JP2002064676A - Line illuminating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a line illuminating apparatus for preventing re-scatter/ reflecting light returned again from scattering and reflection of the draft face. SOLUTION: In a line illuminating apparatus, two line lighting units 10L and 10R are provided opposite for irradiating the same area on the draft with each illumination light (outgoing beam). A paint film (T) for controlling the scattering and reflection of light is provided on an outer face of a light guiding body case 4 for storing a light guiding body 3. The paint film (T) is formed to paint an outer face of the light guiding body case 4 in a black matted color, for instance. The outer face of the light guiding body case 4 may be covered with a member (for instance, black case, etc.), for controlling the scattering and reflection of light.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line illuminator used for a contact type image sensor (CIS), and more particularly, to a line illuminator in which two line illuminating units using a light guide are arranged to face each other. .

[0002]

2. Description of the Related Art A contact image sensor is used as a device for reading a document by a facsimile, a copying machine, a scanner, or the like. This contact image sensor
A line illuminating device is provided for illuminating the document surface with a line over the main scanning range. As this line illumination device, a device using a light guide is known.

The present applicant uses two line illumination units each using a light guide and arranges the line illumination units to face each other (to face each other), thereby achieving a uniform light amount distribution in the main scanning direction. Also, there has been proposed a facing line illumination device in which a shadow is hardly generated even when a document has a fold or the like.

FIG. 5 is a perspective view of the above-mentioned opposed line illumination device, and FIG. 6 is a sectional view in the sub-scanning direction of a contact type image sensor (image reading device) provided with the above opposed line illumination device. In FIG. 5, X is the main scanning direction, Y is the sub-scanning direction, and Z is the direction perpendicular to the document surface.

[0005] As shown in FIG. 5, a facing type line lighting device 110 has two sets of line lighting units 110L and 110L.
R are arranged to face each other so that each illumination light irradiates the same area of the document reading surface. Each of the line lighting units 110L and 110R includes, for example, an acrylic light guide 3 in a white light guide case 4, and has an LED (light emitting diode) on an end face of the light guide 3 in the longitudinal direction (main scanning direction). The light-emitting source substrate 11 having the light-emitting source 12 is mounted. Reference numeral 11a is a terminal for supplying power to a light emitting source 12 such as an LED (light emitting diode).

Light incident from the end face of the light guide 3 and emitted from the light emitting source 12 is guided in the longitudinal direction (main scanning direction) of the light guide 3 while being reflected on the inner surface of the light guide 3, and at the same time. 3 is scattered by the light scattering pattern P formed along the longitudinal direction. As shown in FIG. 6, the scattered light is reflected by the reflection curved surface (elliptical surface) 3c of the light guide 3 and exits from the exit surface 3a. The light scattering pattern P is formed, for example, by printing a white paint. As the distance from the light source 12 increases, the intensity of light propagating inside the light guide 3 decreases. Therefore, by increasing the area of the light scattering pattern P as the distance from the light emitting source 12 increases, the intensity of the emitted light becomes uniform over the longitudinal direction (main scanning direction) of the light guide 3. Also, by covering the light guide 3 with the light guide case 4 except for the light exit surface 3a of the light guide 3, light leaking to the outside is reflected on the inner surface of the light guide case 4 and the light inside the light guide 3 This reduces the loss of scattered light and improves the intensity of emitted light.

As shown in FIG. 6, a contact type image sensor (image reading apparatus) 101 includes a housing 2.
Each of the line illuminating units 110L and 110R is incorporated in the sensor 2, a lens array 5 is arranged in the housing 2 as a 1 × image forming lens, and a line image sensor (light source conversion element) 6 is provided below the housing 2. The substrate 7 is attached. This contact type image sensor (image reading device)
Reference numeral 101 denotes a line image sensor (light source conversion element) that causes each illumination light emitted from the emission surface 3a of each light guide 3 to enter the reading surface of the original through the cover glass 8 and passes through the lens array 5 to the reflected light. The document is read by detecting at 6.

The light guide 3 has an approximately 1/4 elliptical cross section in a direction orthogonal to the length direction, and a side surface along the length direction has an emission surface 3a parallel to the minor axis direction of the ellipse. It has a surface 3b parallel to the major axis direction of the ellipse and a reflection curved surface (elliptical curved surface) 3c. On a surface 3b parallel to the major axis direction of the ellipse, a light scattering pattern P is formed at a position near the focal point of the ellipse by printing a white paint or the like. By providing the light scattering pattern P near the focal point of the ellipse, the light scattered by the light scattering pattern P is reflected by the reflection curved surface (elliptical curved surface) 3c and condensed on the document reading surface. Light intensity can be improved.

[0009]

FIG. 7 is a view showing a problem of a contact type image sensor (image reading apparatus) 101 provided with the above-mentioned opposed line illumination device 110, in which only one of the line illumination units 110L is turned on. Is shown. If there is a document on the glass surface of the cover glass 8, new scattered / reflected light K1 is generated from the document surface irradiated with the illumination light of the line illumination unit 110L, and the scattered / reflected light from this document surface is generated.
The reflected light K1 illuminates the upper surface of the other line illumination unit 110R. Since the light guide case 4 is formed of a white material having high scattering and reflectance, the upper surface of the light guide case 4 becomes a new light source K2 and illuminates the document surface. For this reason, the rod lens 5 depends on the presence or absence of the original.
The light intensity on the optical axis changes.

FIG. 8 is a graph of light intensity characteristics when there is no original, and FIG. 9 is a graph of light intensity characteristics when there is a white original. In these graphs, the vertical axis represents light intensity,
The horizontal axis indicates displacement in the sub-scanning direction. A displacement of 0 in the sub-scanning direction is the optical axis position of the rod lens 5, and one line illumination unit 110L side is indicated by a negative value, and the other line illumination unit 110R side is indicated by a positive value.

The black circles indicate on the glass surface of the cover glass 8 (Z
= 0.0 mm), square marks indicate the light intensity characteristics at a position 0.5 mm above the glass surface (Z = 0.5 mm), and triangle marks indicate the light intensity characteristics above the glass surface. 0mm
Regarding the light intensity characteristics at a position distant (Z = 1.0 mm), a mark “x” indicates a position 1.5 mm away from the glass surface (Z = 1.
5 mm). Note that the light intensity characteristics shown in FIG. 9 are obtained when the white original is brought into close contact with the glass surface of the cover glass 8 (Z = 0.0 mm), and the white original is placed 0.5, 1.0 from the glass surface. , 1.5 mm floating. From these graphs, it can be seen that the light intensity changes depending on the presence or absence of the white document.

FIG. 10 is a diagram showing output signals when an original having a black rectangular area is read. FIG. 10A shows a read original, and FIG. 10B shows an output signal. When a document having a black rectangular area is scanned in the direction of the arrow shown in the figure,
An ideal output signal has a white level W as shown by a symbol SR.
From the black level B to the black level B and from the black level B to the white level W are steep. On the other hand, as shown in FIG. 7, the light K1 scattered and reflected by the white portion of the document is reflected by the upper surface of the light guide case 4, and the light K2 reflected by the light guide case 4 is reflected by the document. The reading output signal SJ of the original in a state where the surface is illuminated has a gradual change from the white level W 'to the black level B' and a change from the black level B 'to the white level W'. As a result, the read image blurs in a black rectangular area. This blurring of the read image occurs in both the main scanning direction and the sub-scanning direction. Further, since the upper surface of the light guide case 4 is a new light source, the light intensity on the document surface increases. For this reason, the white level W ′ and the black level of the output signal SJ are higher than the ideal white level W and the black level B of the output signal SR.

As described above, a contact type image sensor (image reading device) provided with the conventional opposed line illumination device 110
In 101, light scattered and reflected by the original is transmitted through the light guide case 4.
In order to irradiate the original surface by scattering and reflecting again, the amount of light is scattered and reflected on the original surface depending on the size of the original and the positional relationship between the white area and the black area of the original surface, and the amount of light changes. Since the amount of light that is scattered and reflected again by the light guide case 4 and irradiates the original surface changes, the light intensity distribution of the illumination light in the original reading area becomes uneven. For this reason, the luminance of the document cannot be accurately read, and the read image may be unclear.

The present invention has been made to solve such a problem, and prevents light scattered / reflected on a document surface from being further reflected on a light guide case and irradiating the document surface again,
An object of the present invention is to provide a line illumination device that enables a document to be clearly read.

[0015]

According to a first aspect of the present invention, there is provided a line illuminating device including a coating film for suppressing light scattering and reflection on at least a part of an outer surface of a light guide case. Characterized by having been subjected to the above processing. The line illuminating device according to claim 2 is characterized in that at least a part of the light guide case is covered with a member that suppresses scattering and reflection of light.

At least a portion of the outer surface of the light guide case is provided with a coating film for suppressing light scattering and reflection, or is covered with a member for suppressing light scattering and reflection, so that scattering from the document surface is prevented. The reflected light can be prevented from being scattered and reflected again by the light guide case. Thus, the light scattered and reflected by the light guide case does not irradiate the document surface. Therefore, the original intensity distribution of the illumination light is not disturbed by the scattered / reflected light from the light guide case, and the image can be read clearly.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view of a contact type image sensor to which the line illumination device according to claim 1 is applied.

The contact type image sensor (image reading apparatus) 1 shown in FIG. 1 has a housing 2 in which each of the line illumination units 10L and 10R are incorporated. A lens array 5 is arranged, and a sensor substrate 7 provided with a line image sensor (light source conversion element) 6 is attached to a lower portion of the housing 2. A line illuminating device is constituted by two sets of line illuminating units 10 </ b> L and 10 </ b> R opposed to each other. Be composed.

The contact type image sensor (image reading device) 1 causes each illumination light emitted from the emission surface 3a of each light guide 3 to enter a reading surface of an original through a cover glass 8, and reflects the reflected light to a lens. The original is read by detection by a line image sensor (light source conversion element) 6 via the array 5.

Each of the line lighting units 10L and 10R is
The point that a coating film T that suppresses scattering and reflection of light is provided on the outer surface of the light guide case 4 is the conventional line lighting unit 110.
L, 110R. The coating film T is a light guide case 4
Is painted with a matte black color. Since the scattered / reflected light from the document surface is absorbed by the coating film T, the light guide case 4 can be prevented from becoming a new light source. Thus, the original intensity distribution of the illumination light is not disturbed by the scattered / reflected light from the light guide case 4, and the image can be read clearly.

FIG. 2 is a sectional view of a contact type image sensor to which another line illumination device according to claim 1 is applied. FIG.
Each of the line lighting units 20L and 20R shown in FIG. 1 has a coating film t formed only on the upper end surface of the light guide case 4. Simply coating only the upper end surface, which is substantially parallel to the document reading surface, with a black matte color can effectively prevent the light guide case 4 from becoming a new light source, thereby providing the original illumination light. The intensity distribution is not disturbed by the scattered / reflected light from the light guide case 4, and the image can be read clearly.

FIG. 3 is a sectional view of a contact type image sensor to which the line illumination device according to claim 2 is applied. Each of the line lighting units 30L and 30R shown in FIG. 3 has the outer surface of the light guide case 4 covered with a black cover 31.

FIG. 4 is a sectional view of a contact type image sensor to which another line illumination device according to claim 2 is applied. FIG.
Each of the line illumination units 40L and 40R shown in FIG. 3 has the upper part of the light guide case 4 covered with a black cover 41 having an L-shaped cross section, for example.

As shown in FIGS. 3 and 4, the light guide case 4 is covered with a member such as a black cover 31, 41 which suppresses the scattering and reflection of light, so that the light guide case 4 becomes a new light source. Can be effectively prevented, whereby the original intensity distribution of the illumination light is not disturbed by the scattered / reflected light from the light guide case 4 and the image can be read clearly.

[0025]

As described above, the line illuminating device according to the present invention is provided with a coating for suppressing light scattering / reflection on the outer surface of the light guide case, or by providing a light guide case with light scattering. -Since it is covered with the member that suppresses reflection, it is possible to prevent the scattered / reflected light from the document surface from being scattered / reflected again by the light guide case. Thus, the light scattered and reflected by the light guide case does not irradiate the document surface. Therefore,
The original intensity distribution of the illumination light is not disturbed, and the image can be read clearly.

[Brief description of the drawings]

FIG. 1 is a sectional view of a contact type image sensor to which a line illumination device according to claim 1 is applied.

FIG. 2 is a sectional view of a contact type image sensor to which another line lighting device according to claim 1 is applied.

FIG. 3 is a sectional view of a contact type image sensor to which the line lighting device according to claim 2 is applied.

FIG. 4 is a cross-sectional view of a contact type image sensor to which another line lighting device according to claim 2 is applied.

FIG. 5 is a perspective view of a conventional opposed line lighting device.

FIG. 6 is a cross-sectional view of a contact type image sensor including a conventional opposed line illumination device.

FIG. 7 is a diagram showing a problem of a conventional opposed line lighting device.

FIG. 8 is a graph of a light intensity characteristic of a conventional opposed-type line illumination device in a state where no original is present.

FIG. 9 is a graph of light intensity characteristics in a state where a white document is present in a conventional opposed line illumination device.

FIG. 10 is a diagram showing an output signal when a document having a black rectangular area is read by a contact image sensor having a conventional opposed line illumination device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Contact image sensor (image reading device), 2 ... Housing, 3 ... Light guide, 3a ... Emission surface, 3c ... Reflection curved surface, 4 ...
Light guide case, 5: lens array, 6: line image sensor (photoelectric conversion element), 11: light emitting source substrate, 12: light emitting source (LED), 10L, 10R, 20L, 20R, 3
0L, 30R, 40L, 40R: line illumination units constituting a line illumination device; 31, 41: members for suppressing light scattering / reflection (black cover); T, t: coating films for suppressing light scattering / reflection (Black matte coating film), P: Light scattering pattern.

Claims (2)

[Claims] 1. A line illuminating device including a light guide for guiding light from a light source incident from an end face in a longitudinal direction and scattering light by a light scattering pattern formed along the longitudinal direction to emit the light from an exit surface. In this line illuminating device, two sets of line illuminating units each containing the light guide in a case are provided, and each line illuminating unit is configured such that light emitted from each emission surface of each light guide is the same as the original reading surface. A line illuminating device arranged to irradiate an area, wherein at least a part of an outer surface of the light guide case is subjected to a process of suppressing scattering and reflection of light. 2. A line illuminating device comprising a light guide for guiding light from a light source incident from an end face in a longitudinal direction and scattering light by a light scattering pattern formed along the longitudinal direction to emit the light from an exit surface. In this line illuminating device, two sets of line illuminating units each having a light guide housed in a case are provided, and each line illuminating unit emits light emitted from each emission surface of each light guide in the same area of the document reading surface. Wherein the light guide case is covered with a member that suppresses scattering and reflection of light.