CCD Linear Image Sensors
A CCD image sensor consists of a photodiode (photosensitive unit), CCD (transfer unit), and signal detection circuit (output unit). The photodiode converts light into electrons (charges) and stores them. The CCD transfers these electrons to the signal detection circuit. The signal detection circuit then converts electrons into electrical signals.
A sensor to reproduce an image shown on a document on the sensor pixels is called a contact image sensor. It reproduces the image at its original size. A sensor that uses lenses to reduce the image size and reproduces it is called a reduction image sensor. A contact image sensor is usually provided as a module consisting of a light source, lens, and sensor. This module is called a Contact Image Sensor (CIS) module.
Carriage structure (lens reduction type CCD)
Carriage structure (CIS module)
Applications
- Image Scanners
- Multifunction Printers
- Copy Machiness
etc.
System characteristics in terms of a lens reduction CCD or a CIS module
| lens reduction type CCD | CIS module | |||
| Resolution and resolving power (MTF) | ○ | Easy to achieve high resolution due to the single-chip structure. | Depends on lens resolution or resolving power (MTF). | |
| Depth of field | ○ | Deep. | Shallow. | |
| Optical designing and optical adjustment | Lens, mirror, and sensor must be adjusted. | ○ | Adjusted by individual module manufacturers. | |
| Downsizing (smaller and thinner) | Optical distance of 30 to 50 cm is necessary. | ○ | Optical distance of a few millimeters to 2 cm would be enough. | |
| Power consumption | High power consumption in the light source (cold-cathode tube or Xenon tube). | ○ | Low power consumption due to the use of an LED as a light source. | |
| Time required to make the first copy | Long rise time in terms of illuminance when using a cold-cathode tube. | ○ | Short rise time in terms of illuminance due to the use of an LED. | |
| ○ | Short rise time in terms of illuminance when using a Xenon tube. | |||
| Continuous copy speed | ○ | RGB can be read all at the same time because of the use of a white fluorescent light (cold-cathode tube or Xenon tube). | RGB must be sequentially lit and read by color due to the use of an LED. | |
Documents
- Sensors Product list