Projection system, method of controlling projector, and projector

A projection system includes a recursive reflector located in a first area of a projection surface, a projection device configured to project a first image and a second image at respective timings different from each other, an imaging device configured to image a first projection area in a situation in which the projection device projects the first image in the first projection area including the first area to thereby generate imaging data, and a control device configured to identify a position of the recursive reflector based on the imaging data, and decide a second projection area in which the second image is projected based on the position of the recursive reflector, wherein the projection device and the imaging device are disposed so that a contrast ratio between the recursive reflector and a periphery of the recursive reflector becomes equal to or higher than a predetermined value.

The present application is based on, and claims priority from JP Application Serial Number 2020-027005, filed Feb. 20, 2020, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a projection system, a method of controlling a projector, and a projector.

2. Related Art

JP-A-2006-98789 (Document1) discloses a projector which uses a recursive reflector provided to a projection surface such as a whiteboard to set a projection area of a projection image. The projector described above images the projection surface on which the recursive reflector is located with an imaging section while projecting a white image on the projection surface from a projection section to thereby generate imaging data. The projector described above identifies the position of the recursive reflector based on the imaging data, and then decides the projection area of the projection image to be projected subsequently to the white image based on the position of the recursive reflector.

In the projector described in Document1, when reflected light by the recursive reflector fails to enter the imaging section due to the positions of the projection section and the imaging section and so on, the imaging data fails to represent the recursive reflector, and it becomes difficult to identify the position of the recursive reflector.

SUMMARY

A projection system according to an aspect of the present disclosure includes a recursive reflector located in a first area of a projection surface, a projection device configured to project a first image and a second image at respective timings different from each other, an imaging device configured to image a first projection area in a situation in which the projection device projects the first image in the first projection area including the first area to thereby generate imaging data, and a control device configured to identify a position of the recursive reflector based on the imaging data, and decide a second projection area in which the second image is projected based on the position of the recursive reflector, wherein the projection device and the imaging device are disposed so that a contrast ratio between the recursive reflector and a periphery of the recursive reflector represented by the imaging data becomes equal to or higher than a predetermined value.

A method of controlling a projector according to another aspect of the present disclosure is a method of controlling a projector including a projection section configured to project an image and an imaging section configured to perform imaging, the method including the steps of projecting a guide image representing a first area in which a recursive reflector is to be disposed out of a projection surface from the projection section, projecting a first image in a first projection area including the first area in which the recursive reflector is disposed from the projection section, imaging the first projection area with the imaging section in a situation in which the projection section projects the first image in the first projection area to thereby generate imaging data, identifying a position of the recursive reflector based on the imaging data, and deciding a second projection area in which the second image is projected by the projection section based on the position of the recursive reflector, wherein the first area is set so that a contrast ratio between the recursive reflector and a periphery of the recursive reflector represented by the imaging data becomes equal to or higher than a predetermined value.

A projector according to another aspect of the present disclosure includes a projection section configured to project a guide image representing a first area in which a recursive reflector is to be disposed out of a projection surface, and project a first image in a first projection area including the first area in which the recursive reflector is disposed after projecting the guide image, an imaging section configured to image the first projection area in a situation in which the projection section projects the first image in the first projection area to thereby generate imaging data, and a decision section configured to identify a position of the recursive reflector based on the imaging data, and decide a second projection area in which a second image is projected by the projection section based on the position of the recursive reflector, wherein the first area is set so that a contrast ratio between the recursive reflector and a periphery of the recursive reflector represented by the imaging data becomes equal to or higher than a predetermined value.

DESCRIPTION OF AN EXEMPLARY EMBODIMENT

A. First Embodiment

FIG. 1is a diagram showing a projection system1000according to a first embodiment. The projection system1000includes a projector1, a first object7a, a second object7b, a third object7c, and a fourth object7d.

The projector1is supported by a first support device3installed on the ceiling2. The first support device3can be installed on a wall or the like instead of the ceiling2. The projector1is coupled to a PC (Personal Computer)4with a wired LAN (Local Area Network), a wireless LAN, or the like. The coupling between the projector1and the PC4is not limited to the wired LAN or the wireless LAN. For example, the projector1can be coupled to the PC4via a USB (Universal Serial Bus) cable, an HDMI (High Definition Multimedia Interface) cable, or a VGA (Video Graphics Array) cable. USB is a registered trademark. HDMI is a registered trademark.

The projector1receives image data from the PC4. The PC4is an example of an image data provision device. The image data provision device is not limited to the PC4. For example, the image data provision device can be a DVD (Digital Versatile Disc) player. DVD is a registered trademark. It is possible for the projector1to read the image data from a recording medium such as a USB memory to thereby receive the image data. The image data represents an advertisement. It is possible for the image data to represent information different from the advertisement such as a material for a presentation.

The projector1projects the image generated by a liquid crystal light valve12described later, specifically, the image represented by the image data, from a projection section104toward a projection surface5a.

Hereinafter, the image generated by the liquid crystal light valve12is referred to as a “generation image.” The image displayed on the projection surface5aby the projector1projecting the generation image toward the projection surface5ais referred to as a “projection image.” The projection image can become an image in which a distortion based on the positional relationship between the projector1and the projection surface5aoccurs in the generation image. The projector1is capable of performing a keystone distortion correction for correcting the distortion of the projection image.

The color of the projection surface5ais white. The color of the projection surface5ais not limited to white. It should be noted that in order to make the projection image eye-friendly, it is desirable for the color of the projection surface5ato be a color close to white, for example, light gray or cream. The projection surface5ais a surface provided to a projecting board5. The projection surface5ais not limited to the surface provided to the projecting board5. The projection surface5acan be, for example, a screen, a wall, a blackboard, a whiteboard, or a door. The projecting board5is supported by a second support device6installed on the ceiling2. The second support device6can be installed on a wall or the like instead of the ceiling2.

On the projection surface5a, there are disposed the first object7a, the second object7b, the third object7c, and the fourth object7d. The first object7a, the second object7b, the third object7c, and the fourth object7dare the same in size as each other. The first object7a, the second object7b, the third object7c, and the fourth object7bare not required to be the same in size as each other, but can also be made different from each other so as to be the same in size as each other on the imaging data generated by an imaging section106described later.

Hereinafter, when there is no need to distinguish the first object7a, the second object7b, the third object7c, and the fourth object7dfrom each other, the first object7a, the second object7b, the third object7c, and the fourth object7dare each referred to as an “object7.”

The object7sets a projection area8ein the projection surface5a. The projection area8eis, for example, an area in which the image based on the image data received from the PC4is to be projected. The projection surface5ais an example of a first projection area. The projection area8eis an example of a second projection area.

The shape of the projection area8eis a quadrangular shape. The four corners of the projection area8eare set based on the positions of the four objects7. In the present embodiment, the positions of the four objects7constitute the four corners of the projection area8e. When the four objects7are disposed on the four corners of the projection surface5a, the whole of the projection surface5aconstitutes the projection area8e.

The object7is a recursive reflector. The object7reflects most of the incident light toward an opposite direction to the incident direction of the light.

The projector1projects predetermined light such as white image light to the object7from the projection section104. The projector1images the light reflected by the object7with the imaging section106to thereby generate imaging data. The projector1identifies the position of the object7based on the imaging data to decide the projection area8ebased on the position of the object7.

The projector1projects a guide image E1, a projection position detecting image E2, an object detecting image E3, and a display image E4on the projection surface5aat respective timings different from each other.

The guide image E1shows the area in which the object7is to be disposed. The area in which the object7is to be disposed is an example of a first area.

The projection position detecting image E2represents a plurality of dots to be a target of projection position detection. The projection position detecting image E2is used for a calibration of making a camera coordinate system correspond to a liquid crystal panel coordinate system. The camera coordinate system is a coordinate system to be applied to the imaging section106, furthermore, a coordinate system to be applied to a taken image represented by the imaging data. The liquid crystal panel coordinate system is a coordinate system to be applied to the liquid crystal valve12. In the calibration, there is generated a projective transformation matrix for making the camera coordinate system correspond to the liquid crystal panel coordinate system.

The object detecting image E3is projected on the projection surface5ain order to detect the object7. The object detecting image E3includes predetermined light such as white image light to be projected on the object7. The object detecting image E3is an example of a first image.

The display image E4is an image to be projected in the projection area8e. The display image E4is, for example, an image based on the image data received from the PC4. The display image E4is projected after projection of the object detecting image E3. The display image E4is an example of a second image.

FIG. 2is a diagram schematically showing the projector1. The projector1includes an operation receiving section101, an image processing section102, a light valve drive section103, a projection section104, a light source drive section105, the imaging section106, a storage section107, a control section108, and a bus109. The image processing section102includes an image combining section102aand a distortion correction section102b. The projection section104includes a light source11, a red-color liquid crystal light valve12R, a green-color liquid crystal light valve12G, a blue-color liquid crystal light valve12B, and a projection optical system13.

Hereinafter, when there is no need to distinguish the red-color liquid crystal light valve12R, the green-color liquid crystal light valve12G, and the blue-color liquid crystal light valve12B from each other, the red-color liquid crystal light valve12R, the green-color liquid crystal light valve12G, and the blue-color liquid crystal light valve12B are each referred to as a “liquid crystal light valve12.”

The operation receiving section101is, for example, a variety of operation buttons, operation keys, or a touch panel. The operation receiving section101receives an input operation of the user. The operation receiving section101can also be a remote controller for transmitting the information based on the input operation wirelessly or with wire. In this case, the projector1includes a receiving section for receiving the information from the remote controller. The remote controller is provided with a variety of operation buttons, operation keys, or a touch panel for receiving the input operation. It is possible for the operation receiving section101to wirelessly receive the operation input to an application operating in an information terminal device such as a smartphone from the information terminal device.

The image processing section102is formed of a circuit such as a single image processor or two or more image processors. The image processing section102performs image processing on the image data to thereby generate the image signal. For example, the image processing section102performs image processing such as a gamma correction on the image data received from the PC4to thereby generate the image signal. The image data which is received by the image processing section102from other equipment is hereinafter referred to as “reception image data.”

The image combining section102ais constituted by, for example, an image combining circuit. The image combining section102acombines a plurality of image data with each other, or outputs single image data. The image combining section102aoutputs guide image data, projection position detecting image data, object detecting image data, and reception image data at respective timings different from each other.

The guide image data represents the guide image E1. The projection position detecting image data represents the projection position detecting image E2. The object detecting image data represents the object detecting image E3. The reception image data represents the display image E4.

It should be understood that the guide image data, the projection position detecting image data, the object detecting image data, and the reception image data are each image data.

The distortion correction section102bis constituted by, for example, a distortion correction circuit. The distortion correction section102bperforms the keystone distortion correction on the image data output by the image combining section102ato thereby generate the image signal. The keystone distortion correction is processing of adjusting the area in which the generation image is generated in the liquid crystal light valve12so that the display image E4is projected only in the projection area8e.

The light valve drive section103is constituted by a circuit such as a single driver or two or more drivers. The light valve drive section103generates drive voltages based on the image signal. The light valve drive section103drives the liquid crystal light valves12, specifically, the red-color liquid crystal light valve12R, the green-color liquid crystal light valve12G, and the blue-color liquid crystal light valve12B using the drive voltages.

The projection section104emits the generation image toward the projection surface5ato thereby project the projection image on the projection surface5a. For example, the projection section104projects the projection image on the projection surface5aon which the object7is located. The projection section104is an example of a projection device.

The light source11is an LED (Light Emitting Diode). The light source11is not limited to the LED, but can also be, for example, a xenon lamp, a super-high pressure mercury lamp, or a laser source. The light source11emits the light. The light emitted from the light source11enters an integrator optical system not shown. The integrator optical system reduces the unevenness in luminance distribution in the incident light. The light emitted from the light source11passes through the integrator optical system, and is then separated by a color separation optical system not shown into colored light components of red, green, and blue as the three primary colors of light. The red colored light component enters the red-color liquid crystal light valve12R. The green colored light component enters the green-color liquid crystal light valve12G. The blue colored light component enters the blue-color liquid crystal light valve12B.

The liquid crystal light valves12are each formed of a liquid crystal panel having a liquid crystal material existing between a pair of transparent substrates, and so on. The liquid crystal light valves12each have a rectangular pixel area12a. The pixel area12aincludes a plurality of pixels12parranged in a matrix. In each of the liquid crystal light valves12, the drive voltage is applied to the liquid crystal for each of the pixels12p. When the light valve drive section103applies the drive voltages to the respective pixels12p, the light transmittance of each of the pixels12pis set to the light transmittance based on the drive voltage. The light emitted from the light source11passes through the pixel area12ato thereby be modulated. Therefore, the image based on the drive voltages is formed for each colored light. The liquid crystal light valves12are an example of a light modulation device.

The images of the respective colors are combined by a color combining optical system not shown for each of the pixels12p. Therefore, a color image is generated. The color image is projected on the projection surface5avia the projection optical system13.

The light source drive section105drives the light source11. For example, when the operation receiving section101has received the operation input of powering-ON, the light source drive section105makes the light source11emit light.

The imaging section106is, for example, a camera. The imaging section106takes an image of the projection surface5ato thereby generate the imaging data. The imaging section106includes an optical system such as a lens, and an imaging element for converting the light collected by the optical system into an electric signal. The imaging element is, for example, a CCD (Charge Coupled Device) image sensor, or a CMOS (Complementary Metal Oxide Semiconductor) image sensor.

The imaging section106can be disposed as a separate member from the projector1. In this case, the imaging section106and the projector1are coupled to each other with a wired or wireless interface so as to be able to perform transmission/reception of data. The imaging section106is an example of an imaging device.

The storage section107is a computer-readable recording medium. The storage section107stores a program for defining the operation of the projector1, and a variety of types of information.

The control section108is constituted by, for example, a single processor or two or more processors. Citing an example, the control section108is constituted by a signal CPU (Central Processing Unit) or two or more CPUs. Some or all of the functions of the control section108can also be realized by a circuit such as a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The control section108is an example of a control device.

The control section108reads a program stored by the storage section107. The control section108executes the program to thereby realize a projection control section41, an imaging control section42, a projection position detection section43, a coordinate adjustment section44, and a decision section45.

The projection control section41controls the image processing section102and the light source drive section105to thereby control the projection image. The projection control section41can be formed of a circuit such as a single projection controller or two or more projection controllers.

The imaging control section42controls the imaging section106to thereby make the imaging section106generate the imaging data. The imaging control section42can be formed of a circuit such as a single imaging controller or two or more imaging controllers.

The projection position detection section43detects the positions of the plurality of dots represented by the projection position detecting image E2based on the imaging data generated by the imaging section106imaging the projection surface5aon which the projection position detecting image E2is projected. The detection result represents the positions of the plurality of dots in the camera coordinate system. The projection position detection section43can be formed of a circuit such as a projection position detection circuit.

The coordinate adjustment section44generates the projective transformation matrix using the positions of the plurality of dots in the camera coordinate system and the positions of the plurality of dots in the liquid crystal panel coordinate system. The coordinate adjustment section44stores the projective transformation matrix in the storage section107. The coordinate adjustment section44can be formed of a circuit such as a coordinate adjustment circuit.

In the camera coordinate system, when the distortion of the lens provided to the imaging section106affects the positions of the plurality of dots, it is possible for the coordinate adjustment section44to correct the camera coordinate system based on the influence of the distortion of the lens in the imaging section106to thereby generate a standard coordinate system. In this case, the coordinate adjustment section44identifies the positions of the plurality of dots in the standard coordinate system. The coordinate adjustment section44generates the projective transformation matrix using the positions of the plurality of dots in the liquid crystal light valve12to which the liquid crystal panel coordinate system is applied, and the positions of the plurality of dots in the standard coordinate system.

The decision section45identifies the position of the object7based on the imaging data generated by the imaging section106imaging the projection surface5aon which the object detecting image E3is projected.

For example, the decision section45first identifies a high luminance area representing the object7from the taken image. The high luminance area is an area having the luminance no lower than comparative luminance obtained by making the luminance of an adjacent part 1.5 times in the taken image. The value 1.5 is an example of a threshold value. The threshold value is not limited to 1.5, but can be a value greater than 1.5, or can also be a value in a range greater than 1.0 and smaller than 1.5. Further, it is possible for the decision section45to multiply the peak of the luminance in the taken image by a predetermined coefficient to thereby generate a reference value. In this case, it is possible for the decision section45to identify the area having the luminance no lower than the reference value in the taken image as the high luminance area. The predetermined coefficient is, for example, 0.5.

Subsequently, when an area surrounded by the high luminance area exists in the taken image, the decision section45decides an area identified by adding the high luminance area to the area surrounded by the high luminance area as an object area where the object7exists. Further, it is possible for the decision section45to decide an area where the luminance exceeds a predetermined threshold value in the taken image as the object area where the object7exists.

Subsequently, the decision section45identifies the position of the object7based on the object area. Subsequently, the decision section45decides the projection area8ebased on the position of the object7. It is possible for the decision section45to be formed of a circuit such as a decision circuit.

The bas109is coupled to each of the operation receiving section101, the image processing section102, the light valve drive section103, the light source drive section105, the imaging section106, the storage section107, and the control section108.

FIG. 3is a diagram for explaining an example of the keystone distortion correction. Specifically,FIG. 3is a diagram for explaining a method of correcting the generation image to be generated in the liquid crystal light valve12.

A first image G1represented by the image data has a first corner A, a second corner B, a third corner C, and a fourth corner D. The first corner A, the second corner B, the third corner C, and the fourth corner D constitute the four corners of the first image G1.

The distortion correction section102bindividually moves each of the first corner A, the second corner B, the third corner C, and the fourth corner D in accordance with the operation input received by the operation receiving section101to thereby perform the keystone distortion correction. The distortion correction section102bperforms the keystone distortion correction to thereby generate a second image G2. The first image G1and the second image G2are each an example of the generation image.

In the example shown inFIG. 3, the distortion correction section102bmoves the first corner A from a first position a1to a fifth position a5, moves the second corner B from a second position a2to a sixth position a6, moves the third corner C from a third position a3to a seventh position a7, and moves the fourth corner D from a fourth position a4to an eighth position a8.

InFIG. 3, there are shown a first range Ra, a second range Rb, a third range Rc, and a fourth range Rd. The first range Ra is a range in which the first corner A can move in accordance with the keystone distortion correction. The distortion correction section102bmoves the first corner A within the first range Ra. The second range Rb is a range in which the second corner B can move in accordance with the keystone distortion correction. The distortion correction section102bmoves the second corner B within the second range Rb. The third range Rc is a range in which the third corner C can move in accordance with the keystone distortion correction. The distortion correction section102bmoves the third corner C within the third range Rc. The fourth range Rd is a range in which the fourth corner D can move in accordance with the keystone distortion correction. The distortion correction section102bmoves the fourth corner D within the fourth range Rd.

A4. Example of Generation Image

Then, an example of the generation image as each of the guide image E1, the projection position detecting image E2, and the object detecting image E3will be described.

A4-1. Generation Image as Guide Image E1

FIG. 4is a diagram showing an example of the guide image E1represented by the guide image data. In other words,FIG. 4is a diagram showing an example of a generation image based on the guide image data. The guide image E1has first guide areas F11and a second guide area F12. The guide image E1includes a first background F13represented by hatching inFIG. 4. The color of the first background F13is black. The color of the first background F13is not limited to black, but is sufficiently a color different from at least the color of the first guide areas F11. It is possible for the color of the first background F13to be different from either of the color of the first guide areas F11and the color of the second guide area F12.

The first guide areas F11represent ranges in which the first corner A, the second corner B, the third corner C, and the fourth corner D can move, respectively, in accordance with the keystone distortion correction. The color of the first guide areas F11is white. The color of the first guide areas F11is not limited to white, but can be, for example, yellow.

The first guide areas F11include an upper right area Fla, a lower right area F1b, a lower left area F1c, and an upper left area Fld. The upper right area Fla represents a range in which the first corner A can move in accordance with the keystone distortion correction. The lower right area F1brepresents a range in which the second corner B can move in accordance with the keystone distortion correction. The lower left area F1crepresents a range in which the third corner C can move in accordance with the keystone distortion correction. The upper left area F1drepresents a range in which the fourth corner D can move in accordance with the keystone distortion correction.

The positional relationship between the upper right area Fla, the lower right area F1b, the lower left area F1c, and the upper left area F1dis substantially the same as the positional relationship between the first range Ra through the fourth range Rd shown inFIG. 3.

The shape of each of the upper right area Fla, the lower right area F1b, the lower left area F1c, and the upper left F1dis a rectangular shape. The shape of each of the upper right area Fla, the lower right area F1b, the lower left area F1c, and the upper left F1dcan be different from the rectangular shape.

The second guide area F12represents an area where the plurality of dots shown in the projection position detecting image E2is projected. The color of the second guide area F12is white. The color of the second guide area F12is not limited to white, but can be, for example, yellow. The shape of the second guide area F12is a rectangular shape. The shape of the second guide area F12can be different from the rectangular shape.

The guide image E1represents a first message M1. The first message M1encourages to adjust both or one of the position of the guide image E1and the position of the object7so that the object7is located in the first guide area F11displayed on the projection surface5a.

The first message M1represents the words such as “please adjust the projection position so that the object falls within the white areas on the four corners of the projection area.” The first message M1can arbitrarily be changed as long as the first message M1encourages to locate the object7in the first guide area F11. The first message M1can be shown in the second guide area F12, or can also be shown in the first background F13.

The guide image E1further represents a second message M2. The second message M2encourages to locate the second guide area F12in the projection area8e. When the shape of the second guide area F12is a rectangular shape, the second message M2represents the words such as “please adjust the projection position so that the rectangular area at the center of the projection image falls within the projection surface.” The second message M2can arbitrarily be changed as long as the second message M2encourages to locate the second guide area F12in the projection area8e. The second message M2can be shown in the second guide area F12, or can also be shown in the first background F13. The guide image E1can represent only either one of the first message M1and the second message M2, or can also represent both of the first message M1and the second message M2.

A4-2. Generation Image as Projection Position Detecting Image E2

FIG. 5is a diagram showing an example of the projection position detecting image E2represented by the projection position detecting image data. Specifically,FIG. 5is a diagram showing an example of a generation image based on the projection position detecting image data.

The projection position detecting image E2has a projection position detecting pattern F2. The projection position detecting pattern F2has white dots F2athrough F2dshown in a second background F21having a black color. The color of the second background F21is not limited to black, but is sufficiently a color different from the color of the dots F2athrough F2d. The color of the dots F2athrough F2dis not limited to white, but is sufficiently a color different from the color of the second background F21. The dots F2athrough F2dare used for generating the projective transformation matrix. The luminance distribution in each of the dots F2athrough F2dis, for example, a Gaussian distribution. The luminance distribution of the dot is not limited to a luminance distribution having a gradation characteristic such as a Gaussian distribution, but can be a luminance distribution not having the gradation characteristic. It is possible to use marks each having a polygonal shape such as a rectangular shape or a hexagonal shape instead of the dots F2athrough F2d.

A4-3. Generation Image as Object Detecting Image E3

FIG. 6is a diagram showing an example of the object detecting image E3represented by the object detecting image data. In other words,FIG. 6is a diagram showing an example of a generation image based on the object detecting image data.

The object detecting image E3has an object detecting pattern F3. The object detecting pattern F3has patterns F3athrough F3deach having a white color shown in a third background F31having a black color. The patterns F3athrough F3deach having a white color are constituted by white light.

The color of the third background F31is not limited to black, but is sufficiently a color different from the color of the patterns F3athrough F3d. The color of the patterns F3athrough F3dis not limited to white, but is sufficiently a color different from the color of the third background F31. The color of the patterns F3athrough F3dcan be the same as, or can also be different from, the color of the upper right area Fla, the lower right area F1b, the lower left area F1c, and the upper left area F1dshown inFIG. 4.

The color of the patterns F3athrough F3dis preferably the same as the color of the dots F2athrough F2dshown inFIG. 5. When the distortion of the lens provided to the imaging section106is corrected in the camera coordinate system, it is desirable for the color of the dots F2athrough F2dto be a color approximate to a wavelength component of a parameter used when correcting the distortion of the lens provided to the imaging section106. In this case, it is desirable for the color of the dots F2athrough F2dand the color of the patterns F3athrough F3dto be, for example, green instead of white. The light constituting the patterns F3athrough F3dcan be referred to as predetermined light. The white light constituting the patterns F3athrough F3dis an example of the predetermined light. In order to make the detection of the object7easy, it is desirable for the predetermined light to be light having a single color.

The positional relationship between the patterns F3athrough F3dis substantially the same as the positional relationship between the first range Ra through the fourth range Rd shown inFIG. 3. Therefore, when the positions of the guide image E1and the object7are set in accordance with the guide image E1, the first object7ais irradiated with a part of the pattern F3a, the second object7bis irradiated with a part of the pattern F3b, the third object7cis irradiated with a part of the pattern F3c, and the fourth object7dis irradiated with a part of the pattern F3d.

The guide image data, the projection position detecting image data, and the object detecting image data are stored in advance in the storage section107. The guide image data, the projection position detecting image data, and the object detecting image data can be generated by the control section108without being stored in advance in the storage section107.

A5. Example of Projection Image

Then, an example of the projection image as each of the guide image E1, the projection position detecting image E2, and the object detecting image E3will be described.

A5-1. Projection Image as Guide Image E1

FIG. 7is a diagram showing an example of the projection image as the guide image E1. InFIG. 7, a keystone distortion occurs in the guide image E1due to the relative positional relationship between the projector1and the projection surface5a, and so on.

A5-2. Projection Image as Projection Position Detecting Image E2

FIG. 8is a diagram showing an example of the projection image as the projection position detecting image E2. InFIG. 8, a keystone distortion occurs in the projection position detecting image E2due to the relative positional relationship between the projector1and the projection surface5a, and so on.

A5-3. Projection Image as Object Detecting Image E3

FIG. 9is a diagram showing an example of the projection image as the object detecting image E3. InFIG. 9, a keystone distortion occurs in the object detecting image E3due to the relative positional relationship between the projector1and the projection surface5a, and so on. An area Ka irradiated with the pattern F3aout of the projection surface5a, an area Kb irradiated with the pattern F3bout of the projection surface5a, an area Kc irradiated with the pattern F3cout of the projection surface5a, and an area Kd irradiated with the pattern F3dout of the projection surface5aare each an example of the first area. It should be noted that inFIG. 7, there are shown areas Ka1through Kd1each functioning as the first area.

A6. Configuration of Projector1

Then, a configuration of the projector1will be described. Even in the situation in which the object7located on the projection surface5ais irradiated with a part of the object detecting pattern F3, when the imaging section106is located at a position where the imaging section106cannot receive light of a part of the object detecting pattern F3reflected by the object7, the imaging data generated by the imaging section106fails to represent the object7. In this case, the decision section45cannot identify the position of the object7based on the imaging data.

Further, even in a situation in which the imaging section106receives the light of the part of the object detecting pattern F3reflected by the object7, when the high luminance area representing the object7does not exist in the taken image, the decision section45cannot identify the position of the object7based on the imaging data. Here, the high luminance area is an area having the luminance no lower than comparative luminance obtained by making the luminance of an adjacent part 1.5 times in the taken image.

Therefore, the projection section104and the imaging section106are disposed so that the value obtained by dividing the luminance of the object7represented by the imaging data by the luminance of the projection surface5arepresented by the imaging data becomes no lower than 1.5 as a threshold value. In other words, the projection section104and the imaging section106are disposed so that the result of the division becomes no lower than 1.5 irrespective of the position of the object7on the projection surface5a.

Specifically, the user adjusts the position of the projector1and the posture of the projector1to thereby dispose the projection section104and the imaging section106so that a contrast ratio between the object and the periphery becomes no lower than 1.5. It should be understood that the periphery means the periphery of the object. In other words, the user disposes the projection section104and the imaging section106so that the contrast ratio between the object represented by the imaging data and the periphery represented by the imaging data becomes no lower than 1.5.

Here, the reflection characteristics of the object7and the projection surface5awill be described.FIG. 10throughFIG. 13are each a diagram showing reflection characteristics U1of the light in the object7, and reflection characteristics U2of the light in the projection surface5ahigh in light scattering characteristic. The projection surface5ahigh in light scattering characteristic is, for example, a mat screen. InFIG. 10throughFIG. 13, the horizontal axis represents an observation angle T2, and the vertical axis represents reflection intensity T3. InFIG. 10throughFIG. 13, an incident angle T1is 0°, 20°, 40°, 60°, respectively.FIG. 14is an explanatory diagram with respect to the incident angle T1and the observation angle T2corresponding to the disposition of the projection section104and the imaging section106. The incident angle T1is an angle formed between a straight line La passing through an observation point H and the projection section104, and a normal line n of the projection surface5a. The observation angle T2is an angle formed between a straight line Lb passing through the observation point H and the imaging section106, and the straight line La. The fact that the light scattering characteristic is high means that the reflection intensity T3when the observation angle T2is 0° is substantially constant even when the incident angle T1changes from 0° to 60°.

FIG. 10shows the reflection characteristics U1aof light in the object7when the incident angle T1of the light is 0°, and the reflection characteristics U2aof light in the projection surface5awhen the incident angle T1of the light is 0°.FIG. 11shows the reflection characteristics U1bof light in the object7when the incident angle T1of the light is 20°, and the reflection characteristics U2bof light in the projection surface5awhen the incident angle T1of the light is 20°.FIG. 12shows the reflection characteristics U1cof light in the object7when the incident angle T1of the light is 40°, and the reflection characteristics U2cof light in the projection surface5awhen the incident angle T1of the light is 40°.FIG. 13shows the reflection characteristics U1dof light in the object7when the incident angle T1of the light is 60°, and the reflection characteristics U2dof light in the projection surface5awhen the incident angle T1of the light is 60°.

As shown inFIG. 10throughFIG. 13, when the projection surface5ahigh in light scattering characteristic is used, the reflection intensity T3of the object7becomes higher than the reflection intensity obtained by making the reflection intensity T3of the projection surface5a1.5 times irrespective of the incident angle T1as long as the observation angle T2is no smaller than 0° and no larger than 10°. The reflection intensity T3is proportional to the luminance in the imaging data. Therefore, when the observation angle T2is no smaller than 0° and no larger than 10°, the high luminance area exists in the taken image. Therefore, when the observation angle T2is no smaller than 0° and no larger than 10°, it is possible for the decision section45to identify the position of the object7based on the imaging data.

Therefore, when the projection surface5ahigh in light scattering characteristic is used, the user dispose the projection section104and the imaging section106so that the angle T2formed between a first straight line L1passing through the object7and the projection section104, and a second straight line L2passing through the object7and the imaging section106is within a range no smaller than 0° and no larger than 10° irrespective of the position of the object7in the projection surface5aas illustrated inFIG. 15. The range no smaller than 0° and no larger than 10° is an example of a predetermined angular range.

The first straight line L1is a straight line passing through the centroid of the object7and a principal point of the projection optical system in the projection section104. The principal point of the projection optical system13is a principal point of a lens constituting the projection optical system13. The first straight line L1is not limited to the straight line passing through the centroid of the object7and the principal point of the projection optical system13, but can also be, for example, a straight line passing through a point the closest to the projection optical system13in an outer surface of the object7and the principal point of the projection optical system13.

The second straight line L2is a straight line passing through the centroid of the object7and a principal point of an optical system such as a lens in the imaging section106. The second straight line L2is not limited to the straight line passing through the centroid of the object7and the principal point of the optical system such as the lens in the imaging section106, but can also be, for example, a straight line passing through a point the closest to the imaging section106in the outer surface of the object7and the principal point of the optical system such as the lens in the imaging section106.

The angle T2formed between the first straight line L1and the second straight line L2means the observation angle T2. The shorter the distance between the projector1and the projection surface5ais, the larger the observation angle T2becomes. Therefore, the user adjusts the distance between the projector1and the projection surface5ato thereby set the observation angle T2within the range no smaller than 0° and no larger than 10°.

Further, the longer the distance between the projection section104and the imaging section106is, the larger the observation angle T2becomes. Therefore, when the distance between the projection section104and the imaging section106can be adjusted, for example, when there is adopted the configuration in which the imaging section106is separated from the projector1, the user adjusts the distance between the projection section104and the imaging section106to thereby set the observation angle12within the range no smaller than 0° and no larger than 10°. It should be noted that the range no smaller than 0° and no larger than 10° can arbitrarily be changed in accordance with the reflection characteristics of light by the object7and the degree of the light scattering characteristic in the projection surface5a.

When the projection section104and the imaging section106are disposed as described above, it is possible for the decision section45to identify the object7on the projection surface5airrespective of what position in the projection surface5ahigh in light scattering characteristic the object7is disposed at.

A7. Operation of Projector1

Then, an operation of the projector1disposed in such a manner as described above will be described.FIG. 16is a flowchart for explaining the operation of the projector1.

In order to set the projection area8ein the projection surface5a, the user disposes the object7on the projection surface5a. For example, when setting the entire surface of the projection surface5aas the projection area8e, the user disposes the objects7on the four corners of the projection surface5aone by one.

Subsequently, the user operates the operation receiving section101to thereby set the power of the projector1to an ON state. When the power of the projector1is set to the ON state, the projection control section41controls the light source drive section105to thereby put the light source11on in the step S1.

Subsequently, the user operates the operation receiving section101to input an adjustment start instruction of manually adjusting at least one of the posture of the projector1, the position of the projector1, and the position of the object7.

When the operation receiving section101receives the adjustment start instruction in the step S2, the projection control section41reads the guide image data from the storage section107. Subsequently, the projection control section41provides the guide image data to the image combining section102a. Subsequently, the projection control section41sets the correction amount of the keystone distortion correction in the distortion correction section102bto zero. The order of the processing of providing the image combining section102awith the guide image data and the processing of setting the correction amount of the keystone distortion correction to be zero can be reversed. When the operation receiving section101fails to receive the adjustment start instruction within a specified period of time in the step S2, the process can return to the step S1, or can return to the head of the step S2, or can be terminated.

Subsequently, the image processing section102generates the image signal based on the guide image data. Subsequently, the image processing section102provides the image signal to the light valve drive section103. The light valve drive section103generates the drive voltages based on the image signal. Subsequently, in the step S3, the projection section104projects the guide image E1on the projection surface5ain accordance with the drive voltages.

The user is prompted by the guide image E1, for example, prompted by the first message M1and the second message M2, to manually adjust the posture of the projector1, the position of the projector1, or the position of the object7. For example, the user manually adjusts the posture of the projector1, the position of the projector1, or the positions of the objects7so that the first object7ais located in the area Ka1, the second object7bis located in the area Kb1, the third object7cis located in the area Kc1, the fourth object7dis located in the area Kd1, and the second guide area F12is located on the projection surface5a.

When the user ends the manual adjustment according to the guide image E1, the user operates the operation receiving section101to thereby input an execution start instruction of starting an automatic adjustment of the shape of the projection image.

When the operation receiving section101receives the execution start instruction in the step S4, the projection control section41reads the projection position detecting image data from the storage section107. Subsequently, the projection control section41provides the projection position detecting image data to the image combining section102a. The image processing section102generates the image signal based on the projection position detecting image data. Subsequently, the image processing section102provides the image signal to the light valve drive section103. The light valve drive section103generates the drive voltages based on the image signal. It should be noted that when the operation receiving section101fails to receive the execution start instruction within a predetermined period of time in the step S4, the process can return to the step S1, or can return to the head of the step S4, or can be terminated.

Subsequently, in the step S5, the projection section104projects the projection position detecting image E2on the projection surface5ain accordance with the drive voltages based on the projection position detecting image data.

Subsequently, in the step S6, the imaging control section42makes the imaging section106take an image of the projection surface5aon which the projection position detecting image E2is projected. The imaging section106takes an image of the projection surface5ato thereby generate the imaging data.

In the step S6, the imaging control section42adjusts the exposure of the imaging section106so that, for example, a maximum luminance of the dots F2athrough F2drepresented by the imaging data falls within a predetermined luminance range, and then makes the imaging section106take the image of the projection surface5a.

Subsequently, in the step S7, the projection position detection section43executes the processing of detecting the positions of the respective dots F2athrough F2din the taken image represented by the imaging data.

In the step S7, the projection position detection section43first identifies the lowest luminance value in the taken image. Subsequently, the projection position detection section43adds a dot judgment luminance value to the lowest luminance value to thereby calculate a dot judgment threshold value. The dot judgment luminance value is a luminance value to be used for a dot judgment. Subsequently, the projection position detection section43identifies a high luminance portion exhibiting the luminance higher than the dot judgment threshold value in the taken image. Subsequently, the projection position detection section43detects a corresponding-sized high luminance portion having a size within a size range no smaller than a first predetermined size and no larger than a second predetermined size out of the light luminance portion as the dots F2athrough F2d. It should be noted that the second predetermined size is larger than the first predetermined size. The corresponding-sized high luminance portion is hereinafter referred to as a “dot part.”

In the step S7, the projection position detection section43further detects the centroid positions of the respective dot parts as the positions of the dots F2athrough F2d.

It is possible for the projection position detection section43to detect the centroid position of the dot part using a luminance distribution in the dot part. For example, the projection position detection section43weights each of the pixels constituting the dot part based on the luminance of the pixel to detects the centroid position in the dot part thus weighted.

It is possible for the projection position detection section43to detect the position of each of the dots F2athrough F2dusing a difference between the imaging data generated by the imaging section106which is set to the exposure value when generating dot imaging data in the situation in which the projection section104projects an entirely black image, and the dot imaging data. In this case, it becomes possible to prevent the environmental light from affecting the detection of the dots F2athrough F2d.

Subsequently, when any of the dots F2athrough F2dfail to be detected in the step S8, the projection control section41makes the brightness of the projection image darker than the present brightness in the step S9.

As the situation in which any of the dots F2athrough F2dfail to be detected in the step S8, there can be assumed a situation in which, for example, the posture of the projector1has changed due to the own weight of the projector1, and therefore, any of the dots F2athrough F2drun off the projection surface5a. In this situation, even when making the dots F2athrough F2dbright, it is difficult to detect all of the dots F2athrough F2d.

Therefore, when the brightness of the projection image when it is judged that the dots F2athrough F2dare not detected is assumed as 100%, the projection control section41sets the brightness of the projection image to the brightness lower than 100% in the step S9. For example, in the step S9, the projection control section41sets the brightness of the projection image to the brightness of 30%. The brightness lower than 100% is not limited to the brightness of 30%. For example, the brightness lower than 100% can be the brightness of 0%. The brightness of 0% means to stop the projection of the projection image. It is possible for the projection control section41to make the projection image inconspicuous by making the projection image projected in a shifted state with respect to the projection image5adark. When the step S9terminates, the process returns to the step S1.

In contrast, when the dots F2athrough F2dare detected in the step S8, the coordinate adjustment section44calculates the projective transformation matrix for transforming the camera coordinate system into the liquid crystal panel coordinate system using the dots F2athrough F2din the step S10.

In the step S10, the coordinate adjustment section44first identifies the centroid coordinate in the liquid crystal panel coordinate system of each of the dots F2athrough F2dbased on the projection position detecting image data. Subsequently, the coordinate adjustment section44calculates the projective transformation matrix based on a positional relationship between the centroid coordinate in the liquid crystal panel coordinate system of each of the dots F2athrough F2d, and the centroid coordinate in the camera coordinate system of each of the dots F2athrough F2d. Subsequently, the coordinate adjustment section44stores the projective transformation matrix in the storage section107.

Subsequently, the projection control section41reads the object detecting image data from the storage section107. Subsequently, the projection control section41provides the object detecting image data to the image combining section102a. The image processing section102generates the image signal based on the object detecting image data. Subsequently, the image processing section102provides the image signal to the light valve drive section103. The light valve drive section103generates the drive voltages based on the image signal.

Subsequently, in the step S11, the projection section104projects the object detecting image E3on the projection surface5ain accordance with the drive voltages based on the object detecting image data.

Subsequently, in the step S12, the imaging control section42makes the imaging section106take an image of the projection surface5aon which the object detecting image E3is projected. The imaging section106takes an image of the projection surface5ato thereby generate the imaging data. It should be noted that in the step S12, the imaging control section42adjusts the exposure of the imaging section106so that the luminance of the patterns F3athrough F3dof the object detecting image E3falls within a predetermined luminance range similarly when imaging the projection position detecting pattern, and then makes the imaging section106take the image of the projection surface5a.

The projection section104and the imaging section106are disposed as described above. Therefore, whatever areas in the projection surface5aare irradiated with the object detecting pattern F3, it is possible for the decision section45to detect the object7located in that area.

When the imaging section106takes the image of the projection surface5aon which the object detecting image E3is projected to thereby generate the imaging data, the decision section45executes the processing of detecting the object7based on the imaging data in the step S13.

In the step S13, the decision section45first identifies the high luminance area in the taken image. Subsequently, when an area surrounded by the high luminance area exists in the taken image, the decision section45decides the area identified by adding the high luminance area to the area surrounded by the high luminance area as the object area. Subsequently, the decision section45detects the centroid position in the object area as the centroid position of the object7for each of the object areas.

It is desirable for the object7to have a shape and reflection characteristics with which the detection accuracy of the centroid position becomes high. For example, it is desirable for the object7to have a circular shape in a plan view, and have the reflection characteristics in which the closer to the centroid position, the higher the reflectance is. The shape of the object7is not limited to the circular shape, but can be a spherical shape.

It is possible for the decision section45to detect the position of the object7using a difference between the imaging data generated by the imaging section106which is set to the exposure value when generating the imaging data of the object7in the situation in which the projection section104projects an entirely black image similarly to the above, and the imaging data of the object7. In this case, it becomes possible to prevent the environmental light from affecting the detection of the object7.

The position of the object7is not limited to the centroid position of the object7. For example, when the object7has a polygonal shape such as a quadrangular shape or an L shape, it is possible to use a vertex of the object7, an edge of the object7, or a corner of the object7as the position of the object7. When the object7has a solid three-dimensional shape, it is possible for the decision section45to obtain the position of the object7taking the offset amount corresponding to the thickness into consideration.

Subsequently, when the object7, furthermore, the centroid position of the object7, fails to be detected in the step S14, the step S9is executed.

In contrast, when the object7, furthermore, the centroid position of the object7, is detected in the step S14, the decision section45calculates the position information representing the position of the projection range in the liquid crystal panel coordinate system as the correction amount of the keystone distortion correction in the distortion correction section102bin the step S15.

Here, the projection range in the liquid crystal panel coordinate system is a range in which the image to be projected in the entire area of the projection area8eor a part of the projection area8eout of the pixel area12aof the liquid crystal light valve12. The area in which the image to be projected in the entire area of the projection area8eout of the pixel area12ais generated is hereinafter referred to as a “specified area.”

In the step S15, the decision section45transforms the position of the object7on the taken image to which the camera coordinate system is adopted into the coordinate position in the liquid crystal panel coordinate system using the projective transformation matrix generated in the step S10. Subsequently, the decision section45decides, for example, a quadrangular area having the positions of the four objects7on the liquid crystal light valve12as the vertexes, namely the specified area, as the projection range.

It should be noted that it is possible for the decision section45to calculate the projection range so that an outer edge of the generation image is located at the inner side than the outer edge of the specified area without overlapping the object area.

For example, the decision section45first generates the projective transformation matrix for the keystone distortion correction used to transform the positions of the four corners of the pixel area12ain the liquid crystal coordinate system into the positions of the four corners of the specified area in the liquid crystal panel coordinate system. Subsequently, the decision section45calculates the corrected position distant as much as a predetermined offset amount from the position of the corner toward the central position of the pixel area12afor each of the positions of the four corners of the pixel area12ain the liquid crystal panel coordinate system. Subsequently, the decision section45transforms the correction positions of the positions of the four corners of the pixel area12ainto the positions of the four corners of the projection range included in the specified area using the projective transformation matrix for the keystone distortion correction.

It should be noted that the method of calculating the projection range included in the specified area is not limited to the method described above, but can arbitrarily be changed. For example, a reduction operation for reducing a magnification ratio of the specified area in order to set the projection range included in the specified area can be performed using an OSD (On Screen Display) menu, or the reduction operation can be performed with a remote controller. Subsequently, the decision section45sets the positional information of the projection range to the distortion correction section102b.

Subsequently, in the step S16, when the positional information of the projection range is set, the distortion correction section102bperforms the keystone distortion correction on the output of the image combining section102abased on the positional information.

It is conceivable when the posture of the projector1changes due to the own weight of the projector1or the like as described above after the execution of the step S16. In this case, the projection image after the keystone distortion correction runs off the projection area8e. Therefore, when a predetermined period of time elapses in the step S17from when the step S16is completed, the process returns to the step S5.

In the step S17, in the situation in which the predetermined period of time does not elapse from when the step S16is completed, when the operation receiving section101does not receive the termination operation in the step S18, the process returns to the step S17, and when the operation receiving section101has received the termination operation in the step S18, the process terminates.

A8. Projection Image after Keystone Distortion Correction

FIG. 17is a diagram showing an example of a post-keystone distortion correction projection image P which is projected after the keystone distortion correction is performed in the step S16. The post-keystone distortion correction projection image P is an example of the display image E4. InFIG. 17, the keystone distortion correction is performed so that the outer edge of the post-keystone distortion correction projection image P coincides with the outer edge of the projection area8e.

As illustrated inFIG. 18, the keystone distortion correction can be performed so that the whole of the post-keystone distortion correction projection image P falls within the projection area8e, and at the same time, an area where the post-keystone distortion correction projection image P does not exist out of the projection area8eexists.

As illustrated inFIG. 19, it is possible to perform the keystone distortion correction of fitting the projection image into the projection area8ewhile keeping the aspect ratio of the projection image based on the image data. In this case, it becomes possible to suppress the disturbance in the aspect ratio of the post-keystone distortion correction projection image P.

When such a keystone distortion correction as illustrated inFIG. 18orFIG. 19is performed, the area where the post-keystone distortion correction projection image P does not exist in the projection area8eis displayed with, for example, a black color.

It is desirable to make it possible for the user to select the setting regarding the disposition of the post-keystone distortion correction projection image P with respect to the projection area8eusing a menu operation or the like.

The projection system1000, the method of controlling the projector1, and the projector1according to the present disclosure described above include the following aspects.

The object7is the recursive reflector located in an area Ka of the projection surface5a. The projection section104projects the object detecting image E3and the display image E4at respective timings different from each other. The imaging section106takes an image of the projection surface5ain the situation in which the projection section104projects the object detecting image E3on the projection surface5ato thereby generate the imaging data. The decision section45identifies the position of the object7based on the imaging data to decide the projection area8ein which the display image is projected based on the position of the object7. The projection section104and the imaging section106are disposed so that the value obtained by dividing the luminance of the object7represented by the imaging data by the luminance of the projection surface5arepresented by the imaging data becomes no lower than the threshold value greater than 1.

According to this aspect, no matter what position in the projection surface5athe object7is disposed at, the luminance of the object7becomes higher than the luminance of the projection surface5ain the imaging data. Therefore, it is possible for the decision section45to identify the position of the object7based on the difference in luminance. Therefore, setting of the projection area8eusing the object7becomes possible.

The projection section104and the imaging section106are disposed so that the observation angle T2as the angle formed between the first straight line L1passing through the object7and the projection section104and the second straight line L2passing through the object7and the imaging section106becomes within the predetermined angular range, for example, within the range no smaller than 0° and no larger than 10°.

According to this aspect, no matter what position in the projection surface5athe object7is disposed at, it is possible for the decision section45to identify the position of the object7based on the imaging data. For example, when the projection surface5ahigh in light scattering characteristic is used, as long as the observation angle T2is no smaller than 0° and no larger than 10°, no matter what position in the projection surface5athe object7is disposed at, it is possible for the decision section45to identify the position of the object7based on the imaging data.

The projection section104projects the guide image E1representing the area Ka before projecting the object detecting image E3. According to this aspect, it is possible for the user to easily dispose the object7in the area Ka. Therefore, the probability that the imaging data represents the object7increases. Therefore, it is possible for the decision section45to identify the position of the object7based on the imaging data.

The area Ka is set so that the value obtained by dividing the luminance of the object7in the area Ka represented by the imaging data by the luminance of the projection surface5arepresented by the imaging data becomes higher than the threshold value. Therefore, no matter what position in the area Ka the object7is disposed at, it is possible for the decision section45to identify the position of the object7based on the imaging data. Therefore, setting of the projection area8eusing the object7becomes possible.

B. Modified Examples

It is possible to make such a variety of modifications as described below on the embodiment described above. Further, it is also possible to arbitrarily combine one or more modifications arbitrarily selected from the aspects of the modifications described below.

B1. First Modified Example

In the first embodiment, there is used the projection surface5ahigh in light scattering characteristic. However, it is possible to use a projection surface high in specular reflection characteristic as the projection surface5a.FIG. 20throughFIG. 23are each a diagram showing the reflection characteristics U1of light in the object7, and reflection characteristics U3of light in the projection surface5ahigh in specular reflection characteristic. The projection surface5ahigh in specular reflection characteristic is, for example, a whiteboard.

FIG. 20shows the reflection characteristics U1aof light in the object7when the incident angle T1of the light is 0°, and the reflection characteristics U3aof light in the projection surface5awhen the incident angle T1of the light is 0°.

FIG. 21shows the reflection characteristics U1bof light in the object7when the incident angle T1of the light is 20°, and the reflection characteristics U3bof light in the projection surface5awhen the incident angle T1of the light is 20°.

FIG. 22shows the reflection characteristics U1cof light in the object7when the incident angle T1of the light is 40°, and the reflection characteristics U3cof light in the projection surface5awhen the incident angle T1of the light is 20°.

FIG. 23shows the reflection characteristics U1dof light in the object7when the incident angle T1of the light is 60°, and the reflection characteristics U3dof light in the projection surface5awhen the incident angle T1of the light is 20°.

InFIG. 20throughFIG. 23, the horizontal axis represents an observation angle T2, and the vertical axis represents reflection intensity T3. The scale of the vertical axis inFIG. 20throughFIG. 23is different from the scale of the vertical axis inFIG. 10throughFIG. 13. Here, the fact that the specular reflection characteristic is high means that the incident angle T1is equal or substantially equal to the reflection angle.

As shown inFIG. 20, when the projection surface5ahigh in specular reflection characteristic is used, when both of the incident angle T1and the observation angle T2are 0°, the reflection intensity T3of the projection surface5arises, and thus, the difference in reflection intensity T3between the projection surface5aand the object7decreases. Therefore, in the imaging data, the difference in luminance between the object7and the projection surface5adecreases. Therefore, there is a possibility that it becomes unachievable for the decision section45to detect the position of the object7based on the imaging data.

In contrast, as shown inFIG. 20throughFIG. 23, even when the projection surface5ahigh in specular reflection characteristic is used, when the observation angle T2is no smaller than 2° and no larger than 10°, the value obtained by dividing the reflection intensity T3of the object7by the reflection intensity T3of the projection surface5abecomes no lower than a threshold value.

The higher the reflection intensity T3of the object7is, the higher the luminance of the object7represented by the imaging data becomes, and the higher the reflection intensity T3of the projection surface5ais, the higher the luminance of the projection surface5arepresented by the imaging data becomes.

Therefore, when the observation angle T2is no smaller than 2° and no larger than 10°, the value obtained by dividing the luminance of the object7represented by the imaging data by the luminance of the projection surface5arepresented by the imaging data becomes no lower than the threshold value.

Therefore, when the projection surface5ahigh in specular reflection characteristic is used, the user disposes the projection section104and the imaging section106so that the observation angle T2as the angle formed between the first straight line L1passing through the object7and the projection section104and the second straight line L2passing through the object7and the imaging section106becomes within the range no smaller than 2° and no larger than 10°.

For example, the user adjusts the distance between the projector1and the projection surface5aand the posture of the projector1with respect to the projection surface5ato thereby set the observation angle T2within the range no smaller than 2° and no larger than 10°.

According to this aspect, even when the projection surface5ahigh in specular reflection characteristic is used, it is possible for the decision section45to identify the position of the object7based on the imaging data.

Further, the longer the distance between the projection section104and the imaging section106is, the larger the observation angle T2becomes. Therefore, when the distance between the projection section104and the imaging section106can be adjusted, for example, when there is adopted the configuration in which the imaging section106is separated from the projector1, the user adjusts the distance between the projection section104and the imaging section106and the posture of the projector1with respect to the projection surface5ato thereby set the observation angle T2within the range no smaller than 2° and no larger than 10°.

It should be noted that the range no smaller than 2° and no larger than 10° can arbitrarily be changed in accordance with the reflection characteristics of light by the object7and the degree of the specular reflection characteristic in the projection surface5a.

Further, as shown inFIG. 21throughFIG. 23, when the incident angle T1is within a range no smaller than 20° and no larger than 60°, the reflection intensity T3becomes substantially constant even in the projection surface5ahigh in specular reflection characteristic.

Therefore, when the projection surface5ahigh in specular reflection characteristic is used, the user disposes the projection section104and the imaging section106so that the observation angle T2as the angle formed between the first straight line L1passing through the object7and the projection section104and the second straight line L2passing through the object7and the imaging section106becomes within the range no smaller than 0° and no larger than 10°, and the incident angle T1as the angle formed between a normal line n of the projection surface5aand the first straight line L1becomes within the range no smaller than 20° and no larger than 60°.

For example, the user adjusts the distance between the projector1and the projection surface5aand the posture of the projector1with respect to the projection surface5ato thereby set the observation angle T2within the range no smaller than 0° and no larger than 10°, and at same time set the incident angle T1within the range no smaller than 20° and no larger than 60°.

According to this aspect, even when the projection surface5ahigh in specular reflection characteristic is used, it is possible for the decision section45to identify the position of the object7based on the imaging data.

Further, the longer the distance between the projection section104and the imaging section106is, the larger the observation angle T2becomes. Therefore, when the distance between the projection section104and the imaging section106can be adjusted, for example, when there is adopted the configuration in which the imaging section106is separated from the projector1, the user adjusts the distance between the projection section104and the imaging section106and the posture of the projector1with respect to the projection surface5ato thereby set the observation angle T2within the range no smaller than 0° and no larger than 10°, and at same time set the incident angle T1within the range no smaller than 20° and no larger than 60°.

According to this aspect, even when the projection surface5ahigh in specular reflection characteristic is used, it is possible for the decision section45to identify the position of the object7based on the imaging data.

It should be noted that the range no smaller than 0° and no larger than 10° and the range no smaller than 20° and no larger than 60° can arbitrarily be changed in accordance with the reflection characteristics of light by the object7and the degree of the specular reflection characteristic in the projection surface5a.

FIG. 24is a diagram showing an area in which the object7can be identified based on the imaging data when the projector1as an ultrashort focus projector incorporating the imaging section106is installed in the following projection optical conditions. The projection optical conditions are the slow ratio=0.27, the offset=9.68:−1, the aspect ratio=16:9, and the projection area=65 inches. The condition of identifying the object7is that the luminance of the object is no lower than the luminance obtained by making the luminance of the projection surface5a1.5 times in the imaging data.

InFIG. 24, the distance between the projection section104and the imaging section106is set to 13.8 cm. The projection surface5ahas an unidentifiable area5a2in which the object7cannot be identified in addition to an identifiable area5a1in which the object7can be identified. It should be noted that the unidentifiable area5a2shown inFIG. 24is an area in which the observation angle T2is larger than 10°.

In this case, it is sufficient for the user to set the area in which the object7should be disposed in the identifiable area Sal. For example, the user sets an area which does not include the identifiable area5a2out of the areas on the four corners of the projection surface5aas the area in which the object7should be disposed.

It is possible for the user to dissolve the unidentifiable area5a2by increasing the distance between the projector1and the projection surface5a.

Further, it is possible for the user to dissolve the unidentifiable area5a2by decreasing the distance between the projection section104and the imaging section106.FIG. 25shows an example in which the unidentifiable area5a2is dissolved by decreasing the distance between the projection section104and the imaging section106from 13.8 cm to 7.0 cm. In the projection optical condition described above, it is desirable for the distance between the projection section104and the imaging section106to be not longer than 7.0 cm.

In a projection optical condition different from the projection optical condition described above such as a condition that the slow ratio is higher than 0.27 or a condition that the offset approximates zero, when the distance between the projection section104and the imaging section106decreases, the observation angle T2and the incident angle T1come closer to 0°. Therefore, when the projection surface5ais the projection surface high in specular reflection characteristic, due to an influence of the specular reflection, the condition for identifying the object is not fulfilled.

In this case, the user changes the positional relationship of the projection section104and the imaging section106with respect to the projection surface5aso that the observation angle T2becomes within the range no smaller than 2° and no larger than 10°, or changes the positional relationship of the projection section104and the imaging section106with respect to the projection surface5aso that the incident angle T1becomes within the range no smaller than 20° and no larger than 60°.

B2. Second Modified Example

In the first embodiment and the first modified example, it is possible for the projection section104to project the four dots F2athrough F2din the vicinity of the position of the object7for each of the objects7, and it is possible for the coordinate adjustment section44to generate the projective transformation matrix using the dots F2athrough F2dlocated in the vicinity of the object7for each of the objects7. In this case, from a local point of view, it becomes possible to reduce the influence of the distortion of the lens of the imaging section106. In this case, the number of dots to be projected in the vicinity of the position of the object7can also be larger than 4.

B3. Third Modified Example

In the first embodiment and the first modified example through the second modified example, the recursive reflector used as the object7can be provided with the recursive reflection characteristic with respect to visible light, or can be provided with the recursive reflection characteristic with respect to nonvisible light such as infrared light. When the recursive reflector having the recursive reflection characteristic with respect to visible light is used as the object7, the object detecting pattern F3is constituted by light including the visible light. When the recursive reflector having the recursive reflection characteristic with respect to nonvisible light is used as the object7, the object detecting pattern F3is constituted by light including the nonvisible light.

B4. Fourth Modified Example

In the first embodiment and the first modified example through the third modified example, the positions of the four objects7are not limited to the four corners of the projection surface5a. For example, the position of each of the four objects7can be a position at the inner side of the corner of the projection surface5a.

B5. Fifth Modified Example

In the first embodiment and the first modified example through the fourth modified example, the number of the objects7is not limited to 4, but is sufficiently one or more. For example, when an object7ghaving a shape surrounding the projection area8ehaving a rectangular shape is used as shown inFIG. 26, it is sufficient for the number of the objects7to be 1. In this case, the user adjusts either one or both of the position of the guide image E1and the position of the object7gso that each of the four corners of the object7gis located in a first guide area F11in the guide image E1. In this aspect, since the projection area8ecan be set by the single object7, it becomes easy to set the projection area8ecompared to when setting the projection area8eusing the four objects7.

Further, when an object7hshaped like a straight line defining the right side of the projection area8e, and an object7I shaped like a straight line defining the left side of the projection area8eare used as shown inFIG. 27, it is sufficient for the number of the objects7to be 2. In this case, the user adjusts at least one of the position of the guide image E1, the position of the object7h, and the position of the object7I so that an end7h1of the object7his located in the upper right area Fla, the other end7h2of the object7his located in the lower right area F1b, one end7I1of the object7I is located in the lower left area F1c, and the other end7I2of the object7I is located in the upper left area F1d. In this aspect, since the projection area8ecan be set by the two objects7, it becomes easy to set the projection area8ecompared to when setting the projection area8eusing the four objects7.

B6. Sixth Modified Example

In the first embodiment and the first modified example through the fifth modified example, in the guide image E1, the whole or a part of the first message M1and the second message M2can be omitted. Further, in the guide image E1, the second guide area F12can be omitted together with the second message M2.

B7. Seventh Modified Example

In the first embodiment and the first modified example through the sixth modified example, the range of the first guide area F11can be a movable range in which the four corners of the projection image can be moved by the distortion correction section102bperforming the keystone distortion correction, or can be a range included in the movable range.

B8. Eighth Modified Example

In the first embodiment and the first modified example through the seventh modified example, when the projection position detecting pattern F2is performed using nonvisible light such as infrared light, the second guide area F12and the second message M2is omitted from the guide image E1. When the projection position detecting pattern F2is performed using the nonvisible light such as the infrared light, since the projection position detecting pattern F2is not recognized by the user, it becomes possible to execute the step S5while the user is unaware of the execution. When the object detecting pattern F3is performed using the nonvisible light such as the infrared light, since the object detecting pattern F3is not recognized by the user, it becomes possible to execute the step S11while the user is unaware of the execution.

B9. Ninth Modified Example

In the first embodiment and the first modified example through the eighth modified example, a movable surface such as an elevator door can be used as the projection surface5a. In this case, for example, when the elevator door on which the object7is located opens, it becomes possible to make the projection image darker, or to stop the projection of the projection image.

B10. Tenth Modified Example

In the first embodiment and the first modified example through the ninth modified example, it is possible for the object7to be fixed to the projection surface5awith a magnetic force or an adhesion member. It should be noted that the method of fixing the object7to the projection surface5acan arbitrarily be changed.

B11. Eleventh Modified Example

In the first embodiment and the first modified example through the tenth modified example, when the storage section107stores the image data, it is possible for the image combining section102ato use the image data stored by the storage section107instead of the received image data.

B12. Twelfth Modified Example

In the first embodiment and the first modified example through the eleventh modified example, in the projection section104, there are used the liquid crystal light valves as the light modulation device. However, the light modulation device is not limited to the liquid crystal light valves. For example, it is also possible for the light modulation device to have a configuration using three reflective liquid crystal panels. It is possible for the light modulation device to have a configuration such as a system having a single liquid crystal panel and a color wheel combined with each other, a system using three digital mirror devices, or a system having a single digital mirror device and a color wheel combined with each other. When the light modulation device is just one liquid crystal panel or just one digital mirror device, the members corresponding to the color separation optical system and the color combining optical system are unnecessary. Further, besides the liquid crystal panel or the digital mirror device, any configurations capable of modulating the light emitted by the light source can be adopted as the light modulation device.

B13. Thirteenth Modified Example

In the first embodiment and the first modified example through the twelfth modified example, the step S9can be omitted.