JP2511163Y2 - Original illumination device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a document illuminating device that illuminates a document and reads the document in a copying machine, a scanner, a facsimile, or the like.

[Prior Art] Generally, a document illuminating device using a tubular light source such as a fluorescent lamp is used for reading a document such as a copying machine or a scanner.

In this document illuminating device, as shown in FIG. 5, the light from the tubular light source 1 is reflected by the counter-reflecting plate 2 and irradiated onto the reading line 4 of the document 3, and the reflected light is received through the imaging lens 5. An image is formed on the portion 6. As shown in FIG. 6, the counter reflecting plate 2 is arranged on the side opposite to the tubular light source 1, and reflects a part of the illumination light of the tubular light source 1 toward the reading line 4 to improve the illumination efficiency. It is working. The counter reflector 2 in the figure is a conventionally used simple plane mirror, and its optical path is shown by an arrow.

By the way, the light amount distribution of the reading line 4 of the document 3 is brightest near the center in the longitudinal direction of the tubular light source 1 and becomes darker as it approaches both ends. Further, when an image of the original is formed on the light receiving portion 6 through the image forming lens 5, the end portion becomes darker than the center portion due to the cos ⁴ law of the lens. As described above, even if the two main parts necessary for reading the original 3 on the reading line 4 and the light receiving portion 6 are examined, the light amount distribution of the image of the received original is as shown in FIG. It is known that the brightest part of the image becomes dark as it approaches the edge. The light intensity distribution (solid line) of this semi-circular shape is as shown in the figure when the counter reflection plate 2 is not used (dashed line).
It is only 1.2 to 1.5 times as a whole, and accurate light and shade information of the original cannot be obtained unless the light quantity distribution is corrected to be uniform.

Therefore, for example, in the case of a scanner that electrically reads the image of the original 3 with a light receiving element at the time of CCD, there is a method called electrical shading correction, but if a large correction width is set, there is a side effect that the correction accuracy becomes coarse, Not preferable.

Therefore, there is a method of optically correcting the light quantity distribution. In this method, as shown in FIG. 7, a counter reflecting plate 8 is arranged on the side opposite to the tubular light source 1, and the reflecting surface of the counter reflecting plate 8 is ,
The tubular light source 1 is formed in a substantially V shape so that the illumination near the center of the tubular light source 1 is reflected toward the end portion of the reading line 4 where the light amount is small, or as shown in FIG.
A counter reflecting plate such as a counter reflecting plate 9 having a curved reflecting surface is used.

[Problems to be Solved by the Invention] In the document illuminating device using the counter reflecting plate described above, the light amount distribution on the reading line becomes uniform, and accurate document density information can be obtained. However, in the above-mentioned document illuminating device, since the counter reflecting plate is bent or curved, the counter reflecting plate becomes large and it is difficult to dispose the counter reflecting plate near the light source and the reading line. There is.

[Means for Solving the Problems] The gist of the present invention is to provide a document illuminating device that reads a document by reflecting light from a tubular light source in the reading line direction of the document by a counter reflection plate. The reflecting surface of the plate is divided and arranged in a sawtooth shape so that the illumination light near the center of the tubular light source is reflected toward the end of the reading line, and the opposing reflecting plate is formed in a straight line.

[Operation] Since the light near the center of the tubular light source is reflected toward the end of the reading line of the original by the counter reflecting plate, the light near the center where the light amount distribution is relatively large is dispersed to both ends of the reading line. The light amount distribution becomes substantially uniform on the reading line, and the reflecting surface of the counter reflecting plate is divided and arranged in a sawtooth shape, and the counter reflecting plate is formed in a linear shape, whereby the counter reflecting plate becomes small.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.
The whole structure of the document illuminating device is shown in FIG.

As shown in FIG. 1, the counter-reflecting plate 10 is substantially V-shaped in FIG.
The reflecting surface of the V-shaped counter reflecting plate 8 is finely divided and arranged in a sawtooth shape. The reflecting surface is finely divided and arranged in a sawtooth shape to form the counter reflecting plate (10) in a thin linear shape. This is formed based on the principle of a Fresnel lens.

Therefore, the counter reflecting plate 10 can be arranged close to the tubular light source 1, and the reflected light path can be shortened. Further, the light amount distribution on the reading line 4 becomes like the characteristic line (solid line) shown in FIG. 3, and the illumination efficiency is improved as compared with the characteristic line (broken line) when the counter reflecting plate 10 is not used.

Further, as shown in FIG. 2, the curved reflecting surface of the counter reflecting plate 9 of FIG. 8 may be finely divided and arranged in a sawtooth shape to form the counter reflecting plate 11 in a thin linear shape. In this case as well, based on the principle of the Fresnel lens, the counter reflecting plate
Forming 11. By forming the counter reflector 11 in this way, the light amount distribution on the reading line 4 becomes like the characteristic line (solid line) shown in FIG. 4, and the characteristic line when the counter reflector 11 is not used (broken line) ), The efficiency of illumination is improved, and the amount of light at both ends of the reading line is increased to improve the efficiency of illumination as compared with the case where the counter reflecting plate 10 is used.

[Advantage of the Invention] As described above, according to the present invention, since the opposed reflectors are divided and arranged to be thin, the opposed reflectors can be arranged near the tubular light source and the reading line.
The illumination efficiency is improved and the document illumination device is downsized.

[Brief description of drawings]

FIGS. 1 and 2 are perspective views of a counter reflecting plate showing the present invention, and FIGS. 3 and 4 show the light amount distribution in the reading line when the counter reflecting plate shown in FIGS. 1 and 2 are used. FIG. 5 is a characteristic diagram showing FIG. 5, FIG. 5 is an optical layout diagram showing the basic configuration of the document illuminating device, FIGS. 6 to 8 are perspective views showing a conventional tubular light source and a counter reflecting plate, and FIG. 9 is FIG. It is a characteristic diagram which shows the light amount distribution in a reading line when the counter reflection plate shown is used. DESCRIPTION OF SYMBOLS 1 ... Tubular light source, 2,8,9 ... Counter reflector (conventional example), 3 ... Document, 4 ... Reading line, 10,11 ... Counter reflector (sawtooth).

Claims (1)

(57) [Scope of utility model registration request] 1. A document illuminating device for reading a document by reflecting light from a tubular light source by a counter reflecting plate in a document reading line direction, wherein a reflecting surface of the counter reflecting plate is near the center of the tubular light source. 2. The original document illuminating device characterized in that the illumination light is divided and arranged in a sawtooth shape so as to be reflected toward the end portion of the reading line, and the counter reflection plate is formed in a linear shape.