Tetsuya Kuno

A new automatic exposure system for digital still cameras

This paper presents a newly developed automatic exposure (AE) system for digital still cameras (DSC). The through the lens (TTL) system which has been employed mainly by conventional camcorders has been applied as an exposure control system for DSCs. However, the TTL system requires a longer time to obtain an appropriate exposure value, and it is therefore not a suitable control method for DSCs which demand immediate imaging after the shutter button is pushed. The authors have developed a high-precision AE capable of controlling the exposure quickly by converting the brightness of an object directly using the obtained value of an integrated image without using the photometric sensors other than a charge coupled device (CCD). They have also confirmed that the new system enables excellent exposure control without any problem.

Digital still cameras

This paper presents an interpolation method for digital still cameras (DSCs) which is based on color signal correlation. The authors have developed a method of reducing aliasing by increasing the resolution of color signals in DSCs that use a single-plate charge coupled device (CCD) with a primary color filter array. The new method interpolates signals by taking advantage of the fact that color signal variations are similar to one another in a local region of an image. It selects the signal that shows the higher correlation, either in the horizontal or vertical directions, at color signal positions subject to interpolation, thus improving the color resolution. First, the effectiveness of the new method was verified using image simulation. Next, the prototype hardware was fabricated. The prototype is fitted with an original reduced instruction set computer (RISC) built-in dynamic random access memory (DRAM) for processing image signals to provide high-speed camera signal processing. The authors also confirmed that the effectiveness of the new method was also established in actual products.

Advanced demosaicing methods based on the changes of colors in a local region

A large number of demosaicing methods using a directional or adaptive color correlation have been suggested. In such conventional methods, however, there is the problem of artifacts occurring on the edges of color boundaries. In the advanced demosaicing method we propose, demosaicing is carried out on the basis of the results obtained from the analysis of the changes of color signals in a local region. Using image simulation, we confirmed the artifact noise generated in the conventional method had been reduced by the advanced demosaicing method.

Practical color filter array interpolation with constrained color correlation

This paper presents a practical color filter array interpolation method using color correlation for digital cameras. Cost-effective digital cameras use a single chip image sensor and subsequent interpolation processing to produce full-color images. Although many types of sophisticated algorithm have been proposed to create high quality images, it becomes difficult to implement them in digital cameras due to their limited computing capacity, available processing time, and hardware size. The cost-effective interpolation methods using a directional or adaptive color correlation result in color artifacts on the edges of color boundaries. The proposed method eliminates these artifact regardless of the positive, negative or non-color correlation of images by adding a constraining condition to conventional color correlative interpolation. Experimental results confirm the effectiveness of this approach

Development Of Card-sized Digital still cameras

Digital still cameras (DSCs) have attracted a great deal of public attention as input tools for images. However, conventional DSCs are only extensions of compact cameras using 35 mm film, and are not compact enough for easy portability to take photos, anytime, anywhere. For the purpose of offering a more portable DSCs, the authors have developed a card-sized digital still camera (CDSC). It is portable (62/spl times/107/spl times/8.5 (12.3) mm) and has a flash memory which stores 15 pictures. The authors have also developed original software for the CDSC which has a new signal processing system which can offer high quality pictures.

A New Image-stabilization Method by Transferring Electric Charges

We have developed a new image stabilization method that utilizes electric charge transfer in the vertical transfer register of a CCD image sensor. This method repeats a series of actions including one or more continuous exposures according to the degree of camera shake, transferring, and adding electric charges in the vertical transfer registers to correct image blurs. This method can only correct blurs in the direction parallel to the vertical transfer registers, however it does not require mechanical components, external memory, or digital image processing circuits. Consequently, we can apply it in the direction of a single axis when executing biaxial blur correction to a camera that performs blur correction by means of drive control of the optical system in order to realize more compact cameras and reduce costs .

Optical-adjustment-free Camera Modules for Mobile Phones

We have developed optical-adjustment-free camera modules for mobile phones. Because of the currentboom in mobile phones with built-in cameras, easy camera assembly to speed unit output is important. Adjustment-free manufacturing helps camera module assembly makers deliver mass products with short turnovertime. In particular, focus-adjustment-free cameras can be made smaller and task time speeded up. We have examined the trade off between resolution and optical focal depth for mobile phones. And we have developed a new structure for camera modules that has an optical system set on the CMOS sensor to minimize the margin of error in assembly.

Development of very bright LC projector

A very bright, compact LC projector with a multi-scanning function has been developed by using LC panels with a scattering capacity called LCPC (liquid crystal polymer composite) and by reducing the circuit scale drastically using two newly developed LSIs.

Solid State Imaging Techniques. Improving Color Reproduction Characteristics of Industrial Television Color Cameras.

We report methods of improving the color reproduction characteristics of industrial television (ITV) color cameras. Since ITV color cameras are used in a much wider range of situations and lighting conditions than home-use camcorders, it is difficult for them to automatically adapt their color reproduction characteristics according to the color rendering properties of the sources. Thus they have poor color reproduction with low-color light sources. We have extended the light range of color temperature variation of TTL auto-white-balance and achieved automatic color correction according to the kind of light source detected by using the ratio of RGB signals. These methods solve the problem and give good color reproduction regardless of the type of light source.