Patent Publication Number: US-2013234005-A1

Title: Image sensor and optical interaction device using the same thereof

Description:
This application claims the benefit of Taiwan application Serial No. 101107969, filed Mar. 8, 2012, the subject matter of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates in general to an image sensor, and more particularly to an image sensor capable of switching image sources in different directions and an optical interaction device using the same thereof. 
     2. Description of the Related Art 
     Along with the advance in technology, people&#39;s demand for everydayness recording, entertainment and security also increases, and various image sensors are provided in response to the market trends. The generally known image sensors such as camera, video recorder, vehicle recorder and monitor can shoot at a single and specific direction and is unable to shoot at more than two directions at the same time. When there is a need to shoot at two different directions, at least two sets of image sensors are needed or a rotation device is incorporated in the image sensor to rotate the lens. 
     However, two sets of image sensors not only incur more hardware cost and occupy extra space. Due to the restriction of space, sometimes the installation of an extra image sensor is infeasible. The image sensor incorporating a rotation device also needs to consider whether the installation position and space allows the image sensor to rotate at a large angle. Apart from the extra cost of rotation device, the image sensor incorporating a rotation device still has a problem of blind angles in shooting. 
     SUMMARY OF THE INVENTION 
     The invention is directed to an image sensor capable of switching the image sources in different directions to selectively detect images in different directions. The optical interaction device having the said image sensor may selectively receive instructions denoted by the image lights in different directions, and has both two-dimensional and three-dimensional optical interaction functions. 
     According to an embodiment of the present invention, an image sensor for detecting a first and a second image light in different directions is disclosed. The image sensing device comprises a polarization beam splitter, a liquid crystal switch, a polarizer, a lens module and an image sensing device. The polarization beam splitter receives the first and the second image light, and then splits the first image light into a first penetrative light and a first reflective light and splits the second image light into a second penetrative light and a second reflective light. The liquid crystal switch controls the phase delay of the first penetrative light and the second reflective light. The polarizer is disposed on a light emitting side of the liquid switch to control the passage of the first or the second reflective light. The lens module focuses the first or the second reflective light at a focal point. The image sensing device is disposed at the focal point of the lens module to sense the focused first penetrative light or second reflective light. 
     According to another embodiment of the present invention, an image sensor for detecting a first and a second image light in different directions is disclosed. The image sensor comprises an optical splitter, a liquid crystal switch set, a lens module and an image sensing device. The optical splitter receives and transmits the first or the second image light to the first side of the optical splitter. The liquid crystal switch module comprises a first and a second liquid crystal switch. The first liquid crystal switch comprises a liquid crystal layer and a polarizer pair disposed on two opposite sides of the liquid crystal layer, and is disposed at a lateral side of the optical splitter closer to the first image light to control the passage of the first image light. The second liquid crystal switch comprises another liquid crystal layer and another polarizer pair disposed on two opposite sides of the another liquid crystal layer, and is disposed at another lateral side of the optical splitter closer to the second image light to control the passage of the second image light. The lens module focuses the first or the second image light at a focal point located on the first side of the optical splitter. The image sensing device is disposed at the focal point of the lens module to sense the focused first or second image light. 
     According to an alternate embodiment of the present invention, an optical interaction device capable of receiving the image sources in different directions is disclosed. The optical interaction device comprises a display panel and an image sensor disposed on the part of a lateral side of the display panel for detecting a first and a second image light in different directions. The image sensor comprises an optical splitter, a liquid crystal switch module, a lens module, an image sensing device and an image recognition system. The optical splitter receives and transmits a first or a second image light to the first side of the optical splitter. The liquid crystal switch module controls the passage of the first or the second image light. The lens module focuses the first or the second image light at a focal point located on the first side of the optical splitter. The image sensing device is disposed at the focal point of the lens module to sense the focused first or the focused second image light. The image recognition device recognizes an instruction denoted by the focused first image light or another instruction denoted by the focused second image light, wherein the focused first image light and the focused second image light are sensed by the image sensing device. 
     The above and other aspects of the invention will become better understood with regard to the following detailed description of the preferred but non-limiting embodiment(s). The following description is made with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A˜1B  are schematic diagrams of an image sensor according to a first embodiment of the invention; 
         FIGS. 2A˜2B  are schematic diagrams of an image sensor according to a second embodiment of the invention; 
         FIGS. 3A˜3B  are schematic diagrams of an image sensor according to a third embodiment of the invention; 
         FIGS. 4A˜4B  are schematic diagrams of an image sensor according to a fourth embodiment of the invention; 
         FIGS. 5A˜5B  are schematic diagrams of an optical interaction device according to an embodiment of the invention; 
         FIG. 6  is schematic diagrams of a monitoring system according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First Embodiment 
     Referring to  FIGS. 1A and 1B , schematic diagrams of an image sensor  10  according to a first embodiment of the invention are shown. As indicated in  FIG. 1A , the image sensor  10  comprises a polarization beam splitter  100 , a liquid crystal switch  102 , a polarizer  104 , a lens module  106  and an image sensing device  108 . The polarizer  104  is disposed at the light emitting side of the liquid crystal switch  102 . The lens module  106  is disposed between the liquid crystal switch  102  and the image sensing device  108 . In the present embodiment, the polarization beam splitter  100  is realized by such as a polarization beam splitter (PBS), a dual brightness enhancement film dual brightness enhancement film (DBEF), or other reflective multi-layered films having the same function. The image sensing device  108  is realized by such as a complementary metal oxide semiconductor (CMOS) sensor. 
     In the present embodiment, the first image light L 1  and the second image light L 2  are substantially perpendicular to each other. The polarization beam splitter  100  receives the first image light L 1  and the second image light L 2 , and further splits the first image light L 1  into a first penetrative light L P1  and a first reflective light L S1  and splits the second image light L 2  into a second penetrative light L P2  and a second reflective light L S2 . The statement that the first image light L 1  and the second image light L 2  are substantially perpendicular to each other implies that the angle between the first image light L 1  and the second image light L 2  does not need to be exactly equal to 90 degrees and other angles would also do as long as the incident angles of the first image light L 1  and the second image light L 2  fall within an angle range allowing the polarization beam splitter  100  to respectively split the first image light L 1  and the second image light L 2  into separate polarized lights having different phases. 
     It is noted that the polarization beam splitter  100  of  FIGS. 1A and 1B  is realized by a PBS type polarization beam splitter. However, the polarization beam splitter  100  may also be realized by a DBEF type polarization beam splitter as long as the DBEF type polarization beam splitter tilts at an angle to respectively split the first image light L 1  and the second image light L 2  into separate polarized lights having different phases. In the present embodiment, the PBS type polarization beam splitter  100  may function within about 7 degrees of the incident angle at which the incident light enters the PBS type polarization beam splitter  100 ; the DBEF type polarization beam splitter  100  may function within about 30 degrees of the incident angle at which the incident light enters the DBEF type polarization beam splitter  100 . 
     As indicated in  FIGS. 1A and 1B , only the optical paths of the first penetrative light L P1  and the second reflective light L S2  lead to the image sensing device  108 . In the optical path, the liquid crystal switch  102  firstly controls the phase delay of the first penetrative light L P1  and the second reflective light L S2 , and then the polarizer  104  controls the passage of the first penetrative light L P1  or the second reflective light L S2 . The polarizer  104  is for example a polarizer only allows the s-polarized light to pass through. The lens module  106  focuses the first penetrative light L P1  passing through the polarizer  104  or the second reflective light L S2  passing through the polarizer  104  at a focal point F. The image sensing device  108  is disposed at the focal point F of the lens module  106  to sense the focused first penetrative light L P1  or second reflective light L S2 . 
     Firstly, referring to  FIG. 1A , a schematic diagram of applying a voltage V to turn on the liquid crystal switch  102  according to a first embodiment is shown. As indicated in  FIG. 1A , no image sensing devices is disposed in the proceeding direction of the first reflective light L S1  and the second penetrative light L P2 , and the first reflective light L S1  and the second penetrative light L P2  will not be detected. The first penetrative light L P1  and the second reflective light L S2  firstly pass through the enabled liquid crystal switch  102 , which does not delay the phase of the light. For example, both the first penetrative light L P1  and the second penetrative light L P2  are such as a p-polarized light, and both the first reflective light L S1  and the second reflective light L S2  are such as an s-polarized light. The phase difference between the p-polarized light and the s-polarized light is ½λ. Meanwhile, the first penetrative light L P1  after passing through the enabled liquid crystal switch  102  is still a p-polarized light, and the second reflective light L S2  after passing through the enabled liquid crystal switch  102  is still an s-polarized light. Then, the first penetrative light L P1  and the second reflective light L S2  proceed to the polarizer  104  which only allows the s-polarized light to pass through. Eventually, only the second reflective light L S2  passes through the polarizer  104  and is further focused on the image sensing device  108  by the lens  106 . That is, when the liquid crystal switch  102  of  FIG. 1A  is turned on, what is detected by the image sensing device  108  is the image of the second image light L 2  in the incident direction. 
     Next, referring to  FIG. 1B , a schematic diagram of not applying any voltages to the liquid crystal switch  102  so that the liquid crystal switch  102  is turned off according to a first embodiment is shown. Only the differences between and  FIG. 1A  and  FIG. 1B  are disclosed below, and the similarities are no repeated. As indicated in  FIG. 1B , the first penetrative light L P1  and the second reflective light L S2  firstly pass through the disabled liquid crystal switch  102 , which then delays the phase of the light. That is, the first penetrative light L P1  (p-polarized light) after passing through the disabled liquid crystal switch  102  will be delayed as an s-polarized light, and the second reflective light L S2  (s-polarized light) after passing through the disabled liquid crystal switch  102  will be delayed as a p-polarized light. When the delayed first penetrative light L P1  and the second reflective light L S2  proceed to the polarizer  104 , which only allows the s-polarized light to pass through, only the delayed first penetrative light L P1  is able to pass through the polarizer  104  and is further focused on the image sensing device  108  by the lens  106 . That is, when the liquid crystal switch  102  of  FIG. 1B  is turned off, what is detected by the image sensing device  108  is the image of the first image light L 1  in the incident direction. 
     In the first embodiment, by turning on/off the liquid crystal switch  102 , the image sensor  10  selectively detects the image of a first image light L 1  or a second image light L 2 . 
     Second Embodiment 
     Referring to  FIGS. 2A and 2B , schematic diagrams of an image sensor  20  according to a second embodiment of the invention are shown. As indicated in  FIG. 2A , the image sensor  20  comprises a polarization beam splitter  200 , a liquid crystal switch  202 , a polarizer  204 , a lens module  206 , and an image sensing device  208 . The polarizer  204  is disposed at the light emitting side of the liquid crystal switch  202 . The polarization beam splitter  200 , the liquid crystal switch  202 , the polarizer  204  and the image sensing device  208  of the present embodiment are similar to corresponding elements of the first embodiment. Only the differences between the present embodiment and the first embodiment are disclosed, and other similarities are not repeated here. 
     As indicated in  FIGS. 2A and 2B , the lens module  206  comprises a lens  206 - 1  and a lens  206 - 2 . The first image light L 1  firstly passes through a lens  206 - 1  and then proceeds to the polarization beam splitter  200 . The second image light L 2  firstly passes through a lens  206 - 2  and then proceeds to the polarization beam splitter  200 . It is noted that, the lens  206 - 1  is disposed between the light source of the first image light L 1  and the polarization beam splitter  200 , and the lens  206 - 2  is disposed between the light source of the second image light L 2  and the polarization beam splitter  200 . The focal distances of the lens modules  206 - 1  and  206 - 2  are larger than the focal distance of the lens module  106  of the first embodiment, such that the first penetrative light L P1  or the second reflective light L S2  which passes through the lens module  206 - 1  and  206 - 2  may be focused at a focal point F. The image sensing device  208  is disposed at the focal point F of the lens module  206 - 1  and  206 - 2  to sense the focused first penetrative light L P1  or the focused second reflective light L S2 . The polarizer  204  controls the passage of the first penetrative light L P1  or the second reflective light L S2 . 
     Firstly, referring to  FIG. 2A , a schematic diagram of applying a voltage V to turn on the liquid crystal switch  202  according to a second embodiment is shown. In the present embodiment, only the optical paths of the first penetrative light L P1  and the second reflective light L S2  lead to the image sensing device  208 . The first penetrative light L P1  and the second reflective light L S2  firstly pass through the enabled liquid crystal switch  202 , which does not delay the phase of the light. For example, both the first penetrative light L P1  and the second penetrative light L P2  are such as a p-polarized light, and both the first reflective light L S1  and the second reflective light L S2  are such as an s-polarized light. The first penetrative light L P1  after passing through the enabled liquid crystal switch  202  is still a p-polarized light, and the second reflective light L S2  after passing through the enabled liquid crystal switch  202  is still an s-polarized light. Then, the first penetrative light L P1  and the second reflective light L S2  proceed to the polarizer  204  which only allows the s-polarized light to pass through. Eventually, only the second reflective light L S2  is able to pass through the polarizer  204  and is further focused on the image sensing device  208 . That is, when the liquid crystal switch  202  of  FIG. 2A  is turned on, what is detected by the image sensing device  208  is the image of the second image light L 2  in the incident direction. 
     Next, referring to  FIG. 2B , a schematic diagram of not applying any voltages to the liquid crystal switch  202  so that the liquid crystal switch  202  is turned off according to a second embodiment is shown. In the present embodiment, only the optical paths of the first penetrative light L P1  and the second reflective light L S2  lead to the image sensing device  208 . The first penetrative light L P1  and the second reflective light L S2  firstly pass through the disabled liquid crystal switch  202 . It is noted that after the first penetrative light L P1  and the second reflective light L S2  pass through the disabled liquid crystal switch  202 , their phases will be delayed. For example, both the first penetrative light L P1  and the second penetrative light L P2  are such as a p-polarized light, and both the first reflective light L S1  and the second reflective light L S2  are such as an s-polarized light. The first penetrative light L P1  after passing through the disabled liquid crystal switch  202  will be delayed as an s-polarized light, and the second reflective light L S2  after passing through the disabled liquid crystal switch  202  will be delayed as a p-polarized light. Eventually, only the delayed first penetrative light L P1  is able to pass through the polarizer  204  (only the s-polarized light is allowed to pass through) to be focused on the image sensing device  208 . That is, when the liquid crystal switch  202  of  FIG. 2B  is turned off, what is detected by the image sensing device  208  is the image of the first image light L 1  in the incident direction. 
     Third Embodiment 
     Referring to  FIGS. 3A and 3B , schematic diagrams of an image sensor  30  according to a third embodiment of the invention are shown. As indicated in  FIG. 3A , the image sensor  30  comprises a polarization beam splitter  300 , a liquid crystal switch  302 , a polarizer  304 , a lens module  306  and an image sensing device  308 . The polarization beam splitter  300 , the liquid crystal switch  302 , the polarizer  304  and the image sensing device  308  of the present embodiment are similar to corresponding elements of the second embodiment. Only the differences between the present embodiment and the first and the second embodiment are disclosed, and other similarities are not repeated here. 
     As indicated in  FIGS. 3A and 3B , the lens module  306  is disposed between the polarization beam splitter  300  and the liquid crystal switch  302 . The focal distance of the lens module  306  is between that of the lens module  106  of the first embodiment and that of the lens modules  206 - 1  and  206 - 2  of the second embodiment. The first penetrative light L P1  or the second reflective light L S2  which passes through the lens module  306  may be focused at a focal point F. The image sensing device  308  is disposed at the focal point F of the lens module  306  to sense the focused first penetrative light L P1  or the focused second reflective light L S2 . The polarizer  304  controls the passage of the first penetrative light L P1  or the second reflective light L S2 . The polarizer  304  of the present embodiment only allows the s-polarized light to pass through. 
     Firstly, referring to  FIG. 3A , a schematic diagram of applying a voltage V to turn on the liquid crystal switch  302  according to a third embodiment is shown. After the first image light L 1  and the second image light L 2  proceed to the polarization beam splitter  300 , the polarization beam splitter  300  splits the first image light L 1  into a first penetrative light L P1  and a first reflective light L S1 , and splits the second image light L 2  into a second penetrative light L P2  and a second reflective light L S2 . Both the first penetrative light L P1  and the second penetrative light L P2  are such as a p-polarized light, and both the first reflective light L S1  and the second reflective light L S2  are such as an s-polarized light. Only the optical paths of the first penetrative light L P1  and the second reflective light L S2  lead to the image sensing device  308 . The first penetrative light L P1  and the second reflective light L S2  may be focused by the lens module  306 . Before the first penetrative light L P1  and the second reflective light L S2  being focused at the focal point F, the first penetrative light L P1  and the second reflective light L S2  should be selected by the liquid crystal switch  302 . Since the enabled liquid crystal switch  302  does not delay the phase of the light, the first penetrative light L P1  after passing through the enabled liquid crystal switch  302  is still a p-polarized light, and the second reflective light L S2  after passing through the enabled liquid crystal switch  302  is still an s-polarized light. Eventually, only the second reflective light L S2  is able to pass through the polarizer  304  (only the s-polarized light is allowed to pass through) to be focused at the focal point F. That is, when the liquid crystal switch  302  of  FIG. 3A  is turned on, what is detected by the image sensing device  308  is the image of the second image light L 2  in the incident direction. 
     Next, referring to  FIG. 3B , a schematic diagram of not applying any voltages to the liquid crystal switch  302  so that the liquid crystal switch  302  is turned off according to a third embodiment is shown. The similarities between  FIG. 3A  and  FIG. 3B  are not repeated here. It is noted that, after the first penetrative light L P1  and the second reflective light L S2  pass through the disabled liquid crystal switch  302 , their phases will be delayed. That is, when the first penetrative light L P1  (p-polarized light) and the second reflective light L S2  (s-polarized light) proceed to the polarizer  304  which only allows the s-polarized light to pass through, only the delayed first penetrative light L P1  is able to pass through the polarizer  304  to be focused on the image sensing device  308 . That is, when the liquid crystal switch  302  of  FIG. 3B  is turned off, what is detected by the image sensing device  308  is the image of the first image light L 1  in the incident direction. 
     Fourth Embodiment 
     Referring to  FIGS. 4A and 4B , schematic diagrams of an image sensor  40  according to a fourth embodiment of the invention are shown. The image sensor  40  may selectively detect a first image light L 1  or a second image light L 2 , wherein the first image light L 1  and the second image light L 2  are substantially perpendicular to each other. As indicated in  FIG. 4A , the image sensor  40  comprises an optical splitter  400 , a liquid crystal switch module  402 , a lens module  406  and an image sensing device  408 . The lens module  406  and the image sensing device  408  of the present embodiment are similar to corresponding elements of the first embodiment. Only the differences between the present embodiment and the first embodiment are disclosed, and other similarities are not repeated here. 
     In the present embodiment, the optical splitter  400  may be realized by a beam splitter (BS) or a polarization beam splitter similar to the optical splitter  100  of the first embodiment. Details of the polarization beam splitter similar to the optical splitter  100  of the first embodiment are already disclosed above, and the similarities are not repeated here. The BS type beam splitter is a spectroscope which splits a light source into two unequal portions, one is penetrative and the other is reflective. The liquid crystal switch module  402  comprises a liquid crystal switch  402   a  and a liquid crystal switch  402   b . The liquid crystal switch  402   a  is disposed outside the optical splitter  400  and closer to the first image light L 1  to control the passage of the first image light L 1 . The liquid crystal switch  402   b  is disposed outside the optical splitter  400  and closer to the second image light L 2  to control the passage of the second image light L 2 . The lens module  406  is disposed between the optical splitter  400  and the image sensing device  408  for focusing the first image light L 1  passing through the optical splitter  400  or the second image light L 2  passing through the optical splitter  400  at a focal point F. The image sensing device  408  is disposed at the focal point F of the lens module  406  to sense the focused first image light L 1  or the focused second image light L 2 . 
     Firstly, referring to  FIG. 4A , a schematic diagram of applying a voltage V to turn on the liquid crystal switch  402   a  and not applying any voltages to the liquid crystal switch  402   b  so that the liquid crystal switch  402   b  is turned off is shown. As indicated in  FIG. 4A , the liquid crystal switch  402   a  comprises a liquid crystal layer  402   a - 3  and a pair of polarizers  402   a - 1  and  402   a - 2  disposed on two opposite sides of the liquid crystal layer  402   a - 3 . The liquid crystal switch  402   b  comprises another liquid crystal layer  402   b - 3  and another pair of polarizers  402   b - 1  and  402   b - 2  disposed on two opposite sides of the liquid crystal layer  402   b - 3 . Both the polarizer  402   a - 1  and the polarizer  402   b - 2  only allow the s-polarized light to pass through, and both the polarizer  402   a - 2  and the polarizer  402   b - 1  only allow the p-polarized light to pass through. 
     In the present embodiment, when the first image light L 1  proceeds to the liquid crystal switch  402   a , only the first s-polarized light L X1  may pass through the polarizer  402   a - 1  to enter the liquid crystal layer  402   a - 3 . Since the enabled liquid crystal switch  402   a  does not delay the phase of the first s-polarized light L X1 , the first s-polarized light L X1  when proceeding to the polarizer  402   a - 2  cannot pass through the polarizer  402   a - 2 . When the second image light L 2  proceeds to the liquid crystal switch  402   b , only the second p-polarized light L Y2  may pass through the polarizer  402   b - 1  to enter the liquid crystal layer  402   b - 3 . The disabled liquid crystal switch  402   b  delays the phase of the second p-polarized light L Y2 , such that the second p-polarized light L Y2  is converted to a second s-polarized light L Y2′  which may pass through the polarizer  402   b - 2 . 
     Continue to refer to  FIG. 4A . The delayed second s-polarized light L Y2′  after passing through the polarizer  402   b - 2  is reflected to the lens module  406  by the optical splitter  400  and is further focused by the lens module  406  to form an image on the image sensing device  408 . That is, in  FIG. 4A , when the liquid crystal switch  402   a  is turned on and the liquid crystal switch  402   b  is turned off, what is detected by the image sensing device  408  is the image of the second image light L 2  in the incident direction. 
     Referring to  FIG. 4B , a schematic diagram of applying a voltage V to turn on the liquid crystal switch  402   b  and not applying any voltages to the liquid crystal switch  402   a  so that the liquid crystal switch  402   a  is turned off is shown. Only the differences between  FIG. 4A  and  FIG. 4B  are disclosed, and the similarities are no repeated. 
     It is noted that, when the first image light L 1  proceeds to the liquid crystal switch  402   a , only the first s-polarized light L X1  may pass through the polarizer  402   a - 1  to enter the liquid crystal layer  402   a - 3 . The disabled liquid crystal switch  402   a  delays the phase of the first s-polarized light L X1 , such that the first s-polarized light L X1  is converted into a first p-polarized light L X1′ , which may pass through the polarizer  402   a - 2 . When the second image light L 2  proceeds to the liquid crystal switch  402   b , only the second p-polarized light L Y2  may pass through the polarizer  402   b - 1  to enter the liquid crystal layer  402   b - 3 . Since the enabled liquid crystal switch  402   b  does not delay the phase of the second p-polarized light L Y2 , the second p-polarized light L Y2  cannot pass through the polarizer  402   b - 2 . 
     Continue to refer to  FIG. 4B . The delayed first p-polarized light L X1′  after passing through the polarizer  402   a - 2  may penetrate the optical splitter  400  to reach the lens module  406 , and is further focused by the lens module  406  to form an image on the image sensing device  408 . That is, in  FIG. 4B , when the liquid crystal switch  402   a  is turned off and the liquid crystal switch  402   b  is turned on, what is detected by the image sensing device  408  is the image of the first image light L 1  in the incident direction. 
     It is noted that an embodiment in which the lens module  406  is disposed between the optical splitter  400  and the image sensing device  408  is used for description purpose. However, the lens module  406  may comprise two lenses (not illustrated) respectively disposed between the optical splitter  400  and the liquid crystal switch  402   a  and between the optical splitter  400  and the liquid crystal switch  402   b . Alternatively, the two lenses may also be respectively disposed outside the liquid crystal switch  402   a  and closer to the first image light L 1  source, and outside the liquid crystal switch  402   b  and closer to the second image light L 2  source. Other arrangements of the lens module may also do as long as the lens module  406  is disposed in the optical path leading the first image light L 1  and the second image light L 2  to the front of the image sensing device  408  and the image sensing device  408  located at the focal point of the lens module  406 . In the present embodiment, by turning on/off the liquid crystal switch  402   a  and the liquid crystal switch  402   b , the first image light L 1  and the second image light L 2  are selectively transmitted to the image sensing device  408  to form an image. 
     Application of the Image Sensor Disclosed in Above Embodiments: 
     The above embodiments may be used in different types of optical interaction device or image monitoring systems, and a number of applications are disclosed below for exemplification purpose. 
     Referring to  FIG. 5A , a schematic diagram of an optical interaction device  5  according to an embodiment of the invention is shown. The optical interaction device  5  comprises an image sensor  50 - 1 , an image sensor  50 - 2 , and a display panel  52 . The image sensor  50 - 1  and the image sensor  50 - 2  may be realized by any types of image sensors  1040  of the first to the fourth embodiment. As indicated in  FIG. 5A , the image sensor  50 - 1  and the image sensor  50 - 2  are disposed at different positions on a lateral side of the display panel  52 . Preferably, the image sensor  50 - 1  and the image sensor  50 - 2  respectively are disposed at any two non-diagonal positions of the apex angles P 1 -P 4  of the display panel  52 . When the display panel  52  receives a touch signal S, the image sensor  50 - 1  may position the touch signal S as being located on a dummy line f 1 , and the image sensor  50 - 2  may position the touch signal S as being located on a dummy line f 2 . Thus, through the use of two image sensors, the touch signal S is positioned as being at the intersection between the dummy line f 1  and the dummy line f 2 , and the two-dimensional positioning function of the touch panel can thus achieved. In the present embodiment, the touch signal S does not have to contact the display panel  52  as long as the touch signal S may be detected by the image sensor  50 - 1  and the image sensor  50 - 2 . 
     Referring to  FIG. 5B , a schematic diagram of an optical interaction device  5 ′ according to an embodiment of the invention is shown. The optical interaction device  5 ′ comprises an image sensor  50 - 1 , an image sensor  50 - 2 , the display panel  52 ′ and an image recognition device (not illustrated). The image sensor  50 - 1 , the image sensor  50 - 2  and the display panel  52 ′ are similar to corresponding elements of  FIG. 5A , and the similarities are not repeated here. In the present embodiment, when the user sends an instruction (such as a hand gesture or a body movement) in front of the display panel  52 ′, the image sensor  50 - 1  and the image sensor  50 - 2  may obtain the user&#39;s instruction and further transfer the instruction to the image recognition system, which recognizes the instruction denoted by the light signal sensed by the image sensor  50 - 1  and the image sensor  50 - 2 . Therefore, the three-dimensional instruction sent by the user in front of the display panel  52 ′ can thus be recognized by the image sensor  50 - 1  and the image sensor  50 - 2 . 
     In the present embodiment, two image sensors are exemplified for description purpose. However, one image sensor alone may also achieve two-dimensional positioning and three-dimensional instruction recognition for the optical interaction device  5 ′. 
     Referring to  FIG. 6 , a schematic diagram of a monitoring system  6  according to an embodiment of the invention is shown. In the present embodiment, the monitoring system  6  comprises an image sensor  60  and a memory element (not illustrated). The image sensor  60  may be realized by any types of image sensors  1040  of the first to the fourth embodiment. As indicated in  FIG. 6 , the wall W 1  and the wall W 2  are substantially perpendicular to each other. The image sensor  60  is disposed at a corner between the wall W 1  and the wall W 2  to monitor a range crossing direction D 1  (the image of the incident light source substantially parallel to the wall W 1 ) and direction D 2  (the image of the incident light source substantially parallel to the wall W 2 ). In other words, the monitoring system  6  equipped with an image sensor  60  may quickly switch between the image in the direction D 1  and the image in the direction D 2  to instantly monitor the images in the directions D 1  and D 2 . 
     To summarize, the image sensor disclosed in the above embodiments of the invention switch to the image light source in different directions to selectively detect the image light source in different directions. Thus, the optical interaction device using the image sensor provides both the two-dimensional positioning function and the three-dimensional instruction recognition function. Besides, the monitoring system using the image sensor of the above embodiments of the invention may quickly switch and detect the image in different directions, resolves the blind angle problem encountered in conventional monitoring system image, reduces the hardware cost occurring when multiple monitors or rotation devices are required, and is less restricted by the space of installation. 
     While the invention has been described by way of example and in terms of the preferred embodiment(s), it is to be understood that the invention is not limited thereto. On the contrary, it is intended to cover various modifications and similar arrangements and procedures, and the scope of the appended claims therefore should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements and procedures.