1. Technical Field
This application is a continuation in part of U.S. patent application Ser. No. 13/237,077 titled “METHOD OF READING IMAGE AND THE IMAGE READING DEVICE”, the subject matter thereof being fully incorporated herein by reference.
2. Description of Related Art
A conventional image reading device 70 disclosed as prior art in U.S. Pat. No. 7,449,666 is shown in FIG. 4 and FIG. 5, which includes a multi-color light source 71, a rod-shaped lens array 73, and a monochrome image sensor array 75. While the multi-color light source 71, the rod-shaped lens array 73, and the monochrome image sensor array 75 are moved simultaneously in the same direction, the multi-color light source 71 emits light rays of different colors in a predetermined order, which are red light rays 71R, green light rays 71G, and blue light rays 71B. These light rays 71R, 71G, and 71B are projected onto an object 99 and then reflected. The reflected light rays 71R, 71G, and 71B image on the monochrome image sensor array 75 through the rod-shaped lens array 73. The monochrome image sensor array 75 generates signals after sensing the reflected light rays 71R, 71G, and 71B.
The conventional image reading device 70 senses images of all colors merely through the single one monochrome image sensor array 75, and therefore the multi-color light source 71 has to continuously switch between the three kinds of light rays 71R, 71G, and 71B within a distance as wide as a pixel. The multi-color light source 71, the rod-shaped lens array 73, and the monochrome image sensor array 75 are moved simultaneously for a distance as wide as a pixel. As a result, in each pixel of the object 99 sensed by the monochrome image sensor array 75, each light rays 71R, 71G, and 71B occupies only one-third of the pixel, which leads to chromatic aberration in each pixel with two-third bias.
Another conventional image reading device 80, which is also disclosed as prior art in U.S. Pat. No. 7,449,666, is shown in FIG. 6 and FIG. 7. The conventional image reading device 80 projects white light rays emitted by a white light source 81 onto an object 99, and then the white light rays are reflected. The reflected white light rays image on three monochrome image sensor arrays 85R, 85G, and 85B through a rod-shaped lens array 83, wherein the three monochrome image sensor arrays 85R, 85G, and 85B respectively have light filters 86R, 86G, and 86B for filtering red light rays, green light rays, and blue light rays. The colors of an image of the object 99 can be distinguished in this way. The conventional image reading device 80 has three monochrome image sensor arrays 85R, 85G, and 85B, and therefore it can sense three pixels on the image of the object 99 at once.
As we can see in FIG. 7, every time the white light source 81, the rod-shaped lens array 83, and the monochrome image sensor arrays 85R, 85G, and 85B are moved for a distance as wide as a pixel, the monochrome image sensor arrays 85R, 85G, and 85B respectively and simultaneously sense three different pixels on the image of the object 99, wherein the colors of the three pixels may differ from each other. After the white light source 81, the rod-shaped lens array 83, and the monochrome image sensor arrays 85R, 85G, and 85B are moved to project the white light rays on the third pixel on the image of the object 99, the sensed image from the object 99 is chromatic thereafter.
Although the conventional image reading device 80 solves the problem of chromatic aberration in pixels of the other conventional image reading device 70, most energy of the white light rays is filtered out after passing through the light filters 86R, 86G, and 86B, which is wasteful. If we want to speed up the scanning speed, the luminance of the white light rays has to be increased, which worsens the problem of power consumption and heat generation of the white light source 81. Furthermore, providing the light filters 86R, 86G, and 86B in the image reading device 80 increases cost of manufacturing.
It is worth mentioning that the invention disclosed in the U.S. Pat. No. 7,449,666 includes light filters too, hence it has the aforementioned problem, too.