JP2018061149A - Image projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image projection device that can perform color correction with a low-cost and simple configuration.SOLUTION: An image projection device (100) comprises: a light source (1) that emits excitation light in a first wavelength band; a wavelength conversion element (6) that converts the excitation light into converted light in a second wavelength band longer than the first wavelength band; light modulation elements (28, 29, and 39) that modulate the excitation light and converted light; an optical sensor (13) that acquires the light intensity of at least one of the first wavelength band and second wavelength band; and a control part (40) that performs color correction by adjusting the light in the first wavelength band or the second wavelength band. The control part performs color correction to reduce a change in color according to a change in light intensity.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image projection apparatus that projects light from an image display element.

  Conventionally, an image projection apparatus including a phosphor is known. In such an image projection apparatus, the phosphor functions as a wavelength conversion element that converts part of the light emitted from the light source into light longer than the wavelength of the light. However, since the color changes due to the characteristics and deterioration of the phosphor, it is necessary to perform color correction according to the characteristics and deterioration of the phosphor.

  In Patent Document 1, in order to adjust the color balance, the second light amount is controlled to be constant based on the first light amount and the second light amount from the light amount monitor, and the modulation amount of the first light amount by the light modulation device is controlled. A projector including a control unit that performs the above-described control is disclosed. Patent Document 2 discloses a display device that measures light intensity using three color sensors, regarding a display device that includes three light sources.

Japanese Patent No. 5593703 Japanese Patent No. 5743242

  However, in the projector disclosed in Patent Document 1, the light intensity relating to light in different wavelength bands is measured twice, or the light intensity is individually measured for each wavelength band using two or more optical sensors to obtain a color. It is necessary to convert. Further, the display device of Patent Document 2 requires three color sensors. As described above, in the configuration of Patent Document 1 or Patent Document 2, a plurality of measurement times are required or a plurality of optical sensors are required, so that the configuration is complicated or the cost is increased.

  SUMMARY An advantage of some aspects of the invention is that it provides an image projection apparatus capable of performing color correction with a low-cost and simple configuration.

  An image projection apparatus according to another aspect of the present invention includes a light source that emits excitation light in a first wavelength band, and a wavelength that converts the excitation light into converted light in a second wavelength band that is longer than the first wavelength band. A conversion element; a light modulation element that modulates the excitation light and the converted light; an optical sensor that obtains light intensity of at least one of the first wavelength band or the second wavelength band; and the first wavelength band or the A control unit that adjusts light in the second wavelength band to perform color correction, and the control unit performs the color correction so as to reduce a change in color according to a change in the light intensity.

  Other objects and features of the present invention are illustrated in the following examples.

  ADVANTAGE OF THE INVENTION According to this invention, the image projection apparatus which can perform color correction with a low-cost and simple structure can be provided.

1 is a configuration diagram of an image projection apparatus in Embodiment 1. FIG. In Example 1, it is a related figure of the electric current value of a laser light source, and the brightness acquired by the optical sensor. In Example 1, it is a relationship figure between the electric current value of a laser light source, and the brightness acquired from the illuminometer. In Example 1, it is a related figure of the electric current value of a laser light source, and a brightness ratio. In Example 1, it is a relationship figure of the gain of a reflection type liquid crystal display element, and a brightness ratio. FIG. 6 is a configuration diagram of an image projection apparatus in Embodiment 2.

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

  First, the configuration of an image projection apparatus (projector) in Embodiment 1 of the present invention will be described with reference to FIG. FIG. 1 is a configuration diagram of the image projection apparatus 100.

  The image projection device 100 includes a light source unit 50 (light source device). The light source unit 50 is a unit that can store a light source. In this embodiment, the light source unit 50 includes a laser light source 1, a collimator lens 2, a dichroic mirror (or half mirror) 3, condenser lenses 4 and 5, and a phosphor 6. Have.

  The laser light source 1 (light source such as an excitation light source) is a laser diode that emits excitation light (blue band light or ultraviolet band light) in a first wavelength band. A light beam (excitation light) emitted from the laser light source 1 is a divergent light beam, and is converted into a parallel light beam by the collimator lens 2 disposed immediately after the laser light source 1. The laser beam emitted from the collimator lens 2 is reflected by the dichroic mirror 3 and travels toward the condenser lenses 4 and 5. The dichroic mirror 3 has a minimum necessary size for reflecting the light beam from the collimator lens 2. The surface of the dichroic mirror 3 is coated with a dielectric multilayer film that reflects the wavelength light emitted from the laser light source 1 (the light having the wavelength of the laser light source 1) but transmits the fluorescent light (converted light) wavelength. Has been.

  The light beam reflected by the dichroic mirror 3 enters the condenser lenses 4 and 5. In FIG. 1, the condenser lens unit is composed of two lenses (condenser lenses 4 and 5) having positive power, but is not limited to this. The condenser lens unit may be composed of one lens or three or more lenses. The condenser lenses 4 and 5 collect and superimpose the divided light beams to form a laser beam spot uniformly on the phosphor (phosphor unit) 6.

  The phosphor 6 converts blue band light (or ultraviolet band light) emitted from the laser light source 1 into green band light and red band light (performs fluorescence conversion) and also converts light (green band light and red band light). Is superimposed on the return light (blue band light) and reflected to generate white light. Thus, the phosphor 6 is a wavelength conversion element that converts the excitation light into converted light in the second wavelength band that is longer than the first wavelength band. In this embodiment, the light source unit 50 that converts the wavelength of light from the laser light source 1 with the phosphor 6 is used. However, the present invention is not limited to this, and other light sources such as a light source unit including a white light source are used. May be used.

  The image projection apparatus 100 has an illumination optical system 60. The illumination optical system 60 illuminates reflective liquid crystal display elements 28, 29, and 30 (light modulation elements), which will be described later, using the light flux from the light source unit 50. The illumination optical system 60 includes a collimator lens 7, fly-eye lenses 8 and 9, a PS conversion element (polarization conversion element) 10, a condenser lens 11, a mirror 12, an optical sensor 13, and a lens 14.

  The light beam from the light source unit 50 is guided to the fly-eye lenses 8 and 9 through the collimator lens 7 and enters the PS conversion element 10. The PS conversion element 10 is configured to align the polarization direction of the incident light beam in a predetermined direction (to adjust to P-polarized light). The light beam from the PS conversion element 10 is reflected by the mirror 12 via the condenser lens 11. The optical sensor 13 is disposed in the vicinity of the mirror 12 (on the incident side of the light modulation element), and receives optical information (light intensity or brightness) related to the light flux from the light source unit 50 by receiving leakage light from the mirror 12. To get. The light beam reflected by the mirror 12 is guided to the color separation / synthesis unit 70 via the lens 14.

  The color separation / synthesis unit 70 includes a dichroic mirror 21, polarizing beam splitters 22 and 23, a color selective wavelength plate 24, phase plates 25, 26 and 27, reflective liquid crystal display elements 28, 29 and 30, and a color synthesis prism 31. Have The dichroic mirror 21 transmits green band light and reflects blue band light and red band light. The green band light that has passed through the dichroic mirror 21 enters the polarization beam splitter 22, passes through the phase plate 27, and enters the reflective liquid crystal display element 30 (third light modulation element). On the other hand, the color selective wave plate 24 converts the polarization direction of the blue band light of the blue band light and the red band light reflected by the dichroic mirror 21 by 90 ° into S polarization, and the red band light remains P polarization. In this state, the light is incident on the polarization beam splitter 23. The red band light that is P-polarized light is transmitted through the polarization beam splitter 23, and the blue band light that is S-polarized light is reflected by the polarization beam splitter 23. Thereby, the light incident on the polarization beam splitter 23 is separated into blue band light and red band light whose polarization directions are orthogonal to each other. The blue band light reflected from the polarization beam splitter 23 passes through the phase plate 25 and enters the reflective liquid crystal display element 28 (first light modulation element). The red band light that has passed through the polarization beam splitter 23 passes through the phase plate 26 and enters the reflective liquid crystal display element 29 (second light modulation element).

  Each of the reflective liquid crystal display elements 28, 29, and 30 modulates incident light (light from the light source unit 50) according to an image signal (driving signal) and reflects the light, thereby forming image light (image). Display element). The green band light reflected after being subjected to 180 ° phase difference modulation by the reflective liquid crystal display element 30 passes through the phase plate 27, becomes S-polarized light, reflects off the polarization beam splitter 22, and enters the color synthesis prism 31. The red band light reflected after being subjected to 180 ° phase difference modulation by the reflective liquid crystal display element 29 is transmitted through the phase plate 26, becomes S-polarized light, reflects off the polarization beam splitter 23, and enters the color synthesis prism 31. The blue band light reflected after being subjected to 180 ° phase difference modulation by the reflective liquid crystal display element 28 is transmitted through the phase plate 25, converted to P-polarized light, transmitted through the polarization beam splitter 23, and incident on the color combining prism 31. The color synthesizing prism 31 synthesizes light in all wavelength bands of red (R), green (G), and blue (B) and outputs the combined light to the projection optical system (projection lens) 80. The projection optical system 80 projects the combined light (projection light) from the color combining prism 31 onto a projection surface such as a screen (not shown). In this embodiment, the portion of the color separation / synthesis unit 70 excluding the reflective liquid crystal display elements 28, 29, and 30 is referred to as a color separation / synthesis system.

  The controller 40 performs color correction (color control) by adjusting light in the first wavelength band or the second wavelength band (that is, at least one of the reflective liquid crystal display elements 28, 29, and 30 so as to perform color correction). Control one). In the present embodiment, the control unit 40 performs color correction according to the light intensity (light quantity) acquired by the optical sensor 13 (that is, so as to reduce the change in color according to the change in light intensity). The storage unit 42 is a memory that stores various data used in the control by the control unit 40.

  Next, a change in color regarding light emitted from the image projection apparatus 100 (light source unit 50) will be described. The phosphor 6 generally has a characteristic of luminance saturation. This is a characteristic that the conversion efficiency decreases as the light intensity incident on the phosphor 6 increases. For example, when green band light and red band light are fluorescently emitted with respect to blue band light (blue excitation light), if the blue excitation light is increased, the conversion efficiency of green and red with respect to the blue light intensity is increased. Decreases and the bluishness becomes stronger. When the light intensity is changed by intentionally dimming the excitation light of the laser light source 1, the light intensity to the phosphor 6 changes and the color of the light source unit 50 changes. In addition, the excitation light deteriorates when used for a long time, and the light intensity of the excitation light decreases. When the light intensity of the excitation light decreases, the light intensity irradiated on the phosphor 6 decreases, but the phosphor 6 has a characteristic of luminance saturation, and emits fluorescence according to the light intensity irradiated on the phosphor 6. Efficiency and color change. Accordingly, when the light intensity of the excitation light is lowered due to long-term use, the color of the light source unit 50 including the phosphor 6 changes. Further, the excitation light is not only changed in excitation light intensity due to long-time use, but also when the light intensity is changed by intentionally dimming the excitation light, the light intensity to the phosphor 6 changes and the light source is saturated due to luminance saturation. The color of the part 50 changes. The phosphor 6 has a characteristic of temperature quenching accompanying a temperature change. The color of the light source unit 50 also changes depending on such characteristics. Since the color change due to the phosphor 6 occurs due to various factors as described above, in this embodiment, the color of the light source unit 50 is corrected (color correction is performed) using the optical sensor 13.

  Next, color correction (color correction) in the present embodiment will be described with reference to FIGS. FIG. 2 is a relationship diagram between the current value of the laser light source 1 and the amount of light acquired by the optical sensor 13, that is, the brightness (light information). The horizontal axis represents the current value of the laser light source 1, and the vertical axis represents the optical sensor 13. The brightness acquired by each is shown. First, when the brightness acquired by the optical sensor 13 is changed by changing the current value of the laser light source 1, a graph as shown in FIG. 2 is obtained.

  In this embodiment, the optical sensor 13 has at least one light intensity (light quantity, brightness) of the first wavelength band (blue band light or ultraviolet band light) or the second wavelength band (green band light and red band light). get. That is, the optical sensor 13 may be configured to acquire either the light intensity of the excitation light or the light intensity of the converted light. Preferably, the optical sensor 13 acquires only the light intensity of the green band light.

  Subsequently, an illuminometer (not shown) is disposed at the projection position of the projection light from the image projection apparatus 100 (outside of the image projection apparatus 100). Here, the reflective liquid crystal display elements 28, 29, and 30 in the blue, red, and green light paths are alternately displayed with the maximum gradation, and the current value of the laser light source 1 is changed to change the brightness step by step. Then, the brightness (Ev value) in each optical path is acquired using an illuminometer. When displaying the maximum gradation of the reflective liquid crystal display element 28 in the blue light path, the red and green reflective liquid crystal display elements 29 and 30 are displayed in black. In addition, when the brightness at the time of displaying the maximum gradation of green is obtained from the illuminance meter, the blue and red reflective liquid crystal display elements 28 and 29 are displayed in black. Further, when the brightness at the time of displaying the maximum gray level of red is obtained from the illuminance meter, the blue and green reflective liquid crystal display elements 28 and 30 are displayed in black. As described above, when the brightness of each optical path with respect to the current value of the laser light source 1 is obtained using the illuminometer, a graph as shown in FIG. 3 is obtained. FIG. 3 is a relationship diagram between the current value of the laser light source 1 and the brightness acquired from the illuminometer, where the horizontal axis indicates the current value of the laser light source 1 and the vertical axis indicates the brightness acquired from the illuminometer. Yes.

  Subsequently, as shown in FIG. 4, the numerical values of FIG. 3 are calculated so that the degree of color can be understood. FIG. 4 shows the current value of the laser light source 1, the brightness ratio (red / blue) between the red light path and the blue light path acquired from the illuminometer, and the brightness between the green light path and the blue light path acquired from the illuminometer. It is a relationship diagram with a ratio (green / blue). In FIG. 4, the horizontal axis represents the current value of the laser light source 1, and the vertical axis represents the brightness ratio (red / blue, green / blue). As shown in FIG. 4, the brightness ratio (red / blue, green / blue) decreases as the current value of the laser light source 1 increases. This is because, due to the luminance saturation characteristic of the phosphor 6, as the light intensity incident on the phosphor 6 increases, the ratio of converting the blue band light to the green band light and the red band light decreases, and the color becomes blue. It shows that the color will be close.

  In order to reduce such a change in color, the control unit 40 uses the first wavelength band or the second wavelength band from the reflective liquid crystal display element based on the light intensity (brightness) acquired by the optical sensor 13. Color correction is performed by controlling the light output. Preferably, the control unit 40 performs color correction based on light intensity and color information of projection light (color information acquired by an illuminometer). Preferably, the storage unit 42 stores data indicating the relationship between the light intensity and the color information, and the control unit 40 performs color correction based on the data.

  In this embodiment, the control unit 40 performs gain correction (gamma correction) on at least one (gamma characteristic) of the reflective liquid crystal display elements 28, 29, and 30 as color correction. When the color of the phosphor 6 changes, for example, the gain of the red and green reflective liquid crystal display elements 29 and 30 is changed to adjust the color. That is, in this embodiment, the light modulation elements are reflective liquid crystal display elements 28, 29, and 30 (first light modulation element and second light modulation element) that modulate blue band light, red band light, and green band light, respectively. , And a third light modulation element). At this time, the control unit 40 performs gain correction by reducing the gain of the reflective liquid crystal display elements 29 and 30 (second light modulation element and third light modulation element). Alternatively, the control unit 40 performs gain correction by increasing the gain of the reflective liquid crystal display element 28 (first light modulation element). Alternatively, the control unit 40 may perform gain correction by reducing the gain of the reflective liquid crystal display elements 29 and 30 and increasing the gain of the reflective liquid crystal display element 28.

  FIG. 5 is a relationship diagram between the gains of the red and green reflective liquid crystal display elements 29 and 30 and the brightness ratio (red / blue, green / blue). In FIG. 5, the horizontal axis represents the gains of the red and green reflective liquid crystal display elements 29 and 30, and the vertical axis represents the brightness ratio. For example, when the current value of the laser light source 1 is changed from A to B as shown in FIG. 4, the brightness ratio, that is, the color changes. Here, the gains of the red and green reflective liquid crystal display elements 29 and 30 are changed from A ′ to B ′ as shown in FIG. 5 so as to correct the changed brightness ratio (color tone) of the same amount. To do. Thereby, the color of the current value B of the laser light source 1 shown in FIG. 4 can be returned to the color of the current value A. As a result, even when the current value of the laser light source 1 is changed, the brightness ratio of green and blue and red and blue (green / blue, red / blue), that is, the color can be kept substantially constant.

  Further, when the laser light source 1 is used for a long time, the brightness of the laser light source 1 is lowered. For example, let us consider a case where the brightness corresponding to the current value A of the laser light source 1 in FIG. 2 is the same current value A but decreases to the brightness corresponding to the current value B due to deterioration due to long-term use. At this time, due to the luminance saturation characteristic of the phosphor 6, the respective brightness ratios of green and blue and red and blue also correspond to the current values A and B of the laser light source 1 in FIG. 4. become. At this time, the brightness (light quantity) acquired using the optical sensor 13 decreases from the current value A to the brightness corresponding to the current value B. Therefore, in this embodiment, when the gains of the red and green reflective liquid crystal display elements 29 and 30 in FIG. 5 are changed, the red and blue brightness ratios and the green and blue brightness ratios cause the deterioration. Correct the changed amount of the same color (perform color correction). That is, the control unit 40 changes the gain of each of the red and green reflective liquid crystal display elements 29 and 30 from A ′ to B ′ (by performing gain correction), and changes the deteriorated color of the laser light source 1 to the initial value. Return to color. Thereby, even when the brightness of the laser light source 1 changes due to deterioration, the color can be kept constant.

  In the present embodiment, the color change of the image projection apparatus 100 (light source unit 50) with respect to the change in light intensity is acquired in advance using the optical sensor 13 at an initial stage such as at the time of factory shipment. Thereby, when the light quantity of the laser light source 1 (light source part 50) is changed intentionally or when the laser light source 1 deteriorates and the light quantity from the light source part 50 changes, the light intensity is acquired by the optical sensor 13. The color change (that is, the control amount of the color) can be estimated only by this. The control unit 40 can return the changed color to the original color by controlling the reflective liquid crystal display element so as to perform color correction according to the estimated color change.

  Next, with reference to FIG. 6, an image projection apparatus in Embodiment 2 of the present invention will be described. FIG. 6 is a configuration diagram of the image projection apparatus 100a. In the image projection apparatus 100a, the optical sensor 13 is arranged in the vicinity of the mirror 12 (incident side of the light modulation element) in that the optical sensor 13 is arranged in the vicinity of the color synthesizing prism 31 (exit side of the light modulation element). This is different from the image projection apparatus 100 of the first embodiment. Since the other structure of the image projection apparatus 100a is the same as that of the image projection apparatus 100, those description is abbreviate | omitted.

  In FIG. 6, the solid line indicates the light beam displayed by the reflective liquid crystal display elements 28, 29, and 30, and the dotted line indicates the leaked light from the color synthesis prism 31. The optical sensor 13 disposed in the vicinity of the color synthesis prism 31 acquires leakage light indicated by a dotted line. Even in the configuration in which the optical sensor 13 is disposed on the light emission side of the light modulation element as in the present embodiment, the same effects as in the configuration of the first embodiment can be obtained.

  In each embodiment, the light modulation element is not limited to the reflective liquid crystal display element, but may be a transmissive liquid crystal display element or another light modulation element such as a DMD.

  As described above, in each embodiment, when color correction is performed when the light source unit is deteriorated, the color control amount can be estimated simply by obtaining the brightness using the optical sensor. When correcting, it is possible to perform appropriate color control (color correction) using a reflective liquid crystal display element. Further, in this embodiment, the image projection apparatus may be provided with one optical sensor, and color correction can be performed by estimating the color by simply measuring the light intensity using one optical sensor. Therefore, according to each embodiment, it is possible to provide an image projection apparatus capable of performing color correction with a low cost and simple configuration.

  The color correction in each of the above-described embodiments refers to control for displaying an image according to the image data input to the image projection apparatus (projector) on the screen. Alternatively, even if control is performed, the control for setting the RGB gradation or brightness included in the image data input to the projector to 50 to 200% of the input state is called color correction.

  In addition, each color band in each of the above-described embodiments is, for example, the following wavelength band. Specifically, the blue band is 400 to 510 nm, the green band is 490 to 600 nm, the red band is 580 to 700 nm, and the ultraviolet band is 280 to 400 nm.

  As mentioned above, although the preferable Example of this invention was described, this invention is not limited to these Examples, A various deformation | transformation and change are possible within the range of the summary.

1 Laser light source
6 Phosphor (wavelength conversion element)
13 Optical sensor 28, 29, 30 Reflective liquid crystal display element (light modulation element)
40 Control unit 100, 100a Image projection device

Claims (14)

A light source that emits excitation light in a first wavelength band;
A wavelength conversion element that converts the excitation light into converted light in a second wavelength band longer than the first wavelength band;
A light modulation element for modulating the excitation light and the converted light;
An optical sensor for acquiring the light intensity of at least one of the first wavelength band or the second wavelength band;
A controller that performs color correction by adjusting light in the first wavelength band or the second wavelength band;
The control unit performs the color correction so as to reduce a change in color according to a change in the light intensity. The excitation light in the first wavelength band is blue band light or ultraviolet band light,
The image projection apparatus according to claim 1, wherein the converted light in the second wavelength band is green band light and red band light.   The image projection apparatus according to claim 2, wherein the optical sensor acquires only the light intensity of the green band light.   The said control part performs the said color correction by controlling the optical output of the said 1st wavelength band or the said 2nd wavelength band from the said light modulation element, The any one of Claim 1 thru | or 3 characterized by the above-mentioned. The image projection apparatus described in 1.   5. The image projection apparatus according to claim 1, wherein the control unit performs the color correction related to the light modulation element based on the light intensity and color information of the projection light. . A storage unit that stores data indicating a relationship between the light intensity and the color information;
The image projection apparatus according to claim 5, wherein the control unit performs the color correction related to the light modulation element based on the data.   The image projection apparatus according to claim 1, wherein the control unit performs gamma correction on the light modulation element as the color correction.   The image projection apparatus according to claim 1, wherein the control unit performs gain correction on the light modulation element as the color correction. The light modulation element is
A first light modulation element for modulating blue band light;
A second light modulation element for modulating red band light;
The image projection apparatus according to claim 8, further comprising a third light modulation element that modulates green band light.   The image projection apparatus according to claim 9, wherein the control unit performs the gain correction by reducing gains of the second light modulation element and the third light modulation element.   The image projection device according to claim 9, wherein the control unit performs the gain correction by increasing a gain of the first light modulation element.   The image projection apparatus according to claim 1, wherein the optical sensor is arranged on an incident side of the light modulation element.   The image projection apparatus according to claim 1, wherein the optical sensor is disposed on an emission side of the light modulation element.   The image projection apparatus according to claim 1, wherein the light modulation element is a liquid crystal display element or a DMD.