JP2601569Y2 - Light source device of image reading device and image reading device using the same - Google Patents

Description

[Detailed description of the invention]

[0001]

This invention relates to a contact type image sensor used for a facsimile, a hand scanner, and the like.
The present invention relates to a light source device of an image reading device and an image reading device such as a contact image sensor incorporating the light source device.

[0002]

2. Description of the Related Art As shown in FIG. 1, a light source device incorporated in a one-dimensional image reading device such as a contact type image sensor has a shape that is long and thin along a main scanning direction X, and is made of epoxy resin, phenol resin, Dozens (for example, on a printed wiring board 10 based on a synthetic resin such as
About 30 LED elements for lighting (ie, LED
There is a linear light source device 12 on which a chip 11 is mounted. Then, such a linear light source device 12 is incorporated in a contact image sensor 13 as shown in FIG. In FIG. 2, light emitted from the LED chip 11 passes through the platen glass 14 and is incident on the document 17, is reflected by the document 17, passes through the platen glass 14 again, and is The light enters a rod lens array 16 such as a supported Selfoc® lens array (hereinafter referred to as “SLA”), and as a result, the S
The image of the original 17 is formed on the photoelectric conversion element 18 by the LA 16.

In such a contact type image sensor 13, in order to achieve economy, low power consumption, and miniaturization, the LED chips 1 arranged on the printed wiring board 10 are used.
There is a demand to reduce the number of 1s as much as possible and to make the LED chip 11 as close to the document 17 as possible. However, if the number of LED chips 11 is reduced or LE
When the D chip 11 is brought close to the manuscript 17, the manuscript 17
In this case, the illuminance of the portion near the LED chip 11 is large and bright, and the illuminance of the portion far from the LED chip 11 is small and dark.

In order to solve this problem, a linear light source device 12 of a contact type image sensor 13 shown in FIGS.
A linear light source device 20 as shown in FIG. In the linear light source device 20 shown in FIG. 3, an LED lamp (that is, a chip type LE) is opposed to both end surfaces 21a and 21b of a transparent rod 21 having an elongated rectangular parallelepiped shape along the main scanning direction X.
D) 29 is arranged. Note that these chip type LEs
As D29, an LED element 34 is arranged on a printed wiring board 35 having a base made of synthetic resin, and this LED element 34 is mounted on a transparent lens package 3 of a flat lens type.
For example, a one-package one-element type having a structure covered with 3 is used. And the above-mentioned chip type LED2
9 is a printed wiring board 1 having a synthetic resin base for mounting the chip type LED 29 and other electric components.
The anode electrode and the cathode electrode are respectively soldered to the wiring pattern No. 5 to be attached to the printed wiring board 15.

Therefore, these chip type LEDs 29
Is emitted from one end face 21 of the transparent rod 21.
a or 21b is incident on the inside of the transparent rod 21 and is formed on one surface of the outer periphery while facing the other end surface 21a or 21b while repeating total reflection on the outer periphery surface of the transparent rod 21. Since the light is diffusely reflected and diffused by the light diffusion surface 23, the light is emitted from a surface opposite to the light diffusion surface 23. The emitted light has a substantially uniform brightness in the main scanning direction X.

As a method of forming the light diffusing surface 23, there is blasting, and in addition to blasting, printing, vapor deposition, stamping of a diffusely reflecting substance, and the like are available. Further, the light diffusion surface 2
By appropriately changing the light diffusivity of No. 3 closer to the end face 21a or 21b, for example,
The linear light source device 2 having extremely uniform brightness in the longitudinal direction X of the transparent rod 21 (that is, the main scanning direction).
It can be set to 0.

However, in the linear light source device 20 shown in FIG. 3, if the chip type LEDs 29 arranged opposite to the both end surfaces 21a and 21b of the transparent rod 21 are each one due to space restrictions, even if the chip type LED 29 Type LED
1, the number of LED elements 34 is 1/15 compared to the linear light source device 12 shown in FIG. Therefore, the linear light source device of the contact type image sensor is not satisfactory.

The luminous intensity of the LED element 34 is substantially proportional to the forward current value in a practical range.
4 also increases in accordance with the current value. Furthermore, the number of chip type LEDs 29 is limited due to space restrictions and the like. From these points, even if the number of the chip-type LEDs 29 is small, it is conceivable to increase the luminous intensity of each chip-type LED 29 by flowing a forward current as large as possible to each chip-type LED. However, in this case, the LED element 34 in the chip LED 29 generates considerable heat, and the LED element 34
9 is mounted on a printed wiring board 35 having a synthetic resin base, and the chip type LED 29 is mounted on the printed wiring board 15 also having a synthetic resin base. Therefore, the chip type L
The temperature of the ED 29 rises, causing various adverse effects.

[0009] In order to correct such disadvantages ,
Suppress the temperature rise of light emitting element units such as chip type LEDs and LED chips . By increasing the luminous intensity of each light emitting element unit, it is uniform and sufficiently bright as in the conventional case shown in FIGS. Nevertheless, the image of a more compact and economical contact type image sensor
It is conceivable to provide an image reading apparatus such as a contact image sensor incorporating a light source device and the light source device of an image reading apparatus.

[0010] In order to enable such provision,
To the elongated light-transmitting rod, and a light-emitting element units, such as the elongated light-transmitting rod least one at least disposed on the end face vicinity one chip type LED, LED chips, the light emitting element And a mounting plate on which a unit is mounted. After light emitted from the light-emitting element unit is incident on the longitudinal light-transmitting rod, the light is emitted from the outer peripheral surface along the longitudinal direction of the longitudinal light-transmitting rod to the outside. Image reading with a contact-type image sensor configured to be released to the
In the light source device of the device, 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 electrode of the light emitting element unit is Connected to the above conductor wiring pattern
It is conceivable to configure so that

According to the light source device of the image reading apparatus configured as described above , the light radiated from the light emitting element unit is transmitted from the end face of the elongated light transmitting rod to the inside of the elongated light transmitting rod. And is emitted to the outside from the outer peripheral surface of the longitudinal light-transmitting rod as substantially uniform light in the longitudinal direction of the longitudinal light-transmitting rod.

Further, heat released from the light emitting element unit is transmitted to the metal base of the mounting plate via a conductor wiring pattern and the like, and is effectively radiated from the metal base to the outside. Temperature rise can be suppressed.

Next, the image reading constructed as described above is performed.
Specific examples of the light source device of the device are shown in reference examples shown in FIGS .
Will be described. The same parts as those of the conventional example shown in FIGS. 1 to 3 are denoted by the same reference numerals, and the description thereof will be omitted.

The contact type image cells shown in FIGS.
Linear light source device 30 of the capacitors are those that can be used to replace the linear light source device 12, 20 of the conventional example shown in FIGS.

In FIG. 4, a white coating layer 31 is formed on one side of the outer periphery of a transparent rod 21 having a flat and rectangular parallelepiped shape to make this one side a light diffusing surface. Then, the chip-type LEDs 29 arranged close to and opposed to both end faces 21a and 21b of the transparent rod 21 are mounted on a metal base wiring board 32 provided with a wiring pattern for mounting the chip-type LEDs 29. ing. Both end faces 21 of the transparent rod 21
The distance between a and 21b may be, for example, about 20 to 30 cm. The chip type LED 29 has a structure in which an LED element 34 is disposed on a printed wiring board 35 having a base made of a synthetic resin, and the LED element is covered with a flat lens type transparent resin package 33. Type LED chips.
Such a chip-type LED of one package and one element type
Is more suitable for increasing the luminous intensity of each LED element because it has better heat dissipation than the one-package two-element type. In general, as the mounting density of the LED elements increases, the heat dissipation tends to decrease, and the luminous efficiency per LED element tends to decrease.

In this embodiment , four chip type LEDs 29 are provided on one end face 21a of the transparent rod 21, and
The chip-type LEDs 29 are connected to each other in series. Similarly, on the other end surface 21b side of the transparent rod 21, four chip-type LEDs 29 similarly connected in series with each other are provided. In addition, by changing the pattern density of the white coating layer 31 depending on the position in the longitudinal direction X, for example, by decreasing the pattern density closer to the end face 21a or 21b, the light emitted from the transparent rod 21 is made uniform in the longitudinal direction X. Is becoming

FIG. 5 shows details of the metal base wiring board 32 shown in FIG. 4, and FIG. 6 shows a connection state between the metal base wiring board 32 and the chip type LED 29.

In FIGS. 5 and 6, the metal base wiring board 32 has an insulating paste layer 37 formed on almost the entire surface of a metal base 36 having good heat dissipation such as stainless steel or aluminum. A conductor wiring pattern 39 is formed on 37, and portions of the conductor wiring pattern 39 other than the electrode portions are covered with a solder resist layer 38.

The metal base wiring board 32 is, for example, a stainless base 36 having a thickness of 0.2 mm, and a 10 μm-thick
An insulating paste layer 37 made of glass is provided, and a conductor wiring pattern 39 and a resist layer 38 are partially laminated on the insulating paste layer 37, respectively. In this case, since the insulating paste layer 37 is very thin, there is almost no obstacle to heat conduction between the conductor wiring pattern 39 and the stainless steel base 36. The conductor wiring pattern 39 is formed of Ag-
It may be made of Pd or Cu. Then, the connection portions 40 are formed by the conductor wiring patterns 39 exposed from the portions where the solder resist layer 38 is not formed (that is, the openings 38a of the solder resist layer 38). The anode electrode A and the cathode electrode B of the chip type LED 29 and the both ends of the resistor 42 are soldered by the solder 41. The substantially semicircular concave portions 35a formed on both end surfaces of the printed wiring board 35 of the chip type LED 29 are
The anode electrode A and the cathode electrode 29 are provided so as to be surely soldered to the connection portion 40 through the concave portion 35a.

Therefore, when a current flows through the LED elements 34, the LED elements 34 generate heat. This heat is generated by the anode electrode A and the cathode electrode B of the LED chip 29, as shown by the arrow Y in FIG. 4
1. The heat is transmitted to the stainless steel base 36 via the conductor wiring pattern 39 and the insulating paste layer 37, and the heat is efficiently dissipated from the stainless steel base 36 into the air. For this reason, it becomes possible to make the current value of the forward current that can flow through one LED element 34 sufficiently larger than in the past, so that the luminous intensity per LED element can be increased.

More specifically, the temperature rise of the chip-type LED 29 after a constant current of 20 mA is passed through a printed circuit board having a base made of a phenol resin and one chip-type LED 29 is soldered for 20 minutes. Was about 20 ° C. On the other hand, the same chip type LED 29 is placed on the stainless base wiring substrate 32 shown in FIGS.
A constant current of 20 mA to one of
After a lapse of 0 minutes, the temperature rise of the chip type LED 29 was about 10 ° C. Since the temperature rise of the chip type LED 29 itself causes a decrease in the luminous intensity of the LED element 34, the temperature difference of about 10 ° C. makes the use of the stainless steel base wiring board 32 about 5% brighter. In the case of the stainless base wiring board 32, the constant current value can be increased to 22.5 mA.
0% brighter. In addition, the numerical value described here is simply
Only be increased emission intensity of the LED elements 34 are shown to be reliably enabled by the present reference example, about 1
The 0% increase in brightness is only one example of the effect of this embodiment . And if various methods described below are adopted,
The heat dissipation of the chip type LED 29 can be further greatly improved.

Incidentally, the thermal conductivity of stainless steel is 50
Since it is 0 × 10 ⁻⁴ cal / sec / ° C./cm 3, it is much higher than the thermal conductivity of the synthetic resin of 1 × 10 ⁻⁴ cal / sec / ° C./cm 2. However, thermal conductivity 5,000 × 10 ^-4 cal / sec / ° C / c
When the metal base 36 is made of m 2 aluminum, the heat dissipation can be further improved.

FIGS. 7 and 8 show a contact type image sensor 6 as shown in FIG.
0 is shown. In this case, a metal base wiring board 32 shown in FIG. 5 and another metal base wiring board 32 having a symmetrical shape with respect to the metal base wiring board 32 are formed of a longitudinal metal frame made of aluminum or the like. 19 are attached to both left and right ends as side cover plates. Reference numeral 61 denotes a light shielding layer formed on the inner surface of the document table glass 14 so as to face the transparent rod 21.

Accordingly, the light emitted from the chip type LED 29 is diffusely reflected and diffused by the light diffusion surface 31 formed on one side surface of the outer periphery of the transparent rod 21. And
The diffused light is emitted from the surface 21 c opposite to the light diffusion surface 31, and thus enters the original 17 through the original platen glass 14.

The metal base wiring board 32 based on a metal such as stainless steel has excellent workability such as bending and drilling and strength, and therefore, as shown in FIG. A mounting portion 32a for mounting the contact type image sensor 60 on which the device or the like is mounted to an apparatus body such as a facsimile or a supporting portion 32b for supporting the original platen glass 14 can be formed as necessary. Therefore, the side cover plate of the frame 19 and metal fittings for mounting to the apparatus main body, which are necessary in the case of the conventional example shown in FIG. 2, are not required. In the contact type image sensor 60 shown in FIGS. 7 and 8, the thickness of the platen glass 14 is set to, for example, 1.1 mm, and the metal frame 19 supporting the SLA 16 can be manufactured by extruding aluminum.

When the pair of metal base wiring boards 32 is attached to the metal frame 19 in a state where the metal base wiring boards 32 are in contact with the side end surfaces of the metal frame 19, the metal frame 19 further functions as a heat sink of the metal base wiring board 32. Since it functions to increase the heat dissipation area, the heat dissipation can be further enhanced.

[Problems to be Solved by the Invention] However, FIGS.
The light source device 30 of the contact type image sensor 60 shown in FIG.
Is the light emitted from the plurality of chip-type LEDs 29.
Leakage to the outside from the side of these multiple LED chips 29
Loss of light or uneven light due to stray light
Are likely to occur, which results in a sufficiently uniform and sufficiently bright illumination.
Can not do the light. The present invention has a simple configuration.
Image sensor that solves the above-mentioned problems
Light source device for image reading device such as
With the aim of providing an image reading device incorporating
I do.

[Means for Solving the Problems In order to achieve the above-mentioned problems
According to the present invention, there is provided a longitudinal light transmitting rod, and the longitudinal light transmitting rod.
Placed near at least one end of the sex rod
Light emitting element unit and the plurality of light emitting element units
And a mounting plate on which the plurality of light emitting devices are mounted.
The light emitted from the element unit is
Incident on the rod, and in the longitudinal direction of this elongated translucent rod
Image configured to be emitted to the outside from the outer peripheral surface along
In the light source device of the reading device, the mounting plate may include:
Metal base and insulating layer formed on this metal base
And a conductor wiring pattern formed on the insulating layer.
The electrodes of the plurality of light emitting element units are connected to the conductor arrangement.
Connected to the line pattern and attached to the mounting plate
The plurality of light emitting element units are used to
Prevents light from leaking out of the side of the element unit
The opaque common placed on this mounting plate for
Surrounded by an annular frame common to this common annular frame
Is disposed in the hollow portion of the common annular frame body of the common
A light-transmitting material is accommodated in the hollow portion as a filling layer.

[Action] According to the above light source device, from the light emitting element unit
The emitted light is transmitted from the end face of the elongated translucent rod to this length.
The longitudinal light-transmitting rod enters the hand-shaped light-transmitting rod.
From the outer circumferential surface of the rod in the longitudinal direction of the elongated translucent rod.
It is emitted outside as uniform light. Also, multiple light emission
Heat released from the element unit is
This is transmitted to the metal base of the mounting plate
It is effectively released outside from the genus base.
The temperature rise of the light emitting element units can be suppressed.
You. Also, light emitted from multiple light emitting element units
From the sides of these light emitting element units to the outside
Almost no leakage and individual light emitting element units
Light emitted from each other is effectively mixed and almost eliminated
The light enters the longitudinal light-transmitting rod without becoming scattered. Sa
Furthermore, it is housed in a common hollow portion of a common annular frame body
Multiple light-emitting elements by common filling layer made of translucent material
Sub-units in common to improve their durability.
Can be

[0027]

EXAMPLES Next, a description will be given of an embodiment of a light source device for an image reading apparatus according to the present invention 9 to 11 for, in the reference example shown in FIGS. 4-8, but using a chip-type LED 29, The contact image in the embodiment shown in FIGS.
In the linear light source device of the disensor, the chip type LE
Instead of D29, the same LED element (that is, LED chip) 11 as in the conventional example shown in FIGS. 1 and 2 is used. Then, the four LED chips 11 are directly connected to the conductor wiring patterns 39 on the metal base wiring board 51 by wire bonding or the like.

FIGS. 9 to 11 show an LED device 62 used in the linear light source device of the above embodiment.
In the LED device 62, the metal base wiring board 51 has the metal base 36, the insulating paste layer 37, and the metal base wiring board 32, similarly to the metal base wiring board 32 shown in FIGS.
The conductor wiring pattern 39 and the solder resist layer 38 are sequentially laminated. The lower surface electrode of the LED chip 11 is soldered to the connection portion 40 of the conductor wiring pattern 39.
Is, the upper electrode of the LED chip 11 is connected to the other connection portion 40 by wire bonding. And, by these connections, the four LED chips 11 are connected to each other in series. These four LED chips 11 as surrounding the entire, Ho made of an opaque synthetic resin such as a white Isuzu rectangular annular frame body 53 is attached by bonding or the like on the metal base circuit board 51. Also,
The hollow portion 53a of the annular frame 53 is filled with a light-transmitting synthetic resin to form the filling layer 52. Therefore, the four LED chips 11 are packaged with this filling layer. 9 and 11, A and C indicate an anode electrode and a cathode electrode of the LED device 62, respectively.

The LED device 62 shown in FIGS. 9 to 11 is similar to the linear light source device 30 shown in FIG.
It can be used in place of D29. In this case, the side cover plate of the metal frame 19 shown in FIG. 8 is formed almost in the same shape as the metal base wiring board 32 shown in FIGS.
To the metal base 36 of the metal base wiring board 51 shown in FIG.
Can be attached to this side cover plate. Also, the metal base wiring board 51 shown in FIGS. 9 to 11 is formed to have almost the same shape as the metal base wiring board 51 shown in FIGS. 4 and 5, and as in the case shown in FIG. Can be used as a side cover plate of the metal frame 19.

In the LED device 62 shown in FIGS. 9 to 11, the four LED chips 11 are surrounded by an annular frame 53 made of an opaque synthetic resin such as white. To LED device 6
Very little light leaks out of 2. Therefore, LE
The light emitted by the D chip 11 can be efficiently introduced into the transparent rod 21, and the LED chip 11 can be inserted without passing through the printed wiring board 35 having a synthetic resin base as shown in FIG. Since it can be directly connected to the conductor wiring pattern 39 on the metal base wiring board 51, the heat dissipation can be further improved.

[0031]

According to the light source device of the image reading apparatus according to the present invention , the light emitted from the plurality of light emitting element units enters the longitudinal light transmitting rod from the end face of the longitudinal light transmitting rod. The light enters and is emitted to the outside from the outer peripheral surface of the elongated light transmitting rod as substantially uniform light in the longitudinal direction of the elongated light transmitting rod. Therefore, even if the number of the light emitting element units is small, it is possible to effectively illuminate a narrow area along the longitudinal direction of the elongated translucent rod.

Further, heat emitted from the plurality of light emitting element units is transferred to the metal base of the mounting plate via a conductor wiring pattern, so effectively dissipated to the outside from the metal base, said plurality It is possible to suppress the temperature rise of the individual light emitting element units. Therefore, multiple
Since it is possible to effectively suppress the temperature increase of the number of light emitting unit, by by increasing the current applied to the plurality of light emitting element units to increase the emission intensity of the plurality of light emitting element units, further illumination It can be done effectively. In addition, multiple light emitting devices attached to the mounting plate
The element unit is located on the side of these light emitting element units.
To prevent light from leaking out
The opaque common annular frame placed on the mounting plate
Enclosed in a common hollow of this common annular frame
Have been. Therefore, from a plurality of light emitting element units
The emitted light is on the side of these light emitting element units.
With little leakage to the outside and individual light emitting elements
The light emitted from the unit is effectively mixed
It can be inserted into the elongated translucent rod with almost no unevenness.
Light along the longitudinal direction of this elongated translucent rod.
Can evenly illuminate long, narrow areas evenly.
Wear.

Further, as described above, the light emitting element unit
Even if the number is small, extremely effective illumination can be performed, so that the entire light source device can be made compact and power consumption for obtaining the same illumination effect can be reduced. Moreover, it is attached to the mounting plate.
This light-emitting element unit surrounds the
Opaque common annular frame placed on the mounting plate
By storing a translucent material as a filling layer in the hollow part of
The plurality of light emitting element units are
Because they are packaged in common, a common annular frame
Made of a translucent material housed in a common hollow
Durability of multiple light emitting element units due to a common filling layer
They can be packaged in common for improved performance.
Therefore, necessary for a plurality of light emitting element units
The structure of the annular frame is simple, and a plurality of light emitting elements
Easy packaging of the unit with translucent material
Can be.

Further, according to the invention of claim 4, since by combined side cover plate of the image reading apparatus to the mounting plate of the light emitting unit in the light source device, provide a structure extremely simple image reading apparatus can do.

[Brief description of the drawings]

FIG. 1 is a plan view showing a conventional example of a linear light source device of a contact type image sensor.

FIG. 2 is a longitudinal sectional view of a contact type image sensor incorporating the linear light source device shown in FIG.

FIG. 3 is a perspective view showing another conventional linear light source device of a contact image sensor.

FIG. 4 shows a close contact type in a reference example for explaining the present invention.
FIG. 4 is a partially cutaway perspective view of a light source device of the image sensor .

5 is an enlarged plan view of a metal base wiring board of the light source device shown in FIG.

6 is a longitudinal sectional view showing a connection state between a metal base wiring board and a chip type LED of the light source device shown in FIG. 4;

FIG. 7 is a partially cutaway longitudinal sectional view of a contact image sensor incorporating the light source device shown in FIG. 4;

8 is a vertical sectional view of the contact type image sensor shown in FIG.

FIG. 9 shows an example of the LE of the light source device according to the embodiment of the present invention ;
It is a top view of D apparatus.

FIG. 10 is a longitudinal sectional view of the LED device shown in FIG.

FIG. 11 is a plan view of a metal base wiring board used in the LED device shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 LED chip (LED element) 19 Metal frame 21 Transparent rod 21a, 21b End surface 29 Chip type LED (LED lamp) 30 Linear light source device 31 White paint layer 32 Metal base wiring board 33 Transparent resin package 34 LED element 35 Printed wiring board 36 Metal Base 37 Insulating Paste Layer 39 Conductor Wiring Pattern 51 Metal Base Wiring Board 52 Filling Layer(Transparent material)  53 Annular frame 53a Hollow part 60 Close contact type image sensor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-243367 (JP, A) JP-A-6-295002 (JP, A) JP-A-6-217084 (JP, A) JP-A-59-1984 35492 (JP, A) JP-A-62-149180 (JP, A) JP-A-4-94193 (JP, A) JP-A-6-21940 (JP, U) JP-A-1-100175 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) H04N 1/04 101 H01L 33/00

Claims (4)

(57) [Scope of request for utility model registration] 1. A longitudinal light transmitting rod, and said longitudinal light transmitting rod.
Located near at least one end of the sex rodSeveral
Light emitting element unit of the above andMultipleLight emitting element unit
And a mounting plate on whichMultipleThe light emitted from the light emitting element unit is
After being incident on the elongated translucent rod, the elongated translucent rod
From the outer peripheral surface along the longitudinal direction of the pad.
ConfiguredImage reading deviceIn the light source device, the mounting plate may be a metal base and the metal base may be provided on the metal base.
The formed insulating layer and the conductor arrangement formed on the insulating layer
And the electrodes of the plurality of light emitting element units are connected to the conductor wiring pattern.
Connect to turnAnd The plurality of light emitting element units mounted on the mounting plate.
The knit is from the side of these light emitting element units
This mounting plate prevents light from leaking to the outside
Surrounded by an opaque common annular frame placed above
And placed in the common hollow part of this common annular frame, A translucent material is provided in the common hollow portion of the common annular frame.
The above-mentioned plurality of luminescence is accommodated as a filling layer
Element units can be packaged in common by this common packing layer.
The Light source for an image reading device
apparatus. 2. The light-diffusing device according to claim 1, wherein said elongated light-transmitting rod is formed in a substantially rectangular parallelepiped shape, and light is diffusely reflected on one outer peripheral surface of said elongated light-transmitting rod along the longitudinal direction. Means are provided so that most of the light incident on the elongated translucent rod is emitted to the outside from another outer peripheral surface opposite to the one outer peripheral surface. The light source device according to claim 1. 3. The light source device according to claim 1, wherein said light emitting element unit comprises an LED element. 4. An image reading apparatus incorporating the light source device according to claim 1, wherein the first and second light transmissive rods are arranged near both end faces of the elongated translucent rod. First and second mounting plates each having a second plurality of light emitting element units mounted thereon, wherein the first and second mounting plates are respectively provided as side cover plates on both side ends of a frame of the image reading device; An image reading device, which is provided.