Patent Publication Number: US-2013235158-A1

Title: Stereoscopic Image Display Apparatus and Stereoscopic Image Eyeglasses

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. application Ser. No. 13/098,952, now abandoned, which is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2010-187634, filed on Aug. 24, 2010, the entire contents of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to a stereoscopic image display apparatus capable of displaying a stereoscopic image, and stereoscopic image eyeglasses. 
     BACKGROUND 
     In recent years, a display for displaying stereoscopic image contents has been put to practical use. Various stereoscopic image display methods have been proposed. For example, as such methods, polarization filter eyeglasses or electronic shutter eyeglasses may be used. 
     For example, the polarization filter eyeglasses have a left-eye-lens and a right-eye-lens respectively provided with polarization filters having polarization directions orthogonal to each other. In a stereoscopic image display using the polarization filter eyeglasses, first, light rays respectively representing a left-eye-image and a right-eye-image are linearly polarized to have vibration directions orthogonal to each other. Next, the linearly polarized light rays are projected while being superimposed. Then, the projected light rays are split into the left-eye-image and the right-eye-image by the polarization filter eyeglasses. Thus, the left-eye-image and the right-eye-image having a parallax therebetween are simultaneously displayed in a left eye and a right eye, respectively. 
     For example, the electronic shutter eyeglasses have shutters each configured to open/close synchronously with images displayed in the display-device. When a right-eye-image is displayed in a display-device, a left-eye-shutter of the electronic shutter eyeglasses is closed while a right-eye-shutter is opened. Thus, only the right-eye-image can be seen. On the other hand, when a left-eye-image is displayed in the display-device, the right-eye-shutter is closed while the left-eye-shutter is opened. Thus, only the left-eye-image can be seen. Thus, the right-eye-image and the left-eye-image having a parallax therebetween are alternately displayed in left and right eyes. 
     In the stereoscopic image display, a display-device displays stereoscopic-dedicated images, and the user wears eyeglasses. When the user sees the stereoscopic-dedicated images on a screen without such eyeglasses, the right-eye-image and the left-eye-image overlap with each other due to a parallax therebetween, and the images on the screen cannot be viewed as a normal image. 
     For example, in broadcast of video programs and in distribution of video contents (video disc such as optical disc), conventional plane images (hereinafter, a conventional image differing from a stereoscopically-displayed image is referred to as a “plane image”, as compared with a “stereoscopic image”) and stereoscopic images coexist. Thus, the user needs to wear and take off stereoscopic image eyeglasses corresponding to the reproduction of a stereoscopic image and that of a plane image, respectively. 
     At present, there are few stereoscopic image contents yet, while there are many plane image contents. Thus, there are proposed plural conversion methods for performing arithmetic processing on a plane image to convert it into a stereoscopic image. However, sometimes, a stereoscopic image obtained from a plane image through such conversion method has less quality than contents which are originally generated as stereoscopic images. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       A general architecture that implements the various features of the present invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate embodiments of the present invention and not to limit the scope of the present invention. 
         FIG. 1  illustrates configurations of a stereoscopic image display apparatus and stereoscopic image eyeglasses according to an embodiment. 
         FIG. 2  illustrates the stereoscopic image display apparatus. 
         FIG. 3  illustrates the stereoscopic image eyeglasses. 
         FIG. 4  illustrates the distance of the stereoscopic image eyeglasses to the stereoscopic image display apparatus and the angle of the stereoscopic image eyeglasses with respect to the stereoscopic image display apparatus. 
         FIG. 5  illustrates an example of a conversion method to convert a plane image into a stereoscopic image. 
         FIG. 6  illustrates another example of the conversion method to convert a plane image into a stereoscopic image. 
         FIG. 7  illustrates an operation procedure for transmitting wearing information from stereoscopic image eyeglasses. 
         FIG. 8  illustrates an operation procedure for switching between a plane image and a stereoscopic image according to a user&#39;s wearing state of the stereoscopic image eyeglasses. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a stereoscopic image display apparatus includes: a measurement module configured to measure a distance from a display screen to stereoscopic image eyeglasses, and an angle of the stereoscopic image eyeglasses with respect to a normal to the display screen; and a converter configured to convert a plane image into a stereoscopic image based on the distance and the angle. 
     It is preferable to perform conversion according to a position of a user wearing stereoscopic image eyeglasses with respect to a display screen. In addition, it is preferable to perform conversion of a plane image into a stereoscopic image according to a user&#39;s wearing state of stereoscopic image eyeglasses. 
       FIG. 1  illustrates configurations of a stereoscopic image display apparatus  1  and stereoscopic image eyeglasses  2  according to an embodiment. An antenna  4  is a digital terrestrial broadcast antenna or a digital satellite broadcast antenna for receiving broadcast electric waves transmitted from a broadcast station  3 . A tuner  5  selects broadcast signals of a desired channel from digital terrestrial broadcast signals and digital satellite broadcast signals. The tuner  5  includes plural tuner units and can simultaneously receive plural broadcasts. 
     A demodulator  6  demodulates signals according to a modulation method for each digital broadcast signal. Digital terrestrial broadcast signals are demodulated by an orthogonal frequency division multiplexing (OFDM) demodulation method. Digital satellite broadcast signals are demodulated by a phase shift keying (PSK) demodulation method. Thus, the broadcast signals are demodulated into digital image and audio signals which are output to a signal processor  7 . 
     The signal processor  7  selectively performs predetermined digital signal processing on digital image and audio signals supplied from the demodulator  6 . The signal processor  7  outputs the image signals to a three-dimensional (3D) image converter  8  or an image processor  9 . The signal processor  7  outputs the audio signals to an audio processor  12 . The signal processor  7  has the functions of a Moving Picture Experts Group (MPEG) encoder, an MPEG decoder, and an image/audio decoder. 
     In a case where image signals supplied from the demodulator  6  represent plane images, and where the plane image is converted into a stereoscopic image, the signal processor  7  outputs image signals to the 3D image converter  8 . If the plane image is not converted into a stereoscopic image, the signal processor  7  outputs image signals to the image processor  9 . If the image signal supplied from the demodulator  6  represents a stereoscopic image, the signal processor  7  outputs the image signal to the image processor  9 . 
     There are various methods for stereoscopically displaying an image by simultaneously or alternately displaying a right-eye-image and a left-eye-image, which have binocular parallax, on a screen to thereby enable the user to recognize the image as a stereoscopic image due to binocular parallax. For example, a Blu-ray (trademark) display employs a frame sequential method. Thus, a left-eye-image and a right-eye-image are alternately reproduced on a screen at a high speed of 120 frames (in total) per second by reproducing each of the left-eye-image and the right-eye-image at 60 frames per second. Then, with the dedicated stereoscopic eyeglasses having a left shutter and a right shutter that are alternately opened/closed synchronously with the displaying of a left-eye-image and a right-eye-image, a stereoscopic image can be seen on the screen. 
     For example, a digital television broadcast employs a side-by-side method. According to the side-by-side method, frames are sent to an image display apparatus by arranging a left-eye-image and a right-eye-image side by side in each frame. A single screen is divided into two parts respectively corresponding to a left-eye-image and a right-eye-image. Thus, a lateral resolution decreases by half. If an original image has a resolution of 1920×1080 dots, a left-eye-image and a right-eye-image each having a resolution of 960×1080 dots are sent to the image display apparatus which expands each of the left-eye-image and the right-eye-image and which displays the expanded left-eye-image and the expanded right-eye-image on the screen thereof. When processing image signals supplied from the demodulator  6 , the signal processor  7  determines which of a plane image and a stereoscopic image the signal represents. Then, the signal processor  7  sends a determination result to a controller  15 . 
     The 3D image converter  8  has the function of converting a plane image (two-dimensional (2D) image) into a stereoscopic image (3D image). Particularly, a plane image is converted into a left-eye-image and a right-eye-image for a stereoscopic image with binocular parallax, while estimating depth information. Among various methods for estimating the depth information, one method may be selected to be used according to the arithmetic capacity of the converter  8 . The 3D image converter  8  converts a plane image transmitted from the signal processor  7  into a stereoscopic image and outputs the stereoscopic image to the image processor  9 . 
     The image processor  9  converts the format of digital image data input from the signal processor  7  or the 3D image converter  8  into a format to be displayable on a screen  11  of the display unit  10 . In addition, the image processor  9  optionally adjusts display colors. Then, the image processor  9  outputs the converted data to the screen  11  to thereby display an image. The controller  15  changes an input source between the signal processor  7  and the 3D image converter  8 . The image processor  9  has the function of converting a stereoscopic image input from the signal processor  7  into a plane image according to an instruction from the controller  15 . 
     An audio processor  12  converts digital audio data input from the signal processor  7  into an analog audio signal to be reproducible by a speaker  13 . Then, the audio processor  12  outputs the analog audio signal to the speaker  13  and causes the speaker  13  to reproduce a sound. 
     All operations including the above reception operation of the stereoscopic image display apparatus  1  are collectively controlled by the controller  15 . A micro processing unit (MPU)  16  is mounted on the controller  15  and controls each composing element connected thereto via a bus  14 . 
     A random access memory (RAM)  17  is a read/write memory that stores various data necessary for data processing in the MPU  16  and operates as a buffer memory that stores image data and the like. A read-only memory (ROM)  18  is a read-only memory from which data is read, and stores a control program to be executed by the MPU  16 , and the like. 
     A flash memory  19  is a rewritable nonvolatile semiconductor memory in which data is not lost when power is turned off. The flash memory  19  stores setting-data which concerns the display of the display unit  10  and is set by the user. The setting-data is, e.g., set values of luminance and contrast. 
     An operation receiver  20  receives an operation signal transmitted from an operation interface  21  and transfers the operation signal to the MPU  16 . The operation interface  21  is, e.g., a remote controller utilizing wireless communication, e.g., infrared communication and Bluetooth communication, or a wired or wireless keyboard. The operation interface  21  sends operation signals. The operation receiver  20  receives the operation signals from the remote controller, the keyboard, or the like. 
     The communication controller  22  generates a control signal based on an instruction from the MPU  16 , and sends the control signal to the stereoscopic image eyeglasses  2 . The communication controller  22  sends the generated control signal to the stereoscopic image eyeglasses  2  via a transmitting/receiving device  23  such as an antenna or an infrared-emitting device. The communication controller  22  and the transmitting/receiving device  23  function as a receiving module configured to receive information transmitted from the stereoscopic image eyeglasses  2 , the information representing a wearing state in which the user wears the stereoscopic image eyeglasses  2 . 
     A distance/angle measurement module  24  measures a position of the stereoscopic image eyeglasses  2  with respect to the stereoscopic image display apparatus  1 . Particularly, the distance/angle measurement module  24  measures the distance of the stereoscopic image eyeglasses  2  from the substantial center of the screen  11 , and an angle of the stereoscopic image eyeglasses  2  with respect to a normal to the surface of the screen  11  at the substantial center. The distance/angle measurement module  24  performs optical scanning over an angular range of 180 degrees at the front surface side of the screen  11  to measure the distance from the substantial center of the screen  11  to a reflector of the stereoscopic image eyeglasses  2  and the angle of the reflector with respect to the normal to the screen  11 . The distance is detected by measuring a time difference between a moment at which pulse-like laser light is irradiated from the distance/angle measurement module  24 , and a moment at which the laser light reflected by the reflector returns thereto. The angle is detected, based on a direction from which the reflected laser-light returns thereto, among directions respectively corresponding to angles obtained by dividing the angular range of 180 degrees by a large number at the front surface side of the stereoscopic image display apparatus  1 . Information representing the detected distance and the detected angle is converted into digital data. The obtained digital data is output to the controller  15  and stored in the RAM  17 . 
     Another example of the distance/angle measurement module  24  can be such that an image of a scene in the direction of the user is taken with a camera at a central upper portion of the screen  11 , that the taken image is analyzed, that the above angle is measured according to the position of the image of the stereoscopic image eyeglasses  2 , and that the distance is measured according to the size of the image of the stereoscopic image eyeglasses  2 . A more accurate value of the distance can be measured according to a focal length of the camera, which is determined by focusing on the stereoscopic image eyeglasses  2 . 
     An external interface  25  is an interface such as a universal serial bus (USB) interface, an Institute of Electrical and Electronic Engineers (IEEE) 1394 interface, an external Serial ATA (AT Attachment) (eSATA) interface, a secure digital (SD) (trademark) memory card, and a high definition multimedia interface (HDMI) (trademark). An external storage device  26 , such as a USB memory, a USB external device, an SD memory card and drives (such as a hard disk drive (HDD), a solid-state drive (SSD), a compact disc (CD), a digital versatile disc (DVD), and a Blu-ray (trademark) recording/reproducing device), are connected to the external interface  25 . 
     The controller  15  has the function of a parameter generator. This function is implemented by an application-program executed by the MPU  16  of the controller  15 . Usually, the application-program is stored in the ROM  18  and read and executed by the MPU  16  when used. A parameter generator  27  is an output module configured to output, based on the distance and the angle measured by the distance/angle measurement module  24 , a conversion parameter used when the 3D image converter  8  converts a plane image to a stereoscopic image. A depth parameter for adjusting an optimal depth amount is output, based on the distance from the substantial center of the screen  11  to the stereoscopic image eyeglasses  2 . A parallax parameter for adjusting a vector amount corresponding to the parallax caused when a subject is viewed from a left eye and a right eye is output, based on the angle of the stereoscopic image eyeglasses  2  with respect to the normal to the screen  11  at the substantial center. 
     The depth parameter and the parallax parameter are output by the parameter generator  27  to the 3D image converter  8 . By using the parameters, the 3D image converter  8  can convert a plane image into a stereoscopic image to have an optimal effect according to a user&#39;s position. 
     In the stereoscopic image eyeglasses  2 , a controller  31  includes a micro controller unit (MCU) serving as a built-in microprocessor, which a computer system is integrated onto a single integrated circuit. Peripheral function components, such as a ROM, a RAM, and input/output (I/O) associated parts, are mounted thereon. The controller  31  controls operations of the entire stereoscopic image eyeglasses  2 . A wear sensor  33 , liquid crystal shutters  34 , and a transmitting/receiving device  35  are connected to the controller  31  via a data bus  32 . 
     The controller  31  has a sensor controller  31   a,  a shutter controller  31   b,  and a communication controller  31   c . These elements are implemented by application-programs executed by the MCU of the controller  31 . Usually, the application-programs are stored in the ROM provided in the controller  31  and read and executed by the MCU when used. 
     The detector for detecting a wearing state of the user includes the sensor controller  31   a  and a wear sensor  33 . A transmitting module includes the communication controller  31   c  and the transmitting/receiving device  35 . The sensor controller  31   a  receives output signals of the wear sensor  33  mounted on the stereoscopic image eyeglasses  2 , converts the received signal into a signal suited to communication, and transmits to the stereoscopic image display apparatus  1  wearing information (i.e., information indicating that the user wears the stereoscopic image eyeglasses  2 )  36  or non-wearing information (i.e., information indicating that the user removes the stereoscopic image eyeglasses  2 )  37  via the communication controller  31   c  and the transmitting/receiving device  35  implemented by an antenna or the like. 
     The wear sensor  33  includes a light emitter  33   a  and a light receptor  33   b.  The light emitter  33   a  and the light receptor  33   b  are provided in left and right temples, respectively, by being separated from each other so that light emitted from the light emitter  33   a  is received by the light receptor  33   b.  When the user wears the stereoscopic image eyeglasses  2 , light emitted from the light emitter  33   a  is shielded. Thus, it is detected that the user wears the stereoscopic image eyeglasses  2 . 
     The shutter controller  31   b  controls, based on shutter control signals transmitted from the stereoscopic image display apparatus  1 , shutter opening/closing operations of a right-eye liquid crystal shutter  34   a  and a left-eye liquid crystal shutter  34   b.  The liquid crystal shutters  34   a  and  34   b  are configured as follows. That is, when a right-eye-image is displayed in the stereoscopic image display apparatus  1 , the left-eye liquid crystal shutter  34   b  is closed, while the right-eye liquid crystal shutter  34   a  is opened. Thus, only the right-eye-image can be seen. On the other hand, when the left-eye-image is displayed therein, only the right-eye liquid crystal shutter  34   a  is closed, while the left-eye liquid crystal shutter  34   b  is opened. Thus, only the left-eye-image can be seen. 
     The communication controller  31   c  receives, via the transmitting/receiving device  35 , control signals transmitted from the stereoscopic image display apparatus  1  and outputs shutter control signals to the shutter controller  31   b.  The communication controller  31   c  transmits, via the transmitting/receiving device  35 , the wearing information  36  or the non-wearing information  37  to the stereoscopic image display apparatus  1 . 
       FIG. 2  illustrates the stereoscopic image display apparatus  1 . The stereoscopic image display apparatus  1  includes a casing  40 , and a stand  41  for supporting the casing  40 . A display panel  42 , such as a liquid crystal panel or a plasma display panel (PDP), is placed on the front surface side of the casing  40 . A frame (not shown) for supporting the display panel  42  is arranged on the back surface side of the display panel  42 . A circuit board (not shown) and a power supply circuit (not shown), which are used to drive the display panel  42 , are installed in the frame. 
     The outer surfaces of the stereoscopic image display apparatus  1  are surrounded by a front surface cover  43  for covering the front surface side, and a part of the top surface and both side surfaces of the casing  40 , and a back surface cover  44  for covering the front surface side, and a part of the top surface and both side surfaces of the casing  40 . The screen  11  is a portion for displaying an image within a window portion  43   a  of the front cover  43  of the display panel  42 . The transmitting/receiving device  20  is arranged in a front surface side part of the front surface cover  43 . 
     The distance/angle measurement module  24  is installed in a central upper part of the front surface of the front surface cover  43 . Because the distance of the stereoscopic image eyeglasses  2  from the substantial center of the screen  11  and the angle of the stereoscopic image eyeglasses  2  with respect to the normal to the surface of the screen  11  at the substantial center are measured, it is convenient to install the distance/angle measurement module  24  at an upper central part of the front surface cover  43 . The distance/angle measurement module  24  can be installed at a lower central part of the front surface of the front surface cover  43 . 
       FIG. 3  illustrates the stereoscopic image eyeglasses  2 . The stereoscopic image eyeglasses  2  include rims  46   a,    46   b , a bridge  47 , armors  48   a  and  48   b,  temples  49   a  and  49   b,  and liquid crystal shutters  34   a  and  34   b.  Each of the temples  49   a  and  49   b  is turnably attached to an associated one of the armors  48   a  and  48   b  with an associated one of hinges  50   a  and  50   b.    
     The transmitting/receiving device  35  for receiving control signals transmitted from the stereoscopic image display apparatus  1  is provided in the bridge  47 . The controller  31  is housed in the left armor  48   b.  A power switch  51  is provided on the outer side of the left armor  48   b.  The circuits of the wear sensors  33   a  and  33   b  are provided in the left temple  49   a  and the right temple  49   b,  respectively. A battery  52  for supplying electric power to the liquid crystal shutters  34   a  and  34   b  and the wear sensor  33  is provided in a part of the temple  49   b,  which is close to the armor  48   b.    
     A reflector  53  is provided at an upper part of the bridge  47 . The reflector  53  is a reflection plate for reflecting light emitted from the distance/angle measurement module  24  when the distance/angle measurement module  24  measures the position of the stereoscopic image eyeglasses  2  with respect to the stereoscopic image display apparatus  1 . If plural pairs of stereoscopic image eyeglasses  2  are used, one of the stereoscopic image eyeglasses  2  may be used to detect the position of the stereoscopic image eyeglasses  2 . The reflector  53  may not be provided on each of the other pairs of stereoscopic image eyeglasses. 
       FIG. 4  illustrates the distance of the stereoscopic image eyeglasses  2  to the stereoscopic image display apparatus  1  and the angle of the stereoscopic image eyeglasses  2  with respect to the stereoscopic image display apparatus  1 .  FIG. 4  is a plan view of the stereoscopic image display apparatus  1 , which is taken from above. A distance L is the distance between the substantial center of the screen  11  and the reflector  53  of the stereoscopic image eyeglasses  2 . An angle A is an angle of the reflector  53  of the stereoscopic image eyeglasses  2  with respect to a normal  54  to the surface of the screen  11  at the substantial center. More specifically, the angle A is an angle of the projection of the stereoscopic image eyeglasses  2  onto a plane parallel to a horizontal plane with respect to the normal. 
       FIG. 5  illustrates an example of a conversion method to convert a plane image into a stereoscopic image.  FIG. 5  illustrates an example of converting an image-pixel X of a plane image into a stereoscopic image. The 3D image converter  8  converts the image-pixel X of the plane image while estimating depth information corresponding to the image-pixel X of the plane image. The 3D image converter  8  converts the image-pixel X of a plane image into two image-pixels, i.e., a left-eye-image-pixel and a right-eye-image-pixel for a stereoscopic image with binocular parallax. There are various methods for estimating depth information, e.g., a method for analyzing anteroposterior layers, and a method for analyzing the speed of a moving object. Such method may be selected according to the arithmetic capacity of the 3D image converter  8 . 
     The image-pixel X is converted into a right-eye-image-pixel R and a left-eye-image-pixel L, based on depth information. An image-pixel X′ is a pixel which can be seen as that of a stereoscopic image in the direction of depth of the screen  11  after a plane image is converted into a stereoscopic image. As illustrated in  FIG. 5 , the image-pixel X of the plane image is seen as the image-pixel X′ located in the direction of depth of the screen  11  when a stereoscopic image is viewed. 
     The distance L and the angle A illustrated in  FIG. 4  are measured by the distance/angle measurement module  24 . As illustrated in  FIG. 5 , the image-pixel X is located at a position whose distance from the normal  54  to the surface of the screen  11  at the substantial center is M. A distance Ls is a distance from the stereoscopic image eyeglasses  2  to a foot of a perpendicular to the screen  11 . The distance Ls is calculated by the parameter generator  27  according to the distance L and the angle A. An angle B of the stereoscopic image eyeglasses  2  with respect to a normal to the surface of the screen  11  at the image-pixel X is calculated by the parameter generator  27  according to the distance L, the angle A, and the distance M. 
     A depth amount Ld is calculated according to depth information corresponding to the image-pixel X and a depth parameter Pd. The depth parameter Pd for adjusting an optimal depth amount Ld is set according to the value of distance Ls. Then, the value of the depth amount Ld is adjusted. The depth parameter Pd is a predetermined parameter determined by the value of the distance Ls. The depth parameter Pd is calculated after the distance Ls is calculated, based on a predetermined formula, by the parameter generator  27 . The calculated depth parameter Pd is output to the 3D image converter  8 . The 3D image converter  8  calculates the depth amount Ld according to the depth information corresponding to the image-pixel X and the depth parameter Pd, and converts the plane image into a stereoscopic image to have an optimal effect according to the user&#39;s position. Alternatively, the relationship between the distance Ls and the depth parameter Pd can be stored in the ROM  18  or the flash memory  19  in the table format. In addition, after the distance Ls is calculated, the depth parameter Pd may be read from the table. 
     The magnitude of the parallax vector Vd corresponding to the line-segment between the right-eye-image-pixel R and the left-eye-image-pixel L is “d”. The magnitude “d” of the parallax vector Vd is calculated according to the distance D between both eyes of the user, the distance Ls, and the depth amount Ld. The distance D between both eyes of the user can be replaced with the distance between the substantial centers of the right-eye liquid crystal shutter  34   a  and the left-eye liquid crystal shutter  34   b  of the stereoscopic image eyeglasses  2 . The relation among the magnitude d of the parallax vector Vd, the magnitude dR of a parallax vector VdR corresponding to the generated image-pixel R, and the magnitude dL of a parallax vector VdL corresponding to the generated image-pixel L is expressed by the following equation: 
     
       
      
       d=dR+dL  
      
     
     The parameter generator  27  outputs a parallax parameter Ppd for adjusting, according to an angle B, a rate of the magnitude of the parallax vector corresponding to the right-eye-image-pixel R and that of the parallax vector corresponding to the left-eye-image-pixel L. The parallax parameter Ppd is a predetermined parameter determined by the magnitude of the angle B. The parallax parameter Ppd is calculated after the angle B is calculated, based on the predetermined formula, by the parameter generator  27 . The calculated parallax parameter Ppd is output to the 3D image converter  8 . When calculating the magnitude dR of the parallax vector VdR and that dL of the parallax vector VdL, the 3D image converter  8  adjusts the rate between the magnitudes dR and dL, using the parallax parameter Ppd. Thus, the plane image can be converted into a stereoscopic image to have an optimal effect. Alternatively, the relationship between the angle B and the parallax parameter Ppd may be stored in the ROM  18  or the flash memory  19  in the table format. In addition, after the angle B is calculated, the parallax parameter Pp may be read from the table. 
       FIG. 6  illustrates another example of the conversion method to convert a plane image into a stereoscopic image.  FIG. 6  illustrates an example of converting an image-pixel Y of a plane image into image-pixels of a stereoscopic image. The 3D image converter  8  converts the image-pixel Y of the plane image into a left-eye-image-pixel and a right-eye-image-pixel for a stereoscopic image with binocular parallax while estimating depth information. There are various methods for estimating depth information, e.g., a method for analyzing anteroposterior layers, and a method for analyzing the speed of a moving object. Such method may be selected according to the arithmetic capacity of the 3D image converter  8 . 
     The image-pixel Y is converted, based on depth information, into a right-eye-image-pixel R and a left-eye-image-pixel L. An image-pixel Y′ is an image-pixel that can be seen that of a stereoscopic image in the direction of the front of the screen  11  after the plane image is converted into the stereoscopic image. As illustrated in  FIG. 6 , the image-pixel Y of the plane image can be seen as the image-pixel Y′ located in the direction of the front of the screen  11  when the stereoscopic image is viewed. 
     The distance L and the angle A illustrated in  FIG. 4  are measured by the distance/angle measurement module  24 . As illustrated in  FIG. 6 , the image-pixel Y is located at a position at a distance N from a normal  54  to the surface of the screen  11  at the substantial center. The distance Ls is a distance from the stereoscopic image eyeglasses  2  to a foot of a perpendicular to the screen  11 . The distance Ls is calculated by the parameter generator  27  from the distance L and the angle A. An angle C of the stereoscopic image eyeglasses  2  with respect to the normal to the surface of the screen at the image-pixel Y is calculated by the parameter generator  27  from the distance L, the angle A, and the distance N. 
     A projection amount Lf in the front of the screen  11  is calculated according to depth information corresponding to the image-pixel Y and the depth parameter Pf. The depth parameter Pf is a parameter for adjusting a projection amount in the direction of the front of the screen  11 . The depth parameter Pf for adjusting an optimal projection amount is set according to the value of the distance Ls. Thus, the value of the optimal projection amount Lf is adjusted. The depth parameter Pf is a predetermined parameter determined by the value of the distance Ls. The depth parameter Pf is calculated after the distance Ls is calculated, based on a predetermined formula, by the parameter generator  27 . The calculated depth parameter Pf is output to the 3D image converter  8 . The 3D image converter  8  calculates the projection amount Lf according to the depth information corresponding to the image-pixel Y and the depth parameter Pf. Thus, the 3D image converter  8  can convert a plane image into a stereoscopic image to have an optimal effect according to the user&#39;s position. Alternatively, the relationship between the distance Ls and the depth parameter Pf may be stored in the ROM  18  or the flash memory  19  in the table format. In addition, after the distance Ls is calculated, the depth parameter Pf may be read from the table. 
     The magnitude of the parallax vector Vd corresponding to the line-segment between the right-eye-image-pixel R and the left-eye-image-pixel L is “d′”. The magnitude d′ of the parallax vector is calculated from the distance D between both eyes of the user, the distance Ls, and the projection amount Lf. The relation among the magnitude d′ of the parallax vector Vd′, the magnitude d′R of a parallax vector Vd′R corresponding to the generated image-pixel R, and the magnitude d′L of a parallax vector Vd′L corresponding to the generated image-pixel L is expressed by the following equation: 
     
       
      
       d′=d′R+d′L.  
      
     
     The parameter generator  27  outputs a parallax parameter Ppf for adjusting, according to an angle C, a rate of the magnitude of the parallax vector corresponding to the right-eye-image-pixel R and that of the parallax vector corresponding to the left-eye-image-pixel L. The parallax parameter Ppf is a predetermined parameter determined by the magnitude of the angle C. The parallax parameter Ppf is calculated after the angle C is calculated, based on the predetermined formula, by the parameter generator  27 . The calculated parallax parameter Ppf is output to the 3D image converter  8 . When calculating the magnitude d′R of the parallax vector Vd′R and that d′L of the parallax vector Vd′L, the 3D image converter  8  adjusts the rate between the magnitudes d′R and d′L, using the parallax parameter Ppf. Thus, the plane image can be converted into a stereoscopic image to have an optimal image. Alternatively, the relationship between the angle C and the parallax parameter Ppf may be stored in the ROM  18  or the flash memory  19  in the table format. In addition, after the angle C is calculated, the parallax parameter Ppf may be read from the table. 
       FIG. 7  illustrates an operation procedure for transmitting wearing information from the stereoscopic image eyeglasses  2 . In step S 11 , the sensor controller  31   a  of the controller  31  monitors change of an output signal of the wear sensor  33 . Thus, the sensor controller  31   a  monitors whether the user wears or removes the stereoscopic image eyeglasses  2 . When the user turns on the power switch  51  of the stereoscopic image eyeglasses  2 , the sensor controller  31   a  starts monitoring an output signal of the wear sensor  33 . 
     In step S 12 , the sensor controller  31   a  determines whether a wearing/removing state of the user changes. If the wearing/removing state changes, the procedure proceeds to step S 13 . If the wearing/removing state doesn&#39;t change, the procedure returns to step S 11  in which the sensor controller  31   a  continues to monitor. In step S 13 , the sensor controller  31   a  determines whether the user is brought into the wearing state. If the user wears the stereoscopic image eyeglasses  2 , the procedure proceeds to step S 14 . If the user removes the stereoscopic image eyeglasses  2 , the procedure proceeds to step S 15 . 
     In step S 14 , the communication controller  31   c  transmits the wearing information  36  to the stereoscopic image display apparatus  1  via the transmitting/receiving device  35 . Then, the stereoscopic image eyeglasses  2  are again brought into a mode in which the wearing/removing state is monitored. In step S 15 , the communication controller  31   c  transmits the non-wearing information  37  to the stereoscopic image display apparatus  1  via the transmitting/receiving device  35 . Then, the stereoscopic image eyeglasses  2  are again brought into a mode in which the wearing/removing state is monitored. When the user turns off the power switch  51  of the stereoscopic image eyeglasses  2 , a sequence of operations is finished. 
       FIG. 8  illustrates an operation procedure for switching between a plane image and a stereoscopic image according to the user&#39;s wearing state of the stereoscopic image eyeglasses  2 . When the user wears the stereoscopic image eyeglasses  2 , a stereoscopic image is displayed. When the user removes the stereoscopic image eyeglasses  2 , a displayed image is changed to a plane image. Accordingly, when the user wears the stereoscopic image eyeglasses  2 , the stereoscopic image display apparatus  1  converts, if an original image signal represents a plane image, the plane image into a stereoscopic image. If the original image signal represents a stereoscopic image, the stereoscopic image display apparatus  1  displays the stereoscopic image on the screen  11  as it is. When the user removes the stereoscopic image eyeglasses  2 , the stereoscopic image display apparatus  1  displays, if the original image signal represents a plane image, the plane image as it is. If the original image signal represents a stereoscopic image, the stereoscopic image display apparatus  1  converts the stereoscopic image into a plane image and displays the plane image on the screen  11 . 
     In step S 21 , the controller  15  of the stereoscopic image display apparatus  1  determines whether the controller  15  receives the wearing information  36  or the non-wearing information  37 . The controller  15  can make such determination by receiving such information from the communication controller  22 . If the controller  15  receives such information, the procedure proceeds to step S 22 . 
     In step S 22 , the controller  15  determines whether the received information is the wearing information  36  or the non-wearing information  37 . If the received information is the wearing information  36 , the procedure proceeds to step S 23 . If the received information is the non-wearing information  37 , the procedure proceeds to step S 28 . 
     In step S 23 , the controller  15  causes the distance/angle measurement module  24  to measure the distance and the angle of the stereoscopic image eyeglasses  2 . The distance/angle measurement module  24  measures the distance of the stereoscopic image eyeglasses  2  from the substantial center of the screen  11  and the angle of the stereoscopic image eyeglasses  2  with respect to the normal to the surface of the screen  11  at the substantial center. Information representing the detected distance and the detected angle is output to the controller  15  and stored in the RAM  17 . 
     The measurement of the distance and angle of the stereoscopic image eyeglasses  2  is performed not only after the stereoscopic image eyeglasses  2  transmits the wearing information  36  to the stereoscopic image display apparatus  1  but at another timing. For example, the distance and the angle of the stereoscopic image eyeglasses  2  may be measured at predetermined time intervals. This is because the user can moves among viewing-positions while the user wears the stereoscopic image eyeglasses  2 . Even in this case, conversion according to the user&#39;s position can be performed by measuring the position of the stereoscopic image eyeglasses  2  at predetermined time intervals. The position of the stereoscopic image eyeglasses  2  can be measured regardless of whether the user wears the stereoscopic image eyeglasses  2 . 
     In step S 24 , the controller  15  determines whether an image represented by an image signal output from the signal processor  7  is a plane image or a stereoscopic image. If the image represented by the output image signal is a stereoscopic image, the procedure proceeds to step S 27 . If the image represented by the output image signal is a plane image, the procedure proceeds to step S 25 . 
     In step S 25 , the controller  15  activates the 3D image converter  8 . In addition, the controller  15  inputs a signal representing a plane image, which is output from the signal processor  7 , to the 3D image converter  8 . In step S 26 , the parameter generator  27  generates, based on the distance L and the angle A measured by the distance/angle measurement module  24 , the depth parameter and the parallax parameter used when the 3D image converter  8  converts a plane image to a stereoscopic image. The controller  15  outputs to the 3D image converter  8  the depth parameter and the parallax parameter output by the parameter generator  27 . By using the parameters, the 3D image converter  8  can convert a plane image into a stereoscopic image to have an optimal effect according to the user&#39;s position. 
     In step S 27 , the controller  15  puts the image processor  9  into a mode in which the stereoscopic image display apparatus  1  displays a stereoscopic image, so that a stereoscopic image is displayed on the screen  11 . If an original image signal output from the signal processor  7  represents a stereoscopic image, the image processor  9  displays the stereoscopic image as it is. That is, a stereoscopic image output from the 3D image converter  8  is displayed as a stereoscopic image. 
     In step S 28 , the controller  15  determines whether the 3D image converter  8  is operating. If the 3D image converter  8  is operating, the procedure proceeds to step S 29  in which an operation of the 3D image converter  8  is stopped. If the 3D image converter  8  is not operating, the procedure proceeds to step S 30 . 
     In step S 30 , the controller  15  puts the image processor  9  into a mode in which a plane image is displayed. If an original image signal output from the signal processor  7  represents a plane image, the image processor  9  displays the plane image as a plane image. If an original image signal output from the signal processor  7  represents a stereoscopic image, the image processor  9  changes the stereoscopic image to a plane image and displays the plane image as it is. If the original image is, e.g., a stereoscopic image for stereoscopically displaying an image according to the side-by-side method, the stereoscopic image can be converted into a plane image by expanding only one of a right-eye-image and a left-eye-image to the size of the display screen and displaying the stereoscopic image. 
     As described above, the procedure for switching therebetween begins at a time at which the user wears or removes the stereoscopic image eyeglasses  2 . When the user wears the stereoscopic image eyeglasses  2 , the stereoscopic image display apparatus  1  converts, if an original image signal represents a plane image, the plane image into a stereoscopic image. If the original image signal represents a stereoscopic image, the stereoscopic image is displayed on the screen as it is. When the user removes the stereoscopic image eyeglasses  2 , the stereoscopic image display apparatus  1  displays, if the original image signal represents a plane image, the plane image as it is. If the original image signal represents a stereoscopic image, the stereoscopic image display apparatus  1  converts the stereoscopic image into a plane image and displays the plane image on the screen. In the conversion from a plane image to a stereoscopic image at the 3D image converter  8 , the distance and the angle of the stereoscopic image eyeglasses  2  with respect to the stereoscopic image display apparatus  1  are measured. Depth parameters Pd and Pf, and the parallax parameters Ppd and Pdf are output from measurement data by the parameter generator  27 . According to such parameters, the values of the depth amount Ld, the projection amount Lf, the magnitudes of the parallax vectors VdR, Vd′R at the generation of an image-pixel R, and the magnitudes of the parallax vectors VdL and Vd′L at the generation of the image-pixel L are adjusted. Thus, the 3D image converter  8  can convert a plane image into a stereoscopic image to have an optimal effect. 
     Thus, when the user wears the stereoscopic image eyeglasses, a plane image can automatically be converted into a stereoscopic image. Further, a plane image can be converted into a stereoscopic image to have an optimal effect according to the user&#39;s position. 
     The invention is not limited to the above embodiment, and can be embodied by changing the components thereof without departing the scope of the invention. For example, plural components of above embodiment may be appropriately combined, and several components may be deleted from all the components.