JPH04311149A - Image illuminating device, image reader and converging element - Google Patents

Abstract

PURPOSE:To obtain high illumination efficiency without generating a shadow while holding the merit of a single-side illuminating light source. CONSTITUTION:An in-line type plate-like converging element part A is arranged on one side of an image forming light beam in the front of an image reading position and an, off axes type plate-like converging element part B is formed on the other side of the light beam. Both converging elements A, B are unitedly formed on a transparent base 5. The illuminating light source 2 is arranged on the side of the element A so as to illuminate a position 3 to be read out from both sides.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image illumination device, an image reading device, and a condenser, and more particularly to an image illumination device, a condenser, and an image reading device as illumination optical components in an image reading scanner. For example, it is applied to various scanners.

0002

2. Description of the Related Art As a prior art related to the present invention, for example, an "image reading device" is proposed in Japanese Patent Laid-Open No. 1-179658. This publication relates to an illumination device in which the inner surface of the case that holds the components is mirror-finished, but the specularly reflected light from the light source directly enters the imaging element, and the amount of light other than the effective light beam becomes stray light, which causes the sensor to The disadvantage is that the light reaches the surface and becomes flare light, which lowers the S/N ratio of the scanner.

FIGS. 10 and 11 are block diagrams showing a conventional 1-magnification scanner unit. In the figures, 21 is a document support glass;
22 is an illumination light source (LED array), 23 is a reading position, 24 is a reflection mirror, 26 is a 1-magnification line sensor, 26 is a roof mirror lens array (RMLA), 27 is a housing, and 28 is a 1-magnification imaging element ( It is a gradient index rod lens array). FIG. 10 shows LE as the illumination light source 22.
The document is supported on the last surface 21 using light emitting elements such as D arrays.
The above document is illuminated, and the light information is sent to the same-magnification line sensor 25 using a roof mirror lens array (RMLA) 26.
It shows a scanner configuration that forms a life-size image on the top and reads the optical signal. FIG. 11 shows another configuration in which a gradient index rod lens array is used as the equal-magnification imaging element 28 in a similar equal-magnification scanner unit. In both types of configurations, the illumination source, such as an LED array, is typically located on one side. The reason for this is the miniaturization and cost reduction of the unit. However, with one-sided illumination, the amount of illumination light is limited compared to double-sided illumination, and when using a document with steps (for example, a cut document), the stepped portions may create shadows and cause black lines on the scanned image. It appears. Particularly in image scanners, plate-making scanners, and the like, the occurrence of shadows is a fatal drawback.

FIG. 12 shows a fixed CCD dedicated to sheet feeding.
13 is a diagram showing a conventional example of a (Charge Coupled Device) scanner, and FIG. 13 is a diagram showing a conventional example of a document fixed mirror scanning type CCD scanner. In the figure, 31 is a document support glass, 32 is an illumination light source, 33 is a reading position, 34 is a condenser lens, 35 and 38 are mirrors, 36 is a lens, and 37 is a CCD (charge coupled device).
It is.

FIG. 14 is a block diagram of a conventional image illumination device. In the figure, reference numeral 29 indicates an effective light beam, and other parts having the same functions as in FIG. 10 are given the same reference numerals. The luminous flux from the LED light emitting element exhibits diffuse emission characteristics having a wide emission angle, and usually exhibits an illuminance distribution over a wide area on the document surface. Since the reading line used is an extremely narrow area, the illumination efficiency is low and the amount of light outside the effective area reaches the sensor surface as stray light. There is light reflected from the back surface of the glass L2 in FIG. 14, and diffusely reflected light L1 from other parts of the document.

[0006]

[Objective] The present invention has been made in view of the above-mentioned circumstances, and provides an image illuminating device, an image reading device, and an image collecting device that can obtain high illumination efficiency without producing shadows while retaining the advantages of a single-sided illumination light source. This was done for the purpose of providing an optical element.

[0007]

[Structure] In order to achieve the above objects, the present invention provides (1)
an in-line flat condensing element provided on one side of the imaging light beam in front of the image reading position; an off-axis flat condensing element provided on the other side of the imaging light beam in front of the image reading position; It consists of a transparent substrate on which the in-line type flat light condensing element and the off-axis type flat light condensing element are integrally formed, and an illumination light source disposed on the side of the in-line type flat light condensing element. The reading section is illuminated from both sides, and (2) in (1) above,
The in-line planar condensing element is a unidirectional condensing Fresnel lens, and the off-axis planar condensing element is a unidirectional condensing Hololens plate, or
(3) A light source for illuminating the document surface, a member for holding the document, an imaging element, and the imaging element spatially transmits information on the document, and the image-formed document surface information is transferred to a photoelectric conversion element. In an image reading device comprising a sensor that reads the intensity of light as an electric output by a sensor and a housing member for integrally holding these, the image illumination device according to claim 1 is used; ) The image illumination device of (1) above is applied to a reduction type scanner; (5) the above (1)
), the movable image illumination device according to claim 1 is disposed below the document support glass in the movable illumination system of the document fixed type reduction scanner; The optical element is integrally formed by duplication using a photopolymer method, or (7) the flat light condensing element in (1) is formed by an injection method.
Alternatively, (8) the flat light condensing element of (1) above is configured by a volume grating element. Hereinafter, the present invention will be explained based on examples.

FIG. 1 is a configuration diagram for explaining an embodiment of an image illumination device according to the present invention. In the figure, 1 is a document support glass, 2 is an illumination light source (LED array), and 3 is a reading position. , 4 is an effective light beam, and 5 is a hololens plate. A grating element having a cylindrical lens effect is provided on the back surface of the document support glass 1. Reading position 3
There is an in-line grating lens on the left side A, and an off-axis grating lens on the right side B.
There is an off-axis grating lens. This lens is made, for example, as a holographic element. FIGS. 2(a) and 2(b) are enlarged views of the Hololens plate, with FIG. 2(a) being a side view and FIG. 2(b) being a top view. Sections A and B in FIG. 1 are integrally formed with an optical information extraction section provided in the middle thereof. Alternatively, each may be formed independently and only both and portion B may be used. By doing so, the illumination state is the same as when the position to be read is illuminated on both sides even though it is illuminated on one side, and no shadow is produced even when there is a difference in level on the document. Also,
The luminous flux from the LED having a wide emission angle efficiently illuminates the reading position due to the condensing effect of the Hololens plate, and it is possible to obtain a brighter illuminance on the document surface than when both sides are illuminated. Further, the reflected lights L1 and L2 generated by the illumination system shown in the example of FIG. 14 are removed by the hololens plate.

As shown in FIG. 3, an example of the structure and production of such a Hololens plate is as shown in FIG.
A relief hologram can be created by a replication method using a V-curable resin. By doing so, the diffraction efficiency of the off-axis type hololens plate can be maintained at 70% or more even for non-polarized LEDs. FIG. 5 shows an example of a similar Hololens plate molded by the injection method, in which the substrate and the grating part are integrally made of the same plastic material. FIG. 4 shows an example in which a volume grating element is formed on a substrate. Examples of configurations in which these Hololens plates are applied to the same-magnification scanner units shown in FIGS. 10 and 11 are shown in FIGS. 6 and 7, respectively.

In FIGS. 6 and 7, 6 is a housing, 7 is an equal-magnification line sensor, 8 is an imaging element (gradient index rod lens array), 9 is a half mirror lens array, and 10 is a reflective mirror. Other parts having the same functions as those in FIG. 1 are designated by the same reference numerals. A document support glass 1 for a document conveyed by a presser roller rotating in the direction of the arrow, an illumination light source 2, an imaging element 8, and a 1-size line sensor 7 for obtaining information on the document surface as an electrical output based on the intensity of light are arranged. ing. As a result, the information on the document surface is transferred to the illumination light source 2.
The image forming element 8 spatially transmits information on the density of light, and the same-magnification line sensor 7 reads the information as an electrical output. Here, as the imaging optical system, a 1-magnification imaging element such as a rod lens array or a roof mirror lens array is used. As the photoelectric conversion element, a line sensor such as a charge coupled device (CCD) is used. Further, as a light source for illumination, a light emitting diode (LED) array light source, a fluorescent lamp, a xenon tube, or the like is used.

The image illumination device according to the present invention can be applied not only to a 1-magnification scanner but also to a scanner using a charge-coupled device (CCD) or the like. FIG. 8 is a block diagram of an illumination system in which a hololens plate is applied to the reduction type scanner shown in FIG. 12, and FIG. 9 is a block diagram of an illumination system applied to the scanner in FIG. 13. In this case, since the illumination system moves, a movable holo-lens plate is provided below the document support glass.

0012

[Effects] As is clear from the above description, the present invention has the following effects. (1) At the same time, the luminous flux from the light source placed on one side is condensed for illumination, and at the same time the luminous flux diverging to the opposite side of the line to be read, which was not used in the past, is converted to the direction of the optical path and used as condensed illumination light. By using a single-sided illumination light source, the amount of illumination light can be ensured greater than that achieved by double-sided illumination. In addition, the shadow of the document is removed by illumination from opposing directions simultaneously with both side illumination. Also, in terms of space and cost, it is the same as single-sided lighting. Furthermore, flare light, backlighting, etc. can be reduced. (2) Replication using a stamper provides stability, low cost, and excellent mass productivity. It is possible to achieve high diffraction efficiency. (3) The injection method is superior in cost reduction and mass production. (4) The volume type (internal refractive index distribution control) configuration further ensures ease of handling and reliability.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram for explaining an embodiment of an image illumination device according to the present invention.

FIG. 2 is an enlarged view of the Hololens plate.

FIG. 3 is a diagram showing an example of creating a hololens plate.

FIG. 4 is a diagram showing another example of creating a hololens plate.

FIG. 5 is a diagram showing still another example of creating a hololens plate.

FIG. 6 is a diagram showing an example in which a Hololens plate is applied to a 1-magnification scanner unit.

FIG. 7 is a diagram showing another example in which the Hololens plate is applied to a 1-magnification scanner unit.

FIG. 8 is a diagram showing an example in which a hololens plate is applied to a reduction type scanner.

FIG. 9 is a diagram showing another example in which a hololens plate is applied to a reduction type scanner.

FIG. 10 is a diagram showing an example of a conventional same-size scanner unit.

FIG. 11 is a diagram showing another example of a conventional same-size scanner unit.

FIG. 12 is a diagram showing a conventional example of a fixed CCD scanner.

FIG. 13 is a diagram showing a conventional example of a fixed original mirror scanning type CCD scanner.

FIG. 14 is a configuration diagram of a conventional image illumination device.

[Explanation of symbols]

1... Document support glass, 2... Light source for illumination (LED array)
, 3...Position to be read, 4...Effective light flux, 5...Hololens plate.

Claims (5)

[Claims] 1. An in-line type flat condensing element provided on one side of the imaging light beam in front of the image reading position, and an off-axis flat type condenser provided on the other side of the imaging light beam in the front part of the image reading position. a light condensing element, a transparent substrate integrally formed with the in-line flat condensing element and the off-axis flat condensing element, and an illumination light source disposed on the side of the in-line flat condensing element. What is claimed is: 1. An image illumination device comprising: an image illumination device which illuminates a portion to be read from both sides. 2. The in-line planar light condensing element is a one-way condensing Fresnel lens, and the off-axis planar condensing element is a one-way condensing Hololens plate. Item 1. Image illumination device according to item 1. 3. A light source for illuminating the document surface, a member for holding the document, an imaging element, and information on the document is spatially transmitted by the imaging element, and the information on the imaged document surface is transmitted to a photoelectronic device. An image reading device comprising a sensor that reads the intensity of light as an electrical output using a conversion element, and a housing member for integrally holding these, characterized in that the image illumination device according to claim 1 is used. Image reading device. 4. An image reading apparatus characterized in that the movable image illumination device according to claim 1 is disposed below a document support glass in a movable illumination system of a fixed document type reduction scanner. 5. A light condensing element, characterized in that the flat light condensing element according to claim 1 is integrally formed by duplication using a photopolymer method.