This paper proposes and demonstrates a linear-logarithmic image sensor that can operate in both the linear and logarithmic modes, and exhibits low noise and no flickers. Its pixel is composed of one buried-photodiode, five n-channel MOS transistors, two p-channel MOS transistors, and one capacitor. During the linear mode operation, the pixel behaves the same as the four-transistor one, offering a low dark current and low noise. Also, in the logarithmic mode, it operates in an integrating manner in contrast to the majority of logarithmic-response CMOS image sensors that operate in a continuous manner. Thus it has no flickers and can calibrate the fixed pattern noise using the reference level. A wide dynamic range of 190 dB has been confirmed with a 256 × 256-pixel image sensor employing this novel pixel architecture.
This paper demonstrates, for the first time, TOMBO color imaging system that employs color-splitting filters on each
lens. A red, green, or blue color filter is allocated to each microlens instead of each pixel in conventional single-sensor
color imaging system. Thus the microlens array here also makes up a color filter array of Bayer geometry. For the
imaging device, a CMOS image sensor with 1040 x 960 pixels whose size is 6.25 um square was used. 8 x 8 microlens
array with 750 um pitch was employed as a taking lens. Excellent color images were obtained by rearrangement,
interpolation, and postdigital processing.
A very thin image capturing system called TOMBO (Thin Observation Module by Bound Optics)was developed with compound-eye imaging and post digital processing. With the prototype system, some excellent results have been obtained. In this paper, we focus on a multispectral imaging system as an application of the TOMBO.
In the system, it is possible to observe specific points on the target by multiple photodetectors with a special arrangement of the system. A filter array is inserted in front of the image sensor to observe the spectral distribution of the target. A captured compound image is reconstructed by an extended version of the pixel rearrange method. The pixels of the captured image are geometrically rearranged onto a multi-channel virtual image plane. Experimental results of the image reconstruction show effectiveness of the proposed algorithm.
A transversal direct readout (TDR) structure for CMOS active pixel image sensors (APSs) eliminates the vertically striped fixed pattern noise. This novel architecture has evolved to incorporate a variable shutter mode as well as simplifying the pixel structure. This paper describes a 320 X 240- pixel TDR APS that not only exhibits neither vertically nor horizontally striped fixed pattern noise, but can also take pictures at selected exposure times. The pixel consists of a photodiode, a row- and a column-reset transistor, a source- follower input transistor, and a column-select transistor instead of the row-select transistor found in conventional CMOS APSs. The column-select transistor is connected to a signal line, which runs horizontally instead of vertically. The column-reset and the column-select transistor are driven by the same pulse different from its predecessor. Thus the pixel is simplified by the reduction of the number of bus lines similar to conventional CMOS APSs.
A compact image capturing system called TOMBO (thin observation module by bound optics) is developed with compound-eye imaging and post digital processing. To demonstrate effectiveness of the TOMBO architecture, several prototype systems have been constructed with a refractive microlens array and a CMOS (complementary metal oxide semiconductor) image sensor. As a new algorithm for image reconstruction, the pixel rearrange method has been developed. With several test targets, the characteristics of the prototype systems are evaluated.
This paper presents a CMOS active pixel image sensor (APS) with a transversal readout architecture that eliminates the vertically striped fixed pattern noise (FPN). There are two kinds of FPNs for CMOS APSs. One originates form the pixel- to-pixel variation in dark current and source-follower threshold voltage, and the other from the column-to-column variation in column readout structures. The former may become invisible in the future due to process improvements. However, the latter, which result sin a vertically striped FPN, is and will be conspicuous without some subtraction because of the correlation in the vertical direction. The pixel consists of a photodiode, a row- and a column-reset transistor, a source follower input transistor, and a column-select transistor instead of the row-select transistor in conventional CMOS APSs. The column-select transistor is connected to a signal line, which runs horizontally instead of vertically. Every horizontal signal line is merged into a single vertical signal line via a row- select transistor, which can be made large enough to make its on-resistence variation negligible because of its low driving frequency. Therefore, the sensor has neither a vertical nor horizontal stripe FPN.
A compact image capturing system called TOMBO (thin observation module by bound optics) is presented, in which a compound-eye imaging optics is utilized for very thin system configuration. The captured multiple images are processed to retrieve the object image. An experimental system was constructed for verifying the principle and clarifying the issues related on the implementation. For the retrieve, two kinds of processing are considered: simple sampling and back projection methods. The TOMBO system is an instance of opto- electronic hybrid system providing excellent features based on opto-electronic cooperation.