Patent Publication Number: US-2010116970-A1

Title: Photo detection device

Description:
FIELD OF THE INVENTION 
     The present invention relates to a photo detection device, and in particular to a photo detection device that eliminates the influence on a photo detection die by long wavelength invisible lights, such as infrared light to ensure high detection reliability of visible lights and that is applicable to a photo sensor or the likes. 
     BACKGROUND OF THE INVENTION 
     Conventional photo detection devices comprise photo detection dies that are exposed outside the devices or are housed by light-transmitting plastic materials, such as epoxy resin. Consequently, the photo detection die receives both visible lights and invisible lights from all directions. In certain applications of the photo detection device, it is desired to detect if the device is radiated by visible lights by using the photo detection die and to further transmit the result of detection to other devices to induce a corresponding operation. For example, in the application in an automobile, when the automobile travels through a tunnel or an area of insufficient lighting, a central control of the automobile may receive the detection result provided by a photo detection device mounted outside the automobile body to signal the driver of the automobile to turn on the automobile lights or to perform automatic actuation of the automobile lights in order to ensure driving safety. 
     A conventional photo detection device A (see  FIG. 6 ) comprises a photo detection die A 1 , which has a surface formed with a coating layer. In practice, the photo detection die A 1  is housed in a light-transmitting plastic material A 2  to allow the photo detection die A 1  to receive light B that includes both visible components and invisible components from various directions and angles. When an incident light component of the light B having a long wavelength, such as an infrared light, transmits through the coating layer formed on the surface of the photo detection die A 1 , error detection is caused to give an incorrect result of detection, so that a device that receives the incorrect result of detection cannot respond properly. 
     To solve the problems of the conventional photo detection device A, the present inventor conducted extensive study and research and performed experiments that reveal that the photo detection die A 1  provided different result of detection when receiving long wavelength incident lights (such as an invisible light, for example an infrared light) from different angles. It is also found that the greater an incidence angle of a long wavelength incident light (such as an invisible light, for example an infrared light), the more easily the light transmits through the surface coating layer of the photo detection die A 1  to be detected by the photo detection die A 1 , causing error detection, wherein the term “incidence angle” used here is defined as an included angle between an incident light beam and a line perpendicular to the surface of the photo detection die, namely an included angle between the incident light beam and the normal of the surface of the photo detection die. The present invention provides a solution to improve the conventional photo detection device A on the basis of the above observation. 
     SUMMARY OF THE INVENTION 
     An objective of the present invention is to provide a photo detection device, which reduces error detection caused by a long wavelength incident light (such as an invisible light, for example an infrared light) transmitting through a surface coating layer of a photo detection die by means of providing an assembly comprising the photo detection die housed in a non-light-transmittable enclosure with the enclosure forming an opening for the transmission of the light to limit the incidence angle by which the photo detection die receives the light, so as to improve detection reliability of visible lights and thus enhance the practicability of the present invention. 
     Another objective of the present invention is to provide a photo detection device, which reduces error detection caused by a long wavelength component (such as an infrared component) contained in an incident light that transmits through a coating layer of a photo detection die due to a large incidence angle thereof by means of providing an assembly comprising the photo detection die housed in a non-light-transmittable enclosure that forms an opening for the transmission of the light, wherein the opening is made size-reduced for reducing the incidence angle, so as to improve detection reliability and thus enhance the practicability of the present invention. 
     A further objective of the present invention is to provide a photo detection device, which reduces error detection caused by a long wavelength component of an incident light, such as an infrared component, that transmits through a coating layer of a photo detection die due to a large incidence angle thereof by means of providing an assembly comprising the photo detection die housed in a non-light-transmittable enclosure that forms an opening for the transmission of the light and has an increased height to increase the distance between the opening and the photo detection die for reducing the incidence angle by which the incident light that enters the enclosure is incident onto the photo detection die, so as to improve detection reliability and thus enhance the practicability of the present invention. 
     Yet a further objective of the present invention is to provide a photo detection device, which effectively reduces the reflection of a long wavelength incident light (such as an invisible light, for example an infrared light) by a photo detection die by providing an assembly comprising the photo detection die housed in a non-light-transmittable enclosure that forms an opening for the transmission of the light with a coating layer that is formed by either a layer of titanium dioxide (TiO 2 ), a layer of silicon dioxide (SiO 2 ), a stack of at least one layer of titanium dioxide (TiO 2 ) and at least one layer of silicon dioxide (SiO 2 ), or a Bragg reflection film being provided on the photo detection die, so as to reduce the occurrence of error detection and improve detection reliability to thereby enhance the practicability of the present invention. 
     To realize the above objectives, the present invention provides a photo detection device comprising two lead frames, a photo detection die, and an enclosure. The two lead frames include a first lead frame and a second lead frame. The first lead frame forms a carriage section. A coating layer is formed on the photo detection die. The photo detection die is mounted on the carriage section of the first lead frame and forms electrical connection with the second lead frame through a conductor. The enclosure is a non-light-transmittable member forming therein a receiving space. The enclosure is mounted on the first and second lead frames and receives the photo detection die in the receiving space thereof. The enclosure forms an opening for light detection by the photo detection die. As such, detection of a long wavelength invisible light, such as an infrared light, by the photo detection die can be prevented to thereby provide a photo detection device with increased reliability of detection. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be apparent to those skilled in the art by reading the following description of preferred embodiments thereof with reference to the drawings, in which: 
         FIG. 1  is a perspective view illustrating a photo detection device in accordance with the present invention; 
         FIG. 2  is a cross-sectional view illustrating a first embodiment of a coating layer of a photo detection die incorporated in the photo detection device in accordance with the present invention; 
         FIG. 3  is a cross-sectional view illustrating a second embodiment of a coating layer of a photo detection die incorporated in the photo detection device in accordance with the present invention; 
         FIG. 4  is a perspective view illustrating a photo detection device in accordance with another embodiment of the present invention; 
         FIG. 5  is a perspective view illustrating a photo detection device in accordance with a further embodiment of the present invention; and 
         FIG. 6  is a schematic view illustrating the operation of a conventional photo detection device. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to  FIGS. 1-4 , a photo detection device constructed in accordance with the present invention comprises two lead frames, a photo detection die  30 , and an enclosure  40 . The two lead frames include a first lead frame  10  and a second lead frame  20 . The first lead frame  10  forms a carriage section  101 . The photo detection die  30  is provided with a coating layer  31 . The photo detection die  30  is mounted on the carriage section  101  of the first lead frame  10  and the photo detection die  30  forms electrical connection with the second lead frame  20  by means of a conductor  32 . The enclosure  40  is a non-light-transmittable member and forms therein a receiving space  401 . The enclosure  40  is mounted on the first lead frame  10  and the second lead frame  20  and receives the photo detection die  30  in the receiving space  401  thereof. The enclosure  40  has a top wall (not labeled) forming an opening  41 , whereby light is allowed to transmit into the interior of the enclosure  40  through the opening  41  of the enclosure  40  to be detected by the photo detection die  30 . In this way, an angle by which an invisible light of a long wavelength, such as an infrared light, is incident on the photo detection die  30  can be reduced so as to prevent the photo detection die  30  from detecting the long wavelength invisible light, such as an infrared light, whereby a photo detection device with high detection reliability is realized. 
     A shown in  FIG. 2 , the coating layer  31  provided on the photo detection die  30  is to reflect the long wavelength invisible light, such as infrared light. The coating layer  31  is formed by a layer of titanium dioxide (TiO 2 ) or a layer of silicon dioxide (SiO 2 ); or alternatively, as shown in  FIG. 3 , the coating layer  31  is formed of at least one layer of titanium dioxide (TiO 2 ) and at least one layer of silicon dioxide (SiO 2 ) that are stacked over each other; or further alternatively, the coating layer  31  can be a Bragg reflection film, whereby reflection of for example the long wavelength invisible light, such as an infrared light, can be enhanced. The enclosure  40  is made of a light-reflecting or non-light-transmitting material comprising a light absorption material or a light reflection material, such as metals. The enclosure  40  is formed as a sleeve for fitting over the photo detection die  30  with the opening  41  formed in the top wall of the enclosure  40  limiting the angle that light projects into the interior of the enclosure  40 . 
     Researches and experiments conducted by the present inventor reveal that when the incidence angle of light is less than 20 degrees, a long wavelength invisible component of an incident light, such as an infrared component, can be reflected by the coating layer  31  of the photo detection die  30 . The term “incidence angle” used herein is defined as an included angle between an incident light beam and a line perpendicular to a surface of the photo detection die  30 , namely an included angle between the incident light beam and the normal of the surface of the photo detection die  30 . The experiments also show that with the incidence angle of the long wavelength invisible light, such as infrared light, getting greater, the long wavelength invisible light can transmit through the coating-layer  31  of the photo detection die  30  more easily to be detected by the photo detection die  30 . Thus, based on the result of the experiments, the photo detection device can be improved by reducing the incidence angle of the incident light beam in order to reduce the possibility of error detection of the photo detection die  30  caused by long wavelength invisible light components. 
     As shown in  FIG. 4 , in a practical application, the opening  41  of the enclosure  40  can be made smaller to further reduce the incidence angle by which a light is incident onto the photo detection die  30  by transmitting through the opening  41  of the enclosure  40  to get into the enclosure  40 . Alternatively, the height of the enclosure  40  can be increased, namely increasing the vertical distance between the opening  41  of the top wall of the enclosure  40  and the photo detection die  30  set inside the enclosure  40 , to achieve the same result of limiting the incidence angle of the incident light into the enclosure  40  within a given range, whereby the situation that the long wavelength invisible components of the incident light cannot be effectively reflected by the coating layer  31  on the surface of the photo detection die  30  due to large incidence angles can be avoided. Both arrangements of reducing the opening  41  of the enclosure  40  and increasing the height of the enclosure  40  can be practiced individually or in combination to realize the purpose of the present invention. 
     Referring to  FIGS. 1-4 , the present invention features a combination of the first and second lead frames  10 ,  20 , the photo detection die  30  and the enclosure  40  with the enclosure  40  shielding the photo detection die  30  and forming an opening  41  for the transmission of light therethrough, whereby the incidence angle of the light received by the photo detection die  30  is limited in order to prevent error detection caused by a long wavelength invisible component of the incident light, such as an infrared light component, being not reflected by and transmitting through the coating layer  31  of the photo detection die  30  due to the large incidence angle thereof, thereby enhancing the detection reliability of the photo detection die  30 . Further, by further reducing the size of the opening  41  of the enclosure  40 , the light transmitting through the opening  41  of the enclosure  40  is only allowed to have a reduced incidence angle with respect to the photo detection die  30 , whereby the same problem of error detection caused by a long wavelength invisible component of the incident light, such as an infrared light component, transmitting through the coating layer  31  of the photo detection die  30  due to the large incidence angle thereof is avoided. Further, the present invention also provides a solution of increasing the height of the enclosure  40 , which leads to an increased distance between the opening  41  of the enclosure  40  and the photo detection die  30 , which in turn reduces the angle by which the incident light transmitting into the enclosure  40  is projected onto the photo detection die  30 , whereby the problem of error detection of the photo detection die  30  caused by a long wavelength invisible component of the incident light, such as an infrared light component, transmitting through the coating layer  31  of the photo detection die  30  due to the large incidence angle thereof is avoided. Also, with the coating layer  31  of the photo detection die  30  being formed by a layer of titanium dioxide (TiO 2 ) or a layer of silicon dioxide (SiO 2 ) or a stack of at least one layer of titanium dioxide (TiO 2 ) and at least one layer of silicon dioxide (SiO 2 ), or a Bragg reflection film, reflection of long wavelength invisible lights, such as an infrared light, effected by the photo detection die  30  can be enhanced, whereby error detection can be further reduced to improve the detection reliability of visible lights. 
     Further, although the photo detection device of the present invention as shown in  FIGS. 1-4  is embodied in a DIP (Dual In-line Package) package, wherein the photo detection device comprises a combination of two lead frames (namely the first lead frame  10  and the second lead frame  20 ), a photo detection die  30 , and a enclosure  40 , yet it is possible to embody the present invention in an SMD (Surface Mount Device) package, as illustrated in  FIG. 5 , wherein the SMD packaged photo detection device in accordance with the present invention comprises a base  1 , a photo detection die  30 , and a enclosure  40 . The base  1  is provided with two lead frames, which are set in a bent configuration and extend from inside the base  1  to get beyond opposite sides of the base  1 . The two lead frames include a first lead frame  10  and a second lead frame  20 . The first lead frame  10  forms a carriage section  101 . The photo detection die  30  is provided with a coating layer  31 . The photo detection die  30  is mounted on the carriage section  101  of the first lead frame  10  and the photo detection die  30  forms electrical connection with the second lead frame  20  by means of a conductor  32 . The enclosure  40  is a non-light-transmittable member and forms therein a receiving space  401 . The enclosure  40  is mounted on the base  1  and receives the photo detection die  30  in the receiving space  401  thereof. The enclosure  40  has a top wall (not labeled) forming an opening  41  to allow light to be detected by the photo detection die  30 . Similar to the embodiments described with reference to  FIGS. 1-4 , the coating layer  31  can be formed by for example any of a layer of titanium dioxide, a layer of silicon dioxide, a stack of at least one layer of titanium dioxide and at least one layer of silicon dioxide, and a Bragg reflection film. Further, the enclosure  40  can be made of a light reflection material, such as metals, or a light absorption material. Further, similar to what discussed above in the previous embodiments, the opening  41  of the enclosure  40  can be reduced in size and/or the height of the enclosure  40  increased to enhance reflection of a long wavelength invisible light, such as an infrared light, effected by the photo detection die  30  to thereby reduce the occurrence of error detection and improve the detection reliability of the visible light. 
     Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.