JPS62123866A - Original lighting equipment - Google Patents

Abstract

PURPOSE:To attain surely collimated irradiation light while reducing component cost by using a Fresnel lens manufactured simply by press processing or the like as a member collimating a diffused light from a point light source. CONSTITUTION:The Fresnel lens 2 is supported by a fixing frame 20 and a curvature adjusting device 23 adjusting the degree of curvature of the Fresnel lens 2 is provided at the middle of the frame base 21 of the fixed frame 20. In turning properly an adjusting screw 23b of the curvature adjusting device 23, the deviation of the Fresnel lens 2 from the center face is regulated in response to the adjusted quantity of the adjusting screw 23b and the broad-wise curvature of the Fresnel lens 2 is set definitely. Thus, the diffused light from a xenon lamp 1 is collimated completely by the Fresnel lens 2, reflected in a reflector 3 and the face of an original 4 is lighted by a uniform illuminance.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a document illumination device used in copying machines, facsimile machines, etc. The present invention relates to an improvement of a document illumination device that guides the document in a straight direction.

[Prior Art] A conventional document illumination device has a rod-shaped light source movably disposed at a portion facing the document surface, and by moving this rod-shaped light source, the document surface is sequentially illuminated in a slit shape. There is something I did.

However, with this type, the light source is moved directly, which not only shortens the life of the light source as it is easily cut out due to vibrations and shocks during the 8-stroke, but also has a short lifespan. The light intensity distribution tends to vary in the longitudinal direction, which causes a problem in that the illumination illuminance distribution of the document becomes non-uniform and the reading of the document image tends to be inaccurate.

As means for solving such problems, there have been proposed methods described in Japanese Patent Publications No. 53-41976 and Japanese Patent Application Laid-open No. 56-113166, for example. This uses a stable, high-output point light source instead of the rod-shaped light source, converts the diffused light from the point light source into a parallel beam of light through a reflector or collimator lens, and converts this parallel light beam into a condensing member such as a curved reflector. The light is focused in a slit shape onto the surface of the document.

[Problems to be Solved by the Invention] However, in such a conventional document illumination device, as a means for converting the irradiated light from a point light source into a parallel light beam,
Since a high-precision collimator lens and deflector are used, a problem arises in that component costs inevitably increase.

One possible solution to this problem is to create a parallel beam of light by using a Fresnel lens, which is inexpensive to manufacture. Unable to avoid the situation where field distortion occurs,
The parallelism of parallel light beams cannot be sufficiently increased. For this reason, the absolute number of parallel light beams incident on the light collecting member decreases, which not only impairs the light collecting efficiency of the light collecting member, but also reduces the light collecting efficiency of the light collecting member, especially when using a movable light collecting member. Since the amount of light incident on the condensing member varies depending on the position of the member,
This causes a problem in that the illuminance distribution on the document surface tends to become non-uniform.

[Means for Solving the Problems] This invention has been made in view of the above problems, and it is possible to ensure parallelization of irradiated light from a point light source while reducing component costs. An object of the present invention is to provide a document illuminating device that can perform the following operations.

That is, the present invention includes a point light source, a Fresnel lens that converts diffused irradiation light from the point light source into a parallel light beam, and a condensing member that focuses the light transmitted through the Fresnel lens in a slit shape on the document surface. Alternatively, assuming a document illumination device that sequentially illuminates the document surface in a slit shape by relatively moving a condensing member, the Fresnel lens may be adjusted as appropriate to correct the field distortion aberration of the Fresnel lens. It is curved.

In such technical means, the point light source is
Although various types of lamps may be used, it is preferable to use a xenon short arc lamp or an ultra-high pressure mercury lamp from the viewpoint of increasing the output and stabilizing the light output.

Furthermore, as for the above-mentioned condensing member, any member may be used as long as it converges the parallel light beam onto the document surface in the form of a slit; for example, a flapper member or a combination of a lens and a mirror may be used. It will be done.

Further, the Fresnel lens may be fixedly curved in advance at a predetermined curvature, or an adjustment mechanism may be attached to the Fresnel lens to appropriately change the degree of curvature of the Fresnel lens.

[Operation] According to the above-mentioned technical means, the diffused irradiation light from the point light source passes through the Fresnel lens and heads toward the condensing member, but the transmitted light is corrected for the field distortion aberration of the Fresnel lens. Since the light beam transmitted through the Fresnel lens is set as a completely parallel light beam in this state, the light transmitted through the Fresnel lens is reliably guided to a predetermined condensing portion on the document surface by the condensing member.

[Embodiments] Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.

FIG. 1 shows an embodiment of a document illumination device attached to a document reading device, and this document illumination device has the following features:
A xenon short arc lamp (hereinafter referred to as a xenon lamp in the examples) 1 as a point light source, a Fresnel lens 2 that converts the diffused irradiation light from the xenon lamp 1 into a parallel light beam, and the transmitted light of the Fresnel lens 2 as a document 4. It is equipped with a parabolic glue reflector 3 that focuses the light onto a predetermined slit portion of the surface, and by moving the reflector 3 with respect to the surface of the raw stone 4, the surface of the document 4 is sequentially illuminated in a slit shape. The original images from the four sides of the original are incident on the image sensor via an imaging member such as a convergent light transmitter, and are readably stored in a memory (not shown). In FIG. 1, reference numeral 11 represents a power source for the xenon lamp 1, and reference numeral 12 represents a socket for holding the xenon lamp 1.

In this embodiment, the Fresnel lens 2 is held by a fixed frame 20, particularly as shown in FIG.

The fixed frame 20 includes a frame base 21 having a rectangular opening, and is bent at both ends of the frame base 21 in the longitudinal direction, and holds both ends of the Fresnel lens 2 at the same time as the frame base 21. Holding arm 22
A curvature adjustment mechanism 23 for adjusting the degree of curvature of the Fresnel lens 2 is provided approximately at the upper center of the frame base 21. This curvature adjustment mechanism 23
A female screw portion 23a is provided approximately in the upper center of the frame base 21.
is provided, and an adjustment screw 23b that moves forward and backward in the thickness direction of the Fresnel lens 2 is screwed into this female screw portion 23a,
The tip of the adjustment screw 23b is brought into contact with the upper edge of the Fresnel lens 2, which has a substantially medium flame.

Therefore, according to the document illumination device according to this embodiment, when the adjustment screw 23b of the curvature adjustment mechanism 23 is rotated as appropriate, the Fresnel lens 23b changes as shown in FIG. The deviation f from the general plane of the central part of
f1d is constrained, and accordingly, the curvature of the Fresnel lens 2 in the width direction is set to -i. In this case, if the degree of curvature of the Fresnel lens 2 is set in advance to the extent that the field distortion of the Fresnel lens 2 is corrected, the diffused irradiation light from the xenon lamp 1 will be completely parallel at the Fresnel lens 2 portion. Reflector 3 as a beam of light
reach the part. At this time, the parallel light flux is incident on the reflector 3 without wasting it, so the light collection efficiency of the reflector 3 is maintained good, and even if the reflector 3 moves along the surface of the document 4, the reflector Since the light flux incident on the part hardly changes relative to the position of the reflector 3, the illuminance of the slit part on the four sides of the original is kept approximately equal, making the reading operation of the original image extremely stable. Become.

To give more specific numerical values, we are using a 300W xenon lamp 1, and a press-processed acrylic plate as the Fresnel lens 2, with a length, width, and thickness of 340. 70 and 4M, and the focal length was set to 220s + IC, and the distance between the light emitting part of the xenon lamp 1 and the Fresnel lens 2 was set in accordance with the focal length of the Fresnel lens 2. However, when we measured the parallelism of the parallel light flux, we found that the light flux was at an angle of ±0.5° with respect to the X direction (see Figure 1), as shown in Figure 4 (a) and (b). It was found that although it was within the range, it expanded outward at an angle of 4° with respect to the y direction (see Figure 1).

In this case, as shown in FIGS. 5(a) and (b),
When the xenon lamp 1 is placed at an appropriate distance from the Fresnel lens 2, the light beam that was expanding outward will gradually become parallel in the y direction, but due to the influence of field distortion of the Fresnel lens 2, In particular, on both sides of the Fresnel lens 2 in the longitudinal direction, the light beam is converged inward in the X direction. In this state, the center position of the Fresnel lens 2 was shifted by d = 8 mm to the opposite side of the xenon lamp 1 by appropriately operating the curvature adjustment mechanism 23, as shown in Fig. 6 (aH
As shown in b), it was confirmed that the transmitted light beam of the Fresnel lens 2 becomes a reliable parallel light beam in the X direction and the y direction.

In this embodiment, the Fresnel lens 2 is curved in its longitudinal direction to correct field distortion of the Fresnel lens 2, but the invention is not limited to this. For example, the Fresnel lens 2 can be curved in its longitudinal direction. It is also possible to correct field distortion by curving it in the width direction.

[Effects of the Invention] As explained above, according to the document illumination device according to the present invention, a Fresnel lens that is easily manufactured by press processing or the like is used as a member that collimates the diffused irradiation light from a point light source. As a result, the parts cost is cheaper,
The device cost can be reduced.

Further, according to the present invention, since the field distortion of the Fresnel lens is effectively corrected, collimation of the irradiated light from the point light source can be reliably realized. For this reason,
A parallel beam of light can be incident on the condensing member without waste,
Therefore, not only can the light collection efficiency of the light collection member be improved, but also the amount of light incident on the light collection member can be kept constant.
It is possible to suppress variations in the width of the light condensing portion, and it is possible to keep the illuminance of the illuminated portion of the document approximately equal.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view showing an embodiment of a document illumination device according to the present invention, FIG. 2 is a perspective explanatory view showing an example of a support structure for a Fresnel lens according to the embodiment, and FIG. -■ line sectional view, Figures 4 (a) (b) and 5 (a) (b)
is the X of the light transmitted through the Fresnel lens in each different conventional example.
Graph explanatory diagram showing parallelism in direction and X direction, Fig. 6 (
FIGS. 2A and 2B are graph explanatory diagrams showing the X direction and the parallelism in the X direction of light transmitted through a Fresnel lens in an example according to the present invention. [Explanation of symbols] (1)...Xenon short arc lamp (point light source) (2)...Fresnel lens (3)...Reflector (light condensing member) (4)...Manuscript patent applicant Fuji Representative of Xerox Corporation
Patent attorney Tomohiro Nakamura (2 others) Figure 3 Figure 4

Claims (1)

[Claims] It is equipped with a point light source, a Fresnel lens that converts the diffused irradiation light from the point light source into a parallel light beam, and a condensing member that converges the light transmitted through the Fresnel lens onto the document surface in a slit shape. A document illuminating device that sequentially illuminates a document surface in a slit shape by moving the document illuminating device, characterized in that the Fresnel lens is appropriately curved so as to correct field distortion of the Fresnel lens. Manuscript illumination device.