Method of correcting a projection area of a projector and projection system

Abstract

A method for correcting a projection area of a projector and a projection system are provided. The method includes projecting a correction pattern to form a projection area, wherein the correction pattern includes a first original mark group and a second original mark group; obtaining a captured image including the projection area; determining whether the captured image includes a closed area formed by complete lines; performing a first correction operation when the captured image does not include the closed area; performing a second correction operation when the projection area in the captured image includes a complete closed area; correcting the projection area according to the first mark group or the second mark group in the captured image when the first correction operation is performed; and correcting the projection area according to the second mark group in the captured image when the second correction operation is performed. The projection system provided by the present application can determine a proper correction method to correct the projection area generated by an ultra-short focus lens, regardless of whether the projection system can detect a closed area with a complete frame.

Description

Technical Field

[0001] This invention relates to a projection method and projection system, and more particularly to a method and projection system for correcting the projection area of ​​a projector. Background Technology

[0002] Projector image keystone correction functions can be broadly categorized into three types: using accelerometers to correct the vertical direction of the projected image, using a camera to correct the projected image within the projection screen frame or an area with a frame, and using a time-of-flight (ToF) sensor to correct the projected image in both vertical and horizontal directions based on the relative angle of the projection plane. Each of these methods has its limitations. First, the accelerometer-based correction method can only correct the projected image in the vertical direction, and it will fail to correct correctly when the projection plane is not at a 90-degree angle to the projection screen or wall. Second, when the camera cannot detect the frame (e.g., the projection screen frame) or the distance between the projector and the projection plane is insufficient, the projected image will not contain the complete frame, thus preventing correction. Third, the ToF sensor-based correction method is not suitable for projections with frames, as the ToF sensor cannot determine the existence of the frame and its actual coordinates. Therefore, none of these three correction methods can meet the needs of all projector application scenarios.

[0003] For camera-based calibration methods, when the projection system's lens throw ratio is similar to that of an ultra-short-throw lens, the projector must project at an angle of elevation or downward due to the short distance between the lens and the projection plane. When the projector's elevation angle is too large, it becomes difficult for the camera to capture the entire projection plane. Therefore, a fisheye or wide-angle lens may be necessary. However, most calibration algorithms are based on calculations using Cartesian coordinates. Since images captured by fisheye or wide-angle lenses may be distorted and warped, they are not suitable for most calibration algorithms.

[0004] The "Background Art" paragraph is only used to help understand the content of this invention. Therefore, the content disclosed in the "Background Art" paragraph may include some known technologies that are not known to those skilled in the art. The content disclosed in the "Background Art" paragraph does not mean that the content or the problems to be solved by one or more embodiments of this invention were known or understood by those skilled in the art prior to this application. Summary of the Invention

[0005] This invention provides a method and system for correcting the projection area of ​​a projector, which can be used to correct the projection area of ​​a projector with an ultra-short throw lens.

[0006] A method for correcting the projection area of ​​a projector according to the present invention includes: projecting a correction pattern to form a projection area by the projector, wherein the correction pattern includes a first original symbol group and a second original symbol group, wherein the second original symbol group surrounds the first original symbol group and the first original symbol group surrounds the center point of the correction pattern; acquiring a captured image including the projection area by an image capturing device, wherein the captured image includes a first symbol group corresponding to the first original symbol group and a second symbol group corresponding to the second original symbol group; performing a first image recognition on the captured image by a processor to determine whether the captured image contains a closed region formed by complete lines, wherein when the processor determines that the captured image does not contain a closed region, a first correction operation is performed, and when the processor determines that the projection area in the captured image contains a complete closed region, a second correction operation is performed; when performing the first correction operation, the projection area is corrected according to the first symbol group or the second symbol group in the captured image; and when performing the second correction operation, the projection area is corrected according to the second symbol group in the captured image.

[0007] A projection system of the present invention includes a projector, an image capturing device, and a processor. The processor is coupled to the image capturing device and the projector, wherein the processor is configured to perform: projecting a correction pattern by the projector to form a projection area, wherein the correction pattern includes a first group of original symbols and a second group of original symbols, wherein the second group of original symbols surrounds the first group of original symbols and the first group of original symbols surrounds the center point of the correction pattern; acquiring a captured image including the projection area by the image capturing device, wherein the captured image includes a first group of symbols corresponding to the first group of original symbols and a second group of symbols corresponding to the second group of original symbols; performing a first image recognition on the captured image to determine whether the captured image contains a closed region formed by complete lines; when the captured image does not contain a closed region, performing a first correction operation; when the projection area in the captured image contains a complete closed region, performing a second correction operation; and when performing the first correction operation, correcting the projection area according to the first group of symbols or the second group of symbols in the captured image; and when performing the second correction operation, correcting the projection area according to the second group of symbols in the captured image.

[0008] Based on the above, the projection system of the present invention can project a correction pattern comprising a first primary symbol group and a second primary symbol group surrounding the first primary symbol group, and correct the projection area of ​​the projector using the captured image corresponding to the correction pattern. Regardless of whether the application scenario of the projector includes a projection screen or wall with a complete frame, the projection system can use an appropriate primary symbol group to correct the projection area of ​​a projector with an ultra-short-throw lens.

[0009] To make the above features and advantages of the present invention more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings. Attached Figure Description

[0010] Figure 1 A schematic diagram of a projection system is shown according to an embodiment of the present invention.

[0011] Figure 2 A flowchart illustrating a method for correcting the projection area of ​​a projector is shown according to an embodiment of the present invention.

[0012] Figure 3 A schematic diagram of a correction pattern is shown according to an embodiment of the present invention.

[0013] Figure 4 A schematic diagram illustrating the projection area and the captured image is shown according to an embodiment of the present invention.

[0014] Figure 5 A schematic diagram illustrating the offset between the original markings in the correction pattern and the markings in the captured image is shown according to an embodiment of the present invention.

[0015] Figure 6 A schematic diagram illustrating the determination of the offset direction of the projection area based on multiple marks in a second mark group is provided according to an embodiment of the present invention.

[0016] Figure 7 A schematic diagram of a projected region including a closed region is shown according to an embodiment of the present invention.

[0017] Figure 8 A schematic diagram of the corrected projection area is shown according to an embodiment of the present invention.

[0018] Figure 9 A flowchart illustrating a method for correcting the projection area of ​​a projector is shown according to another embodiment of the present invention. Detailed Implementation

[0019] To make the content of this invention more readily apparent, the following specific embodiments are provided as examples on which this invention can indeed be practiced. Furthermore, wherever possible, elements / components / steps referred to by the same reference numerals in the drawings and embodiments represent the same or similar parts.

[0020] Figure 1 A schematic diagram of a projection system 100 is illustrated according to an embodiment of the present invention, wherein the projection system 100 is, for example, an ultra-short throw projection system. The projection system 100 may include a processor 110, a projector 120, and an image capturing device 130. The processor 110 may be coupled to the projector 120 and the image capturing device 130 to control the projector 120 and the image capturing device 130.

[0021] The processor 110 is, for example, a central processing unit (CPU), or other programmable general-purpose or special-purpose microcontroller (MCU), microprocessor, digital signal processor (DSP), programmable controller, application-specific integrated circuit (ASIC), graphics processing unit (GPU), image signal processor (ISP), image processing unit (IPU), arithmetic logic unit (ALU), complex programmable logic device (CPLD), field programmable gate array (FPGA), or other similar elements or combinations thereof.

[0022] Projector 120 may include, but is not limited to, multiple components controlled by processor 110, such as an illumination module with a light-emitting device, a light valve, a prism, a lens, or a projection lens. Processor 110 can control projector 120 to project an image onto a projection surface (e.g., a projection screen or a wall) to form a projection area.

[0023] The image capturing device 130 is, for example, a camera or other device used to capture images. The image capturing device 130 can capture an image including the projection area facing the projection surface. The captured image acquired by the image capturing device 130 can be used to correct the projection area of ​​the projector 120, thereby solving the problem of image distortion caused by the projector 120 using a fisheye lens or wide-angle lens.

[0024] Figure 2 A flowchart illustrating a method for correcting the projection area of ​​a projector according to an embodiment of the present invention is shown, wherein the method may be performed by, for example... Figure 1 The projection system 100 shown is implemented. In step S201, a correction pattern is projected by the projector 120 to form a projection area, and a captured image containing the projection area can be obtained by the image capturing device 130. For example, the projector 120 can be controlled by the processor 110 to project the correction pattern to form the projection area.

[0025] refer to Figure 3 and Figure 4 , Figure 3 A schematic diagram of the correction pattern 300 is shown according to an embodiment of the present invention. Figure 4 A schematic diagram of a projection area 400 and an image capture 500 is shown according to an embodiment of the present invention. The correction pattern 300 may be pre-stored in the storage medium of the processor 110. Before the projector 120 is manufactured, the processor 110 may use the projector 120 to project the original image corresponding to the correction pattern 300 onto a projection surface, and use the image capturing device 130 to capture the original image projected onto the projection surface and store it as the correction pattern 300. The original image may be quadrilateral or rectangular. Since the lens of the projector 120 may be a fisheye lens or a wide-angle lens, the correction pattern 300 may become a distorted quadrilateral or rectangle compared to the original image.

[0026] The processor 110 can project a pre-stored correction pattern 300 through the projector 120 to form a projection area 400, and can acquire a captured image 500 containing the projection area 400 through the image capturing device 130. The projection area 400 is, for example, a deformed quadrilateral or rectangle. The projection area 400 may contain four vertices, namely vertex C1, vertex C2, vertex C3, and vertex C4, such as... Figure 4 As shown.

[0027] The correction pattern 300 may include a first primitive symbol group, which may contain four primitive symbols: primitive symbol b1, primitive symbol b2, primitive symbol b3, and primitive symbol b4. The four primitive symbols in the first primitive symbol group may correspond to the four vertices C1 to C4 of the projection region 400, respectively. Specifically, primitive symbol b1 may correspond to vertex C1, primitive symbol b2 may correspond to vertex C2, primitive symbol b3 may correspond to vertex C3, and primitive symbol b4 may correspond to vertex C4. Principal symbol b1 (or vertex C1) may be the opposite vertex of primitive symbol b3 (or vertex C3), and primitive symbol b2 (or vertex C2) may be the opposite vertex of primitive symbol b4 (or vertex C4).

[0028] The correction pattern 300 may further include a second group of primitive symbols, which may contain eight primitive symbols: primitive symbol a1, primitive symbol a2, primitive symbol a3, primitive symbol a4, primitive symbol a5, primitive symbol a6, primitive symbol a7, and primitive symbol a8. Four of the primitive symbols in the second group of primitive symbols may correspond to the four vertices C1 to C4 of the projection region 400, respectively. Specifically, primitive symbol a1 may correspond to vertex C1, primitive symbol a3 to vertex C2, primitive symbol a5 to vertex C3, and primitive symbol a7 to vertex C4. Primitive symbol a1 may be the opposite vertex of primitive symbol a5, and primitive symbol a3 may be the opposite vertex of primitive symbol a7. The remaining four primitive symbols in the second group of primitive symbols may correspond to the line connecting two vertices of the projection region 400 or a common edge. Specifically, primitive symbol a2 may correspond to the line connecting vertex C1 and vertex C2. That is, the original symbol a2 can be connected to the corresponding line. Furthermore, it lies between the original symbols a1 and a3, and the original symbol a4 can correspond to the line connecting vertex C2 and vertex C3. That is, the original symbol a4 can be connected to the corresponding line. Furthermore, it lies between the original symbols a3 and a5, and the original symbol a6 corresponds to the line connecting vertex C3 and vertex C4. That is, the original symbol a6 can be connected to the line. It is located between the original symbols a5 and a7, and the original symbol a8 corresponds to the line connecting vertex C4 and vertex C1. That is, the original symbol a8 can be connected to a line. It is located between the original symbol a1 and the original symbol a7.

[0029] The first group of original symbols may surround the center point O1 of the correction pattern 300, and the second group of original symbols may surround the first group of original symbols. In one embodiment, if one original symbol in the first group of original symbols and another original symbol in the second group of original symbols correspond to the same vertex of the projection region 400, then the distance between the original symbol in the first group of original symbols and the center point O1 of the correction pattern 300 may be less than or equal to the distance between the original symbol in the second group of original symbols and the center point O1 of the correction pattern 300. Taking vertex C1 of the projection region 400 as an example, the distance between the original symbol b1 in the first group of original symbols and the center point O1... The distance between the primitive symbol a1 and the center point O1 in the second primitive symbol group is smaller than the distance between the primitive symbol a1 and the center point O1. Similarly, the distance between primitive symbol b2 in the first primitive symbol group and the center point O1 It can be less than the distance between the primitive symbol a3 and the center point O1 in the second primitive symbol group. The distance between primitive symbol b3 in the first primitive symbol group and the center point O1 It can be less than the distance between the primitive symbol a5 in the second primitive symbol group and the center point O1. And the distance between primitive symbol b4 in the first primitive symbol group and the center point O1 It can be less than the distance between the primitive symbol a7 in the second primitive symbol group and the center point O1.

[0030] In one embodiment, if one original symbol in the first original symbol group and another original symbol in the second original symbol group correspond to the same vertex of the projection region 400, then the distance between the original symbol in the first original symbol group and the center point O1 of the correction pattern 300 in the first direction can be less than or equal to the distance between the original symbol in the second original symbol group and the center point O1 of the correction pattern 300 in the first direction, and the distance between the original symbol in the first original symbol group and the center point O1 of the correction pattern 300 in the second direction can be less than or equal to the distance between the original symbol in the second original symbol group and the center point O1 of the correction pattern 300 in the second direction, wherein the first direction and the second direction can be perpendicular to each other. For example, the first direction can be the X direction of a rectangular coordinate system, and the second direction can be the Y direction of a rectangular coordinate system. Taking vertex C1 of the projection region 400 as an example, the distance between the original symbol b1 in the first original symbol group and the center point O1... The length of the orthographic projection on the X-axis can be less than the distance between the original symbol a1 and the center point O1 in the second original symbol group. The length of the orthographic projection on the X-axis, and the distance The orthographic projection length on the Y-axis can be less than the distance. The length of the orthogonal projection on the Y-axis.

[0031] The captured image 500 may include a first symbol group corresponding to a first original symbol group, wherein the first symbol group may include four symbols: symbol B1 corresponding to original symbol b1 (or vertex C1), symbol B2 corresponding to original symbol b2 (or vertex C2), symbol B3 corresponding to original symbol b3 (or vertex C3), and symbol B4 corresponding to original symbol b4 (or vertex C4). Depending on the application scenario of the projector 120, there may be an offset between the first symbol group and the first original symbol group. For example... Figure 5 As shown, the marks B1, B2, B3 and B4 in the captured image 500 cannot completely overlap with the original marks b1, b2, b3 and b4 in the correction pattern 300 pre-stored in the projector 120.

[0032] Back Figure 3 and Figure 4The captured image 500 may also include a second symbol group corresponding to the second original symbol group, wherein the second symbol group may include eight symbols, namely symbol A1 corresponding to the original symbol a1 (or vertex C1), symbol A2 corresponding to the original symbol a2 (or connection) and symbol A1 corresponding to the original symbol a2 (or connection) and symbol A1 corresponding to the original symbol a1 (or vertex C1). The notation A2 corresponds to the original notation a3 (or vertex C2), and the notation A3 corresponds to the original notation a4 (or the connection). The notation A4 corresponds to the original notation a5 (or vertex C3), and the notation A5 corresponds to the original notation a6 (or the connection). The notation A6, the notation corresponding to the original notation a7 (or vertex C4), and the notation corresponding to the original notation a8 (or connection) The notation A8. Depending on the application scenario of the projector 120, there may be an offset between the second notation group and the second original notation group. For example... Figure 5 As shown, the symbols A1, A2, A3, A4, A5, A6, A7 and A8 in the captured image 500 cannot completely overlap with the original symbols a1, a2, a3, a4, a5, a6, a7 and a8 in the correction pattern 300 pre-stored in the projector 120.

[0033] Back Figure 2 In step S202, the processor 110 may perform image recognition on the captured image 500 to determine whether the captured image 500 contains a closed region formed by complete lines (e.g., such as...). Figure 7 The captured image 500 is a framed closed area 600. If the processor 110 determines that the captured image 500 contains a closed area formed by complete lines, it proceeds to step S206. If the processor 110 determines that the captured image 500 does not contain a closed area formed by complete lines, it proceeds to step S203. Steps S202 and S206 can be used to confirm whether the captured image 500 contains a projection screen with a complete frame.

[0034] In step S203, the processor 110 may perform image recognition on the captured image 500 to determine whether at least one of the multiple marks in the second mark group is not included in the captured image 500. If at least one of the multiple marks in the second mark group is not included in the captured image 500, then proceed to step S207. If each of the multiple marks in the second mark group is included in the captured image 500, then proceed to step S204.

[0035] In one embodiment, the multiple marks in the second mark group in the captured image 500 may include three marks corresponding to three vertices of the projection region 400, such as vertices C1, C2, and C3, and the three marks are, for example, marks A1, A3, and A5. If at least one of marks A1, A3, and A5 is not included in the captured image 500, the processor 110 can determine that at least one of the multiple marks in the second mark group is not included in the captured image 500, and proceeds to step S207. If each of marks A1, A3, and A5 is included in the captured image 500, the processor 110 can determine that all the multiple marks in the second mark group are included in the captured image 500, and proceeds to step S204.

[0036] In step S204, the processor 110 can determine whether the absolute difference between the included angle of the triangle corresponding to the first original symbol group and the included angle of the triangle corresponding to the first symbol group is greater than a threshold. If the absolute difference is greater than the threshold, proceed to step S207. If the absolute difference is less than or equal to the threshold, proceed to step S205.

[0037] Specifically, processor 110 can obtain a triangle formed by three original symbols from the first group of original symbols in the correction pattern 300, wherein the three original symbols may correspond to the three vertices of the projection region 400, respectively. The three original symbols mentioned above are, for example, original symbols b1, b2, and b3 corresponding to vertices C1, C2, and C3, respectively, and the triangle is, for example, triangle 310 (shown in...). Figure 3 Furthermore, the processor 110 can obtain a triangle formed by three marks from the first mark group in the captured image 500, wherein the three marks may correspond to the three vertices of the projection region 400, respectively. The three marks mentioned above are, for example, marks B1, B2, and B3 corresponding to the original marks b1, b2, and b3, respectively, and the triangle is, for example, triangle 410 corresponding to triangle 310 (illustrated in...). Figure 4 ).

[0038] Next, the processor 110 can obtain the absolute difference between an included angle of triangle 310 of the correction pattern 300 and a corresponding included angle of triangle 410 of the captured image 500, and determine whether the absolute difference is greater than a threshold. For example, the processor 110 can calculate the absolute difference between the included angle ∠b2b1b3 of triangle 310 corresponding to vertex C1 and the included angle ∠B2B1B3 of triangle 410 corresponding to vertex C1, and determine whether the absolute difference is greater than a threshold to decide whether to execute step S205 or step S207.

[0039] In step S205, the processor 110 may perform a first correction operation to correct the projection area 400 based on a plurality of marks in a second mark group and a plurality of original marks in a second original mark group in the captured image 500. The first correction operation is applicable to correcting the projection area 400 that is not projected within a framed enclosed area 600, i.e., applicable to the correction of the projection area in a frameless projection system. The plurality of marks includes, for example, marks A1, A3, and A5, and the plurality of original marks includes, for example, marks a1, a3, and a5.

[0040] Specifically, the processor 110 can first determine the offset direction of the projection region 400. The processor 110 can obtain two original symbols corresponding to two adjacent vertices of the projection region 400 from the second original symbol group of the self-correction pattern 300, and further obtain another original symbol from the second original symbol group corresponding to the line connecting the two adjacent vertices. On the other hand, the processor 110 can obtain three symbols corresponding to the three original symbols from the second symbol group of the captured image 500. These three original symbols include, for example, original symbols a1 and a3 corresponding to vertices C1 and C2 respectively, and a symbol corresponding to the line connecting the two vertices. The original notation a2. The three notations mentioned above include, for example, notations A1, A2, and A3, which correspond to the original notations A1, A2, and A3, respectively.

[0041] It is worth noting that, compared to the center point O1 of the correction pattern 300, the original symbols a1, a2, and a3 are all offset towards the negative X direction. Similarly, compared to the center point O2 of the projection area 400, symbols A1, A2, and A3 are all offset towards the negative X direction. The processor 110 can determine whether the projection area 400 is offset towards the negative X direction based on the original symbols a1, a2, a3, A1, A2, and A3. Figure 6 According to an embodiment of the present invention, a schematic diagram is drawn to determine the offset direction of the projection area based on multiple marks in a second mark group. If the included angle ∠a2a1a3 is less than the included angle ∠A2A1A3, then the processor 110 can determine that the projection area 400 is offset towards the negative X direction, wherein the included angle ∠a2a1a3 is less than the included angle ∠A2A1A3. Connect and The included angle between the lines, ∠A2A1A3 is Connect and The included angle between the connecting lines. Accordingly, the processor 110 can determine the amount of angular variation between the triangles corresponding to the original symbols a1 and a3 (e.g., triangle 320 formed by original symbols a1, a3, and a5, or triangle formed by original symbols a1, a3, and a7) and the triangle corresponding to symbols A1 and A3 (e.g., triangle 420 formed by symbols A1, A3, and A5, or triangle formed by symbols A1, A3, and A7), wherein the three included angles of the two triangles correspond to the three vertices of the projection region 400, respectively. The processor 110 can correct the projection region 400 by reducing the amount of angular variation.

[0042] Suppose that processor 110 decides to use triangle 320, formed by original symbols a1, a3, and a5, and triangle 420, formed by symbols A1, A3, and A5, to correct the projection region 400. Processor 110 can calculate the difference between any two corresponding angles of triangles 320 and 420 to obtain the angular change. For example, processor 110 can calculate the difference between angles ∠a3a1a5 and ∠A3A1A5, and the difference between angles ∠a1a3a5 and ∠A1A3A5. Processor 110 can adjust the projection region 400 accordingly by setting these two differences to zero, thereby completing the correction of the projection region 400.

[0043] Similarly, processor 110 can determine whether the projection area 400 is offset in the positive Y direction based on the original symbols a1, a8, and a7 and symbols A1, A8, and A7. If the projection area 400 is offset in the positive Y direction, processor 110 can decide to perform vertical correction on the projection area 400 using triangles corresponding to the original symbols a1 and a7 and triangles corresponding to symbols A1 and A7. Processor 110 can determine whether the projection area 400 is offset in the positive X direction based on the original symbols a7, a6, and a5 and symbols A7, A6, and A5. If the projection area 400 is offset in the positive X direction, processor 110 can decide to perform horizontal correction on the projection area 400 using triangles corresponding to the original symbols a7 and a5 and triangles corresponding to symbols A7 and A5. Processor 110 can determine whether the projection area 400 is offset in the negative Y direction based on the original symbols a3, a4, and a5 and symbols A3, A4, and A5. If the projection area 400 is offset in the negative Y direction, the processor 110 may decide to use the triangles corresponding to the original symbols a3 and a5 and the triangles corresponding to symbols A3 and A5 to perform vertical correction on the projection area 400.

[0044] If the processor 110 determines that the captured image 500 contains a closed region formed by complete lines, then proceed to step 206. In step S206, the processor 110 may perform image recognition on the captured image 500 to determine whether the projection region 400 in the captured image 500 contains a complete closed region (e.g., such as...). Figure 7 (The closed region 600 shown). If the projected region 400 contains the complete closed region, proceed to step S208. If the projected region 400 does not contain the complete closed region, proceed to step S207.

[0045] In step S207, the processor 110 may perform a first correction operation to correct the projection area 400 based on a plurality of marks in a first mark group and a plurality of original marks in a first original mark group in the captured image 500. The first correction operation may be applicable to correcting projection areas 400 that are not projected within a framed enclosed area (e.g., within a projection screen). The plurality of marks may include, for example, marks B1, B2, and B3, and the plurality of original marks may include, for example, original marks b1, original marks b2, and original marks b3.

[0046] Specifically, the processor 110 can first determine the offset direction of the projection area 400. The method for determining the offset direction of the projection area 400 is the same as that described in step S205, and therefore will not be repeated here. It is worth noting that, compared to the center point O1 of the correction pattern 300, both the original markers b1 and b2 are offset towards the negative X direction. Compared to the center point O2 of the projection area 400, both markers B1 and B2 are offset towards the negative X direction. Accordingly, if the processor 110 determines that the projection region 400 is offset towards the negative X direction, the processor 110 may decide to correct the projection region 400 by using the angular change between the triangles corresponding to the original symbols b1 and b2 (e.g., triangle 310 formed by the original symbols b1, b2, and b3, or triangle formed by the original symbols b1, b2, and b4) and the triangles corresponding to symbols B1 and B2 (e.g., triangle 410 formed by the symbols B1, B2, and B3, or triangle formed by the symbols B1, B2, and B4), wherein the three included angles of the two triangles correspond to the three vertices of the projection region 400, respectively. The processor 110 can correct the projection region 400 by reducing the angular change.

[0047] Suppose processor 110 decides to use triangle 310, composed of original symbols b1, b2, and b3, and triangle 410, composed of symbols B1, B2, and B3, to correct the projection region 400. Processor 110 can calculate the difference between any two corresponding angles of triangles 310 and 410 to obtain the angular change. For example, processor 110 can calculate the difference between angles ∠b2b1b3 and ∠B2B1B3, and the difference between angles ∠b1b2b3 and ∠B1B2B3. Processor 110 can adjust the projection region 400 accordingly by setting these two differences to zero, thereby completing the correction of the projection region 400.

[0048] Similarly, if the projection area 400 is offset in the positive Y direction, the processor 110 may decide to perform vertical correction on the projection area 400 using triangles corresponding to the original notations b1 and b4 and triangles corresponding to notations B1 and B4. If the projection area 400 is offset in the positive X direction, the processor 110 may decide to perform horizontal correction on the projection area 400 using triangles corresponding to the original notations b4 and b3 and triangles corresponding to notations B4 and B3. If the projection area 400 is offset in the negative Y direction, the processor 110 may decide to perform vertical correction on the projection area 400 using triangles corresponding to the original notations b2 and b3 and triangles corresponding to notations B2 and B3.

[0049] If the projection area 400 contains a complete closed region, then proceed to step S208. In step S208, the processor 110 may perform a second correction operation to correct the projection area 400 according to a plurality of marks in a second mark group, wherein the second correction operation may be applicable to adjust the projection area 400 to within the closed range 600. The plurality of marks, for example, includes marks A1, A3, A5, and A7 corresponding to vertices C1, C2, C3, and C4 of the projection area 400, respectively.

[0050] Specifically, the processor 110 can perform image recognition on the captured image 500 to detect multiple corners of the closed region 600, wherein the multiple corners may include corners D1, D2, D3, and D4, and the corners D1, D2, D3, and D4 of the closed region 600 correspond to vertices C1, C2, C3, and C4 of the projected region 400, respectively. Figure 7 As shown. Figure 7 A schematic diagram of a projection area 400 including a closed area 600 is shown according to an embodiment of the present invention.

[0051] The enclosed region 600 in the captured image 500 may be included within the projection region 400. In one embodiment, if a corner point of the enclosed region 600 and a mark in the second mark group correspond to the same vertex of the projection region 400, then the distance between the corner point corresponding to a vertex and the center point O2 of the projection region 400 may be less than the distance between the mark corresponding to the same vertex and the center point O2. For example, the distance between corner point D1 and center point O2... It can be less than the distance between symbol A1 and center point O2. Distance between corner point D2 and center point O2 It can be less than the distance between symbol A3 and center point O2. Distance between corner point D3 and center point O2 It can be less than the distance between symbol A5 and center point O2. And the distance between corner point D4 and center point O2 It can be less than the distance between symbol A7 and center point O2.

[0052] In one embodiment, if the corner point of the closed region 600 and the mark in the second mark group correspond to the same vertex of the projection region 400, then the distance between the corner point of the corresponding vertex and the center point O2 in the first direction can be less than the distance between the mark of the corresponding vertex and the center point O2 in the first direction, and the distance between the corner point of the corresponding vertex and the center point O2 in the second direction can be less than the distance between the mark of the corresponding vertex and the center point O2 in the second direction, wherein the first direction and the second direction can be perpendicular to each other. For example, the first direction can be the X direction of the rectangular coordinate system, and the second direction can be the Y direction of the rectangular coordinate system. Taking vertex C1 of the projection region 400 as an example, the distance between corner point D1 and center point O2... The length of the orthographic projection on the X-axis can be less than the distance between the symbol A1 and the center point O2. The length of the orthographic projection on the X-axis, and the distance The orthographic projection length on the Y-axis can be less than the distance. The length of the orthogonal projection on the Y-axis.

[0053] After detecting the corner points of the closed region 600, the processor 110 can correct the projected region based on the corner points and the marks in the second mark group corresponding to the corner points. Taking the corner point D1 corresponding to vertex C1 and mark A1 as an example, the processor 110 can obtain the straight line formed by mark A1 and mark A3. It can also obtain the straight line formed by corner points D1 and D2. Processor 110 can further obtain straight lines With a straight line The included angle θ AOn the other hand, the processor 110 can obtain the straight line formed by the symbols A1 and A7. It can also obtain the straight line formed by corner point D1 and corner point D4. Processor 110 can further obtain straight lines With a straight line The included angle θ B The processor 110 has an adjustable included angle θ. A and the included angle θ B , so that the included angle θ A and the included angle θ B Approaching zero to correct the projection area of ​​400.

[0054] At the included angle θ A and the included angle θ B When adjusted to zero, the position of marker A1 can overlap with the position of corner point D1 of the closed region 600. Based on the relative position of marker A1 of the second marker group with respect to the vertex C1 of its corresponding projection region 400, the processor 110 can further update the position of marker A1, making the distance between marker A1 and center point O2 in the first direction less than the distance between corner point D1 and center point O2 in the first direction, and making the distance between marker A1 and center point O2 in the second direction less than the distance between corner point D1 and center point O2 in the second direction, wherein the first and second directions can be perpendicular to each other. For example, the first direction can be the X direction of a Cartesian coordinate system, and the second direction can be the Y direction of a Cartesian coordinate system.

[0055] Using a similar method, processor 110 can update the positions of markers A1, A3, A5 and A7 in projection area 400 to generate a corrected projection area 450. Figure 8 A schematic diagram of a corrected projection area is shown according to an embodiment of the present invention, wherein the projection area 450 is the corrected projection area, that is, the projection area 400 before correction is adjusted to the corrected projection area 450. The corrected projection area 450 may be completely contained within the closed area 600, or the vertices C1' to C4' of the corrected projection area 450 may overlap with the corner points D1 to D4 of the closed area 600.

[0056] Based on the above, if the projection area 400 in the captured image 500 contains a closed area 600 formed by complete lines (e.g., a projection screen with a frame), the processor 110 can perform a second correction operation to adjust the image projected by the projector 120 to remain completely within the closed area 600. Conversely, if the processor 110 does not detect any closed area 600 in the captured image 500 or the projection area 400 does not contain a complete closed area 600, the processor 110 can perform a first correction operation to complete the correction of the projection area 400 without considering the closed area 600.

[0057] Furthermore, when performing the first correction operation, using the first original symbol group and the first symbol group to correct the projection area 400 is less likely to significantly alter the projection area 400 compared to using the second original symbol group and the second symbol group. If the amount of change between the first original symbol group and the first symbol group is sufficient to complete the correction of the projection area 400, the processor 110 may preferentially use the first original symbol group and the first symbol group to perform the first correction operation, thereby completing the correction by slightly adjusting the projection area 400. If the amount of change between the first original symbol group and the first symbol group is insufficient to complete the correction of the projection area 400, then the processor 110 will use the second original symbol group and the second symbol group to perform the first correction operation.

[0058] Figure 9 A flowchart illustrating a method for correcting the projection area of ​​a projector according to another embodiment of the present invention is shown, wherein the method may be performed by, for example... Figure 1 The projection system 100 shown is implemented. In step S901, a correction pattern is projected by a projector to form a projection area, wherein the correction pattern includes a first original symbol group and a second original symbol group, wherein the second original symbol group surrounds the first original symbol group and the first original symbol group surrounds the center point of the correction pattern. In step S902, an image capturing device acquires a captured image containing the projection area, wherein the captured image includes a first symbol group corresponding to the first original symbol group and a second symbol group corresponding to the second original symbol group. In step S903, a processor performs first image recognition on the captured image to determine whether the captured image contains a closed region formed by complete lines. When the processor determines that the captured image does not contain a closed region, a first correction operation is performed; when the processor determines that the projection area in the captured image contains a complete closed region, a second correction operation is performed. In step S904, when performing the first correction operation, the projection area is corrected according to the first symbol group or the second symbol group in the captured image; when performing the second correction operation, the projection area is corrected according to the second symbol group in the captured image.

[0059] In summary, the projection system of the present invention can project a correction pattern using a projector and capture an image of the projection area using an image capturing device. The correction pattern may include a first set of original symbols and a second set of original symbols surrounding the first set of original symbols, which are respectively suitable for projection area correction in different situations. When the projection system can detect a closed area with a complete frame (e.g., a projection screen), the projection system can use the second set of original symbols to correct the projection area of ​​the projector. When the projection system cannot detect a closed area with a complete frame, the projection system can determine whether the second set of original symbols can be used to correct the projection area. The projection system can decide to use either the first set of original symbols or the second set of original symbols to correct the projection area based on the determination result. Accordingly, regardless of whether the projection system can detect a closed area with a complete frame, the projection system can determine an appropriate correction method to correct the projection area generated by the ultra-short-throw lens.

[0060] The above description is merely a preferred embodiment of the present invention and should not be construed as limiting the scope of the invention. Any simple equivalent changes and modifications made in accordance with the claims and description of the invention are still within the scope of this patent. Furthermore, no embodiment or claim of the present invention needs to achieve all the objectives, advantages, or features disclosed in the invention. In addition, the abstract and title (invention title) are only used to assist in patent document retrieval and are not intended to limit the scope of the invention. Furthermore, the terms "first," "second," etc., mentioned in this specification or claims are only used to name elements or distinguish different embodiments or scopes, and are not used to limit the upper or lower limit of the number of elements. The directional terms mentioned in this specification or claims, such as up, down, left, right, front, or back, are only for reference to the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the invention.

[0061] Explanation of reference numerals in the attached figures:

[0062] 100: Projection System

[0063] 110: Processor

[0064] 120: Projector

[0065] 130: Image capturing device

[0066] 300: Correction Pattern

[0067] 310, 320, 410, 420: Triangle

[0068] 400: Projection area

[0069] 450: Corrected projection area

[0070] 500: Capture Image

[0071] 600: Enclosed Area

[0072] a1, a2, a3, a4, a5, a6, a7, a8, b1, b2, b3, b4: Primitive notation

[0073] A1, A2, A3, A4, A5, A6, A7, A8, B1, B2, B3, B4: Marks

[0074] C1, C2, C3, C4, C1', C2', C3', C4': Vertices

[0075] D1, D2, D3, D4: corner points

[0076] O1, O2: Center point

[0077] S201, S202, S203, S204, S205, S206, S207, S208, S901, S902, S903, S904: Steps

[0078] θA, θB: included angles.

Claims

1. A method for calibrating the projection area of ​​a projector, characterized in that, include: A correction pattern is projected by the projector to form a projection area, wherein the correction pattern includes a first original symbol group and a second original symbol group, wherein the second original symbol group surrounds the first original symbol group and the first original symbol group surrounds the center point of the correction pattern. An image containing the projection area is obtained by means of an image capturing device, wherein the captured image includes a first symbol group corresponding to the first original symbol group and a second symbol group corresponding to the second original symbol group; The processor performs a first image recognition on the captured image to determine whether the captured image contains a closed region formed by complete lines. When the processor determines that the captured image does not contain the closed region, a first correction operation is performed. When the processor determines that the projected region in the captured image contains the complete closed region, a second correction operation is performed. When performing the first correction operation, the projection area is corrected according to the first or second marker group in the captured image; and When performing the second correction operation, the projection area is corrected according to the second group of symbols in the captured image.

2. The method according to claim 1, characterized in that, The projection area includes a first vertex, a second vertex, and a third vertex. The first primitive symbol group includes a first primitive symbol corresponding to the first vertex, a second primitive symbol corresponding to the second vertex, and a third primitive symbol corresponding to the third vertex. The first symbol group includes a first symbol corresponding to the first vertex, a second symbol corresponding to the second vertex, and a third symbol corresponding to the third vertex. The first primitive symbol, the second primitive symbol, and the third primitive symbol form a first triangle, and the first symbol, the second symbol, and the third symbol form a second triangle.

3. The method according to claim 2, characterized in that, The first triangle includes a first included angle corresponding to the first vertex, and the second triangle includes a second included angle corresponding to the first vertex; when performing the first correction operation, the step of correcting the projection area according to the first or second mark group in the captured image includes: In response to the absolute difference between the first included angle and the second included angle being greater than a threshold, it is determined to correct the projection area using the angular change between the first mark, the second mark, and the third mark of the first mark group and the first original mark, the second original mark, and the third original mark of the first original mark group.

4. The method according to claim 3, characterized in that, The second group of original symbols in the correction pattern includes a fourth original symbol corresponding to the first vertex, a fifth original symbol corresponding to the second vertex, and a sixth original symbol corresponding to the third vertex, wherein the distance between the first original symbol and the center point of the correction pattern is less than or equal to the distance between the fourth original symbol and the center point, the distance between the second original symbol and the center point is less than or equal to the distance between the fifth original symbol and the center point, and the distance between the third original symbol and the center point is less than or equal to the distance between the sixth original symbol and the center point.

5. The method according to claim 4, characterized in that, The second group of symbols in the captured image includes a fourth symbol corresponding to the fourth original symbol, a fifth symbol corresponding to the fifth original symbol, and a sixth symbol corresponding to the sixth original symbol. When performing the first correction operation, the step of correcting the projection area based on the first group of symbols or the second group of symbols in the captured image further includes: In response to the absolute difference between the first included angle and the second included angle being less than or equal to the threshold, it is determined to correct the projection area using the angular change between the fourth, fifth, and sixth marks of the second mark group and the fourth, fifth, and sixth marks of the second original mark group.

6. The method according to claim 5, characterized in that, The correction pattern further includes a seventh original symbol corresponding to the line connecting the first vertex and the second vertex, and the captured image further includes a seventh symbol corresponding to the line connecting the first vertex and the second vertex, wherein the method further includes: In response to the fact that the first included angle formed by the seventh original symbol, the fourth original symbol, and the fifth original symbol is smaller than the second included angle formed by the seventh symbol, the fourth symbol, and the fifth symbol, it is determined that the first triangle and the second triangle are used to correct the projection area.

7. The method according to claim 2, characterized in that, The second original symbol group of the correction pattern includes a fourth original symbol corresponding to the first vertex, a fifth original symbol corresponding to the second vertex, and a sixth original symbol corresponding to the third vertex, and the second symbol group of the captured image includes a fourth symbol corresponding to the fourth original symbol, a fifth original symbol corresponding to the fifth original symbol, and a sixth original symbol corresponding to the sixth original symbol. The step of correcting the projection area based on the first or second marker group in the captured image during the first correction operation includes: In response to the fact that at least one of the symbols corresponding to the fourth, fifth, and sixth symbols is not included in the captured image, it is determined to use the first, second, and third symbols of the first symbol group to correct the projection area.

8. The method according to claim 3, characterized in that, The step of correcting the projection area using the angular variation between the first, second, and third symbols of the first symbol group and the first, second, and third original symbols of the first original symbol group includes: The projection area is corrected by reducing the amount of angle change.

9. The method according to claim 2, characterized in that, Also includes: When the processor determines that the captured image contains the closed region but the projected region does not completely contain the closed region, it performs the first correction operation, including: The projected area is corrected using the angular variation between the first, second, and third symbols of the first symbol group and the first, second, and third original symbols of the first original symbol group.

10. The method according to claim 2, characterized in that, The second original symbol group of the correction pattern includes a fourth original symbol corresponding to the first vertex, a fifth original symbol corresponding to the second vertex, and a sixth original symbol corresponding to the third vertex; the second symbol group of the captured image includes a fourth symbol corresponding to the fourth original symbol, a fifth original symbol corresponding to the fifth original symbol, and a sixth original symbol corresponding to the sixth original symbol; when performing the second correction operation, the step of correcting the projection area according to the second symbol group in the captured image includes: Perform second image recognition on the captured image to detect a first corner point of the closed region, wherein the distance between the first corner point and the second center point of the projected region is less than the distance between the fourth marker and the second center point; and The projection area is corrected so that the distance between the fourth mark and the second center point is less than the distance between the first corner point and the second center point.

11. The method according to claim 10, characterized in that, Also includes: The second image recognition is performed on the captured image to detect the second corner point and the third corner point of the closed region, wherein the distance between the second corner point and the second center point is less than the distance between the fifth marker and the second center point, and the distance between the third corner point and the second center point is less than the distance between the sixth marker and the second center point; Obtain the first angle between the first straight line formed by the fourth mark and the fifth mark and the second straight line formed by the first corner point and the second corner point; Obtain the second included angle between the third line formed by the fourth mark and the sixth mark and the fourth line formed by the first corner point and the third corner point; and The projection area is corrected so that the first included angle and the second included angle are adjusted to zero.

12. The method according to claim 1, characterized in that, The correction pattern is a quadrilateral, the first original symbol group includes four original symbols, and the second original symbol group includes eight original symbols.

13. A projection system, characterized in that, The projection system includes a projector, an image capturing device, and a processor, wherein: The processor is coupled to the image capturing device and the projector, wherein the processor is configured to perform: A correction pattern is projected by the projector to form a projection area, wherein the correction pattern includes a first original symbol group and a second original symbol group, wherein the second original symbol group surrounds the first original symbol group and the first original symbol group surrounds the center point of the correction pattern. The image capturing device acquires a captured image containing the projection area, wherein the captured image includes a first symbol group corresponding to the first original symbol group and a second symbol group corresponding to the second original symbol group; Perform a first image recognition operation on the captured image to determine whether the captured image contains a closed region formed by complete lines. When the captured image does not contain the closed region, perform a first correction operation. When the projected region in the captured image contains the complete closed region, perform a second correction operation. When performing the first correction operation, the projection area is corrected according to the first or second marker group in the captured image; and When performing the second correction operation, the projection area is corrected according to the second group of symbols in the captured image.

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