Abstract:
A Head Up Display (HUD), comprising: an image display unit, to generate input images; a virtual image generation unit, to receive said input images and generate at least a virtual image; a rotation mechanism, used to make said virtual image generation unit to change its projection angle, to project virtual images to a plurality of transmission mirrors; and a plurality of transmission mirrors, used to receive said virtual images and reflect them into a large area virtual image. Advantage of said HUD is that, size of lens and mirrors is reduced, so said HUD is miniaturized, while realizing large area image display, such that information frame of vehicle match that of outside view, hereby solving problems of single optical route display device of the prior art, that is only capable of displaying a small area image rather than a large area image.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an optical system, and in particular to a Head Up Display (HUD) suitable for use in a moving vehicle. 
     2. The Prior Arts 
     It is well known that the Head Up Display (HUD) is an auxiliary aviation instrument that is first utilized in an aircraft, so that a pilot is able to look at the information on the panel without lowering his head, to avoid interruption of attention and lose Situation Awareness. The Head Up Display (HUD) can not only provide convenience in usage, but it can also raise the aviation safety. Therefore, it can be used in any types of the moving vehicles, such as aircrafts, or even automobiles and ships. 
     In the past, the Head Up Display of the prior art could provide only a small display area of simple instrument information within the eyesight of the driver, to indicate the critical information related to the moving vehicle. For the Head Up Displays (HUD) of the prior art, most of them belong to a single optical-route display device having only a small display area, and that is realized through the following ways. Firstly, the critical information is projected onto an optical device, and the display screen is placed inside the wind shield and facing the wind shield, so that the critical information is transmitted to the display screen through the optical device. Then, the critical information displayed on the display screen is reflected by the wind shield and displayed on the wind shield. Also, the position of display is in the eyesight directly in front of the driver, so that in driving a vehicle, the driver is able to view directly the vehicle driving speed or other data he desires to know, without the need to raise or lower his head to change his eyesight. However, according to the optical imaging principle of such a single optical-route display device, for any lens or mirrors utilized, the imaging area of the input image is positively proportional to the size of lenses and mirrors. As such, a Head Up Display requires an enormously large lens or mirror to project out virtual images, thus it is not easy to integrate such a single optical-route display device with an instrument panel into an integral unit, since the volume required by such a Head Up Display would be too large for the panel full of wires and connections. In addition, in order to keep the quality of imaging, the size of optical elements used for a Head Up Display can not be reduced further, therefore, it is rather difficult to achieve large display area in a very limited space of the driver cabin. Also, for the information displayed in an overly small display area, the driver is not able to obtain critical information right away by just glancing briefly over instrument control panel. Or, in case that the driver does raise his head to look at and get the critical information on the display panel in detail, that could disrupt his attention and put him in an immediate danger. 
     Therefore, presently, the design and performance of the Head Up Display (HUD) is not quite satisfactory, and it has much room for improvements. 
     SUMMARY OF THE INVENTION 
     In view of the problems and shortcomings of the prior art, the present invention provides a Head Up Display (HUD), for which size of optical elements such as lens or mirrors can be reduced drastically to have a larger display area, hereby realizing a high caliber Head Up Display (HUD), while achieving safety and efficiency. 
     A major objective of the present invention is to provide a Head Up Display (HUD). Wherein, a rotation mechanism partitions the image signals into individual images, and that is coupled with a technical means of re-converging images to realize imaging. In the present invention, lens or mirror of ordinary size is used to produce even larger display area, or the size of lens or mirror can be reduced, to reduce the volume of the head up display (HUD), so as to achieve large area image display effect in a limited space of a vehicle. The information frame provided by the Head Up Display can overlap entirely the images of an outside view, or the information frame can be matched with images of outside view to make a display as required, to help the driver to pay attention to the critical information of the moving vehicle, in solving shortcomings of the prior art that the single optical-route display device can only achieve small area display. 
     Another objective of the present invention is to provide a Head Up Display (HUD), that utilizes a rotation mechanism to project and converge individual images, and to adjust its image display angle based on the height and seating gesture of the driver by means of the adjustability of a transmission mirror. Compared with the single optical-route display device of the prior art, the present invention enables the driver to have full attention driving and comfort in driving. 
     In order to achieve the above-mentioned objective, the present invention provides a Head Up Display (HUD), at least comprising: an image unit, used to produce one or more input images; a least a virtual image generation unit, to receive input image and produce at least a virtual image; a rotation mechanism, capable of controlling rotation angles of the virtual image generation unit, to change the virtual image projection angle of the virtual image generation unit; and a plurality of transmission mirrors, used to receive virtual images and reflect them into a large area virtual image. 
     Further scope of the applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the present invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the present invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The related drawings in connection with the detailed description of the present invention to be made later are described briefly as follows, in which: 
         FIG. 1  is a system block diagram of a Head Up Display (HUD) according to the present invention; 
         FIG. 2  is a schematic diagram of an optical mechanism of the head up display according to the first embodiment of the present invention; 
         FIG. 3A  is a schematic diagram of a virtual image generation unit of the head up display according to the first embodiment of the present invention; 
         FIG. 3B  is a schematic diagram of a virtual image generation unit and rotation mechanism of the head up display according to the first embodiment of the present invention; 
         FIG. 4  is a schematic diagram of image formation of virtual image generation unit according to the first embodiment of the present invention; 
         FIG. 5  is a schematic diagram of large area image formation according to the first embodiment of the present invention; 
         FIG. 6  is a schematic diagram of optical characteristics of a concave lens according to the first embodiment of the present invention: 
         FIG. 7  is a schematic diagram of a curved mirror image formation according to the first embodiment of the present invention; 
         FIG. 8A  is a schematic diagram of an adjustable transmission mirror according to the first embodiment of the present invention; 
         FIG. 8B  is a front view of an adjustable transmission mirror according to the first embodiment of the present invention; 
         FIG. 8C  is a top view of the adjustable transmission mirror according to the first embodiment of the present invention; 
         FIG. 9A  is a schematic diagram of vision converged range according to the first embodiment of the present invention; 
         FIG. 9B  is a schematic diagram of left half portion and right half portion of vision converged image according to the first embodiment of the present invention; 
         FIG. 9C  is a schematic diagram of upper half portion and lower half portion of vision converged image according to the first embodiment of the present invention; and 
         FIG. 10  is a system block diagram of a Head Up Display (HUD) according to the second embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The purpose, construction, features, functions and advantages of the present invention can be appreciated and understood more thoroughly through the following detailed description with reference to the attached drawings. 
     The present invention provides a Head Up Display (HUD), that utilizes a rotation mechanism and a virtual image generation unit to partition images, or a plurality of image display units are used to present the individual image, and that is supplemented with an image re-converging means, to display large area image, while reducing sizes of lens or mirror. In the present invention, optimal image display angle can be obtained based on height and seating gesture of the driver through using the adjustability of the transmission mirrors. 
     Refer to  FIG. 1  for a system block diagram of a Head Up Display (HUD) according to the present invention. As shown in  FIG. 1 , the Head Up Display (HUD)  10  of the present invention includes: an image display unit  16 , and an optical mechanism  18 , such that the HUD  10  operates in cooperation with an image fetching unit  12  made of charge-coupled device (CCD) elements or CMOS elements; and also in cooperation with a processing unit  14 , that can be a central processor unit (CPU), a microprocessor, or a single chip micro-computer. Wherein, the image display unit  16  is made of a liquid crystal display (LCD) or a digital optical projector. When the processing unit  14  is connected electrically to the image fetching unit  12  and the image display unit  16 , one or more image fetching units  12  can be used to fetch images of views in front of the moving vehicle, such as lane markings, horizontal line, or obstacle contours; or, additionally, one or more image fetching units  12  installed around the perimeter of the moving vehicle can be used to fetch images of blind angle as external signals. The processing unit  14  integrates the critical information required by the moving vehicle, such as the external signals received by the image fetching unit  12 , and at the same time proceeds with receiving and processing the signals of moving vehicle relating to vehicle operation temperature, engine rotation speed, vehicle driving speed, guidance information, tire pressure, gear shift reminder, turning-around and back-up reminder, obstacle warning, flying attitude, flying speed, flying direction, vertical speed variations, vehicle inclination angle, wind direction, vehicle moving-forward or slow-down, or obstacle warning obtained through detecting obstacle contour. As such, the processing unit  14  combines the critical information required by the moving vehicle, and processes them into an image signal. Finally, the processor unit  14  transmits the image signals to the image display unit  16 , for it to generate at least an input image and transmit it to the optical mechanism  18 . 
     Then, refer to  FIGS. 2 ,  3 A, and  3 B respectively for a schematic diagram of an optical mechanism of the head up display according to the first embodiment of the present invention; a schematic diagram of a virtual image generation unit of the head up display according to the first embodiment of the present invention; and a schematic diagram of a virtual image generation unit and rotation mechanism of the head up display according to the first embodiment of the present invention; meanwhile refer to  FIG. 1 . In this embodiment, a plurality of micro-mirrors on a digital micro-mirror device (DMD) is used as a virtual image generation unit. As shown in the drawings, the Head Up Display (HUD)  10  at least includes: an image display unit  16 , to generate one or more input images; and an optical mechanism  18 , to receive input image and generate virtual images. As shown in  FIGS. 2 ,  3 A,  3 B, the optical mechanism  18  at least includes: an image display unit  16 , a digital micro-mirror device  24 , and a plurality of transmission mirrors  28 . Wherein, the virtual image generation unit  22  in the digital micro-mirror device  24  receives the input image generated by the image display unit  16 , and it generates at least a virtual image; and the plurality of transmission mirrors  28  receive the corresponding virtual images and reflect them into a large area virtual image. The detailed structure of the virtual image generation unit  22  is as shown in  FIG. 3A , wherein, a plurality of virtual image generation units  22  (also referred to as magnifying optical elements) are arranged into a matrix array, to form a digital micro-mirror device  24 . The virtual image generation unit  22  operates in cooperation with the rotation mechanism  26 , so that its rotation angle is controlled, to change the virtual image projection angle. Since each of the input image is composed of a plurality of pixels, and each virtual image generation unit  22  corresponds to at least a pixel, such that the technical means of the present invention is that, the number of transmission mirrors  28  is equal to the number of sway states of the rotation mechanism  26 . Namely, in  FIG. 2 , the rotation mechanism  26  having left and right two sections of sway states is taken as an example for explanation, therefore, two transmission mirrors  28  are used for implementation. In case that the rotation mechanism  26  is designed to have left, middle, and right three sections of sway states, then three transmission mirrors  28  are required for implementation. Similarly, in case that the rotation mechanism  26  is designed to have a plurality of sway states, then equal number of transmission mirrors  28  are provided, and its operation principle is similar, thus it will not be repeated here for brevity. 
       FIG. 3B  shows the detailed structure of the rotation mechanism  26 , wherein, the rotation mechanism  26  includes an actuation unit  30 , and a power unit  32 . The actuation unit  30  is composed of a gear wheel  34  and a rack  36 , and the power unit  32  may utilizes a micro motor, such that the power unit  32  can provide power required to bring the actuation unit  30  into action, so that the actuation unit  30  may control the virtual image generation unit  22 . Meanwhile, the rotation mechanism  26  sways the virtual image generation unit  22  rapidly in a period of 1/60 second. Namely, the virtual image generation unit  22  is swayed 60 times or more per second to project the virtual image to the transmission mirrors  28  in front. Due to the persistence of human eye vision, the transmission mirrors  28  present a virtual image display screen. 
     Subsequently, refer to  FIGS. 4 ,  5 ,  6 , and  7  respectively for a schematic diagram of image formation of virtual image generation unit, large area image formation, optical characteristics of a concave lens, and a curved mirror image formation according to the first embodiment of the present invention. As shown in  FIGS. 4 and 5 , the virtual image generation unit  22  can be an optical element, such as a concave lens  38  or a convex lens  40 , either of them utilizes optical principle of upright magnified virtual image to generate virtual images, thus image is formed outside the window in a large area manner, such that the virtual image generated can at least match the actual lane marking  42 , and corresponds to the virtual image lane marking  44 . 
     As shown in  FIG. 6 , the optical characteristics of the concave lens  38  of the present invention are that, when its radius of curvature R is ∞, then it is a concave lens  38 , with its focal length ∞; and when its radius of curvature R is 100, then it is an arc concave lens  38 , with its focal length  50 . The concave lens  38  may produce virtual image, and its focal length is as shown in equation (1):
 
 f=R/ 2  (1)
 
     the curved surface of the concave lens  38  can be designed to be an aspheric surface, to avoid generating optical aberrations. When the input image is placed within the focal length, the concave lens  38  will present a magnified virtual image, with its magnification ratio as shown in equations (2) and (3):
 
1/ S+ 1/ S′ =1/ f   (2)
 
 m=S′/S   (3)
 
In equations (1) to (3), R is a radius of curvature, S is an object distance, S′ is an image distance, f is a focal length, and m is a magnification ratio.
 
     Then, as shown in  FIG. 7 , in case that the HUD  10  is used in an automobile, the image display area may correspond to the virtual image lane marking  44 , with the image covering an area of 4 meter wide by 1 meter high. Wherein, the transmission mirror  28  is a planar plate having high reflectivity optical thin film, with its transmission rate between 70% and 75%, and its reflection rate between 25% and 30%, and it is put inside the wind shield  46 . As such, the driver may gaze the virtual image in front through the transmission mirror  28  and the wind shield  46  in sequence, such that the virtual image overlaps the views in front, or it displays the virtual image corresponding to the views in front, and when the number is large for the transmission mirrors  28  and the corresponding optical routes, the transmission mirrors  28  appear as a curved mirror  48 , so as to display a large image. In addition, through the adjustability of the transmission mirror  28 , a driver may adjust the display angle of the transmission mirror  28  based on his height and seating gesture. In  FIGS. 5 and 7 , an automobile is used as moving vehicle for explanation, so the virtual image lane marking  44  is used as a reference for explanation. Of course, for other moving vehicles such as aircrafts or ships, horizontal lines can be used as a reference, and its principle of operation is the same as mentioned above, and it will not be repeated here for brevity. 
     Refer to  FIGS. 8A ,  8 B, and  8 C respectively for a schematic diagram, a front view, and a top view of an adjustable transmission mirror according to the first embodiment of the present invention. As shown in  FIGS. 8A ,  8 B, and  8 C, the transmission mirror  28  of the present invention is adjustable, so that a driver may adjust it to a proper display angle based on his height and seating gesture. As shown in  FIG. 8A , the transmission mirror  28  is fixed on a rotation mechanism  50 , and that is in turn disposed on a rotation actuation mechanism  52 , so that the rotation mechanism  50  can be rotated around the horizontal axis X in a clockwise or a counterclockwise direction, and the rotation actuation mechanism  52  can be rotated around vertical axis Y in a clockwise or a counterclockwise direction, such that the transmission mirror  28  is adjustable, and it can be adjusted to a proper display angle based on the height and seating gesture of the driver. As shown in  FIGS. 8B and 8C , the rotation mechanism  50  and the rotation actuation mechanism  52  can be rotated based on the position of human eyes  54 , to adjust the transmission mirror  28  to an optimal display angle. 
     Refer to  FIGS. 9A ,  9 B, and  9 C for a schematic diagram of vision converged range, left half portion and right half portion of vision converged image, upper half portion and lower half portion of vision converged image according to the first embodiment of the present invention. As shown in  FIGS. 9A ,  9 B, and  9 C, in the Head Up Display (HUD)  10  of the present invention, a vision converged range  56  is provided, so that the transmission mirror  28  is able to reflect the virtual image into the vision converged range  56  to present a large area virtual image. Since in the first embodiment of the present invention, at least two input images are taken as example for explanation, so two optical routes are used to present the left half portion  58 , the right half portion  60 , or the upper half portion  62 , the lower half portion  64  of the virtual image, and reflects them into the vision converged range  56 . When various parts of virtual images are combined together in vision converged range  56 , a large area virtual image can be observed. Similarly, in case that three or more input images are taken as embodiment, then three or more portions of virtual images can be presented in the vision converged range  56 . Its principle of implementation is the same as that mentioned above, thus it will not be repeated here for brevity. 
     Finally, refer to  FIG. 10  for a system block diagram of a Head Up Display (HUD) according to the second embodiment of the present invention, meanwhile refer to  FIGS. 4 ,  9 A,  9 B, and  9 C. As shown in  FIG. 10 , a head up display (HUD)  10  further includes a light source generation element  65 , that can serve as a light source. In the optical mechanism  18 , a digital micro-mirror device (DMD) is used to realize the image display unit  66 . Since the image display unit  66  is composed of a plurality of micro-mirrors to form into a matrix array, and each input image contains a plurality of pixels, so each of micro-mirrors corresponds to each of the pixels, such that the number of micro-mirrors on the image display unit  66  is equal to the number of pixels. When the image display unit  66  receives lights coming from the light source generation element  65 , it generates one or more input images. Since the image display unit  66  is able to control the on and off states of each pixel (similar to a digital switch 1-on or 0-off state), so it can determine which part of pixels is to be projected. When the micro-mirrors on the image display unit  66  project a portion of pixels onto the virtual image generation unit  68 , that will in turn project the virtual image to the transmission mirror  28 , to realize the same purpose and effect of combining various virtual images into a large area virtual image of the first embodiment, as shown in  FIG. 4 . In the present embodiment, the virtual image generation unit  68  may use a concave lens  38  or a convex lens  40 , likewise, it utilizes optical principle of upright magnified virtual image to generate virtual images. Similarly, in the present embodiment, a rotation mechanism  70  controls the rotation angles of the virtual image generation unit  68 , so the virtual image generation unit  68  is able to change the projection angle of the virtual image, to project each of the pixels to the transmission mirrors  28 , and that receives the corresponding virtual images and reflects them into a large area virtual image. Moreover, the rotation mechanism  70  includes an actuation unit  72  and a power unit  74 . The actuation unit  72  can be a gear wheel  76 , a rack  78 , or a combination of them; while the power unit  74  can be a step motor. Similarly, the rotation mechanism  70  sways the virtual image generation unit  68  rapidly in a period of 1/60 second, also the vision persistence of human eye works the same way as it does in the first embodiment, thus it will not be repeated here for brevity. In this second embodiment, at least two input images are taken as example for explanation, therefore, likewise, two optical routes are utilized to present and reflect the left half portion  58  and the right half portion  60 , or the upper half portion  62  and the lower half portion  64  of virtual image into the vision converged range  56 . Its principle of implementation is the same as the first embodiment, and it will not be repeated here for brevity. 
     The above detailed description of the preferred embodiment is intended to describe more clearly the characteristics and spirit of the present invention. However, the preferred embodiments disclosed above are not intended to be any restrictions to the scope of the present invention. Conversely, its purpose is to include the various changes and equivalent arrangements which are within the scope of the appended claims.