The mechanism of the CCD scanner
The CCD-type bar code scanner
The CCD-type bar code scanner uses the CCD image sensor (the image capture
device) which is used with the video camera and the digital camera and so on and
reads bar code information as the image.As for the point which is different from CCD of the video camera and so on, the video camera reads the surface of 2-dimension (2D) with the color whereas the general bar code scanner reads 1-straight-line line (1D) by the gray scale. (Recently, the surfaces such as the 2-dimension bar code and the colored bar code and the bar code which has information in the color and so on, too, have begun to be practicalized.)
It lights up the bar code to read by the red LED which is had inside the scanner. The camera makes an image with lens on the film and in と with construction the same principle, it makes the image of the bar code with lens on the CCD image sensor. The image which was taken in by the CCD image sensor is to analyze by the CPU inside the scanner, and the distinction and reading the bar code which is contained during image by it
The characteristic of the CCD-type bar code scanner
At first when a bar code was practicalized, a pen-type scanner was used. Because
it was scanning in the person interlude, to read a bar code, the pen type needed
a considerable knack. When comparing with this, because reading is done, turning
a reader part to the bar code only, the CCD-type bar code scanner can use a the
first time scanner to use, that there is little in the practice.It was a very excellent method but at sold first, it was very expensive.
Because however, are a semiconductor and the scanner which was composed of software
The price fell substantially in massing produce a personal computer in the same way.
It becomes popular as widely as meaning CCD scanner if the price, too, becomes extremely inexpensive at present and saying a bar code scanner.
The oblong square of the photograph back is CCD image sensor and the black circle in front is a lens.
The CCD image sensor
CCD is the abbreviation of Charge Coupled Device. The semiconductor devices such as the transistor have the nature that the electric characteristic changes when they are exposed to the light originally. Generally, a semiconductor is made to suppress such an outward change but is made with sensor devices such as the photo transistor and the photo diode which is manufactured to sense light in the influence by the light with to change, being popular being easy. These devices can change the strength of the light into the electric charge (the energy of the electricity).If arranging thousands of photo transistors in one line on the wafer of the semiconductor, theoretically, a linear image sensor is made. However, there is a limit in each of the devices even if it says that the wiring by the huge number became necessary and that much IC was specifically made high density about the fact to take out conduct information in the wiring. Moreover, in case of CCD, it isn't possible to wire metal in the surface in the semiconductor part which receives light.
To solve it, in to send to the bucket relay formula to the cell block next, it arranges some common control lines only in making a signal with the strength of the light which was received in each photo acceptance unit part an electric charge and it is composed of CCD.
The inter line transfer type seems to be mainly used at the bar code scanner.
The characteristic of the CCD image sensor
Because it is a solid image device by the semiconductor, CCD has the characteristic which is excellent about following emergency.- The sensor with very high density
- It is possible to read an image at high speed.
- It is highly precise.
- There is little looseness by the device.
- It is strong in the vibration and the impact because there is not a machine drive part.
- Little environment change, passing year change occur.
- It is very light.
- It is possible to read at high speed.
- It is possible to read at once.
- It is suitable for a great deal of production.
- The mechanical adjustment is unnecessary.
Because it prepares inside the bar code scanner, a lot of bar code scanner can directly connect the CPU (the decoder) and the keyboard interface which analyzes a bar code to the personal computer.
The performance of the CCD scanner
They, too, influence a performance because the CCD scanner is an electronic product but is an optical product like the digital camera and so on, too.- The performance of the lens
- It reads the image of the bar code with the lens. When the lens that the
resolution is low is used, the problem comes up to the small bar code
reading.
- The performance of CCD
- As for CCD, the photo acceptance unit stands in line at one line of the sides. 1024, and 2048 and there is a number of these photo acceptance units. The point which is much can be read because the resolution rises as CCD to the extent that the photo acceptance units are many.
- The performance of the CPU
- When the photo acceptance unit increases, because the processing quantity
after reading increases, the higher-speed CPU and the bigger work memory
become necessary.
Recently, 2000-4000 numbers of the devices are general.
- The scan speed
- It shows how many time it is scanning to 1 second. In case of the CCD scanner, it is influenced by the image transfer rate from CCD and the ability inside the scanner to analyze an image.
