JP2552123B2 - Image projection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image projection apparatus, and more particularly to an image projection apparatus used for projecting an image on a film or the like and reading the projected image.

(Prior Art) Conventionally, as this type of device, there is the following device. That is, the image of the film is illuminated by the light source through the condenser lens, and the image of the film is projected by the projection lens through the folding mirror onto the platen glass of the reading device. At that time, since the image of the film is enlarged and projected, the image projected on the platen glass has different light directivities between the center and the periphery. Therefore,
A Fresnel lens is provided on the platen glass so as to correct this and make all the light beams enter the platen glass vertically. The image projected on the platen glass is read by a solid-state image sensor such as a CCD. By the way, the condenser lens is set so as to efficiently illuminate the film, and the condenser lens is set so as to form an image of the filament of the illumination lamp on the pupil of the projection lens.

(Problems to be Solved by the Invention) However, the related art has the following problems. That is, the image 20 of the filament of the light source.
Is set so as to be projected on the pupil 21 of the projection lens as shown in FIG. 3, so that an image projected from one point on the film has a certain area when passing through the pupil 21 of the projection lens. have. Therefore, the image from one point on the film is refracted by the projection lens 21 and, for example, the light flux R
As shown in FIG. 3, the image is projected onto Q on the Fresnel lens 22 having a small area, and is imaged on the point P on the original platen glass 23 by the Fresnel lens 22.

By the way, the Fresnel lens 22 has a saw-shaped convex portion 22.
Since a is continuously provided, the light flux projected onto the two convex portions 22a of the Fresnel lens 22 like the light flux S is reflected and scattered by the side surface 22a of the convex portion 22a, so that the light is weakened. . On the other hand, a light beam projected on one convex portion 22a like the light beam R is imaged on the original platen glass 23 as it is without being weakened due to scattering or the like, and therefore, an image projected on the original platen glass 23. In addition, there is a problem in that periodic light amount unevenness corresponding to the pitch of the convex portions 22a of the Fresnel lens 22 occurs.

Therefore, in order to solve the above-mentioned problems, the Fresnel lens 22 is installed considerably above the platen glass 23 to blur the uneven light amount, or the signal output from the solid-state image sensor is subjected to an electric shading process to obtain the light amount. It may be possible to prevent unevenness.

In addition, the size of the filament image of the light source projected on the pupil 21 of the projection lens is increased, the light amount of the light flux reaching the surface of the Fresnel lens 22 is increased, and even if there is reflection or scattering, the effect on the total light amount is increased. It is also possible to reduce.

However, in the former case, if the Fresnel lens 22 is placed considerably above the platen glass 23, the Fresnel lens 22
There is a problem that the image sharpness is lost even when the image aberration due to 22 occurs and the image is blurred or is electrically sharded.

In the latter case, since the filament image of the light source is usually a coil-shaped line image, the area cannot be increased, and even if the condenser lens is brought close to the light source to enlarge the filament image, There is a problem in that there are restrictions in the design of the optical system.

Therefore, the present invention has been made in order to solve the above-mentioned problems of the prior art. The object of the present invention is to adjust the pitch of the Fresnel lens even in an apparatus that projects an image using the Fresnel lens. An object of the present invention is to provide an image projection device capable of preventing unevenness in light quantity and easily designing an illumination optical system.

(Means for Solving Problems) In order to achieve the above-mentioned object, the present invention transmits a document illumination lamp, a condenser lens for condensing light emitted from the document illumination lamp, and a condenser lens. A projection lens for projecting an image of a transmissive original illuminated by light onto a projection target member, and a Fresnel provided between the projection lens and the projection target member for refracting a light beam transmitted through the projection lens in a predetermined direction. In an image projection device having a lens, a diffusion unit that transmits and scatters the light flux that has passed through the condensing lens is provided between the condensing lens and the transmissive original, and the transmissive original has scattered light scattered by the diffusing unit. It is characterized by being incident.

(Operation) In the present invention, the image recording medium itself emits light by diffusing the light flux from the light source by the diffusing means and illuminating the image recording medium (transmission original) with the scattered light scattered by the diffusing means. Similarly, the image of the image recording medium is projected by the entire projection lens. Therefore, the image projected on the surface of the Fresnel lens has an area larger than the pitch, and prevents unevenness of the light amount corresponding to the pitch of the Fresnel lens.

(Embodiment) Hereinafter, the present invention will be described based on the illustrated embodiment.

FIG. 2 shows an embodiment of an image reading apparatus to which the image projection apparatus according to the present invention is applied. The image reading device 1 is composed of a reading unit 2 that reads an image of a normal document and a projection unit 3 that is an image projection device that projects an image of an image recording medium such as a film. It is designed to be mounted on the reading unit 2 only when reading an image such as a film. In the projection unit 3, reference numeral 4 denotes an illumination lamp as a light source, which illuminates the film 6 via the condenser lens 5, and the image on the film 6 is projected by the projection lens 7 via the folding mirror 8 as a member to be projected. The image is projected onto the platen glass 9. On the platen glass 9, since the light beam projected on the platen glass 9 has a different angle between the central portion near the optical axis of the projection optical system and the periphery, A Fresnel lens 10 having a saw-shaped convex portion 10a is arranged so that the light flux transmitted through the projection lens 7 is directed to the reading lens 13.

Further, the reading section 1 has a reading lens 1 having a pupil 13a for reading an image projected on the platen glass 9.
3 and a solid-state image sensor 14 such as a CCD are provided, and the image on the film 6 is read by the solid-state image sensor 14.

In the present embodiment, in addition to the above configuration, a transmissive diffusing unit for transmitting and diffusing the light flux from the light source to irradiate the film is provided. That is, in the vicinity of the film 6 between the film 6 and the condenser lens 5, the surface of a transparent plate such as glass or plastic serving as a transmission / diffusion means is formed in a satin shape by sandblasting or the like so as to scatter light. A transmission / diffusion plate 15 is provided, and the light flux emitted from the illumination lamp 4 is condensed by the condenser lens 5 and then transmitted / diffused by the diffusion plate 15 to be applied to the film 6.

With the above configuration, the image reading apparatus to which the image projection apparatus according to the present embodiment is applied projects a film image as follows. That is, as shown in FIG. 1, the luminous flux emitted from the illumination lamp 4 is condensed by the condenser lens 5 and then diffused by the diffusion plate 15 to spread in four directions to illuminate the image on the film 6. . Therefore, the image on the film 6 spreads and passes through the entire pupil 7a of the projection lens 7. The light that has passed through the pupil 7a of the projection lens 7 is projected onto the Fresnel lens 10 via the folding mirror 8 and is imaged by the Fresnel lens 10 at a point B on the platen glass 9 of the reading unit 2. The image formed on the platen glass 9 is directed to the reading lens 13 of the reading unit 2.

In this way, the film 6 is illuminated by the light flux diffused by the transmissive diffusion plate 15, so that it becomes equivalent to the case where the image itself of the film 6 emits light. Therefore, as shown in FIG. 1, the image on the film 6 has a plurality of convex portions on the Fresnel lens 10 over a large area due to the entire projection lens 7.
It is projected on the area A over 10a. Therefore, even if a part of the image at one point on the film 6 is reflected or scattered by the side surface 10b of the convex portion 10a of the Fresnel lens 10, even if the amount of light changes, the influence on the total light flux is small, so that the original table glass 9 Almost no unevenness of the light quantity occurs above. Also, the diffusion plate 15
By providing the above, it is possible to reduce the coherence of the light flux from the illumination lamp 4, and also in this respect, it is possible to prevent the unevenness of the light amount of the projected image. Further, since it is only necessary to provide the transmissive diffusion plate, the optical system can be easily designed.

In the above embodiment, the case where the image projected on the platen glass is formed on the solid-state image sensor fixed by the reading lens to read the image is described, but the invention is not limited to this. Instead, the solid-state image sensor is movably arranged near the lower surface of the platen glass.
You may make it read by scanning the said solid-state image sensor. Further, it is needless to say that it can be applied to the case where the image projected on the platen glass is exposed on the photosensitive drum to copy the film image. In these cases, the projection image may be imaged on the solid-state image sensor or the like via the short-focus imaging lens.

Further, in the above-mentioned embodiment, the case where the diffusion plate is arranged between the condenser lens and the film as the transmission and diffusion means has been described. It may be formed to diffuse light. Furthermore, the diffusing means is not limited to the above-mentioned transmissive diffusing means, and for example, the mirror surface may be used as a rough surface for diffusing. However, if the transmission / diffusion means is provided, it is preferable that the light is diffused while the light flux is passing, so that the diffusion state becomes good.

(Effects of the Invention) The present invention has the above-described configuration and operation, and even in an apparatus that projects an image using a Fresnel lens, it is possible to prevent light amount unevenness due to the pitch of the Fresnel lens from occurring. In addition, it is possible to easily design the light source of the illumination system.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the operation of an embodiment of an image projection apparatus according to the present invention, FIG. 2 is a block diagram showing an image reading apparatus to which the present invention is applied, and FIG. 3 shows a conventional image projection apparatus. FIG. Explanation of symbols 4 …… Illumination lamp, 5 …… Condenser lens 6 …… Film, 7 …… Projection lens 9 …… Original plate glass, 10 …… Fresnel lens 15 …… Transmissive diffusion plate

Claims (1)

(57) [Claims] 1. An original illuminating lamp, a condenser lens for condensing light emitted from the original illuminating lamp, and an image of a transparent original illuminated by the light transmitted through the condensing lens for projecting an image on a projection target member. An image projecting apparatus having a projection lens and a Fresnel lens provided between the projection lens and the member to be projected and refracting a light beam that has passed through the projection lens in a predetermined direction. An image projection apparatus, characterized in that it has a diffusing means for transmitting and scattering the light flux transmitted through the condenser lens, and the scattered light scattered by the diffusing means is incident on the transparent original.