Image projection apparatus

Abstract

The present invention relates to an image projection device capable of adjusting a focal position according to a change in the focal position. The image projection device comprises: a light source; an image light generation unit (2) for receiving light emitted from the light source and generating image light; and a projection optical system (3) that projects the image light generated by the image light generation unit (2) onto a projection surface (P). The image projection apparatus is configured such that a focal position (b) when projecting first image light having a predetermined light energy and a focal position (a) when projecting second image light having a light energy greater than that of the first image light are each positioned on both sides of at least a portion of the projection surface (P).

Description

Technical Field

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

[0002] As is known to all, the existing image projection device focuses the light emitted by the light source onto an image modulation element such as a DMD (Digital Micromirror Device), and then projects the image light modulated by the image modulation element onto a projection surface such as a screen.

[0003] However, as the image projection device operates, the temperature inside the device rises, the optical characteristics of the projection optical system change, and the focal position of the image light projected onto the projection surface changes, causing the existing image projection device to suffer from a degradation in image quality.

[0004] In order to solve the above problems, for example, Patent Document 1 (Japanese Patent Application Publication No. 2006-313201) discloses a method for adjusting the focus position by using the chromatic aberration of the image light or the distortion of the projected image. This method uses the image light of a specific wavelength (color) or a specific part of the projected image to pre-move the initial focus position of the projection in the direction opposite to the direction in which the position change occurs, thereby suppressing the degradation of the image quality by offsetting the position deviation caused by the change of the focus position due to the temperature rise.

[0005] However, in the focus position adjustment method using chromatic aberration or distortion, there is a problem that the focus position adjustment range is limited to the range of chromatic aberration or distortion. Therefore, when the displacement width of the focus position exceeds the range of chromatic aberration or distortion, the focus position cannot be fully adjusted according to the focus position change. Summary of the invention

[0006] In view of this, an object of the present invention is to adjust the focus position according to the focus position change.

[0007]

Methods to solve the problem

[0008] In order to solve the above problems, the present invention provides:

[0009] An image projection device, comprising:

[0010] light source;

[0011] an image light generating unit, configured to receive the light emitted from the light source and generate image light; and

[0012] a projection optical system that projects the image light generated by the image light generating unit onto a projection surface,

[0013] It is characterized in that

[0014] The focal position when a first image light having a predetermined light energy is projected and the focal position when a second image light having a light energy greater than that of the first image light is projected are respectively located on both sides of at least a portion of the projection surface.

[0015] The present invention has the effect of being able to adjust the focus position according to the change in the focus position. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the overall structure of the image projection device according to the first embodiment of the present invention.

[0017] Figure 2 This is a block diagram of the hardware configuration of the image projection device according to the first embodiment of the present invention.

[0018] Figure 3 It is a schematic diagram of a method for adjusting a focal position according to the first embodiment of the present invention.

[0019] Figure 4 It is a schematic diagram showing the change of the focal position in the first embodiment of the present invention.

[0020] Figure 5 It is a schematic diagram showing the contents of the second embodiment of the present invention.

[0021] Figure 6 It is a schematic diagram showing the contents of the third embodiment of the present invention.

[0022] Figure 7 It is a schematic diagram showing the contents of the fourth embodiment of the present invention.

[0023] Figure 8 It is a schematic diagram of the changes in the focal positions of image lights with different light energy levels.

[0024] Fig. 9 is a schematic diagram of an example in which a third image light having a focal position between two focal positions can be projected.

[0025] Fig.10 This is a schematic diagram showing a state where the projection surface is divided into a matrix consisting of a plurality of areas.

[0026] Fig.11 It is a schematic diagram of the focal positions of the first image light and the second image light in various areas of the projection surface.

[0027] Fig.12 This is a schematic diagram of an example of focus adjustment performed by the focus adjustment mechanism.

[0028] Fig.13 This is a diagram showing the focus position adjustment process of the focus adjustment mechanism.

[0029] Fig.14 This is a schematic diagram of the state before the focus position changes.

[0030] Fig.15 This is a schematic diagram of the state after the focus position is changed.

[0031] Fig.16 It is a schematic diagram of the displacement of the respective focal positions when two image lights with different energy levels are projected.

[0032] Fig.17 This is a schematic diagram showing an example of the layout of the evaluation chart in the focus adjustment image.

[0033] Fig.18 It is a schematic diagram of another embodiment of an image for focus adjustment.

[0034] Fig.19 is a schematic diagram of another embodiment of an evaluation chart.

[0035] Fig. 20 FIG. 1 is a schematic diagram of another embodiment of the background portion of the focus adjustment image.

[0036] Explanation of symbols

[0037] 1 lighting device

[0038] 2 Image light generating unit

[0039] 3 Projection optical system

[0040] 4First light source unit

[0041] 5 Second light source unit

[0042] 6 Color Wheel

[0043] 7Light homogenization element

[0044] 8 Light Source

[0045] 9Collimating lens

[0046] 10 Focusing element

[0047] 11Dichroic Mirror

[0048] 12Wavelength conversion element

[0049] 13 Optical elements for synthesis

[0050] 25 Image modulation element

[0051] 26 lenses

[0052] 100 Image Projection Device

[0053] 200 Focus adjustment mechanism

[0054] aFocus position when projecting the second image light

[0055] bFocal position when projecting the first image light

[0056] P projection surface DETAILED DESCRIPTION

[0057] [First embodiment]

[0058] First, according to Figure 1 The overall structure of an image projection device 100 according to the first embodiment of the present invention will be described. In the drawings, components such as parts having the same function or shape are denoted by the same reference numerals to the extent that they can be distinguished, and duplicate descriptions are omitted.

[0059] <Overall Structure of Image Projection Device>

[0060] like Figure 1 As shown, the image projection device 100 involved in the first embodiment of the present invention includes an illumination device 1, an image light generating unit 2, and a projection optical system 3. The illumination device 1 is a device that irradiates light to the image light generating unit 2. The image light generating unit 2 is a part that receives the light irradiated by the illumination device 1 and generates image light. Specifically, the image light generating unit 2 has an image modulation element such as a DMD (Digital Micromirror Device) or a liquid crystal panel. After the illumination device 1 irradiates light to the image light generating unit 2, the image modulation element modulates the light to generate image light. The projection optical system 3 is an optical system that projects the image light generated by the image light generating unit 2 onto a projection surface such as a screen. The projection surface includes a virtual projection surface such as a projection surface provided as a specification of the image projection device 100.

[0061] The lighting device 1 is composed of a first light source unit 4, a second light source unit 5, a color wheel 6, a synthesizing optical element 13, a light homogenizing element 7, and the like.

[0062] Each of the light source units 4 and 5 includes a light source 8 , a collimator lens 9 , a condenser element 10 , a dichroic mirror 11 , and a wavelength conversion element 12 .

[0063] The light source 8 uses, for example, LD (Laser Diode). A collimating lens 9 is provided at a position opposite to the light source 8. The collimating lens 9 is a lens that converts the excitation light emitted from the light source 8 into a parallel light beam. The focusing element 10 converges the excitation light converted into parallel light by the collimating lens 9. The focusing element 10 includes a first focusing element 10A provided between the collimating lens 9 and the dichroic mirror 11 in the direction of travel of the light, a second focusing element 10B between the dichroic mirror 11 and the wavelength conversion element 12, and a third focusing element 10C between the wavelength conversion element 12 and the color wheel 6.

[0064] The dichroic mirror 11 is a wavelength selective reflection mirror that reflects only light of a specific wavelength and transmits light of other wavelengths.

[0065] The wavelength conversion element 12 is, for example, a disk-shaped phosphor wheel. The first embodiment of the present invention is described by taking the example that the light source 8 is a blue laser light source and the wavelength conversion element 12 is a phosphor wheel.

[0066] In each light source unit 4, 5, after the light source 8 emits light (blue light), the light is condensed by the first condensing element 10A, and the condensed light is guided to the dichroic mirror 11. Then, only the light of a specific wavelength is reflected by the dichroic mirror 11, and is further condensed by the second condensing element 10B, thereby generating a predetermined condensing spot on the phosphor wheel as the wavelength conversion element 12.

[0067] The phosphor wheel is a disc-shaped component that is driven by a driving motor to rotate at high speed. The phosphor wheel has a wavelength conversion area, i.e., a phosphor area, on which a phosphor is applied, and a non-wavelength conversion area, i.e., an excitation light reflection area, that reflects excitation light. As the phosphor wheel rotates, the excitation light reflection area and the phosphor area are switched at the position of the light-converging point on the phosphor wheel.

[0068] When the excitation light reflection area of ​​the phosphor wheel is located at the position of the focusing spot, the light is not wavelength-converted and blue light is directly output. When the phosphor area of ​​the phosphor wheel is located at the position of the focusing spot, the light is wavelength-converted to yellow or yellow-green fluorescent output. The phosphor wheel is not limited to being divided into two areas, the excitation light reflection area and the phosphor area, and may also be a component having a plurality of fluorescent areas (for example, a fluorescent area emitting yellow light, a fluorescent area emitting green light) converted into wavelengths different from each other. A semiconductor blue laser light source having an oscillation wavelength with a peak wavelength between 440nm and 465nm is preferably used as the blue laser light source.

[0069] The light beam reflected by the phosphor wheel (wavelength conversion element 12) passes through the second light focusing element 10B again, and is then focused by the third light focusing element 10C. Then, the focused light passes through the color wheel 6 and enters the light homogenizing element 7. In this case, the light focused by the third light focusing element 10C of the first light source unit 4 travels straight, passes through the color wheel 6, and is guided to the light homogenizing element 7. On the other hand, the light focused by the third light focusing element 10C of the second light source unit 5 is reflected by a reflector as a synthesis optical component 13, and its traveling route is changed to the same direction as the light of the first light source unit 4, and then is guided to the color wheel 6 and the light homogenizing element 7. As the synthesis optical element 13, a prism may be used in addition to a reflector.

[0070] The color wheel 6 is driven by a motor to rotate, and the light from each light source unit 4, 5 is divided into red, blue, green, and yellow light components by the color wheel 6, and output to the light homogenizing element 7. Specifically, the color wheel 6 has a transparent portion that allows the blue component and the yellow component light to pass through, a red filter that extracts the red component light from the yellow fluorescence, and a green filter that increases the purity of the green component of the green fluorescence and then extracts the light. The light guided by the synthesis optical component 13 is divided into each color component by the rotating color wheel 6, and then output to the light homogenizing element 7.

[0071] As for the light homogenizing element 7, for example, a light tunnel whose interior is made hollow and whose inside is combined with four reflectors, a rod-shaped integrator whose corner columns are formed of transparent materials such as glass, or a fly-eye lens can be used. For example, when a light tunnel is used as the light homogenizing element 7, by forming it to have substantially the same aspect ratio as that of the image light generating unit 2, the shape of the exit of the light tunnel becomes the shape projected onto the surface of the image light generating unit 2, and the surface of the image light generating unit 2 can be effectively irradiated.

[0072] The light homogenized by the light homogenizing element 7 is irradiated to the image light generating unit 2, which modulates the light to generate image light. The image light generated by the image light generating unit 2 is amplified by the projection optical system 3 and projected onto the projection surface.

[0073] Next, the cooling mechanism of the image projection apparatus 100 according to the first embodiment of the present invention will be described.

[0074] like Figure 1 As shown, the image projection device 100 according to the first embodiment of the present invention is provided with a plurality of heat receiving components 14, a plurality of heat dissipating components 15, and a plurality of airflow generating devices 16, which are used as cooling mechanisms inside the cooling device.

[0075] The plurality of heat receiving members 14 are in contact with the light sources 8 and the wavelength conversion elements 12 of the 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 of the housing 20 constituting the lighting device 1.

[0076] The plurality of heat dissipating members 15 are provided so as to contact the heat receiving members 14 on the outside of the housing 20 of the lighting device 1 and also contact the outer surface of the housing 21 that accommodates the image light generating unit 2 and the light homogenizing element 7. Each heat dissipating member 15 is constituted by, for example, a heat sink having a plurality of fins. The shape of the fins may be any shape as long as it has at least a plurality of concavities and convexities, and may include plate fins, pin fins, corrugated fins, and the like.

[0077] A plurality of airflow generating devices 16 are provided near the heat dissipation component 15 and near the circuit board 17 in the image projection device 100. Each airflow generating device 16 is composed of, for example, an axial flow fan or a sirocco fan. A plurality of air supply ports 18 for supplying air into the device and exhaust ports 19 for exhausting air are provided on the outer casing 22 of the image projection device 100 by driving the airflow generating devices 16.

[0078] As described above, in the image projection device 100 according to the first embodiment of the present invention, the plurality of heat receiving components 14 are provided so as to be in contact with the respective light sources 8 and the respective wavelength conversion elements 12, so that the heat generated from the respective light sources 8 and the respective wavelength conversion elements 12 is transferred to the heat receiving components 14. Then, the heat transferred to the heat receiving components 14 is transferred to the respective heat dissipating components 15 in contact with the respective heat receiving components 14, and is dissipated in the respective heat dissipating components 15. In this way, the respective light sources 8 and the respective wavelength conversion elements 12 can be cooled. Furthermore, the airflow generated by the airflow generating device 16 improves the heat dissipation effect of the heat dissipating components 15, and also cools the circuit board 17. In addition, the heat released from the respective heat dissipating components 15 and the like is discharged to the outside of the device from the exhaust port 19 by the airflow generated in the device, so that the temperature rise in the image projection device 100 can be suppressed.

[0079] <Hardware Configuration>

[0080] Next reference Figure 2 , a hardware configuration of an image projection device 100 according to a first embodiment of the present invention will be described.

[0081] like Figure 2 As shown, the image projection device 100 includes a CPU (Central Processing Unit) 801, a ROM (Read Only Memory) 802, a RAM (Random Access Memory) 803, a medium I / F (Interface) 807, an operation unit 808, a power switch 809, a bus 810, a network I / F 811, a light source driving circuit 814, a light source 8, an image light generating unit 2, a projection optical system 3, a peripheral connection I / F 818, an airflow generating device driving circuit 819 and an airflow generating device 16.

[0082] The CPU 801 controls the overall operation of the image projection device 100. The ROM 802 stores a program for driving the CPU 801. The RAM 803 is used as a work area for the CPU 801. The medium I / F 807 controls reading or writing (storing) of data in a recording medium 806 such as a flash memory.

[0083] The operation unit 808 is provided with various keys, buttons, LEDs, etc., 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 of the size of the projected image, adjustment operations of the color tone, adjustment operations of the focus, and adjustment operations of the trapezoid, and outputs the received operation contents to the CPU 801.

[0084] The power switch 809 is used to switch the power of the image projection device 100 on and off.

[0085] The bus 810 is an address bus and a data bus for electrically connecting various components such as the CPU 801. The network I / F 811 is an interface for data communication using a communication network such as the Internet. The peripheral connection I / F 818 is directly connected to a PC (Personal Computer) to obtain control signals and image data with the PC.

[0086] The light source driving 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 driving circuit 814, light is irradiated from the light source 8 to the image light generating unit 2. The image light generating unit 2 generates image light corresponding to each color based on the image data provided by the external device connection I / F 818, etc. The image light of each color generated by the image light generating unit 2 is projected onto the projection surface through the projection optical system 3. As described above, the light source driving circuit 814, the light source 8, the image light generating unit 2 and the projection optical system 3 as a whole function as a projection unit (projection device), and projects the image light onto the projection surface based on the image data.

[0087] The airflow generating device driving circuit 819 is connected to the CPU 801 and the airflow generating device 16 , and drives and stops the airflow generating device 16 according to a control signal from the CPU 801 .

[0088] After receiving power, the CPU 801 starts according to the control program pre-stored in the ROM 802, provides a control signal to the light source driving circuit 814 to light the light source 8, and provides a control signal to the airflow generating device driving circuit 819 to drive the airflow generating device 16. When the power supply circuit starts to supply power to the image projection device 100, the image light generating unit 2 becomes ready for image display, and then the power supply circuit supplies power to various other components.

[0089] After the power switch 809 is OFF, the image projection device 100 sends a power OFF signal from the power switch 809 to the CPU 801. After detecting the power OFF signal, the CPU 801 provides a control signal to the light source driving circuit 814 to turn off the light source 8. Thereafter, after a predetermined time, the CPU 801 provides a control signal to the airflow generator driving circuit 819 to stop driving the airflow generator 16, and at the same time ends its own control processing, and finally sends a command to the power circuit to stop the supply of power.

[0090] <Focal position change with temperature rise>

[0091] Next reference Fig.14 and Fig.15 , illustrating the change in focus position with increasing temperature.

[0092] Fig.14 is the state before the focus position changes, Fig.15 This is the state after the focus position changes.

[0093] like Fig.14 As shown, after the image light is emitted from the image modulation element 201 of the image light generating unit 202, the output image light passes through a plurality of lenses 213 constituting the projection optical system 203, is magnified and projected onto a projection surface P such as a screen. At this time, the focus position a1 of the image light is adjusted so that it coincides with the projection surface P, so that a good image can be displayed.

[0094] However, as the image projection device operates, heat is generated from heat generating components such as the light source, the temperature inside the device rises, and each component undergoes thermal expansion, thereby changing the optical characteristics of the projection optical system 203 and the like. As a result, Fig.15 As shown in FIG. 1 , the focal position a2 of the image light changes toward the front of the projection plane P (towards the projection optical system 203), and the image quality of the image displayed on the projection plane P is reduced. At this time, depending on the change in the optical characteristics, the same Fig.15 In the opposite case to the example, the focal position a2 of the image light changes toward the inside of the projection surface P (that is, the opposite side to the projection optical system 203).

[0095] This change in the focal position accompanying a temperature rise is more significant when projecting image light having a large light energy, such as a bright image, than when projecting image light having a small light energy, such as a dark image.

[0096] Fig.16 Displays the displacement of the focal position when two image lights A' and B' with different energy levels are projected. Fig.16The horizontal axis in the middle represents the time elapsed from the start of image light projection, and the vertical axis represents the focus displacement when the projection surface is at "0". At this time, the positive square of the vertical axis represents the displacement toward the front of the projection surface, and the negative square represents the displacement toward the inside of the projection surface.

[0097] like Fig.16 As shown in FIG. 1 , when projecting low-energy image light B', although the focus position changes slightly toward the front side as time passes, the displacement is small. Therefore, the focus position is included in the image quality allowable range H. In contrast, when projecting high-energy image light A', the focus position changes greatly, so the focus position deviates from the image quality allowable range H, and the image quality may be significantly reduced.

[0098] In view of this, the present invention proposes the following focus position adjustment method in order to suppress the image quality degradation caused by the focus position change. The focus position adjustment method of the present invention is described below by taking the structure of the first embodiment of the present invention as an example.

[0099] <Focus position adjustment method>

[0100] Figure 3 It is a schematic diagram of a focus position adjustment method according to the first embodiment of the present invention.

[0101] Figure 3 The image light output from the image modulation element 25 of the image light generating unit 2 is projected onto the projection surface P through the plurality of lenses 26 of the projection optical system 3. The lens 26 is an example of an optical component. Figure 3 The focal position a in the figure is the focal position when the image light A with large energy is projected, and the focal position b in the figure is the focal position when the image light B with small energy is projected.

[0102] In the present invention, "high-energy image light A" refers to image light having greater light energy than image light B. That is, the image light projected by the image projection device of the present invention includes at least a first image light (low-energy image light B) having a predetermined light energy and a second image light (high-energy image light A) having a light energy greater than that of the first image light. The high-energy image light A is, for example, image light having a larger average picture level (APL) than the low-energy image light B. In the case where the projected image light is a monochromatic image light, it can be said that the image light A is image light having a larger area ratio of white image light than the low-energy image light B.

[0103] Here, the average image brightness (APL) refers to the value obtained by calculating the sum Ysum of the brightness values ​​Y of each pixel and dividing it by the total number of pixels N, and can be calculated using the following formula: Yave = Ysum / N. There is no particular limitation on the method for calculating the average image brightness (APL). For example, there are methods of calculating based on image information in the image projection device, methods of calculating using a PC or the like based on image data input to the image projection device, and methods of measuring the brightness of each part of the projected image light and averaging it. The area ratio of white image light refers to the ratio of white pixels to the total number of pixels controlled by the image light generating unit 2 when the projected pixels are a monochrome image of either white or black. In this case, white is defined as a state in which the maximum amount of light enters the projection optical system under the control of the image light generating unit 2, and black is defined as a state in which the minimum amount of light enters the projection optical system under the control of the image light generating unit 2.

[0104] like Figure 3 As shown, in the first embodiment of the present invention, the focal position b when the low-energy image light B is projected and the focal position a when the high-energy image light A is projected are adjusted to be located on both sides of the projection surface P. In other words, the focal position a when the high-energy image light A is projected and the focal position b when the low-energy image light B is projected are adjusted so that the projection surface P is located between the focal position a and the focal position b.

[0105] In the first embodiment of the present invention, the focus position a and the focus position b arranged to be located on both sides of the projection surface P are the focus positions when the respective focus positions become stable after the projection of the image light A and the image light B starts. The "stable state" means that the change (rate of change) of the focus position per unit time is less than 1 / 10 of the rate of change (focus moving distance ÷ 60 seconds) after 1 minute has passed from the first image light projection to the second image light projection. The state in which the temperature change (rate of change) per unit time becomes less than 1 / 10 of the rate of change (temperature change amount ÷ 60 seconds) after 1 minute has passed from the first image light projection to the second image light projection can also be regarded as a "stable state".

[0106] Thus, in the first embodiment of the present invention, the focus positions a and b located on both sides of the projection plane P are the focus positions when the respective focus positions become stable. Figure 4 As shown in FIG. 1 , the focus position a and the focus position b in the stable state can be included in the image quality allowable range H. Figure 4Compared with the comparative example shown by the double-dashed line in FIG. 1 , the first embodiment of the present invention can make both the focus position a and the focus position b in the stable state included in the acceptable range H of image quality by moving the focus position in advance to the opposite side of the focus displacement direction (negative direction of the Y axis). In the case of the comparative example, since the focus positions in the stable state when the image light A' and the image light B' are projected are located on the positive side of the Y axis relative to the position of the projection surface P, the focus position in the stable state deviates from the acceptable range H of image quality, especially when the high-energy image light A' is projected. In contrast, in the first embodiment of the present invention, since the focus position b in the stable state when the low-energy image light B is projected and the focus position a in the stable state when the high-energy image light A is projected are arranged to be located on both sides of the projection surface P, each focus position a and the focus position b in the stable state can be included in the acceptable range H of image quality. The deviation amount d of the focus position can be appropriately set according to the deviation amount between the focus position in the stable state and the acceptable range H of image quality when the focus position is not deviated (in the case of the comparative example), and the size of the acceptable range H of image quality.

[0107] Usually, within a period of time after the image light projection starts, the user or the like performs initial settings such as input switching operations. Therefore, the image quality after the focus position turns to a stable state is given priority over the image quality at the beginning of the projection. For this reason, the first embodiment of the present invention adjusts each focus position a and focus position b in a stable state to be located on both sides of the projection surface P. Thus, it is possible to improve the image quality when the user or the like completes the initial settings and each focus position a and focus position b becomes a stable state.

[0108] In the first embodiment of the present invention, when adjusting the focus position, the adjustment range is not limited by the chromatic aberration range or the distortion range because the chromatic aberration of the image light or the distortion of the projected image is not used. Therefore, the focus position can be adjusted according to the change of the focus position. Therefore, according to the adjustment method of the first embodiment of the present invention, even if the deviation of the focus position exceeds the chromatic aberration range or the distortion range, the focus position can be adjusted according to the change of the focus position to improve the image quality.

[0109] The distances between the focus positions a and b and the projection surface P can be set appropriately. Figure 3In the embodiment, the distances La and Lb from the projection surface P to each focal position a and focal position b can be set to half (L / 2) of the distance L between the focal position a and the focal position b. In this case, the image quality when the respective focal positions are in a stable state when projecting high-energy image light A and when projecting low-energy image light B can be made substantially the same. When it is necessary to improve the image quality of the focal position a when projecting high-energy image light A, it is preferred that the distance La between the focal position a and the projection surface P is less than L / 2. On the contrary, when it is necessary to improve the image quality of the focal position b when projecting low-energy image light B, it is preferred that the distance Lb between the focal position b and the projection surface P is less than L / 2.

[0110] In this way, the distances La and Lb between the projection plane P and each focal position a and focal position b can be appropriately changed. However, if the distances La and Lb between the projection plane P and each focal position a and focal position b are too large, the image quality at the focal position with a large distance may be significantly degraded. Therefore, it is preferred that the distances La and Lb between the projection plane P and each focal position a and focal position b are respectively set to be within a range of more than one third and less than two thirds of the distance L between the focal position a and the focal position b (L / 3≤La, Lb≤2L / 3).

[0111] Next, another embodiment of the present invention will be described. The following mainly describes the differences from the first embodiment of the present invention, and the description of the same parts will be omitted.

[0112] [Second embodiment]

[0113] Figure 5 Schematic diagram of the content of the second embodiment of the present invention. Specifically, Figure 5 In the figure, solid lines A and B represent the changes in each focal position when the focus position adjustment method of the second embodiment of the present invention is adopted, and double-dash lines A' and B' represent the changes in each focal position in the comparative example that does not adopt the present invention. Solid line A and double-dash line A' are the changes in each focal position when high-energy image light A and A' are projected, and solid line B and double-dash line B' are the changes in each focal position when low-energy image light B and B' are projected. The contents represented by solid lines A and B and double-dash lines A' and B' are the same in each figure of other embodiments described later.

[0114] like Figure 5 As shown, in this case, after each image light A, image light B, A', B' is projected, each focus position temporarily changes greatly, then the change in the focus position decreases and then enters a stable state. In this way, the focus position changes greatly after the image light projection starts, and then sometimes becomes a stable state.

[0115] In this case, after the high-energy image light A' is projected in the comparative example, the focus position changes greatly, so the focus position deviates from the image quality allowable range H. When the focus position becomes a stable state thereafter, it also deviates from the allowable range H. In contrast, in the second embodiment of the present invention, even when the high-energy image light A is projected, the focus position in the stable state can be included in the image quality allowable range H.

[0116] As described above, in the second embodiment of the present invention, although the focus position in the stable state is included in the permissible range H of the image quality, when the focus position changes the most, the focus position still deviates from the permissible range H of the image quality. However, in a period of time after the start of projection, the user or the like often performs initial settings, and therefore, after the start of projection, the image quality after the focus position turns to the stable state is often preferred over the image quality before the change of the focus position reaches the maximum. For this reason, in the second embodiment of the present invention, it is necessary to give priority to the image quality after the focus position turns to the stable state so that the focus position in the stable state is included in the permissible range H.

[0117] In addition, in the second embodiment of the present invention, in order to ensure the image quality in two stable states when projecting high-energy image light A and low-energy image light B, the focus position a and the focus position b in the stable state of each case are arranged to be located on both sides of the projection surface P. Figure 5 Compared with the comparative example shown by the double dotted line in , the focus position can be moved in advance to the opposite side of the focus displacement direction (the negative direction of the Y axis) so that each focus position a and focus position b in the stable state are included in the allowable range H of image quality.

[0118] [Third Embodiment]

[0119] then, Figure 6 The contents of the third embodiment of the present invention are shown.

[0120] exist Figure 6 In the third embodiment of the present invention shown in FIG. Figure 5 The same as the second embodiment of the present invention shown, the focus position temporarily changes greatly, but when the change is the largest, each focus position a and focus position b is included in the allowable range H of image quality.

[0121] Depending on the configuration of the image projection device, it may take a long time for the focus position to become stable after the maximum displacement. In this case, the image quality degradation before the focus position becomes stable may become a burden for the user. Therefore, in the third embodiment of the present invention, in order to ensure good image quality when the focus position becomes the maximum displacement, the image light A and the image light B are adjusted after the projection starts, so that each focus position a and the focus position b are configured to be located on both sides of the projection surface P when the change becomes the maximum. Thus, since each focus position a and the focus position b are included in the permissible range H of the image quality at the maximum displacement, the image quality when each focus position is the maximum displacement can be improved.

[0122] [Fourth Embodiment]

[0123] then, Figure 7 It is a schematic diagram showing the contents of the fourth embodiment of the present invention.

[0124] exist Figure 7 In the fourth embodiment of the present invention shown, after the high-energy image light A is projected, it is switched to projecting the low-energy image light B. In this case, the focus position is first greatly changed temporarily due to the projection of the high-energy image light A, and then turns to a stable state. Next, after switching to the low-energy image light B, the focus position is greatly displaced in the direction opposite to the displacement direction when the high-energy image light A is projected, and then turns to a stable state. Since the image quality may also be greatly reduced when the focus position changes to the maximum, it is best if possible that the image quality is within the allowable range when the focus position changes to the maximum.

[0125] Therefore, in the fourth embodiment of the present invention, the focus position a when the change is the largest when the image light A is projected, and the focus position b when the change is the largest when the image light B is projected are arranged to be located on both sides of the projection surface P. In this way, since the focus positions a and b at the time of the maximum displacement are included in the permissible range H of the image quality, the image quality can be improved.

[0126] <Regarding the relationship between the focal position and the permissible range of image quality>

[0127] The above embodiments take the projection of two types of image light, high energy image light A and low energy image light B, as examples to illustrate the respective focal positions. However, in general, the image projection device is not limited to the above two types of image light, but can project various image lights with different light energy levels. Moreover, the form of the change of the focal position of these image lights is different according to the light energy level of each image light.

[0128] Figure 8 It is a schematic diagram of the changes in the focal position of various image lights with different light energy levels.

[0129] In this case, the average picture brightness (APL) is used to define the light energy of each image light. Specifically, Figure 8 The image average brightness of the image light is set to approximately 0%, 30%, 50%, 70%, and approximately 100%, and the focus position changes when the image light is projected. The image average brightness is not "0%" or "100%", but "approximately 0%" or "approximately 100%". This is because when it is completely set to "0%" or "100%", the entire image is black or white, and the focus position cannot be adjusted.

[0130] like Figure 8 As shown, when the average brightness of the image is approximately 0%, the focus position hardly changes. However, as the average brightness of the image reaches 30%, 50%, 70%, and approximately 100%, the focus position changes significantly. At the same time, the time it takes for the focus position to reach the maximum displacement and the time it takes to turn to a stable state are shortened.

[0131] Here, in order to ensure good image quality, it is preferred that the focus position after the image is in a stable state is included in the image quality allowable range H. Although it is ideal that the focus position is included in the image quality allowable range H in the stable state for all image lights with an image average brightness of 0% to 100%, it is difficult to meet this condition in reality. Therefore, it is preferred to determine the range of the focus position included in the image quality allowable range H according to the actual usage form.

[0132] In this regard, it can be seen from the actual usage state that the image light with an average image brightness of 30% or more and 70% or less is used more frequently. Therefore, it can be said that the focus position in the stable state when projecting image light with an average image brightness of at least 30% or more and 70% or less is preferably included in the image quality allowable range H. Therefore, if Figure 8 As shown, it is preferred to adjust the focus position b of the image light with an average image brightness of 30% in a stable state and the focus position a of the image light with an average image brightness of 70% in a stable state to both sides of the projection surface P so that the focus position b and the focus position a are included in the permissible range H of the image quality. It is also possible to adjust the focus position when the displacement amount is the largest in the image light with an average image brightness of 30% and the focus position when the displacement amount is the largest in the image light with an average image brightness of 70% to both sides of the projection surface P so that both focus positions are included in the permissible range H of the image quality. The two types of image light whose focus positions a and b are adjusted are not limited to image light with an average image brightness of 30% and 70%, and can be set arbitrarily as long as the average image brightness is greater than 30% and less than 70%.

[0133] In addition to the average brightness of the image of the small-energy first image light being more than 30% and the average brightness of the large-energy second image light being less than 70%, how to select the two image lights can be appropriately changed according to image quality requirements, etc.

[0134] For example, among two image lights with different light energy levels, the first image light can be regarded as image light having light energy less than 50% of the light with the maximum energy that can be emitted by the light source, and the second image light can be regarded as image light having light energy greater than 50% of the light with the maximum energy that can be emitted by the light source.

[0135] The first image light may be image light that includes an evaluation chart for evaluating image quality or focus position in an image with a black background in an emission mode of the darkest light that can be emitted by the light source, and the second image light may be image light that includes an evaluation chart for evaluating image quality or focus position in an image with a white background in an output mode of the brightest light that can be emitted by the light source.

[0136] Furthermore, the first image light may be image light having light energy less than one tenth of that of the second image light.

[0137] <Focus Position Adjustment Device>

[0138] Next, the focus position adjustment device will be described.

[0139] Regarding the method of adjusting the focal position, there is a method of changing a part of the lens 26 of the projection optical system 3 (see Figure 3 ), changing the position of the lenses 26, or changing the spacing between the lenses 26, or changing the spacing between the lenses 26 and the image modulation element 25. In addition, the positions of all the lenses 26 of the projection optical system 3 may be changed, or the positions of the lenses 26 except the lenses 26 at the two ends may be changed without changing the positions of the lenses 26 at the two ends.

[0140] When the image modulation element 25 is fixed to the housing and the projection optical system 3 is mounted on the housing or a bracket connected to the housing, a spacer component may be provided between the bracket and the projection optical system 3 or between the bracket and the housing to adjust the interval between the projection optical system 3 and the image modulation element 25. If the displacement amount of the focal position is determined in advance, the focal position can be easily adjusted by interposing the spacer component.

[0141] In order to adjust the focal position, the distance between the bracket and the projection optical system 3, or between the bracket and the housing, may be changed. For example, the distance between the bracket and the projection optical system 3, or between the bracket and the housing, may be changed by changing the amount of pressure of a spring member held therebetween. In this case, since the amount of displacement of the focal position can be adjusted by changing the angle of rotation of a screw for adjusting the amount of pressure of the spring member, more precise adjustment can be performed compared to the method using a shim member.

[0142] If the image modulator 25 is movable, the image modulator 25 may be moved to change the distance between the projection optical system 3 and the image modulator 25. In this case, since the object to be moved is the image modulator 25 which is lighter than the projection optical system 3, the adjustment operation can be easily performed.

[0143] As another method of adjusting the focal position, there is a method of deforming a component between the image modulation element 25 and the projection optical system 3 by heat. For example, a housing between the image modulation element 25 and the projection optical system 3 can be heated by a heater to thermally expand the housing, thereby changing the distance between the image modulation element 25 and the projection optical system 3. If a heater is used, the housing can be thermally expanded quantitatively, so that the focal position can be adjusted with high precision.

[0144] The heat generated in the image projection device may be used to heat the housing, etc. instead of the heater. For example, when the image modulation element 25 generates image light, if the image light is irradiated on a component other than the projection optical system 3 (for example, a light cutoff plate, etc.), heat is generated, and therefore, the heat can be used as heat for heating the housing, etc. The heat generated by the light source may also be used as heat for heating the housing, etc. These methods can reduce power consumption compared to using a heater, and thus can save energy. Furthermore, by using a temperature sensor or a strain gauge to control the amount of thermal expansion of the housing, etc., the focus position can be adjusted with higher precision.

[0145] like Fig. 9 As shown, in order to easily adjust the focus position, the third image light C having the focus position c may be projected between the two focus positions a and b to be adjusted. For example, in the case of monochromatic image light, if the image light having a black ratio of 90% or more is used as the first image light and the image light having a white ratio of 90% or more is used as the second image light, the third image light may be used as the image light having a white or black ratio of 35% or more and 65% or less. In addition, if the first image light is used as the image light having an image average brightness of 30% and the second image light is used as the image light having an image average brightness of 70%, the third image light may be used as the image light having an image average brightness of 40% or more and 70% or less.

[0146] By projecting such a third image light by a user or the like, the focus position c at this time is adjusted to coincide with the projection surface P, so that the focus position a of the image light having a greater light energy than the third image light and the focus position b of the image light having a smaller light energy than the third image light are adjusted to be located on both sides of the projection surface P. Fig. 9 In the example shown, the focal position c of the third image light C adjusted to coincide with the projection plane P is taken as the focal position in a stable state, but the focal position c can be set arbitrarily.

[0147] In addition, the third image light C may be set to an image light having an average image brightness of about 50%, and the average image brightness 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 average image brightness, the average image brightness of the third image light C may be changed to 70% in the case of the presentation mode. On the other hand, since the image light when projecting movies or other images often has a relatively low average image brightness, the average image brightness of the third image light C may be changed to 30% in the case of the movie mode or the theater mode. In this way, by arbitrarily changing the average image brightness of the third image light C according to the projection mode of the image projection device, good image quality can be ensured.

[0148] The third image light may be an image light including an evaluation chart for evaluating image quality or focus position. In this case, the user can adjust the focus position while visually viewing the evaluation chart to improve the image quality of the evaluation chart, so that the focus position can be easily adjusted. The evaluation chart may be a symbol or a graphic in addition to text such as letters and numbers, as long as the image quality can be visually confirmed.

[0149] Evaluation charts are as follows Fig.10 As shown in FIG. 1 , in the case where the projection surface P is divided into a plurality of areas u1 to u13 in a matrix shape, the evaluation chart can be projected onto at least one area. By projecting the evaluation chart onto any area of ​​the projection surface P and adjusting the focus position of the evaluation chart to be consistent with the projection area, the focus positions a and b of the first image light and the second image light can be arranged as follows: Fig.11 shown.

[0150] Fig.11 The focus position a and the focus position b of the first image light and the second image light in each of the plurality of regions u1 to u13 that partition the projection surface P are displayed. Fig.11 The middle white dot is the focus position b of the first image light with small light energy, and the black dot is the focus position a of the second image light with large light energy. In the area u8, since the focus position a and the focus position b cannot be measured, the white dot and the black dot are not displayed. In this way, if the evaluation chart included in the third image light C is used, the focus positions a and b of the first image light and the second image light can be adjusted so that they are located on both sides of the projection surface P.

[0151] If the projection surface P is large or somewhat curved, it may not be possible to make the focus positions of the evaluation chart consistent in all the areas u1 to u13 of the projection surface P. In this case, for example, the focus positions of the evaluation charts can be made consistent in the central area u5, and then the focus positions of the evaluation charts can be made consistent in the upper areas u1, u2, u3, u10, u11, etc. by a mechanism that changes the size of the projected image.

[0152] <Focus adjustment mechanism>

[0153] Next, the structure of the focus adjustment mechanism included in the image projection device of the present invention will be described.

[0154] Fig.12 Schematic diagram of an example of the focus adjustment mechanism 400.

[0155] like Fig.12 As shown, 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 driving unit 405 .

[0156] The interface unit 401 obtains information output from an information processing device 300 such as a personal computer that outputs image information or a memory that stores image information. The processing unit 402 is used to process the image information input from the interface unit 401. The recording unit 403 stores image information for intersection adjustment. The 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 that are adjustment objects, or an evaluation chart contained therein. The image projection unit 404 is used to generate image light based on the image information input from the processing unit 402 and project it. Figure 2 The image generating unit 2 and the projection optical system 3 shown are constituted.

[0157] The focus driving unit 405 is used to move part or all of the multiple lenses of the projection optical system 3 of the image projection unit 404 in the axial direction of the projection light, so that the focus of the image light (third image light C) for focus adjustment at the required projection position on the projection surface is consistent with the projection surface P, or the focus of the first image light and the second image light for focus adjustment are respectively located on both sides of the projection surface. Fig.12 In the example shown in FIG. 4 , the focus driving unit 405 and the lens of the projection optical system 3 are connected via the focus connecting unit 406 . However, the focus driving unit 405 may be included in the image projection unit 404 .

[0158] The image projection device 100 is provided with the above-mentioned focus adjustment mechanism 400 to facilitate the adjustment of the focus position. The focus position adjustment of the focus adjustment mechanism 400 can be performed automatically or manually. In the case of manual adjustment, the focus drive unit 405 is not required, and it is sufficient to provide a device for detecting the focus position adjustment operation, or a device for detecting that the focus position adjustment operation has been performed. A device for detecting whether the focus adjustment mode is selected can also be used as a detection device. In the case of automatic focus position adjustment, by detecting the selection of the focus adjustment mode, image light for focus adjustment is projected from the image projection unit 404 based on the image information stored in the recording unit 403.

[0159] <Flow of adjusting the focus position>

[0160] Fig.13 This is a flow chart of the focus position adjustment performed by the focus adjustment mechanism 400 .

[0161] like Fig.13 As shown, the processing unit 402 detects the focus adjustment mode, determines whether the focus adjustment mode is ON (S1), and when it is determined that the focus adjustment mode is ON, reads the information of the image light projected during the focus adjustment from the recording unit 403 and inputs it to the processing unit 402 (S2). For example, when the user starts the focus adjustment operation using a remote controller, the detection device detects the signal sent by the remote controller or the device, so that it can be confirmed that the focus adjustment mode has become ON. When the processing unit 402 reads the image information for focus adjustment, the processing unit 402 switches the image information from the information processing device 300 input before to the image information for focus adjustment (S4). Then, the image projection unit 404 generates and projects the image light based on the image information for focus adjustment input from the processing unit 402 (S5). As a result, the image for focus adjustment is displayed on the projection surface, so that the user adjusts the focus position while visually viewing the projected image so that the focus of the image coincides with the projection surface (S6).

[0162] On the other hand, when the image adjustment mode is not detected to be turned on, the processing unit 402 reads the image information from the information processing device 300 and executes the projection mode based on the image information (external input image) ( S3 ).

[0163] As described above, when the image adjustment mode is detected to be turned on, by adjusting the focus position based on the image for focus adjustment, the focus positions a and b of the first image light and the second image light of different light energy can be adjusted to be located on both sides of the projection surface P. The user can automatically adjust the focus position according to the focus adjustment image displayed on the projection surface, so it is easy to adjust the focus position. In addition, in addition to manually adjusting the focus position while visually viewing the focus adjustment image projected on the projection surface, the projection image can also be arranged to automatically adjust the contrast to be optimal.

[0164] <Focus adjustment image example>

[0165] Use here Figures 17 to 20 A focus adjustment image used when a user adjusts the focus of an image projection device or when an assembler in a manufacturing process adjusts the focus of an image projection device is described.

[0166] Fig.17 FIG. 1 is a schematic diagram showing an example of the configuration of an evaluation chart included in an image for focus adjustment. Fig.17 In the example of , the projection plane P is divided into nine equal matrix-shaped areas u1 to u9.

[0167] In the manufacturing process of the image projection device, in order to ensure the required projection image quality, generally, a plurality of evaluation charts of focus adjustment images are projected on the projection surface so that the focus position of the entire projection surface area can be adjusted. Fig.17 The evaluation charts are projected onto the centers o1 to o9 of the nine areas U1 to u9 respectively, and the assembly adjustment of the parts is performed to align the focus of each evaluation chart and perform the inspection process.

[0168] On the other hand, when the user adjusts the focus of the image projection device, if many evaluation charts are projected on the projection surface P, the user will often feel confused about which evaluation chart to focus on for adjustment. If the image projection device is adjusted to a certain quality in the manufacturing process, the user does not necessarily need to perform the same degree of focus adjustment work as in the manufacturing process when adjusting the focus. When the user adjusts the focus, it is hoped that the focus adjustment work is as simple as possible and the projected focus adjustment image is as simple as possible.

[0169] Therefore, when the user performs focus adjustment, it is preferred that the evaluation chart is not projected onto the centers o1 to o9 of all nine areas U1 to u9 as in the manufacturing process, but rather projected onto the centers o1 to o9 of all nine areas U1 to u9 as in the manufacturing process. Fig.17In the example of , the evaluation chart 90 is projected to a total of five locations near the center o5 of the projection surface P and the four corners c1 to c4. In this way, by projecting the evaluation chart 90 to the center o5 of the projection surface P and the four corners c1 to c4, the resolution performance of the center and the periphery of the projection surface P can be ensured, and a certain projection image quality can be ensured. Since there are only five projection positions of the evaluation chart 90, the viewpoint movement is also minimized, so the device is also easy to operate for the user. Since the total area of ​​the evaluation chart 90 can be minimized, when determining the average image brightness (APL) of the background part without the evaluation chart 90, the evaluation chart 90 itself does not need to be the value of the determined average image brightness (APL), so the difference between the value of the determined average image brightness (APL) and the value of the actual average image brightness (APL) including a plurality of evaluation charts 90 can be reduced. Therefore, the projection position of the evaluation chart 90 is preferably about five locations in the center of the projection surface P and its periphery.

[0170] Specifically, the evaluation chart 90 is preferably arranged at the center o5 of the projection plane P, and 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 plane 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 plane 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. The evaluation chart 90 projected near the four corners c1 to c4 may also be arranged at positions between the centers o1, o3, o7, o9 of the regions u1, u3, u7, u9 including the four corners c1 to c4 and the positions e1, e3, e7, e9 close to the corners ( Fig.17 Evaluation chart location as shown).

[0171] In this way, by selecting the center o5 of the projection surface P and the positions near the four corners c1 to c4 (including the positions between the centers o1, o3, o7, o9 of the areas u1, u3, u7, u9 of the four corners c1 to c4 and the corners c1 to c4) as the projection positions of the evaluation chart 90, the focus can be adjusted while observing the balance of the projection image at the center o5 where the quality of the projection image is most obvious and near the four corners c1 to c4 where the focus is most strictly required.

[0172] In addition, when the user performs focus adjustment, in order to select a mode for projecting the evaluation chart at the above five locations, it is preferable to pre-set a simple mode different from the focus adjustment mode in the manufacturing process. In addition, since the user wants to perform more detailed focus adjustment, in this case, a plurality of detailed modes capable of projecting the evaluation chart at more than five locations may be pre-set, and a preferred mode may be selected according to the purpose of the image projection device. In addition, when the person who installs the device or performs service performs focus adjustment, a focus adjustment image of a service mode capable of projecting the evaluation chart at more than five locations may be prepared.

[0173] Fig.18 It is a schematic diagram of another embodiment of an image for focus adjustment.

[0174] exist Fig.18 In the example of (a), the evaluation chart 90 of the focus image is displayed as black cross lines (horizontal and vertical cross shapes) on a white background. Here, the evaluation chart 90 is projected at five positions, namely the center o and four corners c1 to c4 of the projection surface P. The background portion 91 other than the evaluation chart 90 in the focus adjustment image becomes a pattern in which the average image brightness (APL) is adjusted to, for example, 50% of the desired value. That is, the grayscale is selected so that the brightness of the output image becomes an intermediate grayscale image with 50% intensity relative to white. Specifically, in the case of γ=2.2 described later, when the grayscale is set to 256, if the grayscale value is appropriately set (for example, to about 186), the output value is approximately 50%, and an image equivalent to 50% of the average image brightness (APL) can be obtained.

[0175] Then, in Fig.18 In the example (b), the evaluation chart 90 is displayed as a pair of black double intersecting lines (vertical and horizontal cross shapes) on a white background. The background portion 91 of the focus adjustment image other than the evaluation chart 90 is a pattern in which the image average brightness (APL) is adjusted to a desired value such as 50%. Fig.18 In (b), the background portion 91 appears to be displayed in gray, but the background portion 91 is enlarged in units of pixels (see Fig.18 In other words, in this case, for each pixel, one of the two values ​​of full white or full black is projected at a ratio of 1:1, and the average brightness (APL) of the image is determined by the ratio of the number of white pixels to the number of black pixels.

[0176] Fig.19 is a schematic diagram of another embodiment of an evaluation chart.

[0177] Fig.19 The examples of evaluation charts shown are particularly examples of various evaluation charts used when the user performs focus adjustment (simple mode). Fig.19As shown, in addition to setting the color of the cross-line part of the evaluation chart to white or black, and the cross-line part to be composed of a single line or multiple lines, the color of the background part of the evaluation chart can also be set to black or white, and various combinations can be selected.

[0178] When the user makes a focus adjustment, in order to facilitate the process, the line width of the evaluation chart, which is equivalent to the number of pixels, can be set to be larger than the pixel unit of the image modulation element (bold resolution). If the line width of the evaluation chart is the same as the pixel unit (image resolution performance) of the image modulation element, the focus sensitivity becomes higher and it is difficult for the user to adjust. Therefore, it is preferred to use a plurality of continuous black and white pairs of lines. In this way, by setting the line width of the evaluation chart to 2 or 3 times the image resolution performance of the panel, it is convenient for the user to adjust the focus. When the assembly operator or service personnel in the manufacturing process makes a focus adjustment, it is not limited to this, and it is suitable to use an evaluation chart composed of lines or text represented by the pixel unit of the image modulation element.

[0179] Fig. 20 FIG. 1 is a schematic diagram of another embodiment of the background portion of an image for focus adjustment.

[0180] Fig. 20 (a) shows an example of a background portion 91 with an average image brightness (APL) of 50%, (b) shows an example of a background portion 91 with an average image brightness (APL) of 60%, and (c) shows an example of a background portion 91 with an average image brightness (APL) of 80%. In this way, by setting each pixel to a white pixel or a black pixel, the image average brightness (APL) can be correctly determined. In the case of gray display, since the image average brightness (APL) depends on the ability of grayscale reproducibility, it is impossible to determine the correct image average brightness (APL). This is because multiple gamma curves can be selected. For example, in the case of an image projection device that can be displayed with 256 grayscale levels from black 0 to white 255, the brightness information of the input signal and the displayed grayscale level value are mostly not linear, and are mostly downward convex exponential functions, which have multiple functions (called so-called gamma curves). The relationship between the input value x and the output value y in the gamma curve is represented by y=x γ The exponential part of the image can generally take a value of about γ = 2, γ = 0, or γ = 2.2. Most image projection devices have multiple image display modes. Even if a grayscale value is selected to display 50% gray, the grayscale value will change according to the value of γ, so the correct image average brightness (APL) cannot be determined. This method of determining the image average brightness (APL) that does not depend on γ is to define the image average brightness (APL) by the ratio of the number of black and white pixels, thereby obtaining a background image with a correct image average brightness (APL).

[0181] Used above Figures 17 to 20 The focus adjustment image and evaluation chart during focus adjustment are described, but the focus adjustment image can be an image projected based on image information pre-stored in the image projection device, or an image projected based on image information input from an external device to the image projection device.

[0182] In addition, the image projection device of the present invention is not limited to the above-mentioned embodiment.

[0183] For example, in addition to an image projection device that projects image light onto a flat surface such as a screen, the present invention can also be used for an image projection device that projects image light onto a three-dimensional structure such as a vehicle body or a building. Therefore, the present invention does not need to adjust the positions of the focus position a and the focus position b of the first image light and the second image light to be adjusted to both sides of the entire projection surface P. For example, when the projection surface is a concave and convex surface, and the distance from the image projection device to the projection surface varies greatly depending on the parts of the projection surface, at least a part of the projection surface can be adjusted to be located between the focus position a and the focus position b of the first image light and the second image light, respectively.

[0184] The image projection device of the present invention can be used for business (projection display for business, conference, demonstration, etc.), home use, medical use (projection display of monochrome medical images such as X-ray images and MRI (Magnetic Resonance Imaging) images), public use (projection display of various guides, advertisements, signs, etc. in public places, stores, and transportation vehicles), factory installation, etc. The image projection device of the present invention has projection modes corresponding to their respective uses (color mode, animation mode, image mode, medical mode for projecting medical images, public mode for projecting guides or signs outdoors or in stores, etc.), and can also automatically change the driving method and driving amount control of the light source, power, cooling, output, etc. according to the change of mode.

[0185] The present invention can be summarized as including at least the following aspects.

[0186] <1> An image projection device, comprising:

[0187] light source;

[0188] an image light generating unit, configured to receive the light emitted from the light source and generate image light; and

[0189] a projection optical system that projects the image light generated by the image light generating unit onto a projection surface,

[0190] The image projection device is configured so that a focal position when projecting a first image light having a predetermined light energy and a focal position when projecting a second image light having a light energy greater than that of the first image light are respectively located on both sides of at least a portion of the projection surface.

[0191] <2> The image projection device according to claim 1, wherein there is a device for moving the optical elements of the projection optical system, so that the focal position when the first image light with a specified light energy is projected and the focal position when the second image light with a light energy greater than that of the first image light is projected are respectively located on both sides of at least a portion of the projection surface.

[0192] <3> exist <1> In the aspect, each of the focus positions arranged on both sides of at least a portion of the projection surface is a focus position when the focus positions each become a stable state after the projection of the first image light and the second image light starts.

[0193] <4> exist <1> In the aspect, each of the focal positions arranged on both sides of at least a portion of the projection surface is a focal position when the temperature of the projection optical system becomes stable after the projection of the first image light and the second image light starts.

[0194] <5> exist <1> In the aspect, the focus positions arranged on both sides of at least a portion of the projection surface are focus positions at which changes in the focus positions are maximum after the projection of the first image light and the second image light starts.

[0195] <6> exist <1> to <5> In any aspect of the invention, when the distance between the focal positions arranged on both sides of at least a portion of the projection surface is set to 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, the following relationship is satisfied: L / 3≤La, Lb≤2L / 3.

[0196] <7> exist <1> to <6> In any aspect of the present invention, the image average brightness of the first image light is smaller than the image average brightness of the second image light.

[0197] <8> exist <1> to <7> In any one aspect of the present invention, the first image light is a monochromatic image light in which the area ratio of the white image light is smaller than that of the second image light.

[0198] <9> exist <1> to <8> In any aspect of the present invention, the first image light is image light having a light energy less than 50% of the light with a maximum energy that can be emitted by the light source, and the second image light is image light having a light energy greater than 50% of the light with the maximum energy.

[0199] <10> exist <1> to <9> In any one aspect of the invention, the first image light is image light that includes an evaluation chart for evaluating image quality or focus position in an image with a black background in an emission mode of the darkest light that the light source can emit, and the second image light is image light that includes an evaluation chart for evaluating image quality or focus position in an image with a white background in an output mode of the brightest light that the light source can output.

[0200] <11> exist <1> to <10> In any aspect of the present invention, the light energy of the first image light is less than one tenth of the light energy of the second image light.

[0201] <12> exist <1> to <11> In any one aspect of the invention, a third image light can be projected, the third image light having a focal position between the focal positions respectively arranged on both sides of at least a portion of the projection surface.

[0202] <13> exist <12> In the aspect of , the third image light is image light including an evaluation chart for evaluating image quality or focus position.

[0203] <14> exist <12> or <13> In the aspect, there is a focus adjustment mechanism for moving at least one lens of the projection optical system when projecting the third image light.

Claims

1. An image projection device, comprising: light source; an image light generating unit, configured to receive the light emitted from the light source and generate image light; and a projection optical system that projects the image light generated by the image light generating unit onto a projection surface, It is characterized in that The focal position when a first image light having a predetermined light energy is projected and the focal position when a second image light having a light energy greater than that of the first image light is projected are respectively located on both sides of at least a portion of the projection surface.

2. The image projection device according to claim 1, further comprising a device for moving the optical elements of the projection optical system so that the focal position when projecting a first image light having a specified light energy and the focal position when projecting a second image light having a light energy greater than that of the first image light are respectively located on both sides of at least a portion of the projection surface.

3. The image projection device according to claim 1, wherein: The focal positions arranged to be located on both sides of at least a portion of the projection surface are focal positions when the focal positions are each in a stable state after the projection of the first image light and the second image light starts.

4. The image projection device according to claim 1, wherein: The focal positions arranged to be located on both sides of at least a portion of the projection surface are focal positions when the temperature of the projection optical system becomes stable after the projection of the first image light and the second image light starts.

5. The image projection apparatus according to claim 1, wherein: The focus positions arranged to be located on both sides of at least a portion of the projection surface are focus positions at which changes in the focus positions are maximum after the projection of the first image light and the second image light begins.

6. The image projection apparatus according to claim 1, wherein: When the distance between the focal positions configured to be located on both sides of at least a portion of the projection surface is set to 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, the following relationship is satisfied: L / 3≤La, Lb≤2L / 3.

7. The image projection apparatus according to claim 1, wherein: The image average brightness of the first image light is smaller than the image average brightness of the second image light.

8. The image projection apparatus according to claim 1, wherein: The first image light is monochromatic image light in which the area ratio of white image light is smaller than that of the second image light.

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

10. The image projection apparatus according to claim 1, wherein: The first image light is image light that includes an evaluation chart for evaluating image quality or focus position in an image with a black background under an emission mode of the darkest light that the light source can emit, and the second image light is image light that includes an evaluation chart for evaluating image quality or focus position in an image with a white background under an output mode of the brightest light that the light source can output.

11. The image projection apparatus according to claim 1, wherein: The light energy of the first image light is less than one tenth of the light energy of the second image light.

12. The image projection apparatus according to claim 1, wherein: A third image light can be projected, the third image light having a focal position between the focal positions configured to be located on both sides of at least a portion of the projection surface.

13. The image projection apparatus according to claim 12, wherein: The third image light is image light including an evaluation chart for evaluating image quality or focus position.

14. The image projection device according to claim 12 or 13, wherein: A focus adjustment mechanism is provided for moving at least one lens of the projection optical system when projecting the third image light.

Images