1. Field of the Invention
The present invention relates to an image pickup unit, mounted in a facsimile or a cash dispenser, for taking an image of the surface of an object (more specifically, printed characters on an original or embossed characters on a cash card, for example).
2. Prior Art
FIG. 2 is a sectional view showing an example of a conventional specular reflection type image pickup unit having a image-forming means, such as a rod lens, arranged at such a position as to receive the maximum quantity of reflected light.
In this image pickup unit, a light source 1 is provided at a position a specified distance away from the target surface of the object, such as an original P. The light source 1 is formed of a plurality of light emitters arranged in a row, and emits light ph1 in a linear form at a specified angle xcex8(0xc2x0 less than xcex8 less than 90xc2x0) to a direction normal to the target surface of the original P. After passing through a glass plate 2, the emitted light ph1 is incident on the focal points f of a rod lens array 3 on the target surface of the original P at an incidence angle xcex8. The incident light is reflected by the target surface chiefly as a maximum quantity of reflected light rf1 at a reflection angle xcex8. For this purpose, the rod lens array 3 is so arranged as to hold the angle xcex8. Therefore, when the reflected light rf1 is converged by the rod lens array 3, an image is formed at an image-forming position indicated by a conjugate distance T. Note that the conjugate distance T is the characteristic value of the rod lens array 3 that shows the distance between the target surface of the original P and the image-forming position. The light-receiving faces of image pickup elements 4 are located at this image-forming position. The reflected light rf1 which formed the image plane is converted into electric signals by an array of image pickup elements 4, and the electric signals pass through a board 4a and are sent to an image processing system, for example, to undergo a specified process. The light source 1 is mounted on the board 1a, and the board 1a is located at a proper position and supported in a housing 5. The image pickup elements 4 are fixed through the intermediary of a board 4a to the inside walls of the housing 5 such that the light-receiving faces are normal to the propagating direction of the reflected light rf1.
As has been described, in the specular reflection type image pickup unit, the light source 1 and the rod lens array 3 are arranged at equal angles xcex8 to the normal to the target surface of the original P. Therefore, since the image pickup elements can receive the maximum quantity of the reflected light, the embossed characters of a cash card, for example, can be displayed with proper contrast on the display screen.
However, the conventional image pickup unit in FIG. 2 has a problem. Specifically, the problem is the large width of the housing attributable to the inclined mounting in the housing 5 of the board 4a on which the image pickup elements 4 are mounted.
Meanwhile, FIG. 3 is a sectional view showing an example of the irregular reflection type image pickup unit whose size was reduced by the sacrifice of the received light quantity of the image-forming means. The same parts as those in FIG. 2 are designated by the common reference numerals.
In this image pickup unit in FIG. 3, the rod lens array 3 is arranged normal to the target surface of the original P, and receives the reflected light rf1. Therefore, the width dimension of the housing 5A can be made smaller than that of the housing 5 in FIG. 2. However, due to the smaller received quantity of the reflected light rf1, this image pickup unit is unable to produce a distinct image.
It is an object of the present invention to provide an image pickup unit which is made in a compact size but capable of producing vivid images.
In present invention, the image pickup unit comprises a light source, an image-forming means, image pickup elements, a housing, and a board.
The light source for emits a light to a target surface of an object at a fixed angle to a direction normal to the target surface. The image-forming means is mounted at such an angle as to receive a maximum quantity of reflected light from the target surface, and forms an image at a specified image-forming position. The image pickup elements receive the reflected light converged at the image-forming position and convert the reflected light into an electric signal. The light source, the image-forming means, and the image pickup elements are arranged in the housing. The image pickup elements are mounted on the board, and the board is arranged in the housing in parallel with the target surface.
By adopting the configuration described above, the space between two walls of the housing which are parallel with the target surface of the object can be reduced, so that the housing itself can be reduced in size.
Because the image-forming means is arranged at such an angle as to receive a maximum quantity of the reflected light, distinct images can be obtained by the image pickup elements.
According to a second embodiment of the present invention, an image pickup unit comprises a light source, an image-forming means, image pickup elements, a housing and a board.
The light source emits a light to a target surface of an object at a fixed angle to a direction normal to the target surface. The image-forming means is mounted at such an angle as to receive a maximum quantity of reflected light from the target surface, and forms an image at a specified image-forming position. The image pickup elements receive the reflected light converged at the image-forming position and convert the reflected light into an electric signal. The light source, the image-forming means, and the image pickup elements are arranged in the housing. The image pickup elements are mounted on the board, and the board is arranged in the housing in a direction at right angles to the target surface.
By adopting the configuration shown in the second embodiment, the space between two walls of the housing, each of which lies in a direction at right angles to the target surface of the object, can be reduced, with the result that the housing itself can be reduced in size.
Like in the first embodiment, because the image-forming means is arranged at such an angle as to receive a maximum quantity of the reflected light, vivid images can be obtained by the image pickup elements.
In the first and the second embodiments, that portion of the board where the image pickup elements are mounted may be bent to orient the light-receiving faces of the image pickup elements at right angles to the propagating direction of the reflected light. By this arrangement, the image pickup elements can be positioned correctly at the image-forming means merely by moving the board in one direction along the wall.
In the first and the second inventions, it is possible to arrange another board for mounting the light source in a direction at right angles to the target surface and install a reflector to reflect the emitted light of the light source at a fixed angle. By this arrangement, the other board, which was inclined, is now arranged in parallel with the wall opposite the wall on which the other board is mounted, so that the housing can be further reduced in size.