Patent Publication Number: US-2022215782-A1

Title: Method for generating image with uniform brightness

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of China application serial no. 202110002798.3, filed on Jan. 4, 2021. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND 
     Technical Field 
     The disclosure relates to an image generation method and particularly relates to a method for generating an image with uniform brightness. 
     Description of Related Art 
     Generally, to achieve an image display effect over a large projection area, the entire projection image needs to be formed by splicing multiple sub-images respectively projected from multiple projection devices, and the multiple sub-images are partially superimposed with each other. In such a case, however, if the overlapping portions of the multiple sub-images are not adjusted, the entire image may have excessively high or low brightness in the overlapping areas between the sub-images, which impairs the image display effect over a large area. 
     SUMMARY 
     The disclosure provides a method for generating an image with uniform brightness, applicable to displaying an image with uniform brightness on a projection surface. 
     According to an embodiment of the disclosure, a method for generating an image with uniform brightness includes: providing a first sub-image having a first overlapping portion and a first non-overlapping portion; providing a second sub-image having a second overlapping portion and a second non-overlapping portion; and superimposing the first sub-image with the second sub-image through the first overlapping portion and the second overlapping portion. Brightness of the first overlapping portion of the first sub-image is complementary to brightness of the second overlapping portion of the second sub-image. 
     Based on the above, the method for generating an image with uniform brightness according to the disclosure displays an image with uniform brightness by providing two images that are partially superimposed with each other. 
     The disclosure may be understood by referring to the following detailed description with reference to the accompanying drawings. It should be noted that, in order to facilitate the reader&#39;s understanding and the conciseness of the drawings, the drawings in the disclosure may only depict a part of a display device, and specific elements in the drawings may not be drawn according to actual scales. In addition, the number and size of each element in the drawings are only for illustration, and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the disclosure and, together with the description, serve to explain the principles of the disclosure. 
         FIG. 1A  is a schematic diagram of an electronic device and sub-images according to an embodiment of the disclosure. 
         FIG. 1B  is a flowchart of a method for generating an image with uniform brightness according to an embodiment of the disclosure. 
         FIG. 2  is a schematic diagram of an image with uniform brightness according to an embodiment of the disclosure. 
         FIG. 3  is a schematic diagram of sub-images according to another embodiment of the disclosure. 
         FIG. 4  is a schematic diagram of sub-images according to another embodiment of the disclosure. 
         FIG. 5  is a schematic diagram of sub-images according to another embodiment of the disclosure. 
         FIG. 6A  to  FIG. 6C  are schematic diagrams of measurement of the brightness of sub-images according to an embodiment of the disclosure. 
         FIG. 7A  and  FIG. 7B  are schematic diagrams of measurement of the brightness of an image according to an embodiment of the disclosure. 
         FIG. 8A  and  FIG. 8B  are schematic diagrams of measurement of the brightness of sub-images according to another embodiment of the disclosure. 
         FIG. 9A  and  FIG. 9B  are schematic diagrams of measurement of the brightness of sub-images according to yet another embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS 
     Reference will now be made to the exemplary embodiments of the disclosure, and examples of the exemplary embodiments are illustrated in the accompanying drawings. Wherever possible, the same reference numerals are used in the drawings and description to indicate the same or similar parts. 
     It should be noted that, in order to facilitate the reader&#39;s understanding and the conciseness of the drawings, the drawings in the disclosure may only depict a part of an electronic device, and specific elements in the drawings may not be drawn according to actual scales. In addition, the number and size of each element in the drawings are only for illustration, and are not intended to limit the scope of the disclosure. For example, for clarity&#39;s sake, relative size, thickness and position of each film layer, region and/or structure may be reduced or enlarged. 
     Throughout the specification and claims of the disclosure, certain words are used to refer to specific elements. Those skilled in the art should understand that electronic device manufacturers may refer to the same elements by different names. This specification does not intend to distinguish those elements with the same function but different names. In the following description and claims, the words “have” and “include” are open-ended words, so they should be interpreted as “including but not limited to . . . ” 
     The terms “about,” “equal,” “same,” “substantially” or “approximately” mentioned herein generally represent falling within 10% of a given value or range, or represent falling within 5%, 3%, 2%, 1% or 0.5% of the given value or range. In addition, the terms “the given range is from a first value to a second value” and “the given range falls within the range of the first value to the second value” mean that the given range includes the first value, the second value and other values between the first value and the second value. 
     In some embodiments of the disclosure, the terms related to bonding and connecting mentioned in the specification, such as “connected,” “interconnected,” etc., unless specifically defined, may mean that two structures are directly in contact with each other, or that two structures are not directly in contact with each other but there are other structures located between the two structures. The terms related to bonding and connecting may also include a situation that both structures are movable or both structures are fixed. In addition, the terms “electrical connection” and “coupling” include any direct and indirect electrical connection means. 
     In the following embodiments, the same or similar elements may be denoted by the same or similar reference numerals, and descriptions thereof are omitted. In addition, the features in different embodiments may be combined arbitrarily as long as they do not violate the spirit of the disclosure or there is no confliction, and simple equivalent changes and modifications made in accordance with this specification or claims still fall within the scope of the disclosure. Moreover, the terms “first” and “second” mentioned in the specification or claims are only used to name different elements or to distinguish different embodiments or ranges, and are not intended to limit an upper limit or a lower limit of the number of the elements, and are not intended to limit a manufacturing sequence or an arrangement sequence of the elements. 
     It should be understood that the features in several different embodiments may be replaced, recombined or mixed, without departing from the spirit of the disclosure, to form other embodiments. The features in different embodiments may be combined arbitrarily as long as they do not violate the spirit of the disclosure or there is no confliction. 
       FIG. 1A  is a schematic diagram of an electronic device and sub-images according to an embodiment of the disclosure. Referring to  FIG. 1A , the electronic device  100  includes a display  110  and an optical system  120 . The display  110  is coupled to the optical system  120 . The electronic device  100  may project an image displayed by the display  110  to a projection surface through the optical system  120  for the projection surface to correspondingly display the display content of the display  110 . The image of the disclosure includes, for example, an image, a pattern, a sign, text, a number, etc., but the disclosure is not limited thereto. In this embodiment, the electronic device  100  includes a head-up display (HUD), but not limited thereto. As shown in  FIG. 1A , the optical system  120  may project a first sub-image  131  and a second sub-image  141  displayed by the display  110  to, for example, a windshield of a car for the windshield of the car to display the first sub-image  131  and the second sub-image  141 . In this embodiment, the display  110  of the disclosure alternately displays the first sub-image  131  and the second sub-image  141  in a high-frequency switching manner. The high-frequency switching refers to that when human eyes watch the first sub-image  131  and the second sub-image  141  switched at a high frequency, the display switching speed of the first sub-image  131  and the second sub-image  141  creates persistence of vision for the eyes of the viewer, and as a result, the first sub-image  131  and the second sub-image  141  appear to be displayed simultaneously to the viewer, but the disclosure is not limited thereto. In another embodiment, the display  110  may generate the first sub-image  131  and the second sub-image  141  at the same time, and project the first sub-image  131  and the second sub-image  141  to the projection surface through the optical system  120 . 
     In this embodiment, the display  110  may include, for example, a liquid crystal display, an organic light emitting diode (OLED) display, an inorganic light emitting diode (ILED) display, a Mini-LED display, a Micro-LED display, a quantum dot (QD) display, a quantum dot diode (QLED/QDLED) display, an electro-phoretic displays, etc., but the disclosure is not limited thereto. In this embodiment, the optical system  120  may include related optical elements and optomechanical elements for sequentially displaying the first sub-image  131  and the second sub-image  141  projected to different positions (but partially overlapping) of the projection surface, but the disclosure is not limited thereto. Moreover, the number of sub-images that the electronic device  100  of the disclosure switches to display is not limited to two as shown in  FIG. 1A . The number of sub-images that the electronic device  100  switches to display may be determined according to different usage scenarios, equipment resources or user requirements. In addition, in some embodiments of the disclosure, the electronic device  100  may also include a plurality of displays and a plurality of optical systems for displaying sub-images individually (simultaneously or sequentially). 
       FIG. 1B  is a flowchart of a method for generating an image with uniform brightness according to an embodiment of the disclosure.  FIG. 2  is a schematic diagram of an image with uniform brightness according to an embodiment of the disclosure. Referring to  FIG. 1A  to FIG.  2 , the electronic device  100  may perform the following steps S 101 , S 103 , and S 105  to generate an image with uniform brightness. In step S 101 , the electronic device  100  may provide the first sub-image  131  having a first overlapping portion  131 _ 1  and a first non-overlapping portion  131 _ 2 . As shown in  FIG. 1A , the electronic device  100  may display the first sub-image  131  in a first display range  130 . Two boundaries of the first display range  130  in the direction P 1  are, for example, the position a 0  and the position a 4 . In this embodiment, the range of the first overlapping portion  131 _ 1  of the first sub-image  131  in the direction P 1  is from the position a 2  to the position a 3 . The range of the first non-overlapping portion  131 _ 2  of the first sub-image  131  in the direction P 1  is from the position a 1  to the position a 2 . The first non-overlapping portion  131 _ 2  of the first sub-image  131  may have a brightness value B 2 . The first non-overlapping portion  131 _ 2  of the first sub-image  131  may have a distribution of brightness in a linear form, wherein the distribution of brightness may have a plurality of fixed values. In some embodiments, the plurality of fixed values are substantially the same. In other embodiments, any difference within plus or minus 10% between the fixed values is regarded as the fixed values referred to in the disclosure. As shown in  FIG. 1A , the first overlapping portion  131 _ 1  of the first sub-image  131  may have a brightness value B 1 . In this embodiment, the direction P 1  is perpendicular to the direction P 2 . The direction P 1  may be, for example, the horizontal direction of the projection plane, and the direction P 2  may be, for example, the vertical direction of the projection plane. 
     In step S 103 , the electronic device  100  may provide the second sub-image  141  having a second overlapping portion  141 _ 1  and a second non-overlapping portion  141 _ 2 . As shown in  FIG. 1A , the electronic device  100  may display the second sub-image  141  in a second display range  140 . Two boundaries of the second display range  140  in the direction P 1  are, for example, the position b 0  and the position b 4 . In this embodiment, the range of the second overlapping portion  141 _ 1  of the second sub-image  141  in the direction P 1  is from the position b 1  to the position b 2 . The range of the second non-overlapping portion  141 _ 2  of the second sub-image  141  in the direction P 1  is from the position b 2  to the position b 3 . The second non-overlapping portion  141 _ 2  of the second sub-image  141  may have a brightness value B 2 , and the second non-overlapping portion  141 _ 2  of the second sub-image  141  may have a distribution of brightness in a linear form, wherein the distribution of brightness may have a plurality of fixed values, and the plurality of fixed values are substantially the same. As shown in  FIG. 1A , the first overlapping portion  141 _ 1  of the second sub-image  141  may have a brightness value B 1 ′. 
     In step S 105 , the electronic device  100  may superimpose the first sub-image  131  with the second sub-image  141  through the first overlapping portion  131 _ 1  and the second overlapping portion  141 _ 1 . As shown in  FIG. 1A , the range of the first display range  130  from the position a 2  to the position a 4  in the direction P 1  may overlap the range of the second display range  140  from the position b 0  to the position b 2  in the direction P 1 . In this embodiment, the brightness value B 1  of the first overlapping portion  131 _ 1  of the first sub-image  131  is complementary to the brightness value B 1 ′ of the second overlapping portion  141 _ 1  of the second sub-image  141 . For example, the brightness value B 1  and the brightness value B 1 ′ may each be half of the brightness value B 2 , or the sum of the brightness value B 1  and the brightness value B 1 ′ may be substantially equal to the brightness value B 2 . 
     As shown in  FIG. 1A  and  FIG. 2 , the electronic device  100  may sequentially project the first sub-image  131  and the second sub-image  141  to a surface S 1  of a projection target  200  (such as the windshield of a car or any projection surface), wherein the surface S 1  may be a flat surface or a curved surface. In this regard, the viewer may see an image  211  as shown in  FIG. 2 . The image  211  is the result of partially superimposing the first sub-image  131  and the second sub-image  141 . Two boundaries of the image range  210  of the image  211  in the direction P 1  are the position c 0  and the position c 5 . In this regard, the position c 0  of the image range  210  corresponds to the position a 0  of the first display range  130 . The position c 1  of the image range  210  corresponds to the position a 1  of the first display range  130 . The position c 2  of the image range  210  corresponds to the position a 2  of the first display range  130  and the position b 1  of the second display range  140 . The position c 3  of the image range  210  corresponds to the position a 3  of the first display range  130  and the position b 2  of the second display range  140 . The position c 4  of the image range  210  corresponds to the position b 3  of the second display range  140 . The position c 5  of the image range  210  corresponds to the position b 4  of the second display range  140 . 
     In this embodiment, the first overlapping portion  131 _ 1  and the second overlapping portion  141 _ 1  overlap, so that the first sub-image  131  and the second sub-image  141  form the image  211  with a larger image area. Moreover, since the brightness value B 1  of the first overlapping portion  131 _ 1  of the first sub-image  131  is complementary to the brightness value B 1 ′ of the second overlapping portion  141 _ 1  of the second sub-image  141 , the brightness of the image obtained by overlapping the first overlapping portion  131 _ 1  and the second overlapping portion  141 _ 1  is increased, and is substantially the same as the brightness of the first non-overlapping portion  131 _ 2  and the brightness of the second non-overlapping portion  141 _ 2 . Therefore, the image  211  of this embodiment may present a display result with the uniform brightness value B 2  from the position c 1  to the position c 4  in the direction P 1 . It should be noted that the “complementary” mentioned in the disclosure means that the sum of the brightness of the corresponding overlapping portions of the two sub-images is greater than the brightness before the addition. For example, referring to  FIG. 1A  and  FIG. 2 , the brightness value B 2  obtained by overlapping the first overlapping portion  131 _ 1  of the first sub-image  131  and the second overlapping portion  141 _ 1  of the second sub-image  141  at the position c 2  is greater than the brightness value B 1  of the first overlapping portion  131 _ 1  and the brightness value B 1 ′ of the second overlapping portion  141 _ 1 , and it may be said that the brightness value B 1  of the first overlapping portion  131 _ 1  is complementary to the brightness value B 1 ′ of the second overlapping portion  141 _ 1 . 
     It should be noted that the sub-images and image contents (or display pictures) of the images in the disclosure are not limited to  FIG. 1A  and  FIG. 2 . In addition, the term “uniform brightness” mentioned in each embodiment of the disclosure may include, for example, an image display result that an image has the same gray level in a pure color picture and the overall brightness distribution difference of the image is less than, for example, 10%, but the disclosure is not limited thereto. The term “uniform brightness” mentioned in each embodiment of the disclosure may also include, for example, an image display result that the range of the difference in the overall brightness distribution is not easily noticeable by human eyes or an image display result that the overall brightness value is consistent. 
       FIG. 3  is a schematic diagram of sub-images according to another embodiment of the disclosure. Referring to  FIG. 1A  and  FIG. 3 , in some embodiments of the disclosure, the electronic device  100  of  FIG. 1A  may also provide the first display range  330  and the second display range  340  as shown in  FIG. 3  to synthesize an image with uniform brightness. As shown in  FIG. 3 , in this embodiment, the electronic device  100  may provide the first sub-image  331  having the first overlapping portion  331 _ 1  and the first non-overlapping portion  331 _ 2 . The electronic device  100  may display the sub-image  331  in the first display range  330 . Two boundaries of the first display range  330  in the direction P 1  are, for example, the position d 0  and the position d 4 . In this embodiment, the range of the first overlapping portion  331 _ 1  of the first sub-image  331  in the direction P 1  is from the position d 2  to the position d 3 . The range of the first non-overlapping portion  331 _ 2  of the first sub-image  331  in the direction P 1  is from the position d 1  to the position d 2 . The first non-overlapping portion  331 _ 2  of the first sub-image  331  may have the brightness value B 2 , and the first overlapping portion  331 _ 1  of the first sub-image  331  may have a distribution of brightness in a linear form. 
     In this embodiment, the electronic device  100  may provide the second sub-image  341  having the second overlapping portion  341 _ 1  and the second non-overlapping portion  341 _ 2 . The electronic device  100  may display the sub-image  341  in the second display range  340 . Two boundaries of the second display range  340  in the direction P 1  are, for example, the position e 0  and the position e 4 . In this embodiment, the range of the second overlapping portion  341 _ 1  of the second sub-image  341  in the direction P 1  is from the position e 1  to the position e 2 . The range of the second non-overlapping portion  341 _ 2  of the second sub-image  341  in the direction P 1  is from the position e 2  to the position e 3 . The second non-overlapping portion  341 _ 2  of the second sub-image  341  may have the brightness value B 2 , and the second overlapping portion  341 _ 1  of the second sub-image  341  may have a distribution of brightness in a linear form. 
     In this embodiment, the electronic device  100  may superimpose the first sub-image  331  with the second sub-image  341  through the first overlapping portion  331 _ 1  and the second overlapping portion  341 _ 1 . As shown in  FIG. 3 , the range of the first display range  330  from the position d 2  to the position d 4  in the direction P 1  may overlap the range of the second display range  340  from the position e 0  to the position e 2  in the direction P 1 . In this embodiment, the brightness of the first overlapping portion  331 _ 1  of the first sub-image  331  is complementary to the brightness of the second overlapping portion  341 _ 1  of the second sub-image  341 . For example, in terms of the relationship between the brightness and position of the image (coordinate axes), the first overlapping portion  331 _ 1  of the first sub-image  331  may have a distribution of brightness in a linear form with a slope of −1, for example, and the second overlapping portion  341 _ 1  of the second sub-image  341  may have a distribution of brightness in a linear form with a slope of 1, for example. Therefore, the electronic device  100  may sequentially or simultaneously project the first sub-image  331  and the second sub-image  341  to the surface S 1  as shown in  FIG. 2  for the viewer to see the image  211  with the uniform brightness value B 2  as shown in the embodiment of  FIG. 2 . 
       FIG. 4  is a schematic diagram of sub-images according to another embodiment of the disclosure. Referring to  FIG. 1A  and  FIG. 4 , in some embodiments of the disclosure, the electronic device  100  of  FIG. 1A  may also provide the first display range  430  and the second display range  440  as shown in  FIG. 4  to synthesize an image with uniform brightness. As shown in  FIG. 4 , in this embodiment, the electronic device  100  may provide the first sub-image  431  having the first overlapping portions  431 _ 11  and  431 _ 12  and the first non-overlapping portion  431 _ 2 . The electronic device  100  may display the sub-image  431  in the first display range  430 . Two boundaries of the first display range  430  in the direction P 1  are, for example, the position f 0  and the position f 5 . In this embodiment, the range of the first overlapping portions  431 _ 11  and  431 _ 12  of the first sub-image  431  in the direction P 1  is from the position f 2  to the position f 4 . The range of the first non-overlapping portion  431 _ 2  of the first sub-image  431  in the direction P 1  is from the position f 1  to the position f 2 . The first non-overlapping portion  431 _ 2  of the first sub-image  431  may have the brightness value B 2 , and the first overlapping portions  431 _ 11  and  431 _ 12  of the first sub-image  431  may have a distribution of brightness in a stepped form. In this embodiment, the first overlapping portion  431 _ 11  of the first sub-image  431  may have the brightness value B 3  in the range from the position f 2  to the position f 3  in the direction P 1 , and the first overlapping portion  431 _ 12  of the first sub-image  431  may have the brightness value B 4  in the range from the position f 3  to the position f 4  in the direction P 1 . 
     In this embodiment, the electronic device  100  may provide the sub-image  441  having the second overlapping portions  441 _ 11  and  441 _ 12  and the second non-overlapping portion  441 _ 2 . The electronic device  100  may display the sub-image  441  in the second display range  440 . Two boundaries of the second display range  440  in the direction P 1  are, for example, the position g 0  and the position g 5 . In this embodiment, the range of the second overlapping portions  441 _ 11  and  441 _ 12  of the second sub-image  441  in the direction P 1  is from the position g 1  to the position g 3 . The range of the second non-overlapping portion  441 _ 2  of the second sub-image  441  in the direction P 1  is from the position g 3  to the position g 4 . The second non-overlapping portion  441 _ 2  of the second sub-image  441  may have the brightness value B 2 , and the second overlapping portion  441 _ 1  of the second sub-image  441  may have a distribution of brightness in a stepped form. In this embodiment, the second overlapping portion  441 _ 12  of the second sub-image  441  may have the brightness value B 5  in the range from the position g 2  to the position g 3  in the direction P 1 , and the second overlapping portion  441 _ 11  of the second sub-image  441  may have the brightness value B 6  in the range from the position g 1  to the position g 2  in the direction P 1 . 
     In this embodiment, the electronic device  100  may superimpose the first sub-image  431  with the second sub-image  441  through the first overlapping portions  431 _ 11  and  431 _ 12  and the second overlapping portions  441 _ 11  and  441 _ 12 . As shown in  FIG. 4 , the range of the first display range  430  from the position f 2  to the position f 5  in the direction P 1  may overlap the range of the second display range  440  from the position g 0  to the position g 3  in the direction P 1 . In this embodiment, the brightness value B 4  of the first overlapping portion  431 _ 11  of the first sub-image  431  is complementary to the brightness value B 5  of the second overlapping portion  441 _ 12  of the second sub-image  441 . The brightness value B 3  of the first overlapping portion  431 _ 12  of the first sub-image  431  is complementary to the brightness value B 6  of the second overlapping portion  441 _ 11  of the second sub-image  441 . For example, the sum of the brightness value B 3  of the first overlapping portion  431 _ 12  of the first sub-image  431  in the range from the position f 2  to the position f 3  in the direction P 1  and the brightness value B 6  of the second overlapping portion  441 _ 11  of the second sub-image  441  in the range from the position g 1  to the position g 2  in the direction P 1  is equal to the brightness value B 2 . The sum of the brightness value B 4  of the first overlapping portion  431 _ 11  of the first sub-image  431  in the range from the position f 3  to the position f 4  in the direction P 1  and the brightness value B 5  of the second overlapping portion  441 _ 12  of the second sub-image  441  in the range from the position g 2  to the position g 3  in the direction P 1  is equal to the brightness value B 2 . Therefore, the electronic device  100  may sequentially or simultaneously project the first sub-image  431  and the second sub-image  441  to the surface S 1  as shown in  FIG. 2  for the viewer to see the image  211  with the uniform brightness value B 2  as shown in the embodiment of  FIG. 2 . 
       FIG. 5  is a schematic diagram of sub-images according to another embodiment of the disclosure. Referring to  FIG. 1A  and  FIG. 5 , in some embodiments of the disclosure, the electronic device  100  of  FIG. 1A  may also provide the first display range  530  and the second display range  540  as shown in  FIG. 5  to synthesize an image with uniform brightness. As shown in  FIG. 5 , in this embodiment, the electronic device  100  of  FIG. 1A  may display the sub-image  531  in the first display range  530  and provide the first sub-image  531  having the first overlapping portion  531 _ 1  and the first non-overlapping portion  531 _ 2 . Two boundaries of the first display range  530  in the direction P 1  are, for example, the position h 0  and the position h 4 . In this embodiment, the range of the first overlapping portion  531 _ 1  of the first sub-image  531  in the direction P 1  is from the position h 2  to the position h 3 . The range of the first non-overlapping portion  531 _ 2  of the first sub-image  531  in the direction P 1  is from the position h 1  to the position h 2 . The first non-overlapping portion  531 _ 2  of the first sub-image  531  may have the brightness value B 2 , and the first overlapping portion  531 _ 1  of the first sub-image  531  may have a distribution of brightness in a non-linear form. 
     In this embodiment, the electronic device  100  may display the sub-image  541  in the second display range  540  and provide the sub-image  541  having the second overlapping portion  541 _ 1  and the second non-overlapping portion  541 _ 2 . Two boundaries of the second display range  540  in the direction P 1  are, for example, the position i 0  and the position i 4 . In this embodiment, the range of the second overlapping portion  541 _ 1  of the second sub-image  541  in the direction P 1  is from the position i 1  to the position i 2 . The range of the second non-overlapping portion  541 _ 2  of the second sub-image  541  in the direction P 1  is from the position i 2  to the position i 3 . The second non-overlapping portion  541 _ 2  of the second sub-image  541  may have the brightness value B 2 , and the second overlapping portion  541 _ 1  of the second sub-image  541  may have a distribution of brightness in a non-linear form. 
     In this embodiment, the electronic device  100  may superimpose the first sub-image  531  with the second sub-image  541  through the first overlapping portion  531 _ 1  and the second overlapping portion  541 _ 1 . As shown in  FIG. 5 , the range of the first display range  530  from the position h 2  to the position h 4  in the direction P 1  may overlap the range of the second display range  540  from the position i 0  to the position i 2  in the direction P 1 . In this embodiment, the brightness of the first overlapping portion  531 _ 1  of the first sub-image  531  is complementary to the brightness of the second overlapping portion  541 _ 1  of the second sub-image  541 . Therefore, the electronic device  100  may sequentially or simultaneously project the first sub-image  531  and the second sub-image  541  to the surface S 1  as shown in  FIG. 2  for the viewer to see the image  211  with the uniform brightness value B 2  as shown in the embodiment of  FIG. 2 . 
     Referring to  FIG. 1A  again, which is taken as an illustration of proof, one proof method of the disclosure is that, for example, the tester may first shield the optical system  120  of the electronic device  100  from projecting the second sub-image  141 , and capture the first sub-image  131  through an image capturing device (such as a charge-coupled device (CCD)) in an environment without external interference light. For the first captured image corresponding to the first sub-image  131  obtained by the image capturing device, the tester may arbitrarily measure the brightness value of one point (such as the measurement points T 1  and T 2 ) of the areas respectively corresponding to the first overlapping portion  131 _ 1  and the first non-overlapping portion  131 _ 2  in the first captured image. Then, the tester may shield the optical system  120  of the electronic device  100  from projecting the first sub-image  131 , and capture the second sub-image  141  through the image capturing device in an environment without external interference light. For the second captured image corresponding to the second sub-image  141  obtained by the image capturing device, the tester may arbitrarily measure the brightness value of one point (such as the measurement points T 3  and T 4 ) of the areas respectively corresponding to the second overlapping portion  141 _ 1  and the second non-overlapping portion  141 _ 2  in the second captured image. Therefore, according to the obtained brightness value sensing results, the tester may determine whether the distribution of brightness meets the brightness distribution design of the embodiment of  FIG. 1A  of the disclosure for the first overlapping portion  131 _ 1  and the first non-overlapping portion  131 _ 2  of the first sub-image  131  and the second overlapping portion  141 _ 1  and the second non-overlapping portion  141 _ 2  of the second sub-image  141 , which may effectively show whether to use the technique of the disclosure to realize the product. Moreover, such a proof method may also be applied to verify the technical solutions of the brightness distribution designs of the sub-images in the embodiments shown in  FIG. 3  to  FIG. 5 . 
     Furthermore, another proof method of the disclosure may be that the tester operates the electronic device  100  to project a pure color picture instead of the special pattern shown in  FIG. 1A . For example, the projected pure color picture may be a rectangle. For example, the tester may first shield the optical system  120  of the electronic device  100  from projecting the second pure color sub-image, and capture the first pure color sub-image through an image capturing device. For the first pure color captured image corresponding to the first pure color sub-image obtained by the image capturing device, the tester may arbitrarily measure multiple brightness values of multiple points of the areas respectively corresponding to the overlapping portion and the non-overlapping portion in the first pure color captured image, and obtain the average value of the multiple brightness values. Then, the tester may shield the optical system  120  of the electronic device  100  from projecting the first pure color sub-image, and capture the second pure color sub-image through the image capturing device. For the second pure color captured image corresponding to the second pure color sub-image obtained by the image capturing device, the tester may arbitrarily measure multiple brightness values of multiple points of the areas respectively corresponding to the overlapping portion and the non-overlapping portion in the second pure color captured image, and obtain the average value of the multiple brightness values. Therefore, according to the obtained average value sensing results, the tester may determine whether the distribution of brightness meets the brightness distribution design of the embodiment of  FIG. 1A  of the disclosure for the first overlapping portion  131 _ 1  and the first non-overlapping portion  131 _ 2  of the first sub-image  131  and the second overlapping portion  141 _ 1  and the second non-overlapping portion  141 _ 2  of the second sub-image  141 , which may effectively show whether to use the technique of the disclosure to realize the product. Moreover, this proof method may also be applied to verify the technical solutions of the brightness distribution designs of the sub-images in the embodiments shown in  FIG. 3  to  FIG. 5 . 
       FIG. 6A  to  FIG. 6C  are schematic diagrams of measurement of the brightness of sub-images according to an embodiment of the disclosure. Referring to  FIG. 6A  to  FIG. 6C , another proof method of the disclosure may be that the tester operates the electronic device to project the first sub-image  631  with a color pattern as shown in  FIG. 6A . For example, the tester may first shield the optical system of the electronic device from projecting the second sub-image, and capture the first sub-image  631  with the color pattern through an image capturing device in an environment without external interference light. For the first color captured image corresponding to the first sub-image  631  with the color pattern obtained by the image capturing device, the tester may perform brightness measurement on the areas respectively corresponding to the first overlapping portion  631 _ 1  and the first non-overlapping portion  631 _ 2  in the first color captured image according to multiple measurement points  601 _ 1  to  601 _M on the brightness measurement line SD (which may be substantially parallel to the image stitching direction, for example) to obtain multiple pieces of corresponding brightness information. In this regard, for example, the tester may perform brightness measurement at multiple equidistant measurement points  601 _ 1  to  601 _N in the first non-overlapping portion  631 _ 2  along the brightness measurement line SD, and the tester may perform brightness measurement at multiple equidistant measurement points  601 _(N+1) to  601 _M in the first overlapping portion  631 _ 1  along the brightness measurement line SD, wherein M is a positive integer. The measurement density of the first overlapping portion  631 _ 1  may be higher than the measurement density of the first non-overlapping portion  631 _ 2 . In other words, the fixed distance between every two adjacent points of the measurement points  601 _(N+1) to  601 _M may be less than the fixed distance between every two adjacent points of the measurement points  601 _ 1  to  601 _N, but the disclosure is not limited thereto. In an embodiment, the fixed distance between every two adjacent points of the measurement points  601 _(N+1) to  601 _M may be greater than or equal to the fixed distance between every two adjacent points of the measurement points  601 _ 1  to  601 _N. In this regard, the tester may create the gamma curve of each color as shown in  FIG. 6B  according to the multiple pieces of brightness information of the measurement points  601 _ 1  to  601 _N of the first non-overlapping portion  631 _ 2 , wherein N is a positive integer. The gamma curve of each color may include, for example, the red gamma curve RG 1 , the green gamma curve GG 1 , and the blue gamma curve BG 1 , and the gamma curve represents the relationship between gray level and normalized brightness. Then, the tester may create the gamma curve of each color as shown in  FIG. 6C  according to the multiple pieces of brightness information of the measurement points  601 _(N+1) to  601 _M of the first overlapping portion  631 _ 1 . The gamma curve of each color may include, for example, the red gamma curve RG 2 , the green gamma curve GG 2 , and the blue gamma curve BG 2 . Accordingly, the tester may operate the electronic device to project the second sub-image with another color pattern, and obtain the gamma curve of each color of the overlapping portion and the non-overlapping portion as described above. In other words, the tester may determine whether the result of the gamma curve of each color of the color sub-image respectively in the overlapping portion and the non-overlapping portion has the difference as shown in  FIG. 6B  and  FIG. 6C  to effectively determine whether the distribution of brightness meets the brightness distribution design of one of  FIG. 1A  and  FIG. 3  to  FIG. 5  of the disclosure, which may effectively show whether to use the technique of the disclosure to realize the product. 
     In addition, the brightness measurement line SD used in this proof method is not limited to the form perpendicular to the image stitching line DD shown in  FIG. 6A . In this regard, the proof method may use any measurement line, which may pass through the geometric center of the sub-image, for example, and the any measurement line may pass through the overlapping portion and the non-overlapping portion of each sub-image (such as the first sub-image  131  and the second sub-image  141  of  FIG. 1A ). 
       FIG. 7A  and  FIG. 7B  are schematic diagrams of measurement of the brightness of an image according to an embodiment of the disclosure. Referring to  FIG. 7A  and  FIG. 7B , another proof method of the disclosure may be that the tester captures the image range  210  as shown in  FIG. 2  to obtain the captured image range  710  as shown in  FIG. 7A . The tester may perform brightness measurement at multiple equidistant measurement points on the captured image  711  (corresponding to the image  211  of the image range  210 ) in the captured image range  710  along the brightness measurement line SD to obtain the brightness distribution result as shown in  FIG. 7B . The brightness measurement line SD is perpendicular to the image stitching line X L  and/or the image stitching line X R . According to the relationship between brightness and position as shown in  FIG. 7B , since the image  211  of  FIG. 2  has uniform brightness, the brightness  701 _ 1  to  701 _P respectively outside the image stitching line X L  and the image stitching line X R  and between the image stitching line X L  and the image stitching line X R  may have substantially the same or similar brightness value B 2  (the brightness distribution difference is less than 10%, for example). Accordingly, the tester may effectively prove that the image provided by the electronic device has an image display result with uniform brightness. It should be noted that the brightness measurement line SD is not limited to the form perpendicular to the image stitching line X L  and/or the image stitching line X R  shown in  FIG. 7A . The proof method may use any measurement line, which may pass through the geometric center of the sub-image, for example, and the any measurement line may pass through the overlapping portion and the non-overlapping portion of each sub-image (such as the first sub-image  131  and the second sub-image  141  of  FIG. 1A ). For example, like the brightness measurement line SD′ additionally marked in  FIG. 7A , the brightness measurement line SD′ may be an oblique straight line passing through the geometric center P of the captured image  711 , and the brightness measurement line SD′ passes through the first overlapping portion  711 _ 1  of the first sub-captured image, the first non-overlapping portion  711 _ 2  of the first sub-captured image, the second non-overlapping portion  712 _ 2  of the second sub-captured image, and the first overlapping portion  712 _ 1  of the second sub-captured image. 
       FIG. 8A  and  FIG. 8B  are schematic diagrams of measurement of the brightness of sub-images according to another embodiment of the disclosure. Referring to  FIG. 8A  and  FIG. 8B , the tester may first shield the optical system of the electronic device from projecting the second sub-image to capture the first sub-image, so as to obtain the first sub-captured image range  830  as shown in  FIG. 8A . Then, the tester may shield the optical system of the electronic device from projecting the first sub-image to capture the second sub-image, so as to obtain the second sub-captured image range  840  as shown in  FIG. 8A . The tester may perform brightness measurement at multiple equidistant measurement points on the first sub-captured image  831  in the first sub-captured image range  830  along the brightness measurement line SD 1  to obtain the brightness distribution result of the brightness  801 _ 1  to  801 _R as shown in  FIG. 8B , wherein R is a positive integer. The brightness measurement line SD 1  is perpendicular to the image stitching line X L1  and the image stitching line X R1 . The tester may perform brightness measurement at multiple equidistant measurement points on the second sub-captured image  841  in the second sub-captured image range  840  along the brightness measurement line SD 2  to obtain the brightness distribution result of the brightness  802 _ 1  to  802 _T as shown in  FIG. 8B , wherein T is a positive integer. The brightness measurement line SD 2  is perpendicular to the image stitching line X L2  and the image stitching line X R2 . It should be noted that the combined result of the first sub-captured image  831  and the second sub-captured image  841  is similar to the captured image  711  of  FIG. 7A . The position of the image stitching line X L1  in the image may correspondingly overlap the image stitching line X L2 , and the position of the image stitching line X R1  in the image may correspondingly overlap the image stitching line X R2 . 
     In this embodiment, according to the brightness distribution result of the brightness  801 _ 1  to  801 _R, the tester may prove that one side of the first sub-captured image  831  along the image stitching line X L1  has the first non-overlapping portion  831 _ 2  with uniform brightness of the brightness value B 2 , and the first overlapping portion  831 _ 1  having a distribution of brightness in a linear form is between the image stitching line X L1  and the image stitching line X R1 . According to the brightness distribution result of the brightness  802 _ 1  to  802 _T, the tester may prove that one side of the second sub-captured image  841  along the image stitching line X R2  has the second non-overlapping portion  841 _ 2  with uniform brightness of the brightness value B 2 , and the second overlapping portion  841 _ 1  having a distribution of brightness in a linear form is between the image stitching line X L2  and the image stitching line X R2 . In addition, the tester may select the brightness  801 _S corresponding to one point of the first overlapping portions  831 _ 1  among the brightness  801 _ 1  to  801 _R from the reference position X 1 , and the tester may select the brightness  802 _U corresponding to one point of the second overlapping portion  841 _ 1  among the brightness  802 _ 1  to  802 _T from the reference position X 2 , wherein S and U are positive integers. The position of the reference position X 1  in the image may correspondingly overlap the reference position X 2 . Therefore, the tester may add the brightness value Bj of the brightness  801 _S to the brightness value Bk of the brightness  802 _U. If the sum of the brightness value Bj and the brightness value Bk is substantially equal to the brightness value B 2 , it means that the electronic device of this test adopts the technique of the brightness distribution design of the sub-images in  FIG. 3  of the disclosure to achieve the display effect of providing an image with uniform brightness. 
     However, this proof method is not limited to proving the brightness distribution design of the sub-images in the embodiment of  FIG. 3  of the disclosure. If a brightness measurement technique the same as this proof method is applied to each sub-image in the embodiment of  FIG. 5  of the disclosure to obtain the brightness distribution result of each sub-image, it may also show whether the electronic device to be tested adopts the brightness distribution design of the sub-images in the embodiment of  FIG. 5  of the disclosure. 
       FIG. 9A  and  FIG. 9B  are schematic diagrams of measurement of the brightness of sub-images according to yet another embodiment of the disclosure. The tester may first shield the optical system of the electronic device from projecting the second sub-image to capture the first sub-image, so as to obtain the first sub-captured image range  930  as shown in  FIG. 9A . Then, the tester may shield the optical system of the electronic device from projecting the first sub-image to capture the second sub-image, so as to obtain the second sub-captured image range  940  as shown in  FIG. 9A . The tester may perform brightness measurement at multiple equidistant measurement points on the first sub-captured image  931  in the first sub-captured image range  930  along the brightness measurement line SD 3  to obtain the brightness distribution result of the brightness  901 _ 1  to  901 _V as shown in  FIG. 9B , wherein V is a positive integer. The brightness measurement line SD 3  is perpendicular to the image stitching line X L3  and the image stitching line X R3 . The tester may perform brightness measurement at multiple equidistant measurement points on the second sub-captured image  941  in the second sub-captured image range  940  along the brightness measurement line SD 4  to obtain the brightness distribution result of the brightness  902 _ 1  to  902 _X as shown in  FIG. 9B , wherein X is a positive integer. The brightness measurement line SD 3  is perpendicular to the image stitching line X L4  and the image stitching line X R4 . It should be noted that the combined result of the first sub-captured image  931  and the second sub-captured image  941  is similar to the captured image  711  of  FIG. 7A . The position of the image stitching line X L3  in the image may correspondingly overlap the image stitching line X L4 , and the position of the image stitching line X R3  in the image may correspondingly overlap the image stitching line X R4 . 
     In this embodiment, according to the brightness distribution result of the brightness  901 _ 1  to  901 _V, the tester may prove that one side of the first sub-captured image  931  along the image stitching line X L3  has the first non-overlapping portion  931 _ 2  with uniform brightness of the brightness value B 2 . The first sub-captured image  931  has the first overlapping portion  931 _ 11  with uniform brightness of the brightness value Bm between the image stitching line X R3  and the reference position X 3 , and the first overlapping portion  931 _ 12  with uniform brightness of the brightness value BL between the image stitching line X L3  and the reference position X 3 . According to the brightness distribution result of the brightness  902 _ 1  to  902 _X, the tester may prove that one side of the second sub-captured image  941  along the image stitching line X R4  has the second non-overlapping portion  941 _ 2  with uniform brightness of the brightness value B 2 . The second overlapping portion  941 _ 11  with uniform brightness of the brightness value Bo is between the image stitching line X L4  and the reference position X 4 , and the second overlapping portion  941 _ 12  with uniform brightness of the brightness value Bn is between the image stitching line X R4  and the reference position X 4 . In other words, since each overlapping portion of the first sub-image and the second sub-image has a distribution of brightness in a stepped form, the tester may obtain that the brightness distribution result of the respective pattern overlapping portions in the first sub-image and the second sub-image may be a distribution of brightness in a stepped form that has a sharp change in brightness. It should be noted that the “distribution of brightness in a stepped form” mentioned in the disclosure may mean that the brightness difference between two adjacent points among multiple measurement points measured at equal intervals changes sharply. For example, in  FIG. 9B , the brightness value BL of the brightness  901 _W 2  changes to the brightness value Bm of the next brightness  901 _W 1 . 
     In this embodiment, the tester may select the brightness  901 _W 1  corresponding to one point of the first overlapping portion  931 _ 11  among the brightness  901 _ 1  to  901 _V between the reference position X 3  and the image stitching line X R3 , and the tester may select the brightness  901 _W 2  corresponding to one point of the first overlapping portion  931 _ 12  among the brightness  901 _ 1  to  901 _V between the reference position X 3  and the image stitching line X L3 , wherein W 1  and W 2  are positive integers. The tester may select the brightness  902 _Y 1  corresponding to one point of the second overlapping portion  941 _ 11  among the brightness  902 _ 1  to  902 _X between the reference position X 4  and the image stitching line X L4 , and the tester may select the brightness  902 _Y 2  corresponding to one point of the second overlapping portion  941 _ 12  among the brightness  902 _ 1  to  902 _X between the reference position X 4  and the image stitching line X R4 , wherein Y 1  and Y 2  are positive integers. The position of the reference position X 3  in the image may correspondingly overlap the reference position X 4 . Therefore, the tester may add the brightness value Bm of the brightness  901 _W 1  to the brightness value Bn of the brightness  902 _Y 2 , and may add the brightness value BL of the brightness  901 _W 2  to the brightness value Bo of the brightness  902 _Y 1 . If the sum of the brightness value Bm and the brightness value Bn is equal to the brightness value B 2  (the error is within plus or minus 10%), and the sum of the brightness value BL and the brightness value Bo is equal to the brightness value B 2  (the error is within plus or minus 10%), it means that the electronic device to be tested adopts the technique of the brightness distribution design of the sub-images in  FIG. 4  of the disclosure to achieve the display effect of providing an image with uniform brightness. 
     In addition, it should be noted that the above proof methods are not limited to proving the specific embodiments of the disclosure. In the process of proving the electronic device to be tested, the tester may preferably adopt any of the proof methods that can be clearly verified and meet the corresponding conditions. 
     In summary, the electronic device and the method for generating an image with uniform brightness according to the disclosure may display an image with a larger image area on the projection surface by splicing and projecting multiple sub-images, and with the special brightness distribution design for the overlapping portions of the multiple sub-images, the image generated by partially overlapping the multiple sub-images may have an image display effect of uniform brightness. 
     It should be noted that the above embodiments are used to illustrate, not to limit, the disclosure. Although the disclosure has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that it is possible to make modifications to the foregoing embodiments, or equivalently replace some or all of the technical features. These modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the disclosure.