Patent Publication Number: US-2021168339-A1

Title: Display apparatus, display method, and program

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The present application is a Bypass Continuation of PCT/JP2019/009403, filed on Mar. 8, 2019, which is based upon and claims the benefit of priority from Japanese Patent Application No. 2018-161283, filed on Aug. 30, 2018, the disclosure of which is incorporated herein in its entirety by reference. 
    
    
     BACKGROUND 
     The present disclosure relates to a display apparatus, a display method, and a program. 
     In recent years, image display technology using projectors has been developed. Further, there is a growing need to display images in various places, as represented by projection mapping which displays images on any objects such as buildings. 
     For example, Non-Patent Literature 1 (Development of Interlayer film to meet the demands to increase the amount of Information displayed on a vehicle windshield [Retrieved on Jul. 4, 2018], Internet &lt;URL: https://www.sekisui.co.jp/news/2015/1274415_23166.html&gt;) discloses the development of an interlayer film to meet the demands to increase the amount of information displayed on glass of an automobile. Further, Non-Patent Literature 2 (Xperia Touch (G1109) [Retrieved on Jul. 4, 2018], Internet &lt;URL: https://www.sony.jp/xperia-smart-products/products/G1109/&gt;) discloses a technique for projecting an image on various places in a focus-free manner. 
     SUMMARY 
     However, the technique disclosed in Non-Patent Literature 1 is specialized for performing display on glass, and the technique disclosed in Non-Patent Literature 2 is adapted only to a surface on which visible light is reflected. Meanwhile, in a daily environment, there are both a region in which visible light is transmitted and a region in which visible light is reflected. As described above, there has been a demand for a technique for unitarily and suitably displaying information for a region in which visible light is transmitted and a region in which visible light is reflected. 
     According to an embodiment, a display apparatus is a display apparatus configured to project an image onto a target projection surface having a first region in which a first wavelength light is reflected and a second region in which the first wavelength light is transmitted and in which visible light is emitted by receiving a second wavelength light that is different from the first wavelength light. The display apparatus includes: a wavelength selection unit configured to, based on region distribution information which is information about a distribution of the first and the second regions on the target projection surface, select the first wavelength light as light to be projected onto the first region and select the second wavelength light as light to be projected onto the second region; a light source unit configured to emit light selected from either the first wavelength light or the second wavelength light; and a projection unit configured to project the image formed by the emitted light onto the target projection surface. 
     According to an embodiment, a display method is a display method for projecting an image onto a target projection surface having a first region in which a first wavelength light is reflected and a second region in which the first wavelength light is transmitted and in which visible light is emitted by receiving a second wavelength light that is different from the first wavelength light. The display method includes: a wavelength selection step of, based on region distribution information which is information about a distribution of the first and the second regions on the target projection surface, selecting the first wavelength light as light to be projected onto the first region and selecting the second wavelength light as light to be projected onto the second region; an emission step of emitting light selected from either the first wavelength light or the second wavelength light; and a projection step of projecting the image formed by the emitted light onto the target projection surface. 
     According to the present embodiment, it is possible to provide a display apparatus capable of suitably displaying information within a viewing angle of a user. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of an automobile equipped with a display apparatus according to an embodiment; 
         FIG. 2  is a diagram showing a target projection region of the display apparatus according to an embodiment; 
         FIG. 3  is a cross-sectional view of a windshield according to a first embodiment; 
         FIG. 4  is a block diagram of a display apparatus according to the first embodiment; 
         FIG. 5  is a block diagram of a light source unit of the display apparatus according to the first embodiment; 
         FIG. 6  is a diagram showing region distribution information of the display apparatus according to the first embodiment; 
         FIG. 7  shows region distribution information including distortion adjustment information; 
         FIG. 8  is a diagram showing a projection range of the display apparatus according to the first embodiment as viewed from the top thereof; 
         FIG. 9  shows an example in which an image is projected by the display apparatus according to the first embodiment; 
         FIG. 10  is a diagram showing a projection range of a display apparatus according to a modified example 1 of the first embodiment as viewed from the top thereof; 
         FIG. 11  is a block diagram of a display apparatus according to a modified example 2 of the first embodiment; 
         FIG. 12  is a block diagram of a display apparatus according to a second embodiment; 
         FIG. 13  is a flowchart showing processing of the display apparatus according to the second embodiment; 
         FIG. 14  shows an example in which an image is projected by the display apparatus according to the second embodiment; and 
         FIG. 15  shows an example in which an image is projected by a display apparatus according to a third embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments according to the present disclosure will be described hereinafter with reference to the drawings. In order to clarify the explanation, the following descriptions and the drawings are partially omitted and simplified as appropriate. Note that throughout the drawings, the same components are denoted by the same reference signs and redundant descriptions are omitted as appropriate. 
     First Embodiment 
     A first embodiment will be described with reference to  FIG. 1 .  FIG. 1  is a top view of an automobile equipped with a display apparatus according to the embodiment. An automobile  900  shown in  FIG. 1  includes cameras  901  and a display apparatus  1 . The cameras  901  are a plurality of cameras, each of which shoots an image of the area outside the automobile  900 . As shown in  FIG. 1 , the automobile  900  includes a camera  901 R on the right door mirror thereof and a camera  901 L on the left door mirror thereof. The camera  901 R shoots an image of the area outside the right side of the automobile  900 , and the camera  901 L shoots an image of the area outside the left side of the automobile  900 . Specifically, the camera  901 R shoots the area in the direction to the right rear of the automobile  900  from the right side thereof and the camera  901 L shoots the area in the direction to the left rear of the automobile  900  from the left side thereof. Further, the cameras  901  may include a camera which is disposed so that it faces in the direction to the front of the automobile  900  in order to shoot the area in the direction to the front of the automobile  900 . Further, the cameras  901  may include a camera which is disposed so that it faces in the direction to the rear of the automobile  900  in order to shoot the area in the direction to the rear of the automobile  900 . 
     The display apparatus  1  is a laser projector that displays a predetermined image by projecting a laser light onto a target projection region set in a cabin of the automobile  900 . As shown in  FIG. 1 , the automobile  900  includes two display apparatuses (a display apparatus  1 A and a display apparatus  1 B). The display apparatuses  1 A and  1 B are fixed to a ceiling of the automobile  900  above the driver&#39;s seat, and are set so that the display apparatus  1 A projects an image onto a region of the cabin on the right front side thereof, and the display apparatus  1 B projects an image onto a region of the cabin on the left front side thereof. The display apparatus  1 A, for example, performs predetermined processing on an image of the area outside the right side of the automobile  900  shot by the camera  901 R and then projects this image toward the right front of the cabin. Similarly, the display apparatus  1 B, for example, performs predetermined processing on an image of the area outside the left side of the automobile  900  shot by the camera  901 L and then projects this image toward the left front of the cabin. 
     A target projection region in the cabin of the automobile  900  will be described with reference to  FIG. 2 .  FIG. 2  is a diagram showing the target projection region of the display apparatus according to the first embodiment. In a region assumed to be the visual field of the driver in the front side of the cabin of the automobile  900 , a target projection region F 91  is set on the right side of the cabin of the automobile  900  and a target projection region F 92  is set on the left side thereof so that it is adjacent to the projection region F 91 . 
     The target projection region F 91  is a region onto which the display apparatus  1 A projects an image. The target projection region F 91  includes a windshield  904 , a right A-pillar  905 , a side window  906 , a dashboard, a front right door trim, and the like. Further, the target projection region F 92  is a region onto which the display apparatus  1 B projects an image. The target projection region F 92  includes the windshield  904 , a left A-pillar  903 , a side window  902 , the dashboard, a front left door trim, and the like. That is, the target projection regions F 91  and F 92  include regions (the A-Pillars, the dashboard, and the like) in which visible light is not easily transmitted, and regions (the side windows and the windshield) in which visible light is easily transmitted. In the following description, the region in which visible light is not easily transmitted is referred to as a first region. Further, the region in which visible light is easily transmitted is referred to as a second region. The left end part of the projection region F 91  and the right end part of the projection region F 92  may partially overlap each other or a space may be provided therebetween. 
     The A-pillar  905 , the dashboard, and the like, which form the first region of the regions forming the target projection region, are regions in which visible light is not transmitted. The first region has a function of reflecting visible light without transmitting visible light. Thus, in the first region, visible light projected by the display apparatus  1  is reflected, whereby it is possible for a driver or the like to visually recognize the reflected visible light. The surface of the first region may be formed of a material including a retroreflective material so that visible light projected by the display apparatus  1  can be suitably reflected. 
     The side window  902 , the windshield  904 , and the side window  906 , which form the second region of the regions forming the target projection region, each have a function of transmitting visible light, and emitting light when it receives ultraviolet light having a predetermined wavelength. A material having such a function is, for example, laminated glass having a self-luminous intermediate film. 
     An overview of the principle of a self-luminous intermediate film will be described with reference to  FIG. 3 , which illustrates the windshield  904 .  FIG. 3  is a cross-sectional view of the windshield according to the first embodiment. The windshield  904  is composed of two glass plates  904 G and a self-luminous intermediate film  904 IM sandwiched between the two glass plates  904 G. Further, the self-luminous intermediate film  9041 M contains a luminescent material  904 A. The luminescent material  904 A has a property of emitting fluorescent light having a wavelength in a visible light range when it is excited by ultraviolet light having a specific wavelength and transmitting light other than the ultraviolet light. That is, the display apparatus  1  projects a predetermined ultraviolet light onto the windshield  904  having the above-described structure, whereby the self-luminous intermediate film  9041 M emits light. Thus, a driver or the like riding in the automobile  900  can visually recognize an image displayed on the windshield  904 . 
     Note that the side window  902 , the windshield  904 , and the side window  906  are not limited to being formed of the materials described above, and may instead each have any other structure having a function of transmitting visible light and emitting light when it receives ultraviolet light having a predetermined wavelength. For example, the side window  902 , the windshield  904 , and the side window  906  may be formed of a combination of a resin such as acrylic, which transmits visible light, and a luminescent material. Further, in addition to the structure described above, the side window  902 , the windshield  904 , and the side window  906  may have UV-cut layers having a property of cutting ultraviolet light on an outer surface side of the automobile. By this structure, it is possible to prevent ultraviolet light projected by the display apparatus  1  from leaking to the outside and prevent the entire surface of each of the side window  902 , the windshield  904 , and the side window  906  from being fluoresced by ultraviolet light contained in sunlight and hence obstructing the visual field of the driver. 
     As described above, the target projection regions F 91  and F 92  have the first region in which visible light is reflected and the second region in which visible light is transmitted and fluorescence light having the wavelength range of visible light is emitted by receiving ultraviolet light. 
     Next, the configuration of the display apparatus  1  will be described with reference to  FIG. 4 .  FIG. 4  is a block diagram of the display apparatus according to the first embodiment. The display apparatus  1  includes, as its main components, a control unit  10 , a laser light source unit  20 , a scanner unit  30 , and a memory  40 . 
     The control unit  10  is connected to the camera  901 , the laser light source unit  20 , the scanner unit  30 , and the memory  40 , and thereby controls the operation of the display apparatus  1 . The control unit  10  is composed of, for example, a Central Processing Unit (CPU), a Graphics Processing Unit (GPU), or a combination of other electric circuits. Therefore, for example, the control unit  10  may be referred to as a control circuit. The control unit  10  includes, as its main components, an image data acquisition unit  11 , an image processing unit  13 , an object recognition unit  12 , a laser light source control unit  14 , and a scanner control unit  15 . 
     The image data acquisition unit  11  receives image data, which is data of an image of the area outside the automobile  900  shot by the camera  901 , via a predetermined interface. 
     The object recognition unit  12  recognizes an object, which is a target to be recognized from the image data acquired by the image data acquisition unit  11 . In order to perform recognition processing, the object recognition unit  12 , for example, extracts a feature value from luminance data of the image data, and checks whether the extracted feature value coincides with a feature value dictionary stored in the memory  40 . Further, when the object recognition unit  12  detects the object to be recognized, it temporarily holds information about the recognized object, such as the position, the size, and the type thereof. Alternatively, the object recognition unit  12  supplies information about the recognized object, such as the position, the size, and the type thereof, to the image processing unit  13 . 
     The image processing unit  13  performs, based on the image data acquired by the image data acquisition unit  11  and the information about the object received from the object recognition unit  12 , predetermined processing on the image data. An example of the predetermined processing is processing for extracting image data of the target object recognized by the object recognition unit  12  and generating projection image data for projecting the extracted image data onto the target projection regions F 91  and F 92 . Note that the projection image data is image data of an image projected by the display apparatus  1 . Another example of the predetermined processing is processing for, on image data, superimposing a frame around the recognized target object, or superimposing an icon or character information for displaying a type of the recognized object, such as whether the recognized object is a pedestrian or a bicycle. When the above processing is performed, the image processing unit  13  reads image data stored in advance in the memory  40  and superimposes the read image data on the image data. 
     Further, the image processing unit  13  includes a distortion adjustment unit  131 . The distortion adjustment unit  131  performs distortion adjustment processing suitable for a target projection surface on the image data. The distortion adjustment processing includes linear correction such as trapezoidal correction, and nonlinear correction. By performing this processing, the display apparatus  1  can project an image having little distortion onto a projection surface. Note that how the distortion adjustment method, which is a method for adjusting image data, is executed is determined by a position where the display apparatus  1  is disposed and a shape of the target projection region, and the specific processing is executed, for example, by using a conversion formula stored in advance in the memory  40 . The image processing unit  13  performs the above-described processing, thereby generating projection image data. 
     The laser light source control unit  14  outputs a laser drive signal based on the projection image data to a laser driver  22 , thereby controlling the output of a laser diode. By doing so, the laser light source control unit  14  controls the output of light from the laser light source unit  20 . Specifically, the laser light source control unit  14  controls driving of red, blue, and green laser diodes  211 R,  211 B, and  211 G, respectively, and an ultraviolet laser diode  211 UV in accordance with the color and the brightness of each pixel included in the projection image data processed by the image processing unit  13 . Further, the laser light source control unit  14  performs Auto Power Control (APC) processing. In the APC processing, the laser light source control unit  14  evaluates the state of the laser light source unit  20  based on the intensity of the laser light detected by a photodiode  23 , determines the driving current values of the laser diodes  211 , and controls the laser driver  22 . 
     Further, the laser light source control unit  14  operates in synchronization with the scanner control unit  15 . More specifically, the laser light source control unit  14 , for example, shares a horizontal synchronization signal for synchronization in the horizontal direction and a vertical synchronization signal for synchronization in the vertical direction with the scanner control unit  15 , and determines the output of each laser based on these signals. As described above, the laser light source control unit  14  and the scanner control unit  15  operate in synchronization with each other, whereby the display apparatus  1  controls the color and the output of each pixel that constitutes the projection image data. Thus, the display apparatus  1  can generate a desired image. 
     Further, the laser light source control unit  14  includes a wavelength selection unit  141 . The wavelength selection unit  141  has a function of selecting, for the first region, visible light corresponding to the first region as a first wavelength light, and selecting, for the second region, ultraviolet light corresponding to the second region as a second wavelength light based on region distribution information which is information about a distribution of the first and the second regions on the target projection surface. Note that details of the region distribution information will be described later. 
     The wavelength selection unit  141  performs, for example, processing for setting an output of visible light or ultraviolet light for each pixel of an image projected by the display apparatus  1 . The laser light source control unit  14  switches the output of visible light or ultraviolet light by outputting the laser light set by the wavelength selection unit  141  based on the horizontal and the vertical synchronization signals. By this configuration, the display apparatus  1  drives a visible light laser when it projects pixels included in the first region, while the display apparatus  1  drives an ultraviolet laser when it projects pixels included in the second region. Thus, by switching laser lights based on preset region distribution information, it is possible to efficiently perform a wavelength switching operation. 
     Note that the wavelength selection unit  141  may include region distribution information as a rewritable register. By making the region distribution information rewritable, it is possible to easily cope with a change in the region distribution information of the target projection region. 
     The scanner control unit  15  outputs a scanner drive signal to a scanner driver  32  and controls scanning of a laser light performed by a scanner  31 . The scanner control unit  15  operates based on the above-described horizontal and vertical synchronization signals. Further, the scanner control unit  15  monitors a detection signal of a scan angle detection unit (not shown) that detects a scan angle of the scanner  31  and performs, for example, control of the scan angle, the waveform generation, and the oscillation frequency of the scanner  31 . 
     The laser light source unit  20  includes a laser module  21  that outputs a laser light, the laser driver  22  that drives laser diodes included in the laser module  21 , the photodiode  23  that measures the amount of laser light, and the like. 
     Details of the laser light source unit  20  will be described with reference to  FIG. 5 .  FIG. 5  is a block diagram of the light source unit of the display apparatus according to the first embodiment. As shown in  FIG. 5 , the laser module  21  includes the red laser diode  211 R, the green laser diode  211 G, the blue laser diode  211 B, the ultraviolet laser diode  211 UV, and dichroic mirrors  212 R,  212 G,  212 B, and  212 UV corresponding to the laser diodes  211 R,  211 B,  211 G, and  211 UV, respectively. The laser lights of the respective colors output from the laser diodes  211  are multiplexed by the dichroic mirrors  212 , and then output to the scanner unit  30 . 
     The dichroic mirror  212 R has a characteristic of reflecting approximately 100% of the light having a red wavelength output from the red laser diode  211 R. The dichroic mirror  212 G has a characteristic of transmitting approximately 100% of the light having a red wavelength output from the red laser diode  211 R and reflecting approximately 100% of the light having a green wavelength output from the green laser diode  211 G. Examples of characteristics of the dichroic mirror  212 B include a characteristic of reflecting about 98% of the light having a red wavelength output from the red laser diode  211 R and about 98% of the light having a green wavelength output from the green laser diode  211 G, and transmitting about 2% of each of these lights. Further, the examples of characteristics of the dichroic mirror  212 B includes a characteristic of transmitting about 98% of the light having a blue wavelength output from the blue laser diode  211 B and reflecting about 2% of this light. The dichroic mirror  212 UV has a characteristic of transmitting approximately 100% of the lights having a red wavelength and a green wavelength reflected by the dichroic mirror  212 B and approximately 100% of the light having a blue wavelength transmitted through the dichroic mirror  212 B, and reflecting approximately 100% of the ultraviolet light output from the ultraviolet laser diode  211 UV. 
     By this configuration of the dichroic mirror  212 , about 98% of each of the visible lights (the laser light having a red wavelength, the laser light having a green wavelength, and the laser light having a blue wavelength) output from the laser diodes  211  is made incident on the scanner unit  30 , and about 2% of each of the visible lights is made incident on the photodiode  23 . Further, about 100% of the ultraviolet light output from the laser diode  211  is made incident on the scanner unit  30 . The laser driver  22  drives the laser diodes  211  based on a laser drive signal from the control unit  10 . The photodiode  23  measures the amount of incident laser light and outputs a result of the measurement to the control unit  10 . Note that the configurations of the laser diodes  211  and the dichroic mirrors  212  are not limited to those shown in  FIG. 5 , and any configuration can be adopted as long as the respective outputs from these diodes and mirrors to the scanner unit  30  and the photodiode  23  are performed in a manner similar to those performed by the laser diodes  211  and the dichroic mirrors  212  according to the configurations shown in  FIG. 5 . 
     Referring back to  FIG. 4 , the description will be continued. The scanner unit  30  projects a laser light made incident from the laser light source unit  20  as an image onto the target projection region. The scanner unit  30  can also be referred to as a projection unit. The scanner unit  30  includes, as its main components, the scanner  31 , which is a scanning mirror unit that reflects the laser light output from the laser light source unit  20  and scans it, the scanner driver  32  that drives the scanner  31 , a scan angle detection unit (not shown) that detects a scan angle of the scanner  31 , and the like. The scanner  31  includes a vertical mirror  311  that reflects a laser light and scans it in a vertical direction, a horizontal mirror  312  that reflects a laser light and scans it in a horizontal direction, and the like. The vertical mirror  311  and the horizontal mirror  312  are configured by a micro electro mechanical system (MEMS) mirror and the like. 
     The scanner driver  32  drives the scanner  31  based on a scanner drive signal from the scanner control unit  15 . When the scanner  31  is configured by the vertical mirror  311  and the horizontal mirror  312 , in general, the vertical mirror  311  operates at a scan angle and an oscillation frequency controlled by the scanner driver  32 , and the horizontal mirror  312  operates at a scan angle and a oscillation frequency due to resonance since the oscillation frequency is high. Note that the horizontal mirror  312 , like the vertical mirror  311 , may operate at the scan angle and the oscillation frequency controlled by the scanner driver  32 . 
     The memory  40  is a non-volatile storage device. The memory  40  is connected to the control unit  10 . The control unit  10  can write any data into the memory  40  or read any data stored in the memory  40 . Further, the memory  40  stores a recognition dictionary. 
     Next, region distribution information will be described with reference to  FIGS. 6 and 7 .  FIG. 6  is a diagram showing region distribution information of the display apparatus according to the first embodiment. A rectangular figure on the right side of  FIG. 6  schematically shows region distribution information R 91   a  of the display apparatus  1 A. 
     The region distribution information R 91   a  is formed so that the projection region of the display apparatus  1 A corresponds to the target projection region F 91  shown in  FIG. 2 . That is, in the region distribution information R 91   a , a region corresponding to the windshield  904  included in the target projection region F 91  is a region R 914 . Similarly, in the region distribution information R 91   a , the A-pillar  905  and the like correspond to a region R 915 , and the side window  906  corresponds to a region R 916 . That is, the region R 915  is the first region in which visible light is reflected, and hatching of the same type as that of the first region shown in  FIG. 4  is applied thereto. Further, the regions R 914  and R 916  are the second regions which emit light in response to ultraviolet light, and hatching of the same type as that of the second region shown in  FIG. 4 . 
     The region distribution information R 91   a  corresponds to a position of each pixel of image data. For example, in the region distribution information R 91   a , a region corresponding to each pixel is defined for each position of each of the pixels in a horizontal direction H and a vertical direction V using the upper left of the rectangle as the origin. For example, an address of any pixel of an image in the horizontal direction and an address of any pixel of an image in the vertical directions are defined as Hn and Vn, respectively, the image being projected by the display apparatus  1 A. In this case, the region distribution information R 91   a  shown in  FIG. 6  indicates whether the pixel of the address (Hn, Vn) is the first region or the second region. 
     A rectangular figure on the left side of  FIG. 6  schematically shows region distribution information R 92   a  of the display apparatus  1 B. The region distribution information R 92   a  is formed on a principle similar to that of the above-described region distribution information R 91   a . That is, the region distribution information R 92   a  includes a region R 923  as the first region, and a region R 922  and a region R 924  as the second regions. However, the region distribution information R 92   a  differs from the region distribution information R 91   a  described above in that the region distribution information R 92   a  includes a region R 921 . The region R 921  is a region of a rearview mirror disposed in the windshield  904 . That is, the display apparatus  1  is configured so that it does not project an image onto the region of the rearview mirror. Therefore, the region R 921  is formed so that a laser light is not projected thereonto. As described above, in region distribution information, a region onto which light is not projected may be set in advance. 
     Next, region distribution information will be further described with reference to  FIG. 7 .  FIG. 7  shows region distribution information including distortion adjustment information. A rectangular figure on the right side of  FIG. 7  schematically shows region distribution information R 91  of the display apparatus  1 A. 
     As shown in the figure, unlike the region distribution information R 91   a  shown in  FIG. 6 , the first and the second regions have a bent band shape in which the shape of the outer edge gently increases from the left end thereof toward the right thereof and gently descends toward the right end thereof using the region R 915  as the vertex. Further, the rectangular region distribution information R 91  includes blank regions R 910 , each of which is not hatched so as to correspond to its shape, in the upper right, the upper left, and the lower center thereof, respectively. 
     The blank region R 910  is a region onto which a laser light is not projected. This shape of the projection region is due to the relative positional relation between the position where the display apparatus  1 A is disposed and the target projection region F 91 . That is, the region distribution information R 91  includes information about distortion adjustment corresponding to the target projection region F 91 . 
     A rectangular figure on the left side of  FIG. 7  schematically shows region distribution information R 92  of the display apparatus  1 B. As shown in in the figure, in the distribution information R 92 , unlike the region distribution information R 92   a  shown in  FIG. 6 , the first and the second regions have a bent band shape in which the shape of the outer edge gently increases from the left end thereof toward the right thereof and gently descends toward the right end thereof using the region R 923  as the vertex. Further, the rectangular region distribution information R 92  includes blank regions R 920 , each of which is not hatched so as to correspond to its shape, in the upper right, the upper left, and the lower center thereof, respectively. The region distribution information R 92  is formed on a principle similar to that of the above-described region distribution information R 91 . That is, the region distribution information R 92  includes distortion adjustment information in addition to the region distribution information R 91   a  shown in  FIG. 6 . 
     The wavelength selection unit  141  supplies a switching signal of laser lights to the laser light source unit  20  based on the region distribution information configured as described above. By doing so, the display apparatus  1  can efficiently project a suitable image in which distortion is reduced onto the target projection region F 91 . Note that a technique of adjusting distortion by making image data projected by a projector correspond to the distance to the target projection region is known to a person skilled in the art, and therefore a detailed description thereof will be omitted here. 
     Next, a relation between a projection range of the display apparatus and the visual field of a user will be described with reference to  FIG. 8 .  FIG. 8  is a diagram showing the projection range of the display apparatus according to the first embodiment as viewed from the top thereof. As shown in  FIG. 8 , the target projection region F 91  includes the windshield  904 , the A-pillar  905 , and the side window  906 . The target projection region F 92  includes the windshield  904 , the A-pillar  903 , and the side window  902 . 
     As shown in  FIG. 8 , the display apparatuses  1 A and  1 B are disposed above and behind the driver so that they perform projection in directions different from each other. The display apparatus  1 A is disposed above and behind the driver on the left side and performs projection to the right front side of the driver. The display apparatus  1 A has a projection angle A 91 . That is, the display apparatus  1 A is disposed so that the target projection region F 91  is included in a range of the projection angle A 91 . Similarly, the display apparatus  1 B has a projection angle A 92 . The display apparatus  1 B is disposed so that the target projection region F 92  is included in a range of the projection angle A 92 . As shown in  FIG. 8 , the target projection regions F 91  and F 92  are adjacent to each other. Further, a region obtained by combining the target projection regions F 91  and F 92  substantially coincides with a visual field A 90  of the driver. 
     In this way, by disposing the display apparatus  1  above and behind the driver, it is possible to increase the projection region of the display apparatus  1 , and accordingly, it is possible to increase the target projection region. Further, by disposing the display apparatus  1  in the above-described manner, the display apparatus  1  can display an image over the entire range of the visual field of the driver. Therefore, the display apparatus  1  can perform display with a high degree of freedom. Further, by disposing the display apparatus  1  above the driver and at a position corresponding to the position of the driver&#39;s eye, the display apparatus  1  can easily display an image close to an image viewed from the viewpoint of the driver. Note that in a state where a plurality of display apparatuses  1  are disposed and their projection ranges are made adjacent to each other, by tiling images to be projected by the plurality of display apparatuses  1 , the display apparatus  1  can suitably display a wide-angle image. 
     Note that as shown in  FIG. 8 , when display is performed over the entire range of the visual field of the driver in the cabin of the automobile  900 , the distance from the display apparatus  1  to the target projection region greatly varies. For example, a distance D 1  from the display apparatus  1 A to the right end of the target projection region F 91  that corresponds to the display apparatus  1 A is not more than half a distance D 2  from the display apparatus  1 A to the left end of the target projection region F 91  that corresponds to the display apparatus  1 A. When the distances (the projection distances) from the display apparatus to the target projection region widely differ from each other as described above, a focus-free laser projector that displays images by sequentially scanning coherent lights can be suitably used. 
     Next, an example of display performed by the display apparatus  1  will be described with reference to  FIG. 9 .  FIG. 9  shows an example in which an image is projected by the display apparatus according to the first embodiment.  FIG. 9  shows scenery that a driver of the automobile  900  is looking at. In the following description of this embodiment, such scenery that the driver is looking at is also referred to as scenery viewed from a viewpoint of the driver. As shown in  FIG. 9 , a bicycle  801  is traveling to the left front of the automobile  900 . Further, in the traveling direction of the automobile  900 , there is a pedestrian  802 . Further, to the right front of the automobile  900 , another automobile  803  is traveling on a side road. Further, the display apparatus  1  can recognize the aforementioned objects from image data of images shot by the cameras  901  disposed outside the automobile  900 . In the above situation, a display example in which display performed by the display apparatus  1  differs for each object will be described. 
     First, a first display example is described using the other automobile  803 . The display apparatus  1  displays, based on the images shot by the cameras  901 , the other automobile  803  that is hidden from view due to the right A-pillar. Here, the other automobile  803  can be visually recognized through the windshield  904 , over the A-pillar  905 , and through the side window  906 . In such a case, the display apparatus  1  does not display the other automobile  803  on the second region that can be directly, visually recognized through the glass, but can only display it on the first region corresponding to the A-pillar  905  which is a blind spot of the driver. By performing such display, the display apparatus  1  can suitably display an object located in the blind spot. Further, the display apparatus  1  displays the other automobile  803  so that a displayed image is superimposed on the scenery viewed from the viewpoint of the driver without giving a feeling that something is wrong. That is, the display apparatus  1  performs distortion adjustment so that the image of the other automobile  803  projected onto the A-pillar  905  becomes the image viewed from the viewpoint of the driver. Then, the display apparatus  1  displays the image of the other automobile  803  on the A-pillar  905  so that it does not deviate from the other automobile  803  visually recognized by the driver with the naked eye through the windshield  904  and the side window  906 . By doing the above, the driver can intuitively recognize the position and the size of the object. 
     Next, a second display example will be described using the pedestrian  802 . The display apparatus  1  recognizes the pedestrian  802  present in front of the automobile  900  based on the images shot by the cameras. In order for the driver to recognize the presence of the pedestrian  802 , the display apparatus  1  performs display in which the area around the pedestrian  802  is surrounded by a polygonal frame such as a rectangle. In this case, the display apparatus  1  displays a rectangle by projecting ultraviolet light onto the second region. Note that when the pedestrian  802  is present at the same position as that of the first region, the display apparatus  1  performs display by projecting visible light onto the first region. As described above, the display apparatus  1  can perform the above display in order for the driver to recognize the recognized object within the range of the visual field of the driver regardless of whether the recognized object is in the first region or the second region. Therefore, the display apparatus  1  can perform display for making the driver recognize the object so that he/she can intuitively recognize it. Note that the display in which the area around the object is surrounded by a frame in order to make the driver recognize the object is, as a matter of course, merely one example of a method for making the driver recognize the object, and the display apparatus  1  can employ various methods for achieving the same using images, characters, and the like. 
     Next, a third display example will be described using the bicycle  801 . The display apparatus  1  recognizes the bicycle  801  traveling to the left front of the automobile  900  based on the images shot by the cameras. Further, the display apparatus  1  displays the bicycle  801  so that it can be visually recognized through the side window  902 , over the A-pillar  903 , through the windshield  904 , and the like. In this case, since the bicycle  801  is located behind the A-pillar  903  and the left side mirror, most of the bicycle  801  cannot be visually recognized with the naked eye from the visual field of the driver. In such a situation, the display apparatus  1  can display, on the side window  902 , the bicycle  801  located behind the left side mirror. Note that, here, like in the first display example, the display apparatus  1  displays the bicycle  801  as an image viewed from the viewpoint of the driver. 
     Note that the display apparatus  1  can extract image data of the object recognized by the object recognition unit  12 , and properly display the extracted projection image data related to the object in accordance with the display examples described above. That is, the display apparatus  1  can extract a part of the image data generated by the camera  901  and display the extracted image, instead of using all of the image data generated by the camera  901  as a projection image. Thus, the display apparatus  1  can efficiently perform desired display while preventing the display from being complicated. 
     Modified Example 1 of First Embodiment 
     Next, a modified example 1 of the first embodiment will be described with reference to  FIG. 10 .  FIG. 10  is a diagram showing a projection range of a display apparatus according to a modified example 1 of the first embodiment as viewed from the top thereof. The projection range of the display apparatus  1  according to this modified example differs from that of the first embodiment. 
     As shown in  FIG. 10 , the automobile  900  includes a display apparatus  1 C and a display apparatus  1 D behind the driver. The display apparatuses  1 C and  1 D, respectively, have the same configurations as those of the display apparatuses  1 A and  1 B, but the projection angles are narrower than those of the respective display apparatuses  1 A and  1 B. That is, the display apparatus  1 C has a projection angle A 93 , and accordingly corresponds to a target projection region F 93 . The display apparatus  1 D has a projection angle A 95 , and accordingly corresponds to a target projection region F 95 . Further, the target projection region F 93  is not adjacent to the target projection region F 95 . Further, a target projection region F 94  in which a head-up display apparatus HUD performs display is provided between the target projection regions F 93  and F 95 . Here, the target projection regions F 93  and F 94  are adjacent to each other, and the target projection regions F 94  and F 95  are adjacent to each other. That is, in the modified example of first embodiment, the target projection regions F 93 , F 94 , and F 95  are connected to each other, thereby covering the visual field A 90  of the driver. By such a configuration, the display apparatuses  1 C and  1 D can perform display with a high degree of freedom with regard to the visual field of the driver by cooperating with the head-up display apparatus HUD. 
     Further, the display apparatus  1  according to this modified example can cooperate with the head-up display apparatus HUD, to thereby perform display using a change in a feeling of depth with regard to the driver. That is, when a real image is provided to the driver, the display apparatus  1 C or  1 D projects ultraviolet light onto the windshield  904 . Further, when a virtual image having a feeling of depth is provided to the driver, the head-up display apparatus HUD displays the image. By this configuration, the display apparatus  1  can perform display with a high degree of freedom. Note that in the modified example of the first embodiment, the target projection regions F 93  and F 94  or the target projection regions F 94  and F 95  may overlap each other. 
     Modified Example 2 of First Embodiment 
     Next, a modified example 2 of the first embodiment will be described with reference to  FIG. 11 . This modified example differs from the above-described first embodiment in that region distribution information is stored in the memory. Further, this modified example differs from the above-described first embodiment in that the wavelength selection unit  141  operates based on the region distribution information stored in the memory  40 . 
       FIG. 11  is a block diagram of the display apparatus according to the modified example 2 of first embodiment. The differences between the display apparatus according to this modified example and that of the first embodiment will be described below. The wavelength selection unit  141  is implemented by, for example, a register set based on region distribution information stored in the memory  40 . When the laser light source control unit  14  controls a laser light in synchronization with the scanner control unit  15 , the laser light source control unit  14  selects a wavelength of the laser based on the setting of the wavelength selection unit  141 . By this configuration, the display apparatus  1  drives a visible light laser when it projects pixels included in the first region, while the display apparatus  1  drives an ultraviolet laser when it projects pixels included in the second region. Thus, by switching laser lights based on preset region distribution information, it is possible to efficiently perform a wavelength switching operation. 
     The memory  40  according to this modified example stores region distribution information. The memory  40  is a rewritable non-volatile storage device such as an Erasable Programmable Read Only Memory (EPROM), a flash memory, or a Ferroelectric Random Access Memory (FeRAM). Further, the region distribution information stored in the memory  40  can be rewritten by a user. By the above configuration, the display apparatus according to the modified example 2 of the first embodiment can easily update region distribution information and suitably display information within the viewing angle of the driver. 
     The first embodiment has been described above. However, the configurations of the display apparatus  1  are not limited to those described above. For example, instead of a MEMS mirror, the scanner unit may be a reflective liquid crystal panel or a Digital Light Processing (DLP) type projector. In this case, for example, the display apparatus  1  may include a reflective panel for each wavelength of light to be projected and may be configured to composite images generated for each wavelength of light and project the composited images to the outside. Further, the display apparatus  1  may output, to a reflective panel that reflects a plurality of lights of wavelengths different from each other, lights of different wavelengths in a time-division manner. Note that, as a matter of course, visible light projected to the first region may be of any one color or two or more colors. 
     Further, the display apparatus  1  may display not only an image viewed from the viewpoint of the driver but also an image viewed from the viewpoint of a passenger other than the driver. In this case, the display apparatus  1  may change the image to be displayed to an image viewed from the viewpoint of any passenger who is seated. 
     By the above configuration, according to the first embodiment, it is possible to provide a display apparatus capable of suitably displaying information within the viewing angle of the driver or the like based on region distribution information. 
     Second Embodiment 
     Next, a second embodiment will be described with reference to  FIG. 12 .  FIG. 12  is a block diagram of a display apparatus according to the second embodiment. A display apparatus  2  according to the second embodiment differs from the first embodiment described above in that the object recognition unit  12  includes a warning determination unit  121  and that the wavelength selection unit is included in the image processing unit  13  in place of the laser light source control unit  14 . 
     The object recognition unit  12  includes the warning determination unit  121 . More specifically, the warning determination unit  121  determines whether or not an object recognized by the object recognition unit  12  may come into contact with the automobile  900 , and when it determines that the object recognized by the object recognition unit  12  may come into contact with the automobile  900 , the warning determination unit  121  determines to display a warning for this object. 
     The image processing unit  13  includes a wavelength selection unit  132 . The wavelength selection unit  132  performs conversion processing of the color and the output of the image to be projected based on region distribution information. For example, in image data, position information of a pixel is defined by the H (horizontal) and V (vertical) address. Further, information about the color in a predetermined pixel of the image data is defined for each of R (red), G (green), and B (blue) in 256 stages from 0 to 255. The wavelength selection unit  132  converts, based on a preset condition, the pixel information defined as described above so that it is defined by R, G, B, and UV (ultraviolet light) and their respective output values. 
     For example, the wavelength selection unit  132  first checks the position information of the pixel (hereinafter referred to as a target pixel) to be processed against the region distribution information stored in the memory  40  and determines whether the target pixel is included in the first region or the second region. When the wavelength selection unit  132  determines that the target pixel is included in the first region, it maintains the information about the color and the output of the target pixel. On the other hand, when the wavelength selection unit  132  determines that the target pixel is included in the second region, it converts the information about the color and the output of the target pixel based on a preset method. More specifically, for example, the wavelength selection unit  132  calculates an average of the output values of R, G, and B, and uses the calculated output value as an output value of ultraviolet light. Note that when the output value of UV is determined, it may be based on the maximum output values of R, G and B, or may be based on a quantified value obtained by quantifying the visibility of each color. 
     Next, processing performed by the display apparatus  2  according to the second embodiment will be described with reference to  FIG. 13 .  FIG. 13  is a flowchart showing processing of the display apparatus according to the second embodiment. The flowchart shown in  FIG. 13  shows processing performed by the object recognition unit  12  in the processing performed by the control unit  10  of the display apparatus  2 . 
     First, the object recognition unit  12  receives image data from the image data acquisition unit  11  (Step S 11 ). When the object recognition unit  12  receives the image data, it recognizes a target object by referring to the feature value dictionary, and determines whether or not the target object is in the image data (Step S 12 ). If the object recognition unit  12  cannot recognize the target object in the image data (No in Step S 12 ), the process returns to Step S 11 , where the object recognition unit  12  acquires the next image. On the other hand, if the object recognition unit  12  recognizes the target object in the image data (Yes in Step S 12 ), the warning determination unit  121  of the object recognition unit  12  determines whether or not the recognized object is an object to be warned (Step S 13 ). 
     An example of a method for determining whether or not the recognized object is an object to be warned is given below. The object recognition unit  12  sequentially receives image data shot by the camera  901  via the image data acquisition unit  11 , and sequentially performs processing for recognizing an object on the received image data. Therefore, the object recognition unit  12  can estimate a moving direction and a moving speed of the object from the image data pieces acquired at a plurality of times different from each other. Further, the object recognition unit  12  can estimate that the recognized object is approaching the automobile  900  and estimate that the approaching object may come into contact with the automobile  900  based on a preset threshold value. Therefore, when the approaching object may come into contact with the automobile  900 , the object recognition unit  12  determines the recognized object to be an object to be warned. Further, an object traveling in the vicinity of the automobile  900  may be determined to be an object to be warned based on the position and the moving direction of the recognized object. 
     Note that when the automobile  900  includes a distance measuring sensor such as Light Detection and Ranging (LiDAR), the display apparatus  2  may acquire a signal from the distance measuring sensor in addition to the image data to be acquired from the camera  901  and estimate that the automobile  900  may come into contact with the object by using the acquired signal. Further, when the camera  901  is a stereo camera, it may be estimated that the automobile  900  may come into contact with the object based on a plurality of image data pieces acquired from the cameras  901  at the same time. 
     If the warning determination unit  121  does not determine that the recognized object may come into contact with the automobile  900  (No in Step S 13 ), it does not determine to display a warning, and the process proceeds to Step S 15 . On the other hand, if the warning determination unit  121  determines that the recognized object may come into contact with the automobile  900  (Yes in Step S 13 ), it determines to display a warning (Step S 14 ). In this case, the warning determination unit  121  supplies information about the object for which a warning is to be displayed to the image processing unit  13 . Further, the processing performed in Step S 13  may be processing for determining whether or not the object recognized in Step S 12  is an object to be warned. For example, even if there is no possibility of the recognized object coming into contact with the automobile  900 , the recognized object may be determined to be an object to be warned when it is traveling in the vicinity of the automobile  900 . 
     In Step S 14 , if the warning determination unit  121  determines to display a warning, the image processing unit  13  performs predetermined processing for displaying a warning on the image data of the object for which a warning is to be displayed. Note that a specific example of this predetermined processing will be described later. 
     After Step S 14 , the object recognition unit  12  determines whether or not all of the processing is completed (Step S 15 ). If the object recognition unit  12  does not determine that all of the processing is completed (No in Step S 15 ), the process returns to Step S 11 , where the object recognition unit  12  acquires image data again. On the other hand, if the object recognition unit  12  determines that all of the processing is completed (Yes in Step S 15 ), it ends the processing. 
     Next, a specific example in which a warning is displayed will be described with reference to  FIG. 14 .  FIG. 14  shows an example in which an image is projected by the display apparatus according to the second embodiment. As shown in  FIG. 14 , display apparatuses  2 A and  2 B are disposed in the cabin of the automobile  900 . The display apparatus  2 A is configured to project an image toward the right front of the cabin. Further, the display apparatus  2 B is configured to project an image toward the left front of the cabin. Further, in  FIG. 14 , the bicycle  801  traveling to the left front of the automobile  900  is in a situation in which the bicycle  801  is traveling in the vicinity of the automobile  900  or in which it may come into contact with the automobile  900 . Further, although the other automobile  803  is in the right front of the automobile  900 , the possibility of it coming into contact with the automobile  900  is low at the point of time when this image is displayed, that is, the other automobile  803  is not an object to be warned. 
     In such a situation, the display apparatus  2 A displays an image of the other automobile  803  shot by the camera  901 . Here, the display apparatus  2 A determines that the other automobile  803  is not the object to be warned. Therefore, the display apparatus  2 A displays the other automobile  803  without displaying a warning. Meanwhile, the display apparatus  2 B displays an image of the bicycle  801  shot by the camera  901  while displaying a warning. Displaying a warning is to display a line image obtained by extracting the contour of the object to be warned. 
     The warning determination unit  121  of the display apparatus  2 B determines, from the image data acquired from the camera  901 , that the bicycle  801  is the object to be warned. Therefore, the warning determination unit  121  supplies, to the image processing unit  13 , information about the display of a warning. The image processing unit  13  generates, based on the information received from the warning determination unit  121 , a line image obtained by extracting the contour of the bicycle  801 , and superimposes the generated line image on the bicycle  801  and displays it. By performing such display, it is possible for the driver to intuitively recognize the presence of an object or the like which may come into contact with his/her automobile. 
     The second embodiment has been described above. However, a method for displaying a warning is not limited to the above-described method, and various methods for displaying a warning can be employed. For example, a warning may be displayed by blinking the display of the above-described line image obtained by extracting the contour of the object or changing the thickness of the line. Further, a warning may be displayed by changing a display mode in accordance with the moving speed of the object to be warned. Further, the warning determination unit  121  may determine a degree of risk to the automobile  900  in a plurality of stages, and change the display mode in accordance with the degrees of risk determined in the plurality of stages. Further, the display apparatus  2  may be configured to generate, when it displays a warning, a sound from a speaker in response to the warning. 
     As described above, according to the second embodiment, it is possible to provide a display apparatus capable of suitably displaying information within the viewing angle of the driver or the like based on region distribution information. 
     Third Embodiment 
     Next, a third embodiment will be described with reference to  FIG. 15 . A display apparatus according to the third embodiment differs from the display apparatus according to the second embodiment in that an image to be projected onto the target projection region is generated based on region distribution information and then the generated image is displayed.  FIG. 15  shows an example in which an image is projected by the display apparatus according to the third embodiment. 
     As shown in  FIG. 15 , display apparatuses  3 A and  3 B are disposed in the cabin of the automobile  900 . The display apparatus  3 A is configured to project an image toward the right front of the cabin. Further, the display apparatus  3 B is configured to project an image toward the left front of the cabin. Further, in  FIG. 15 , the bicycle  801  traveling on the left side of the automobile  900  is in a situation in which it is traveling at a position such as a blind spot where it is difficult for the driver of the automobile  900  to check visually or through a mirror. 
     In such a situation, the display apparatus  3 B displays a pseudo bicycle  801 V in the region where the bicycle  801  is to travel based on the image of the bicycle  801  shot by the camera. The bicycle  801 V is an image displayed at a position where the bicycle  801  is assumed to be located when a predetermined period of time has elapsed. 
     The display apparatus  3 B generates image data of the bicycle  801 V in a predetermined region based on image data of the bicycle  801  generated by the camera  901 . An example of a method performed by the display apparatus  3 B for generating image data of the bicycle  801 V is given below. First, the image processing unit  13  of the display apparatus  3 B performs a linear transformation on the image data of the bicycle  801  and moves it to a predetermined region. Then, the image processing unit  13  checks whether each pixel of the moved image data corresponds to the first region or the second region. Further, the image processing unit  13  selects a predetermined color from among R, G and B for the pixel corresponding to the first region, and sets the output value so that the image is displayed by the selected color. Then, the image processing unit  13  sets the output value of the UV of the pixel included in the first region to zero. Similarly, the image processing unit  13  selects UV for the pixel corresponding to the second region, and sets the output value so that the image is displayed by ultraviolet light. Then, the image processing unit  13  sets the output value of each of R, G and B of the pixel included in the second region to zero. 
     Further, as shown in  FIG. 15 , the display apparatus  3 B may display, in addition to the display of the pseudo bicycle  801 V, character information for making the driver recognize the risk, the position, and the like of the bicycle  801  on the windshield  904 . For example, the display apparatus  3 B may display character information indicating that the traveling bicycle is in the blind spot. 
     As described above, the display apparatus according to the third embodiment can display a pseudo object regardless of whether the target projection region is the first region or the second region. Thus, it is possible to perform display so that the driver can intuitively recognize the display. 
     Any processing of the above-described display apparatuses can also be implemented by causing a Central Processing Unit (CPU) to execute a computer program. In this case, the computer program can be stored and provided to a computer using any type of non-transitory computer readable media. Non-transitory computer readable media include any type of tangible storage media. Examples of non-transitory computer readable media include magnetic storage media (such as floppy disks, magnetic tapes, hard disk drives, etc.), optical magnetic storage media (e.g., magneto-optical disks), Compact Disc Read Only Memory (CD-ROM), CD-R, CD-R/W, and semiconductor memories (such as mask ROM, Programmable ROM (PROM), Erasable PROM (EPROM), flash ROM, Random Access Memory (RAM), etc.). The program may be provided to a computer using any type of transitory computer readable media. Examples of transitory computer readable media include electric signals, optical signals, and electromagnetic waves. Transitory computer readable media can provide the program to a computer via a wired communication line (e.g., electric wires, and optical fibers) or a wireless communication line. 
     Further, in addition to the cases where the functions of the aforementioned embodiments are implemented by causing a compute to execute a program that is used to implement functions of the aforementioned embodiments, other cases where the functions of the aforementioned embodiments are implemented with cooperation with an Operating System (OS) or application software running on the computer are also included in the embodiments of the present disclosure. Further, other cases where all or part of the processing of this program is executed by a function enhancement board inserted into the computer or a function enhancement unit connected to the compute to implement the functions of the aforementioned embodiments are also included in the embodiments of the present disclosure. 
     Note that the present disclosure is not limited to the above-described embodiments and may be modified as appropriate without departing from the spirit of the present disclosure. For example, the above-described display apparatus can be applied not only to an automobile but also to a mobile body such as a train, an aircraft, and a ship. Further, the display technology used in the above-described display apparatus can be applied not only to the above-described mobile body but also to a house or outdoors.