Image projection device

Abstract

To permit adjustment of a focal position according to a change in the focal position.SOLUTION: An image projection device includes: an image light generation section 2 for generating image light by receiving light emitted from a light source; and a projection optical system 3 for projecting image light generated by the image generation section 2 to a projection surface P. Image light projected from the projection optical system 3 to the projection surface P includes first image light having predetermined light energy, and second image light having light energy larger than that of the first image light, and a focal position (b) when the first image light is projected and a focal position (a) when the second image light is projected are disposed so as to sandwich at least one portion of the projection surface P.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an image projection device.

Background Art

[0002] There is known an image projection device that condenses light emitted from a light source onto an image modulation element such as a DMD (Digital Micromirror Device), and projects the image light modulated by the image modulation element onto a projection surface such as a screen.

[0003] In an image projection device, when the temperature inside the device rises during operation, the optical characteristics of the projection optical system change, resulting in a change in the focal position of the image light projected onto the projection surface and a problem of deterioration in image quality.

[0004] Regarding such a problem, for example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2006-313201), a method of adjusting the focal position using chromatic aberration of image light or distortion aberration of a projected image has been proposed. According to this method, using image light of a specific wavelength (color) or a specific part of the projected image, the initial focal position is shifted in a direction opposite to the direction in which a positional change occurs in advance, so that even if a change in the focal position due to a temperature rise occurs, the displacement is canceled out, thereby suppressing a deterioration in image quality.

[0005] However, in the method of adjusting the focal position using chromatic aberration or distortion aberration, the adjustment range of the focal position is limited within the range of chromatic aberration or distortion aberration. Therefore, when the displacement width of the focal position exceeds the range of chromatic aberration or distortion aberration, there is a problem that the adjustment of the focal position corresponding to the change in the focal position cannot be sufficiently performed.

Summary of the Invention

Problems to be Solved by the Invention

[0006] Therefore, an object of the present invention is to enable adjustment of the focal position in accordance with a change in the focal position.

Means for Solving the Problems

[0007] In order to solve the above problems, an image projection apparatus according to the present invention includes a light source, an image light generation unit that receives light emitted from the light source and generates image light, and a projection optical system that projects the image light generated by the image light generation unit onto a projection surface. The image light projected from the projection optical system onto the projection surface includes first image light having a predetermined light energy and second image light having a light energy greater than that of the first image light, and a focal position when the first image light is projected and a focal position when the second image light is projected are arranged so as to sandwich at least a part of the projection surface.

Effects of the Invention

[0008] According to the present invention, the focal position can be adjusted according to the change in the focal position.

Brief Description of the Drawings

[0009]

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Embodiments for Carrying Out the Invention

[0010] <Overall Configuration of the Image Projection Device> First, based on FIG. 1, the overall configuration of the image projection device 100 according to the first embodiment of the present invention will be described. In each drawing for explaining the present invention, components such as members and parts having the same function or shape are given the same reference numerals as much as possible for discrimination, and the description thereof will be omitted after being explained once.

[0011] As shown in FIG. 1, the image projection apparatus 100 according to the first embodiment of the present invention includes an illumination device 1, an image light generation unit 2, and a projection optical system 3. The illumination device 1 is a device that irradiates light onto the image light generation unit 2. The image light generation unit 2 is a part that receives the light irradiated from the illumination device 1 and generates image light. Specifically, the image light generation unit 2 has an image modulation element such as a DMD (Digital Micromirror Device) or a liquid crystal panel. When light is irradiated from the illumination device 1 onto the image light generation unit 2, the light is modulated by the image modulation element, and image light is generated. The projection optical system 3 is an optical system that projects the image light generated by the image light generation unit 2 onto a projection surface such as a screen.

[0012] The illumination device 1 is composed of a first light source unit 4, a second light source unit 5, a color wheel 6, a combining optical element 13, a light homogenizing element 7, and the like.

[0013] Each of the light source units 4 and 5 has a light source 8, a collimator lens 9, a condensing element 10, a dichroic mirror 11, and a wavelength conversion element 12.

[0014] As the light source 8, for example, an LD (Laser Diode) is used. A collimator lens 9 is disposed at a position facing the light source 8. The collimator lens 9 is a lens that converts the excitation light emitted from the light source 8 into a parallel light beam. The excitation light converted into parallel light by the collimator lens 9 is condensed by the condensing element 10. The condensing element 10 includes a first condensing element 10A disposed between the collimator lens 9 and the dichroic mirror 11, a second condensing element 10B disposed between the dichroic mirror 11 and the wavelength conversion element 12, and a third condensing element 10C disposed between the wavelength conversion element 12 and the color wheel 6 in the traveling direction of the light.

[0015] The dichroic mirror 11 is a wavelength-selective mirror that reflects only light of a specific wavelength and transmits light of other wavelengths.

[0016] As an example of the wavelength conversion element 12, a disk-shaped phosphor wheel can be mentioned. In the first embodiment of the present invention, a case where a blue laser light source is used as the light source 8 and a phosphor wheel is used as the wavelength conversion element 12 will be described as an example.

[0017] In each light source unit 4, 5, when light (blue light) is emitted from the light source 8, the light is condensed by the first condenser 10A, and the condensed light is guided to the dichroic mirror 11. Then, only light of a specific wavelength is reflected by the dichroic mirror 11, and the light is condensed by the second condenser 10B, thereby generating a predetermined condensing spot on the phosphor wheel which is the wavelength conversion element 12.

[0018] The phosphor wheel is a disk-shaped member configured to rotate at high speed by a drive motor. Further, the phosphor wheel has a phosphor region which is a wavelength conversion region coated with a phosphor and an excitation light reflection region which is a non-wavelength conversion region for reflecting excitation light. When the phosphor wheel rotates, the excitation light reflection region and the phosphor region are switched at the position of the condensing spot on the phosphor wheel.

[0019] When the excitation light reflection region of the phosphor wheel is located at the position of the condensing spot, the light is not wavelength-converted and blue light is output as it is. On the other hand, when the phosphor region of the phosphor wheel is located at the position of the condensing spot, the light is wavelength-converted into yellow or yellow-green fluorescence and output. Note that the phosphor wheel is not limited to being divided into two regions, an excitation light reflection region and a phosphor region, and may have a plurality of fluorescent regions (for example, a fluorescent region that emits yellow light, a fluorescent region that emits green light) that convert to different wavelengths from each other. Further, as the blue laser light source, a semiconductor blue laser light source having a peak wavelength between 440 [nm] and 465 [nm] in the oscillation wavelength is preferable.

[0020] The light beam reflected by the phosphor wheel (wavelength conversion element 12) passes through the second condenser 10B again and is then condensed by the third condenser 10C. Then, the condensed light passes through the color wheel 6 and enters the light homogenizing element 7. In this case, the light condensed by the third condenser 10C of the first light source unit 4 travels straight through the color wheel 6 and is guided to the light homogenizing element 7. On the other hand, the light condensed by the third condenser 10C of the second light source unit 5 is reflected by a mirror which is the combining optical element 13, and its path is changed in the same direction as the light of the first light source unit 4 and is guided to the color wheel 6 and the light homogenizing element 7. Note that as the combining optical element 13, a prism may be used in addition to a mirror.

[0021] The color wheel 6 rotates by a motor and allows the light from each of the light source units 4 and 5 to pass through, thereby splitting the light into red, blue, green, and yellow color component lights and outputting them to the light homogenizing element 7. Specifically, the color wheel 6 has a transparent portion that transmits blue component and yellow component lights, a red filter that extracts red component light from yellow fluorescence, and a green filter that extracts light by increasing the purity of the green component from green fluorescence. When the light guided through the combining optical element 13 passes through the rotating color wheel 6, the light is split into color components and output to the light homogenizing element 7.

[0022] As the light homogenizing element 7, for example, a light tunnel with a hollow interior and four mirrors combined on the inner surface, a rod integrator formed of a transparent material such as glass in the shape of a prism, a fly-eye lens, etc. are used. For example, when a light tunnel is used as the light homogenizing element 7, by making the aspect ratio of the light tunnel substantially the same as that of the image light generation unit 2 and making the shape of the exit of the light tunnel projected onto the surface of the image light generation unit 2, the surface of the image light generation unit 2 can be efficiently illuminated.

[0023] The light homogenized by the light homogenizing element 7 is irradiated onto the image light generation unit 2, and the image light is generated by modulating the light with the image light generation unit 2. Then, the image light generated by the image light generation unit 2 is enlarged by the projection optical system 3 and projected onto the projection surface.

[0024] Subsequently, the cooling mechanism of the image projection apparatus 100 according to the first embodiment of the present invention will be described.

[0025] As shown in FIG. 1, in the image projection apparatus 100 according to the first embodiment of the present invention, as a cooling mechanism for cooling the inside of the apparatus, a plurality of heat receiving members 14, a plurality of heat radiating members 15, and a plurality of air flow generating devices 16 are provided.

[0026] The plurality of heat receiving members 14 are arranged so as to be in contact with the light sources 8 and the wavelength conversion elements 12 of the respective light source units 4 and 5. In the first embodiment of the present invention, three heat receiving members 14 are provided on three side surfaces constituting the housing portion 20 of the illumination device 1.

[0027] The plurality of heat radiating members 15 are provided so as to be in contact with the respective heat receiving members 14 outside the housing portion 20 of the illumination device 1, and are also provided so as to be in contact with the outer surface of the housing portion 21 in which the image light generation unit 2 and the light homogenizing element 7 are housed. Each heat radiating member 15 is constituted by, for example, a heat sink having a plurality of fins. The shape of the fins may be any shape having at least a plurality of irregularities, and includes plate fins, pin fins, corrugated fins, and the like.

[0028] The plurality of air flow generating devices 16 are provided in the vicinity of the heat radiating member 15 and in the vicinity of the electronic substrate 17 inside the image projection apparatus 100. Each air flow generating device 16 is constituted by, for example, an axial flow fan or a sirocco fan. Further, a plurality of air supply ports 18 for supplying air into the apparatus and exhaust ports 19 for exhausting air are provided in the exterior portion 22 of the image projection apparatus 100 by driving the air flow generating devices 16.

[0029] Thus, in the image projection apparatus 100 according to the first embodiment of the present invention, since the plurality of heat receiving members 14 are arranged so as to be in contact with each light source 8 and each wavelength conversion element 12, the heat generated from each light source 8 and each wavelength conversion element 12 moves to the heat receiving members 14. Then, the heat that has moved to the heat receiving members 14 moves to each heat radiating member 15 that is in contact with each heat receiving member 14, and is radiated from each heat radiating member 15. Thereby, each light source 8 and each wavelength conversion element 12 can be cooled. Further, the airflow generated by the airflow generating device 16 enhances the heat radiation effect by the heat radiating member 15 and also cools the electronic substrate 17. In addition, the heat released from each heat radiating member 15 and the like is discharged from the exhaust port 19 to the outside of the apparatus by the airflow generated inside the apparatus, so that the temperature rise inside the image projection apparatus 100 can be suppressed.

[0030] <Hardware Configuration> Subsequently, based on FIG. 2, the hardware configuration of the image projection apparatus 100 according to the first embodiment of the present invention will be described.

[0031] As shown in FIG. 2, the image projection apparatus 100 includes a CPU (Central Processing Unit) 801, a ROM (Read Only Memory) 802, a RAM (Random Access Memory) 803, a media I / F (Interface) 807, an operation unit 808, a power switch 809, a bus line 810, a network I / F (Interface) 811, a light source drive circuit 814, a light source 8, an image light generation unit 2, a projection optical system 3, an external device connection I / F (Interface) 818, an airflow generation device drive circuit 819, and an airflow generation device 16.

[0032] Among these, the CPU 801 controls the operation of the entire image projection apparatus 100. The ROM 802 stores programs used for driving the CPU 801. The RAM 803 is used as a work area for the CPU 801. The media I / F 807 controls the reading or writing (storage) of data to / from a recording medium 806 such as a flash memory.

[0033] The operation unit 808 is provided with various keys, buttons, LEDs, etc., and is used for the user to perform various operations other than turning on and off the power of the image projection device 100. For example, the operation unit 808 receives instruction operations such as adjustment operations for the size of the projected image, adjustment operations for color tone, focus adjustment operations, keystone adjustment operations, etc., and outputs the received operation content to the CPU 801.

[0034] The power switch 809 is a switch for switching on and off the power of the image projection device 100.

[0035] The bus line 810 is an address bus, a data bus, etc. for electrically connecting each component such as the CPU 801. The network I / F 811 is an interface for performing data communication using a communication network such as the Internet. The external device connection I / F 818 is directly connected to a PC (Personal Computer), and acquires control signals and image data from the PC.

[0036] The light source drive circuit 814 controls the lighting and extinguishing of the light source 8 under the control of the CPU 801. When the light source 8 is lit under the control of the light source drive circuit 814, light is irradiated from the light source 8 to the image light generation unit 2. The image light generation unit 2 generates image light corresponding to each color based on the image data given via the external device connection I / F 818, etc. The image light of each color generated by the image light generation unit 2 is projected onto the projection surface via the projection optical system 3. Thus, the light source drive circuit 814, the light source 8, the image light generation unit 2, and the projection optical system 3 function as a projection unit (projection means) for projecting image light onto the projection surface based on the image data as a whole.

[0037] The airflow generation device drive circuit 819 is connected to the CPU 801 and the airflow generation device 16, and drives and stops driving the airflow generation device 16 based on a control signal from the CPU 801.

[0038] When power is supplied to the CPU 801, it starts up according to a control program pre-stored in the ROM 802, gives a control signal to the light source drive circuit 814 to turn on the light source 8, and gives a control signal to the air flow generator drive circuit 819 to drive the air flow generator 16. Also, when the supply of power from the power circuit to the image projection apparatus 100 is started, the image light generation unit 2 becomes in a state where an image can be displayed, and further, power is supplied from the power circuit to various other components.

[0039] Also, when the power switch 809 of the image projection apparatus 100 is turned off, a power-off signal is sent from the power switch 809 to the CPU 801. When the CPU 801 detects the power-off signal, it gives a control signal to the light source drive circuit 814 to turn off the light source 8. After that, when a predetermined time has elapsed, the CPU 801 gives a control signal to the air flow generator drive circuit 819 to stop driving the air flow generator 16, ends its own control process by itself, and finally gives an instruction to the power circuit to stop the supply of power.

[0040] <Change in focal position due to temperature rise> Subsequently, with reference to FIGS. 14 and 15, the change in the focal position due to temperature rise will be described.

[0041] FIG. 14 shows the state before the focal position changes, and FIG. 15 shows the state after the focal position has changed.

[0042] As shown in FIG. 14, when image light is emitted from the image modulation element 201 of the image light generation unit 202, the output image light passes through a plurality of lenses 213 constituting the projection optical system 203 and is enlarged, and is projected onto a projection surface P such as a screen. At this time, by adjusting the focal position a1 of the image light to coincide with the projection surface P, a good image is projected.

[0043] However, when heat is generated from a heat-generating member such as a light source as the image projection device operates, the temperature inside the device rises, and each member thermally expands, causing changes in the optical characteristics of the projection optical system 203 and the like. As a result, as shown in FIG. 15, the focal position a2 of the image light changes to the front side (the projection optical system 203 side) from the projection surface P, and the image quality of the image projected onto the projection surface P deteriorates. Note that depending on the mode of change in the optical characteristics, the focal position a2 of the image light may change to the back side (the side opposite to the projection optical system 203 side) from the projection surface P, contrary to the example shown in FIG. 15.

[0044] In addition, the change in the focal position associated with such a temperature rise tends to be more prominent when projecting image light with high light energy such as a bright image than when projecting image light with low light energy such as a dark image.

[0045] FIG. 16 shows the displacement amounts of the focal positions when two types of image lights A' and B' with different energy magnitudes are projected. In FIG. 16, the horizontal axis represents the elapsed time since the start of projection of the image light, and the vertical axis represents the displacement amount of the focus when the position of the projection surface is set to "0". In this case, the plus side of the vertical axis indicates displacement to the front side, and the minus side indicates displacement to the back side.

[0046] As shown in FIG. 16, when the image light B' with low energy is projected, the focal position changes slightly to the front side over time, but the displacement amount is small. Therefore, the focal position is within the allowable width H of the image quality. On the other hand, when the image light A' with high energy is projected, since the focal position changes greatly, the focal position may deviate from the allowable range H of the image quality, and there is a risk that the image quality will deteriorate significantly.

[0047] Therefore, in the present invention, in order to suppress the deterioration of the image quality due to the change in the focal position, the following method for adjusting the focal position is proposed. Hereinafter, the method for adjusting the focal position according to the present invention will be described by taking the configuration according to the first embodiment of the present invention as an example.

[0048] <Method for Adjusting Focal Position> FIG. 3 is a diagram showing a method for adjusting the focal position according to the first embodiment of the present invention.

[0049] In FIG. 3, the state in which the image light output from the image modulation element 25 of the image light generation unit 2 passes through the plurality of lenses 26 of the projection optical system 3 and is projected onto the projection surface P is shown. Here, the focal position a in FIG. 3 is the focal position when the image light A with high energy is projected, and the focal position b in the figure is the focal position when the image light B with low energy is projected.

[0050] In the present invention, the "image light A with high energy" means image light having higher light energy than the image light B. That is, the image light projected by the image projection device according to the present invention includes at least a first image light (image light B with low energy) having a predetermined light energy and a second image light (image light A with high energy) having higher light energy than the first image light. The image light A with high energy is, for example, image light having a higher average picture level (APL) than the image light B with low energy. Further, when the projected image light is monochromatic image light, it can be said that the image light A with high energy is image light having a higher area ratio of white image light than the image light B with low energy.

[0051] Here, the average picture luminance (APL) is calculated by computing the sum Ysum of the luminance values Y of each pixel and dividing the sum Ysum by the total number N of pixels, and can be calculated by the average picture luminance Yave = Ysum / N. Note that the method for calculating the average picture luminance (APL) is not particularly limited, and examples include a method of calculating from image information within the image projection device, a method of calculating with a PC or the like based on the image data input to the image projection device, and a method of measuring the luminance at various locations of the projected image light and taking the average. Also, the area ratio of the white image light means the ratio of the pixels controlled to be white among the total number of pixels of the pixel of the image light generation unit 2 when a monochrome image in which each pixel is either white or black is projected. In this case, white is defined as the state controlled by the image light generation unit 2 so that the largest amount of light enters the projection optical system, and black is defined as the state controlled by the image light generation unit 2 so that the smallest amount of light enters the projection optical system.

[0052] As shown in FIG. 3, in the first embodiment of the present invention, the focal position b when the image light B with low energy is projected and the focal position a when the image light A with high energy is projected are adjusted to be arranged on opposite sides sandwiching the projection surface P. In other words, the projection surface P is located between the focal position a when the image light A with high energy is projected and the focal position b when the image light B with low energy is projected, and the respective focal positions a and b are adjusted accordingly.

[0053] Also, in the first embodiment of the present invention, the respective focal positions a and b arranged to sandwich the projection surface P are set as the focal positions when the change in each focal position has reached a stable state after the projection of each image light A and B has started. Note that the "stable state" means a state in which the change (change rate) of the focal position per unit time is 1 / 10 or less of the change rate (focal movement distance ÷ 60 seconds) from immediately after the change from the projection of the first image light to the projection of the second image light to 1 minute later. Also, the state in which the change (change rate) of the temperature per unit time is 1 / 10 or less of the change rate (temperature change amount ÷ 60 seconds) from immediately after the change from the projection of the first image light to the projection of the second image light to 1 minute later may be defined as the "stable state".

[0054] Thus, in the first embodiment of the present invention, since each of the focal positions a and b arranged so as to sandwich the projection surface P is the focal position when the change in each focal position reaches a stable state, as shown in FIG. 4, each of the focal positions a and b in the stable state can be included within the allowable range H of image quality. That is, in the first embodiment of the present invention, compared with the comparative example shown by the two-dot chain line in FIG. 4, by shifting the focal position in advance to the side opposite to the focal displacement direction (the minus side of the Y axis), both of the focal positions a and b in the stable state can be included within the allowable range H of image quality. In the case of the comparative example, since each of the focal positions in the stable state at the time of projection of the respective image lights A' and B' is located on the plus side of the Y axis with respect to the position of the projection surface P, the focal position in the stable state when the image light A' with particularly large energy is projected is out of the allowable range H of image quality. On the contrary, in the first embodiment of the present invention, since the focal position b in the stable state when the image light B with small energy is projected and the focal position a in the stable state when the image light A with large energy is projected are arranged so as to sandwich the projection surface P, each of the focal positions a and b in the stable state can be included within the allowable range H of image quality. The shift amount d of the focal position may be appropriately set according to the deviation amount between the focal position in the stable state when the focal position is not shifted (the case of the comparative example) and the allowable range H of image quality, and the size of the allowable range H of image quality.

[0055] Generally, for some time after the projection of the image light is started, initial settings such as input switching operations by the user etc. are often performed. Therefore, it is preferable to prioritize the image quality after the focal position has shifted to the stable state rather than the image quality immediately after the projection starts. Therefore, in the first embodiment of the present invention, each of the focal positions a and b in the stable state is adjusted to be arranged so as to sandwich the projection surface P. Thereby, when the initial setting by the user etc. is completed and each of the focal positions a and b reaches the stable state, the image quality can be improved.

[0056] Also, in the first embodiment of the present invention, when adjusting the focal position, chromatic aberration of image light or distortion aberration of the projected image is not used, so the adjustment range is not limited to the range of chromatic aberration or distortion aberration. Therefore, it is possible to adjust the focal position according to the change in the focal position. Thus, according to the adjustment method according to the first embodiment of the present invention, even when the amount of deviation of the focal position exceeds the range of chromatic aberration or distortion aberration, it is possible to adjust the focal position according to the change in the focal position, and the image quality can be improved.

[0057] Also, the distances between the respective focal positions a, b and the projection surface P can be set as appropriate. For example, in FIG. 3, the distances La, Lb from the projection surface P to the respective focal positions a, b may be set to 1 / 2 (L / 2) of the distance L between the respective focal positions a, b. In this case, the image quality when the image light A with large energy is projected and the image quality when the image light B with small energy is projected can be made the same when the respective focal positions are in a stable state. Also, when it is desired to improve the image quality of the focal position a when the image light A with large energy is projected, it is preferable to make the distance La between the focal position a and the projection surface P smaller than L / 2. Conversely, when it is desired to improve the image quality at the focal position b when the image light B with small energy is projected, it is preferable to make the distance La between the focal position b and the projection surface P smaller than L / 2.

[0058] Thus, the distances La, Lb between the projection surface P and the respective focal positions a, b can be changed as appropriate. However, if the distances La, Lb between the projection surface P and the respective focal positions a, b become too large, there is a concern that the deterioration of the image quality at the focal position with a large distance becomes prominent. Therefore, it is preferable that the distances La, Lb between the projection surface P and the respective focal positions a, b are set within a range of 1 / 3 or more and 2 / 3 or less of the distance L between the focal positions a, b (L / 3 ≤ La, Lb ≤ 2L / 3).

[0059] Subsequently, another embodiment of the present invention will be described. Hereinafter, mainly the parts different from the first embodiment of the present invention will be described, and the same parts will be omitted as appropriate.

[0060] <Second Embodiment of the Present Invention> FIG. 5 is a diagram showing the content of the second embodiment of the present invention. Specifically, in FIG. 5, solid lines A and B show the modes of change of each focal position when the focal position adjustment method according to the second embodiment of the present invention is applied, and two-dot chain lines A' and B' show the modes of change of each focal position in a comparative example where the present invention is not applied. Also, solid line A and two-dot chain line A' are the modes of change of each focal position when image lights A and A' with large energy are projected, and solid line B and two-dot chain line B' are the modes of change of each focal position when image lights B and B' with small energy are projected. Note that the content shown by solid lines A and B and two-dot chain lines A' and B' is the same in each drawing of other embodiments described hereinafter.

[0061] As shown in FIG. 5, in this case, when each of the image lights A, B, A', and B' is projected, each focal position temporarily changes greatly, then the change in the focal position is reduced, and thereafter, it becomes a stable state. Thus, the focal position may change greatly after the start of projection of the image light and then become a stable state.

[0062] In this case, in the comparative example, when the image light A' with large energy is projected, the focal position changes greatly, so that the focal position deviates from the allowable range H of the image quality. Also, even when the subsequent focal position becomes a stable state, it deviates from the allowable range H. On the other hand, in the second embodiment of the present invention, even when the image light A with large energy is projected, the focal position in the stable state is included within the allowable range H of the image quality.

[0063] Thus, in the second embodiment of the present invention, the focal position in the stable state is within the allowable range H of the image quality. However, when the change in the focal position is maximum, the focal position is outside the allowable range H of the image quality. However, since initial settings are often made by the user or the like for some time after the projection starts, it is often preferable to prioritize the image quality after the focal position has shifted to the stable state rather than the image quality until the change in the focal position becomes maximum after the projection starts. Therefore, in the second embodiment of the present invention, the focal position in the stable state is within the allowable range H so as to prioritize the image quality after the focal position has shifted to the stable state.

[0064] Also, in the second embodiment of the present invention, in order to ensure the image quality in both the stable states when the high-energy image light A is projected and when the low-energy image light B is projected, the focal positions a and b in the stable states in each case are arranged with the projection surface P therebetween. As a result, compared with the comparative example shown by the two-dot chain line in FIG. 5, the focal position can be shifted in advance to the side opposite to the focal displacement direction (the minus side of the Y axis), and each focal position a and b in the stable state can be made to be within the allowable range H of the image quality.

[0065] Subsequently, FIG. 6 shows the content of the third embodiment of the present invention.

[0066] In the third embodiment of the present invention shown in FIG. 6, the focal position changes temporarily greatly in the same manner as in the second embodiment of the present invention shown in FIG. 5. In this case, each focal position a and b when the change is maximum is within the allowable range H of the image quality.

[0067] Depending on the configuration of the image projection device, it may take a long time for the focus position to shift most significantly and then transition to a stable state. In such cases, the deterioration of the image quality until the focus position reaches the stable state may be stressful for the user. Therefore, in the third embodiment of the present invention, in order to ensure good image quality when the focus position reaches the maximum displacement, after the projection of each of the image lights A and B is started, the respective focus positions a and b when the change is maximum are adjusted so as to be arranged on opposite sides with respect to the projection surface P. As a result, since the respective focus positions a and b at the time of maximum displacement are included within the allowable range H of the image quality, the image quality when each focus position reaches the maximum displacement can be improved.

[0068] Subsequently, FIG. 7 is a diagram showing the content of the fourth embodiment of the present invention.

[0069] In the fourth embodiment of the present invention shown in FIG. 7, after starting the projection of the high-energy image light A, the projection is switched to the low-energy image light B. In this case, first, due to the projection of the high-energy image light A, the focus position temporarily changes significantly and then transitions to a stable state. Subsequently, when switched to the low-energy image light B, the focus position is significantly displaced in the direction opposite to the displacement during the projection of the high-energy image light A and then transitions to a stable state. Since the image quality may significantly deteriorate when the change in the focus position is maximum, if possible, it is preferable to ensure that the image quality is within the allowable range when the change in the focus position is maximum.

[0070] Therefore, in the fourth embodiment of the present invention, the respective focus positions a and b when the change is maximum when each of the image lights A and B is projected are arranged with respect to the projection surface P. As a result, the respective focus positions a and b at the time of maximum displacement can be included within the allowable range H of the image quality, so that the image quality can be improved.

[0071] <Regarding the relationship between the focus position and the allowable range of image quality> In each of the above embodiments, the case of projecting two types of image light, i.e., high-energy image light A and low-energy image light B, has been described as an example for each focal position. However, generally, an image projection apparatus is not limited to two types of image light, and it is possible to project various image lights having different light energies. Further, the mode of change in the focal position of these image lights varies depending on the magnitude of the light energy possessed by each image light.

[0072] FIG. 8 is a diagram showing the mode of change in the focal position for each image light having a different light energy.

[0073] In this case, the magnitude of the light energy of each image light is defined by the average picture luminance (APL). Specifically, the average picture luminance of the image light is set to approximately 0%, 30%, 50%, 70%, and approximately 100%, and the mode of change in the focal position when each image light is projected is shown in FIG. 8. Note that the average picture luminance is set to "approximately 0%" and "approximately 100%" instead of "0%" and "100%" because if it is completely "0%" or "100%", the entire image will be a black image or a white image, and the focal position cannot be adjusted.

[0074] As shown in FIG. 8, when the average picture luminance is approximately 0%, there is almost no change in the focal position. However, as the average picture luminance becomes 30%, 50%, 70%, and approximately 100%, the focal position changes greatly, and the time until the focal position reaches the maximum displacement and the time until it shifts to the stable state become shorter.

[0075] Here, in order to ensure good image quality, it is preferably such that the focal position after reaching the stable state is included within the allowable range H of the image quality. Ideally, it is preferably such that the focal position is included within the allowable range H of the image quality in the stable state of all image lights with an average picture luminance from 0% to 100%. However, it is actually difficult to satisfy such conditions. Therefore, the range for making the focal position included within the allowable range H of the image quality is preferably determined according to the actual usage mode.

[0076] Therefore, considering the actual usage patterns, it was found that the image light that is generally used frequently has an image average luminance of 30% or more and 70% or less. From this, it can be said that it is preferable that the focal position in the stable state when image light with an image average luminance of at least 30% or more and 70% or less is projected is included within the allowable range H of image quality. Therefore, as shown in FIG. 8, it is preferable that the focal position b in the stable state of the image light with an image average luminance of 30% and the focal position a in the stable state of the image light with an image average luminance of 70% are adjusted so as to sandwich the projection surface P. Also, both the focal position when the displacement amount is maximum in the image light with an image average luminance of 30% and the focal position when the displacement amount is maximum in the image light with an image average luminance of 70% may be adjusted so as to sandwich the projection surface P so that they are included within the allowable range H of image quality. Note that the two types of image light for which the focal positions a and b are adjusted are not limited to the case where the image average luminance is 30% and 70%, and can be arbitrarily set as long as the image average luminance is 30% or less and 70% or more.

[0077] Also, not limited to the case where the image average luminance of the first image light with small energy is 30% or less and the average luminance of the second image light with large energy is 70% or more, how to select the two types of image light can be appropriately changed according to the required image quality and the like.

[0078] For example, among two types of image light with different light energies, the first image light may be image light having a light energy smaller than 50% of the light energy of the maximum energy that the light source can emit, and the second image light may be image light having a light energy larger than 50% of the light energy of the maximum energy that the light source can emit.

[0079] Also, the first image light may be image light including an evaluation chart for evaluating image quality or focal position in an image with a black background in the emission mode of the darkest light that the light source can emit, and the second image light may be image light including an evaluation chart for evaluating image quality or focal position in an image with a white background in the output mode of the brightest light that the light source can output.

[0080] Further, the first image light may be image light having light energy that is 1 / 10 or less of the light energy of the second image light.

[0081] <Focus position adjustment means> Next, the focus position adjustment means will be described.

[0082] As one means for adjusting the focus position, there is a means of changing the position of some of the lenses 26 (see FIG. 3) included in the projection optical system 3 to change the distance between the lenses 26 or to change the distance between the lens 26 and the image modulation element 25. There is also a means of changing the positions of all the lenses 26 of the projection optical system 3 or changing the positions of the lenses 26 other than the lenses 26 at both ends while keeping the positions of the lenses 26 at both ends unchanged.

[0083] Further, when the image modulation element 25 is fixed to the housing and the projection optical system 3 is attached to the housing or a bracket connected to the housing, the distance between the projection optical system 3 and the image modulation element 25 may be adjusted by interposing a shim member between the bracket and the projection optical system 3 or between the bracket and the housing. If the amount of focus position shift is determined in advance, the focus position can be easily adjusted by interposing a shim member.

[0084] Further, in order to adjust the focus position, the distance between the bracket and the projection optical system 3 or between the bracket and the housing may be changed. For example, by changing the pressing amount of the spring member held therebetween, the distance between the bracket and the projection optical system 3 or between the bracket and the housing can be changed. Also, in this case, since the amount of focus position shift can be adjusted by changing the rotation angle of the screw for adjusting the pressing amount of the spring member, a more precise adjustment can be performed than the means using a shim member.

[0085] Further, when the image modulation element 25 is movable, the image modulation element 25 may be moved to change the distance between the projection optical system 3 and the image modulation element 25. In this case, since the object to be moved is the image modulation element 25 which is lighter than the projection optical system 3, the adjustment work can be easily performed.

[0086] Also, as another means for adjusting the focal position, there is a method of deforming a member interposed between the image modulation element 25 and the projection optical system 3 by heat. For example, the housing interposed between the image modulation element 25 and the projection optical system 3 may be heated by a heater to cause thermal expansion, thereby changing the distance between the image modulation element 25 and the projection optical system 3. By using a heater, the housing can be thermally expanded quantitatively, so that the focal position can be adjusted with high accuracy.

[0087] Alternatively, instead of the heater, heat generated in the image projection apparatus may be used to warm the housing or the like. For example, when image light is generated by the image modulation element 25, heat is generated when the image light irradiates a member other than the projection optical system 3 (for example, an off-light plate), and this heat may be used as heat for warming the housing or the like. Also, heat generated from the light source may be used as heat for warming the housing or the like. These methods can reduce the power consumption compared to the case of using a heater, so that energy saving can be achieved. Further, by controlling the amount of thermal expansion of the housing or the like using a temperature sensor or a strain gauge, more accurate adjustment of the focal position becomes possible.

[0088] Also, as shown in FIG. 9, in order to easily adjust the focal position, a third image light C having a focal position c may be projected between two focal positions a and b to be adjusted. For example, in monochrome image light, when the image light with a black ratio of 90% or more is the first image light and the image light with a white ratio of 90% or more is the second image light, the third image light is the image light in the range where the ratio of white or black is 35% or more and 65% or less. Also, when the first image light is the image light with an average luminance of 30% and the second image light is the image light with an average luminance of 70%, the third image light may be the image light in the range where the average luminance is 40% or more and 70% or less.

[0089] By a user or the like projecting such third image light and adjusting so that the focal position c at that time coincides with the projection surface P, the focal position a of the image light having higher light energy than the third image light and the focal position b of the image light having lower light energy than the third image light are adjusted to be located on opposite sides of each other with the projection surface P interposed therebetween. In the example shown in FIG. 9, the focal position c of the third image light C adjusted to coincide with the projection surface P is the focal position in the stable state, but the focal position c can be arbitrarily set.

[0090] Also, the third image light C may be set to image light having an image average luminance of about 50%, and the image average luminance of the third image light C may be changed according to the content or mode of the projected image light. For example, since the image light when projecting presentation materials or the like often has a relatively high image average luminance, in the presentation mode, the image average luminance of the third image light C may be changed to 70%. On the other hand, since the image light when projecting videos such as movies often has a relatively low image average luminance, in the movie mode or theater mode, the image average luminance of the third image light C may be changed to 30%. Thus, by arbitrarily changing the image average luminance of the third image light C according to the projection mode of the image projection apparatus, good image quality can be ensured.

[0091] Also, the third image light may be image light including an evaluation chart for evaluating image quality or a focal position. In this case, since a user or the like can adjust the focal position while visually observing the evaluation chart so that the image quality of the evaluation chart improves, the adjustment of the focal position becomes easy. The evaluation chart may be characters such as alphabets and numbers, as well as symbols and figures, as long as it is an image whose image quality can be visually confirmed.

[0092] Further, the evaluation chart may be projected onto at least one of a plurality of regions u1 to u13 obtained by partitioning the projection surface P in a matrix shape as shown in FIG. 10. By projecting the evaluation chart onto any region of the projection surface P and adjusting it so that the focal position of the evaluation chart coincides with the projection region, the focal positions a and b of the first image light and the second image light can be arranged as shown in FIG. 11, for example.

[0093] In FIG. 11, the focal positions a and b of the first image light and the second image light for each of the plurality of regions u1 to u13 partitioning the projection surface P are shown. The white circles in FIG. 11 are the focal positions b of the first image light having small light energy, and the black circles in the figure are the focal positions a of the second image light having large light energy. Note that in region u8, the focal positions a and b could not be measured, so the white and black circles are not shown. Thus, by using the evaluation chart included in the third image light C, the focal positions a and b of the first image light and the second image light can be adjusted to be located on opposite sides across the projection surface P.

[0094] Note that when the projection surface P is large or somewhat curved, it may not be possible to make the focal positions of the evaluation chart coincide in all regions u1 to u13 of the projection surface P. In such a case, for example, the focal position of the evaluation chart may be made to coincide in the central region u5, and then the focal position of the evaluation chart may be made to coincide in each of the upper regions u1, u2, u3, u10, u11, etc. by a mechanism for changing the projected image size.

[0095] <Focus adjustment mechanism> Subsequently, the configuration of the focus adjustment mechanism included in the image projection apparatus according to the present invention will be described.

[0096] FIG. 12 is a schematic diagram showing an example of the focus adjustment mechanism 400.

[0097] As shown in FIG. 12, the focus adjustment mechanism 400 includes an interface unit 401, a processing unit 402, a recording unit 403, an image projection unit 404, and a focus drive unit 405.

[0098] The interface unit 401 acquires information output from an information processing device 300 such as a personal computer that outputs image information or a memory in which image information is stored. The processing unit 402 is a part that processes the image information input from the interface unit 401. The recording unit 403 stores image information for focus adjustment. This image information for focus adjustment is information on a third image light C having a focus position c between two focus positions a and b to be adjusted, or an evaluation chart included therein. The image projection unit 404 is a part that generates and projects image light based on the image information input from the processing unit 402, and is composed of an image generation unit 2 and a projection optical system 3 shown in FIG. 2.

[0099] The focus drive unit 405 moves a part or all of a plurality of lenses included in the projection optical system 3 of the image projection unit 404 in the axial direction of the projection light in order to match the focus of the image light for focus adjustment (third image light C) with the projection surface P at a desired projection position on the projection surface. In the example of FIG. 12, the focus drive unit 405 and the lens of the projection optical system 3 are connected via a focus connection unit 406, but the focus drive unit 405 may be included in the image projection unit 404.

[0100] By providing the focus adjustment mechanism 400 as described above in the image projection device 100, the adjustment of the focus position can be easily performed. The adjustment of the focus position by the focus adjustment mechanism 400 may be performed automatically or manually. In the case of manual adjustment, the focus drive unit 405 is not necessary, and means for detecting an operation for adjusting the focus position, or means for detecting that an operation for adjusting the focus position has been performed may be provided. Also, as means for detecting these, means for detecting whether or not a focus adjustment mode has been selected may be used. Further, when the focus position is automatically adjusted, when the selection of the focus adjustment mode is detected, the image light for focus adjustment is projected from the image projection unit 404 based on the image information stored in the recording unit 403.

[0101] <Focus position adjustment flow> FIG. 13 is a diagram showing the flow of focus position adjustment by the focus adjustment mechanism 400.

[0102] As shown in FIG. 13, when it is detected that the focus adjustment mode has been turned on, information on the image light projected during focus adjustment is read from the recording unit 403 to the processing unit 402. That the focus adjustment mode has been turned on can be confirmed, for example, when the detection means detects a signal emitted from the remote controller or the device when the user starts a focus adjustment operation using a remote controller or the like. When the image information for focus adjustment is read by the processing unit 402, in the processing unit 402, the image information from the information processing apparatus 300 that has been input until then is switched to the image information for focus adjustment. Then, the image projection unit 404 generates and projects image light based on the image information for focus adjustment input from the processing unit 402. As a result, an image for focus adjustment is projected onto the projection surface, so that the user or the like visually observes the projected image and adjusts the focus position so that the focus of the image coincides with the projection surface.

[0103] On the other hand, when it is not detected that the image adjustment mode is ON, the image information from the information processing apparatus 300 is read by the processing unit 402, and a projection mode based on the image information (externally input image) is executed.

[0104] As described above, when it is detected that the image adjustment mode is ON, the focus position is adjusted based on the image for focus adjustment, so that the respective focus positions a and b of the first image light and the second image light having different magnitudes of light energy can be adjusted to be located on opposite sides of each other with the projection surface P interposed therebetween. In addition, since the user can automatically adjust the focus position based on the image for focus adjustment projected onto the projection surface, the focus position can be easily adjusted. In addition to the case where the focus position is manually adjusted while the user or the like visually observes the image for focus adjustment projected onto the projection surface, the projected image may be imaged and automatically adjusted so that the contrast is optimal.

[0105] <Example of Image for Focus Adjustment> Here, with reference to FIGS. 17 to 20, the focus adjustment image used when a user performs focus adjustment of the image projection apparatus or when an assembly worker performs focus adjustment of the image projection apparatus in the manufacturing process will be described.

[0106] FIG. 17 is a diagram showing an example of the arrangement of evaluation charts included in the focus adjustment image. In the example of FIG. 17, the projection surface P is divided into nine regions u1 to u9 in a uniform matrix shape.

[0107] In the manufacturing process of the image projection apparatus, in order to maintain the desired projection image quality, it is common to project a large number of evaluation charts of the focus adjustment image within the projection surface so that the focus positions across the entire projection surface can be adjusted. Therefore, for example, it is preferable to project evaluation charts at the centers o1 to o9 of the nine divided regions U1 to u9 in FIG. 17, perform assembly adjustment of the components so that the foci of the respective evaluation charts are in focus, and perform an inspection process.

[0108] On the other hand, when a user performs focus adjustment of the image projection apparatus, when a large number of evaluation charts are projected on the projection surface P, the user often gets confused as to which evaluation chart to focus on for adjustment. Also, for an image projection apparatus that has been adjusted to a certain quality in the manufacturing process, when a user performs focus adjustment, it is not necessarily required to perform a focus adjustment operation to the same extent as in the manufacturing process. Rather, when a user performs focus adjustment, it is preferable that the focus adjustment operation is as simple as possible, and the projected focus adjustment image is also preferably as simple as possible.

[0109] Therefore, when the user performs focus adjustment, instead of projecting the evaluation chart onto all of the centers o1 to o9 of the nine regions U1 to U9 as in the manufacturing process, it is preferable to project the evaluation chart 90 onto a total of five locations, i.e., the center o5 of the projection surface P and the vicinity of the four corners c1 to c4, as in the example of FIG. 17. By projecting the evaluation chart 90 onto the center o5 of the projection surface P and the vicinity of the four corners c1 to c4 in this way, it is possible to ensure the resolution performance of the center and the periphery of the projection surface P, and to ensure a certain projection image quality. In addition, since the number of projection locations of the evaluation chart 90 is only five, the viewpoint movement can be minimized, making the device easy to handle for the user. Further, since the total area of the evaluation chart 90 can be minimized, when the image average luminance (APL) of the background portion without the evaluation chart 90 is determined, the evaluation chart 90 itself does not necessarily have the value of the determined image average luminance (APL). Therefore, the difference between the value of the determined image average luminance (APL) and the value of the actual image average luminance (APL) including the plurality of evaluation charts 90 can be reduced. For this reason, it is most preferable that the projection locations of the evaluation chart 90 be about five locations at the center and the periphery of the projection surface P.

[0110] Specifically, in addition to the center o5 of the projection surface P, the evaluation chart 90 is preferably arranged at positions near the corners c1 to c4 on the four straight lines connecting the center o5 and the four corners c1 to c4. More specifically, in addition to the center o5 of the projection surface P, the evaluation chart 90 is preferably arranged at the centers o1, o3, o7, o9 of the regions u1, u3, u7, u9 including the four corners c1 to c4 of the projection surface P, or at positions e1, e3, e7, e9 between these centers o1, o3, o7, o9 and the four corners c1 to c4, or at the four corners c1 to c4. Further, the evaluation chart 90 projected near the four corners c1 to c4 may be arranged at positions (the positions shown in FIG. 17) between the centers o1, o3, o7, o9 of the regions u1, u3, u7, u9 including the four corners c1 to c4 and the corner-near positions e1, e3, e7, e9.

[0111] In this way, by selecting, as the projection positions of the evaluation chart 90, the center o5 of the projection surface P and the positions near the four corners c1 to c4 (the positions between the centers o1, o3, o7, o9 of the respective regions u1, u3, u7, u9 including the four corners c1 to c4 and the respective corners c1 to c4), it is possible to perform focus adjustment while considering the balance of the projected image at the location where the quality of the projected image at the center o5 is most prominent and near the four corners c1 to c4 where focusing is most difficult.

[0112] When the user performs focus adjustment, it is preferable to pre-set a simple mode different from the focus adjustment mode in the manufacturing process so that the mode of projecting the evaluation chart to the above-mentioned five locations can be selected. Also, since some users may desire to perform more detailed focus adjustment, in such cases, a plurality of detailed modes in which the evaluation chart can be projected to more locations than five may be set, and a preferable mode may be selectable according to the use of the image projection device. Further, when the person in charge of installing or servicing the device performs focus adjustment, an image for focus adjustment in the service mode in which the evaluation chart can be projected to more locations than five may be prepared.

[0113] FIGS. 18(a) and (b) are diagrams showing other embodiments of the image for focus adjustment.

[0114] In the example of FIG. 18(a), the evaluation chart 90 of the image for focus adjustment is displayed as black cross lines (vertical and horizontal cross shapes) on a white background. Here, the evaluation chart 90 is projected to five locations, namely, the center o of the projection surface P and the four corners c1 to c4. Among the image for focus adjustment, the background portion 91 other than the evaluation chart 90 has a pattern in which the image average luminance (APL) is adjusted to a desired value of, for example, 50%. That is, it is a halftone image in which the tone is selected so that the brightness of the output image becomes 50% with respect to white. Specifically, when using 256 gradations in the case of γ = 2.2 described later, if the gradation value is appropriately determined (for example, about 186), the output value becomes about 50%, and an image corresponding to an image average luminance (APL) of 50% can be obtained.

[0115] Subsequently, in the example of FIG. 18(b), the evaluation chart 90 is displayed as a pair of lines of a black double cross line (vertical and horizontal cross shape) on a white background. Among the images for focus adjustment, the background portion 91 other than the evaluation chart 90 has a pattern in which the image average luminance (APL) is adjusted to a desired value such as 50%. In FIG. 18(b), the background portion 91 appears gray, but when the background portion 91 is magnified in pixel units (see the enlarged view in FIG. 18(b)), white pixels and black pixels are alternately projected. That is, in this case, for each pixel, either all white or all black, a binary value, is projected at a ratio of 1:1, and the image average luminance (APL) is determined by the ratio of the number of white pixels to the number of black pixels.

[0116] FIG. 19 is a diagram showing another embodiment of the evaluation chart.

[0117] The examples of the evaluation chart shown in FIG. 19 are various embodiments of the evaluation chart particularly when the user performs focus adjustment (simple mode). As shown in FIG. 19, in addition to changing the color of the cross line portion of the evaluation chart to white or black, or configuring the cross line portion with a single line or a plurality of lines, a large number of combinations are selectable, such as changing the color of the background portion of the evaluation chart to black or white.

[0118] Also, when the user performs focus adjustment, in order to make it easier to handle, it is preferable to make the width of the lines of the evaluation chart, that is, the number corresponding to the number of pixels, larger (coarser resolution) than the pixel unit of the image modulation element. If the line width of the evaluation chart is the same as the pixel unit (resolution performance) of the image modulation element, the sensitivity of focusing becomes high and it becomes difficult for the user to adjust. Therefore, it is preferable to use a pair of white and black of a plurality of consecutive lines. In this way, by setting the width of the lines of the evaluation chart to twice or three times the panel resolution performance, it becomes easier for the user to perform focus adjustment. However, this is not the case when the assembler in the manufacturing process or the service person performs focus adjustment. It is appropriate to use an evaluation chart composed of lines or characters represented in pixel units of the image modulation element.

[0119] FIG. 20(a) to (c) are diagrams showing other embodiments of the background portion of the focus adjustment image.

[0120] In FIG. 20, (a) shows an example of the background portion 91 where the image average luminance (APL) is 50%, (b) shows an example of the background portion 91 where the image average luminance (APL) is 60%, and (c) shows an example of the background portion 91 where the image average luminance (APL) is 80%. Thus, by setting each pixel to a white pixel or a black pixel, the image average luminance (APL) can be accurately determined. In the case of gray display, since the image average luminance (APL) depends on the tone reproduction ability, an accurate image average luminance (APL) cannot be determined. This is due to the fact that multiple γ curves can be selected. For example, in the case of an image projection device that can display 256 gradations from black 0 to white 255, the luminance information of the input signal and the display gradation value are often not linear, and are generally convex-down exponential functions, and there are multiple such functions (functions called γ curves). The exponent part when the relationship between the input value x and the output value y in this γ curve is y = x γ is shown, and generally, γ can take values around γ = 2, or γ = 0, or γ = 2.2. Image projection devices often have a large number of video representation modes. Even if a gradation value is selected to display 50% gray, the gradation value changes depending on the value of γ, so an accurate image average luminance (APL) cannot be determined. The method of determining the image average luminance (APL) that does not depend on such γ is to define the image average luminance (APL) by the ratio of the number of white and black pixels. Thereby, it becomes possible to obtain a background image having an accurate image average luminance (APL).

[0121] As described above, the focus adjustment image and the evaluation chart in the case of performing focus adjustment using FIGS. 17 to 20 have been described. However, the focus adjustment image may be projected based on the image information stored in the image projection device in advance, or may be projected based on the image information input from an external device to the image projection device.

[0122] Also, the image projection device according to the present invention is not limited to the above-described embodiments.

[0123] For example, the present invention is applicable not only to an image projection device that projects image light onto a flat surface such as a screen, but also to an image projection device that projects image light onto a three-dimensional structure such as a vehicle body or a building. Therefore, in the present invention, the focal positions a and b of the first image light and the second image light to be adjusted do not necessarily have to be adjusted so as to sandwich the entire projection surface P therebetween. For example, when the projection surface is a surface having irregularities and the distance from the image projection device to the projection surface varies greatly depending on each part of the projection surface, at least a part of the projection surface may be adjusted to be located between the focal positions a and b of the first image light and the second image light.

[0124] In addition, as applications of the image projection device according to the present invention, it can be used in various scenes such as business use (projection display for business, meetings, presentations, etc.), home use, medical use (projection display of monochromatic medical images such as X-ray images of X-rays and MRI (Magnetic Resonance Imaging) images), public use (projection display of various guides, advertisements, signage, etc. in public places, stores, and transportation facilities), and factory installation use. Further, the image projection device according to the present invention has a projection mode corresponding to each application (color mode, video mode, image mode, medical mode for projecting medical images, public mode for projecting guides or signage outdoors, in stores, etc.), and may automatically change the driving method and the control of the driving amount such as the light source, power, cooling, and output according to the change of the mode.

[0125] Summarizing the aspects of the present invention, the present invention includes at least the following aspects.

[0126] [First Aspect] A first aspect includes a light source, an image light generation unit that receives light emitted from the light source to generate image light, and a projection optical system that projects the image light generated by the image light generation unit onto a projection surface. The image light projected from the projection optical system onto the projection surface includes first image light having a predetermined light energy and second image light having a light energy greater than that of the first image light. The focal positions when the first image light is projected and the focal positions when the second image light is projected are arranged so as to sandwich at least a part of the projection surface. This is an image projection device.

[0127] [Second Aspect] In a second aspect, in the first aspect, each of the focal positions arranged so as to sandwich at least a part of the projection surface is the focal position when the change in each of the focal positions has reached a stable state after the projection of the first image light and the second image light has started.

[0128] [Third Aspect] In a third aspect, in the first aspect, each of the focal positions arranged so as to sandwich at least a part of the projection surface is the focal position when the temperature change of the projection optical system has reached a stable state after the projection of the first image light and the second image light has started.

[0129] [Fourth Aspect] In a fourth aspect, in the first aspect, each of the focal positions arranged so as to sandwich at least a part of the projection surface is the focal position when the change in each of the focal positions has reached its maximum after the projection of the first image light and the second image light has started.

[0130] [Fifth Aspect] In the fifth aspect, in any one of the first to fourth aspects, the distance between the respective focal positions arranged so as to sandwich at least a part of the projection surface is L, the distance between the focal position when the first image light is projected and the projection surface is La, and the distance between the focal position when the second image light is projected and the projection surface is Lb. Then, the relationship L / 3 ≦ La, Lb ≦ 2L / 3 is satisfied.

[0131] [Sixth Aspect] In the sixth aspect, in any one of the first to fifth aspects, the first image light has a smaller average image luminance than the second image light.

[0132] [Seventh Aspect] In the seventh aspect, in any one of the first to sixth aspects, the first image light is monochromatic image light having a smaller area ratio of white image light than the second image light.

[0133] [Eighth Aspect] In the eighth aspect, in any one of the first to seventh aspects, the first image light is image light having a light energy smaller than 50% of the maximum energy light that the light source can emit, and the second image light is image light having a light energy larger than 50% of the maximum energy light.

[0134] [Ninth Aspect] In the ninth aspect, in any one of the first to eighth aspects, the first image light is in the darkest light emission mode that the light source can emit, and is image light including an evaluation chart for evaluating image quality or focal position in an image with a black background. The second image light is in the brightest light output mode that the light source can output, and is image light including an evaluation chart for evaluating image quality or focal position in an image with a white background.

[0135] [Tenth Aspect] In the tenth aspect, in any one of the first to ninth aspects, the light energy of the first image light is 1 / 10 or less of the light energy of the second image light.

[0136] [Aspect 11] Aspect 11 is capable of projecting third image light having a focal position between each of the focal positions arranged so as to sandwich at least a part of the projection surface in any one of Aspects 1 to 10.

[0137] [Aspect 12] Aspect 12 is, in Aspect 11, the third image light is image light including an evaluation chart for evaluating image quality or a focal position.

[0138] [Aspect 13] Aspect 13 is, in Aspect 11 or 12, provided with a focus adjustment mechanism that moves at least one lens included in the projection optical system when projecting the third image light.

Explanation of Reference Signs

[0139] 1 Lighting device 2 Image light generation unit 3 Projection optical system 4 First light source unit 5 Second light source unit 6 Color wheel 7 Light homogenizing element 8 Light source 9 Collimator lens 10 Condensing element 11 Dichroic mirror 12 Wavelength conversion element 13 Combining optical element 25 Image modulation element 26 Lens 100 Image projection device 200 Focus adjustment mechanism a Focal position when the second image light is projected b Focal position when the first image light is projected P Projection surface

Prior Art Documents

Patent Documents

[0140] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-313201

Claims

1. A light source; an image light generating unit that receives light emitted from the light source and generates image light; a projection optical system that projects the image light generated by the image light generation unit onto a projection surface; Equipped with The image light projected from the projection optical system to the projection surface is a first image light having a predetermined light energy; a second image light having a light energy greater than that of the first image light; Including, An image projection device, characterized in that a focal position when the first image light is projected and a focal position when the second image light is projected are arranged so as to sandwich at least a portion of the projection surface.

2. The image projection device of claim 1, wherein each of the focal positions arranged to sandwich at least a portion of the projection surface is a focal position when the change in each of the focal positions becomes stable after projection of the first image light and the second image light has begun.

3. The image projection device of claim 1, wherein each of the focal positions arranged to sandwich at least a portion of the projection surface is a focal position when the temperature change of the projection optical system becomes stable after projection of the first image light and the second image light is started.

4. The image projection device of claim 1, wherein each of the focal positions arranged to sandwich at least a portion of the projection surface is a focal position at which the change in each of the focal positions is maximum after projection of the first image light and the second image light is started.

5. A distance between the focal positions arranged so as to sandwich at least a part of the projection surface is defined as L, The distance between the focal position and the projection surface when the first image light is projected is defined as La, If the distance between the focal position when the second image light is projected and the projection surface is Lb, then 2. The image projection device according to claim 1, wherein the relationships L / 3.ltoreq.La, Lb.ltoreq.2L / 3 are satisfied.

6. 2. The image projection device according to claim 1, wherein the first image light has an average image luminance lower than that of the second image light.

7. 2. The image projection device according to claim 1, wherein the first image light is a monochrome image light having a smaller area ratio of white image light than the second image light.

8. the first image light is image light having light energy less than 50% of the maximum energy of light that can be emitted by the light source, 2. The image projection device according to claim 1, wherein the second image light has a light energy that is greater than 50% of the light with the maximum energy.

9. the first image light is image light in an emission mode of the dimmest light that can be emitted by the light source, the image having a black background and including an evaluation chart for evaluating image quality or a focal position; 2. The image projection device according to claim 1, wherein the second image light is image light including an evaluation chart for evaluating image quality or focal position against a white background in an output mode of the brightest light that the light source can output.

10. 2. The image projection device according to claim 1, wherein the light energy of the first image light is equal to or less than one tenth of the light energy of the second image light.

11. The image projection device according to claim 1 , capable of projecting a third image light having a focal position between the focal positions arranged so as to sandwich at least a part of the projection surface.

12. 12. The image projection device according to claim 11, wherein the third image light is image light including an evaluation chart for evaluating image quality or a focal position.

13. 13. The image projection device according to claim 11, further comprising a focus adjustment mechanism that moves at least one lens of the projection optical system when projecting the third image light.

Images