Abstract:
An image capture apparatus and a method of image processing. The apparatus includes an image sensor array which receives light that has been reflected by a scene, a luminance photodetector which receives light from a luminance channel, a multifunction lens, and a processor. The multifunction lens includes an imaging lens portion and the luminance channel. The imaging lens portion directs the light that has been reflected in a first direction onto the image sensor array. The luminance channel includes an optical element which directs the light from the luminance channel in a second direction different from the first direction onto the luminance photodetector. The image sensor array and the luminance photodetector each convert the light they receive to image data electrical signals and luminance data electrical signals, respectively. The processor processes the image data electrical signals to form an image of the scene using the luminance data electrical signals.

Description:
This application is a Continuation of U.S. application Ser. No. 10/266,538, filed Oct. 7, 2002, now U.S. Pat. No. 7,414,662, issued on Aug. 19, 2008, the contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention relates to digital imaging systems. More particularly, the present invention relates to a digital imaging system including a multifunction lens. 
     Digital imaging devices capture a scene as an image defined by a set of digital values. The captured image (as a set of digital values) can be processed for various applications. For example, to improve the quality of reproduction, various processing techniques such as flicker correction and color balancing can be applied to a captured image. To apply these techniques, information is required regarding the lighting, or luminance, of the scene at the time the scene is captured by the imaging device. 
     To obtain the luminance information, a light meter can be used to measure the light impinging upon the image. However, the light meter, as a separate device, does not measure the luminance of the scene at the exact instant that the scene is captured. Further, the luminance information obtained by the light meter is not immediately available to the imaging device. Some imaging devices include a built-in luminance metering system including a luminance detector and a luminance detector lens system. In such devices the luminance detector and the luminance detector lens system are separate from the main imaging sensor and imaging lens. According, the addition of the luminance detector and the luminance detector lens system to the imaging device increases costs of manufacture, increases bulk to the imaging system, and decreases reliability of the imaging system due to having additional components 
     Consequently, there remains a need for an improved luminance detection system for imaging devices. 
     SUMMARY 
     These needs are met by the present invention. According to one aspect of the present invention, an image capture apparatus includes a multifunction lens having an imaging lens portion adapted to focus a scene onto an image sensor array and a luminance channel portion adapted to channel luminance of the scene toward a luminance photo detector. 
     According to another aspect of the invention, a multifunction lens includes an imaging lens portion adapted to focus a scene onto an image sensor array and a luminance channel portion adapted to channel luminance of the scene toward a luminance photo detector. 
     According to yet another aspect of the invention, a method of capturing an image includes the steps of capturing a scene through a multifunction lens and capturing luminance of said scene through the multifunction lens. 
     Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross sectional side view of an apparatus according to one embodiment of the present invention; 
         FIG. 2  is a cross sectional side view of a portion of the apparatus of  FIG. 1  with additional illustrations; 
         FIG. 3  is a cross sectional side view of a portion of an apparatus according to another embodiment of the present invention; and 
         FIG. 4  is a front view of a portion of the apparatus of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     As shown in the exemplary drawings and discussions herein below, the present invention is embodied in an image capture apparatus with a multifunction lens. The multifunction lens includes an imaging lens portion adapted to focus a scene onto an image sensor array and a luminance channel portion adapted to channel luminance of said scene toward a luminance photo detector. Due to a single piece design of the multifunction lens of the present invention, compared to the prior art built-in luminance metering system, the costs of manufacture are decreased, bulk to the imaging system is decreased, and reliability of the imaging system is increased. 
       FIG. 1  is a cross sectional side view of an image capture apparatus  100  in accordance with one embodiment of the present invention. The following drawings are not necessarily to scale. This is done in order to more clearly illustrate the invention. The image capture apparatus  100  can be for example a digital camera, a cellular phone camera, a personal digital assistant camera, or a camcorder. The image capture apparatus  100  includes a processor  102 , a memory  104  connected to the processor  102 , an image sensor array  107  connected to an analog to digital (AD) converter  105 , and a luminance photo detector  108  connected to an analog to digital converter  109 . The analog to digital converters  105  and  109  are connected to the processor  102 . One or more of these listed elements can be fabricated over a single substrate  106 . In the illustrated embodiment, for example, the image sensor array  107 , the luminance photo detector  108 , and the analog to digital converters  105  and  109  are fabricated over the substrate  106 . The image capture apparatus  100  further includes a multifunction lens  110 . 
     The multifunction lens  110  has two portions. The first portion is an imaging lens portion  120 . The imaging lens portion  120  is adapted to focus light from a scene to the image sensor array  107 . The image sensor array  107  captures the scene as an image by converting the light into electrical signals. The electrical signals are converted into digital values by the analog to converter  105 . The converted digital values are sent to the processor  102 . The processor stores the image, as a set of digital values (image data), in the memory  104 . 
     The second portion of the multifunction lens  110  is a luminance channel portion  130 . The luminance channel portion  130  is adapted to channel light onto the luminance photo detector  108 . The luminance photo detector  108  is adapted to detect the channeled light by converting the channeled light into electrical signals. The electrical signals are converted into digital values by the analog to digital converter  109 . The converted digital values (luminance data) are sent to the processor  102 . The luminance data can be used to process the image data. For example, the luminance data can be used to apply automatic white balance, flicker detection and correction to the image data and perform luminance metering. The luminance photo detector  108  can be fabricated proximal to the image sensor array  107 . The luminance photo detector  108  can be fabricated at the same time as the image sensor array  107  and on the same substrate  106 . 
       FIG. 2  includes a cross sectional side view of portions of the image capture apparatus  100  of  FIG. 1 . Further,  FIG. 2  illustrates a luminance source  111  and a sample scene  114 . The scene  114  is shown, only for the purpose of illustration, as a tree  114 . The scene  114  can be any scene captured by the image capture device  100 . The luminance source  111  can be any source of light, for example sunlight, incandescent light, florescent light, or halogen light. The luminance source typically  111  emits light in many directions. A first portion of the light (illustrated as vector  112 ) from the luminance source  111  can be received by the luminance channel portion  130 . A second portion of the light (illustrated as vector  113 ) from the luminance source  111  is directed toward the scene  114 . The second portion of the light  113  is reflected by the scene  114  toward the multifunction lens  110 . A first portion of the reflected light (illustrated as vector  115 ) is directed toward the imaging lens portion  120 . A second portion of the reflected light (illustrated as vector  116 ) is directed toward the luminance channel portion  130 . Vectors  112  through  116  and other vectors used in  FIGS. 1-4  illustrate general directions of light to aid the discussion of the present invention, and are not intended to represent ray traces as is often used in the art of optics. 
     The first portion of the reflected light  115  enters the imaging lens portion  120  through an aperture  122 . The aperture  122  focuses the reflected light  115  onto the image sensor array  107  that captures the image as already discussed. 
     The second portion of the reflected light  116  is received by the luminance channel portion  130 . The luminance channel portion  130  includes a luminance channel lens  132  adapted to receive the second portion of the reflected light  116  and a luminance channel pipe  134  adapted to channel, or pipe, the received light toward the luminance photo detector  108 . The luminance channel lens  132  can include a convex surface, as illustrated, to increase the amount of light received by the luminance channel lens  132  and to direct the received light toward the luminance channel pipe  134 . For convenience, light received by the luminance channel lens  132  is illustrated as received light  117 . The luminance channel pipe  134  has total internal reflection such that all received light  117  is channeled to the detector  108 . 
     In  FIG. 2 , both the imaging lens  120  and the luminance channel portion  130  are directed in a first direction (illustrated by vector  144 ) toward the scene  114 . However, this is not required.  FIG. 3  illustrates another embodiment of the present invention wherein the luminance channel portion  130  is directed in a second direction (illustrated by vector  146 ), different than the first direction  144 . 
     An embodiment of the present invention having a certain alternate configuration is shown in  FIG. 3 . Portions of this embodiment are similar to those shown in  FIG. 2 . For convenience, components in  FIG. 3  that are similar to components in  FIG. 2  are assigned the same reference numerals while analogous but changed components are assigned the same reference numerals accompanied by a letter “a”. Different components are assigned different reference numerals. 
       FIG. 3  illustrates another embodiment of the present invention including the multifunction lens  110   a  having a luminance channel portion  130   a . The luminance channel portion  130   a  is directed toward the second direction  146 . Here, the first direction  114  is generally toward the scene  114  and the second direction  146  is generally toward a luminance source  111   a . In the illustrated embodiment, the second direction  146  is normal to the first direction  144 . However, the second direction  146  can be any direction including, as illustrated in  FIG. 2 , the same direction as the first direction  146 . In  FIG. 3 , the luminance source  111   a  is illustrated as having a position over the multifunction lens  110  which may be the case in some instances. To direct the received light  117   a  to the luminance photo detector  108 , an optic element  142  such as a mirror may be used within the luminance channel portion  130   a.    
       FIG. 4  illustrates a front view of the multifunction lens  110  in accordance to one embodiment of the present invention as illustrated in  FIGS. 1 and 2 . Referring to  FIGS. 1 ,  2 , and  4 , the multifunction lens  110  can include one or more support legs. In  FIG. 4 , the multifunction lens  110  is illustrated having three support legs  118 ,  119 , and  130  with the support leg  130  also configured and operating as the luminance channel portion  130 . In fact, each of the other support legs — 118  and  119 —can also be configured to function as a luminance channel. 
     In  FIGS. 1 ,  2 , and  4 , the luminance channel portion  130  is illustrated as having generally a cylindrical shape with the luminance channel lens  132  at one end of the cylinder (that is luminance channel portion  130 ) and the luminance photo detector  108  at the other end of the cylinder. The diameter, or thickness, of the luminance channel portion  130 , the luminance channel pipe  134 , or both can vary depending on implementation. For example, these portions can have a thickness ranging from 10 microns to 2000 microns. The luminance channel pipe  134  has a height that is substantially similar to the focal length  140 . In fact, in the illustrated embodiment, height of the support legs  118 ,  119 , and  130  is substantially similar to focal length  140  of the imaging lens  120 . This is often the case for fixed focus imaging lens portion  120 . 
     Luminance information received by the multifunction lens and detected by the luminance photo detector  108  is often used for improving the image data. For example, the luminance information can be used for metering the luminance of the scene  114 . Further, the luminance information can be used to detect various flicker parameters such as flicker frequency, flicker levels, or both. Such flicker may be result of luminance source having an alternating-current (AC) power source having, for example, 60 Hz (in the U.S.) or 50 Hz (in Europe). Another use of the luminance information is white balancing of the captured image. In order to perform white balancing on the captured image, three luminance photo detectors can be used to detect red, green, and blue components of the luminance light. This alternative embodiment can be discussed using  FIG. 4 . 
     In an alternative embodiment, each of the support legs  118 ,  119 , and  130  of the multifunction lens  110  can be configured as a luminance channel directing luminance information to a photo detector associated with the combined support leg-luminance channel. Further the photo detectors associated with the support legs-luminance channels  118 ,  119 , and  130  can be configured for detection of light at a particular frequency range. For example, the detector  108  (illustrated in  FIG. 1 ) associated with the support leg-luminance channel  130  can be adapted to detect light in a first frequency range (for example, around red color spectrum), a second detector (not illustrated) associated with the support leg-luminance channel  118  and be adapted to detect light in a second frequency range (for example, around green color spectrum), and a third detector (not illustrated) associated with the support leg-luminance channel  119  and be adapted to detect light in a third frequency range (for example, around blue color spectrum). Then, using the luminance information received by the support legs-luminance channels  118 ,  119 , and  130  and detected by the luminance photo detectors (detector  130 , the second detector, and the third detector discussed above), the captured image can be processed for color balancing. In another alternative embodiment, three or more photo detectors (for capture of Red, Green, and Blue components as well as other aspects of the luminance) can be fabricated under the single luminance channel portion  130 . 
     From the foregoing it will be appreciated that the multifunction lens provided by the invention provides an efficient, reliable, and cost effective means of measuring luminance of a scene. The present invention integrates an imaging lens with a luminance channel lens in a relatively simple manner. In the preceding detailed description, references are made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The preceding detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims. In the following, claims drafted to take advantage of the “means or steps for” provision of 35 USC section 112 are identified by the phrase “means for.”