JPH0223066B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reading device for an image forming device such as a facsimile machine or a recording machine that scans and reads a document. More specifically, the present invention relates to the arrangement position of a reference member of an automatic image quality adjustment means in a document reading device having a plurality of magnification modes.

First, as related to the present invention, a conventional facsimile automatic density adjustment method will be briefly described. In a normal facsimile machine, the read image information is passed through a lens to a photoelectric conversion element.
Project onto CCD. The optical information formed on this CCD becomes an output as shown in the graph of FIG. 1, and can be observed with an oscilloscope or the like. In the figure, L is the white level of image information, and D is the black level output. In order to judge the output of the image information obtained in this way in binary terms of black and white, the control circuit sets the slice level shown by the straight line S in Fig. 1, and a value higher than this S level (on the L side) By determining the output of the signal as white and conversely determining that the output of a value lower than the S level is black, it becomes possible to divide the output signal shown in FIG. 1 into two values.

However, in some manuscripts such as blueprint copies made by diazo copying machines and newspapers, the contrast between the image information portion and other portions is low. The output from the CCD when reading these originals is, for example, the second
The result will be as shown in the figure. That is, low contrast means that the difference in output between L and D levels is small. If the slice level S is set to a fixed value as described above, for example, in Fig. 2,
Both the L and D levels are below the S level, and both levels are considered black.

In order to solve this problem, it is necessary to hold the peak and valley values of the output level of the read image information as shown by the straight line S1 in Fig. All you have to do is set the . By setting the slice level in this way, no matter what contrast image information is input, it can be binarized into black and white. However, when reading all white or all black,
The above idea makes it impossible to set the slice level.

As a means to solve this problem, the concept of placing a fixed reflective member outside the effective reading area of the document, which serves as a reference for the output level of image information, has been proposed.
For example, when this member is made of a white material with high reflectance, the output of all black image information is as shown in FIG. 3. Here, W is the output level of the above-mentioned fixed white background reflective member (hereinafter referred to as reference white background),
D indicates the output level of all black information. At this time, for example, if the slice level S2 is set at an arbitrary position within a certain proportion of the output level W, it becomes possible to make a binary judgment such that the area above S2 is white and the area below is black.

As explained above, the slice level S in Figure 2
1 and the slice level S2 shown in FIG. 3, it is possible to perform binary judgment of black and white for documents of any contrast. In particular, this method of providing a reference white background is an inexpensive and reliable method for automatically adjusting the document density because it is sufficient to provide a reflective member made of a small piece on the reading line outside the effective reading area.

Let us now consider the case where the method using the reference white background described above is applied to a reading optical system having a plurality of variation modes. A conventional reading optical system having a plurality of variable ratio modes has an optical system arrangement as schematically shown in FIG. The device shown in the figure shows a document reading section of a facsimile machine. In the figure, 1 indicates a reading line, 2 indicates an optical axis of a lens, and 3 indicates an imaging section line of a CCD, which is a photoelectric conversion element. here,
Area l1 is 257mm on the short side of B4 size (JIS standard), while area l2 is 210mm on the short side of A4 size (JIS standard),
A solid line 4 shows an optical path in the reduced mode, and a broken line 5 shows an optical path in the same magnification mode. It is assumed that both optical paths 4 and 5 form images in the same area l3 on the imaging section line 3. In other words, if l2 = 210mm is imaged on l3 in the same magnification reading mode, l2 = 210mm is imaged on l3
When 1=257mm is imaged on the same l3, the reduction ratio is
It becomes a 210/257 reduction reading mode, and if l1 is set to the same size, l2 is enlarged. In such a case, considering the location for fixedly arranging the reference white background, for example, if we focus on areas 6 and 7, these areas are outside the effective reading area l2 in the same magnification mode. is the inner area of the effective reading area l1 in the reduction mode. Therefore, in the reduction mode, if there is a reference white background in these areas 6 and 7,
Image information will be lost. The problem mentioned above disappears in areas 8 and 9 compared to areas 6 and 7, but as is clear from the figure, in order to read the reference white background provided in area 8 or 9 in the same magnification mode, the optical path is moved far outside. must be expanded. This not only increases the angle of view of the lens, but also increases the length of the CCD. As a result, in order to simply read the reference white background, the angle of view of the lens on the 1x side must be made considerably wider, which naturally results in higher lens performance and higher manufacturing costs. At the same time, it becomes necessary to use a CCD with a large number of bits for the reasons mentioned above, and there is no advantage in terms of cost.

SUMMARY OF THE INVENTION An object of the present invention is to easily realize the arrangement of a reference member for an image adjustment means of a reading device having a plurality of variable rate modes, and to provide an inexpensive and highly reliable reading device.

To achieve the above object, the present invention includes a light receiving means including a plurality of light receiving elements for receiving image light from a slit-scanned document, and an output signal of the document image from the light receiving means that is scanned prior to scanning the document. and a reference member for correcting the slit, in a reading device that forms a document image within a fixed reading width of a light receiving means regardless of the document size, in which one end of the document is brought into contact with and positioned in the longitudinal direction of the slit. The present invention is characterized in that it has a positioning member, and the reference member is provided on the side of the positioning member in a vicinity outside the effective reading area of the document. A photoelectric conversion element is used as the above-mentioned light receiving element, and specifically,
There are elements such as CCD. Further, as the method of reading the original, there are two methods: one in which the original is read in line in a direction perpendicular to the direction in which the original is conveyed, and one in which the original is supported on a flat surface and the surface of the original is scanned in a plane. Furthermore, reference members include a white board to clarify the white and black parts as mentioned above, white and black as standards, and white and black to be used as scales for intermediate tones.
It is a board of black, gray, etc. The latter concept of using a scale as a reference is also used in electrophotography, and is used to set a reference potential.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 5 shows a reading section of a facsimile to which the present invention is applied, and this facsimile has a lens system (not shown) for setting a plurality of variable magnification modes. Then, l1, l as described in Figure 4
However, the original to be read is not transported centering on the optical axis, but is transported around a specific end regardless of the magnification mode or document size. The difference from FIG. 4 is that the conveyance is carried out to

In Fig. 5, 10 indicates the optical axis in the same magnification mode,
Reference numeral 11 denotes a positioning surface of a positioning member for positioning the original, and indicates a reference surface against which the original is abutted when conveying the original.
Regardless of the variable magnification mode, if a document is set and placed using surface 11 as a reference, the document will be conveyed for reading with surface 11 as a reference. If the position of the reference white background in this optical system is fixed to area 12, the reference white background will be included in the effective reading area l1 of B4 in the reduction mode, resulting in part of the image being missing. Furthermore, as mentioned above, region 13 has the drawbacks that the angle of view of the lens must be increased in the same magnification mode and that the length of the CCD on the light receiving side must be increased unnecessarily.

However, in the configuration shown in FIG. 5, all of the above-mentioned drawbacks can be solved by arranging the reference white background outside the effective reading area on the specific end side of image reading (on the document abutment reference 11 side). This is because, as is clear from the figure, if the lens of each magnification is made to have an angle of view slightly wider than the effective image reading angle of view, the lens can easily view the reference white background at each magnification, and the CCD can be exposed to light. Regarding the length of the CCD, the number of bits required for effective reading of image information plus a certain number of bits is sufficient. Therefore, it is possible to reduce the cost of the photoelectric conversion element on the light receiving side.

Here, how to actually construct the reference white background will be explained according to the embodiments shown in FIGS. 6 and 7.

FIG. 6 is a sectional view of the main part of the reading section. After placing the original 15 that you wish to send on the horizontal original table 16, when you operate an operating means (not shown), the drive system is activated, and the feed roller pair 17 and the ejection roller pair 18 rotate to move the original 15 in the direction of the arrow. Convey in direction A. At this time, image information passing through position B between both rollers 17 and 18 is read. In this reading section, 19 is a lower guide plate having a reading opening, 20 is an upper guide plate, and 21 is a light source for illuminating the document in the slit section.

The image information scanned and read by the slit section at the position B is transferred to the fixed mirror 22 and the condensing lens 2.
3, the image is formed on a CCD 24, which is a light receiving means equipped with a plurality of light receiving elements, and is then converted into an electrical signal and transmitted to the other party's facsimile. Other components 25 and 26 are stays for attaching the mirror and lens, respectively, and 27 is the CCD2.
The printed board on which 4 is attached is shown.

Here, the position where the reference white background is placed is the 6th position.
At the same time on the reading line position B shown in the figure,
This means that the area is just outside the effective reading width of this document. If an attempt is made to arrange the reference white background portion under these conditions, the result will be as shown in FIG.

FIG. 7 is a perspective view of the lower document guide plate 19, where the straight line B corresponds to the above reading line, and the dimension C indicates the effective reading area of the document. For the reference blank area, a lower guide plate 19 is partially extended outside the effective reading area on the abutment reference 11 side of the document to form a part 19a. And this part 19
The reading side of a (in the figure, the back side of the hatching side)
If you make it white, you can obtain the desired white background.
Examples of specific means for achieving this white color include applying white paint or gluing white paper.

In this way, it is possible to configure the reference white background portion even by using a part of the lower guide plate. As an example of the white background portion, the document side of the upper guide plate 20 may be white, a portion of the lower guide plate 19 may be cut out, and the white portion of the guide plate 20 may be exposed to CCD.

In the above embodiment, attention is paid to a reading optical system such as a facsimile machine having multiple variable magnification modes, and when placing the fixed reference white background of the automatic density adjustment means on the reading line, the specific side of the reading area is used as a reference. By using an optical system that arranges originals of various sizes and irradiates them onto a light-receiving element of a certain size, and by placing them on the reference side of the reading area and near the outside of the effective reading area, the angle of view is unnecessarily large. It does not require a condensing means such as a lens. At the same time, this has the effect of not requiring an unnecessarily long or large photoelectric conversion element. In other words, it is possible to obtain an inexpensive and reliable automatic density adjustment means even in a facsimile machine having a plurality of magnification modes.

Note that the present invention is not limited to the above-mentioned combination of facsimile line scanning and a reference blank area, but can also be applied to a device that reads an original using a photoelectric conversion element and is provided with a reference member for adjusting image quality. By doing so, the above effects can be obtained.

[Brief explanation of drawings]

Figures 1, 2, and 3 are graphs showing how to set the slice level to binarize the black and white parts of a document image, and Figure 4 is a graph showing how to set the slice level to binarize a document image into black and white parts. A conceptual diagram of the optical system showing the positional relationship between the document position and the reference member, FIG. 5 is a conceptual diagram of the present invention, and FIG.
The figure is a sectional view of the main part of a facsimile to which the present invention is applied, and FIG. 7 is a perspective view showing the configuration of a reference member. In the figure, 1B is a reading line, 2 and 10 are optical axes, 3 is an imaging line, 4 and 5 are optical paths, 11 is a reference position of the document, 19a is a reference white area, and 24 is a CCD
The element is shown.

Claims (1)

[Scope of Claims] 1. A light-receiving means including a plurality of light-receiving elements that receive image light from a slit-scanned original, and a light-receiving means that is scanned prior to scanning the original and corrects an output signal of the original image from the light-receiving means. A positioning member that abuts and positions one end of the document in the longitudinal direction of the slit in a reading device that forms a document image within a fixed reading width of the light receiving means regardless of the document size. A reading device characterized in that the reference member is provided near the positioning member and outside the effective reading area of the document.