JPS6151821B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a copying machine that detects optical information using a line sensor and records it on recording paper wound around a rotating drum, and its purpose is to improve light unevenness. .

A line sensor collects optical information using photoelectric conversion elements arranged in a line. Information on the subject document is imaged onto the line sensor using a lens, and electrical output is generated by photoelectrically converting this image. can get. Normally, optical information is sequentially extracted by main-scanning this by electrical means and sub-scanning by mechanical means.

A copying machine or a facsimile receiver is constructed by writing the output thus obtained on a recording paper wound around a rotating drum.

In a copying machine with such a configuration, uneven illumination of the original will cause unevenness in the optical information, making it impossible to make good copies.In particular, the light intensity characteristics of the imaging lens, that is, the reduction in peripheral light intensity, will cause large output unevenness. Occur.

FIG. 1 shows a conventional copying machine having such characteristics, with FIG. 1A showing its overall configuration and FIG. 1B showing the amount of light incident on the line sensor. In the figure, the line sensor 1 has an imaging lens 2.
The optical information 3e of the original 3 is projected to form a real image 1.
It is converted into an electrical signal as e. Line sensor 1
is driven by a clock signal 6 to a clock input 1c and a start input 1b of a switch 7 which generates a start signal that determines the start of scanning. Line sensor 1
The electrical output 1a is amplified by the amplifier 5 and then applied to the recording needle 10. The rotary drum 8 is rotated at a constant speed by a motor 9, and a start signal is generated by a switch 7 every time it rotates. Further, the line sensor 1 and the lamp 4 are mechanically sub-scanned in synchronization with the movement of the recording needle 10. The original 3 is illuminated by a lamp 4.

In such conventional copying machines, it is extremely difficult to make the illumination by the lamp 4 uniform over the entire surface of the document in the main scanning direction, and even if uniform illumination is achieved, the amount of light around the imaging lens 2 As shown in FIG. 1B, the light input at both ends of the line sensor decreases as compared to the center of the line sensor. This characteristic is determined by the performance of the lens, and can be improved by using a high-quality wide-angle lens, but the lens configuration becomes complicated, requiring a large and expensive lens, which increases the cost of the copying machine. vinegar. There is also a method of compensating for this decrease in light intensity around the lens using illumination, but this requires providing illuminance to the original as shown in Figure 2, making it extremely difficult to adjust the light intensity and ensuring good unevenness. It's almost impossible to fix.

The present invention solves the above-mentioned drawbacks easily and inexpensively, and one embodiment of the present invention will be described in detail below with reference to the drawings. In addition, in the figure, the same parts as in FIG. 1 are given the same numbers and explanations are omitted.

FIG. 3 shows a copying machine according to an embodiment of the present invention, FIG. 3A shows its overall configuration, and FIG.
FIG. 3B is an enlarged view of the means for controlling the amount of light to the line sensor 1, and FIG. 3C is a diagram showing its characteristics.

In the figure, a transparent plate 32 is inserted between the lamp 4 and the document 3. The transparent plate 32 has a disk shape, and a gear 31b is formed on the periphery of the disk.The transparent plate 32 is connected to a gear 31a that rotates at the same speed as the rotating drum 8. The number of teeth of the gear 31b is selected so that it rotates quickly. The light transmitting plate 32 has a transmittance that changes in a sinusoidal manner as shown in FIG.
has two surfaces, and two bright portions 32b.

As described above, the rotation of the transparent plate 32 is synchronized with the rotation of the rotating drum 8, and the start phase of the line sensor 1 also corresponds to the phase of the rotating drum 8. 32
If the line sensor is set so that when a is relative to the lamp 4, the line sensor scans the center portion, and when the bright portion 32b of the transparent plate 32 is relative to the lamp 4, the line sensor scans the end portion, then the periphery of the lens in the main scanning direction can be scanned. It is possible to compensate for a decrease in the amount of light. Furthermore, by using this method, it is also possible to compensate for defects in the light source, such as light unevenness due to the position of the light source lamp. On the other hand, if the lamp 4 and the line sensor 1 are mechanically sub-scanned in the sub-scanning direction, uniform illumination can be achieved in the sub-scanning direction.

FIG. 4 shows a second embodiment of the present invention. In this embodiment, two polarizing plates (a polarizing plate and an analyzing plate) are used as means for controlling the amount of light to the line sensor. ing. In the figure, a polarizing plate 41
and the analyzer plate 42 are placed between the lamp 4 and the original 3 in an overlapping manner. A gear 31b is provided on the periphery of the polarizing plate 41, and this is coupled to the gear 31a of the rotating drum 8, as in FIG.

It is well known that when the polarizing plate 41 and the analyzing plate 42 are overlapped and rotated, their transmittance changes sinusoidally, and characteristics similar to those shown in FIG. 3C can be obtained.

FIG. 5 shows a third embodiment of the present invention, in which the amount of light to the line sensor is controlled by changing the width of the light-transmitting path of the light-shielding plate.

In the figure, the light shielding plate 51 has a light-transmitting part and a light-blocking part, and the light-transmitting part has a wide part 51b and a narrow part 51a. Therefore, if the light shielding plate 51 is rotated and the light source and the document are opposed to each other through the light shielding plate, the illuminance of the document by the illumination light source will periodically repeat brightness and darkness.

As is clear from the above detailed description, by using the light amount control means according to the present invention, it is possible to easily and inexpensively compensate for a decrease in the peripheral light amount of the lens.

[Brief explanation of the drawing]

FIG. 1 shows a conventional copying machine, in which A is a schematic diagram and B is a diagram showing an illuminance distribution. Fig. 2 is a diagram showing the illuminance distribution when compensating for the decrease in the amount of light around the lens with illumination, Fig. 3A is a schematic configuration diagram of a copying machine according to an embodiment of the present invention, and Fig. 3B is a partial perspective view. , C is an explanatory diagram of the operation, and FIGS. 4 and 5 are partial perspective views of other embodiments of the present invention. 1... Line sensor, 2... Lens, 3... Document, 4... Lamp, 5... Amplifier, 6... Clock signal, 7... Switch, 8... Rotating drum, 9
... Motor, 10 ... Recording needle, 31 ... Gear, 3
2... Translucent plate, 41... Polarizing plate, 42... Analyzing plate, 51... Light shielding plate.

Claims (1)

[Scope of Claims] 1. A line sensor that forms an optical image obtained by irradiating a document with a lamp through a lens and converts optical information from the optical image into an electrical signal, and each photoelectric conversion of the line sensor. A drum that rotates in synchronization with main scanning that sequentially electrically scans the elements, and a recording means that is movable in the direction of the rotational axis of the drum and that records on a recording paper wound around the drum based on the electrical signal. a sub-scanning means for mechanically moving the lamp and the line sensor in a direction orthogonal to the main scanning direction of the line sensor in synchronization with the movement of the recording means in the direction of the rotation axis of the drum; 1. A copying machine comprising: a light amount control plate disposed on a drum, the light amount control plate controlling the amount of light irradiated onto the document so as to be uniform in the main scanning direction in synchronization with the rotation of the drum. 2. The copying machine according to claim 1, wherein the light amount control plate is constituted by a rotating disk having an opening in the center, and the rotating disk is a transparent plate whose transmittance changes sequentially in the direction of rotation. 3. The copying machine according to claim 1, wherein the light amount control plate is composed of two polarizing plates, and an opening is formed in the center of one of the polarizing plates. 4. A copying machine according to claim 1, wherein the light amount control plate is constituted by a rotating disk having a light-transmitting part and a light-blocking part, and the width of the light-transmitting part changes sequentially in the direction of rotation.