JPH0785238A - Original illuminator for picture reader - Google Patents

Abstract

PURPOSE:To effectively utilize light projected from a linear light source device for illuminating the surface of an original by arranging the linear light source device so that the optical axis of light emitted from the device is almost parallel with the surface of the original and providing the device with a reflection face for deflecting the optical axis of the emitted light to the original face side. CONSTITUTION:The linear light source device 14 consists of a transparent rod 10 and plural LED elements 41. The rod 10 is arranged in a frame 49 so as to be almost loaded on the inside face of a cover glass 21. Thereby the optical axis 18 of illuminating light 16 projected from the projection face 10c of the rod 10 is made almost parallel with the cover glass 21, in its turn the face 17 of an original. The frame 49 is provided with a reflection face 31 for reflecting the light 16 so that the optical axis 18 of the light 16 is deflected to the side of the original face 17. Thereby the light 16 projected from the projection face 10c is reflected on the reflection face 31 and directed to the original face 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document illuminating device for linearly illuminating a document surface in an image reading device such as a contact type image sensor used in a facsimile, a copying machine, a hand scanner and the like. is there.

[0002]

2. Description of the Related Art In facsimiles, copiers, hand scanners and the like, an image scanning device such as an image sensor, that is, an image reading device is used to read a document. There are various types of image reading devices such as a reduction type, a contact type, and a perfect contact type. In the case of a contact type image sensor, the image reading device includes an illumination system, a 1 × imaging optical system, a sensor, and the like. . In addition, such a contact image sensor generally does not require a high-performance lens for document reduction, which is required in the case of a reduction image sensor.
The optical path length can be shortened, and therefore, downsizing and cost reduction can be achieved.

In such a contact type image sensor, the illumination system must illuminate the document surface with an illuminance higher than that which can be read by the sensor. The area to be illuminated by this illumination system is linear and extremely narrow in the sub-scanning direction, and in the main scanning direction (hereinafter referred to as "length direction") orthogonal to the sub-scanning direction. It's getting quite long. Further, if the illuminance on the document surface is uneven in the length direction, it causes a reading error. Therefore, it is desirable that the illuminance is uniform.

As such an illumination system, a linear light source device 40 as shown in FIGS. 1 and 2 is conventionally used in a one-dimensional image reading device such as a contact image sensor as shown in FIG. Incorporated and used. As shown in FIG. 1, the linear light source device 40 is an LED array having an elongated shape along the length direction, and is made of an epoxy resin,
Dozens (for example, 32) LED elements (that is, LED chips) 41 for illumination and a resistor 42 on a printed wiring board 43 based on a synthetic resin such as phenol resin.
Are mounted by using wire bonding 46 and the like, and each LED chip 41 is covered with a transparent synthetic resin 44 such as an epoxy resin.

FIG. 2 shows a connection state of the LED chip 41 and the resistor 42 in the LED array 40 shown in FIG. In FIG. 2, eight sets of series circuits 47 each including one resistor 42 connected in series to four LED chips 41 connected in series are provided, and these eight sets of series circuits 47 are parallel to each other. It is connected to the. Therefore, in the entire LED array 40, 32
Although one LED chip 41 is used, all the LED chips 41 are arranged in a line on the printed wiring board 43, as shown in FIG.

In FIG. 2, the LED chip 4 is generally used.
Since the forward voltage (VF) applied to 1 is about 2.0 to 2.5V, assuming that the forward voltage (VF) when the forward current (IF) is 20 mA is VF = 2.2V, the resistance of the resistor 42 used. The value R is R = 160 (Ω) (= (12-2.2 × 4) /
0.02). However, since the VF and the brightness of the mass-produced LED chips vary, the series circuit 4
By adjusting the resistance value R of the resistor 42 in FIG. 7, the adverse effect due to such variations is suppressed.

When such a linear light source device 40 is incorporated in a contact type image sensor 48 as shown in FIG.
The light emitted from the LED chip 41 passes through the cover glass 21 that also serves as the platen glass, and the document surface 17 to be illuminated.
Incident on the original document surface 17, reflected on the original surface 17 and then passed through the cover glass 21 again, such as a SELFOC (registered trademark) lens array (hereinafter referred to as “SLA” (registered trademark)) supported by the metal frame 49. The light enters the rod lens array 19, and as a result, an image of the document surface 17 is formed by the SLA 19 on the photoelectric conversion element 36 provided on the lid 34.

In the contact image sensor 48 shown in FIG. 3, the SLA 19 is specifically a product number SLA20B manufactured by Nippon Sheet Glass Co., Ltd.
Has an element diameter of 0.9 mm, a height of 6.8 mm, and a conjugate length of 14.
It is 4 mm. Further, the LED array 40 is adhesively fixed to the metal frame 49 with a double-sided adhesive tape. Further, the cross-sectional size of the contact image sensor 48 is, for example, L ₁ = L ₂ = 20 mm.

In the contact image sensor 48 shown in FIG. 3, the optical axis 18 of the light emitted from the LED chip 41 in the LED array 40 is about 45 ° with respect to the document surface 17.
The LED array 40 is attached to the metal frame 49 so that the reason is as follows.

That is, in order to increase the illuminance of the document surface 17, the LED chip 41 is arranged at the position where the SLA 19 is arranged in FIG. 3 so that the optical axis 18 is substantially perpendicular to the document surface 17. Preferably. But,
As described above, in the contact image sensor 48, since the cover glass 21 is interposed between the LED array 40 and the SLA 19 and the document surface 17, stray light (flare) reflected by the inner side surface 21a of the cover glass 21 is generated. SLA19
And enters the photoelectric conversion element 36 to give noise.

In order to measure the intensity of this noise, instead of the cover glass 21, a cover glass having a variable angle θ _C (see FIG. 3) with the optical axis 22 of the SLA 19 (see FIG. 3) is used. The output voltage E of the photoelectric conversion element 36 was measured using the same device as the contact image sensor shown in FIG. In FIG. 4, the angle θ
The change of the output voltage E according to the change of _C is shown. In FIG. 4, the output voltage E is almost 0 and 10 mV (1/100 when reading a white original) or less at 90 ° or less and 130 ° or more, but 105 ° to 115 °.
It is high in the range of ° and has a peak near θ _C = 111 °. Since the peak value is about twice as high as the normal output voltage of the photoelectric conversion element 36 at the time of reading a white original, such strong reflected light enters the angle of view AV of the SLA 19 and the SLA 19 is connected. If the image is affected, the output of the photoelectric conversion element 36 will be greatly adversely affected.

In order to avoid such an adverse effect, FIG.
In the contact image sensor 48 shown in FIG.
The LED so that it is about 45 ° to the document surface 17.
An array 40 is arranged. Since this 45 ° corresponds to the case of θ _C = 90 ° in FIG. 4, in such a setting, stray light (flare) generated by reflection on the inner surface 21a of the cover glass 21 is photoelectric. The influence on the output voltage E of the conversion element 36 is almost zero.

The linear light source device (L
In the case of the ED array) 40, the circuit configuration is simple, the response time at lighting and extinguishing is short, the cost is low, and a large number of LED chips 41 are arranged, so that a sufficient amount of light is secured. You can

However, in the case of this LED array 40, by adjusting the resistance value R of the resistor 42, even if the adverse effects due to variations in VF and brightness of each LED chip 41 are suppressed, the LEDs on the document surface 17 The portion facing the chip 41 becomes bright, and the portion facing the intermediate position between the LED chip and the LED chip adjacent thereto becomes dark, so that periodic illuminance unevenness occurs, and particularly large illuminance unevenness is read. It is a serious problem that causes an error.

The above-mentioned illuminance unevenness in the contact image sensor 48 shown in FIG. 3 will be specifically described. In this contact image sensor 48, a sensor of a light intensity meter is placed at the position of the document surface 17, and this sensor is long. By measuring the illuminance at each position while moving in the vertical direction, the graph shown in FIG. 5 was obtained. Maximum value MA of illuminance in the effective measurement range ER excluding the left and right ends of this graph
The illuminance unevenness was calculated by the following equation using X and the minimum value MIN. Illuminance unevenness = (MAX-MIN) / (MAX + MIN)

According to the calculation result, the illuminance unevenness in the case shown in FIG. 5 is 14.2%, which shows that there is a considerably large illuminance unevenness.

In order to make the above-mentioned illuminance unevenness inconspicuous, it is necessary to make the interval between the LED chips 41 small. Therefore, for example, in the case of an A4 size document having a width of 216 mm, there are about 30 LED chips. is necessary. As a result, the power consumption increases, and the temperature rise of the LED chip 41 increases. Furthermore, in order to make the above-mentioned illuminance unevenness inconspicuous, the LED chip 41 and the document surface 17
Since it is necessary to set the interval between and to a certain extent, there is a certain limit to downsizing the contact image sensor as a whole.

In order to solve the above-mentioned problems of the linear light source device 40 shown in FIGS. 1 to 3, such a linear light source device (LED array) 40 is replaced by the linear light source device shown in FIG. It is considered that 13 is used for the contact type image sensor 48 as shown in FIG.

In the linear light source device 13 shown in FIG. 6, an LED lamp (that is, a chip-type LED) is provided so as to face both end surfaces 10a and 10b of a transparent rod 10 having a rectangular parallelepiped shape that is elongated along the length direction. ) 12 are arranged. A light-scattering surface 11 composed of a sand scraping surface, a white printing surface, or the like is formed on one long and slender surface of the outer circumference of the transparent rod 10. The chip-type LED 12 is a one-package one-element type having a structure in which LED elements are arranged on a printed wiring board having a synthetic resin base and the LED elements are covered with a flat lens type transparent resin package. Is. Further, the chip type LED 12 is the chip type L
The anode electrode and the cathode electrode are soldered to the wiring patterns of a printed wiring board (not shown) having a synthetic resin base for mounting the ED 12 and other electric parts, and thus the printed wiring board is mounted. Further, when the linear light source device 13 shown in FIG. 6 is incorporated into the contact image sensor 48 shown in FIG. 3, the contact image sensor 48 shown in FIG. 3 has been described with reference to FIG. For the same reason as described above, the linear light source device 13 is mounted on the metal frame 49 so that the optical axis 18 of the light emitted from the light diffusing surface 11, which is a pseudo light source, is approximately 45 ° with respect to the document surface 17. It is attached.

Therefore, in FIG. 6, the chip type LE is
The light emitted from D12 enters the inside of this transparent rod 10 from one end surface 10a or 10b of the transparent rod 10, and repeats total reflection on the outer peripheral surface of the transparent rod 10 to the other end surface 10a or 10b. Since the light is diffused and diffused by the light diffusing surface 11 while facing, the light is emitted to the outside from the surface 10c opposite to the light diffusing surface 11. The light emitted to the outside illuminates the document surface 17 as in the case shown in FIG. 3, so that an image of the document surface 17 is formed on the photoelectric conversion element 36. The transparent rod 1
The light emitted from the 0 surface 10c to the outside has substantially uniform brightness in the length direction.

In the case of the linear light source device 13 shown in FIG.
Compared with the case of the LED array 40 shown in FIGS.
The number of ED chips (LED elements) can be reduced, and the illumination light emitted from the transparent rod 10 toward the document surface 17 is uniform in the length direction. Even if they are brought close to each other, uneven illuminance does not occur. Therefore, it is possible to achieve downsizing and cost reduction of the contact image sensor.

However, in the case of the linear light source device 13 shown in FIG. 6, since only one chip type LED 12 is arranged so as to face both end surfaces 10a and 10b of the transparent rod 10, respectively. The amount of light obtained from the linear light source device 13 may not always be sufficient.

Therefore, the present inventors have replaced the linear light source device 13 shown in FIG. 6 with the linear light source device 14 shown in FIGS. 7, 8 and 9 and the contact type image sensor 4 as shown in FIG.
It was conceived that the contact image sensor 50 shown in FIG. 7 to 10, the same parts as those in FIGS. 1 to 6 are designated by the same reference numerals and the description thereof will be omitted.

Next, the contact type image sensor 50 shown in FIGS. 7 to 10 will be described as a reference example. As shown in FIGS. 7 and 8, the linear light source device 14 has a flat and elongated rectangular parallelepiped shape. With a transparent rod 10 and a pair of one-package four-element type LED array (LED lamp) 2
It consists of 4 and.

As shown in FIG. 7, each LED array 24 includes four LED chips (LEs) connected in series with each other.
The D element) 41 is directly connected to the conductor wiring pattern 51 on the metal base wiring board 26 using the wire bonding 46 or the like. The metal base wiring board 51 is formed by sequentially laminating a substantially L-shaped metal base 52 made of stainless steel, an insulating paste layer 53, a conductor wiring pattern 51, and a solder resist layer 54. In addition, the LED chip 41 is provided in the connection portion 55 formed of a portion of the conductor wiring pattern 51 which is not covered with the solder resist layer 54.
The lower surface electrode of the LED chip 41 is soldered.
The upper surface electrode of is connected to another connection portion 55 by wire bonding 46. And with these connections,
The four LED chips 41 are connected in series with each other. Further, a substantially rectangular annular frame 28 made of a substantially opaque synthetic resin such as white is attached on the metal base wiring board 26 by adhesion or the like so as to take in the entire four LED chips 41. . Further, since the hollow layer 28a of the annular frame 28 is filled with the translucent synthetic resin to form the filling layer 29, the four LED chips 41 are resin-packaged by the filling layer. . In FIG. 7, A and C are L
The anode electrode and the cathode electrode of the ED array 24, each of which is composed of a part of the conductor wiring pattern 51.

The transparent rod 10, as shown in FIG.
Corresponding to the LED array 24 having the individual LED chips 41, having a flat and long rectangular parallelepiped shape, acrylic resin,
It is made of polycarbonate resin, optical glass, etc. Then, on one side surface of the outer periphery of the transparent rod 21, a white coating layer 11 for making this one side a light diffusion surface is formed.
Is formed, and the surface 10c opposite to the white coating layer 11 is formed.
A reflective layer 23 made of metal plating or metal foil having a high reflectance is formed on the remaining three side surfaces except for.
The reflective layer 23 is for effectively totally reflecting the light incident on the inside of the transparent rod 10 from the LED array 24 on the outer peripheral surface of the transparent rod 10.

In order to mechanically connect the LED array 24 to the transparent rod 10, both end surfaces 10 of the transparent rod 10 are connected.
A pair of protrusions 10d is integrally formed on each of a and 10b, and a pair of left and right fitting holes 28b is formed on the annular frame 28 of the LED array 24. Then, the pair of protrusions 10d are inserted into the pair of fitting holes 28b.
The LED array 24 is attached to the one end face 10 a of the transparent rod 10 by fitting the. Although only one of the LED arrays 24 is shown in FIG. 7, another LED array 24 having a structure symmetrical to the one LED array 24 also has a transparent rod as shown in FIG. It is attached to the other end surface 10b of 10 in the same manner.
In this case, if the upper surfaces of the pair of LED arrays 24 are brought into close contact with both end surfaces 10a and 10b of the transparent rod 10, LE
The light emitted from the D chip 41 can be efficiently incident on the inside of the transparent rod 10 with almost no leakage to the outside. In addition, the transparent rod 1 is provided on the upper surface of the LED array 24.
It is also possible to bond both end faces 10a, 10b of 0 with a transparent epoxy resin-based adhesive. In this case, although the amount of light leaking to the outside increases a little, the LED array 24 is replaced by the transparent rod 1.
Can be firmly bonded to 0.

In the LED array 24 shown in FIG. 7,
Since the four LED chips 41 are surrounded by the annular frame 28 made of a substantially opaque synthetic resin such as white, little light leaks from the side of the LED chips 41 to the outside of the LED array 24. Therefore, L
The light emitted from the ED chip 41 efficiently transmits the transparent rod 10
Can be introduced inside. Moreover, since it is possible to directly connect the LED chip 41 to the conductor wiring pattern 51 on the metal base wiring board 26 without using a printed wiring board having a synthetic resin as a base as in the case shown in FIG. The radiation performance can be improved.

FIG. 9 shows a white coating layer 11 forming the light diffusing surface of the transparent rod 10 shown in FIG.
The white coating layer 11 has a pattern in which the width of the white coating portion 11a and the width of the non-coating portion (smooth portion) 11b gradually change according to the position in the longitudinal direction.
The width of the white painted portion 11a gradually increases from both end faces 10a, 10b to the center of the unpainted portion 11b.
The width of is becoming smaller.

FIG. 10 shows a contact type image sensor 50 as a reference example obtained by incorporating the linear light source device 14 shown in FIGS. 7, 8 and 9 into a contact type image sensor as shown in FIG. It is shown. In the case of the contact image sensor 50 shown in FIG. 10, the light diffusion surface 11 which is a pseudo light source is also used for the contact image sensor 48 shown in FIG. 3 for the same reason as described with reference to FIG. The optical axis 18 of the light emitted from the
The linear light source device 14 is attached to the metal frame (the metal frame 49 in the case of FIG. 3) so as to be 5 °.

[0031]

However, in the contact-type image sensor 50 as a reference example shown in FIGS. 7 to 10, the present inventors have studied the outer surface 21 of the cover glass 21.
The illuminance peak at point b is not on the document surface 17 but at point 2
By empirically finding that it is close to 1c, it was found that the illumination light 16 from the linear light source device 14 was not effectively used to illuminate the document surface 17.

According to the present invention, the light emitted from the linear light source device is effectively used for illuminating the surface of an original, and the original is used in an image reading apparatus such as a contact type image sensor which has a good space factor and can be miniaturized. An object is to provide a lighting device.

[0033]

In order to achieve the above object, in the original illuminating device in the image reading apparatus according to the present invention, the optical axis of the light to be emitted is approximately parallel to the original surface. The linear light source device is provided, and a reflecting surface that reflects the light is provided so that the optical axis of the light emitted from the linear light source device is deflected to the document surface side.

The reflecting surface may be an elongated flat surface or an elongated concave surface.

Further, the linear light source device has a long light-transmitting rod and a light source unit arranged near at least one end face of the light-transmitting rod, and is emitted from the light source unit. It is preferable that the light is incident on the translucent rod and then emitted from the outer peripheral surface along the longitudinal direction of the translucent rod.

The light source unit is arranged at least near one of the end faces of the light-transmitting rod and is at least 1.
Individual light emitting elements and a mounting plate to which the light emitting element is mounted, the mounting plate comprising a metal base, an insulating layer formed on the metal base, and a conductor formed on the insulating layer. And a wiring pattern, and the electrode of the light emitting element is preferably connected to the conductor wiring pattern.

Further, the light source unit is housed in an opaque annular frame body disposed on the mounting plate so as to surround the light emitting element mounted on the mounting plate, and in a hollow portion of the annular frame body. It is preferable to further have a translucent material.

[0038]

The light is emitted from the linear light source device so that its optical axis is substantially parallel to the document surface, and this light is deflected at the reflecting surface toward the document surface. Thus, the document surface can be effectively illuminated.

[0039]

EXAMPLE An example of the present invention will be described below with reference to FIGS. 7 to 9 and 11 to 14. In the embodiment of the present invention, the linear light source device 14 shown in FIGS. 7 to 9 having the same configuration as that of the reference example shown in FIGS. 7 to 10 is used. In addition, in FIGS.
The same parts as those in FIG. 10 are designated by the same reference numerals and the description thereof will be omitted.

First, referring to the first embodiment of the present invention shown in FIGS. 7 to 9 and 11 to 13, the contact image sensor 60 shown in FIGS. 11 and 12 has the following two points. It is substantially different from the contact image sensor 50 shown in FIG. 11 is a schematic view of the contact image sensor 60 shown in correspondence with FIG. 10, and FIG. 12 is a view specifically showing the contact image sensor 60 shown in FIG.

First, FIG. 1 of the image sensor 60 of FIG.
The first difference from the image sensor 50 shown in FIG. 0 is that the transparent rod 10 is placed on the inner surface 21a of the cover glass 21 on the metal frame 49 in a state of being almost mounted. Therefore, the optical axis 18 of the illumination light 16 to be emitted to the outside from the emission surface 10c of the transparent rod 10 is substantially parallel to the cover glass 21, and thus the document surface 17.

The second difference is that the exit surface 10c is
The optical axis 18 of the illumination light 16 emitted from the outside is the original surface 1
This is that a long and thin reflecting surface 31 for reflecting the light is provided on the metal frame 49 so as to be deflected to the 7 side. Therefore, the illumination light emitted from the emission surface 10c to the outside is reflected by the reflection surface 31 and goes to the document surface 17, so that the document surface 17 can be efficiently illuminated. The reflection surface 31 may be formed of a plating layer formed by plating a metal such as aluminum or tin having a high reflectance on a flat surface of the metal frame 49 made of aluminum or the like, and similar to the metal frame 49. Alternatively, a metal plate or metal foil having high reflectance may be attached. The optical axis 18 of the illuminating light 16 and, by extension, the angle formed by the cover glass 21 and the reflection surface 31 is, of course, an acute angle, but from a practical viewpoint, it is preferably 40 to 80 °, and 50 More preferably, it is ˜70 °.

The contact type image sensor 60 is specifically shown in FIG. 12, but in this FIG.
As A19, the product number SLA20 of Nippon Sheet Glass Co., Ltd. shown in FIG.
D (element diameter 0.6 mm, height 4.3 mm, conjugate length 9.1 mm) is used. Further, in FIG. 12, a gap 37 between the lower end of the SLA 19 and the facing portion of the metal frame 49 is provided to absorb variations in the dimensions of the SLA 19 in manufacturing.

In the case of the contact image sensor 60 shown in FIG. 12, the cross-sectional dimensions L ₃ and L ₄ are 16.5, respectively.
Since it can be set to mm and 11 mm, the sectional area ratio can be set to about 1/2 of that in the case of the conventional contact type image sensor 48 shown in FIG. 3, and therefore the size can be considerably reduced. The length dimension of the contact image sensor 60 shown in FIG. 12 (length dimension in the direction perpendicular to the paper surface in FIG. 12) can be about 220 to 230 mm, and the length dimension of the metal frame 49 is 216 mm. Can be

FIG. 13 shows the measurement result of the illuminance distribution according to the position of the document surface 17 in the contact image sensor 60 shown in FIG. In this measurement, the dimensions of the transparent rod 10 were 8 mm, 230 mm and 1.5 mm for L ₅ , L ₆ and L ₇ shown in FIG. 8, respectively.
Further, four LED chips 41 each were attached to both end surfaces 10a and 10b of the transparent rod 10 by a transparent epoxy resin adhesive in the same arrangement as that shown in FIG. These LED chips 41 have a peak wavelength of 5
The LED chip 41 of 70 nm was made to emit light by applying a current of 20 mA to each LED chip 41. The cover glass 21 has a thickness of 1.1 mm, and the reflecting surface 31 has a thickness of 0.05 mm.
Using an aluminum foil of mm, the angle θ in FIG. 12 was 60 °.

Under such a condition, the sensor (diameter 1 mm) of the light intensity meter is placed at the position of the document surface 17 in FIG. 12, and the illuminance distribution is measured by moving this sensor along the length direction. , The graph shown in FIG. 13 was obtained. As is clear from FIG. 13, in the case of the contact image sensor 60 shown in FIG. 12, the ripple is much smaller than that in the case shown in FIG. In this case, the aforementioned illuminance unevenness (= (MAX-MIN) / (MAX + MIN))
Is 6.8%, so the illuminance unevenness is considerably improved compared to 14.2% in the case of the conventional contact image sensor 48 shown in FIG. Therefore, in the case of the contact-type image sensor 60 shown in FIG. 12, not only can the cross-sectional dimension be smaller than in the conventional case, but also the illuminance unevenness can be reduced.

In the first embodiment shown in FIGS. 11 and 12, the reflecting surface 31 is a long and thin plane, but as in the second embodiment shown in FIG.
May be a long thin concave surface (long thin semi-cylindrical surface). In this case, since the illumination light 16 can be efficiently condensed on the document surface 17, the utilization efficiency of the illumination light 16 is further enhanced. be able to.

Further, in the above-mentioned embodiment, the transparent rod 10 has a flat and long rectangular parallelepiped shape, but it may have a long and thin cylindrical shape.

The utilization efficiency of the illumination light 16 can also be improved by forming the side surface 10c of the transparent rod 10 as an inclined surface (an inclined surface cut inward from the upper side to the lower side in FIG. 12).

[0050]

According to the present invention configured as described above, light is emitted from the linear light source device so that its optical axis is substantially parallel to the document surface. Since the optical axis of the reflecting surface is reflected so as to be deflected to the original surface side, the original surface can be effectively illuminated. For this reason, the light emitted from the linear light source device is emitted from the original surface. It can be effectively used for surface illumination.

Further, according to the present invention, since the linear light source device is arranged so that the optical axis of the light to be emitted is substantially parallel to the document surface, the space factor is good and the size is small. can do.

Further, according to the invention described in claim 4, since the unevenness of the illuminance on the document surface can be almost eliminated, the reading error due to the unevenness of the illuminance can be very effectively prevented.

Further, according to the invention described in claim 5, since the metal base of the mounting plate for mounting the light emitting element functions as a heat radiating plate, it is possible to effectively prevent the temperature rise of the light emitting element. The amount of light emitted from each light emitting element can be increased by passing a large current through the light emitting element.

Further, according to the invention of claim 6,
The light leaking from the side portion of the light emitting element can be almost eliminated, the durability of the light emitting element can be improved, and the light source unit can be handled easily.

[Brief description of drawings]

FIG. 1A is a plan view in which a part of a linear light source device (LED array) incorporated in a conventional contact image sensor is cut away, and FIG. 1B is a vertical sectional view of the same.

FIG. 2 is a circuit diagram of the LED array shown in FIG.

FIG. 3 is a vertical cross-sectional view of a conventional contact image sensor incorporating the LED array shown in FIGS. 1 and 2.

FIG. 4 is a graph showing a change in output voltage of a photoelectric conversion element according to a change in an angle of a cover glass in the contact image sensor shown in FIG.

5 is a grab showing a measurement result of an illuminance distribution according to a position on a document surface in a longitudinal direction in the contact image sensor shown in FIG.

FIG. 6A is a front view of another conventional linear light source device incorporated in a contact image sensor, and FIG. 6B is a side view of the same.

FIG. 7A is a plan view of an LED array used in Examples and Reference Examples of the present invention, FIG. 7B is a longitudinal sectional view in the longitudinal direction of the same, and FIG. It is a longitudinal cross-sectional view in the width direction, and (D) is a plan view of the same metal base wiring board.

8A is a plan view in which a part of the linear light source device incorporating the LED array shown in FIG. 7 for use in Examples and Reference Examples of the present invention is disassembled and a part is cut away, B) is a side view of the above.

9 is a side view showing a pattern of a light diffusing surface of the transparent rod shown in FIG.

10 is a schematic view of an example in which the linear light source device shown in FIG. 8 is incorporated.

FIG. 11 is a schematic view of a contact type image sensor of the first embodiment of the present invention in which the linear light source device shown in FIG. 8 is incorporated.

12 is a specific vertical cross-sectional view of the contact image sensor shown in FIG.

13 is a graph showing the measurement result of the illuminance distribution according to the position in the length direction of the document surface in the contact image sensor shown in FIG.

FIG. 14 is a schematic diagram of a contact image sensor according to a second embodiment of the present invention.

[Explanation of symbols]

 10 Transparent Rod 14 Linear Light Source Device 16 Illumination Light 17 Original Surface 18 Optical Axis 24 LED Array 26 Metal Base Wiring Board 31 Reflective Surface 41 LED Element

Claims (6)

[Claims] 1. A linear light source device arranged such that an optical axis of light to be emitted is substantially parallel to a document surface, and an optical axis of light emitted from the linear light source device is the above-mentioned. A document illuminating device in an image reading apparatus, comprising: a reflection surface that reflects the light so that the light is deflected to the document surface side. 2. The device according to claim 1, wherein the reflecting surface is an elongated flat surface. 3. The device according to claim 1, wherein the reflecting surface is a thin concave surface. 4. The linear light source device has a long light-transmitting rod and a light source unit arranged near at least one end face of the light-transmitting rod, and is emitted from the light source unit. 4. The light is incident on the translucent rod and then is emitted to the outside from the outer peripheral surface along the longitudinal direction of the translucent rod.
The device according to. 5. The light source unit includes at least one light emitting element arranged near at least one end surface of the light transmitting rod, and a mounting plate to which the light emitting element is mounted, The mounting plate has a metal base, an insulating layer formed on the metal base, and a conductor wiring pattern formed on the insulating layer, and the electrodes of the light emitting element are connected to the conductor wiring pattern. The device according to claim 4, wherein the device comprises: 6. The light source unit is housed in an opaque annular frame body arranged on the mounting plate so as to surround a light emitting element mounted on the mounting plate, and in a hollow portion of the annular frame body. The device of claim 5, further comprising a translucent material.