1. Field of the Invention
The present invention relates generally to optical camera systems. More specifically, the present invention relates to optical camera systems using integrated circuits (ICs) which integrate two or more separate imaging pixel arrays on a single IC chip.
2. Discussion of the Related Art
An optical camera system typically includes an optical lens or lens system, and light sensing elements. The light sensing elements can be either traditional film or integrated circuit sensors fabricated by any of a number of manufacturing processes, such as CMOS (complementary metal-oxide semiconductor) or CCD (charge-coupled device) process. Such light sensing ICs traditionally have light sensing elements, called pixels, arranged in a single one-dimensional (e.g., one row) or two-dimensional (e.g., many rows and columns) array. The pixel array is aligned with the image formed by the optical lens system and position within the focus depth of the optical system while each pixel provides an electrical output corresponding to the intensity of the incident light to which the pixel is exposed.
In a typical simple camera system, one image of an object is captured using a sensor chip having a pixel array. However, many applications require forming multiple images of the same object or forming multiple images of different objects. Such applications require using multiple cameras or, alternatively, a camera system with multiple sensor arrays. For example, a professional studio camcorder uses three sensor arrays to separately capture red, green, and blue images. As another example, a panoramic imaging system (e.g., that described in U.S. patent application Ser. No. 11/624,209) uses several sensor arrays to provide overlapping fields of view, so that a composite image may encompass a full 360° field of view.
For such applications, a conventional imaging system uses multiple single-array image sensor chips (e.g., CCD or CMOS sensors), with each sensor chip having a 2-dimensional pixel array located typically near the center of the sensor chip. In that arrangement, each sensor chip is fabricated separately and has its own signal processing chain, a digital image-processing pipeline or both. These chips are aligned and positioned carefully to accommodate the image-forming lens system. As a result, such a system has large power consumption due to duplicated signal chains on the chips. Such a system is also more complex and bulky due to difficulty in aligning multiple chips, and may be more costly to produce.
There is therefore a need for a simpler and more compact camera system that can take in multiple images.
The present invention provides a simpler and more compact camera system for capturing multiple images.
The present invention provides a camera system that uses one or more image sensor IC chips each having multiple pixel arrays on the same semiconductor substrate (i.e., “multiple pixel arrays on a chip”). In one embodiment, such a camera system includes: (a) optical components that create multiple images in close physical proximity of each other (e.g., within a few millimeters or centimeters); and (b) a single sensor substrate (“chip”) containing multiple 2-dimensional pixel arrays that are aligned to capture these multiple images, so as to convert the multiple images into electrical signal. The pixel arrays can be manufactured using a CCD or a CMOS compatible process. For manufacturing reasons, such a chip is typically two centimeters or less on a side. However, large chips can also be made.
Optional electronic components for further signal processing of the captured images may be formed either on the sensor chip (i.e., in a “system-on-a-chip” implementation), or in a separate back-end application specific integrated circuit (ASIC). In addition, digital storage components, display elements, and wired or wireless communication links may also be included in any suitable combination to allow review and further processing of the captured images.
Compared to a conventional imaging system using multiple cameras or multiple image sensors, the present invention provides several advantages, such as a more compact design, easier fabrication, lower power, and a lower manufacturing cost. Other features and advantages of the present invention will become more readily apparent after reviewing the following detailed description and the accompanying drawings.
The present invention provides a camera system having multiple pixel arrays on a semiconductor substrate (“on the chip”).
In camera system 100, multiple sensor chips 121, 122, and 123 can be the same kind or different kinds of integrated circuit chips. An example of such an image sensor chip is provided in
In conventional camera system as system 100 of
By a proper design, one can align the different image planes of optical system 110 to form a single plane. With such a design, multiple discrete image sensors may be placed on a common PC board to allow multiple images be recorded, with each image sensor recording a single image. In such a system, the size of the overall system is determined by how closely the active regions of the sensors may be packed together. A number of factors limit the packing density. First, the peripheral circuits (e.g., timing and control circuit 220, readout chain 230 and I/O ring 240) on each image sensing chip occupy space around each sensor array 210. The mechanical tolerances for wafer dicing and chip packaging must also be taken into account. Additionally, gaps are required on the PCB between sensor packages to allow reliably board assembly. Typically, each package has its own power, ground, and data pins. The closer the packages are placed relative to each other, the more difficult it is to route the interconnect signals on the PCB. Finally, each image sensor may require multiple power supply bypass capacitors, which must be placed close to the power pins. With so many constraints, size reduction in such a conventional camera system is difficult.
In principle, a sufficiently large conventional image sensor chip having a large pixel array can record images from multiple optical objectives onto a single light-sensing region. In such a case, the image sensor does not limit how closely the images can be packed together. Further, all the images in such a system share a common package, integrated power bus, signal processing circuitry and signal I/O pins. Therefore, the overall pin-count and the capacitor-count on the PCB are reduced. However, the mechanical and optical constraints still limit how closely the images can be packed on the sensor. As a result, many pixels cannot be used to form the resulting images. These unused pixels waste power and occupy precious chip real estate that may otherwise be used to provide other sensor functions.
Optical system 310 can have multiple elements for creating multiple images of the same object or of different objects. As shown in
The pixel arrays of image chip 330 can be manufactured using either a CCD or a CMOS compatible process. For manufacturing reasons, such a chip is typically no more than two centimeters on a side. However, larger chips are also possible.
Optional electronic component 340 may be formed on sensor chip 330 (i.e., in a “system-on-a-chip” implementation), or on a separate back-end application specific integrated circuit (ASIC). Existing technology allows both analog and digital components to be formed on the same ASIC.
Optional component 350 allows review and further processing of the captured images.
In this embodiment, lens element 511 has a negative power, while the lens group formed by lens elements 514, 515 and 516—a configuration often referred to as a “triplet”—has a positive power, together with suitable compensation for chromatic aberration. The overall lens configuration is a “folded inverse telephoto” lens design. Inverse telephoto is a common wide-angle lens configuration. Such a lens configuration for a capsule camera is disclosed, for example, in U.S. provisional patent application Ser. No. 61/052,180, entitled “Folded Imager,” filed on May 10, 2008. The disclosure of the Imager Provisional Application is hereby incorporated by reference in its entirety.
As shown in
Besides pixel arrays 611, 612, 613 and 614, other components may also be formed on substrate 650, including timing and control block 620, one or more readout chains (e.g., read out chain 630) for reading out electrical output signals from the pixel arrays, and I/O ring structures 640. Such components may have conventional constructions.
Capsule camera system 800 may construct 360° panoramic images from images provided by optical lens sub-systems each having a horizontal field of view of 90° or greater. Such cameras can be used for any applications where wide field of view is desired, such as surveillance cameras and endoscopic cameras.
Thus, the present invention processes multiple images in a less complex, more cost-effective system than prior art imaging systems that use multiple cameras or image sensors. By fabricating multiple pixel arrays on a common sensor chip, the image capturing apparatus may be aligned and supported during manufacturing. Pixel arrays may be formed relative each other with an accuracy of one micron or less. Such a common sensor chip substantially eliminates the additional costs associated with packaging and handling multiple sensor chips beyond the first sensor chip. The reduced complexity results in a lower manufacturing cost. Further, signal processing elements provided on the single chip may be shared among the multiple pixel arrays. Consequently, the silicon area required to implement signal processing functions is reduced, resulting in a smaller die size, lower power, and lower manufacturing cost.
An imaging system of the present invention is also more compact. Under a proper design, a camera system using a single image sensor chip and multiple pixel arrays has a small footprint and can be used wherever a compact design is desired. For example, an imaging system of the present invention may be used in a capsule camera for imaging of the gastro-intestinal (GI) tract. Such an application is described, for example, in U.S. patent application Ser. No. 11/533,304, assigned to Capso Vision, Inc., or in U.S. Pat. No. 5,604,531.
The above detailed description is provided to illustrate specific embodiments of the present invention and is not intended to be limiting. Numerous variations and modifications within the scope of the present invention are possible. The present invention is set forth in the following claims.
The present application relates to and claims priority of U.S. Provisional Patent Application, entitled “Camera System with Multiple Arrays on a Chip,” Ser. No. 60/990,601, filed Nov. 27, 2007. The disclosure of the Provisional Application is hereby incorporated by reference in its entirety.
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