JPS5876859A - Original reader - Google Patents

Abstract

PURPOSE:To obtain a signal corresponding accurately to the quantity of reflected light by guiding reflected light from an original scanned by a laser beam to a readout box which has light transmission parts and a reflecting and converging surface, and providing a photoelectric converting element and a correcting means for the guantity of converged light in the box. CONSTITUTION:A reading laser beam 1 illuminates a dichroic mirror 7 through a mirror 2, shutter 3, mirror 4, cylindrical lens 5, and beam expander 6. A recording laser beam 8 has wavelength corresponding to the spectral sensitivity of a photosensitive drum and illuminates the dichroic mirror 7 through a beam shifter 9, stabilizer 11 for the quantity of light and modulator 16. Then, the composite beam of said beams is polarized by a polygon 23 and separated through a dichroic mirror 25 into a reading laser beam, which is guided through the cylindrical lens 31 of a transmission part 30a to the readout box 30 to scan on an original through a transmission part 30b. Then, a light shielding member 33 is provided to perform photoelectric conversion 34.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an original reading device that scans the surface of an original with a laser beam, collects reflected light, and reads an image of the original from changes in the amount of collected light.

Conventional document reading devices guide a laser beam emitted from a He-Ne gas laser or the like to the document surface through an optical system including a beam expander, polygons, etc., and direct the reflected light from the document surface to the light receiving end surface ( The end face facing the original surface is received by a group of glass fibers arranged in a straight line, and the other end face of this glass fiber group is bundled, and the light emitted from there is applied to a light receiving part such as a hoat multiplier, and the image is It was about getting information. In a conventional device using a group of glass fibers as described above, the light-receiving end faces of the thin glass fibers must be aligned and arranged linearly in the main scanning direction.
This process is extremely troublesome and requires many man-hours to manufacture, and the glass fiber itself is expensive, resulting in high costs. In addition, even though the amount of light reflected on the document surface is the same, signals of different levels are output from the photoelectric conversion element depending on the document scanning point due to the directivity of the photoelectric conversion element and other factors. Laser printers and the like have had the problem of not being able to provide satisfactory image quality.

The present invention was made in view of the above-mentioned problems, and it scans the document surface with a laser beam, focuses the reflected light, and
In a document reading device that reads a document image based on a change in the amount of light condensed, a light condensing means includes a reading box having at least a light transmitting part that guides reflected light from the document surface into the interior, and a condensing surface that reflects and condenses the reflected light. In addition, by arranging a charging conversion element in the reading box and further providing a condensed light amount correction means so that the output of the photoelectric conversion element is not affected by the scanning position of the laser beam, a simple configuration can be achieved. The present invention has realized a low-cost document reading device that can obtain a signal that accurately corresponds to the amount of light reflected on the document surface.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIGS. 1 and 2 are explanatory diagrams showing one embodiment of a document reading device according to the present invention, and show a case where the document reading device is embodied as a laser printer. Of the two figures, Figure 1 is a configuration diagram seen from the top side, and Figure 2 is a configuration diagram seen from the front side (for ease of understanding, some parts are shown only in one drawing). In the figure, 1 is a reading laser, for example, the wavelength is 6.
It is an 11e-Ne laser that outputs 328 laser beams. Is the laser beam output from this reading laser 1 a mirror? , shutter 3. Mirror 4. The beam passes through a cylindrical lens 5 and a beam expander 6, and enters the front side of the dichroic mirror 7. 8 is a recording laser whose output light wavelength is determined in relation to the spectral sensitivity of the photoreceptor forming the surface of the photoreceptor drum. In this example, a short wavelength (for example, 441
6) He-Cd lasers are used. A beam shifter 9 is arranged in the beam optical path of the recording laser 8 to adjust the optical path in parallel, and the laser beam after passing through the beam shifter 9 is reflected by a mirror 10 and then enters a beam light amount stabilizing device 11. It has become. This stabilizing device 11 stabilizes the power of the laser beam directed to the subsequent optical system. The laser beam after passing through the stabilizing device 11 is condensed by a lens 14, passes through a shutter 15, and enters an acousto-optic modulator 16, where the laser beam modulated is transmitted through a slit 1.
Only the primary light is taken out by 7, collimated by lens 18 again, and then enters the rear surface of dichroic mirror 7 via one mirror, cylindrical lens 20° beam expander 21, and mirror 22. It has become.

The dichroic mirror 7 has the property of transmitting only light of a predetermined wavelength and reflecting the others; in this embodiment, the laser beam from the reading laser 1 is reflected (red light is reflected),
The laser beam from the recording laser 8 is transmitted (blue light is transmitted), and the laser beams from both lasers 1 and 8 are combined and made incident on the reflective surface of the polygon 23. This polygon 23 is rotating at a constant speed, and the laser beam deflected by its reflecting surface passes through an f/θ lens 24 and enters a dichroic mirror 25. Like the dichroic mirror 7 described above, the dichroic mirror 25 has the characteristics of transmitting blue light and reflecting red light, so that the combined beam is again separated into a recording laser beam and a reading laser beam. . The reading laser beam separated by the dichroic mirror 25 is guided to the reading box 30 by a group of reflecting mirrors 26, 27, 28, and 29.

The reading box 30 includes first and second light transmitting sections 30a, as shown in FIGS. 3 and 4.

30b is formed. The first light transmitting section 30a guides the reflected light from the mirror 29 into the reading box 30.
A cylindrical lens 31 is fixed there.

Further, the second light transmitting section 30b includes a cylindrical lens 3.
The laser beam that has passed through the scanner 1 is irradiated onto an original platen 32 made of a transparent glass plate, and the reflected light from the original surface is guided into the reading box 30 again. Inside the reading box 30, a photoelectric conversion element 34 is provided for detecting the light guided into the reading box 30 by the second light transmitting section 30b and reflected by the condensing surface 30C. As this photoelectric conversion element 34, a photomultiplier or a semiconductor photosensor is used. Condensing surface 3 in this example
0C is formed of an elliptical concave surface whose focal point is the photoelectric conversion element 34 (more specifically, its center A) and the document scanning point B of the reading laser beam. Generally, in an ellipsoidal mirror, light emitted from one focal point is focused at another focal point without aberration. Therefore, it is suitable for condensing light, but in the case of a reading device, since the document scanning point B moves, a problem arises if the condensing surface 30c is formed with an accurate elliptical concave surface.

Therefore, in this embodiment, as already shown in FIGS. 3 and 4, in consideration of ease of processing, the light converging surface 30c of the reading box 30 is formed into an ellipse at the intermediate position of the main scan. The shape was unified. When the light receiving area of the photoelectric conversion element 34 is small, as shown in FIG.
It is preferable to further improve the light collection efficiency by making d fan-shaped. Reference numeral 33 denotes a light shielding member disposed within the reading box 30, which has a slit 33a that is narrow at the center and wide at both ends, as shown in FIG. The output of the photoelectric conversion element 34 when this light shielding member 33 is not provided is determined by the directivity of the photoelectric conversion element 34 and the difference in the incident optical path from the document scanning point to the photoelectric conversion element 34, even if the output is uniformly distributed over a single document. , as shown in FIG. 7, different values are shown at the center and at the ends of the scanning line, and the output decreases when scanning near both ends of the document. Therefore, if the above-mentioned light shielding member 33 is inserted between the light condensing surface 30c and the photoelectric conversion element 34 as a light amount correction means, the amount of transmitted light in the central part is reduced, and the output of the photoelectric conversion element 34 as shown in FIG. Characteristics can be easily obtained. Regarding the specific dimensions of the slit 33a, please refer to the photoelectric conversion element 34.
Although it differs depending on what is used as the filter, for example, the directivity of the photomultiplier or the semiconductor photosensor, the point that the central portion is narrowed is exactly the same. Further, it is preferable that the mounting position of the light shielding member 33 be adjustable. Although not shown, the reading box 30 is supported by a guide rail or the like so that it can move in the left-right direction in FIG. They are driven by a motor or the like at the same speed. At this time, the 28.29 mirror group needs to move at half the speed of the reading box 30.

On the other hand, the recording laser beam separated by the dichroic mirror 25 is reflected by the mirror 35, passes through the cylindrical lens 36 and the protective glass plate 37, and is irradiated onto the photoconductor on the surface of the photoconductor drum 50, thereby forming a laser beam on the surface of the photoconductor. The electrostatic latent image formed is made into a hard copy by a known electrophotographic process 2 (with respect to each device making up the electrophotographic process, only the developing device 51 is shown in FIG. 2, and the others are omitted).

Next, a document reading operation in the above embodiment apparatus will be explained. Reading in this apparatus is performed by moving the reading laser beam in the main scanning direction using the polygon 23, and moving the reading laser beam in the sub-scanning direction by moving the reading box 30 at the same speed as the circumferential speed of the photoreceptor as shown in FIG. Towards the left (or right)
This is done by moving to . During this scanning, the reflected light from the document surface is generally scattered, and is transmitted to the second light transmitting section 3.
0b, the light is guided into the reading box 30, reflected by the light collecting surface 30C of the reading box 30, and illuminates the photoelectric conversion element-34. Therefore, if a reading laser beam scans a document having a pattern as shown in FIG.
A signal as shown in FIG. 3(b) is output from the photoelectric conversion element 34. In the case of this specific example, the output signal of the photoelectric conversion element 34 is amplified by the first amplifier 70 as shown in FIG. 10, and converted into a binary signal by the binarization circuit 71 (see FIG. See C)5. the second amplifier 72;
By driving the acousto-optic modulator 16 with the output signal of No. 2, the laser beam is modulated and the laser beam irradiation onto the photoreceptor is controlled to obtain a hard copy.

Note that the document reading device described above can be used not only for laser printers, but also for laser printers that also have the function of electrically receiving image information from a computer or the like to obtain a hard copy. Further, although the case of reading with a laser beam of a gas laser has been shown, the same applies to a semiconductor laser. Furthermore, the optical system does not need to be limited to that of this embodiment.

Furthermore, although the embodiment has been shown in which the document table 32 is fixed and the reading box 30 is moved, the reverse may be used. Furthermore, although the elliptical concave surface of the condensing surface 30c is unified into one elliptical shape, the condensing surface 30c is changed so that a plurality of elliptical shapes are continuous.
0c may be formed.

Further, in the above embodiment, the amount of light condensed was corrected by the light shielding member 33, but as shown in FIG.
It is also possible to correct the amount of light by using the light shielding member 33 instead of the light shielding member 33 (an example of light transmittance characteristics is shown in FIG. 12). As shown in FIG. 13, this correction of the amount of light condensation is possible by using a light-shielding plate 61 that is shorter than the scanning width of the laser beam and does not transmit light.The shape of the light-shielding plate 61 shown here is rectangular. However, depending on the directivity of the photoelectric conversion element, it can be shaped like a diamond, round, or
It may be formed into an ellipse or the like. Furthermore, as shown in Figure 14,
The reflectance of the central part 30e (shaded area) of the inner surface of the reading box 30 (especially the condensing surface 30C) is reduced (for example, painted black).
However, the amount of condensed light can also be corrected by increasing the reflectance (for example, by painting white) on both ends 30f (both sides of 30e). Of course, the inner surface of the reading box 30 may be painted white at the extreme end, and the reflectance may be gradually lowered as it approaches the center.

As explained above, the present invention has a major feature in that a reading box is used instead of the optical pipe made of a group of glass fibers, and a photoelectric conversion element and a light collection amount correction means are provided in the reading box. Therefore, according to the present invention, it is possible to realize a low-cost document reading device that can obtain a signal that accurately corresponds to the amount of light reflected on the surface of the document.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are explanatory diagrams of one embodiment of the present invention.
The figure is a configuration diagram seen from the top side, and FIG. 2 is a configuration diagram seen from the front side. Further, FIGS. 3 to 5 are explanatory diagrams of the reading hook in the second motherboard, and FIG. 6 is a perspective view of the light shielding member.
7 and 8 are characteristic diagrams of the photoelectric conversion element, FIGS. 9 and 10 are operation explanatory diagrams of the above embodiment, and FIGS.
FIG. 4 is an explanatory diagram of another embodiment of the condensed light amount correcting means. 1... Reading laser 5.20.31.36... Cylindrical lens 6.
21...Beam expander 7.25...Dichroic mirror 8...Recording laser 23...Polygon 25...
・F・θ lens 30...reading box 30a...
-First light transmitting section 30b...Second light transmitting section 30c...Condensing surface 32...Original table 33...
- Light shielding member 34... photoelectric conversion element 50...
Photosensitive drum 6o... NO filter 61... Light shielding plate Patent applicant Konishiroku Photo Industry Co., Ltd.? on behalf of
People Patent Attorney Osamu Ijima PI3 Figure 3 Figure 0 Figure 4 2 Figure 5 Figure 4 / Figure 6 M7 Figure Middle W, J9 Figure (c) - SυU Atsushi Figure 11 Figure 12 Atsushi 13 Figure n Figure 14 figure

Claims (6)

[Claims] (1) In a document reading device that scans the document surface with a laser beam, condenses the reflected light, and reads the document image from the change in the amount of condensed light, a light transmitting section that guides at least the reflected light from the document surface inside. and a reading box having a condensing surface for reflecting and condensing the reflected light is used as a light condensing means, and a photoelectric conversion element is disposed in the reading box, and further, the output of the photoelectric conversion element is the same as that of the laser beam. A document reading device characterized in that a light collection amount correcting means is provided so as not to be affected by a scanning position. (2) The document reading device according to claim 1, wherein the light condensing amount correcting means is constituted by a light condensing amount correcting member installed between the light condensing surface and the photoelectric conversion element. (3) The document reading device according to claim 2, wherein a light shielding member having a slit that is narrow at the center and wide at both ends is used as the light convergence amount correction member. (4) The document reading device according to claim 2, wherein an ND filter having low light transmittance at the center and high light transmittance at both ends is used as the condensed light amount correction member. (5) The document reading device according to claim 2, wherein a light shielding plate that is shorter than the main scanning width of the laser beam and does not transmit light is used as the light condensing amount correction member. (6) The document reading device according to claim 1, wherein the light condensing amount correcting means is configured such that the center portion of the light condensing surface has a low reflectance and both end portions have a high reflectance.