Ikuo Akiyama

Interline CCD image sensor with an anti blooming structure

A ⅔-in 384 (H) × 490 (V) element interline CCD image sensor with a new antiblooming structure was developed. Blooming was suppressed without sacrificing photosensitivity and dynamic range by means of a vertical overflow drain positioned under (rather than beside) a photodiode. For 10-percent vertical height illumination the smear signal was reduced to 0.05 percent of the illumination signal. Well-balanced performance, namely, large dynamic range (72 dB), low random noise (65 rms noise electrons per charge packet), high-contrast transfer functions for horizontal and vertical directions, and a spectral response similar to the luminous efficiency curve were obtained under moderate operating conditions.

Interline CCD image sensor with an antiblooming structure

A ⅔-in 384 (H) × 490 (V) element interline CCD image sensor with a new antiblooming structure was developed. Blooming was suppressed without sacrificing photosensitivity and dynamic range by means of a vertical overflow drain positioned under (rather than beside) a photodiode. For 10-percent vertical height illumination the smear signal was reduced to 0.05 percent of the illumination signal. Well-balanced performance, namely, large dynamic range (72 dB), low random noise (65 rms noise electrons per charge packet), high-contrast transfer functions for horizontal and vertical directions, and a spectral response similar to the luminous efficiency curve were obtained under moderate operating conditions.

A new noise suppression method for high-definition CCD cameras

A novel noise suppression method for a high-definition CCD (charge coupled device) camera, the RDS (reflection-delayed noise suppression) method, is described. By using the reflection in a delay line, it has become possible to obtain both significant noise suppression and a wide frequency bandwidth. The method is superior to conventional methods in that its frequency bandwidth is very wide and its high-speed operations are very stable. The performance of a HDTV (high-definition TV) three-CCD color camera using this method is reported. >

A 1-inch 2-M pixel HDTV CCD image sensor with tungsten photo-shield and H-CCD shunt wiring

A 1-inch 2-million pixel FIT-CCD image sensor for HDTV has been developed, which features a tungsten photo-shield and horizontal CCD (H-CCD) shunt wiring. Tungsten photo-shield, which has low reflectance and good step coverage characteristics, reduces smear level to -110 dB, combined with a frame-interline-transfer (FIT) scheme. The tungsten photo-shield also acts as a shunt busline, supplying transfer pulses to vertical CCD (V-CCD) electrodes, so that a 1.2/spl times/10/spl circ/5 electron charge handling capability is obtained at a frame transfer frequency of 1 MHz. Newly developed H-CCD shunt wiring suppresses vertical line pair FPN, even with smaller transfer pulse amplitudes. H-CCD shunt wiring also helps reduce power consumption in the H-CCD by 2/3 as compared to that achieved with conventional wiring. >

HDTV single-chip CCD color camera

An HDTV (high-definition television) color camera has been developed by using a novel color-coding method, the field sequential color-coding method, to suppress spurious color signals. This camera has realized a high resolution of more than 850 TV lines without color moire and spurious color signals. Since the size and weight are 1/5 that of an HDTV 3-CCD color camera, it is suitable for both industrial and home use. >

A CCD image sensor with 768×490 pixels

HIGH-RESOLUTION TV CAMERAS are essential to home VTRs, industrial TV systems, broadcasting systems, and future high-definition TV systems. To provide cameras, solid-state image sensors are expected to be the most suitable devices, affording performance superior to that available from most of the current vidicon type pickup tubes. However, as far as the resolution is concerned, existing solid-state image sensors’ >2 are still inferior to vidicon pickup tubes. In the design of practical high-resolution solid-state image sensors, it is important to reduce the cell size to one half of that of the conventional device’, and also maintain a wide dynamic range and high sensitivity; i.e., high signal-to-noise ratio. Therefore, signal-handling capability per unit area for both photodiode (PD) and vertical CCD (VCCD) shift registers must be ideally doubled, and noise dominated by the output amplifier must be lowered. This paper will describe a high resolution interline CCD (HRIL-CCD) image sensor which includes 768 pixels in the horizontal direction and 490 pixels in the vertical direction. The overall die size of this sensor is the same as the conventional CCD models’. The HRIL-CCD image sensor was fabricated on a 20-30&m N-type silicon substrate using three-level polysilicon technology and 1 . 5 ~ rule fine pattern process. Image area measures 8.8(H) x 6.6(V) mm, applicable to a 2/3” vidicon lens view field. Unit cell size is 11.5(H) x 13.5(V) p. The aperture ratio is about 40%. A cross sectional view of a unit cell of the image sensor employing a vertical overflow drain’ is shown in Figure 1. The buried channel V-CCD shift register is made of a thick, highly doped P-well. The N-region of the PD is formed in a shallow, lightly doped P-layer which is a lateral diffused region of the above thick, highly doped P-well. Therefore, excess charge, which can be controlled by a substrate voltage, overflows through the laterally diffused P-layer into an N-type silicon substrate to eliminate blooming, while on the other hand, the entire P-well region under the V-CCD shift register is kept undepleted at this substrate voltage. Another advantage of this structure is that a unit cell with smaller size can also be realized by adjusting both dosage and depth of the P-well. The 3 . 3 ~ channel width of the V-CCD shift register was chosen to maximize the PD area. The depth of the buried channel for the V-CCD shigt register was designed to be as shallow as possible ( 0 . 5 ~ ) to obtain as much transferable signal charge as possible. Moreover, the thickness of Si02 for cell isolation has been thinned (about 0 . 3 ~ ) to reduce bird‘s beak intrusion, and also to suppress field-stress

A 1280 × 980 pixel CCD image sensor

An interline-transfer CCD image sensor with 1280(H)× 970(V) pixels that has been developed for a TV camera will be presented. The device, designed for high definition TV, has a 48dB SNR.

A CCD image sensor with 768 × 490 pixels

A ⅔-in 768(H) × 490(V) element interline CCD image sensor has been successfully developed. The device adopts a vertical overflow drain principle, a buried,channel amplifier, three-level polysilicon technology, and 1.5-µm-rule fine-pattern process. The device operates with an NTSC format. The 560 TV lines limiting resolution is obtained in the horizontal direction. No significant loss in transfer efficiency is observed in the horizontal register, even at the 14.32 MHz clock rate. Optimal photosensitivity spectrum response is obtained and the peak response appears at 550 nm. The noise equivalent signal is reduced to 48 electrons, using correlated double sampling. Then, the dynamic range reaches 68 dB. The correlated double sampling, combined with buried-channel amplifier technology is found to be also effective for great reduction in horizontal line noise.

A 2 M pixel HDTV CCD image sensor with tungsten photo-shield and H-CCD shunt wiring

A 1-in optical lens format, 2-Mpixel FIT-CCD (charge coupled device) image sensor is described. The low reflectance and good step coverage characteristics of a tungsten photoshield, combined with a frame-interline-transfer scheme, reduces the smear level to -110 dB. The tungsten photoshield also acts as a shunt bus line, supplying transfer pulses to vertical CCD (V-CCD) electrodes, so that a 1.2*10/sup 5/-electron charge-handling capability is obtained at a frame transfer frequency of 1 MHz. Tungsten-and-aluminum-shunt (TAS) wiring, used in a horizontal CCD (H-CCD), suppresses vertical line pair fixed-pattern noise, even at a smaller transfer pulse amplitudes. TAS wiring also helps reduce power consumption in the H-CCD by 2/3 compared to that achieved with conventional wiring.<<ETX>>

Ultra high-resolution CCD image sensor.

高精細度テレビカメラの固体化を指向した超高解像度CCDイメージセンサを開発した.有効画素数は, 水平1280×垂直970であり, 水平・垂直方向ともにテレビ標準方式の約2倍の解像力を有する.本センサは, インタライン方式であり, 縦形オーバフロードレイン構造を用いてブルーミングを抑制している.また, 水平CCDレジスタ部には, デュアルチャンネル読出し構造を採用して, レジスタ1本当たりの駆動周波数を半減させ, 転送効率の劣化に起因する解像度の低下を防止している.さらに, 出力アンプにはデプレッション型MOSFETを導入して, 広帯域化と低雑音化をはかっている.本センサの水平・垂直解像度は共に960TV本, 標準撮像条件 (2000lx, F8) におけるS/Nは48dBであり, 文書画像読取装置や電子スチルカメラなど, 新しい分野に応用するのに充分な特性が得られた.