Abstract:
A remote-control light receiving unit includes a remote-control light receiving unit body having a lens portion, and a light guiding member that guides transmission signal light received from a remote-control transmitter to the lens portion. In the remote-control light receiving unit body, at least a photoelectric conversion device and a signal processing device that processes an electric signal received from the photoelectric conversion device are mounted on a lead frame, and encapsulated in a light permeable resin. The light guiding member has a terminal end surface that emits the transmission signal light toward the lens portion. The light guiding member is disposed with at least a part of the terminal end surface in close contact with the lens portion.

Description:
This nonprovisional application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2004-373017 filed in Japan on 24 Dec. 2004, the entire contents of which are hereby incorporated by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a remote-control light receiving unit used for electric home appliances and information communication products (personal computers etc.). 
   2. Description of the Related Art 
   In a receiving device for remote control (hereinafter referred to as remote-control light receiving unit) that receives an infrared light signal transmitted from a device for remote control that is called a “remote control transmitter” and so on, a light receiving element [e.g., photodiode chip (hereinafter referred to as PD chip)] receives the infrared light signal transmitted from the remote-control transmitter. Then, various signal processings such as amplification and waveform shaping are executed by a signal control processing device (hereinafter referred to as IC chip) so that remote control of various audio visual apparatuses such as TVs and DVDs or office automation apparatuses such as personal computers is carried out in response to the received signal. 
   Infrared light signals transmitted from the remote-control transmitter are digital signals. These digital signals are received at a light receiving surface of the PD chip, and the received optical signals are converted to weak electrical signals. The weak electrical signals are amplified by several tens of thousands by an amplifier circuit within the IC chip. A filter circuit [band pass filter (BPF)] extracts signals of necessary frequencies from the amplified electrical signals. Thereafter, the extracted signals are outputted by a detection circuit as digital waveform information similar to the above infrared light signals. 
   A remote-control light receiving unit of this type is formed by mounting and fixing the PD chip and the IC chip on a lead frame and encapsulating them in a molding resin. As the remote-control light receiving unit, there are a multi-chip type light receiving unit in which the molding resin is externally covered with a metallic case and a multi-chip type light receiving unit in which the inside of the molding resin is covered with a lead frame. In general, a distance of 10 m or more of remote control is required as a function necessary for the remote-control light receiving unit. Signal amplification processing for amplifying a weak electrical signal by several tens of thousands is, however, executed in both of the multi-chip type light receiving parts. Therefore, noise components such as electromagnetic noises that are not signals are also amplified by the amplification circuit, so that the magnitude ratio of the signal to the noise (SN ratio) cannot be secured. Consequently, it becomes impossible to extract only necessary signals. In order to prevent such a phenomenon, electromagnetic shielding is frequently performed by covering the PD chip, IC chip and peripheries thereof with a conductive resin, a metallic shielding case or the like. 
   It is required that a remote-control light receiving unit to be installed in an apparatus such as a TV or a DVD (digital versatile disk) apparatus (hereinafter simply referred to as “apparatus”) be positioned at the front of the apparatus in order to receive the infrared signal from a remote-control transmitter. 
   In a structure in which a main board is placed so as to extend in a depth direction like the TV and the like, the remote-control light receiving unit may be placed on a sub-board fitted to the main board so as to be positioned at the front of the apparatus, but it is common that the remote-control light receiving unit is placed on the main board to avoid an increase in cost (e.g., JP 2001-94124 A). 
   In such a case, since the apparatus takes a structure in which the remote-control light receiving unit is set far back from the front of the apparatus, there arises necessity to efficiently transfer a transmission signal from the front portion of the apparatus to a lens portion of the remote-control light receiving unit body. Thus, as taught in JP 2001-94124 A, a light guiding member (light guide) is provided from the front of the apparatus to the remote-control light receiving unit so that transmission signal light that is incident on the front of the apparatus is transferred to the remote-control light receiving unit. The light guiding member is generally an injection molded product using a thermoplastic transparent resin or an infrared light permeable resin. The light guiding member is a separate part from the remote-control light receiving unit. 
   Next, the structures of the remote-control light receiving unit and the light guiding member will be described with reference to  FIGS. 4 to 7A ,  7 B. In  FIG. 4 , a PD chip  2  is bonded to a metallic lead frame (Iron lead frames are the mainstream. The metallic lead frame will be hereinafter simply referred to as “lead frame”)  1  with an insulative adhesive  3 , while an IC chip  4  is bonded with a conductive adhesive  5 . The PD chip  2  usually has a PN junction structure, and because an inverse voltage is applied to the PD chip in the case of the remote-control light receiving unit, an electric potential occurs at an N electrode on the rear surface side of the chip. Therefore, it is required that an insulating state be kept between the PD chip  2  and a PD chip mounting portion of the lead frame, which portion has a GND potential because of the structure of the lead frame  1 , and an epoxy resin containing an insulating filler is used for bonding the lead frame  1  and the PD chip  2 . 
   On the other hand, since a signal processing is executed on a surface of the IC chip  4 , its rear surface is irrelevant to the signal processing. Thus, bonding to the lead frame  1  may be done with either of the conductive adhesive  5  or the insulative adhesive  3 . Usually, the conductive adhesive (an adhesive prepared by mixing Ag powder with an epoxy resin and the like)  5  is used. An electrode of the PD chip  2 , an electrode  6  of the IC chip  4  and an input/output lead  7  of the lead frame  1  are connected to one another with a gold wire (hereinafter referred to as Au wire) having a diameter of tens of micrometers  8 . Similarly, the IC chip  4  and other input/output leads  7  are connected to one another with Au wires. 
   The PD chip  2  and the IC chip  4  mounted on the lead frame  1  in the above-mentioned manner are encapsulated in a thermosetting resin (hereinafter referred to as a mold encapsulation resin)  9  which is mixed with a dye that transmits infrared light and blocks visible light. Deburring and bar-resin cutting are performed on the lead frame  1  exposed from the mold encapsulation resin  9 . 
     FIG. 6  shows a four-side view of a molded resin product having the mold encapsulation resin  9  in an injection molded state. Referring to  FIG. 6 , injection molding is performed so that the mold encapsulation resin  9  of the molded resin product is covered with a conductive thermoplastic resin  11  (hereinafter referred to as secondary molding). Tie-bar cutting and soldering are performed on the lead frame  1  exposed from the mold encapsulation resin  9 . In this manner, the input/output leads  7  of the lead frame  1  are separated from one another to be individual input/output leads  12 . Subsequently, the resultant lead frame goes through a single-piece cutting process whereby a lead frame as a single article is obtained. 
   A method of installing the thus formed remote-control light receiving unit in an apparatus such as a TV or the like, and a method of transferring incident light will be described below. 
     FIG. 7A  and  FIG. 7B  respectively show a front elevational view of the apparatus, in which a remote-control light receiving unit is installed, and a cross sectional view taken along line  7 B- 7 B of  FIG. 7A . In  FIGS. 7A and 7B , a main board  15  is placed so as to extend in a depth direction of the apparatus, and an individual remote-control light receiving unit  16  as shown in  FIG. 6  is provided on the main board  15  with its input/output terminals erect. On the other hand, a light receiving window  17  for transmission signal light, which is positioned at the front of the apparatus, is provided in an outer frame (which is a plastic molded product in many cases)  18  of the apparatus. An interspace from the light receiving window  17  to the remote-control light receiving unit  16  is made up for with a light guiding member (lightguide)  19  so that the transmission signal light reaches a lens of the remote-control light receiving unit  16  from the light receiving window  17 . 
   However, the conventional remote-control light receiving unit has the following problem. That is, since the remote-control light receiving unit  16  is an electric component, it requires to be mounted on a wiring board having a wiring pattern. On the other hand, since the remote-control light receiving unit  16  also must serve as a light receiving component, it requires to be positioned at the front of the apparatus. In order to satisfy both of these conditions, the light guiding member  19  is provided. However, the light guiding member  19  is fitted to the outer frame  18  of the apparatus, and the remote-control light receiving unit  16  is fitted to the main board  15 . That is, the light guiding member  19  and the remote-control light receiving unit  16  are provided at different supports. Therefore, positioning accuracy between the light guiding member  19  and the remote-control light receiving unit  16  tends to be poor. 
   When displacement between the light guiding member  19  and the remote-control light receiving unit  16  is large, transmission signal light emitted from the light guiding member  19  is not efficiently transferred to the lens portion of the remote-control light receiving unit  16 , so that the reach of the transmission signal light from the remote-control transmitter is reduced. Furthermore, if there is a gap between a terminal end portion of the light guiding member  19  and the lens portion of the remote-control light receiving unit  16 , the angle of light emitted from the light guiding member  19  may be biased or the light may be dispersed depending on the angle of transmission signal light that is made incident on the light guiding member  19 , so that the light is not efficiently emitted toward the lens portion of the remote-control light receiving unit  16 . Consequently, the transmission signal light from the remote-control transmitter has a reduced reach. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a remote-control light receiving unit that can efficiently transfer transmission signal light incident on a light guiding member from a remote-control transmitter to a lens portion of the unit. 
   In order to accomplish the above object, a remote-control light receiving unit according to the present invention includes: 
   a remote-control light receiving unit body in which at least a photoelectric conversion device that converts an optical signal into an electrical signal and a signal processing device that processes the electrical signal from the photoelectric conversion device are mounted on a lead frame, and encapsulated in a light permeable resin; 
   a lens portion provided at the remote-control light receiving unit body and focusing incident light at the photoelectric conversion device; and 
   a light guiding member that guides transmission signal light received from a remote-control transmitter to the lens portion; wherein 
   the light guiding member has a terminal end surface that emits the received transmission signal light toward the lens portion, and the light guiding member is disposed with at least a part of the terminal end surface in close contact with the lens portion such that transfer efficiency of the transmission signal light guided from the light guiding member to the lens portion is improved. 
   With the above construction, at least a part of the terminal end surface of the light guiding member that guides incident transmission signal light to the lens portion is in close contact with the lens portion. Therefore, the transmission signal light emitted from the terminal end surface of the light guiding member can efficiently be transferred to the lens portion. That is, according to the present invention, a reduction in the reaches of the transmission signal light from the remote control transmitter can be suppressed as much as possible. 
   In one embodiment, the light guiding member and the remote-control light receiving unit are integrally formed, and the entire terminal end surface of the light guiding member is in close contact with the lens portion. 
   According to this embodiment, the transmission signal light emitted from the terminal end surface of the light guiding member is transferred to the lens portion efficiently. 
   In one embodiment, the remote-control light receiving unit has a light shielding layer that covers an outer peripheral surface on at least a terminal end surface side of the light guiding member and an outer peripheral surface of at least the light permeable resin of the remote-control light receiving unit body. 
   In the embodiment, the transmission signal light that is transferred within the light guiding member is prevented from leaking through the outer peripheral surface of the light guiding member to the outside, and transfer of the transmission signal light is efficiently performed. 
   In one embodiment, conductive substance is mixed into the light guiding member. 
   According to the embodiment, the light guiding member is provided with conductivity, so that a pillar shaped conductor can be disposed in a region from the apparatus in which the remote-control light receiving unit is installed to the front of the lens portion. Therefore, resistance to electromagnetic noises can be improved. 
   In one embodiment, a light reflection layer is provided between the light guiding member and the light shielding layer. Preferably, the light reflection layer may be in close contact with the light guiding member and the light shielding layer. 
   According to the embodiment, the light reflection layer and the light shielding layer are formed around the outer peripheral surface of the light guiding member. Therefore, the reflectance of transmission signal light on the outer peripheral surface of the light guiding member can be improved, thus making it possible to perform efficient transfer to the lens portion of the transmission signal light transferred within the light guiding member. 
   In one embodiment, the remote-control light receiving unit includes a light shielding and reflection layer that covers an outer peripheral surface on at least a terminal end surface side of the light guiding member and an outer peripheral surface of the light permeable resin. The light shielding and reflection layer may preferably in close contact with the outer peripheral surface of the light guiding member and the outer peripheral surface of the light permeable resin. 
   According to this embodiment, a layer having a light shielding effect and a layer having light reflectivity are combined into one layer. Therefore, the number of manufacturing steps is reduced to achieve cost reduction. 
   In an electronic apparatus according to the present invention, the above remote-control light receiving unit of the invention is used. 
   With the above construction, due to the use of the remote-control light receiving unit that is able to efficiently transfer transmission signal light from the remote-control transmitter to the lens portion, a reduction in the reach of the transmission signal light from the remote-control transmitter can be suppressed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
       FIG. 1  is a longitudinal cross sectional view of a remote-control light receiving unit according to a first embodiment of the present invention; 
       FIG. 2  is a longitudinal cross sectional view of a remote-control light receiving unit according to a second embodiment of the present invention; 
       FIG. 3  is a longitudinal cross sectional view of a remote-control light receiving unit according to a third embodiment of the present invention; 
       FIG. 4  is a view showing a state in which a PD chip and an IC chip are mounted on a lead frame; 
       FIG. 5  is a view showing a state in which the PD chip and the IC chip mounted on the lead frame are encapsulated in a mold resin; 
       FIG. 6  is an explanatory illustration of secondary molding for a molded resin product; and 
       FIG. 7A  and  FIG. 7B  are a front elevational view of an apparatus in which a conventional remote-control light receiving unit is installed, and a cross sectional view taken along line  7 B- 7 B of  FIG. 7A , respectively, which explain installation of the remote-control light receiving unit in an apparatus. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The present invention will be described in detail below based on the embodiments illustrated in the attached drawings. 
   First Embodiment 
     FIG. 1  shows a longitudinal cross sectional view of a remote-control light receiving unit according to an embodiment of the present invention. This remote-control light receiving unit  21  includes a remote-control light receiving unit body  22  having a lens portion  24 , and a light guiding member  23  fixed to and in close contact with the remote-control light receiving unit body  22 . The remote-control light receiving unit body  22  is of the same structure as the single remote-control light receiving unit as shown in  FIG. 5  and thus illustration and description of its internal structure will be omitted. 
   The light guiding member  23  has a shape of combined circular cylinder and cone, more specifically truncated cone. A diameter at a terminal end portion  25  of the circular cylinder portion is the same as or smaller than a diameter at a base of the remote-control light receiving unit lens portion (hereinafter simply referred to as lens portion)  24  at the front of the remote-control light receiving unit body  22 . The light guiding member  23  is disposed in a state in which the terminal end portion  25  is in close contact with the front of the lens portion  24 . The reason why the diameter at the terminal end portion  25  of the light guiding member  23  is the same as or smaller than the diameter at the base of the lens portion  24  is to ensure that the entirety of a terminal end surface  25   a  of the light guiding member  23  is in close contact with the front of the lens portion  24  so that light emitted from the terminal end surface  25   a  is made incident on the lens portion  24  without loss. If the diameter at the terminal end portion  25  is larger than the diameter at the base of the lens portion  24 , light from the light guiding member  23  will be emitted also to regions other than the lens portion  24 , that is, there will be light that is not condensed by the lens portion  24 . Therefore, there occurs loss in the transfer of transmission signal light. 
   Contrary to that, the entrance side of the light guiding member  23  spreads conically, which increases an area of its entrance portion  26 , so as to be able to take in as much transmission signal light (infrared light) as possible. Because the design of the apparatus should be considered, the entrance portion  26  cannot be blindly made larger, but making the area larger as far as the design layout permits can increase the reach of the transmission signal light from the remote-control transmitter because the absolute amount of light received increases. 
   The shape of the light guiding member  23  from the entrance portion  26  toward the terminal end portion  25  is a generally conical shape in which the area at the entrance portion  26  is large and that at the terminal end portion  25  is small, but the above shape may be changed to a straight shape or a branching shape for convenience of retention of the light guiding member  23  or sharing with other parts. However, if the number of branches increases, the leakage rate of light may increase and therefore, it is preferable not to perform branching if possible. 
   As a material of the light guiding member  23 , thermoplastic resins (such as polycarbonate, acrylic, etc.) and epoxy resins that transmit infrared light may be used. A resin having flexibility such as urethane may also be used such that the unit is easily fitted in an outer frame  27  of the apparatus. The light guiding member  23  contains conductive substances. 
   The periphery of the light guiding member  23  is provided with a light shielding layer  28 . As will be also described below in connection with the producing method, the light shielding layer  28  is in close contact with the light guiding member  23 . As a material of the light shielding layer  28 , a thermoplastic resin (polycarbonate etc.) having a light shielding effect and conductivity is used. Alternatively, similarly to the case of the light guiding member  23 , a resin having flexibility may be used such that the unit can be easily fitted in the frame of the apparatus. Forming the light shielding material on the periphery of the light guiding member  23  as described above produces the effect that transmission signal light that is being transferred within the light guiding member  23  is prevented from being discharged to the outside of the light guiding member  23 . Furthermore, a conductive filler is contained in the light shielding layer  28 , which improves the resistance to electromagnetic noises. 
   The light shielding layer  28  has portions that cover surfaces of the remote-control light receiving unit body  22  other than a surface of the lens portion  24  and a surface  31  of a molded portion  29  from which input/output leads  30  protrude (i.e., the covered surfaces being a rear surface, side surfaces, a top surface and a front surface other than the lens portion  24 ). The portions, of the light shielding layer  28 , that cover the periphery of the remote-control light receiving unit body  22  and the portion that covers the light guiding member  23  are molded simultaneously (integral molding). 
   Incidentally, electromagnetic noises to the remote-control light receiving unit  21  include noises derived from the apparatus itself in which the unit is installed, such as, for example, noises generated from a cathode ray tube of a TV, a compressor of an air conditioner, and the like, and noises derived from devices other than the apparatus, such as a fluorescent lamp stabilizer. In the present embodiment, a lattice-like mesh net made of a metal or other conductive material (not shown) is formed at the front of the lens portion  24  in the remote-control light receiving unit  21 , so that the resistance to electromagnetic noises is further increased. 
   As described above, in the light receiving unit of the present embodiment, the entirety of the terminal end surface  25   a  is in close contact with the front of the lens portion  24  of the remote-control light receiving unit body  22 . Also, the remote-control light receiving unit  21  has the light guiding member  23  having a conical shape open to the incident side of light. The periphery of the light guiding member  23  is covered with the light shielding layer  28  having a light shielding effect and conductivity. Therefore, a large amount of transmission signal light (infrared light) from the remote-control transmitter is introduced in the light guiding member  23 , and light emitted from the terminal end surface  25   a  of the light guiding member  23  is made incident on the lens portion  24  without loss. This can increase the distance the transmission signal light from the remote-control transmitter can reach. 
   Further, since the pillar-like conductor is formed in the region from the outer frame  27  of the apparatus to the front of the lens portion  24 , the resistance to noises is improved, as compared with the structure in which the front of the lens portion  21  is open to space. 
   Next, a method of producing the light guiding member  23  and the light shielding layer  28  will be described. 
   As shown in  FIG. 5 , the PD chip and the IC chip that are mounted on the lead frame are primary molded with a mold encapsulation resin. After bar-resin cutting, injection molding with a conductive resin is performed such that the conductive resin covers the primary molded product. In this way, the light shielding layer  28  is formed. In this case, first, placed is a mold that covers portions of the primary molded remote-control light receiving unit body  22  other than the surface  31 , that is firmly attached to the base of the lens portion  24 , and that has a cavity open in a trumpet shape toward the front to expose a surface of the lens portion  24 . Then, a thermoplastic resin having a light shielding effect and conductivity is injected to make a light shielding layer  28  defining a cavity open in a trumpet shape toward the front from the base of the lens portion  24 . 
   Next, a light permeable thermoplastic resin is injected into the cavity open in a trumpet shape inside of the light shielding layer  28  to mold the light guiding member  23  in close contact with the front of the lens portion  24 . 
   As described above, in the present embodiment, the light guiding member  23  is attached to the front of the lens portion  24  of the remote-control light receiving unit body  22  so as to be united with the lens portion  24 . Therefore, displacement between the light guiding member  23  and the lens portion  24  does not occur, and transmission signal light emitted from the light guiding member  23  is efficiently transferred to the lens portion  24 . 
   The order of injection molding the light guiding member  23  and the light shielding layer  28  may be opposite to the above-mentioned order, but if the light guiding member  23  is injection molded first, it is required that the mold be in close contact with not only the front of the lens portion  24  but also a part of the remote-control light receiving unit body  22 . 
   The above-mentioned production method forms the light guiding member  23  and the light shielding layer  28  by injection molding, but other molding methods such as transfer molding may be adopted. 
   Second Embodiment 
   In the above-described first embodiment, the light shielding layer  28  is formed directly on the periphery of the light guiding member  23 . In a second embodiment, a reflection layer is formed between the light guiding member  23  and the light shielding layer  28 , as shown in  FIG. 2 . In  FIG. 2 , components same as those of the first embodiment shown in  FIG. 1  are designated by the same numerals, and description thereof is omitted. 
   As described above, a remote-control light receiving unit  41  of the present embodiment has a reflection layer  42  between the light guiding member  23  and the light shielding layer  28 , the reflection layer  42  being of a material having a high reflectance (e.g., a silver colored infrared light blocking material). The provision of the reflection layer  42  can enhance the reflection of transmission signal light on the outer peripheral surface of the light guiding member  23 . Thus, possible absorption of the transmission signal light by the light shielding layer  28  while it is transferred through the light guiding member  23  is suppressed, so that the efficiency of transfer of the transmission signal light to the lens portion  24  can be improved. 
   If a black-colored infrared-transmitting light shielding layer  28  having a high light shielding effect or an infrared-absorbing light shielding layer  28  alone is used as in the first embodiment, the reflectance at an interface between the light guiding member  23  and the light shielding layer  28  becomes lower (because light is absorbed by the light shielding film  28 ). Therefore, the transfer efficiency of transmission signal light is lower and the reach of the transmission signal light from the remote-control transmitter is shorter. 
   Although the light shielding layer  28  and the reflection layer  42  have been described as being formed of different materials, a light shielding and reflection layer having both the light shielding effect and the reflectivity may be formed using a luster metallic colored (silver etc.) resin that does not transmit infrared light. 
   Third Embodiment 
   In both of the remote-control light receiving units  21 ,  41  of the first and second embodiments, the light receiving unit body  22  and the light guiding member  23  are integrally formed such that they are in close contact with each other. On the other hand, in a remote-control light receiving unit of a third embodiment, a remote-control light receiving unit body and a light guiding member are constructed as separate parts, though they are in close contact with each other. 
     FIG. 3  shows a longitudinal cross sectional view of the remote-control light receiving unit  51  of the third embodiment. In this case also, components same as those of the first embodiment shown in  FIG. 1  are designated by the same numerals, and description thereof is omitted. 
   A terminal end portion  54  of a light guiding member  53  is positioned in contact with or extremely close to an apex  52  of the lens portion  24  of the remote-control light receiving unit body  22 . The light guiding member  53  of the present embodiment also has a shape of combined circular cylinder and cone, similar to the light guiding member  23  of the first embodiment shown in  FIG. 1 , and the terminal end  54  of the light guiding member is an end surface of the circular cylinder. 
   A light shielding member  55  is placed so as to surround the circular cylinder portion of the light guiding member  53 . The light shielding layer  55  consists of a portion that covers surfaces of the remote-control light receiving unit body  22  other than a surface of the lens portion  24  and a surface  31  of a molded portion  29  from which input/output leads  30  protrude (i.e., the covered surfaces being a rear surface, side surfaces, a top surface and a front surface other than the lens portion  24 ), as in the light shielding layer  28  of the first embodiment shown in  FIG. 1 . Both of these portions are integrally molded. The light shielding member  55  contains conductive filler. 
   In the present embodiment, the light shielding member  55  has a circular cylinder shape so as to surround a circular cylinder portion of the light guiding member  53 , but it may be formed in a trumpet shape so as also to surround the conical portion of the light guiding member  53   
   The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.