Image projection apparatus, image projection method, and computer program product

Abstract

The invention relates to an image projection device, an image projection method and a computer program product, and aims to solve the problems that the structure of the image projection device is complex, and focusing offset is difficult to recognize. The image projection apparatus includes an acquisition unit that acquires image data, a classification unit that classifies a type of an image represented by the image data acquired by the acquisition unit, and a detection unit that detects whether or not the type classified by the classification unit changes. And a switching unit that switches the gamma curve applied to the image data to a gamma curve corresponding to the type of the image represented by the image data when the detection unit detects that the type has changed.

Description

Technical Field

[0001] The invention relates to an image projection device, an image projection method and a computer program product. Background Art

[0002] The lens of the projection optical system mounted on the image projection device (projector) will expand or contract to some extent as the temperature changes, although the degree varies. The expansion or contraction of the lens of this projection optical system is particularly significant in an optical system that uses a shortened focal length reflector. That is, when projecting a bright image, the lens that constitutes the projection optical system (the lens and the reflector when a reflector is used) will become hot due to the large amount of transmitted light, causing the lens (the lens and the reflector when a reflector is used) to expand. On the other hand, when projecting a dark image, the amount of transmitted light is small, so the expansion of the lens of the projection optical system (the lens and the reflector when a reflector is used) is suppressed, and contraction occurs compared to when it expands. In this way, when the lens expands or contracts with temperature changes, the focal length changes. This phenomenon is called temperature drift (hereinafter referred to as drift). Due to this drift, the focal position of the lens changes, and the image projected on the screen is recognized as a focus shift.

[0003] Although this drift is sometimes taken into account in the design of optical systems, it is very difficult to completely eliminate the drift within the range of lens use. Although optical designers try to minimize this drift in their designs, controlling it to a level that can be completely ignored requires a very expensive lens structure, which is not suitable as a lens for the projection optical system of a general-purpose projector. Therefore, the actual situation is that a certain degree of drift has to be allowed in the lens design. In addition, the adjustment of the manufacturing process also needs to be simple, which requires a simplified lens system design.

[0004] In response to the above-mentioned focus deviation, prior art such as Patent Document 1 (Japanese Patent Application Publication No. 2006-313201) discloses a technical solution, which uses a camera to capture the image projected onto the screen by the projector, detects the focus deviation, feeds the result back to the projector, controls the electric focus on the projector, and stably maintains the focus quality of the image projected onto the screen.

[0005] However, the technical solution disclosed in Patent Document 1 requires that an electric focusing mechanism and a camera device for a screen be mounted on the projection optical system, which has the problem of being complex in structure and correspondingly expensive. Summary of the invention

[0006] An object of the present invention is to provide an image projection device, an image projection method and a computer program product which can improve the complexity of the structure and make the focus deviation difficult to identify.

[0007] In order to solve the above-mentioned problems and achieve the purpose of the present invention, the present invention provides an image projection device for projecting images using a projection optical system, which comprises: an acquisition unit for acquiring image data; a classification unit for classifying the type of image represented by the image data acquired by the acquisition unit; a detection unit for detecting whether the type classified by the classification unit has changed; and a switching unit for switching the gamma curve applied to the image data to a gamma curve corresponding to the type of image represented by the image data when the detection unit detects that the type has changed.

[0008] The effect of the present invention is to improve the complexity of the structure and make the focus offset difficult to be identified. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram of an overall structure of an example of an image projection device involved in an embodiment.

[0010] Figure 2 It is a top view of an example of a lighting device of the image projection device according to the embodiment.

[0011] Figure 3 This is a block diagram showing an example of the hardware configuration of the image projection device according to the embodiment.

[0012] Figure 4 This is a functional block diagram of an example of the image projection device according to the embodiment.

[0013] Figure 5 This is an example of a continuous image frequency characteristic diagram.

[0014] Figure 6 This is an example of a discrete image frequency characteristic diagram.

[0015] Figure 7 This is an example of a gamma curve graph.

[0016] Figure 8 This is an example of an operation flow chart of the image projection device according to the embodiment.

[0017] Explanation of symbols

[0018] 10 Image projection device

[0019] 11 Shell

[0020] 12 lighting fixtures

[0021] 13 points stick

[0022] 14 Illumination optical system

[0023] 15DMD

[0024] 16 Projection optical system

[0025] 101a, 101bLED light source

[0026] 102a, 102b collimating lens

[0027] 103a, 103b light source optical system

[0028] 104a, 104b light focusing element

[0029] 105a, 105b micro lens array

[0030] 106a, 106b dichroic mirror

[0031] 107a, 107b first focusing optical system

[0032] 108a, 108b fluorescent wheel

[0033] 109a, 109b second focusing optical system

[0034] 110 Prism

[0035] 110A reflective surface

[0036] 110B transmission surface

[0037] 111 Color Wheel

[0038] 201 Acquisition Department

[0039] 202 Feature extraction unit

[0040] 203 Image type determination unit

[0041] 204 brightness determination unit

[0042] 205 Image Classification Department

[0043] 206 Image Change Detection Unit

[0044] 207 Gamma curve switching unit

[0045] 208 Projection Control Department

[0046] 209 Storage Department

[0047] 801CPU

[0048] 802ROM

[0049] 803RAM

[0050] 806 Medium

[0051] 807 Media I / F

[0052] 808 Operation Department

[0053] 809 power switch

[0054] 810 bus

[0055] 811 Network I / F

[0056] 814LED drive circuit

[0057] 818 peripheral connection I / F

[0058] 819 fan drive circuit

[0059] 820 Cooling Fan

[0060] F1, F2 light

[0061] GC1~GC3 gamma curve

[0062] LS1 first light source unit

[0063] LS2 second light source unit

[0064] W Projection surface DETAILED DESCRIPTION

[0065] The following describes in detail the embodiments of the image projection device, image projection method and computer program product of the present invention with reference to the accompanying drawings. The present invention is not limited to the following embodiments, and the constituent elements in the following embodiments include elements that are obvious to those skilled in the art, are substantially the same, and belong to the so-called equivalent scope. In addition, various omissions, substitutions, changes and combinations of constituent elements can be made within the scope of the following embodiments without departing from the purpose.

[0066] <Overview of Image Projection Device Configuration>

[0067] Figure 1 It is a schematic diagram of an overall structure of an example of an image projection device according to an embodiment. Figure 2 Schematic diagram of an illumination device for an image projection device according to an embodiment of the present invention. Figure 1 and Figure 2 , the structure of the image projection device 10 of this embodiment is described. Figure 1 and Figure 2 In the figure, the X direction, the Y direction and the Z direction are orthogonal to each other, the X direction and the Y direction are horizontal directions, and the Z direction is a vertical direction.

[0068] Figure 1The image projection device 10 shown is a device that projects an image represented by image data such as animation or still images onto a projection surface W. The image projection device 10 includes an illumination device 12, an integrator rod 13, an illumination optical system 14, a DMD (Digital Micromirror Device) 15, and a projection optical system 16 in a housing 11.

[0069] The lighting device 12 is a device for irradiating illumination light. The structure of the lighting device 12 will be described in detail below.

[0070] The integrator rod 13 is a rod-shaped glass element, and is an optical element that homogenizes the illumination light incident from the illumination device 12 by multiple reflections inside. Specifically, the integrator rod 13 outputs illumination light with homogenized illuminance and light intensity distribution of two lights F1 and F2 synthesized by the prism 110 described later.

[0071] The optical element for homogenizing light is not limited to the integrator rod 13, and may be, for example, a prismatic light tunnel whose four surfaces are combined using reflectors or a fly-eye lens.

[0072] The illumination optical system 14 is an optical system for guiding the illumination light output from the integrator rod 13 to the DMD 15. The illumination optical system 14 is composed of optical elements including lenses and reflecting mirrors.

[0073] The DMD 15 is an element that generates an image by reflecting the illumination light guided by the illumination optical system 14 through a micro mirror provided on the surface. The DMD 15 may be replaced by a transmissive liquid crystal element or a reflective liquid crystal element.

[0074] The projection optical system 16 is provided downstream of the optical path of the DMD 15 and is an optical system that amplifies light representing an image generated by the DMD 15 and projects the amplified light as projection light onto a projection surface W as a screen. The projection optical system 16 is composed of optical elements including lenses and reflective mirrors.

[0075] The following references Figure 2 , the structure of the lighting device 12 is described in detail. Figure 2 1 is a plan view of the image projection device 10 viewed from above.

[0076] like Figure 2 As shown, the lighting device 12 includes a first light source unit LS1 , a second light source unit LS2 , a prism 110 , and a color wheel 111 .

[0077] The first light source unit LS1 is a unit that irradiates the prism 110 with light F1 after the excitation light irradiated from the light source is optically processed by various optical elements inside. Figure 2As shown, the first light source unit LS1 has an LED (Light Emitting Diode) light source 101a, a collimating lens 102a, a light source optical system 103a, a focusing element 104a, a microlens array 105a, a dichroic mirror 106a, a first focusing optical system 107a, a phosphor wheel 108a, and a second focusing optical system 109a.

[0078] The LED light source 101a is a light source element that uses an LED as a light source to emit excitation light. The LED light source 101a is not limited to an LED, and may be, for example, a multi-chip laser diode unit in which a plurality of light emitting units are arranged in a one-dimensional or two-dimensional array.

[0079] The collimator lens 102a is an optical element disposed opposite to the light emitting side of the LED light source 101a and converts the excitation light emitted from the LED light source 101a into parallel light.

[0080] The light source optical system 103 a is an optical element that converges the excitation light converted into parallel light by the collimator lens 102 a .

[0081] The light-converging element 104 a is a lens element having negative refractive power disposed in the subsequent stage of the light-source optical system 103 a , and is used to relax the convergence of the excitation light converged by the light-source optical system 103 a .

[0082] The microlens array 105 a is a light profile adjusting element that equalizes the light intensity distribution of the irradiation point of the excitation light irradiated to a desired position on the subsequent fluorescent wheel 108 a .

[0083] The dichroic mirror 106a is a reflective element that reflects only light having a specific wavelength among the beams of excitation light that have passed through the microlens array 105a. A reflective diffractive optical element (DOE: Diffractive Optical Element) may be used instead of the dichroic mirror 106a.

[0084] The first condensing optical system 107a is an optical component that allows the excitation light reflected by the dichroic mirror 106a to appear as an irradiation point at a desired position of the fluorescent wheel 108a. As described later, the light reflected by the fluorescent wheel 108a passes through the first condensing optical system 107a again and is emitted to the second condensing optical system 109a.

[0085] The phosphor wheel 108a is a disc-shaped wavelength conversion element that is driven by a motor to rotate at a high speed. The phosphor wheel 108a has a wavelength conversion area coated with phosphor, namely the phosphor area, and a non-wavelength conversion area that reflects the excitation light, namely the excitation light reflection area. That is, through the rotation of the phosphor wheel 108a, the phosphor area and the excitation light reflection area are switched with each other at the position of the above-mentioned irradiation point. In this embodiment, blue light with a central wavelength of luminous intensity of, for example, 455 [nm] can be used as the excitation light emitted from the LED light source 101a. In this case, when the excitation light reflection area is located at the position of the irradiation point, the phosphor wheel 108a does not perform wavelength conversion and directly outputs blue light. On the other hand, when the fluorescent area is located at the position of the irradiation point, the phosphor wheel 108a converts the wavelength into yellow or yellow-green fluorescent light output.

[0086] The fluorescent wheel 108a is divided into two regions, a fluorescent region and an excitation light reflecting region, but is not limited thereto and may have a plurality of fluorescent regions converted to have different wavelengths (e.g., a fluorescent region emitting yellow light and a fluorescent region emitting green light, etc.), or may have a plurality of excitation light reflecting regions.

[0087] The second condensing optical system 109 a is an optical component that condenses the light reflected by the fluorescent wheel 108 a and transmitted through the first condensing optical system 107 a . The light condensed by the second condensing optical system 109 a enters the reflecting surface 110A of the prism 110 .

[0088] The second light source unit LS2 is a unit that irradiates the prism 110 with light F2 after the excitation light irradiated from the light source is optically processed by various optical elements inside. Figure 2 As shown, the second light source unit LS2 includes an LED light source 101b, a collimating lens 102b, a light source optical system 103b, a light focusing element 104b, a microlens array 105b, a dichroic mirror 106b, a first light focusing optical system 107b, a phosphor wheel 108b, and a second light focusing optical system 109b. The functions of the LED light source 101b, the collimating lens 102b, the light source optical system 103b, the light focusing element 104b, the microlens array 105b, the dichroic mirror 106b, the first light focusing optical system 107b, the phosphor wheel 108b, and the second light focusing optical system 109b are respectively the same as the functions of the above-mentioned LED light source 101a, the collimating lens 102a, the light source optical system 103a, the light focusing element 104a, the microlens array 105a, the dichroic mirror 106a, the first light focusing optical system 107a, the phosphor wheel 108a, and the second light focusing optical system 109a. The light condensed by the second condensing optical system 109 b enters the transmission surface 110B of the prism 110 .

[0089] The prism 110 is a polyhedral synthetic optical element having more than four faces. The prism 110 reflects the light F1 irradiated by the first light source unit LS1 with the reflection surface 110A, and allows the light F2 irradiated by the second light source unit LS2 to pass through the transmission surface 110B, thereby synthesizing the light F1 and the light F2 into a light beam heading in approximately the same direction and guiding them to the integrator rod 13.

[0090] It is preferred that the transmission surface 110B on which the light F2 is incident in the prism 110 is a diffusion surface. By using the transmission surface 110B as a diffusion surface, the unevenness of the color and brightness of the light passing through the transmission surface 110B can be eliminated. It is also possible to provide a diffusion plate instead of a diffusion surface on the prism 110 to eliminate the unevenness of the color and brightness of the light.

[0091] The combining optical element is not limited to the prism 110 , and any optical element may be used as long as it can combine the lights emitted by two or more light source units into lights directed in substantially the same direction and guide the lights to the integrator rod 13 .

[0092] The color wheel 111 is disposed between the prism 110 and the integrator rod 13, and is a disk-shaped element that time-divides the light synthesized by the prism 110 into red, blue, green, and yellow. Specifically, the color wheel 111 has a red area that allows only red light to pass through, a blue area that allows only blue light to pass through, a green area that allows only green light to pass through, and a yellow area that allows only yellow light to pass through. The color wheel 111 is driven by a motor to rotate and time-divide the light synthesized by the prism 110 into red, blue, green, and yellow. The time-divide light that passes through the color wheel 111 is incident on the integrator rod 13.

[0093] The color wheel 111 is controlled to rotate synchronously at the same speed as the fluorescent body wheels 108a and 108b. For example, as described above, when the fluorescent light divided into blue light and yellow (or yellow-green) by the fluorescent body wheels 108a and 108b is incident on the color wheel 111, the color wheel 111 is controlled to rotate so that the blue area of ​​the color wheel 111 corresponds to the excitation light reflection area of ​​the fluorescent body wheels 108a and 108b, and the red area, green area and yellow area correspond to the fluorescent body area of ​​the fluorescent body wheels 108a and 108b. In this way, the red, blue, green and yellow lights divided by the fluorescent body wheels 108a and 108b and the color wheel 111 are averaged by the integrator rod 13 and guided to the DMD 15.

[0094] The color wheel 111 may be disposed at the rear stage (light emission side) of the integrator rod 13 .

[0095] <Hardware Configuration of Image Projection Device>

[0096] Figure 3 FIG. 1 is a block diagram showing an example of a hardware configuration of an image projection device according to an embodiment of the present invention. Figure 3 , the hardware structure of the image projection device 10 involved in this embodiment is described.

[0097] like Figure 3 As shown, the image projection device 10 includes a CPU (Central Processing Unit) 801, a ROM (Read Only Memory) 802, a RAM (Random Access Memory) 803, a media I / F 807, an operation unit 808, a power switch 809, a network I / F 811, an LED driving circuit 814, an external device connection I / F 818, a fan driving circuit 819, and a cooling fan 820. In order for the CPU 801, the ROM 802, the RAM 803, the media I / F 807, the operation unit 808, the network I / F 811, the LED driving circuit 814, the external device connection I / F 818, and the fan driving circuit 819 to communicate data with each other, they are electrically connected via a bus 810 such as an address bus and a data bus.

[0098] The CPU 801 is a computing device that controls the overall operation of the image projection device 10. The ROM 802 is a nonvolatile storage device that stores a computer program for driving the CPU 801. The RAM 803 is a volatile storage device that is used as a work area for the CPU 801.

[0099] The medium I / F 807 is an interface circuit that controls the reading and writing (storage) of data with respect to a medium 806 such as a flash memory.

[0100] The operation unit 808 is provided with various keys, buttons, LEDs, etc., and is used to perform various operations other than turning on / off the power of the image projection device 10 by the user. For example, the operation unit 808 receives operation instructions such as the size adjustment operation, the color tone adjustment operation, the focus adjustment operation, and the trapezoidal adjustment operation of the projected image, and outputs the received operation content to the CPU 801.

[0101] The power switch 809 is a switch for switching the power of the image projection device 10 on and off.

[0102] The network I / F 811 is an interface circuit for performing data communication using a communication network such as the Internet.

[0103] The LED driving circuit 814 is a driving circuit that controls the lighting and extinguishing of the LED light sources 101 a and 101 b under the control of the CPU 801 .

[0104] The peripheral connection I / F 818 is an interface circuit for connecting to an external device such as a PC (Personal Computer) and performing communication such as signal control and image data.

[0105] The fan driving circuit 819 is connected to the CPU 801 and the cooling fan 820, and is a driving circuit for driving / stopping the cooling fan 820 according to a control signal from the CPU 801. The cooling fan 820 is driven by the fan driving circuit 819 to rotate, thereby exhausting the air inside the image projection device 10 and cooling the inside of the image projection device 10.

[0106] After the CPU 801 starts supplying power, it starts according to the control program pre-stored in the ROM 802, and sends a control signal to the LED driving circuit 814 to light up the LED light sources 101a and 101b. The CPU 801 provides a control signal to the fan driving circuit 819 to rotate the cooling fan 820 at a specified rated speed. In addition, in the image projection device 10, after the power supply circuit starts supplying power, the DMD 15 becomes ready for image display, and the power supply circuit supplies power to various other components.

[0107] When the power switch 809 is OFF, the power OFF signal in the image projection device 10 is sent from the power switch 809 to the CPU 801. After detecting the power OFF signal, the CPU 801 gives a control signal to the LED driving circuit 814 to turn off the LED light sources 101a and 101b. Then, after a predetermined time, the CPU 801 gives a control signal to the fan driving circuit 819 to stop the cooling fan 820. At the same time, the CPU 111 terminates its own control processing and finally gives an instruction to the power circuit to stop the power supply.

[0108] <Functional Block Structure and Operation of Image Projection Device>

[0109] Figure 4 This is a functional block diagram of an image projection device according to an embodiment. Figure 5 This is an example of a continuous image frequency characteristic diagram. Figure 6 This is an example of a discrete image frequency characteristic diagram. Figure 7 This is an example of a gamma curve. Figures 4 to 7 , the configuration and operation of the functional modules of the image projection device 10 of this embodiment will be described.

[0110] like Figure 4 As shown, the image projection device 10 includes an acquisition unit 201, a feature extraction unit 202 (extraction unit), an image type determination unit 203 (first determination unit), a brightness determination unit 204 (second determination unit), an image classification unit 205 (classification unit), an image change detection unit 206 (detection unit), a gamma curve switching unit 207 (switching unit), a projection control unit 208, and a storage unit 209.

[0111] The acquisition unit 201 is a functional unit that acquires image data through the medium I / F 807 , the external device connection I / F 818 , or the network I / F 811 .

[0112] The feature extraction unit 202 is a functional unit that extracts feature quantities by performing frequency analysis on the image data obtained by the acquisition unit 201, decomposing the signal level of the brightness value of the image data into frequency components. For example, when the image data obtained by the acquisition unit 201 is animation data, the feature extraction unit 202 cumulatively performs frequency analysis on a number of frames and extracts the decomposed frequency components as feature quantities.

[0113] In this Figure 5 As shown in FIG. 1 , if the signal level frequency component of the image data completely includes the wide frequency range, it is judged to be a natural image, etc., and the image represented by such image data is called a continuous image. Figure 6 As shown, if the frequency components of the signal level of image data are discretely dispersed, it is determined that the image data is presentation data containing a lot of text, and the image represented by such image data is called a discrete image.

[0114] The image type determination unit 203 is a functional unit for determining the type of image, and determines whether the image represented by the image data is a continuous image (first image) or a discrete image (second image) based on the frequency components of the image data extracted by the feature extraction unit 202. For example, the image type determination unit 203 determines that the image represented by the image data is a continuous image when a frequency component having a signal level greater than a predetermined threshold value exists within the entire predetermined frequency range, and determines that the image represented by the image data is a discrete image when a frequency component having a signal level greater than a predetermined threshold value exists within the entire predetermined frequency range. However, the method for determining whether a continuous image is a discrete image is not limited to the above method.

[0115] The brightness determination unit 204 is a functional unit that determines whether the image represented by the image data acquired by the acquisition unit 201 is a bright image (third image) or a dark image (fourth image). For example, the brightness determination unit 204 may calculate the APL (Average Picture Level) of the image represented by the image information, and determine that the image is bright when the APL is above a predetermined threshold, and determine that the image is dark when the APL is below the threshold. The method of determining whether the image is bright or dark is not limited to the above method.

[0116] The image classification unit 205 is a functional unit that classifies the pattern of the image represented by the image data acquired by the acquisition unit 201 based on the determination results of the image type determination unit 203 and the brightness determination unit 204. Specifically, the image classification unit 205 classifies the image into any one of the four types of continuous type image and bright bright image, continuous type image and dark image, discrete type image and bright image, and discrete type image and dark image.

[0117] The images classified by the image classification unit 205 are not limited to the above-mentioned four types, and may be classified into types other than the four types. For example, it is not limited to whether the image type determination unit 203 determines whether it is a continuous image or a discrete image, and it may be determined to be any of three or more types of images based on the frequency components of the image data. It is also not limited to whether the brightness determination unit 204 determines whether it is a bright image or a dark image, and it may be determined to be any of images with three or more levels of brightness based on the APL of the above-mentioned image data. As a result, it may be classified into four or more types by the image classification unit 205. In addition, the image classification unit 205 is not limited to classifying the type of image represented by the image data based on the judgment results of both the image type determination unit 203 and the brightness determination unit 204, and may be classified based on the judgment results of at least one of the image type determination unit 203 and the brightness determination unit 204.

[0118] The image change detection unit 206 is a functional unit that detects whether the type of the image classified by the image classification unit 205 is changed to a type different from the type of the image previously classified by the image classification unit 205 .

[0119] The gamma curve switching unit 207 is a functional unit that switches the gamma curve applicable to the image data when the image type of the image data is detected to be changed to another type by the image change detection unit 206. Switching the gamma curve applicable to the image data means, for example, when the image data is animation data, when the type of the image of the next frame (or frame group) of a specific frame included in the animation data is changed from the type of the image of the specific frame (or frame group) to another type, switching the gamma curve from the gamma curve applicable to the specific frame to the gamma curve applicable to the next frame.

[0120] The gamma curve is a brightness curve that controls the relationship between the input level and the output level of the image data so that the displayed image (the image projected by the image projection device 10 in this case) changes from black to white (or from white to black) in a predetermined manner and determines the intermediate brightness level. For example, when displaying an image of image data, in order to make the image appear to change from black to white with a certain amount of change (i.e., linearly), the gamma curve that controls the relationship between the input level and the output level of the image data is the gamma curve that is most suitable for the image projection device 10 of the display device, for example, Figure 7On the other hand, in order to make the image appear bright as a whole by displaying the intermediate brightness level higher than the gamma curve GC2, the gamma curve that controls the relationship between the input level and the output level of the image data is used, for example Figure 7 The gamma curve GC1 shown in the figure is represented. In order to make the image as a whole appear dark by making the intermediate brightness level appear lower than the gamma curve GC2, the gamma curve that can control the relationship between the input level and the output level of the image data is represented by, for example Figure 7 That is, by switching the gamma data suitable for the image data, the image display form of the image data can be changed. Figure 7 As shown, no matter which gamma curve is used, the brightness level (luminance) of black and white does not change, and only the intermediate brightness level changes. In the description of this embodiment, it is assumed that data of gamma curves GC1 to GC3 are stored in the storage unit 209 .

[0121] Here, since various frequency components are mixed in a continuous image such as a natural picture, it is difficult to identify a focus deviation. Therefore, when the image change detection unit 206 detects that the image type of the image data is switched to a continuous image type, the gamma curve switching unit 207 switches to the gamma curve GC2 that is most suitable for the display device and applies the gamma curve GC2 to the image data.

[0122] On the other hand, since discrete images such as presentation data are often assumed to require reading of text when displaying character strings, it is judged that focus deviation is very likely to be recognized. The drift of the lens of the projection optical system 16 depends on the amount of light transmitted (i.e., the brightness of the image), so when the amount of light changes sharply, the drift becomes obvious. In this regard, since the occurrence of drift itself cannot be avoided, the present embodiment makes it difficult to recognize focus deviation by controlling the drift occurrence experience time. Specifically, when the image change detection unit 206 detects that the type of image data is changed to a discrete image and a dark image type, the gamma curve switching unit 207 switches to a gamma curve GC1 that makes the middle brightness level appear higher than the gamma curve GC2, and applies the gamma curve GC1 to the image data. When the image change detection unit 206 detects that the type of image data is changed to a discrete image and a bright image type, the gamma curve switching unit 207 switches to a gamma curve GC3 that makes the middle brightness level appear lower than the gamma curve GC2, and applies the gamma curve GC3 to the image data. This can make the sharp changes in image brightness become smoother, so that the drift also becomes smoother and the focus deviation is difficult to identify.

[0123] The gamma curve switching unit 207 is not limited to switching from the three gamma curves GC1 to GC3 to any one gamma curve, and may switch to any one of four or more gamma curves according to the type of the image detected by the image change detection unit 206 .

[0124] The projection control unit 208 is a functional unit that applies the gamma curve switched by the gamma curve switching unit 207 to the image data acquired by the acquisition unit 201, controls the DMD 15 to generate an image, and projects the image from the projection optical system 16. Specifically, the projection control unit 208 refers to the storage unit 209, reads the data of the gamma curve switched by the gamma curve switching unit 207, and applies the data of the gamma curve to the image data.

[0125] The storage unit 209 is a functional unit for storing gamma curve data and image data acquired by the acquisition unit 201. Figure 3 The ROM 802 or RAM 803 shown is implemented.

[0126] The acquisition unit 201, feature extraction unit 202, image type determination unit 203, brightness determination unit 204, image classification unit 205, image change detection unit 206, gamma curve switching unit 207 and projection control unit 208 are described above, for example, by Figure 3 At least a part of the acquisition unit 201, the feature extraction unit 202, the image type determination unit 203, the brightness determination unit 204, the image classification unit 205, the image change detection unit 206, the gamma curve switching unit 207 and the projection control unit 208 may also be implemented by a hardware circuit such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0127] Figure 4 The functional units of the image projection device 10 shown in the figure are only functional units that conceptually represent their functions, and are not limited to such configurations. Figure 4 The modules shown do not need to be constituted as clear software modules, and the functions of the functional units can be realized as a whole by executing the program in the image projection device 10. Figure 4 In the image projection device 10 shown in FIG. 1 , a plurality of functional units shown as independent functional units may be configured as one functional unit. Figure 4 In the image projection device 10 shown, the functions of one functional unit are divided into a plurality of functional units.

[0128] <Overall Operation of Image Projection Device>

[0129] Figure 8 FIG. 1 is an example of an operation flow chart of the image projection device according to the embodiment. Figure 8 , the overall operation flow of the image projection device 10 of this embodiment is described.

[0130] <Step S11>

[0131] The acquisition unit 201 of the image projection device 10 acquires the image data via the medium I / F 807, the peripheral connection I / F 818, or the network I / F 811. Then, the process proceeds to step S12 and step S14.

[0132] <Step S12>

[0133] The feature extraction unit 202 of the image projection device 10 performs frequency analysis on the image data acquired by the acquisition unit 201 to decompose the signal level of the brightness value of the image data into frequency components and extracts the frequency components as feature quantities. Then, the process proceeds to step S13.

[0134] <Step S13>

[0135] The image type determination unit 203 of the image projection device 10 determines whether the image represented by the image data is a continuous image or a discrete image based on the frequency components of the image data extracted by the feature quantity extraction unit 202 .

[0136] <Step S14>

[0137] The brightness determination unit 204 of the image projection device 10 determines whether the image represented by the image data acquired by the acquisition unit 201 is a bright image or a dark image.

[0138] After the processing of the above steps S13 and S14 is completed, the process proceeds to step S15.

[0139] <Step S15>

[0140] The image classification unit 205 of the image projection device 10 classifies the image represented by the image data acquired by the acquisition unit 201 according to the judgment results of the image type judgment unit 203 and the brightness judgment unit 204. Specifically, the image classification unit 205 classifies the image into one of the four types: a continuous image and a bright image, a continuous image and a dark image, a discrete image and a bright image, and a discrete image and a dark image. Then, the process proceeds to step S16.

[0141] <Step S16>

[0142] The image change detection unit 206 of the image projection device 10 detects whether the type of the image classified by the image classification unit 205 has changed to a type different from the image previously classified by the image classification unit 205. When the image change detection unit 206 detects that the type of the image has changed (changed) (step S16: Yes), the process proceeds to step S17, and when no change is detected (step S16: No), the operation ends.

[0143] <Step S17>

[0144] The gamma curve switching unit 207 of the image projection device 10 switches the gamma curve, and uses the gamma curve corresponding to the type of the image detected to be changed by the image change detection unit 206 for the image data acquired by the acquisition unit 201. Specifically, when the image change detection unit 206 detects that the type of the image of the image data has changed to the type of a continuous image, the gamma curve switching unit 207 switches to the gamma curve GC2 that is most suitable for the display device, and applies the gamma curve GC2 to the image data. When the image change detection unit 206 detects that the type of the image of the image data has changed to the type of a discrete image and a dark image, the gamma curve switching unit 207 switches to the gamma curve GC1 that displays the intermediate brightness level higher than the gamma curve GC2, and applies the gamma curve GC1 to the image data. When the image change detection unit 206 detects that the type of the image of the image data has changed to the type of a discrete image and a bright image, the gamma curve switching unit 207 switches to the gamma curve GC3 that displays the intermediate brightness level lower than the gamma curve GC2, and applies the gamma curve GC3 to the image data. Then, the projection control unit 208 of the image projection device 10 applies the gamma curve switched by the gamma curve switching unit 207 to the image data acquired by the acquisition unit 201, controls the DMD 15 to generate an image, and projects the image from the projection optical system 16. Then, the operation ends.

[0145] When the entire image data is acquired by the acquisition unit 201 and stored in the storage unit 209 in step S11, steps S12 to S17 may be repeatedly executed with reference to the image data stored in the storage unit 209.

[0146] As described above, in the image projection device 10 of the present embodiment, the acquisition unit 201 acquires image data, the image classification unit 205 classifies the type of image represented by the image data acquired by the acquisition unit 201, and the image change detection unit 206 detects whether the type classified by the image classification unit 205 has changed. When the image change detection unit 206 detects that the image type has changed, the gamma curve switching unit 207 switches the gamma curve used for the image data to a gamma curve corresponding to the image type. In this way, since there is no need to install a focusing mechanism or a camera device or other mechanism or device in order to deal with the focus deviation, the structural complexity can be reduced, and the focus deviation is difficult to be identified.

[0147] In the above-mentioned embodiment, when at least one of the functional units of the image projection device 10 is implemented by executing a program, the program can be installed in a ROM or the like in advance and provided. The above-mentioned embodiment can also be configured such that the program executed in the image projection device 10 is recorded in a computer-readable recording medium such as a CDROM (Compact Disc Read Only Memory), a floppy disk (FD), a CD-R (Compact Disk-Recordable), or a DVD-R (Digital Versatile Disc) as a document in an installable format or an executable format and provided. Furthermore, the above-mentioned embodiment can also be configured such that the program executed in the image projection device 10 is stored in a computer connected to a network such as the Internet and provided by downloading the network. Furthermore, the above-mentioned embodiment can also be configured such that a computer program product for execution by the image projection device 10 is provided or released through a network such as the Internet. In the above-mentioned embodiment, the program executed in the image projection device 10 includes a module structure of at least any one of the above-mentioned functional units, and is generated by the CPU 801 as actual hardware reading the program from the above-mentioned storage device (such as ROM 802, medium 806, etc.) and executing it, and loading the above-mentioned functional units onto the main storage device (RAM 803).

[0148] The aspects of the present invention are as follows.

[0149] <1> An image projection device for projecting an image using a projection optical system, comprising:

[0150] An acquisition unit, used for acquiring image data;

[0151] a classification unit, configured to classify the type of the image represented by the image data acquired by the acquisition unit;

[0152] a detection unit, configured to detect whether the type classified by the classification unit has changed; and

[0153] A switching unit is used to switch the gamma curve applied to the image data to a gamma curve corresponding to the type of image represented by the image data when the detection unit detects the occurrence of the type.

[0154] <2> according to <1> The image projection device further comprises a projection control unit for applying the gamma curve switched by the switching unit to the image data so that the projection optical system projects an image.

[0155] <3> according to <2> The image projection device, wherein:

[0156] A storage unit is also provided for storing data of a plurality of gamma curves.

[0157] The projection control unit reads out data corresponding to the gamma curve switched by the switching unit from the storage unit, and applies the data to the image data.

[0158] <4> according to <1> ~ <3> The image projection device as described in any one of the preceding claims, further comprising:

[0159] an extracting unit configured to extract a predetermined feature amount of the image data acquired by the acquiring unit; and

[0160] a first determination unit configured to determine the type of image represented by the image data based on the feature quantity extracted by the extraction unit;

[0161] The classification unit classifies the type of the image represented by the image data based on at least the determination result of the first determination unit.

[0162] <5> according to <4> The image projection device, wherein:

[0163] The extracting unit decomposes the brightness value of the image data acquired by the acquiring unit into frequency components and extracts the frequency components as the feature amount.

[0164] The first determination unit determines, based on the frequency component extracted by the extraction unit, whether the image represented by the image data is a first image in which at least the frequency component exists continuously within a predetermined frequency range or a second image in which the frequency component exists discretely.

[0165] <6> according to <1> ~ <5> The image projection device described in any one of the above further comprises a second judgment unit for judging whether the image represented by the image data acquired by the acquisition unit is a third image having at least a specified brightness or a fourth image darker than the third image, and the classification unit classifies the type of the image represented by the image data based at least on the judgment result of the second judgment unit.

[0166] <7> An image projection method for projecting an image from a projection optical system, comprising: an acquisition step for acquiring image data; a classification step for classifying the type of the image represented by the acquired image data; a detection step for detecting whether the classified type has changed; and a switching step for switching a gamma curve applied to the image data to a gamma curve corresponding to the type of the image represented by the image data when a change in the type is detected.

[0167] <8> A computer program product is used to cause a computer, which is an image projection device that projects an image from a projection optical system, to execute the following steps: an acquisition step of acquiring image data; a classification step of classifying the type of the image represented by the acquired image data; a detection step of detecting whether the classified type has changed; and a switching step of switching a gamma curve applied to the image data to a gamma curve corresponding to the type of the image represented by the image data when a change in the type is detected.

Claims

1. An image projection device for projecting an image using a projection optical system, comprising: An acquisition unit, used for acquiring image data; a classification unit, configured to classify the type of the image represented by the image data acquired by the acquisition unit; a detection unit, configured to detect whether the type classified by the classification unit has changed; and The switching unit is configured to switch the gamma curve applied to the image data to a gamma curve corresponding to the type of the image represented by the image data when the detection unit detects that the type has changed. 2 . The image projection device according to claim 1 , further comprising a projection control unit for applying the gamma curve switched by the switching unit to the image data to cause the projection optical system to project an image. 3 .

3. The image projection device according to claim 2, wherein: A storage unit is also provided for storing data of a plurality of gamma curves. The projection control unit reads out data corresponding to the gamma curve switched by the switching unit from the storage unit, and applies the data to the image data.

4. The image projection device according to any one of claims 1 to 3, further comprising: an extracting unit configured to extract a predetermined feature amount of the image data acquired by the acquiring unit; and a first determination unit configured to determine the type of image represented by the image data based on the feature quantity extracted by the extraction unit; The classification unit classifies the type of the image represented by the image data based on at least the determination result of the first determination unit.

5. The image projection device according to claim 4, wherein: The extracting unit decomposes the brightness value of the image data acquired by the acquiring unit into frequency components and extracts the frequency components as the feature amount. The first determination unit determines, based on the frequency component extracted by the extraction unit, whether the image represented by the image data is a first image in which at least the frequency component exists continuously within a predetermined frequency range or a second image in which the frequency component exists discretely.

6. The image projection device according to any one of claims 1 to 5, wherein: further comprising a second determination unit for determining whether the image represented by the image data acquired by the acquisition unit is a third image having at least a predetermined brightness or a fourth image darker than the third image, The classification unit classifies the type of the image represented by the image data based on at least the determination result of the second determination unit.

7. An image projection method for projecting an image from a projection optical system, comprising: An acquisition step of acquiring image data; a classification step of classifying the type of image represented by the acquired image data; A detection step of detecting whether the classified type has changed; as well as A switching step, when a change in the type is detected, switches the gamma curve applied to the image data to a gamma curve corresponding to the type of the image represented by the image data.

8. A computer program product for causing a computer as an image projection device for projecting an image from a projection optical system to execute the following steps: An acquisition step of acquiring image data; a classification step of classifying the type of image represented by the acquired image data; A detection step of detecting whether the classified type has changed; as well as A switching step, when a change in the type is detected, switches the gamma curve applied to the image data to a gamma curve corresponding to the type of the image represented by the image data.

Images