With digital cameras becoming extremely popular the good news for all photographers and enthusiasts is that the prices are going down. This tendency is mostly due to the invention of CMOS (complementary metal-oxide semiconductor) sensors used for digital cameras.
The process of making the CMOS image sensors is much faster and cheaper than that for the manufacturing of the CCD (charge-coupled device) sensors.
Thanks to the introduction of CMOS cameras, today more people have the opportunity to purchase reasonably priced, high-quality digital cameras.
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CMOS camera
CMOS sensors are often referred to as systems on a chip. There is a wide variety of CMOS sensors and it is thanks to them that digital cameras evolved so rapidly mainly due to their ease of use. The integrated chip technology is very flexible as far as cost reduction is concerned.
It comprises of a grouping (array) of pixel sections each containing a separate light sensor paired with an active amplifier for every pixel. CMOS sensors have all its functional parts on a single circuit which allows for real-time conversion of an object or a situation into a digital image.
All of the modules which are vital for the pixel sensor operation such as the analog-to-digital converter and the digital controller are on the CMOS sensor. All components are integrated into the sensor itself which allows for a faster speed and lower power consumption while at the same time providing high image performance.
What is a CCD camera?
The area on a CCD sensor is divided up into pixels via a series of channel stops and gates. When the sensor is exposing, the photons which fall on each pixel is converted into an electron and then stored as charge packets.
The gates of the pixels are then clocked to read the CCD sensor and to move the stored charge packets into a horizontal readout register. There the charge packets can be clocked individually into an amplifier which converts the electrons to a voltage.
Since the digital conversion occurs outside of the CCD sensor, a high quality 16 bit ADC (analog to digital converter) can be implemented. Every individual pixel is converted with the same amplifier which leads to excellent pixel to pixel linearity and reproducibility.
This process is slower but can result in images with superb quality.
CCD sensors rely on a number of external circuitry to function but this allows for better control and optimization of the camera which is excellent for low light imaging.
CCD vs CMOS
CCDs are made via a special production process which can create sensors which have the ability to transport the charge across the chip with no distortion. There are very high-quality CCD sensors which are unmatched in terms of light sensitivity and fidelity.
CMOS chips are made in a traditional way which is the same as making microprocessors. The former is a much more expensive and complicated process, while the latter is less expensive and easier.
CCD sensors are able to create low-noise and top-quality images, while CMOS sensors ar more prone to create noise.
The light sensitivity of the CMOS sensor is lower too.
CMOS is a low power sensor, while CCD consumes about 100 times more power due to the more complex processes involved in image capture.
CCDs tend to have more pixels and a higher quality, while CMOS provides lower sensitivity, lower resolution, and lower quality.
Which is better CMOS or CCD?
Which type of sensor is better depends on the needs and the use of the camera.
Here are the pros and cons of both sensor types, so you can decide which one is more suitable for your purposes:
CCD
Pros:
- Exceptional pixel-to-pixel reproducibility and high output uniformity.
- High-quality analog to digital conversion.
- Uses binning to modify the pixel size.
- Very little signal is added by the other circuits.
Cons:
- It is more expensive.
- The process of readout is slower.
- Uses 100 times more power than CMOS.
CMOS
Pros:
- Very fast read speed.
- Lower cost
- Use little power and has smaller system usage.
- Low read noise in high gain settings.
Cons:
- A 12bit ADC can lower the image quality.
- Low output uniformity.
- Amp glow
- No on-chip CCD binning.
- There can be variations in the sensitivity and linearity of the pixels.
Conclusion
Choosing between a CMOS and CCD camera should be based on what the camera is used for and what the end results are expected to be.
For crisp clean images with no distortion even in low light, a CCD camera should be used.
For the cases when high speed, ease of use and a lower power consumption and overall cost is a factor – CMOS is the way to go.
