Abstract:
An image sensor includes a substrate; a photosensitive die having an array of photosensitive sites for receiving incident light; wherein the substrate extends beyond a boundary of the photosensitive layer for forming a mounting surface; a support, which includes a receiving portion, mounted to the substrate and surround at least a portion of the array of photosensitive sites; a transparent layer mounted in the receiving portion of the support; an optical assembly through which the incident light passes and includes at least three mounting structures which are mounted respectively to one mounting location on the support and two mounting locations on the mounting surface of the substrate for aligning the assembly to the array of photosensitive sites.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to image sensors and, more particularly, to an optical assembly attached parallel or substantially parallel to an array of photosensitive sites of the image sensor to eliminate tilt of the optical assembly relative to the array of photosensitive sites. 
       BACKGROUND OF THE INVENTION 
       [0002]    Presently, image sensors include an array of photosensitive sites surrounded by an enclosing structure, typically made of plastic. Glass is mounted on the top of the enclosing structure, which in combination with the enclosing structure, totally encapsulates the array of photosensitive sites. 
         [0003]    Typically, a lens and/or a filter is placed over the image sensor for either directing the incident light toward the array of photosensitive sites or filtering the light or a combination of both directing and filtering incident light. The lens or filter is mounted to the plastic enclosing structure by mounting extensions for rigidly mounting the lens and/or filter. 
         [0004]    Although the presently known and utilized image sensor is satisfactory, it includes drawbacks. One drawback is that the mounting of the lens and/or filter to the plastic enclosing structure is not precise as desired and the lens and/or filter may tilt relative to the array of photosensitive sites. This causes the incident light to be directed inappropriately onto the array of photosensitive sites. 
         [0005]    Consequently, a need exists for improving the mounting of the lens and/or filter to the plastic enclosing structure so that tilting is eliminated or substantially eliminated within desired tolerances. 
       SUMMARY OF THE INVENTION 
       [0006]    It is therefore an object of the present invention to provide an image sensor in which the optical assembly is aligned in such a way as to eliminate or substantially eliminate tilt of the optical assembly relative to the array of photosensitive sites. 
         [0007]    This object is achieved by an image sensor having a substrate; a photosensitive die having an array of photosensitive sites for receiving incident light; wherein at least a portion of the substrate extends beyond a boundary of the silicon die for forming a mounting surface; a support, which includes a receiving portion, mounted to the substrate and surrounds at least a portion of the array of photosensitive sites; a transparent layer mounted in the receiving portion of the support; an optical assembly through which the incident light passes and includes at least three mounting structures which are mounted respectively to one mounting location on the support and two mounting locations on the mounting surface of the substrate for aligning the assembly to the array of photosensitive sites. 
       ADVANTAGES 
       [0008]    The present invention provides the advantage of eliminating undesirable tilt of the optical assembly relative to the array of photosensitive sites. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a top view of the image sensor of the present invention; 
           [0010]      FIG. 2  is a side view cut along line  2 - 2  of  FIG. 1 ; 
           [0011]      FIG. 3  is a side view cut along line  3 - 3  of  FIG. 1 ; 
           [0012]      FIG. 4  is a side view cut along line  4 - 4  of  FIG. 4 ; 
           [0013]      FIG. 5  is a top view of the image sensor of the present invention with the optical assembly removed; and 
           [0014]      FIG. 6  is a schematic in block diagram form of an image capture device of the present invention having the image sensor of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    Referring to  FIGS. 1 and 2 , there is shown an image sensor  10  having a substrate  20  on which is mounted a photosensitive die  30 , preferably silicon die, having an array of photosensitive sites  40  therein each for receiving incident light which releases charge in the silicon die in response to incident light, and the charge is captured respectively by each photosensitive site  40 . The array of photosensitive sites  40  may be either charge-coupled devices or complimentary metal oxide semiconductor (commonly referred to as CMOS) both well known in the art. CMOS refers to the fact that CMOS uses complementary and symmetrical pairs of p-type and n-type metal oxide semiconductor field effect transistors (MOSFETs) typically for logic functions. A plurality of microlenses  45  are disposed over the photosensitive sites  40  for further directing the light on the photosensitive sites  40 . It is noted that the photosensitive die  30  is placed and glued parallel to the substrate  20 . 
         [0016]    A support  50 , preferably plastic, extends around the periphery of the photosensitive sites  40  and typically completely surrounds the photosensitive site  40 . It is noted that a mating surface  59  of the plastic support  50  is placed and glued parallel to the substrate  20 . The support  50  includes a receiving portion  55 , preferably L-shaped, in which a transparent layer  60 , preferably glass, is placed in the receiving portion  55 . The transparent layer  60  is sealed to the receiving portion  55  by either glue, adhesive, epoxy or the like  58 . The transparent layer  60  and the support  50  encloses the photosensitive die  30  on its top and side with the substrate  20  enclosing it from the bottom. A plurality of wire bonds  70  each extend from the periphery of the photosensitive die  30  to the substrate  20  and are each connected to a solderpad  80  via metal contacts  90 , commonly referred to in the art as VIAs. The solderpads  80  permit the signal to be passed therefrom for further processing, as is well known in the art. 
         [0017]    An optical assembly  100 , which may be either a lens and/or a filter, is placed over the array of photosensitive sites  40  in the photosensitive die  30  and includes a mounting structure  120  having mounting extensions  110   a  and  110   b  (only two of which is visible in  FIG. 2 ). Referring to  FIG. 4 , the mounting extension  110   a  is rigidly attached to the support  50  at one location, and referring to  FIG. 3 , the two mounting extensions  110   b  are rigidly attached to the substrate  20  at two locations. Referring to  FIG. 5 , it is noted that attachment of the mounting extensions  110   b  to the substrate  20  is at a mounting location  115   b  which is located beyond the support  50 . The attachment of the mounting extension  110   a  is directly on the plastic support  50 . These locations  115   a  and  115   b  may be marked with fiducials for efficient aligning of the photosensitive die  30  and the optical assembly  100  thereon. 
         [0018]    Preferably, the location  115   a  on the plastic support  50  is substantially at a midpoint of the array of photosensitive sites  40  of the photosensitive die  30 , and preferably the two mounting locations  115   b  on the mounting surface of the substrate  20  are each substantially at an edge of the array of photosensitive sites  40  of the photosensitive die  30 . The placement of the optical assembly  100  to the array of photosensitive sites  40  is parallel or substantially parallel which alleviates tilting and the like. The two mounting locations  115   b  on the substrate  20  are aligned to the longer side of the image array. 
         [0019]    Referring to  FIG. 6 , there is shown a block diagram of an imaging system that can be used with the image sensor  10  in accordance with the present invention. Imaging system  1200  includes digital camera phone  1202  and computing device  1204 . Digital camera phone  1202  is an example of an image capture device that can use an image sensor incorporating the present invention. Other types of image capture devices can also be used with the present invention, such as, for example, digital still cameras and digital video camcorders. 
         [0020]    Digital camera phone  1202  is a portable, handheld, battery-operated device in an embodiment in accordance with the invention. Digital camera phone  1202  produces digital images that are stored in memory  1206 , which can be, for example, an internal Flash EPROM memory or a removable memory card. Other types of digital image storage media, such as magnetic hard drives, magnetic tape, or optical disks, can alternatively be used to implement memory  1206 . 
         [0021]    Digital camera phone  1202  uses optical assembly  100  to focus light from a scene (not shown) onto the image sensor array  10  of pixel sensor  1212 . Image sensor array  10  provides color image information using the Bayer color filter pattern in an embodiment in accordance with the invention. Image sensor array  10  is controlled by timing generator  1214 , which also controls flash  1216  in order to illuminate the scene when the ambient illumination is low. 
         [0022]    The analog output signals output from the image sensor array  10  are amplified and converted to digital data by analog-to-digital (A/D) converter circuit  1218 . The digital data are stored in buffer memory  1220  and subsequently processed by digital processor  1222 . Digital processor  1222  is controlled by the firmware stored in firmware memory  1224 , which can be flash EPROM memory. Digital processor  1222  includes real-time clock  1226 , which keeps the date and time even when digital camera phone  1202  and digital processor  1222  are in a low power state. The processed digital image files are stored in memory  1206 . Memory  1206  can also store other types of data, such as, for example, music files (e.g. MP3 files), ring tones, phone numbers, calendars, and to-do lists. 
         [0023]    In one embodiment in accordance with the invention, digital camera phone  1202  captures still images. Digital processor  1222  performs color interpolation followed by color and tone correction, in order to produce rendered sRGB image data. The rendered sRGB image data are then compressed and stored as an image file in memory  1206 . By way of example only, the image data can be compressed pursuant to the JPEG format, which uses the known “Exif” image format. This format includes an Exif application segment that stores particular image metadata using various TIFF tags. Separate TIFF tags can be used, for example, to store the date and time the picture was captured, the lens f/number and other camera settings, and to store image captions. 
         [0024]    Digital processor  1222  produces different image sizes that are selected by the user in an embodiment in accordance with the invention. One such size is the low-resolution “thumbnail” size image. Generating thumbnail-size images is described in commonly assigned U.S. Pat. No. 5,164,831, entitled “Electronic Still Camera Providing Multi-Format Storage Of Full And Reduced Resolution Images” to Kuchta, et al. The thumbnail image is stored in RAM memory  1228  and supplied to color display  1230 , which can be, for example, an active matrix LCD or organic light emitting diode (OLED). Generating thumbnail size images allows the captured images to be reviewed quickly on color display  1230 . 
         [0025]    In another embodiment in accordance with the invention, digital camera phone  1202  also produces and stores video clips. A video clip is produced by summing multiple pixels of image sensor array  10  together (e.g. summing pixels of the same color within each 4 column×4 row area of the image sensor array  10  to create a lower resolution video image frame. The video image frames are read from image sensor array  1210  at regular intervals, for example, using a 15 frame per second readout rate. 
         [0026]    Audio codec  1232  is connected to digital processor  1222  and receives an audio signal from microphone (Mic)  1234 . Audio codec  1232  also provides an audio signal to speaker  1236 . These components are used both for telephone conversations and to record and playback an audio track, along with a video sequence or still image. 
         [0027]    Speaker  1236  is also used to inform the user of an incoming phone call in an embodiment in accordance with the invention. This can be done using a standard ring tone stored in firmware memory  1224 , or by using a custom ring-tone downloaded from mobile phone network  1238  and stored in memory  1206 . In addition, a vibration device (not shown) can be used to provide a silent (e.g. non-audible) notification of an incoming phone call. 
         [0028]    Digital processor  1222  is connected to wireless modem  1240 , which enables digital camera phone  1202  to transmit and receive information via radio frequency (RF) channel  1242 . Wireless modem  1240  communicates with mobile phone network  1238  using another RF link (not shown), such as a 3GSM network. Mobile phone network  1238  communicates with photo service provider  1244 , which stores digital images uploaded from digital camera phone  1202 . Other devices, including computing device  1204 , access these images via the Internet  1246 . Mobile phone network  1238  also connects to a standard telephone network (not shown) in order to provide normal telephone service in an embodiment in accordance with the invention. 
         [0029]    A graphical user interface (not shown) is displayed on color display  1230  and controlled by user controls  1248 . User controls  1248  include dedicated push buttons (e.g. a telephone keypad) to dial a phone number, a control to set the mode (e.g. “phone” mode, “calendar” mode” “camera” mode), a joystick controller that includes 4-way control (up, down, left, right) and a push-button center “OK” or “select” switch, in embodiments in accordance with the invention. 
         [0030]    Dock  1250  recharges the batteries (not shown) in digital camera phone  1202 . Dock  1250  connects digital camera phone  1202  to computing device  1204  via dock interface  1252 . Dock interface  1252  is implemented as wired interface, such as a USB interface, in an embodiment in accordance with the invention. Alternatively, in other embodiments in accordance with the invention, dock interface  1252  is implemented as a wireless interface, such as a Bluetooth or an IEEE 802.11b wireless interface. Dock interface  1252  is used to download images from memory  1206  to computing device  1204 . Dock interface  1252  is also used to transfer calendar information from computing device  1204  to memory  1206  in digital camera phone  1202 . 
         [0031]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. 
       PARTS LIST 
       [0000]    
       
           10  image sensor array 
           20  substrate 
           30  photosensitive die 
           40  photosensitive sites 
           45  microlenses 
           50  plastic support 
           55  receiving portion 
           58  glue or adhesive 
           59  mating surface 
           60  transparent layer or glass 
           70  wire bonds 
           80  solderpads 
           90  metal contacts or VIAs 
           100  optical assembly 
           110   a  mounting extensions 
           110   b  mounting extensions 
           115   a  mounting location 
           115   b  mounting location 
           120  mounting structure 
           1200  imaging system 
           1202  digital camera phone 
           1204  computing device 
           1206  memory 
           1210  image sensor array 
           1212  pixel sensor 
           1214  timing generator 
           1216  flash 
           1218  A/D converter circuit 
           1220  buffer memory 
           1222  digital processor 
           1224  firmware memory 
           1226  clock 
           1228  RAM memory 
           1230  color display 
           1232  audio codec 
           1234  microphone 
           1236  speaker 
           1238  mobile phone network 
           1240  wireless modem 
           1242  RF Channel 
           1244  photo service provider 
           1246  Internet 
           1248  user controls 
           1250  dock 
           1252  dock interface