out of photos by using a PC photography system, their excitement w
ill drive the next expansion of the digital image industry.
Foreseeing this acceleration in the demand for digital cameras, more than 20 vendors in Japan have been scrambling to capture market share, and they are committed to developing new models in response to consumer needs. In addition, a number of Taiwan companies are weighing in with a range of low-cost, low-end models slated to hit the international market in the second half of this year.
CCD vs. CMOS Image Sensors
At the heart of most standard digital cameras is a single chip, a charge-coupled device (CCD), similar to those found in scanners. By the 1980s, this image-sensing technology had become almost the exclusive choice for solid-state imaging applications. It has also become the standard imaging device for today's digital cameras.
"Thanks to their ability to convey a charge from the photodiode array to amplifiers along the edge of the chip with great accuracy, CCDs traditionally have been able to deliv
er far better image quality," says Huang Nan-Chao, technical engineer of the computer and peripherals division at Epson Taiwan Technology & Trading Ltd. A CCD cell measures only the brightness of light, regardless of the color. To accurately measure the separate RGB light intensities, a CCD needs to capture three separate images, each filtered for a respective color. While individual techniques vary, the basic idea is to capture alternating red, green, and blue light values, then interpolate the missing pixels for each color to approximate the RGB values for each cell.
In a conventional image-compression process, the analog signal from an image sensor is first converted to digital with an A/D converter. And all of the succeeding processes, including compression, are done in the digital domain. After their CCD captures a picture, these cameras use compression -- usually the JPEG file format -- to reduce the image file size. The greater the compression ratio, the more photos can be stored. However, us
ers have to sacrifice image quality in order to save expensive memory.
Recently, the electronics giant Sharp Corp. of Japan developed a high-end CCD image sensor that enables images of 1024 x 768 XGA resolution from a digital camera. This CCD imager incorporates more than a million pixels in the one-third-inch-square size that's widely used in consumer products. A number of midrange digital cameras based on this advanced technology will be available by the end of the year.
However, some observers see an intensifying contest between CCDs and CMOS imaging chips. CMOS imaging devices promise to cut power requirements and ease integration. CMOS is emerging as a possible candidate to replace the power-hungry CCD in next-generation portable equipment, some analysts say.
But others see a persistent advantage to CCDs. "Given the learning curve that CCDs have already, the new megapixel cameras will use CCDs," says Jeffrey Wan, vice president of Umax Data Systems, a Taiwan-based company that makes sca
nners and other peripherals. "But in the future," Wan predicts, "CMOS is likely to be very strong in the consumer market. One of the driving forces in the consumer market is the need to reduce power, and CMOS image chips use much less power than CCDs."
The CMOS Advantage
Unlike CCD image sensors, which require three different voltages with separate power supplies to drive them, CMOS devices require only a single power supply. This is a key factor in giving the CMOS device a tenfold advantage in reducing power consumption. Where CCD sensors rely on specialized fabrication processes that require dedicated and consequently expensive manufacturing processes, the CMOS sensor is fabricated with the same process used by a majority of semiconductor makers to produce integrated circuits. As a result, the CMOS device is much easier to integrate into an entire imaging system on a chip, leading to much lower cost at the system level.
"This will give Taiwan a great opportunity to compete with Japanese
suppliers' dominance in the arena of image sensor chips," says Chiang Wen-Tseng, digital camera project leader for Taiwan's Opto-Electronics & Systems Laboratories.
Additionally, CMOS image sensors can incorporate many traditional camera functions, including analog-to-digital conversion, timing, control, clock and bias generation, auto exposure, automatic gain control, gamma correction, and output-signal formatting for video standards such as PAL and NTSC.
Building these functions into the image sensor yields many system-level benefits, including reduced assembly and test costs, increased endurance, and much higher reliability. It empowers manufacturers to develop digital cameras that have the image quality of film cameras but at affordable prices.
These chips will anchor a new breed of low-cost, low-power, high-resolution digital cameras. Companies all over the world are engaged in a race to develop CMOS-based cameras. Toshiba Corp. of Japan has announced a prototype 1,300,000-pixel CM
OS sensor. This new device operates on a single 3.3-V power supply and supports the 1280 x 1024 SXGA format. It consumes only 30 mW, approximately one-tenth of the power that is required by most CCD imagers.
Other companies, such as Japan's Matsushita Electric and Olympus Optical, and U.S.-based VLSI Vision Ltd. and Photobit, are working on their own CMOS sensors. Taiwan's Opto-Electronics & Systems Laboratories, at the Industrial Technology Research Institute (ITRI, which is partially owned by the government), claims that it has successfully developed a megapixel CMOS device as well.
Matsushita's one-chip CMOS image sensor includes on-chip signal-compression circuitry, while Olympus's component features 4 million pixels, achieving both high resolution (2048 x 2048 pixels) and real-time readout.
There's one major problem with CMOS sensors, however. Early chips have been plagued with noise contamination, which degrades the signal as it traverses the wire to the sensor readout. Japanese c
ompanies are striving to overcome the noise problems by adding active CMOS circuitry to reduce that residual noise to a negligible level.
The Next Step
Digital cameras have evolved through several stages since makers started to flood the market with a comprehensive range of models in mid-1996. Consumers are becoming more discriminating in terms of portability, ease of use, and system expandability, according to Jack Cheng, product manager at Ability Enterprise Company Ltd., an affiliate of Canon Japan.
For the consumer market, digital cameras fall into three price points: below $500, around $500, and near $1000. "Resolution is a strong determinant of price," says Cheng. Low power consumption, large image capacity, and a compact package are also important features.
Before they buy, users should decide what they want to do with their camera, advises Casio's Wu. A model with 640 x 480 VGA resolution is adequate for a wide range of applications, he says, adding that "units selling for l
ess than $500 meet more than 80 percent of the digital image demand."
The models priced around $500 offer 24-bit color and two resolution choices: 320 x 240 (standard) or 640 x 480 (high) pixels. Standard resolution is acceptable for on-screen applications, but high resolution is needed if you want acceptable hard-copy reproductions. Most sub-$500 cameras have only an optical viewfinder and offer the LCD screen as an option for viewfinding, image previewing, and in-camera editing.
In a move to push digital imaging into the mass market, a handful of Taiwan companies has rolled out stripped-down, low-resolution (320 x 240 pixels) cameras priced at $199 or less. For the intended audience, "picture quality is not the only priority," says Casio's Wu. Affordability is also very important.
Sharp's Chen, however, would rather see cameras that can do more rather than cost less. "I think it will be more interesting to raise the capabilities of $300 to $500 cameras rather than to drop prices further,"
he says.
Digital cameras priced below $1000 are currently delivering resolution of about 100 pixels per inch, which supports a typical computer screen's resolution of about 96 dots per inch (dpi). The Kodak DC120, for instance, has a 836,400-pixel CCD imager and a motor-driven 3X zoom lens -- rare in a digital camera priced under $1000. It uses memory cards that range in capacity from 2 MB to 10 MB.
High-end digital cameras deliver the resolution needed to produce photographic-quality prints equal to those from 35mm film, but they're priced upwards of $10,000. This breed is familiar to professional and advanced amateur photographers. These cameras incorporate such high-end features as interchangeable lenses and manual control over f-stops and shutter speeds.
Next-generation cameras must have better resolution, longer battery life, and larger memory capacity, and they must include the full range of basic features such as automatic focus, zoom lens, flash capability, and high-quality viewfinde
r. Built-in LCD viewers, which are useful in determining whether the content and quality of an image are sufficient, will become standard.
Other new features will include Universal Serial Bus (USB) support and limited video. For example, Ricoh is bringing to market a digital camera with sound and motion-video capability, boasting resolution of 768 x 576 pixels; with this unit, users can record full-motion video and sound, although even with maximum data compression its 8-MB card has room for only a 5-second clip.
These cameras will allow several ways to transfer pictures and store them in a personal computer, including a standard serial/parallel connector, USB connector, flash memory reader, or even a magneto-optical (MO) drive, depending on how images are downloaded. Manufacturers believe some type of removable storage will be critical to consumer acceptance of digital cameras.
Three relevant form factors for removable storage devices have emerged: CompactFlash, promoted by the CompactFlash
Association (CFA), led by SanDisk Corp.; the Miniature Card, driven by Intel and AMD; and the Solid State Floppy Disk Card (SSFDC), backed by Toshiba and Kingston. It seems that most OEMs are reluctant to commit to an exclusive relationship.
SanDisk's CompactFlash card, adopted by leading players such as Kodak, Canon, and Ricoh, is a PC Card product that can be used with desktop and notebook computer peripherals without special drivers or software. "We believe CompactFlash offers our customers the best cross-platform solution available today for storing pictures from digital cameras," says Cheng at Ability.
Sony's
MVC-FD7
, on the other hand, uses a high-density floppy disk to store its images. This solution is somewhat inelegant to look at, but the theory is sound. Weighing 600 grams, the camera is large (126.5 mm x 110.5 mm x 73.3 mm) mainly because of the size of the floppy disk, but for the average user, floppies are familiar and universally available.
Cameras that
support wireless infrared downloads are extremely convenient. Sharp and Sony have implemented the technology into their latest cameras.
Sharp's Chen says the company is on the right track with its MD-PS1, which incorporates MiniDisc (MD) storage and wireless transmission technology. "We expect that other major camera manufacturers soon will follow Sharp's lead and introduce their own MD-based cameras," he says.
Beyond the Camera
Color printers from Hewlett-Packard, Canon, and Epson are capable of photo-quality output equivalent to 2400 dpi. HP's PhotoSmart printer reproduces an 8 x 10 photo in 5 minutes and a 4 x 6 photo in 2.5 minutes. In addition to the printer, HP offers PhotoSmart photographic papers that are available in matte and glossy finishes; photos printed on these papers are virtually indistinguishable from traditionally printed photos.
Fujifilm's thermo autochrome NC-3D printer offers photo-quality printing from digital files. The company claims that the cost per print
is at least half that of rival dye-sub printers.
Before you print, though, you might want to manipulate your images. In the area of editing tools, every product mentioned in this article comes with TWAIN drivers plus image editing software. Most of the cameras come bundled with their own TWAIN-compliant image-manipulation program.
The cameras from Agfa, Casio, Olympus, and Umax come with Adobe's PhotoDeluxe, and the Kodaks come with PictureWorks Technology's PhotoEnhancer Special Fun Edition. PhotoDeluxe is a user-friendly and powerful image-management package that lets you resize, crop, and edit pictures. PhotoEnhancer, on the other hand, lets you work with multiple images at once. It also includes a very helpful set of tools to make photo adjustments with ease.
Arcsoft's PhotoStudio, a Windows-based image-editing and special effects program, is now bundled with the cameras developed by Ricoh, Epson, Sony, and others. ArcSoft's direct-connection feature lets PhotoStudio upload or download i
mages directly from digital cameras. The images appear directly in PhotoStudio, ready for editing.
photo_link (14 Kbytes)
Sony's MVC-FD7 uses a floppy disk to store images.
Stella Kao is a freelance writer based in Taipei. You can reach her at
meou@email.gcn.net.tw
.
Digital Images
