JPS63125931A - Image forming device - Google Patents

Abstract

PURPOSE:To generate an erect and a mirror image selectively and to generate even an image of variable magnification by providing an image inverting prism so that it moves away from an optical path and also a lens for varying image magnification on the optical path so that it can moves onto and away from the optical path. CONSTITUTION:When the erect image is obtained (in normal copy formation), a solenoid 17 is turned on to move the image inverting prism 14 away from the optical path and lenses 21 and 22 are moved away from the optical path similarly to perform image exposure. When a 1:1, i.e. life-size mirror image is obtained, the solenoid is turned off and only the image inverting prism 14 is put on the optical path to perform image exposure. Then when a mirror image of specific magnification is obtained (at the time of the formation of a negative plate for special purpose such as offset printing and design, the solenoid 17 is turned off to put the image inverting prism 14 on the optical pat, and the lens 21 and 22 are moved onto the optical path to perform image exposure. Consequently, images of variable magnification are obtained and the erect image and mirror image can be selected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an imaging device, particularly to an imaging device used in an imaging device such as a copying machine or a printer.

In general, when creating original plates for offset printing, a simple method is to use a copying machine. However, an original plate for offset printing is required to be a mirror image, whereas an ordinary copying machine can only produce an erect image.

By the way, as an image forming device for a copying machine that obtains a mirror image, as described in Japanese Patent Publication No. 48-35503, a converging light transmitting body consisting of a group of convex lenses arranged in an array and an object surface or A structure in which a fixed image reversing prism is provided between the image plane and the image plane has been proposed.

However, this imaging device only has the function of obtaining a 1:1 mirror image, and cannot obtain an erect image, which is a normal function of a copying machine. It is also not possible to obtain a variable magnification image, which has the problem that its use as an image forming device is extremely limited.

Therefore, the imaging device according to the present invention has a structure in which the focusing light transmitting member and the object surface or the image surface are A lens for changing the image magnification is movably provided on the optical path, and an image reversing prism is installed on the optical path so that an erect image and a mirror image (including a magnified mirror image) can be selectively obtained. Its basic feature is that it can be evacuated.

Fig. 1 shows an embodiment of the imaging device according to the present invention, with a document table glass (1) at the top and a photoreceptor drum (2) at the bottom.
is installed, and the entire machine is configured as an electrophotographic copying machine. Note that the structure around the photoreceptor drum is well known, and a description thereof will be omitted.

The imaging device (10) includes a lamp (
11), a converging light transmitter array (13), an image reversing prism (14), a lens for changing image magnification (21), (
22).

The lamp (11) irradiates light focused by a reflecting mirror (12) onto the back surface of the document table glass (1) in the form of a slit. The original placed R on the original platen glass (1) is moved by this lamp (11) to the arrow (a) on the original platen glass (1).
, (a') direction, the light is sequentially irradiated in a slit shape.

The convergent light transmitter array (13) is made by converging a large number of single convergent light transmitters (for example, product name: Cell 7-Sai Tsuku) into an array shape, and is connected to the document platen glass (1) and the photosensitive material. The photoreceptor drum (2) is installed to guide reflected light from the document table glass (1) onto the photoreceptor drum (2) to form an image of the document. At this time, it goes without saying that the photosensitive drum (2) is rotated in the direction of the arrow (b) at the same speed (peripheral speed) as the original table glass (1).

The image inversion prism (14) is held in a holder (IS),
It is installed movably on the optical path between the convergent light transmission body array (13) and the photosensitive drum (2). For more information,
The holder (15) has guide rails (16) fixed to the machine body at both ends, and arrows (A) and (A) on the guide rails (16).
') direction, and a solenoid (17) is connected to the central part of the back surface of the holder (15).

On the other hand, the holder (15) is always urged in the direction of the arrow (A) by springs (19) whose ends are locked to the bins (18) on both sides, and the holder (15) is attached to the positioning member (20) fixed to the machine body. The position is regulated by the contact between the front end portions of 15). Although not shown, the spring (19) and the positioning member (20) are also installed on the rear side in Figure m1.

That is, the image reversing prism (14) is the solenoid (17)
When the is turned off, the arrow (
A), the position is regulated by the positioning member (20), and the image forming device is positioned on the optical path of the imaging device. When the solenoid (17) is turned on, its driving force moves the direction indicated by the arrow (A).
slide in the direction and retreat from the optical path.

The lenses (21) and (22) for image magnification are arranged such that one lens (21) is placed between the document table glass (1) and the convergent light transmitting array (13), and the other lens (22) is held together by a holder having the same structure as the prism holder (15) so that it is located above the prism (14) at the opening between the converging light transmitting body array (13) and the photosensitive drum (2). The prism is moved forward and backward on the optical path between the document platen glass (1) and the photosensitive drum (2) by a mechanism similar to that of the prism. Lens (21), (22)
As can be seen from FIG. 2(A), which shows the optical transmission system, both are composed of spherical lenses (21s) and (22s) (the embodiment shown in FIG. f51). As another example, a cylindrical lens (21c) as shown in FIG. 2(B), (
22c) may be used to create a vt.

In the above configuration, in order to obtain an erect image (during normal copy creation), the solenoid (17) is turned on to retract the image reversing prism (14) from the optical path, and the lens (21) is moved in the same manner. ), (22) are removed from the optical path and image exposure is performed (see FIG. 3 (A1)).

In addition, to obtain a 1:1 mirror image (when creating a master plate for offset printing), image exposure is performed by turning off the lens maid (17) and allowing only the image reversing prism (14) to enter the optical path. (See Figure 3 (82)). In order to obtain a mirror image that has been magnified at a predetermined magnification (when creating original plates for special purposes such as offset printing or design), a solenoid (1
7) is turned off and the image reversing prism (14) enters the optical path, and the lenses 'X (21) and (22) enter the optical path to perform image exposure (': Figure 53 (A3) , see Figure 3(B)). f53 diagram (A3) is the lens (21)
, (22) are spherical lenses, and the image is magnified in two directions, vertically and horizontally (in the figure, it is reduced but includes enlargement). On the other hand, FIG. 3(B) shows a lens (21).

(22) is the case of a cylindrical lens, and the image is magnified in one direction, either vertically or horizontally (in the figure, it is a reduction in the vertical direction, but it also includes enlargement, and it also includes cases of scaling in the horizontal direction). Ru.

In the case of these image exposures, if the direction of rotation of the photosensitive drum is constant in the direction of arrow (b), the direction of movement of the document table plus is in the direction of arrow (a) when creating an erect image, and in the direction of arrow (a) when creating a mirror image. is an arrow (a゛) and is in the opposite direction. Also, f
In FIG. 53, (X) is a document image, (Y) is an exposure image, (23) is an object plane, and (24) is an image plane.

Generally, when light passes through a substance with a refractive index greater than 1, the apparent conjugate length becomes shorter.

However, it is preferable that the apparent optical path length does not change depending on the presence or absence of the prism (14) and lenses (21) and (22) due to the mechanical configuration. In this embodiment, from this point of view, conditions are set that allow for variable magnification while preserving the conjugate length by combining positive and negative lenses.Furthermore, in the prism (14), the refractive index of the prism medium and the angle of incidence are set. And by selecting a shape that defines the reflection point in the optical axis direction, the optical path length is kept unchanged.

Furthermore, the prism (14) has a shape that also takes into account the effect of employing the convergent light transmitter array (13) as shown in the embodiment for the purpose of compactness. That is,
When using an imaging element with a shallow depth of focus, such as a converging light transmitter array, the astigmatism caused by the prism causes the image plane to shift vertically and horizontally, and at the same time it is out of focus, which has a negative impact on resolution. . Therefore, as shown in the embodiment, a prism is used in which the light input and output end surfaces are parallel planes and the apex angles at both ends are equal, so that astigmatism does not occur. In addition, in consideration of ease of design, conditions were selected that would not change the optical axis position on the exit surface, and the shape was asymmetrical in consideration of the spread of the light flux. Various design considerations regarding the image reversing prism (14) apply similarly to the embodiments described below.

5 and 6 show other embodiments regarding the arrangement of lenses (21) and (22), and FIG. 4 is a longitudinal sectional view of the optical transmission system according to the embodiment of FIG. 1. As shown in Figure 5,
A lens (22) may be placed between the image reversing prism (14) and the image plane (lens (22')), as shown in Fig. 6, with the image reversing prism (14) sandwiched in the middle. and the lens (
21'') and (22'') may be provided.

In the embodiments described above, the lenses having positive and negative refractive powers are arranged in order from the document surface side, but it is of course possible to arrange the lenses in the order of the negative lens and the positive lens. Also, positive.

Negative lenses are used as a set, but positive, positive or negative,
A negative combination may also be used. Alternatively, if the focus is simply on the variable magnification function, either a positive or negative lens may be used.

According to the above embodiment, a life-sized erect image, a 1:1 mirror image,
It is possible to selectively obtain a magnified mirror image and a magnified erect image surround, which greatly improves the functionality of the imaging device.

Next, other embodiments of the imaging device according to the present invention will be described with reference to FIGS. fpJ7 to FIG. 14.

As shown in FIG. 7, this embodiment differs from the embodiment in which the lenses in FIG. It is something. Before other configurations, the same reference numerals indicate the same or equivalent parts as in the ptSi diagram,
Detailed explanation will be omitted.

FIG. 8(A) shows a perspective view of this image reversing prism. The prism has a spherical lens part (14s+) on the light beam entrance surface, and also a spherical lens on the exit surface? )1((14sz)
have. FIG. 8(B) shows another embodiment, in which the prism (14) has cylindrical lens portions (14c+) to (14c2) on the light exit surface, respectively.

In this configuration, in order to obtain an erect image (during normal copy production), the solenoid shown in FIG. (See Figure 1o (At)).

On the other hand, in order to obtain a magnified mirror image (such as when creating an original for offset printing), the solenoid (17) is turned off and the image reversing prism (14) enters the optical path to perform image exposure (10th prism). (See Figure (^3) and Figure 10 (B)). 10th
In the case of figure (^3), the prism has a spherical lens part (14s
,).

(14s2), the projected image becomes a mirror image that is scaled vertically and horizontally at a predetermined magnification (reduction includes enlargement), and the first
In the case of Figure 0 (B), the cylindrical lens part (14c, ), (
14c2), a mirror image whose magnification is varied (preferably including reduction and enlargement) at a predetermined magnification in the scanning direction (one direction) of the original image is obtained. If this latter case is adopted, useful functions can be achieved during printing. In other words, when an original plate is printed on a printing machine, the image generally stretches in the paper feeding direction. It is possible to correct the elongation of printed images, eliminating the need for precise and complicated adjustments such as corrections during printing.

FIGS. 12 to 14 show main parts of other embodiments.

Figure 12 shows an image reversing prism with negative refractive power on the light exit surface, Figure 13 shows a prism with positive power on the entrance surface and negative power on the exit surface, and Figure 14 shows an image reversing prism with negative refractive power on the exit surface. The entrance surface has negative power and the exit surface has positive power.

In addition, in the embodiments shown in FIG. 11 (side view of FIG. For the purpose of variable magnification, it is sufficient to form the curvature surface on one of the end faces.

By the way, when a lens portion is formed on the light flux input/output end face of the prism as described above, the image plane (24) generally moves. This characteristic is that when the power of the lens portion is positive, the image plane approaches and the conjugate length decreases. Conversely, when the power of the lens portion is negative, the image plane moves away and the conjugate length increases. Therefore, assuming that the mechanical configuration shown in Fig. 9, in which the prism does not have a lens part, has already been completed, it would be desirable to replace only the prism without changing this configuration, but instead of replacing the prism with a lens part. It is necessary to correct the optical path length so that the image plane does not move even if it is inserted into or removed from the optical path.

As a specific method, in the embodiment for the configuration shown in FIG. 9, the optical path length is corrected by increasing or decreasing the overall length (Lo) of the prism (14).

In other words, the prism shown here is made of optical plus such as BK7 or plastic, but these media have a higher refractive index than air (2 spaces), so these media can be used as an alternative to air. If the space is filled with , the air-equivalent distance will be shorter than the apparent optical path length. For example, if the prism medium is BK7, the refractive index n is 1.5168,
The air equivalent distance to the length l is 1/n. The difference Δ
Since Δ1=1-1/n=0.341N, p is 0
．． 34H! The optical path length can be shortened by

Using this, when the power of the lens part is positive, change the length of the prism (see Figure 11, Ll). ), when the power is negative, the image plane position can be maintained constant by shortening the length of the prism (see Figure @12, L2<L.). This makes it extremely easy to change the design of the configuration shown in Figure 9, and it is also possible to add a prism with a lens to the configuration shown in Figure 9 (in the figure, the prism can be moved forward and backward from the left side on the optical path). Even in the case of 1), there is no need to make any major changes to the structure.

Note that the imaging device according to the present invention is not limited to the various embodiments described above, and can be variously modified within the scope of the gist. For example, an image reversing prism (14) may be provided between the document table glass (1) and the convergent light transmitter array (13).

Effects of the Invention As is clear from the above explanation, since the present invention provides an image reversing prism that can be retracted from the optical path, it is possible to selectively create an erect image and a mirror image, which is particularly useful for offset printing. An original version can be easily created. moreover,
Since a lens for changing the image magnification can be inserted into the optical path, it is also possible to create a magnified mirror image.For example, according to a preferred embodiment of the present invention, image distortion during printing can be corrected in advance when creating the original plate. You can keep it.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of an imaging device according to the present invention, FIG. 2(A) is a perspective view showing an optical transmission system thereof, and FIG.
B) is a perspective view of the optical transmission system of another embodiment, Figure 13 (^1)
, (^2)l(^3) and Fig. 3 (B) are explanatory diagrams of the imaging state, Fig. 4 is a longitudinal cross-sectional view of Fig. 2 (A) or (B),
FIGS. 5 and 6 are longitudinal sectional views of other embodiments of lens arrangement. @Figure 7 is a perspective view of another embodiment, and Figure 8 (A
) is a perspective view of only the image reversing prism, @8 (B) is a perspective view of an image reversing prism according to another embodiment of this type, 1
Figure 9 is an explanatory diagram of a design example in which the image reversing prism is retractably provided, Figure 10 (Δ1), (A3) and Figure 1/10 (B
)1. Image L! l) Theory [IJ[1J11 is based on Figure 8 (
A) or (B) side view, Fig. 12, Fig. 13, Fig. 1
FIG. 4 shows a side view of a prism according to still another embodiment. (1)...Original table is lath, (2)...Photoconductor drum, (10)...Imaging device, (11)...Lamp, (
13)...Focusing light transmission body array, (14)...Image reversing prism, (17)...Solenoid, (19)...
... Spring, (20) ... Positioning member, (23
)...object surface, (24)...image surface, (21), (22
)...Lens for changing image magnification, (14s+), (14
s2), (14c+L(14cz)...lens portion formed on the image reversing prism, (X)...original image, (Y)
...Exposure image.

Claims (1)

[Claims] (1) A converging light transmitting body is interposed between the object plane and the image plane, and an image reversing prism is provided on the optical path between the converging light transmitting body and the storeroom or the image plane to obtain a mirror image. An imaging device, characterized in that the image reversing prism is provided retractably from the optical path, and a lens for changing image magnification is provided retractably on the optical path.