermined period. Light intensity measuring device.

2. When the operating mode is the light intensity measurement mode, the drive circuit sets the second current value such that the average current value supplied to each of the semiconductor lasers during the predetermined period is substantially the same as the first current value. The light intensity measuring device according to claim 1.

3. The aforementioned light source, A reflective optical modulation element that modulates and reflects the light emitted from the aforementioned light source based on video data, A projection optical unit that emits light modulated by the aforementioned optical modulation element, A light intensity measuring device according to claim 1, wherein the light sensor is provided between the light source and the light modulation element, A projection device equipped with [a specific feature / equipment].

4. A drive circuit that individually drives each of the multiple semiconductor lasers contained in the light source, A light sensor that detects light emitted from the aforementioned light source, A processing circuit that calculates at least the amount of light from each of the plurality of semiconductor lasers based on the detection results from the optical sensor, A method for measuring light intensity using a light intensity measuring device equipped with, When the operating mode is image projection mode, a current of the first current value is supplied to each of the plurality of semiconductor lasers. When the operating mode is light intensity measurement mode, processing for a predetermined period consisting of a first period and a second period is performed periodically. In the processing for the predetermined period, during the first period, the plurality of semiconductor lasers are sequentially selected for groups of one or more semiconductor lasers having a common wavelength, the supply of current to the selected group of semiconductor lasers is stopped, and a current of the first current value is supplied to the remaining unselected semiconductor lasers, and during the second period, a current of a second current value higher than the first current value is supplied to each of the plurality of semiconductor lasers. Based on the detection results by the optical sensor during the first period of each predetermined period, the amount of light from each group of the plurality of semiconductor lasers is calculated. Method for measuring light intensity.

5. A drive circuit that individually drives each of the multiple semiconductor lasers contained in the light source, A light sensor that detects light emitted from the aforementioned light source, A processing circuit that calculates at least the amount of light from each of the plurality of semiconductor lasers based on the detection results from the optical sensor, A control program that causes a computer to perform light intensity measurement processing in a light intensity measuring device equipped with the following: When the operating mode is image projection mode, the process involves supplying a current of a first current value to each of the plurality of semiconductor lasers, When the operating mode is light intensity measurement mode, the process periodically executes a predetermined period consisting of a first period and a second period, In the processing for the predetermined period, in the first period, the plurality of semiconductor lasers are sequentially selected for groups of one or more semiconductor lasers having a common wavelength, the supply of current to the selected group of semiconductor lasers is stopped, and a current of the first current value is supplied to the remaining unselected semiconductor lasers, and in the second period, a current of a second current value higher than the first current value is supplied to each of the plurality of semiconductor lasers. A process to calculate the light intensity of each group of the plurality of semiconductor lasers based on the detection results by the optical sensor during the first period of each predetermined period, A control program that causes a computer to execute a command.

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