Abstract:
A stereo image display device includes an image display unit for displaying a parallactic image having a right-eye image and a left-eye image on a display plane, a parallactic image selecting unit for making only the right-eye image of the parallactic image reach the right eye of a viewer and making only the left-eye image of the parallactic image reach the left eye of the viewer to thereby make the viewer view a stereo image, an eye fatigue degree detecting unit for detecting the eye fatigue degree of the viewer, and an eye fatigue relaxation processing unit for carrying out eye fatigue relaxation processing for relaxing the eye fatigue of the viewer.

Description:
BACKGROUND 
   1. Technical Field 
   The present invention relates to stereo image display device and method. 
   2. Related Art 
   An image viewed through the right eye of a human and an image viewed through the left eye of the human are combine with each other in the brain of the human, whereby the human recognizes the viewed object as a stereo image. This is possible because the same object is viewed at different angles (i.e., from different positions) by the right and left eyes and thus the image viewed by the right eye and the image viewed by the left eye are slightly different from each other. 
   Therefore, in order to make a viewer recognize a two-dimensionally displayed image as a stereo image, a parallactic image comprising an image to be viewed by the right eye (right-eye image) and an image to be viewed by the left eye (left-eye image) is displayed on the two-dimensional plane, and only the right-eye image is made to reach the right eye of the viewer while only the left-eye image is made to reach the left eye of the viewer, whereby the viewer can recognize the two-dimensional parallactic image as a stereo image. 
   Specifically, a stereo image display device is equipped with an image display unit for displaying a parallactic image on a display plane, and a parallactic image selecting unit for making only the right-eye image of the parallactic image reach the right eye of a viewer and making only the left-eye image of the parallactic image reach the left eye of the viewer. A pair of glasses may be used as the parallactic image selecting unit, for example. The viewer puts on the glasses concerned to thereby recognize a stereo image. As the glasses may be generally used polarized glasses having right-eye and left-eye transmissible portions that transmit therethrough polarized light beams of different polarization directions, or liquid crystal shutter glasses having right-eye and left-eye transmissible portions that are alternately varied between a transmissible state and a non-transmissible state. In the case of use of the polarized glasses, the right-eye image of the parallactic image is set to be based on the polarized light having the polarization direction along which the right-eye transmissible portion transmits light, and the left-eye image of the parallactic image is set to be based on the polarized light having the polarization direction along which the left-eye transmissible portion transmits light, whereby only the right-eye image is made to reach the right eye of the viewer and only the left-eye image is made to reach the left eye of the viewer. Furthermore, in the case of use of the liquid crystal shutter glasses, the right-eye image of the parallactic image is displayed under the state that the right-eye transmissible portion is set to the transmissible state and the left-eye transmissible portion is set to the non-transmissible state, and the left-eye image of the parallactic image is displayed under the state that the right-eye is set to the non-transmissible state and the left-eye transmissible portion is set to the transmissible state, whereby only the right-eye image is made to reach the right eye of the viewer and only the left-eye image is made to reach the left eye of the viewer. 
   Furthermore, there is known a stereo image display device using a lenticular lens as a parallactic image selecting unit. Specifically, a lenticular lens is disposed on a display plane so that only the right-eye image of a parallactic image displayed on the display plane is guided to the right eye of a viewer, and only the left-eye image of the parallactic image displayed on the display plane is guided to the left eye of the viewer. 
   The stereo image display devices described above are disclosed in JP-A-63-70284 or JP-A-63-227193, for example. 
   In the stereo image display devices as described above, a viewer is made to view a stereo image which does not actually exist, and thus the viewer&#39;s convergence and the focal point are not coincident with each other, so that the viewer feels uncomfortable and suffers eye fatigue. 
   Particularly, when the viewer views a stereo image for a long time, a large load is imposed on the viewer&#39;s eyes and the eye fatigue is intensified. 
   SUMMARY 
   An advantage of some aspects of the invention is to reduce eye fatigue of a viewer when the viewer views a stereo image. 
   In order to attain the above object, according to a first aspect of the invention, a stereo image display device including an image display unit for displaying a parallactic image having a right-eye image and a left-eye image on a display plane, a parallactic image selecting unit for making only the right-eye image of the parallactic image reach the right eye of a viewer and making only the left-eye image of the parallactic image reach the left eye of the viewer to thereby make the viewer view a stereo image, an eye fatigue degree detecting unit for detecting the eye fatigue degree of the viewer, and an eye fatigue relaxation processing unit for carrying out eye fatigue relaxation processing for relaxing the eye fatigue of the viewer. 
   According to the stereo image display device of the first aspect of the invention, the eye fatigue degree of the viewer is detected by the eye fatigue degree detecting unit, and the eye fatigue relaxation processing is carried out in accordance with the detection result by the eye fatigue relaxation processing unit. 
   Therefore, even when the viewer views a stereo image for a long time, the load imposed on the viewer&#39;s eyes can be reduced as compared with the stereo image display devices of the related art. Accordingly, the stereo image display device of the first aspect of the invention can reduce the eye fatigue of the viewer when the viewer views a stereo image. 
   In the above stereo image display device, it is preferable that the eye fatigue degree detecting unit comprises plural image pickup units for picking up images of the viewer, a calculating unit for calculating the distance between the viewer&#39;s irises and the distance from the viewer to the display plane on the basis of the image pickup results of the image pickup units, a digitizing unit for digitizing an eye fatigue degree of the viewer per unit time in accordance with the distance between the viewer&#39;s irises and the distance from the viewer to the display plane, and an integrating unit for integrating the digitized eye fatigue degree of the viewer per unit time and outputting a start signal of the eye fatigue relaxation processing as the detection result when the integrating result exceeds a predetermined threshold value. 
   In the stereo image display device described above, it is preferable that the eye fatigue relaxation processing unit may carry out as the eye fatigue relaxation processing the processing of displacing the stereo image viewed by the viewer in a vertical direction to the display plane. 
   With the above construction, the stereo image is displaced in the vertical direction to the display plane in the eye fatigue relaxation processing, and thus the eye convergence of the viewer can be varied in accordance with the displacement of the stereo image. That is, the viewer can make an eye stretch in the eye fatigue relaxation processing, so that the viewer&#39;s eye fatigue when the viewer views the stereo image can be reduced. 
   Furthermore, in the stereo image display device described above, it is preferable that the eye fatigue relaxing unit is equipped with a display plane displacing unit for displaying the display plane in the depth direction with respect to the viewer, and the eye fatigue relaxation processing contains the processing of displaying the display plane. 
   With the above construction, the display plane is displaced in the depth direction with respect to the viewer in the eye fatigue relaxation processing, and in connection with this displacement, the focal point of the eyes of the viewer can be varied. That is, the eyes of the viewer can be stretched in the eye fatigue relaxation processing, and the eye fatigue of the viewer can be reduced when a stereo image is viewed. 
   It is preferable that when the display plane is displaced, the display plane is displaced without varying the size of the stereo image viewed by the viewer. Accordingly, the eye fatigue of the viewer when the viewer views a stereo image can be reduced without varying the size of the stereo image viewed by the viewer. 
   Furthermore, in the stereo display image described above, it is preferable that the eye fatigue relaxing unit emit an alarm to the viewer in the eye fatigue relaxation processing. 
   With the above construction, an alarm is emitted to the viewer as the eye fatigue relaxation processing. Therefore, the moderation of the eye fatigue can be promoted to the viewer although it is not directly carried out. 
   Next, according to another aspect of the present invention, a stereo image display method comprises: displaying a parallactic image comprising a right-eye image and a left-eye image on a display plane; making only the right-eye image of the parallactic image to the right eye of a viewer while making only the left-eye image of the parallactic image to the left eye of the viewer, thereby making the viewer view a stereo image; and detecting an eye fatigue degree of the viewer and relaxing the eye fatigue of the viewer in accordance with the detection result to carry out eye fatigue relaxation processing. 
   According to the stereo image display method described above, the eye fatigue degree of the viewer is detected, and the eye fatigue relaxation processing is carried out in accordance with the detection result. 
   Therefore, even when the viewer views a stereo image for a long time, the load imposed on the eyes of the viewer can be reduced as compared with the stereo image display device of the related art. Accordingly, according to the stereo image display method of the aspect of the invention, the eye fatigue of the viewer when the viewer views a stereo image can be reduced. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
       FIG. 1  is a schematic diagram showing a stereo image display device according to a first embodiment of the invention. 
       FIG. 2  is a diagram showing the operation of the stereo image display device of the first embodiment of the invention. 
       FIG. 3  is a diagram showing the operation of the stereo image display device of the first embodiment of the invention. 
       FIG. 4  is a diagram showing the operation of the stereo image display device of the first embodiment of the invention. 
       FIG. 5  is a diagram showing the operation of the stereo image display device of the first embodiment of the invention. 
       FIG. 6  is a schematic diagram showing a stereo image display device according to a second embodiment of the invention. 
       FIG. 7  is a schematic diagram showing a stereo image display device according to a third embodiment of the invention. 
   

   DESCRIPTION OF EXEMPLARY EMBODIMENTS 
   Embodiments of stereo image display device and method according to the invention will be described hereunder with reference to the accompanying drawings. In the drawings, the contraction scale of each element is properly changed so that each element is visually recognizable. 
   First Embodiment 
     FIG. 1  is a schematic diagram showing the construction of a stereo image display device S 1  of a first embodiment. As shown in  FIG. 1 , the stereo image display device S 1  of this embodiment comprises an image display device  1  (image display unit) and glasses  2  (parallactic image selecting unit). 
   The image display device  1  displays a parallactic image comprising an image for a right eye (right-eye image) and an image for a left eye (left-eye image). This image display device  1  comprises a calculator  11  (calculating unit), a digitizer  12  (digitizing unit), an integrator  13  (integrating unit), an eye fatigue relaxation processor  14  (eye fatigue relaxation processing unit), a parallactic image processor  15 , a left-eye image projector  16 , a right-eye image projector  17 , a first image pickup device  18  (image pickup unit), a second image pickup device  19  (image pickup unit) and a screen  20  (display plane). The first image pickup device  18 , the second image pickup device  19  and the screen  20  are disposed so as to face a viewer (the glasses  2 ). 
   The first image pickup device  18  and the second image pickup device  19  are arranged in the horizontal direction, and it picks up the image of the viewer and outputs the image pickup result. By picking up the image of the viewer with the two image pickup devices thus arranged horizontally, the images of the viewer which are picked up by the respective image pickup devices  18 ,  19  are slightly different from each other. 
   On the basis of the image pickup result of the first image pickup device  18  and the second image pickup device  19 , the calculator  11  calculates the distance between the viewer&#39;s irises on the image pickup result of the first image pickup device  18  and the second image pickup device  19  and the distance from the viewer to the screen  20 . Here, as described above, the first and second image pickup devices  18  and  19  are arranged so as to be slightly displaced from each other in the horizontal direction, and thus the calculator  11  can easily calculate the distance from the viewer to the screen  20  on the basis of the displacement amount of the image pickup result of the image pickup devices  18 ,  19 . Furthermore, the distance between the viewer&#39;s irises can be easily achieved by actually measuring the corresponding distance on the image pickup result of the first image pickup device  18  or/and the second image pickup device  19 . 
   The digitizer  12  digitizes the eye fatigue degree per unit time in accordance with the calculation result of the calculator  11 , that is, the distance between the viewer&#39;s irises and the distance from the viewer to the screen  20 . 
   For example, the distance to the gaze point is uniquely calculated on the basis of the distance between the viewer&#39;s irises on the image pickup result of the first image pickup device  18  and the second image pickup device  19  and the distance from the viewer to the screen  20 . Accordingly, the digitizer  12  stores the relationship of the distance between the viewer&#39;s irises on the image pickup result of the first image pickup device  18  and the second image pickup device  19  and the distance from the viewer to the screen  20  and the gaze point distance in advance and extracts a prescribed gaze point distance from the calculation result of the calculator  11 . The gaze point distance means the distance from the viewer to the stereo image viewed by the viewer, that is, the distance from the viewer to the position at which the viewer gazes. The digitizer  12  stores the eye fatigue degree corresponding to the inverse number of each gaze point distance in the form of a numerical value in advance, and on the basis of the calculation result of the calculator  11 , the digitizer  12  can calculate the eye fatigue degree of the viewer per unit time as a numerical value (i.e., digitize the eye fatigue degree). 
   The integrator  13  integrates the digitized viewer&#39;s eye fatigue per unit time, and outputs a start signal representing the start of the eye fatigue relaxation processing to the eye fatigue relaxation processor  14  when the integration result exceeds a predetermined threshold value. 
   In the stereo image display device S 1  of this embodiment, the eye fatigue detecting unit comprises the first image pickup device  18 , the second image pickup device  19 , the calculator  11 , the digitizer  12  and the integrator  13 . That is, in the stereo image display of this embodiment, the eye fatigue degree of the viewer is detected by the first image pickup device  18 , the second image pickup device  19 , the calculator  11 , the digitizer  12  and the integrator  13  constituting the eye fatigue detecting unit, and when the viewer&#39;s eye fatigue degree exceeds the predetermined threshold value, the start signal representing the start of the eye fatigue relaxation processing is output as a detection signal to the eye fatigue relaxation processor  14 . 
   The eye fatigue relaxation processor  14  carries out the eye fatigue relaxation processing for relaxing the eye fatigue of the viewer in accordance with the start signal input from the integrator  13 , that is, the detection result of the eye fatigue detecting unit. In this embodiment, the eye fatigue relaxation processing is the processing of displacing the stereo image viewed by the viewer in the vertical direction to the screen  20 . Specifically, the signal for the eye fatigue relaxation processing is output to the parallactic image processor  15 . On the basis of this signal, the signal of the parallactic image is converted in the parallactic image processor  15  so that the stereo image is displaced in the vertical direction to the screen  20 . When the signal is input from the eye fatigue relaxation processor  14  to the parallactic image processor  15 , the parallactic image processor  15  converts the signal of a parallactic image input from the external or the signal of a parallactic image stored in advance, and then inputs the parallactic image signal thus converted to the left-eye image projector  16  and the right-eye image projector  17 . However, when no signal is input from the eye fatigue relaxation processor  14 , the parallactic image processor  15  does not convert the signal of the parallactic image input from the external or the signal of the parallactic image stored in advance, and directly inputs the signal concerned to the left-eye image projector  16  and the right-eye image projector  17 . 
   The left-eye image projector  16  is supplied with the signal of the left-eye image out of the parallactic image signal from the parallactic image processor  15 , and projects the left-eye image on the basis of this signal to display the left-eye image on the screen  20 . 
   Furthermore, the right-eye image projector  17  is supplied with the signal of the right-eye image out of the parallactic image signal from the parallactic image processor  15 , and projects the right-eye image on the basis of this signal to display the right-eye image on the screen  20 . 
   The three-plate type liquid crystal projector using three liquid crystal light valves as optical modulators may be used as the left-eye image projector  16  and the right-eye image projector  17 . Furthermore, a single-plate type liquid crystal projector using a liquid crystal light valve as an optical modulator or a projector using a minute mirror array device may be used. 
   As shown in  FIG. 1 , circular polarization plates  161  and  171  are disposed at the subsequent stages of the left-eye and right-eye image projectors  16  and  17 , respectively. These circular polarization plates  161  and  171  polarize transmitted light in different rotational directions. In the stereo image display device S 1  of the first embodiment, the circular polarization plate  16  disposed at the subsequent stage to the left-eye image projector  16  polarizes the transmitted light to polarized light in a counterclockwise direction when viewed in the direction from the image display device  1  to the glasses  2 , and the circular polarization plate  171  disposed at the subsequent stage to the right-eye image projector  17  polarizes the transmitted light to polarized light in a clockwise direction when viewed in the direction from the image display device  1  to the glasses  2 . 
   The viewer puts on the glasses  2 , and the glasses  2  have a right-eye transmissible portion  21  for transmitting only image light of the right-eye image out of the parallactic image displayed on the screen  20 , and a left-eye transmissible portion  22  for transmitting only image light of the left-eye image out of the parallactic image displayed on the screen  20 . The right-eye transmissible portion  21  and the left-eye transmissible portion  22  are disposed so that the right-eye transmissible portion  21  is disposed in front of the right eye of the viewer and the left-eye transmissible portion  22  is disposed in front of the left eye of the viewer when the viewer puts on the glasses  2 . 
   Specifically, the glasses  2  of the stereo image display device S 1  of the first embodiment are circular polarization glasses in which the right-eye transmissible portion  21  and the left-eye transmissible portion  22  transmit circularly-polarized light beams different in rotational direction respectively. In the first embodiment, when viewed in the direction from the image display device  1  to the glasses  2 , the right-eye transmissible portion  21  transmits only the circularly-polarized light in the clockwise direction, and the left-eye transmissible portion  22  transmits only the circularly-polarized light in the counterclockwise direction. 
   The rotational direction of the circularly-polarized light is varied by reflection. Therefore, when the image light beams projected from the left-eye image projector  16  and the right-eye image projector  17  are reflected in the image display device  1 , the rotational direction of the polarized light transmitted through each of the right-eye transmissible portion  21  and the left-eye transmissible portion  22  is varied in accordance with the reflection frequency. That is, the right-eye transmissible portion  21  and the left-eye transmissible portion  22  are selected so that the image light emitted from the left-eye image projector  16  reaches only the left eye and the image light emitted from the right-eye image projector  17  reaches only the right eye. 
   Next, the operation of the stereo image display device S 1  thus constructed (stereo image display method) of this embodiment will be described. 
   First, under a normal state, that is, when no start signal is input to the eye fatigue relaxation processor  14  and thus no signal is input from the eye fatigue relaxation processor  14  to the parallactic image processor  15 , the signal of the parallactic image input from the external to the parallactic image processor  15  or the signal of the parallactic image stored in the parallactic image processor  15  in advance is divided into the left-eye image signal and the right-eye image signal, and the left-eye and right-eye image signals thus achieved are input to the left-eye image processor and the right-eye image projector  17 , respectively. 
   As a result, the left-eye image is projected from the left-eye image projector  16  onto the screen  20  and the right-eye image is projected from the right-eye image projector  17  onto the screen  20 . 
   Here, the image light of the left-eye image projected from the left-eye image projector  16  onto the screen  20  is polarized to polarized light in the counterclockwise direction through the circular polarization plate  161  when viewed in the direction from the image display device  1  to the glasses  2 , and the image light of the right-eye image projected from the right-eye image projector  17  onto the screen  20  is polarized to polarized light in the clockwise direction through the circular polarization plate  171  when viewed in the direction from the image display device  1  to the glasses  2 . 
   In the stereo image display device S 1  of this embodiment, the right-eye transmissible portion  21  of the glasses  2  is constructed as a circular polarization plate for transmitting only circularly-polarized light in the clockwise direction when viewed in the direction from the image display device  1  to the glasses  2 , and the left-eye transmissible portion  21  of the glasses  2  is constructed as a circular polarization plate for transmitting only circularly-polarized light in the counterclockwise direction when viewed in the direction from the image display device  1  to the glasses  2 . Therefore, the right-eye image reaches only the right eye of the viewer, and the left-eye image reaches only the left eye of the viewer. As a result, the brain of the viewer combines the right-eye image and the left-eye image, and the viewer views the stereo image. 
   In the stereo image display device S 1  of this embodiment, when the viewer views the stereo image, the image of the viewer is picked up by the first image pickup device  18  and the second image pickup device  19 . This image pickup result is input to the calculator  11 . In the calculator  11 , the distance between the viewer&#39;s irises on the image pickup result of the first image pickup device  18  and the second image pickup device  19  and the distance from the viewer to the screen  20  on the image pickup result are calculated. When the viewer views the stereo image, the viewer puts on the glasses  2 . In this case, the right-eye transmissible portion  21  and the left-eye transmissible portion  22  are constructed by polarization plates. Therefore, the distance between the viewer&#39;s irises can be checked on the image pickup result of the first image pickup device  18  and the second image pickup device  19 . 
   Subsequently, the calculation result of the calculator  11 , that is, the distance between the viewer&#39;s irises on the image pickup result and the distance from the viewer to the screen  20  is input to the digitizer  12 . The digitizer  12  extracts the gaze point distance from the relationship of the distance between the viewer&#39;s irises on the image pickup result and the distance from the viewer to the screen  20  stored in advance and the gaze point distance on the basis of the input calculation result. For example, when the distance from the viewer to the screen  20  which is based on the input calculation result is equal to 1 m and the relationship between the distance between the viewer&#39;s irises on the image pickup result for the distance of 1 m from the viewer to the screen  20  and the gaze point distance is shown in a graph of  FIG. 2 , if the distance between the viewer&#39;s irises on the image pickup result of the input calculation result is equal to 6.2 cm, the calculator  11  calculates the gaze point distance as 26 cm. Thereafter, the digitizer  12  extracts the eye fatigue degree corresponding to the inverse number of the gaze point distance which is digitized and stored in advance. Here, the inverse number of the gaze point distance is used because the relationship between the gaze point distance and the eye fatigue degree is an inversely proportional relationship, that is, the eye fatigue degree is increased as the gaze point distance approaches to zero. 
   As described above, the eye fatigue degree of the viewer is digitized on the basis of the calculation result of the calculator  11  in the digitizer  12 . 
   The viewer&#39;s eye fatigue degree thus digitized is input to the integrator  13 . The integrator  13  integrates the viewer&#39;s eye fatigue degree thus digitized and input and outputs the start signal to the eye fatigue relaxation processor  14  when the result exceeds a predetermined threshold value. 
   For example, the inverse number of the gaze point distance as shown in  FIG. 3  varies with the time. That is, when a viewer views a stereo image whose pop amount from the screen  20  varies with the time, the integrator  13  integrates the eye fatigue degree with the time lapse as shown in  FIG. 4 , and outputs the start signal when the integration result exceeds a threshold value E. 
   The start signal output from the integrator  13  is input to the eye fatigue degree relaxing processor  14 . The eye fatigue relaxation processor  14  carries out the eye fatigue relaxation processing in response to the start signal thus input. Specifically, in the stereo image display device S 1  of this embodiment, as shown in  FIG. 5 , the stereo image viewed by the viewer is displaced in the vertical direction to the display plane of the screen  20 . More specifically, the signal for converting the parallactic image signal is output to the parallactic image processor  15  so that the stereo image viewed by the viewer is displaced in the vertical direction to the display plane of the screen  20 . The parallactic image processor  15  converts the parallactic image signal is converted on the basis of the input signal. 
   As described above, by displaying the stereo image viewed by the viewer in the vertical direction to the display plane of the screen  20 , the convergence angle of the eyes of the viewer is varied, and thus the eye of the viewer is stretched. Accordingly, the eye fatigue of the viewer can be reduced when the viewer views the stereo image. 
   Second Embodiment 
   Next, a second embodiment of the invention will be described. In the following description of the second embodiment, the description of the same portion as the first embodiment is omitted or simplified. 
     FIG. 6  is a schematic diagram showing the construction of a stereo image display device S 2  of the second embodiment. As shown in  FIG. 6 , in the stereo image display device S 2  of the second embodiment, the eye fatigue relaxation processor  14  comprises a screen moving mechanism  141  (display plane displacing unit). 
   The screen moving mechanism  141  moves (displaces) the screen  20  in the depth direction with respect to the viewer. 
   In the stereo image display device S 2  of this embodiment, when the start signal is input to the eye fatigue relaxation processor  14 , the eye fatigue relaxation processor  14  moves the screen  20  in the depth direction with respect to the viewer by the screen moving mechanism  141 . 
   By moving the screen  20  in the depth direction with respect to the viewer as described above, the focal length of the eyes of the viewer and the convergence angle of the eyes of the viewer are varied and the eyes of the viewer are stretched. Accordingly, the eye fatigue of the viewer when the viewer views the stereo image can be reduced. 
   In the stereo image display device S 2  of the second embodiment, it is preferable that the parallactic image signal is converted so that the size of the stereo image viewed by the viewer is not varied when the screen  20  is moved. Specifically, when the screen  20  is far away from the viewer, the right-eye image and the left-eye image are greatly varied, and when the screen  20  approaches to the viewer, the right-eye image and the left-eye image are slightly varied, so that the screen  20  can be moved without varying the size of the stereo image viewed by the viewer. In this case, the convergence angle of the eyes of the viewer is not varied, however, the focal length of the eyes of the viewer is varied. Therefore, the eyes of the viewer can be likewise stretched, and the eye fatigue of the viewer when the viewer views the stereo image can be reduced. 
   Furthermore, in the stereo image display device S 2  of the second embodiment, when the parallactic image signal is converted so that the size of the stereo image viewed by the viewer is not varied, it is unnecessary to electrically connect the eye fatigue relaxation processor  14  and the parallactic image processor  15  to each other. 
   Third Embodiment 
   Next, a third embodiment of the invention will be described. In the following description of the third embodiment, the description of the same portion as the first embodiment is omitted or simplified. 
     FIG. 7  is a diagram showing the construction of a stereo image display device S 3  of the third embodiment. As shown in  FIG. 7 , in the stereo image display device S 3  of the third embodiment, the eye fatigue relaxation processor  14  is equipped with an alarm portion  142 . 
   When the start signal is input to the eye fatigue relaxation processor  14 , the alarm portion  142  emits an alarm to the viewer. Therefore, an operation of relaxing the eye fatigue (for example, rest or the like) can be promoted to the viewer although it is not direct, so that the eye fatigue of the viewer can be reduced. 
   The alarm portion  142  may be performed by emitting an alarm or displaying an alarm message on the screen  20 . 
   The embodiments of the stereo image display device and method according to the present invention have been described with reference to the drawings, however, the invention is not limited to the above-described embodiments. The shapes, combinations, etc. of the respective constituent elements of the embodiments described above are examples, and various modifications in design, etc. may be modified without departing from the subject matter of the invention. 
   For example, in the above embodiments, the stereo image is moved, the screen  20  is moved or the alarm is emitted as the eye fatigue relaxation processing. However, the invention is not limited to these manners. For example, the processing of displaying an image for relaxing the eye fatigue on the screen  20  or the processing of non-displaying the image itself may be carried out as the eye fatigue relaxation processing. 
   In the above embodiments, the image of the viewer is picked up by the image pickup devices  18  and  19 , the distance between the viewer&#39;s irises on the image pickup result and the distance from the viewer to the screen  20  are calculated on the basis of the image pickup result, and the eye fatigue degree of the viewer is detected on the basis of the calculation result. However, this invention is not limited to this manner. For example, the eye fatigue degree may be detected from other ecological information, or the eye fatigue degree of the viewer may be detected by judging whether the eye fatigue degree of the viewer exceeds a threshold value when a predetermined time elapses. 
   Furthermore, in the above embodiments, the polarized glasses  2  using the circular polarization plates as the right-eye transmissible portion  21  and the left-eye transmissible portion  22  are used as the parallactic image selecting unit. However, this invention is not limited to this mode. For example, liquid crystal glasses using liquid crystal shutters as the right-eye transmissible portion  21  and the left-eye transmissible portion  22  may be used as the parallactic image selecting unit. Furthermore, a lenticular lens or the like disposed on the screen  20  may be used as the parallactic image selecting unit. In this case, it is unnecessary for the viewer to put on the glasses, and thus the image of the irises of the viewer can be more clearly picked up by the image pickup devices  18  and  19 . 
   In the above embodiments, the projector is used as the display unit for display an image. However, the invention is not limited to this mode. For example, various kinds of displays such as a CRT, a liquid crystal display device, a plasma display panel, an organic EL display device, an inorganic EL display device, a field emission device, a surface-conduction electron emitter display, etc. may be used. 
   The entire disclosure of Japanese Patent Application No. 2005-085835, filed Mar. 24, 2005 is expressly incorporated by reference herein.