JPS6326648A - Mirror image forming device - Google Patents

Abstract

PURPOSE:To execute good orthochromatic filtering in a state that conjugate length of an existing optical system has been held, and to improve the image forming performance, by providing a filter means on an image inverting prism itself. CONSTITUTION:A mirror image forming device 10 is constituted of a lamp 11 provided with a reflecting mirror 12, a focusing optical transmission body array 13, and an image inverting prism 14 having a filter means. By mixing uniformly a transition metal ion, a rare earth ion, etc., for instance, mainly composed of Fe, having an absorption band in a near infrared area, into optical glass which becomes a base, an optical filter element having a desired spectral transmissivity is obtained, and it becomes the filter means provided on said image inverting prism 14. In this way, since an optical absorber for absorbing a light beam of a specific wavelength area has been mixed uniformly into the optical glass of the prism material, a uniform spectral transmissivity is easily obtained on the whole surface, and also, each face of the prism has flatness of high accuracy by grinding therefore, comparing with a plate glass filter, deterioration of the image forming performance is not generated at all.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an imaging device, and particularly to a mirror image forming device that can create a printing original using an electrophotographic process such as a copying machine or a printer.

- Rice technique and back weight technique 1 In general, when creating a master plate for offset printing, a simple method is to use a copying machine. However, although the original plate for offset printing is required to be a mirror image, a normal copying machine can only produce an erect image, as can be seen from FIG.

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 prism for image reversal is installed between a lens array and an object surface or an image surface. What has been established is known. However, this method has a disadvantage in that the angle of view is large due to the use of a lens array, which leads to an increase in the size of the prism and thus the size of the imaging device.

Therefore, in order to eliminate this drawback, a technique using a converging light transmitting element array as an imaging element has been considered.This allows the optical path length between the object surface and the image plane to be shortened, and the prism for image reversal can also be used. The device itself can be made smaller, and the device itself can be made smaller.

By the way, copy 8 as above! In devices such as those that form a document image on an image receptor (for example, a photoreceptor) to obtain a desired copy image, the imaging light is In order to appropriately correct the spectral distribution, a correction filter element is usually interposed in the optical path of the optical system. Conventionally, this filter element has generally been formed by depositing a multilayer film on a plate glass.

Problems that Ming attempts to solve However, there are problems in using a multilayer film-deposited glass filter in the optical system of a printing press for a light printing system using the above-mentioned PPC process. First, forming a multilayer film on a plate glass by vapor deposition is preferable because the film configuration can be freely selected and a variety of spectral characteristics can be achieved, but on the other hand, the plate glass itself has variations in flatness and thickness, resulting in poor imaging performance. This is a problem that requires strict management as it causes deterioration. Second, since a flat glass is inserted into the optical path of the optical system, the imaging optical path length increases, which is undesirable from the standpoint of miniaturization, and if the optical system is based on an already established design, the optical design The problem is that a slight modification of the optical system forces a major change not only in the optical system but also in the structure, including the optical system, as people often say.

The present invention aims to eliminate the above two problems with ItVi at the same time.

Means for Solving the Problems Therefore, the present invention provides a convergent light transmitter array interposed between the object surface and the image plane, and also provides a means for interposing the convergent light transmitter array between the object surface or the image plane. In a mirror image forming device in which an image reversal prism is installed on the optical path between the image surfaces, we focused on the image reversal prism, which is made of optical glass whose optical performance is strictly controlled and whose surfaces are precisely polished. The basic feature is that the image reversing prism is provided with a filter means for absorbing light in a specific wavelength range so as to match the spectral sensitivity of the photoreceptor forming the image reversing prism.

FIG. 1 shows an embodiment of the mirror image forming device according to the present invention,
Above is the document table glass (1), below is the photosensitive drum (
2) is installed, and the whole is configured as an electrophotographic copying machine. It should be noted that the Vt regulation around the photoreceptor drum including the charging unit 2 is well known in terms of I/%, and the explanation thereof will be omitted.

The mirror image forming device (10) includes a lamp (11) with a reflection fi<12), a convergent light transmitter array (13), 7
It consists of an image reversing prism (14) having 4717 means.

The lamp (11) irradiates light focused by a reflecting mirror (12) onto the back surface of the document table glass (1) in a slotted manner. The original placed on the original platen glass (1) is moved by the arrow (a) of the original platen glass (1) by this lamp (11).
), (a') directions, the light is sequentially irradiated in a slit-throat pattern.

The convergent light transmitter array (13) is made up of a large number of single convergent light transmitters (for example, product name: Cell 7ttsu) converged, and includes a document table glass (1) and a photoreceptor drum (2). )
The light reflected from the document table glass (1) is guided onto the photosensitive drum (2) to form a document image. At this time, it goes without saying that the photosensitive drum (2) is rotationally driven in the direction of the arrow (b) at the same speed (peripheral speed) as the original platen glass (1).

The image reversing prism (14) is held in a holder (15),
The holder (15) is installed on the optical path between the convergent light transmitter array (13) and the photosensitive drum (2), and the holder (15) is positioned and fixed at the optimum position of the machine body at both ends thereof.

In a normal copying machine, as shown in Fig. 2, scanning exposure is performed to create a mirror latent image, and this is visualized and transferred to paper to obtain an erect image.On the other hand, as in the present invention, To obtain a mirror image as a transferred image to a transfer medium including paper (such as when creating an original for offset printing), image reversal prism (14) is placed on the optical path and image exposure is performed (see Figure 3). In the case of these image exposures, if the rotation direction of the photoreceptor drum is constant in the direction of arrow (b), the direction of movement of the platen glass is in the direction of arrow (,) when creating an erect image, and in the direction of arrow (,) when creating a mirror image. The time is indicated by an arrow (a゛), indicating the opposite direction. Also, in Fig. 2 and Q'S3, (X) is the original image, (Y) is the exposure image, (21) is the object surface, (22) indicates the image plane.

Next, the prism used in the present invention will be explained.

In general, copy 8! In such an imaging device, an odd number of reflection system may be used to obtain a mirror image. Therefore, if a prism is used to simply obtain an odd number of reflection system, a doped prism (P,) as shown in FIG. 4 can be used. However, when using an imaging element with a shallow focusing depth such as a convergent optical transmitter array as in the present invention, the image plane may be shifted vertically and horizontally due to non-linear aberrations caused by the prism. However, since the pin F does not come out at the same time, the resolution is adversely affected, which is not preferable. Therefore, a prism (P2) that does not cause astigmatism as shown in FIG. 5 may be used. This prism (P2) has parallel planes at which light enters and exits, and the apex angles (φ) at both ends are equal.

On the other hand, when light passes through a substance with a refractive index greater than 1 (the refractive index of all substances is greater than 1), the apparent conjugate length becomes shorter. However, it is preferable in terms of mechanical configuration that the apparent optical path length does not change depending on the presence or absence of the prism. In order for the apparent optical path length to remain unchanged, (x++x2+a++az)/Na = (Xl + X2 + (at + a2)/c
os2θ]/N ・−・−・■ However, Na: the refractive index of air, N, and the refractive index of the nibliism medium only need to hold. Furthermore, in order for the optical axis position not to change, a, = a2 = a ......
The height H) from the bottom surface of the prism to the optical axis may be selected so that (2) holds true. If the above-mentioned condition (2) is satisfied, the optical axis position will not change regardless of whether the shape of the prism is symmetrical or asymmetrical. FIG. 6 shows a prism (P,) that meets these conditions.

Here, a design example of the prism (P,) will be shown. Note that in this design example, the shape is asymmetrical in consideration of the spread of the luminous flux.

Material: BK7 (Refractive index: 1.5188) φ: 60
゜L: 15ff1m a: 3.88fflII H: 8.81m x: 2.24mm The distance from the image plane and the optical axis can be kept constant, which makes it easy to integrate into existing image forming devices, and there is no astigmatism when using the prism.
Obtain good imaging.

The above prisms (P2) and ('Pa1) are integrally shaped as pentagonal prisms, but from the viewpoint of manufacturing such as surface polishing and cost, as shown in FIGS. 7 and 9, The prism (P,) may be formed by dividing it into a triangular prism (P31) whose cross section is the triangle ABC and a quadrangular prism (pi2) whose cross section is the quadrangle BEFD in advance, and then gluing these two parts together. . Adhesion is performed using an adhesive such as Ceramic Bond or 7 Otobond (trade name), which is equivalent to optical glass.

The above are the geometrical optical characteristics of the image reversing prism (14). Next, the filter means provided in this image reversing prism (14) will be explained.

Generally, photoconductors for copying machines are C, (S-based).

Se-based or organic semiconductor-based materials are used, and the light source is generally a halogen lamp (the lamp (11) in FIG. 1 is also a halogen lamp). The spectral distribution characteristics of this halogen lamp have a peak on the long wavelength side, that is, around 800 to 900 nm, and decrease uniformly on the shorter wavelength side. Therefore, in order to correct the relative luminous efficiency of the spectral distribution characteristics of the light incident on the photoreceptor, the near-infrared region (750t+m~3μ
m) Cuts the light. This is done using colored optical glass, that is, by uniformly mixing transition metal ions, rare earth ions, etc., which have an absorption band in the near-infrared region, such as Fe, etc., into the base optical glass, the desired spectral transmission can be achieved. An optical filter element having a ratio of In the embodiment shown in FIG. 7, a triangular prism (P3.
) was created as described above. The spectral transmittance distribution characteristics are shown in FIG.

In this way, if a prism is made of optical glass, which is the prism material, and a light absorber that absorbs light in a specific wavelength range is uniformly mixed therein, it is easy to obtain a -like spectral transmittance over the entire surface.
Furthermore, since each surface of the prism has highly accurate flatness due to polishing, there is no deterioration in imaging performance compared to the plate 7y7 filter. Furthermore, compared to the vapor-deposited multilayer film described later, it is necessary to strictly control the film thickness (changes in spectral transmittance are observed when the film thickness varies); Uniformly dispersed mixing eliminates the hassle of manufacturing and management.

In the example of FIG. 7, only the triangular prism (P3.) is shown as the prism in which the light absorber is mixed, but it is also possible to have only the square prism (P32), or both may be in this mixed form. That is, when the image reversing prism (14) is constructed with two parts, at least one of the prisms is made with a light absorber mixed therein.

Another embodiment, as shown in FIG. 9, is to apply a trichromatic multilayer coating to the prism (P3). Coating is done by vapor deposition.

A surface including side AB of a triangular prism (P: 11) (a part through which the image light flux passes is shown in the illustration) or side BC
For example, MgF2 and Sub, I on the surface containing λ.

/4 (λ.: dominant wavelength) and are alternately deposited to form a multi-NJ film (C0) or (C2). FIG. 10 illustrates a six-layer structure. In addition to the entrance part of the prism, the output part is also functionally equivalent, so a similar film structure can be deposited on the surface including the side DF (the part through which the image light flux passes is shown in the figure). may be applied to form multilayer g(C3).

By the way, since the surface including the side EF deviates from the total reflection condition, it is usually made into a mirror surface by coating it with a metal film such as ALAg. However,
Instead of this simple mirror surface, for example, P b F
x and S ub, I as λ. The first layer and the final layer are deposited alternately with a film thickness of /4 (λ.: dominant wavelength), and the first layer and the final layer are
. /811Q, the surface including side EF (a part in the figure) can be made into a multilayer interference film mirror (C4). This multilayer Y film mirror (C4) selectively transmits only the light of the necessary wavelength. This allows for color correction. $1
Figure 1 shows the case of a 15Wi configuration. In addition, the 9/l S
i The O2 film is used to prevent film cracking. FIG. 12 shows an example of spectral transmittance distribution characteristics based on color-coating in a mirror image forming device using an organic photoreceptor drum and a halogen lamp.

By depositing an appropriate material on the prism in this way, it is possible to perform the desired color correction, and compared to a plate plus, each surface of the prism is polished, so there are no problems with flatness. It is advantageous for downsizing the optical system because there is no increase in the apparent optical path length due to the addition of extra flat glass, and it also increases the cost of installing an independent filter element or modifying the structure to add filter function. Considering this, it has advantages such as significantly lower cost.

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

λ Absorption Δ Processing As is clear from the above explanation, according to the present invention, the image reversal prism itself is provided with a filter means, so that the existing optical system can be improved without increasing the apparent optical path length. It is possible to perform good color matching filtering while maintaining the conjugate length, and it is possible to improve imaging performance while maintaining a compact configuration.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of a mirror image forming apparatus according to the present invention, FIG. 2 is an explanatory diagram of an image forming state in a copying machine using a cell 7 network, and FIG. 3 is an explanatory diagram of an image forming state of the embodiment. figure,
4, 5, and 6 are explanatory diagrams of an image reversing prism, FIG. 7, and FIG. 59 are explanatory diagrams of an image reversing prism according to another embodiment, and FIG. 10. FIG. 11 is an explanatory diagram of a vapor-deposited coating film, FIG. FIG. 12 is a graph showing the spectral transmittance distribution characteristics of the imaging light. (1)... Original table glass, (2)... Photosensitive drum, (10)... Imaging device, (11)... Lamp, (
13)...Focusing light transmission body array, (14)...Image reversing prism, (21)...Object surface, (22)...Image surface, (X)...Document image, ( Y)...Exposure image, (P
l), (P2), (P,)...prism, (Pco,)
...Triangular prism mixed with light absorber, (CI), (
C2), (C3), (C,)...Multilayer film by vapor deposition.

Claims (1)

[Claims] (1) A convergent light transmitter array is interposed between the object surface and the image plane, and a prism for image reversal is provided on the optical path between the convergent light transmitter array and the object surface or the image plane. A mirror image forming device, characterized in that the image reversing prism is provided with a filter means for absorbing light in a specific wavelength range so as to match the spectral sensitivity of the photoreceptor forming the image plane.