Since bringing the world's first CCD video camera to market, Sony has continued to develop and introduce new digital imaging products, including Handycam and Cyber-shot. It has accumulated extensive experience and a range of technologies to achive high picture quality, which it has applied to the development of CMOS sensor technology and CMOS sensor camera systems. One of the successes to emerge from this work is the CMOS sensor that was used in the DCR-PC1000, launched in 2004 as the world's first consumer digital video camera featuring three CMOS sensors. In 2005 Sony's CMOS sensor was also used as the image sensor in the HDR-HC1 Digital HD "Handycam". The superb images produced by these cameras are proof that despite its compact size, Sony's CMOS sensor yields excellent imaging performance. CMOS sensors made compact HD video cameras a reality.
What is a CMOS Sensor?
Like a CCD, a CMOS sensor is used as an image sensor in digital still and video cameras. It uses an internal array of photodiodes to convert images entering the camera through the lens into digital images. The major structural difference between a CMOS sensor and a CCD is the fact that each photodiode in a CMOS sensor has an amplifier that converts electrical charges to voltage. In a CCD, the photodiodes in each row act like a "bucket brigade." The charges passed along each row are collected and transferred to the output stage, where they are converted to voltage by an amplifier.
CMOS sensors have long been widely known as a type of image sensor offering a number of advantages over CCDs, including low power consumption, high data retrieval speed, and compatibility with LSI logic. However, for many years they were considered unsuitable for perusing high picture quality imaging applications because of issues relating to their structure and manufacturing processes.
Over the last few years there have been dramatic improvements in the image quality achievable with CMOS sensors, and today they are used in television cameras and professional SLR digital cameras. Like CCDs, CMOS sensors have started to attract increasing interest as image sensors. However, there are still major obstacles to the use of CMOS sensors in producing high resolution images.
Light is converted into electricity by the photodiodes, which read out the accumulated charges and output them after amplification. With CMOS sensors, charges are converted to voltage and amplified at each pixel.
As with CMOS, light is converted into electricity by photodiodes. With CCDs, however, the data remains in charge form as it is passed along by the photodiodes, which act like a "bucket brigade." The charges are all converted into voltage at the output stage.
ClearVid CMOS Sensor and Enhanced Imaging Processor
Demand is on the rise for digital video cameras capable of capturing high resolution still images and HD video images. Naturally, such capabilities require high-resolution image sensors. At the time, the challenge was to increase resolution (by increasing the number of pixels) without increasing the size of the image sensor. At first glance, one would think that the only answer would be to reduce the size of each individual pixel. However, this reduces sensitivity because it results in a reduction in the light-receiving surface area of each pixel. Conversely, to increase sensitivity without changing the number of pixels (by increasing the size of each pixel), it would be necessary to increase the size of the image sensor itself, making it impossible to achieve highly-compact products. The goals of increasing resolution and improving sensitivity have generally been regarded as mutually exclusive, which meant that it was impossible to create a video camera, especially a compact video camera, capable of capturing high resolution still images. Sony overcame this challenge by developing and bringing to market its new ClearVid CMOS Sensor, and by optimizing its image processing engine, the Enhanced Imaging Processor, to maximize the performance of the new image sensor.
