Correction method, projector, and program

Abstract

To reduce a situation where geometric correction frequently changes unintentionally.SOLUTION: A correction method includes: when a projection angle that is an angle formed by a horizontal plane and a projection direction of a projector is an angle within a first range, applying first geometric correction for correcting distortion of an image projected on a first projection surface from the projector; when the projection angle is an angle within a second range different from the first range, applying second geometric correction for correcting distortion of an image projected, from the projector, on a second projection surface intersecting the first projection surface; when the projection angle changes from the angle within the first range to an angle within a third range that is a range between the first range and the second range, applying the first geometric correction; and when the projection angle changes from the angle within the second range to the angle within the third range, applying the second geometric correction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a correction method, a projector, and a program. [Background technology]

[0002] For example, Patent Document 1 describes a projection device that can change the projection direction of a projection unit that converts image data into light and projects it. The projection device described in Patent Document 1 measures the distance to a projection medium onto which the projection unit projects light, obtains a first direction perpendicular to the projection medium based on the measured distance, and performs image processing on the image data according to a second direction obtained by correcting the projection direction of the projection unit using the first direction. Here, the distortion correction coefficient used for correction is switched before and after the projection angle to the intersection line of two projection mediums that intersect with each other, such as a wall and a ceiling. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-150380 Summary of the Invention [Problem to be solved by the invention]

[0004] In the projection device described in Patent Document 1, when projecting near the intersection line of two intersecting projection media, there is a risk that the distortion correction coefficients will be switched frequently. [Means for solving the problem]

[0005] A correction method according to one embodiment of the present disclosure includes applying a first geometric correction to correct distortion of an image projected from the projector onto a first projection surface when a projection angle, which is an angle between a horizontal plane and a projection direction of the projector, is within a first range; applying a second geometric correction to correct distortion of an image projected from the projector onto a second projection surface that intersects with the first projection surface when the projection angle is within a second range different from the first range; applying the first geometric correction when the projection angle changes from the first range to an angle within a third range that is a range between the first range and the second range; and applying the second geometric correction when the projection angle changes from the second range to an angle within the third range.

[0006] A projector according to one embodiment of the present disclosure includes an optical device and at least one processor that performs the following operations: applying a first geometric correction to correct distortion of an image projected from the optical device onto a first projection surface when a projection angle, which is the angle between a horizontal plane and a projection direction of the optical device, is within a first range; applying a second geometric correction to correct distortion of an image projected from the optical device onto a second projection surface that intersects with the first projection surface when the projection angle is within a second range different from the first range; applying the first geometric correction when the projection angle changes from the first range to an angle within a third range that is a range between the first range and the second range; and applying the second geometric correction when the projection angle changes from the second range to an angle within the third range.

[0007] A program according to one embodiment of the present disclosure causes at least one processor to perform the following: apply a first geometric correction to correct distortion of an image projected from the projector onto a first projection surface when a projection angle, which is the angle between a horizontal plane and the projection direction of the projector, is an angle within a first range; apply a second geometric correction to correct distortion of an image projected from the projector onto a second projection surface that intersects with the first projection surface when the projection angle is an angle within a second range different from the first range; apply the first geometric correction when the projection angle changes from the first range to an angle within a third range that is a range between the first range and the second range; and apply the second geometric correction when the projection angle changes from the second range to an angle within the third range. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an outline of a system used in a correction method according to a first embodiment. [Figure 2] FIG. 1 is a block diagram of a projector according to a first embodiment. [Figure 3] 4 is a flowchart showing the flow of a correction method according to the first embodiment. [Figure 4] FIG. 4 is an explanatory diagram of switching of geometric correction in the first embodiment. [Figure 5] FIG. 10 is an explanatory diagram of correction values. [Figure 6] 10 is a flowchart illustrating an example of a method for calculating a correction value. [Figure 7] FIG. 10 is an explanatory diagram of switching of geometric correction in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Preferred embodiments of the present disclosure will be described below with reference to the accompanying drawings. Note that the dimensions and scale of each part in the drawings may differ from the actual dimensions and are shown schematically to facilitate understanding. Furthermore, the scope of the present disclosure is not limited to these embodiments unless otherwise specified in the following description to the effect that the present disclosure is limited. 1. First embodiment 1-1. Overview of the system used for the correction method 1 is a diagram showing an outline of a system 100 used in a correction method according to the first embodiment. As shown in FIG.

[0010] The projector 10 is a display device that projects an image G represented by image information output from a device such as a computer (not shown) onto a projection surface SC.

[0011] The attitude of the projector 10 or the optical device 15 described below about the axis AX can be changed. The axis AX is an axis perpendicular to the direction in which the projector 10 projects the image G. Therefore, the rotation of the projector 10 or the optical device 15 described below about the axis AX changes the projection angle θ, which is the angle between the horizontal plane H and the projection direction of the projector 10, described below. The projection direction is, for example, the direction from the projector 10 to the projection surface SC of the center line of the image light emitted by the projector 10.

[0012] The method for changing the attitude of the projector 10 is not particularly limited, but may include, for example, a method using a platform that supports the projector 10 or the optical device 15 (described later) rotatably around the axis AX. As an example, the platform includes a base that is placed on the installation surface and a pair of support columns that are connected to the base. The projector 10 is placed between the pair of support columns and connected to a rotation mechanism provided at the tip of each support column. This supports the projector 10 so that it can rotate around the axis AX. The rotation mechanism includes, for example, a shaft provided on one of the projector 10 and the support column, and a bearing provided on the other of the projector 10 and the support column that rotatably supports the shaft. The structure of the platform is not limited to this, and a support plate on which the projector 10 is placed may also be rotated by a similar rotation mechanism.

[0013] The projector 10 can project an image G onto any one of the projection surfaces SC-1, SC-2, SC-3, and SC-4 by changing the position of the projector 10 around the axis AX. The projection surface SC-1 is an example of a "first projection surface," and the projection surface SC-2 is an example of a "second projection surface." For convenience of illustration, the projection surface SC-3 is not shown in FIG. 1. Hereinafter, the projection surfaces SC-1, SC-2, SC-3, and SC-4 may be referred to as the projection surface SC without distinction.

[0014] Projection surface SC-1 is a surface parallel to the vertical direction, such as a wall surface or a surface such as a screen aligned with the wall surface. Projection surface SC-2 intersects with projection surface SC-1 and is preferably a surface perpendicular to the vertical direction, such as a ceiling surface or a surface such as a screen aligned with the ceiling. Projection surface SC-3 is a surface that intersects with projection surface SC-2 and faces projection surface SC-1, such as a wall surface or a surface such as a screen aligned with the wall. Projection surface SC-4 is a surface that intersects with projection surfaces SC-1 and SC-3 and faces projection surface SC-2, such as a floor surface or a surface such as a screen aligned with the floor. Note that each of projection surfaces SC-1, SC-2, SC-3, and SC-4 does not need to be strictly flat, but from the viewpoint of simplifying the process of geometric correction of image G, it is preferable that the surfaces be surfaces that can be regarded as flat.

[0015] The projector 10 corrects distortion of the image G caused by the orientation of the projector 10 around the axis AX by geometric correction such as keystone correction. In the geometric correction, for example, if the shape of the image G to be projected is rectangular, the shape of the image G that is actually projected is corrected to be rectangular.

[0016] As will be described in more detail later, projector 10 is equipped with sensor 17, and has the function of using sensor 17 to measure the position and orientation of projector 10 relative to projection surface SC, and the function of determining correction values ​​for geometric correction of image G based on the results of that measurement.

[0017] 1-2.Projector Fig. 2 is a block diagram of a projector 10 according to the first embodiment. As shown in Fig. 2, the projector 10 includes a storage device 11, a processing device 12, a communication device 13, an image processing circuit 14, an optical device 15, an operation device 16, and a sensor 17. These are connected to each other so as to be able to communicate with each other.

[0018] The storage device 11 is a storage device that stores programs executed by the processing device 12 and data processed by the processing device 12. The storage device 11 includes, for example, a hard disk drive or a semiconductor memory. Note that part or all of the storage device 11 may be provided in an external storage device or server outside the projector 10.

[0019] The storage device 11 stores a program PR1, variable information PA, and correction value information DC.

[0020] The program PR1 is a program for executing a correction method, which will be described in detail later.

[0021] The variable information PA is information indicating a variable of an arithmetic formula used for geometric correction of the image G, and indicates the degree of geometric correction of the image G. The variable relates to at least one of the installation angle of the projection surface SC, the normal vector of the projection surface SC, and the attitude of the projector 10. In other words, the variable is a variable that indicates the angle between the projection surface SC and the projection direction.

[0022] The correction value information DC is information indicating correction values ​​for geometric correction of image G. The correction values ​​are, for example, coordinate values ​​of four corners of image G. The coordinate values ​​are, for example, coordinate values ​​of a display coordinate system set in optical device 15 (described later) or a coordinate system associated therewith.

[0023] The processing device 12 has the function of controlling each part of the projector 10 and the function of processing various data. The processing device 12 includes at least one processor such as a CPU (Central Processing Unit). Note that some or all of the functions of the processing device 12 may be realized by hardware such as a DSP (Digital Signal Processor), ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), or FPGA (Field Programmable Gate Array). The processing device 12 may also be integrated with the image processing circuit 14.

[0024] The communication device 13 is a communication device capable of communicating with various devices and acquires video data IMG from devices not shown. For example, the communication device 13 is a wired communication device such as a wired LAN (Local Area Network), USB (Universal Serial Bus), or HDMI (High Definition Multimedia Interface), or a wireless communication device such as LPWA (Low Power Wide Area), wireless LAN including Wi-Fi, or Bluetooth. "HDMI," "Wi-Fi," and "Bluetooth" are all registered trademarks.

[0025] The image processing circuit 14 performs necessary processing on the video data IMG from the communication device 13 and inputs the data to the optical device 15. The image processing circuit 14 may include, for example, one or more processors such as a CPU, or may include hardware such as a DSP, ASIC, PLD, or FPGA. The image processing circuit 14 may have, for example, a frame memory (not shown), and may load the video data IMG into the frame memory, appropriately perform various processes such as resolution conversion, resizing, and distortion correction, and input the data to the optical device 15. Here, correction value information DC is used for geometric correction, including distortion correction. Note that the image processing circuit 14 may also perform processes such as OSD (On Screen Display) processing, which generates image information for menu display or operation guides, etc., and combines the image information with the video data IMG, as needed.

[0026] The optical device 15 is a device that projects image light onto a projection surface SC to display an image G. The optical device 15 has a light source 15a, a light modulator 15b, and a projection optical system 15c.

[0027] The light source 15a includes a light source such as a halogen lamp, a xenon lamp, an ultra-high pressure mercury lamp, an LED (Light Emitting Diode), or a laser light source, and emits red, green, and blue light, respectively. The light modulator 15b includes three light modulation elements corresponding to red, green, and blue. Each light modulation element includes, for example, a transmissive liquid crystal panel, a reflective liquid crystal panel, or a DMD (Digital Micromirror Device), and generates image light of each color by modulating light of the corresponding color. The image light of each color generated by the light modulator 15b is combined by a color combining optical system to become full-color image light. The projection optical system 15c is an optical system including a projection lens and the like that forms and projects the full-color image light from the light modulator 15b onto a projection surface SC.

[0028] The operation device 16 is a device that accepts operations from the user. For example, the operation device 16 includes an operation panel and a remote control receiver, not shown. The operation panel is provided on the exterior housing of the projector 10, and outputs a signal based on an operation from the user. The remote control receiver receives an infrared signal from a remote control, not shown, decodes the infrared signal, and outputs a signal based on the operation of the remote control. The operation device 16 may be provided as needed, or may be omitted.

[0029] Sensor 17 is a sensor for estimating the relative position and attitude of projector 10 with respect to projection surface SC. Sensor 17 includes distance sensor 17a and acceleration sensor 17b. Distance sensor 17a is a time-of-flight (ToF) distance sensor that measures the distance between each part of projection surface SC and projector 10. In other words, distance sensor 17a measures the shape of projection surface SC. Acceleration sensor 17b is a sensor that detects acceleration on three mutually orthogonal axes, and detects the acceleration applied to projector 10.

[0030] 2 as long as it can obtain the detection results necessary to estimate the relative position and orientation of projector 10 with respect to projection surface SC, and for example, it may be an embodiment in which one of distance sensor 17a and acceleration sensor 17b is omitted, or an embodiment in which an inertial sensor such as an angular velocity sensor and a camera are provided instead of one or both of distance sensor 17a and acceleration sensor 17b. However, the detection results necessary to estimate the relative position and orientation of projector 10 with respect to projection surface SC differ depending on the calculation method of geometric correction, etc., and are not particularly limited.

[0031] In the above-described projector 10, the processing device 12 executes the program PR1 stored in the storage device 11, thereby performing various processes required for the correction method described below.

[0032] 1-3. Correction method 3 is a flowchart showing the flow of the correction method according to the first embodiment. As shown in FIG. 3, the correction method according to this embodiment includes steps S10 to S70. Here, the program PR1 causes the processing device 12 to execute steps S10 to S70. The processing device 12 and the image processing circuit 14 are examples of a "computer" and include at least one processor that executes steps S10 to S70.

[0033] First, in step S10, the processing device 12 acquires the gravitational acceleration acting on the projector 10 based on the detection result of the acceleration sensor 17b. Note that the gravitational acceleration may be calculated based on the result of statistical processing such as moving average of the detection result of the acceleration sensor 17b.

[0034] After step S10, in step S20, the processing device 12 determines the projection position based on the direction of gravitational acceleration acting on the projector 10. This determination is made by determining whether the projection angle θ, which will be described later and is estimated based on this direction, falls within a range of RA1 to RA4 or a range of RB1 to RB4, which will be described later. Furthermore, if the projection angle θ falls within one of the ranges RB1 to RB4, it is specified which of the ranges RA1 to RA4 the projection angle θ fell within immediately before it fell within this range. Details of step S20 will be described later with reference to FIG. 4.

[0035] After step S20, in step S30, the processing device 12 acquires a point cloud on the projection surface SC based on the detection result of the distance sensor 17a. This point cloud is acquired, for example, as coordinate values ​​indicating a plurality of positions on the projection surface SC.

[0036] After step S30, in step S40, the processing device 12 calculates corrected coordinates. These corrected coordinates are the coordinate values ​​of the four corners of the image G after geometric correction. An example of a method for calculating these coordinate values ​​will be described later with reference to FIGS. 5 and 6.

[0037] After step S40, in step S50, the processing device 12 sets corrected coordinates. The processing device 12 writes the corrected coordinates obtained in step S30 into the storage device 11 as correction value information DC. The image processing circuit 14 performs geometric correction processing with reference to the correction value information DC, thereby executing geometric correction based on the set corrected coordinates. Note that in step S50, a statistical value such as an average value of corrected coordinates at multiple times may be set as the corrected coordinates to be used for geometric correction.

[0038] After step S50, in step S60, the processing device 12 performs focus setting by acquiring the distance between the projector 10 and the projection surface SC based on the detection result of the distance sensor 17a, calculating the position of the lens of the projection optical system 15c based on that distance, and changing the position of the lens based on the calculation result.

[0039] After step S60, in step S70, the processing device 12 determines whether to end the process. This determination is made based on, for example, an operation performed on the projector 10 by the user.

[0040] If the process is not to be completed (step S70: NO), the processing device 12 returns to step S10. As a result, steps S10 to S60 are repeatedly executed in this order. On the other hand, if the process is to be completed (step S70: YES), the processing device 12 ends the process.

[0041] FIG. 4 is an explanatory diagram of switching between geometric corrections in the first embodiment. FIG. 4 shows the relationship between the projection angle θ, which is the angle between the horizontal plane H and the projection direction of the projector 10, and the pattern of geometric correction to be applied. In the following explanation, projection surfaces SC-1 to SC-4 are virtual surfaces defined for the processing performed by the projector 10. In the following, it is assumed that projection surfaces SC-1 to SC-4 are each flat, projection surfaces SC-1 and SC-3 are surfaces parallel to the vertical direction, and projection surfaces SC-2 and SC-4 are surfaces perpendicular to the vertical direction. This simplifies the processing when geometrically correcting image G.

[0042] By changing its posture around the axis AX, the projector 10 can take one of the following states: a state in which it projects image G so that it fits within one of the projection surfaces SC-1 to SC-4; a state in which it projects image G so that it straddles projection surfaces SC-1 and SC-2; a state in which it projects image G so that it straddles projection surfaces SC-2 and SC-3; a state in which it projects image G so that it straddles projection surfaces SC-3 and SC-4; or a state in which it projects image G so that it straddles projection surfaces SC-4 and SC-1.

[0043] Different geometric corrections are applied when projecting image G so that it fits within projection surface SC-1, when projecting image G so that it fits within projection surface SC-2, when projecting image G so that it fits within projection surface SC-3, and when projecting image G so that it fits within projection surface SC-4. Note that "applying geometric correction" includes at least the processing of step S30 in which processing device 12 calculates correction value information DC, and may also include other processing performed by processing device 12 to execute step S30, and processing in which image processing circuit 14 applies geometric correction to video data IMG.

[0044] Here, when the projection target is changed from one projection surface SC among projection surfaces SC-1 to SC-4 to another projection surface SC that intersects with the projection surface SC, it is necessary to switch the geometric correction to be applied. This is because, near the boundary between these projection surfaces SC, one of the upper and lower edges of image G on one projection surface SC is close to the projector 10, while the other of the upper and lower edges on another projection surface SC is close to the projector 10, and therefore the correction method needs to be changed. In this case, if the projection angle θ at which the geometric correction is switched when the projection target is changed from one projection surface SC to the other and the projection angle θ at which the geometric correction is switched when the projection target is changed from the other projection surface SC to one are equal to each other, the geometric correction will be switched frequently. In other words, if the projection angle θ at which the geometric correction is switched is set to one fixed value, and image G is projected at an angle close to that angle, the determination of which projection surface SC the projection target is is changed frequently due to detection errors of sensor 17 or vibrations applied to projector 10. As a result, the geometric correction is switched frequently.

[0045] Therefore, in the projector 10, the projection angle θ at which the geometric correction is switched is changed depending on the direction in which the projection direction changes.

[0046] Specifically, in step S20, the processing device 12 determines to which of the different ranges RA1, RA2, RA3, RA4, RB1, RB2, RB3, and RB4 the projection angle θ belongs. Range RA1 is an example of a "first range." Range RA2 is an example of a "second range" and is a range different from range RA1. Range RB1 is an example of a "third range" and is a range between range RA1 and range RA2.

[0047] Range RA1 is a range that includes an angle of 0° and corresponds to geometric correction A for image G projected onto projection surface SC-1. Range RA2 is a range that includes an angle of 90° and corresponds to geometric correction B for image G projected onto projection surface SC-2. Range RA3 is a range that includes an angle of 180° and corresponds to geometric correction C for image G projected onto projection surface SC-3. Range RA4 is a range that includes an angle of 270° and corresponds to geometric correction D for image G projected onto projection surface SC-4.

[0048] Range RB1 is a range between range RA1 and range RA2 and includes angle α1. Angle α1 is determined according to the projection angle θ when the projection direction intersects with the intersection line between projection surface SC-1 and projection surface SC-2, and is not particularly limited, but is, for example, between 45° and 60°.

[0049] Range RB2 is a range between range RA2 and range RA3 and includes angle α2. Angle α2 is determined according to the projection angle θ when the projection direction intersects with the intersection line between projection surface SC-2 and projection surface SC-3, and is not particularly limited, but is, for example, between 135° and 150°.

[0050] Range RB3 is a range between range RA3 and range RA4, and includes angle α3. Angle α3 is determined according to the projection angle θ when the projection direction intersects with the intersection line between projection surface SC-3 and projection surface SC-4, and is not particularly limited, but is, for example, between 225° and 240°.

[0051] Range RB4 is a range between range RA4 and range RA1 and includes angle α4. Angle α4 is determined according to the projection angle θ when the projection direction intersects with the intersection line between projection surface SC-4 and projection surface SC-1, and is not particularly limited, but is, for example, between 300° and 315°.

[0052] In this embodiment, the magnitudes β1, β2, β3, and β4 of the ranges RB1, RB2, RB3, and RB4 are each greater than 0° and less than 90°, preferably greater than 5° and less than 90°, and more preferably greater than 10° and less than 90°. This makes it possible to preferably reduce frequent unintentional switching of the geometric correction. In this embodiment, the magnitudes β1, β2, β3, and β4 are each less than 90°.

[0053] If the projection angle θ is within the range RA1, in step S40, the processing device 12 applies geometric correction A to correct distortion of the image G projected from the projector 10 onto the projection surface SC-1. Geometric correction A is an example of a "first geometric correction" and includes processing that uses a variable that indicates the angle between the projection surface SC-1 and the projection direction. Therefore, the degree of correction by geometric correction A changes depending on the angle between the projection surface SC-1 and the projection direction. This makes it possible to project onto the projection surface SC-1 an image G that has been subjected to appropriate geometric correction according to the projection angle θ. Geometric correction A includes geometric corrections A-1 and A-2.

[0054] If the projection angle θ is within the range RA2, in step S40, the processing device 12 applies geometric correction B to correct distortion of the image G projected from the projector 10 onto the projection surface SC-2. Geometric correction B is an example of "second geometric correction" and includes processing that uses a variable that indicates the angle between the projection surface SC-2 and the projection direction. Therefore, the degree of correction by geometric correction B changes depending on the angle between the projection surface SC-2 and the projection direction. This makes it possible to project onto the projection surface SC-2 an image G that has been subjected to appropriate geometric correction according to the projection angle θ. Geometric correction B includes geometric corrections B-1 and B-2.

[0055] In the above-mentioned geometric correction A, as will be explained later with reference to FIG. 6, it is necessary to calculate the normal vector of the projection surface SC based on the point cloud acquired in step S30, whereas in geometric correction B, instead of acquiring such a point cloud and calculating the normal vector, the direction of gravitational acceleration is used as the normal vector of the projection surface SC. For this reason, in geometric correction B, measurement by distance sensor 17a is not performed. Also, in geometric correction A, roll correction is performed to correct distortion of image G caused by roll rotation, which is rotation around an axis along the projection direction of projector 10, whereas in geometric correction B, such roll correction is not performed.

[0056] If the projection angle θ is within the range RA3, in step S40, the processing device 12 applies geometric correction C to correct distortion of the image G projected from the projector 10 onto the projection surface SC-3. The geometric correction C includes processing that uses a variable that indicates the angle between the projection surface SC-3 and the projection direction. Therefore, the degree of correction of the geometric correction C changes depending on the angle between the projection surface SC-3 and the projection direction. This makes it possible to project onto the projection surface SC-3 an image G to which appropriate geometric correction has been applied according to the projection angle θ. The geometric correction C includes geometric corrections C-1 and C-2. Note that, like the geometric correction A, the geometric correction C requires calculating the normal vector of the projection surface SC based on the point cloud acquired in step S30, as will be described later with reference to FIG. 6.

[0057] If the projection angle θ is within the range RA4, in step S40, the processing device 12 applies geometric correction D to correct distortion of the image G projected from the projector 10 onto the projection surface SC-4. The geometric correction D includes processing that uses a variable that indicates the angle between the projection surface SC-4 and the projection direction. Therefore, the degree of correction of the geometric correction D changes depending on the angle between the projection surface SC-4 and the projection direction. This makes it possible to project onto the projection surface SC-4 an image G that has been subjected to appropriate geometric correction according to the projection angle θ. The geometric correction D includes geometric corrections D-1 and D-2. Note that, like the geometric correction B, the geometric correction D uses the direction of gravitational acceleration as the normal vector of the projection surface SC.

[0058] If the projection angle θ changes from the range RA1 to an angle within the range RB1, in step S40 the processing device 12 applies geometric correction A-2 of geometric correction A. On the other hand, if the projection angle θ changes from the range RA2 to an angle within the range RB1, in step S40 the processing device 12 applies geometric correction B-1 of geometric correction B.

[0059] If the projection angle θ changes from the range RA2 to an angle within the range RB2, then in step S40 the processing device 12 applies geometric correction B-2 of geometric correction B. On the other hand, if the projection angle θ changes from the range RA3 to an angle within the range RB2, then in step S40 the processing device 12 applies geometric correction C-1 of geometric correction C.

[0060] If the projection angle θ changes from the range RA3 to an angle within the range RB3, then in step S40 the processing device 12 applies the geometric correction C-2 of the geometric correction C. On the other hand, if the projection angle θ changes from the range RA4 to an angle within the range RB3, then in step S40 the processing device 12 applies the geometric correction D-1 of the geometric correction D.

[0061] If the projection angle θ changes from the range RA4 to an angle within the range RB4, then in step S40 the processing device 12 applies the geometric correction D-2 of the geometric correction D. On the other hand, if the projection angle θ changes from the range RA1 to an angle within the range RB4, then in step S40 the processing device 12 applies the geometric correction A-1 of the geometric correction A.

[0062] As described above, the projection angle θ at which the geometric correction is switched varies depending on the direction in which the projection direction changes, which reduces the frequency of unintentional switching of the geometric correction compared to a mode in which the geometric correction is switched at the same projection angle θ regardless of the direction in which the projection direction changes. In other words, even if the projection angle θ changes from an angle within one of the ranges RA1, RA2, RA3, or RA4 to an angle within one of the ranges RB1, RB2, RB3, or RB4, the geometric correction applied before the change in the projection angle θ is applied until the projection angle θ reaches a range RA1, RA2, RA3, or RA4 that is different from the range before the change in the projection angle θ. In this way, the projection angle θ at which the geometric correction is switched has hysteresis, which differs depending on the direction in which the projection angle θ changes.

[0063] Here, when the projection angle θ changes from an angle within range RB1 to an angle within range RA2, in step S40, the processing device 12 applies geometric correction B-1 of geometric correction B. As a result, when the projection angle θ changes from an angle within range RA1 to an angle within range RA2 via range RB1, the projector 10 can project the image G to which geometric correction B has been applied onto the projection surface SC-2.

[0064] On the other hand, if the projection angle θ changes from an angle within range RB1 to an angle within range RA1, in step S40, the processing device 12 applies geometric correction A-2 of geometric correction A. As a result, if the projection angle θ changes from an angle within range RA2 to an angle within range RA1 via range RB1, the projector 10 can project the image G to which geometric correction A has been applied onto the projection surface SC-1.

[0065] Similarly, if the projection angle θ changes from an angle within range RB2 to an angle within range RA3, in step S40, the processing device 12 applies geometric correction C. If the projection angle θ changes from an angle within range RB2 to an angle within range RA2, in step S40, the processing device 12 applies geometric correction B. If the projection angle θ changes from an angle within range RB3 to an angle within range RA4, in step S40, the processing device 12 applies geometric correction D. If the projection angle θ changes from an angle within range RB3 to an angle within range RA3, in step S40, the processing device 12 applies geometric correction C. If the projection angle θ changes from an angle within range RB4 to an angle within range RA1, in step S40, the processing device 12 applies geometric correction A. If the projection angle θ changes from an angle within range RB4 to an angle within range RA4, in step S40, the processing device 12 applies geometric correction D.

[0066] FIG. 5 is an explanatory diagram of correction values. In this embodiment, as shown in FIG. 5, image G is rectangular, and in step S40, coordinate values ​​P1(x,y), P2(x,y), P3(x,y), and P4(x,y) of the four corners of image G are calculated as correction values. These coordinate values ​​are coordinate values ​​of a display coordinate system set in the optical device 15 or a coordinate system associated therewith. Therefore, these coordinate values ​​are associated with pixels of the optical device 15. An example of a method for calculating these correction values ​​will be briefly described below. Note that the method for calculating the correction values ​​is merely an example and is not limited thereto, and various known calculation methods may be used, for example.

[0067] Fig. 6 is a flowchart showing an example of a method for calculating the correction value. In step S40, as shown in Fig. 6, first, in step S41, the processing device 12 acquires a depth map of the projection surface SC based on the point cloud acquired in step S30, finds a plane equation of the projection surface SC from the depth map, and then calculates a normal vector of the projection surface SC as a variable based on the plane equation.

[0068] Then, in step S42, the processing device 12 calculates a rotation matrix that represents the rotation of the projection surface SC as seen from the projector 10 in the projection direction, based on the normal vector of the projection surface SC and the direction of the gravitational acceleration acting on the projector 10.

[0069] After that, in step S43, the processing device 12 calculates the corrected shape as the shape of the image G when facing the projection surface SC.

[0070] Next, in step S44, the processing device 12 uses the rotation matrix calculated in step S42 and the corrected shape calculated in step S43 to calculate the coordinate values ​​P1(x,y), P2(x,y), P3(x,y), and P4(x,y) of the four corners of image G as the coordinates of image G after correction.

[0071] By using the calculation method described above, the detection results of the sensor 17 can be used to automatically perform geometric correction on the image G projected onto the projection surface SC in real time.

[0072] As described above, in the first embodiment, the projection angle θ at which the geometric correction is switched varies depending on the direction in which the projection direction changes, and therefore, compared to a configuration in which the geometric correction is switched at the same projection angle θ regardless of the direction in which the projection direction changes, it is possible to reduce the frequency of unintentional switching of the geometric correction.

[0073] 2. Second embodiment A second embodiment of the present disclosure will be described below. In the following exemplary embodiment, for elements whose actions and functions are similar to those of the first embodiment, the reference numerals used in the description of the first embodiment will be used, and detailed descriptions of each element will be omitted as appropriate.

[0074] 7 is an explanatory diagram of switching of geometric correction in the second embodiment. This embodiment is similar to the first embodiment except that the magnitudes β1, β2, β3, and β4 of the ranges RB1, RB2, RB3, and RB4 are each 90°. Therefore, the magnitudes of the ranges RA1, RA2, RA3, and RA4 are each substantially 0°.

[0075] In this embodiment, when the projection angle θ is 0°, the processing device 12 determines that the projection angle θ is an angle within a range RA1. When the projection angle θ is 90°, the processing device 12 determines that the projection angle θ is an angle within a range RA2. When the projection angle θ is 180°, the processing device 12 determines that the projection angle θ is an angle within a range RA3. When the projection angle θ is 270°, the processing device 12 determines that the projection angle θ is an angle within a range RA4. Therefore, for example, when the projection angle θ is initially set to 0° and the projection direction is changed in a direction in which the projection angle θ increases, geometric correction A is applied when the projection angle θ is less than 90°. When the projection angle θ is 90° or greater, geometric correction B is applied. When geometric correction B is applied, if the projection direction is changed in a direction that decreases the projection angle θ, geometric correction B is applied in a range where the projection angle θ is greater than 0°, and when the projection angle θ becomes 0° or less than 360°, geometric correction A is applied.

[0076] The second embodiment described above also reduces the frequency of unintentional switching of geometric correction. This embodiment also has the advantage that only a small change in the projection angle θ is required to switch between geometric corrections. It also makes it possible to widen the range of projection angles θ to which each geometric correction can be applied. The size of each of the ranges RA1, RA2, RA3, and RA4 may be approximately 1° or more and 5° or less.

[0077] 3. Variations The above-described embodiments can be modified in various ways. Specific modifications that can be applied to the above-described embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples can be combined as appropriate within the scope of not mutually contradictory.

[0078] 3-1. Variation 1 In the above-described embodiment, an example is given in which image G can be projected onto projection surfaces SC-1 to SC-4, but this is not limited to this embodiment, and for example, the projection of image G onto projection surfaces SC-3 and SC-4 may be omitted.

[0079] 3-2. Variation 2 In the above embodiment, projection surface SC-1 is described as the "first projection surface" and projection surface SC-2 as the "second projection surface," but this is not limited to this, and it is possible to regard one projection surface SC of any two adjacent projection surfaces SC of projection surfaces SC-1 to SC-4 as the "first projection surface" and the other projection surface SC as the "second projection surface." In this case, the projection of image G onto projection surfaces SC that do not correspond to the "first projection surface" and "second projection surface" may be omitted.

[0080] 4. Notes A summary of this disclosure is provided below.

[0081] (Supplementary Note 1) A first aspect, which is a preferred example of the correction method of the present disclosure, includes: applying a first geometric correction to correct distortion of an image projected from the projector onto a first projection surface when a projection angle, which is the angle between a horizontal plane and a projection direction of the projector, is an angle within a first range; applying a second geometric correction to correct distortion of an image projected from the projector onto a second projection surface that intersects with the first projection surface when the projection angle is an angle within a second range different from the first range; applying the first geometric correction when the projection angle changes from the first range to an angle within a third range that is a range between the first range and the second range; and applying the second geometric correction when the projection angle changes from the second range to an angle within the third range.

[0082] In the above-described aspects, the projection angle at which the geometric correction is switched varies depending on the direction in which the projection direction changes, and therefore, compared to aspects in which the geometric correction is switched at the same projection angle regardless of the direction in which the projection direction changes, it is possible to reduce the frequency of unintentional switching of the geometric correction.

[0083] (Supplementary Note 2) In the first aspect, which is a preferred example of the first aspect, the second geometric correction is applied when the projection angle changes from an angle within the third range to an angle within the second range. In the above aspect, when the projection angle changes from an angle within the first range to an angle within the second range via the third range, an image to which the second geometric correction has been applied can be projected from the projector onto the second projection surface.

[0084] (Supplementary Note 3) In a third aspect, which is a preferred example of the first or second aspect, the method further includes applying the first geometric correction when the projection angle changes from an angle within the third range to an angle within the first range. In the above aspect, when the projection angle changes from an angle within the second range to an angle within the first range via the third range, an image to which the first geometric correction has been applied can be projected from the projector onto the first projection surface.

[0085] (Supplementary Note 4) In a fourth aspect which is a preferred example of any of the first to third aspects, the first geometric correction includes processing using a variable indicating the angle between the first projection surface and the projection direction, and the second geometric correction includes processing using a variable indicating the angle between the second projection surface and the projection direction. In the above aspect, it is possible to project images to which appropriate geometric corrections have been applied according to the projection angles for each of the first and second projection surfaces.

[0086] (Supplementary Note 5) In a fifth aspect which is a preferred example of any of the first to fourth aspects, the third range is greater than 0° and equal to or less than 90°. In the above aspect, it is possible to preferably reduce frequent unintentional switching of the geometric correction.

[0087] (Supplementary Note 6) In a sixth aspect which is a preferred example of any of the first to fifth aspects, the first projection surface is a surface parallel to the vertical direction, and the second projection surface is a surface perpendicular to the vertical direction. In the above aspects, a wall surface or a screen or the like along the wall surface can be used as the first projection surface, and a ceiling surface or a screen or the like along the wall surface can be used as the second projection surface.

[0088] (Appendix 7) A seventh aspect, which is a preferred example of the projector of the present disclosure, includes an optical device and at least one processor that performs the following operations: applying a first geometric correction to correct distortion of an image projected from the optical device onto a first projection surface when a projection angle, which is the angle between a horizontal plane and a projection direction of the optical device, is an angle within a first range; applying a second geometric correction to correct distortion of an image projected from the optical device onto a second projection surface that intersects with the first projection surface when the projection angle is an angle within a second range different from the first range; applying the first geometric correction when the projection angle changes from the first range to an angle within a third range that is a range between the first range and the second range; and applying the second geometric correction when the projection angle changes from the second range to an angle within the third range.

[0089] In the above-described aspects, the projection angle at which the geometric correction is switched varies depending on the direction in which the projection direction changes, and therefore, compared to aspects in which the geometric correction is switched at the same projection angle regardless of the direction in which the projection direction changes, it is possible to reduce unintentional and frequent switching of the geometric correction.

[0090] (Appendix 8) An eighth aspect, which is a preferred example of the program of the present disclosure, causes at least one processor to perform the following: apply a first geometric correction to correct distortion of an image projected from the projector onto a first projection surface when a projection angle, which is the angle between a horizontal plane and the projection direction of the projector, is an angle within a first range; apply a second geometric correction to correct distortion of an image projected from the projector onto a second projection surface that intersects with the first projection surface when the projection angle is an angle within a second range different from the first range; apply the first geometric correction when the projection angle changes from the first range to an angle within a third range that is a range between the first range and the second range; and apply the second geometric correction when the projection angle changes from the second range to an angle within the third range.

[0091] In the above-described aspects, the projection angle at which the geometric correction is switched varies depending on the direction in which the projection direction changes, and therefore, compared to aspects in which the geometric correction is switched at the same projection angle regardless of the direction in which the projection direction changes, it is possible to reduce unintentional and frequent switching of the geometric correction. [Explanation of symbols]

[0092] 10...projector, 11...storage device, 12...processor, 13...communication device, 14...image processing circuit, 15...optical device, 15a...light source, 15b...light modulator, 15c...projection optical system, 16...operation device, 17...sensor, 17a...distance sensor, 17b...acceleration sensor, 100...system, A...geometric correction (first geometric correction), A-1...geometric correction, A-2...geometric correction, AX...axis, B...geometric correction (second geometric correction), B-1...geometric correction, B-2...geometric correction, C...geometric correction, C-1...geometric correction, C-2...geometric correction, D...geometric correction, D-1...geometric correction, D-2...geometric correction, DC...correction value information, G...image, H...horizontal plane, IMG...video data, P1...coordinate value, PA...variable information information, PR1...program, RA1...range (first range), RA2...range (second range), RA3...range, RA4...range, RB1...range (third range), RB2...range, RB3...range, RB4...range, S10...step, S20...step, S30...step, S40...step, S41...step, S42...step, S43...step, S44...step, S50...step, S60...step, S70...step, SC...projection surface, SC-1...projection surface (first projection surface), SC-2...projection surface (second projection surface), SC-3...projection surface, SC-4...projection surface, α1...angle, α2...angle, α3...angle, α4...angle, β1...magnitude, β2...magnitude, β3...magnitude, β4...magnitude, θ...projection angle.

Claims

1. applying a first geometric correction to correct distortion of an image projected onto a first projection surface from a projector when a projection angle, which is an angle between a horizontal plane and a projection direction of the projector, is within a first range; applying a second geometric correction to correct distortion of an image projected from the projector onto a second projection surface intersecting the first projection surface when the projection angle is within a second range different from the first range; and applying the first geometric correction when the projection angle changes from the first range to an angle within a third range that is a range between the first range and the second range; applying the second geometric correction when the projection angle changes from the second range to an angle within the third range; A correction method comprising:

2. applying the second geometric correction when the projection angle changes from an angle within the third range to an angle within the second range. The correction method according to claim 1 .

3. applying the first geometric correction when the projection angle changes from an angle within the third range to an angle within the first range. The correction method according to claim 1 .

4. the first geometric correction includes processing using a variable indicating an angle between the first projection surface and the projection direction, the second geometric correction includes processing using a variable indicating an angle between the second projection surface and the projection direction. The correction method according to any one of claims 1 to 3.

5. The third range is greater than 0° and less than or equal to 90°. The correction method according to any one of claims 1 to 3.

6. the first projection surface is a surface parallel to the vertical direction, the second projection surface is a surface perpendicular to the vertical direction; The correction method according to any one of claims 1 to 3.

7. an optical device; applying a first geometric correction to correct distortion of an image projected onto a first projection surface from the optical device when a projection angle, which is an angle between a horizontal plane and a projection direction of the optical device, is within a first range; applying a second geometric correction to correct distortion of an image projected from the optical device onto a second projection surface intersecting the first projection surface when the projection angle is within a second range different from the first range; and applying the first geometric correction when the projection angle changes from the first range to an angle within a third range that is a range between the first range and the second range; applying the second geometric correction when the projection angle changes from the second range to an angle within the third range; at least one processor executing Including, projector.

8. At least one processor applying a first geometric correction to correct distortion of an image projected onto a first projection surface from a projector when a projection angle, which is an angle between a horizontal plane and a projection direction of the projector, is within a first range; applying a second geometric correction to correct distortion of an image projected from the projector onto a second projection surface intersecting the first projection surface when the projection angle is within a second range different from the first range; and applying the first geometric correction when the projection angle changes from the first range to an angle within a third range that is a range between the first range and the second range; applying the second geometric correction when the projection angle changes from the second range to an angle within the third range; Execute program.

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