JPS6235300B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reading variable magnification method in a solid-state scanning system.

2. Description of the Related Art Solid-state scanning systems, that is, original scanning systems using solid-state sensors, have recently been actively applied to facsimile machines and copying machines.

First, the solid-state scanning method will be briefly explained with reference to FIG.

FIG. 1 schematically shows a typical optical arrangement in a solid-state scanning system, and in the figure, reference numeral L indicates a main scanning line, reference numeral 1 indicates a solid-state sensor, and reference numeral 2 indicates an imaging lens system.

The main scanning line L is a fixed linear area set at a fixed position in the device space, and the document to be scanned is scanned in a direction perpendicular to the drawing, with the surface of the document aligned with the main scanning line L. , are transported across the main scanning line L.

During scanning, the vicinity of the main scanning line, including the main scanning line L, is illuminated.

The solid-state sensor 1 includes an extremely small light-receiving element,
They are aligned in one direction and integrated, and are provided with a self-scanning function.The alignment direction of the light-receiving elements is parallel to the main scanning line L, and the light-receiving area is arranged to correspond to the main scanning line L. Ru. Here, the light-receiving area of the solid-state sensor 1 is the area where the light-receiving elements are arranged, and its length is indicated by the symbol l in the figure.

The imaging lens system 2 is provided between the main scanning line L and the solid-state sensor 1.
The arrangement position is determined so that a reduced image of the document portion on the main scanning line L is formed on the light-receiving area of the solid-state sensor 1.

Therefore, by illuminating the original, an image of the original part on the main scanning line L is formed on the light receiving area of the solid-state sensor 1, and while this is being scanned by the solid-state sensor 1,
If the document is conveyed intermittently by small distances in synchronization with the scanning speed, or if it is conveyed continuously at a speed slower than the scanning speed, the surface of the document will be scanned sequentially, and the document will be Information on the surface is sequentially converted into time-series electrical signals.

In this specification, the width of a document is defined as follows. That is, the width of the document is the length of the document in the direction perpendicular to the direction in which the document is transported.

Then, the length L _A of the main scanning line L corresponds to the maximum width of the document that can be scanned by the solid-state sensor 1 .

When an original whose width is smaller than L _A , for example, an original whose width is L _B , is scanned, the solid state sensor 1
The size of the original image on the light receiving area is less than the length l.

In this case, since both the image of the document having the width L _A and the document having the width L _B are reduced by the same magnification and imaged on the light-receiving area of the solid-state sensor 1, both documents
Although scanning is performed with the same resolution, it cannot be said that the self-scanning function of the solid-state sensor 1 is fully utilized when scanning a document having a width L _B.

That is, even when reading magnification is performed according to the width of the document to be scanned and a document having a width L _B is scanned, the length of the image formed on the light receiving area of the solid-state sensor 1 is If the length of the light-receiving area is set equal to l, all the light-receiving elements of the solid-state sensor 1 will effectively contribute to scanning, and the solid-state sensor 1
The self-scanning function of the scanner is fully demonstrated, and the scanning resolution improves as the width of the document becomes smaller.

By the way, in order to perform reading magnification according to the width of the original, it is necessary to adjust the optical arrangement of the main scanning line L, solid-state sensor 1, and imaging lens system 2 according to the width of the original. .

An object of the present invention is to provide a reading magnification method using a solid-state scanning method, which allows the adjustment of the optical arrangement described above to be carried out extremely easily and with high precision.

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

First, if we consider the size of the original, the size of the original to be scanned is generally
Standardized. For example, in our country, the above sizes are standardized according to the A size series and the B size series.

Moreover, assuming that scanning of documents is performed as part of normal office processing, the types of document sizes are often limited to at most several sizes.

Therefore, in order to simplify the explanation, in the following, we will consider a case where reading magnification is performed on two types of originals with different sizes, and for the sake of concreteness, we will change the sizes of these two types of originals to 4 in column B, respectively. The originals of this size will be referred to simply as B4 originals and A4 originals.

Furthermore, considering a set of originals that have standardized sizes and can be read and enlarged between sizes, each original that constitutes this set is defined as a rated original.

In the above example, the B4 original and the A4 original are each rated originals.

When the rated originals are A4 originals and B4 originals,
The effective length of the main scanning line L is set equal to the width of the B4 original. In FIG. 2, in the optical arrangement when scanning a B4 original, the solid sensor 1
The position of the imaging lens system 2 is shown by the solid line.

However, as shown in FIG. 2, when the A4 document is positioned at the center of the main scanning line L, the image of the A4 document on the main scanning line L overlaps and forms an image over the entire light receiving area of the solid-state sensor 1. In order to achieve this, the solid-state sensor 1 and the imaging lens system 2 must be placed at the positions indicated by broken lines.

That is, the reading magnification is changed by changing the solid-state sensor 1 and the imaging lens system 2 from one of the arrangements shown by the solid line and the arrangement shown by the broken line to the other.

If the focal length of the imaging lens system is f, the image magnification in the A4 document scanning mode is K ₀ , and the image magnification in the B4 document scanning mode is K ₁ , the imaging lens system 2, solid state sensor 1
The amounts of movement d ₁ and d ₂ are given as follows, respectively.

d ₁ = f (K ₀ - K ₁ /K ₁ K ₀ ), d ₂ = f (K ₀ - K
₁ /K ₁ K ₀ ) - f (K ₀ - _{K 1} ) If we consider this change in optical arrangement with the imaging lens system 2 as a reference, the change in the object world side of the imaging lens system 2 due to the reading magnification change. and the change in optical path length on the image field side are d ₁ = f (K ₀ - K ₁ /K ₀ K ₁ ) and d ₃ , respectively.
=f( _K0 − _K1 ).

Here, we will give specific numerical values for these quantities.

Assuming that the imaging lens system 2 has a focal length of 32,
345, and as the solid state sensor 1, we used CCD121H made by Fairchild Inc., and B4.
When 8 dots/mm is applied to the original, the above d ₁ and d ₃ become d ₁ =67.66 mm and d ₃ =0.60 mm, respectively. As solid sensor 1, manufactured by Reticon Co., Ltd.
When using PDARL 1728H, for the above conditions,
d ₁ and d ₃ are d ₁ =64.51 mm and d ₃ =0.75 mm, respectively.

As can be seen from this example, the change in optical path length when reading and changing magnification is extremely small on the image field side of the imaging lens system 2. It is difficult to move the solid-state sensor 1 by such a small distance with respect to the imaging lens system 2 to perform reading magnification.

In the present invention, this difficulty is solved as follows.

A plurality of plane mirrors are fixed on the object side of the imaging lens system, and mutually independent optical paths are set for the number of rated document types with respect to the main scanning line. Each of these independent optical paths has a predetermined magnification, and each magnification is determined by the width of the selected rated document.
It is set so that the image is formed within the light-receiving area length of the solid-state sensor. Each optical path is set to be inclined with respect to the optical axis of the imaging lens system.

The selection of each optical path is performed by moving the imaging lens system, by moving the solid-state sensor, or by integrally moving the imaging lens system and one plane mirror on the image field side.

In this way, when the optical path is selected, a conjugate relationship is established such that the image of the rated original on the main scanning line is reduced in accordance with the imaging magnification set for the optical path and is focused on the light receiving area of the solid-state sensor. Realize.

When selecting an optical path, the solid-state sensor, coloring lens system, imaging lens system, and one plane mirror on the image field side are moved so as to satisfy the following conditions.

In other words, when a solid-state sensor or the like moves, since one of the solid-state sensor and the imaging lens system is fixed, a relative displacement inevitably occurs between the solid-state sensor and the imaging lens system. The displacement is made in a direction slightly inclined with respect to the direction perpendicular to the optical axis on the image plane of the imaging lens system.

Hereinafter, description will be given based on specific examples.

FIG. 3 schematically shows an example of a reading device to which the present invention is applied.

In order to avoid confusion, the same reference numerals are used from FIG. 1 onwards for items that are unlikely to be confused.

In the figure, numeral 3 indicates a contact glass, numeral 4 a lamp, numeral 5 a slit, and numeral M
1 and M2 each indicate a plane mirror. In this example, the imaging lens system 2 is fixed at a fixed position.

By fixing the imaging lens system 2 and fixing the plane mirrors M1 and M2, two optical paths are set, but both of these two optical paths are tilted with respect to the optical axis of the imaging lens system 2. and have different optical path lengths.

That is, if the lamp 4 is made to emit light while the document O is being conveyed in the direction of the arrow to illuminate the vicinity of the main scanning line L, a part of the reflected light from the illuminated area is reflected by the plane mirror M1 and then reflected by the slit 5. The light passes through and enters the imaging lens system 2, and an image of the document portion on the main scanning line L is formed at a position indicated by symbol PA4. The optical path length at this time is A on the main scanning line L.
When there are four originals, the size of the image is set to be equal to the length l of the light-receiving area of the solid-state sensor 1.

The other part of the reflected light from the illuminated part is reflected by the plane mirror M2.
, passes through the slit 5 and enters the imaging lens 2.
, and forms a document image at the position indicated by PB4. The optical path length at this time is set so that when a B4 original is on the main scanning line L, the size of the image is equal to the length l of the light-receiving area of the solid-state sensor 1.

In the figure, the symbols S1 and S2 indicate the optical paths of the plane mirrors M1 and M2 along the optical axis of the imaging lens system 2.
This is a virtual surface showing the upper surface of the contact glass 3 when converted to an OL. Therefore, the distance between the virtual surfaces S1 and S2 is equal to the optical path length change d ₁ on the object world side of the imaging lens system 2 during reading variable magnification. Similarly,
Lens optical axis OL at positions indicated by symbols PB4 and PA4
The difference in position above is equal to the optical path length change d ₃ on the image field side of the imaging lens system 2 due to the reading magnification change.

When there is an A4 original on the main scanning line L, the effective read image at position PA4 is shown in Figure 4.
When there is a B4 original on the main scanning line L, such as IMA4, the effective read image at position PB4 becomes IMB4.

Assuming that the distance between the two is d ₄ as shown in the figure, this d ₄ is a change in the optical path length d on the image field side of the imaging lens system 2 by adjusting the arrangement position of the plane mirrors M1 and M2. ₃ , it can be made sufficiently large.

Therefore, as shown in FIG.
is moved in a direction perpendicular to the alignment direction of the light-receiving elements on the plane S3 including PA4 and PB4, and one of the two independent optical paths is set to the width of the rated document to be scanned. If selected accordingly, the reading magnification is changed and the size of the original image on the light-receiving area of the solid-state sensor 1 is always kept constant.

Now, in Fig. 5, the imaging point PA4 or
When PB4 is selected, the image plane passes through imaging PA4 or PB4 and is perpendicular to the optical axis OL. The distance between these image planes is _d3 , which is small as described above.

Further, on the surface S3, the distance between the positions PA4 and PB4 is d ₄ as described above. If the angle between the surface S3 and the image plane is θ, then Sinθ=d ₃ /d ₄ .

One of the features of the present invention is that when the optical path is selected, the relative displacement between the imaging lens system and the solid-state sensor is such that the relative displacement between the imaging lens system and the solid-state sensor is The idea is to make it occur in a slightly tilted direction. This point will be explained in the case of the above-mentioned embodiment as follows.

That is, in this embodiment, the selection of the optical path is performed by displacing the solid-state sensor 1 on the plane S3 relative to the imaging lens system 2, as is clear from the above description. Setting the direction of this relative movement to be a direction slightly inclined from the direction perpendicular to the optical axis OL on the image plane of the imaging lens system means that the angle θ is sufficiently small, This means that d ₄ ≫ _{d 3} .

The size of the angle θ is determined by the imaging lens 2 and the plane mirror M1,
Although it depends on the relative positional relationship of M2, the moving direction of the solid-state sensor 1 is slightly inclined with respect to the direction perpendicular to the optical axis OL on the image plane of the imaging lens system. The angle θ can be set because the two set independent optical paths are inclined with respect to the optical axis of the imaging lens system.

That is, in the present invention, as described above, each independent optical path is set to be inclined with respect to the optical axis of the imaging lens system, and by adjusting the relationship between each optical path, the solid-state sensor and the imaging lens are The direction of movement relative to the system is made to be slightly inclined with respect to the direction perpendicular to the optical axis on the image plane of the imaging lens.

In this way, the moving distance d ₄ of the solid-state sensor 1 due to the reading magnification change becomes sufficiently larger than d ₃ . Therefore, compared to the case where the solid-state sensor 1 is moved by a minute distance d ₃ with respect to the imaging lens system 2 and the reading magnification is changed, the reading magnification can be changed with higher precision. Moreover, the direction of movement of the solid-state sensor 1 is approximately parallel to the effective read image, and the light receiving area is set somewhere within the effective read images IMB4, IMA4. Since the width of the area is sufficiently small, the distance shown in Figure 4
For d ₅ and d ₆ , the moving distance of solid sensor 1 is approximately
It is possible to move the solid state sensor 1 roughly by d ₆ - _{d 5} , and therefore, the movement of the solid state sensor 1 with respect to the reading magnification change can be done quite roughly.

As in the example shown in FIG. 6, by fixing a plane mirror M3 to the image interface of the imaging lens system 2, the moving plane of the solid-state sensor 1 is changed from the plane S3 to, for example, parallel to the optical axis OL of the imaging lens system. It may be moved to surface S4.

In this example, the optical axis OL is also bent by the plane mirror M3, so the image plane, that is, the plane on which the image is actually formed, is a plane slightly inclined with respect to the plane S4. Therefore, in this example as well, the solid-state sensor 1 is moved in a direction slightly tilted with respect to the direction perpendicular to the optical axis on the image plane of the imaging lens system, and the solid-state sensor 1 and the optical path are The image lens system 2 moves relative to the direction perpendicular to the optical axis on the image plane of the imaging lens system in a direction slightly inclined.

In the example described above, the solid-state sensor is moved to select the optical path, but the solid-state sensor may be fixed and the imaging lens system may be moved.

The principle in this case will be explained with reference to FIG. The main scanning line L, plane mirrors M1 and M2, and solid-state sensor 1 are fixed, and two independent optical paths are set depending on their positional relationship. In the figure, the lens positions indicated by solid lines and broken lines are lens positions for image formation in each optical path. In this case, in order to select the optical path by moving the imaging lens system 2, as shown _in FIG. It should be clear from the above description that it is sufficient to move the imaging lens system from the lens position in one optical path to the lens position in the other optical path by displacing the lens by d ₇ . At this time, using the angle α in the figure, tanα=d ₃ /d ₇ , and the relative displacement between the imaging lens system 2 and the solid-state sensor is in the direction perpendicular to the optical axis on the image plane of the imaging lens system 2. On the other hand, in order to perform the scanning in a slightly tilted direction, the angle α may be made small, but this can be achieved by setting each optical path so that d ₇ ≫ _{d 3} . Such optical path setting is possible because each optical path is inclined with respect to the optical axis of the imaging lens system.

In this case, the imaging lens system 2 is aligned in the optical axis direction.
Since the reading surface is displaced by d ₃ , the distance between the reading surfaces S1 and S2 may be set to d ₁ +d ₃ . To do this, a plane including each mirror surface of plane mirrors M1 and M2,
When the intersection with the optical axis OL is P and Q, PQ=d ₁ +
All you have to do is make it d ₃ .

In order to select the optical path by moving the imaging lens system 2, the imaging lens system 2 may be displaced in a direction substantially parallel to the optical axis. FIG. 7 shows such an embodiment.

In the figure, a plane mirror M1 sets an optical path for an A4 document to the imaging lens system 2 at a position indicated by a broken line, and a plane mirror M2 sets an optical path for a B4 document to the imaging lens system 2 at a position indicated by a solid line. Lens system 2
is set for.

Switching of the optical path is performed by integrally moving the imaging lens system 2 and the plane mirror M4, which is an example of its image.

FIG. 9 is a diagram for explaining the principle of the present invention regarding the embodiment of FIG. 7.

If the amount of displacement of the imaging lens system 2 in the optical axis OL direction is d ₈ , the positions of the plane mirrors M1 and M2 must be adjusted so that the distance between the virtual surfaces S1 and S2 becomes d ₁ +d ₈ . In FIG. 9, the symbol S0 is a surface that coincides with the light-receiving surface of the solid-state sensor 1 and is nearly parallel to the image plane.

The optical axis of the imaging lens system is bent by a plane mirror M4 on the image field side of the imaging lens system. Therefore, when selecting an optical path, the imaging lens system 2 is displaced in a direction slightly tilted with respect to its own optical axis, but with respect to the optical axis on the image plane of the imaging lens 2, The relative displacement between the solid-state sensor 1 and the imaging lens system 2 is due to the optical axis on the image plane of the imaging lens system 2. For the orthogonal direction,
It is performed in a slightly tilted direction.

The angle between the moving direction of the imaging lens system 2 and the optical axis OL is tanβ=d ₃ /d ₈ , where β is the angle formed by the moving direction of the imaging lens system 2 and the optical axis OL.

In the case of the embodiment shown in FIG. 7, the imaging lens system 2 moves approximately parallel to its own optical axis, but as shown in FIG.
As is clear from looking at the mirror images 2A1 and 2A2 according to No. 4, when selecting the optical path, the mirror image of the imaging lens system 2 is moved a distance in a direction slightly tilted with respect to the direction perpendicular to the optical axis on the image plane of the imaging lens. It has moved by approximately _d8 , and is essentially the same as the principle diagram shown in FIG.

In the embodiment shown in FIG. 7 as well, by setting each optical path so that d ₈ ≫d ₃ , the amount of movement of the movable part accompanying the reading magnification change can be made sufficiently large and rough.

As described above, according to the present invention, it is possible to provide a reading variable magnification method using a solid-state scanning method, which allows optical arrangement to be performed easily and accurately in accordance with the width of a rated document.

In the above description, the case where there are two types of rated originals has been explained, but the present invention can of course be applied and implemented even when the number of types is three or more. A person skilled in the art will be able to easily determine how to specifically apply the present invention when there are three or more types of rated originals based on the above-mentioned information.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining a conventionally known solid-state scanning system, FIG. 2 is a diagram for explaining reading variable magnification and its problems, and FIGS. 3 and 4 are
An explanatory diagram for explaining the present invention, FIG. 5 is an explanatory diagram of one embodiment of the present invention, and FIG. 6 is an explanatory diagram of another embodiment of the present invention. , FIG. 7 is a diagram illustrating still another embodiment of the present invention, and FIGS. 8 and 9 are diagrams for explaining the principle of the present invention. 1... Solid sensor, 2... Imaging lens system, L
...Main scanning line, M1, M2...Plane mirror.

Claims (1)

[Scope of Claims] 1. A method for keeping the size of an image on a light-receiving area of a solid-state sensor constant regardless of the rated document width in a document scanning method using a solid-state sensor, comprising:
In a positional relationship with the main scanning line, one of the imaging lens system and the solid-state sensor is fixed, the other is movable, and a plurality of plane mirrors are fixedly installed on the object world side of the imaging lens system, Independent optical paths tilted with respect to the optical axis of the imaging lens system are set for the number of types of rated originals with respect to the main scanning line, so that the magnification in each optical path corresponds to the width of each rated original. Then, by moving the imaging lens system or the solid-state sensor, or by moving the imaging lens system and one plane mirror on the image field side together, the optical path is set according to the rated document to be read and scanned. and the solid-state sensor and the imaging lens system in the movement of the imaging lens system, the solid-state sensor, the imaging lens system, and the one plane mirror on the image field side for optical path selection. A reading variable magnification method in a solid-state scanning system, characterized in that the relative displacement with respect to the image plane of an imaging lens system is performed in a direction slightly inclined with respect to a direction orthogonal to the optical axis direction on the image plane of an imaging lens system. .