Patent Publication Number: US-8981923-B2

Title: Remote control signal receiver and electronic device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2009-221217, filed on Sep. 25, 2009, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a remote control signal receiver and an electronic device that uses the same, and more particularly, to a remote control signal receiver including a plurality of signal reception units enabling remote control from multiple directions and an electronic device that uses the same. 
     In the prior art, infrared remote controllers are often used for electronic devices such as video projectors. A remote controller may be combined with more than one signal reception units, or vise versa. For example, Japanese Laid-Open Patent Publication No. 2009-21687 describes an image display device including a plurality of signal reception units for receiving a control code signal transmitted from a remote controller. The image display device includes a signal receiver that may receive control code signals from a plurality of remote controllers with the plurality of signal reception units. In such a case, the operations of the plurality of remote controllers are alternately employed to prevent operations that are unintended by the user from being performed. 
     SUMMARY OF THE INVENTION 
     The electronic device may be a video projector, in which case, the needs described below arises. Referring to  FIG. 6(   a ), a video projector  1  includes a housing  10  having a front plate  11  and an upper plate  12 . A signal reception unit  3  is often arranged on the front plate  11  of the housing  10  to receive an infrared signal  21  from a remote controller  2  when the video projector  1  is placed upright on the floor. However, as shown in  FIG. 6(   b ), when the video projector  1  is suspended upside down from the ceiling, it is desirable that the signal reception unit  3  be arranged on the lower surface of the housing  10 , which is defined by the upper plate  12 , to respond to the infrared signal  21  from the remote controller  2  that is located at a lower position. To satisfy this desire, the signal reception unit  3  may be arranged on the front surface of the housing  10 , and a signal reception unit  4  may be arranged on the upper surface of the housing  10 , as viewed in a state in which the video projector  1  is placed upright. In this manner, when using a plurality of signal reception units  3  and  4 , light reception elements of the signal reception units  3  and  4  may be mounted on the same circuit board to decrease circuit boards and cables and to reduce costs. Further, to harmonize the signal reception units  3  and  4  with the design of the video projector, the signal reception units  3  and  4  may be arranged on a corner of the housing  10  so that the components of the signal reception units  3  and  4  are arranged near one another in the housing  10 . 
       FIGS. 7 and 8  show a referential example of a video projector that receives light signals from multiple directions.  FIG. 7  is a perspective view of  FIG. 6 , and FIG.  8  is a cross-sectional view taken along line A-A in  FIG. 7 . The referential example of  FIGS. 6 to 8  is given by the inventor of the present invention only for comparison with the present invention and is not admitted as prior art. In this example, the front signal reception unit  3  includes a light reception window  31 , which is formed in the front plate  11 , and a light reception element  32 , which is arranged in the housing  10  facing toward the light reception window  31  en a circuit board  5 . Further, the upper signal reception unit  4  includes a light reception window  41 , which is formed in the upper plate  12 , and a light reception element  42 , which is arranged in the housing  10  facing toward the light reception window  41  on the circuit board  5 . 
     The signal reception units  3  and  4  are arranged next to each other on the upper right corner of the housing  10 . In this specification, the frame of reference is the state of  FIG. 7  when referring to the front, rear, left, and right directions. Further, the surface to which the signal reception unit  3  is attached is referred to as the front surface to define the front, rear, left, and right directions. Further, the signal reception units  3  and  4  share the same circuit board  5 , on which the light reception elements  32  and  42  and a signal processor for processing signals received from the light reception elements  32  and  42  are mounted. Fastening screws  52  fasten the circuit board  5  to a fastening plate  51  so that the circuit board  5  lies along a plane orthogonal to the front plate  11  and the upper plate  12 . 
     For example, when the video projector  1  is placed upright on the floor as shown in  FIG. 6(   a ) and the infrared signal  21  from the remote controller  2  is received by the signal reception unit  3  on the front plate  11 , infrared noise  61  from a fluorescent lamp  6 , which is arranged on the ceiling, may enter the housing  10  through the light reception window  41  in the upper plate  12 . In the same manner, when the video projector is suspended from the ceiling as shown in  FIG. 6(   b ) and the infrared signal  21  from the remote controller  2  is received by the lower signal reception unit  4 , infrared noise  61  from the fluorescent lamp  6 , which is arranged on the ceiling, may enter the housing  10  through the light reception window  31  in the front plate  11 . 
     The infrared light entering the light reception window  41  of the upper plate  12  may be, for example, reflected into stray light by an inner surface of the housing  10  or other electronic components  53  and  54 , as shown by the broken lines in  FIG. 8 . In this case, the stray light may be transmitted to the front signal reception unit  3 . The infrared noise  61  received by the light reception element  32  of the signal reception unit  3  may interfere with remote control operations that were intended to be performed in accordance with the infrared signal  21  through the signal reception unit  3 . This may result in erroneous operations. The same situation may occur when infrared noise  61  enters the light reception window  31  of the signal reception unit  3 . 
     In this manner, when the signal reception units  3  and  4  are arranged near each other, a continuous space through which a transmission path of the infrared noise  61  extends, that is, a non-partitioned space, is formed in the housing  10  between the signal reception units  3  and  4 . As a result, the infrared noise  61  entering the light reception window for one of the signal reception units may affect remote control operations performed by the other one of the signal reception units. However, Japanese Laid-Open Patent Publication No. 2009-21687 does not address this problem. To resolve this problem, a controller that selects the activated one of the signal reception units  3  and  4  may be employed. However, as long as a continuous space, which allows for extension of the infrared transmission path, is formed between the signal reception units  3  and  4  in the housing  10 , the infrared noise  61  entering one of the signal reception units ( 3  or  4 ) cannot be prevented from interfering with the remote control operations performed by the other one of the signal reception units ( 4  or  3 ). 
     One aspect of the present invention is a remote control signal receiver including a plurality of signal reception units. Each signal reception unit includes a light reception window arranged in a housing of an electronic device and a light reception element arranged in the housing facing toward the light reception window. The light reception elements of the signal reception units are mounted on a circuit board. A transmission barrier prevents infrared noise entering the housing through the light reception window of one of the signal reception units from being transmitted to the light reception element of another one of the signal reception units. 
     Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
         FIG. 1(   a ) is a perspective view showing a remote control signal receiver for a video projector according to one embodiment of the present invention, and  FIG. 1(   b ) is a cross-sectional view of  FIG. 1(   a ); 
         FIG. 2(   a ) is a perspective view showing the remote control signal receiver of  FIG. 1(   a ), and  FIG. 2(   b ) is an exploded perspective view showing the remote control signal receiver of  FIG. 2(   a ); 
         FIG. 3  is a diagram showing a transmission barrier in the remote control signal receiver of  FIG. 1(   a ); 
         FIG. 4  is a cross-sectional view showing a modification of the remote control signal receiver; 
         FIG. 5  is a cross-sectional view showing a further modification of the remote control signal receiver; 
         FIG. 6(   a ) is a schematic diagram showing a referential example of a video projector arranged on a floor, and  FIG. 6(   b ) is a schematic diagram showing the video project in a state suspended from a ceiling; 
         FIG. 7  is a perspective view showing the video projector of  FIG. 6 ; and 
         FIG. 8  is a cross-sectional view showing the video projector and taken along line A-A in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A remote control signal receiver for a video projector according to one embodiment of the present invention will now be discussed with reference to  FIGS. 1 to 3 . Like or same reference numerals are given to those components that are the same as the corresponding components of the referential example described above. Such components will not be described in detail. 
     A video projector  1  serving as an electronic device in this embodiment has an outer appearance that is identical to the video projector of the referential example (refer to  FIG. 7 ). Signal reception units  3  and  4  are arranged on a front plate  11  and an upper plate  12  to allow for the remote controller  2  to perform remote control operations from multiple directions. When comparing the video projector  1  with that of the referential example shown in  FIGS. 6 to 8 , the arrangement of light reception windows  31  and  41  of the signal reception units  3  and  4  on a housing  10  is the same. Further, the arrangement of the circuit board  5 , on which light reception elements  32  and  42  are mounted, on the housing  10  is also the same. 
     In the video projector  1  of the present invention, a signal receiver includes a transmission barrier  100 , which is added to the signal receiver in the referential example of  FIGS. 6 to 8 . The transmission barrier  100  prevents infrared noise  61  that enters a light reception window ( 31  or  41 ) of one of the signal reception units ( 3  or  4 ) from being transmitted to light reception elements ( 42  or  32 ) of the other one of the signal reception units ( 4  or  3 ). 
     The light reception windows  31  and  41 , which are not connected to each other, are each formed by an independent transparent plate. The light reception windows  31  and  41  are each formed to have the minimal required size. Further, the light reception windows  31  and  41  are arranged at different locations on the housing  10 . The housing  10  includes a front plate  11  and an upper plate  12 . Part of the front plate  11  and part of the upper plate  12  extend between the two light reception windows  31  and  41 , as shown in  FIGS. 1 and 3 . In the illustrated example, the front plate  11  and the upper plate  12  are coupled to each other at a right angle and form a corner in between. The light reception windows  31  and  41  may be located near the line of intersection between the plates  11  and  12 . The housing  10  is formed by a non-transparent member from resin or a metal material, such as steel or aluminum. 
     The transmission barrier  100  (refer to  FIG. 1 ) will now be described in detail. 
     The transmission barrier  100  cooperates with the circuit board  5  and the housing  10  to spatially separate the light reception elements  32  and  42 . A cover member  110  is attached to the circuit board  5  to cover one of the light reception elements. In the illustrated example, the cover member  110 , the circuit board  5 , and the inner surface of the housing  10  cooperate to define a light reception compartment that encompasses the upper light reception element  42  in the housing  10 . The front light reception element  32  that is not covered by the cover member  110  is arranged outside the light reception element compartment. 
     In a preferred example, the transmission barrier  100  includes a shield  120  that closes gaps between the cover member  110  and the upper plate  12  around the portion of the housing  10  surrounding the light reception window  41 . This prevents such gaps from connecting the interior of the cover member  110  that is in communication with the light reception window  41  and the exterior of the cover member  110 . That is, the shield  120  prevents the gaps from forming a transmission path of infrared noise  61 . 
     The cover member  110  includes a partition wall  111 , an upper wall  112 , a rear wall  113 , a side wall  114 , a hooking wall  115 , and a fastening wall  116 . The partition wall  111  partitions the two light reception elements  32  and  42  of the signal reception units  3  and  4  on the circuit board  5 . The upper wall  112  is arranged next to the upper plate  12  and is open at a portion immediately above the light reception element  42 . The rear wall  113  covers the rear surface of the light reception element  42 . The side wall  114  faces toward the circuit board  5  and covers the right surface of the light reception element  42 . The hocking wall  115  is hooked to the circuit board  5 . The fastening wall  116  serves as a fastening piece. In the illustrated example, the cover member  110  resembles a container having a triangular interior. A projection wall  117  serving as a lug extends from the lower rear end of the cover member  110 . The partition wall  111  partitions a continuous space between one of the signal reception units and the other one of the signal reception units that would form a transmission path of infrared noise  61 . Thus, the partition wall  111  prevents a non-partitioned space from being formed between the signal reception units  3  and  4  in the housing  10 . When the light reception elements  32  and  42  are mounted on the same mounting surface of the circuit board  5 , it is preferable that the partition wall  111  extend from one edge to another edge of the circuit board  5  on the same mounting surface of the circuit board  5 . 
     The upper wall  112  has a length set so as not to cover the portion immediately above the light reception element  42  and thereby ensure an inlet for an infrared signal  21  between the upper wall  112  and the partition wall  111 . It is preferred that the top end of the partition wall  111  be located near the portion of the housing  10  between the light reception windows  31  and  41 , particularly, the corner between the front plate  11  and the upper plate  12 . The top end of the partition wall  111  is located near the housing  10  to prevent the gap between the top end of the partition wall  111  and the housing  10  from functioning as an infrared noise transmission path. Infrared noise  61  directed toward the gap between the top surface of the partition wall  111  and the housing  10  is repetitively reflected and attenuated by the partition wall  111 , the front plate  11 , and the upper plate  12 . The attenuation occurs when the energy from infrared light striking the partition wall  111 , the front plate  11 , and the upper plate  12  is partially absorbed by the material forming the partition wall  111 , the front plate  11 , or the upper plate  12 . More specifically, the energy from infrared light striking a dielectric material is partially absorbed by the dielectric material. The infrared light decreases as it repeats reflection. For the same reason, it is preferred that the top end of the circuit board  5  be located near the upper plate  12  and the upper wall  112  of the cover member  110  be located near the upper plate  12 . 
     The fastening wall  116  includes two insertion holes  115   a  (refer to  FIG. 2(   d )) into which fastening screws  52  are inserted to fasten the cover member  110  together with the circuit board  5  to a fastening plate  51 . A backing plate  51   b  serving as a screw seat is attached to the back surface of the fastening plate  51 . The circuit board  5  includes insertion holes  5   a  into which the fastening screws  52  are inserted. Such a structure fastens the cover member  110  together with the circuit board  5  to the fastening plate  51  with the fastening screws  52 . The cover member  110  may be formed from a metal material, such as steel or aluminum, or a non-metal material, such as a resin or rubber. 
     Accordingly, when attaching the cover member  110  to the circuit board  5  so as to cover the light reception element  42 , the light reception element  42  is substantially isolated from the other light reception element  32 , while ensuring a transmission path for the infrared signal  21  that enters the interior of the cover member  110  through the light reception window  41 . In this manner, infrared noise  61  entering one of the two light reception windows  31  and  41  is substantially prevented from being transmitted to the other light reception element  32 . 
     The shield  120  prevents gaps between the cover member  110  and the upper plate  12  from forming a transmission path of infrared noise  61  that connects the interior of the cover member  110 , which is in communication with the light reception window  41 , and the exterior of the cover member  110 . The shield  120  includes downward extending walls  121  and  122 , which extend downward from the upper plate  22  and are formed integrally with the upper plate  12 . The joined circuit board  5  and cover member  110  are held between the downward extending walls  121  and  122  with slight gaps  121   a  and  122   a  formed in between. The slight gaps  121   a  and  122   a  between the circuit board  5  and the cover member  110  repetitively reflects and attenuates the infrared noise  61  passing through the gaps  121   a  and  122   a . In this manner, the downward extending walls  121  and  122  substantially prevent leakage of the infrared noise  61  while leaving a gap between the top end of the cover member  110  and the upper plate  12 . 
     It is preferred that the downward extending walls  121  and  122  be in contact with the circuit board  5  and the cover member  110  so as not to form the gaps  121   a  and  122   a . However, when it is difficult to completely eliminate the gaps  121   a  and  122   a  for economic or manufacturing reasons, the shield  120  shown in  FIG. 1(   b ) is effective. 
     The remote control signal receiver of the present embodiment and the video projector using the remote control signal receiver prevent the infrared noise  61  entering the light reception window ( 31  or  41 ) of one of the signal reception units ( 3  or  4 ) from being transmitted to the light reception element ( 42  or  32 ) of the other one of the signal reception units ( 4  or  3 ) as described below. 
     For example,  FIG. 6   a ) shows a situation in which infrared noise  61  enters the upper light reception window  41 . In this case, as shown in  FIG. 3 , the entering infrared noise  61  is repetitively reflected in the interior of the cover member  110  and ultimately transmitted to the gap between the cover member  110  and the upper plate  12 . However, as shown in  FIG. 1(   b ), the gap between the upper plate  12  and the joined circuit board  5  and cover member  110  is small, and the infrared noise  61  is repetitively reflected and attenuated when passing through the gap. The infrared noise  61  transmitted out of the cover member  110  from the gap is further repetitively reflected and attenuated in the gap  121   a  between the circuit board  5  and the downward extending wall  121  of the shield  120  or in the gap  122   a  between the side wall  114  and the downward extending wall  122  of the shield  120 . In this manner, the infrared noise  61  is prevented from being transmitted out of the gaps  121   a  and  122   a.    
     In the front part of the joined circuit board  5  and cover member  110 , the top end of the partition wall  111  is located near the corner between the upper plate  12  and the front plate  11 . The infrared noise  61  directed toward the gap between the top end of the partition wall  111  and the corner is repetitively reflected by the partition wall  111 , the front plate  11 , and the upper plate  12 . This prevents transmission of the infrared noise  61  from the gap. Further, in the rear part of the joined circuit board  5  and cover member  110 , a small gap is formed between the upper wall  112  and the upper plate  12 . Thus, in the same manner as the front part, transmission of the infrared noise  61  is prevented. 
     The above describes a situation in which infrared noise  61  enters the light reception window  41  when performing a remote control operation with the front signal reception unit  3 . The same situation occurs when, for example, as shown in  FIG. 6(   b ), infrared noise  61  enters the light reception window  31  and remote control operation is performed with the upper signal reception unit  4 . More specifically, in the front part of the joined circuit board  5  and cover member  110 , the top end of the partition wall  111  is located near the upper plate  12 . Thus, the infrared noise  61  directed toward the gap between the top end of the partition wall  111  and the upper plate  12  and enters the interior of the cover member  110  is repetitively reflected between the partition wall  111  and the housing  10 . This prevents transmission of the infrared noise  61  from the gap to the interior of the cover member  110 . Further, in the rear part of the joined circuit board  5  and cover member  110 , the gap is small between the upper wall  112  and the upper plate  12 . Thus, the infrared noise  61  in the gap directed toward the interior of the cover member  110  is repetitively reflected and attenuated in the gap. This prevents the infrared noise  61  from being transmitted to the interior of the cover member  110 . 
     The infrared noise  61  that enters the interior of the cover member  110  through the gap  121   a  between the circuit board  5  and the downward extending wall  121 , the gap  122   a  between the side wall  114  and the downward extending wall  122 , and the gap between the cover member  110  and the upper plate  12  is repetitively reflected and attenuated in the gap  121   a , the gap  122   a , and the gap between the cover member  110  and upper plate  12 . Accordingly, the infrared nose  61  is prevented from entering the interior of the cover member  110 . 
     In this manner, in the remote control signal receiver the present embodiment, the infrared noise  61  entering the light reception window ( 31  or  41 ) of one of the signal reception units ( 3  or  4 ) is prevented from being transferred to the light reception element ( 42  or  32 ) of the other one of the signal reception units ( 4  or  3 ). This prevents remote control operations performed by the other one of the signal reception units ( 4  or  3 ) from being interfered. 
     The remote control signal receiver of the present embodiment has the advantages described below. 
     (1) The transmission barrier  100  prevents the infrared noise  61  entering the light reception window ( 31  or  41 ) of one of the signal reception units ( 3  or  4 ) from being transferred to the other one of the signal reception units ( 4  or  3 ). Thus, intended remote control operations performed in accordance with the infrared signal  21  with the other one of the signal reception units ( 4  or  3 ) are not interfered by the infrared noise  61 . 
     (2) If the light reception windows  31  and  41  were to be connected to each other and the infrared noise  61  were to be emitted toward either one of the light reception windows  31  and  41 , there would be a tendency for the infrared noise  61  to be transmitted to the light reception elements  32  and  42  of the other one of the signal reception units  3  and  4 . However, in the illustrated example, the light reception windows  31  and  41  are not connected to each other and formed independently from each other in the housing  10 . Thus, such a problem does not occur. 
     (3) The transmission barrier  100  is formed to cooperate with the housing  10  and prevent the transmission of infrared noise  61  from one of the signal reception units to the other one of the signal reception units. By using part of the originally existing housing  10  of the electronic device, the structure of the transmission barrier  100  is simplified. 
     (4) The transmission barrier  100  is formed to cooperate with the circuit board  5  and prevent transmission of infrared noise  61  from one of the signal reception units to the other one of the signal reception units. The transmission barrier  100  isolates the light reception elements  32  and  42 , which are mounted on the circuit board  5 , from each other. Thus, the use of at least part of the circuit board  5  simplifies the structure of the transmission barrier  100 . 
     (5) The transmission barrier  100  includes the partition wall  111 , which partitions the signal reception units  3  and  4  on the circuit board  5 . As shown in  FIG. 3 , the partition wall  111  prevents the infrared noise  61  from being directly transmitted from one of the signal reception units to the light reception element of the other one of the signal reception units. This significantly contributes to preventing the transmission of the infrared noise  61 . It should be noted that even if the transmission barrier  100  were to include just the partition wall  111 , this would still have a significant effect for preventing infrared noise transmission. 
     (6) As apparent from  FIG. 3 , one end of the partition wall  111  is located near the housing  10  between the light reception windows  31  and  41 , specifically, the corner between the front plate  11  and the upper plate  12 . Thus, the partition wall  111  cooperates with the housing to encompass the portion through which infrared noise  61  has a tendency to pass near the signal reception units  3  and  4 . This effectively prevents the transmission of infrared noise  61  with a simplified structure. Further, the infrared noise  61  that passes through the gap between the partition wall  111  and the housing  10  is repetitively reflected and attenuated by the partition wall  111  and the housing  10 . This prevents transmission of the infrared noise  61 . 
     (7) The cover member  110  of the transmission barrier  100  is attached to the circuit board  5  so as to cover the light reception element  42  while leaving a transmission path for the infrared signal  21  into the interior of the cover member  110  from the light reception window  41 . The light reception element  32  located outside the cover member  110  is substantially shut out from the interior of the cover member  110 . This substantially prevents the transmission of infrared noise  61  between the interior and exterior of the cover member  110 . 
     (8) The shield  120  of the transmission barrier  100  prevents the interior of the cover member  110  that is communication with the light reception window  41  and the gap between the cover member  110  and the exterior from forming a transmission path for infrared noise  61 . More specifically, the shield  120  includes the downward extending wall  121 , which faces toward the circuit board  5  with the slight gap  121   a  in between, and the downward extending wall  122 , which faces toward the side wall  114  with a slight gap  122   a  in between. Accordingly, infrared noise  61  passing through the gap between the cover member  110  and the housing  10  is repetitively reflected and attenuated by the shield  120 . This effectively prevents transmission of the infrared noise  61 . 
     Even when a gap connecting the exterior and interior of the cover member  110  is located near the light reception window  41 , the shield  120  encompasses the light reception element  42  outside the cover member  110 . This substantially prevents transmission of infrared light from the light reception window  41  to the exterior of the cover member  110 . 
     (9) In the front part of the joined circuit board  5  and cover member  110 , the top end of the partition wall  111  is located near the corner between the upper plate  12  and the front plate  11 . Thus, infrared noise  61  passing through the gap between the top end of the partition wall  111  and the housing  10  is repetitively reflected and attenuated. This prevents transmission of the infrared noise  61 . Further, in the rear part of the joined circuit board  5  and the cover member  110 , a small gap is formed between the upper wall  112  and the upper plate  12 . Thus, in the same manner as in the front part, infrared noise  61  is repetitively reflected and attenuated. This prevents transmission of the infrared noise  61 . 
     (10) The electronic device of the present embodiment includes the above-described remote control signal receiver. Thus, remote control operations may be performed from multiple directions without any problems. 
     (11) The video projector serving as an electronic device according to one embodiment of the present invention includes the above-described remote control signal receiver. This facilitates and ensures remote control operations in various states of installation, such as when the video projector is placed on a floor, hooked on a wall, or suspended from a ceiling. 
     It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the scope of the invention. Particularly, it should be understood that the present invention may be embodied in the following forms. 
     The transmission barrier  100  may be formed by only the partition wall  111 . Such a structure would also be significantly advantageous as mentioned in the foregoing description. 
     In the above-discussed embodiment, the top end of the partition wall  111  is located near the corner of the front plate  11  and the upper plate  12 . However, when allowed by assembly conditions, the top end of the partition wall  111  may be in contact with the corner of the front plate  11  and the upper plate  12 . This would prevent the transmission of infrared noise more easily. 
     The transmission barrier  100  may be formed by just the cover member  110 , and the shield  120  may be eliminated. In such a structure, one of the signal reception units would be substantially covered. This would substantially prevent transmission of the infrared noise  61 . 
     In the above-discussed embodiment, the cover member  110  covers the light reception element  42  of the upper signal reception unit  4 , and the shield  120  corresponds to the light reception window  41  of the signal reception unit  4 . Instead, the cover member  110  may cover the light reception element  32  of the front signal reception unit  3 , and the shield  120  may be formed in correspondence with the light reception window  31  of the signal reception unit  3 . This would obtain the same advantages as in the above-discussed embodiment. 
     The downward extending walls  121  and  122  are formed integrally with the upper plate  12  in the above-discussed embodiment. Alternatively, as shown in  FIG. 4 , downward extending walls  121  and  122 , which are discrete from the upper plate  12 , may be fixed to the upper plate  12  by a suitable means, such as adhering or welding. When the downward extending walls  121  and  122  are discrete from the upper plate  12 , a slight gap may be formed between the downward extending walls  121  and  122  and the upper plate  12 . Such a gap may result in a lower effect for shielding infrared noise compared to the above-discussed embodiment. 
     In the above-discussed embodiment, the upper wall  112  is formed so as to ensure an inlet for an infrared signal  21  between the upper wall  112  and the partition wall  111 . The shape of the upper wail  112  is not limited as long as it does not cover the portion located immediately above the light reception element  42 . For example, as shown in  FIG. 5 , the upper wall  112  may be connected to the top end of the partition wall  111  and include a hole  112   a , which allows for the passage of the infrared signal  21 . 
     The present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.