JP4720831B2 - Lighting device for image sensor - Google Patents

Description

  The present invention relates to an illumination device for an image sensor equipped with a large number of LED light sources.

  With an increase in output of an LED light source used in an illumination system mounted on an image sensor configured with a small space, a heat dissipation structure that efficiently generates heat from the light source and a number of light source arrangement methods are required. For example, in FIG. 7 of JP 2002-218162 A (see Patent Document 1), a heat radiating member 108g is provided on the opposite side of the light guide 108c via the LED 108b, and the heat radiating member 108g has a substantially U-shaped cross section. By using this leaf spring, the space K is formed inside the U-shape. The space portion K includes a pair of flat plate portions 108g1 and 108g2 opposed via the space portion K and a connection portion 108g3 connecting the flat plate portions 108g1 and 108g2.

  FIG. 2 (see Patent Document 2) of Japanese Patent Laid-Open No. 5-56214 shows an LED array 21 that illuminates a document on a support 1 cut into a metal extrusion material such as an aluminum alloy that integrally supports a reading system. An image sensor is disclosed in which the interior of the support 1 forms two substantially independent spaces 30 and 31 and the LED array 21 is accommodated on the space 30 side.

  FIG. 1 (see Patent Document 3) of JP-A-2002-170998 discloses an electrically insulating substrate, two electrode portions formed on the substrate, and one electrode portion. A light-emitting element chip wire-bonded to another electrode part via a metal wire, a transparent resin part covering the light-emitting element chip and the metal wire surface, and a light-shielding and reflective resin part covering the transparent resin part The semiconductor light-emitting device comprised from these is disclosed.

Japanese Patent Laid-Open No. 2002-218162 (FIG. 7)

Japanese Patent Laid-Open No. 5-56214 (FIG. 2)

JP 2002-170998 A (FIG. 1)

  However, although the thing of patent document 1 is connecting with the housing | casing 108f using the elastic U-shaped leaf | plate spring and improving the thermal radiation effect, there exists a movable part of leaf | plate spring in the vicinity of LED108b. Depending on the movable state of the leaf spring, there is a problem that foreign matter is allowed to enter the light source side, and light emission is blocked by the foreign matter, resulting in unstable light emitted from the light source.

  The one described in Patent Document 2 uses a conductive material such as a metal for the support 1 to improve the shielding effect against harmful radio waves, and the reading system has an integrated structure, and independent spaces 30 and 31 are provided. Although the adverse effect due to dust is also taken into consideration by forming, the support 1 is a metal casing, and there is a problem that it becomes an expensive image sensor as a result of having a low degree of freedom in external design and requiring cutting. .

  Although the thing of patent document 3 has arrange | positioned many light emitting elements on a board | substrate, details, such as a radiation direction of light, are not described.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an image sensor illumination device that efficiently emits light emitted from a light source to the outside in a small space.

An illumination device for an image sensor according to a first aspect of the present invention is a light guide that extends in the reading width direction of a document, and is installed at both ends of the light guide to provide a hole, one end of the hole A holder for holding the light guide by inserting the outer peripheral end of the light guide into a part of the light guide, and the hole on the other end side of the holder so as to face the end of the light guide A plurality of LED chips having a single-sided two-electrode structure and a double-sided electrode structure along the outer edge of the space part on the other end side of the hole part on the surface of the substrate facing the end part of the light guide. A first mounting pad for mounting the LED chip having the single-sided two-electrode structure corresponding to the LED chip having the single-sided two-electrode structure, and the double-sided corresponding to the LED chip having the double-sided electrode structure. The second electrode on which the back electrode of the LED chip having the electrode structure is mounted A plurality of first electrodes provided on the substrate, which are arranged on the outside of the first mounting pad and are connected to one or the other electrode of the LED chip of the single-sided two-electrode structure by a metal wire. One or the other of the LED chips of the single-sided two-electrode structure adjacent to the other or one electrode of the LED chip of the single-sided two-electrode structure disposed inside the connection pad and the first mounting pad A plurality of second connection pads provided on the substrate for connecting the electrodes in common with metal wires and connecting the adjacent LED chips having the two-sided electrode structure in series, and outside the second mounting pads A plurality of third connection pads provided on the substrate and connected to each of the second mounting pads via a pattern, and arranged outside the second mounting pads. A plurality of fourth connection pads provided on the substrate for connecting the surface electrodes of the LED chips having the double-sided electrode structure with metal wires, and disposed inside the second mounting pads, respectively. The surface electrode of the LED chip having the double-sided electrode structure is connected by a metal wire, and the LED chip having the double-sided electrode structure connected to the fourth connection pad adjacent to the LED chip having the double-sided electrode structure is mounted. A plurality of fifth connection pads for connecting the second mounting pads through a pattern and connecting adjacent LED chips having a double-sided electrode structure in series are provided at the end of the light guide of the substrate. A plurality of the LED chips having a single-sided two-electrode structure and a plurality of the LED chips having a double-sided electrode structure are arranged on opposite surfaces and are electrically connected through a through hole. The LED substrate is disposed on the surface opposite to the installation surface of the LED chip having the single-sided two-electrode structure and the LED chip having the double-sided electrode structure .

According to the illumination device for an image sensor according to claim 1, the end of the light guide is inserted into a part of the one end side of the hollow region of the holder installed at both ends of the light guide, By arranging a large number of LED chips along the outer edge on a substrate having each mounting pad and each connection pad for each LED chip, uniform light is emitted at the end of the light guide. There is an effect that it is possible to obtain an illumination device for an image sensor which is irradiated and has a high luminance.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to FIG. FIG. 1 is a configuration diagram of an illumination device including a light guide of the image sensor according to the first embodiment. In FIG. 1, reference numeral 1 denotes a light guide that is mounted on an image sensor and is made of a transparent plastic material or a transparent glass material, and transmits light in the main scanning direction (the reading width direction of the document). A hollow holder made of a plastic material or the like that holds the side surfaces of the light guide 3 is an aluminum base on which an insulating layer is applied to the surface on which LED chips (LEDs) installed along the holders 2 at both ends of the light guide 1 are mounted. A board (LED board) using a material or a printed wiring material, 4 is a heat radiating plate (heat radiating plate) for radiating Joule heat generated in the LED board 3, and 5 is a guide hole provided at both ends of the heat radiating board 4. Is a rigid-type flexible cable for supplying power to the pattern of the LED substrate 3, and 6a is an electrode (flexible lead terminal) of the flexible cable. In the drawings, the same reference numerals indicate the same or corresponding parts.

  FIG. 2 is a partial cross-sectional view of the illumination device mounted on the image sensor according to Embodiment 1 of the present invention. In FIG. 2, 1 a is a light scattering layer that reflects light provided on the light guide 1, 7 is a light source in which LED chips of a plurality of colors are mounted on the LED substrate 3, and 8 is a heat radiating plate that generates Joule heat generated on the LED substrate 3. 4 is a heat-dissipating sheet or heat-dissipating grease for efficiently transferring heat to 4, and 9 is a gap that relaxes the stress in the longitudinal direction by thermal expansion and contraction of the light guide 1, and the inside of the gap is filled with a fluid resin. Reference numeral 10 denotes a spring plate made of SUS or phosphor bronze thin plate provided on the heat radiating plate 4 that absorbs the position change of the holder 2 or the LED substrate 3 due to thermal expansion and contraction of the light guide 1, and 10a is an elastic portion of the spring plate. . Reference numeral 11 denotes a housing of the image sensor. The housing 11 is used to form a gap 9 together with the heat sink 4, and the position of the LED substrate 3 and the heat sink 4 is changed by moving the elastic portion 10 a of the spring plate 10. Absorb. Reference numeral 12 denotes a transparent body that uses the inside of the image sensor together with the housing 11 as a sealed space. 2, the same reference numerals as those in FIG. 1 denote the same or corresponding parts.

  FIG. 3 is a single explanatory diagram of the LED chip mounted on the LED substrate 3, FIG. 3 (a) is an external view of the LED chip provided with an anode and a cathode electrode on the surface, and FIG. 3 (b) is an illustration on the surface. It is an external view of the LED chip which provided the anode electrode and the cathode electrode in the back surface. In FIG. 3, 7a is a face-up 2-wire type LED chip, and 7b is a face-up 1-wire type LED chip. The face-up two-wire type LED chip 7a has an anode electrode and a cathode electrode serving as wire bond terminals on the chip surface, and has a chip size of about 350 μm × 350 μm. Further, the face-up 1-wire type LED chip 7b is formed so that an anode electrode serving as a wire bond terminal is formed on the surface of the chip and a back surface of the chip is formed as a cathode region, and has a chip size of about 325 μm × 325 μm.

  FIG. 4 is a mounting diagram of an LED substrate mounted on the image sensor illumination device according to Embodiment 1 of the present invention. In FIG. 4, 30 is a pattern of the LED substrate 3, 30a is a common pattern (VLED), 30b is a divided individual pattern (C1), 30c is a divided individual pattern (C2), and 30d is a divided individual pattern. Pattern (C3). 40 is a pattern gap of the LED substrate 3, 41 is a non-flow prevention pattern gap provided for preventing the flow of the die bond material generated when the back surface of the LED chip 7 a is bonded with a die bond material, and 50 is a wire such as a gold wire. In addition, the edge part effective illumination area | region (phi4.5mm) of the light guide 1 is shown with a broken line.

  FIG. 5 is an LED board mounting diagram when the face-up 2-wire type LED chip 7a shown in FIG. 4 is replaced with a face-up 1-wire type LED chip 7b. As shown in the light source circuit of FIG. 6, even if the LED chip is mounted with the face-up 2-wire type LED chip 7a shown in FIG. 4, the LED chip is mounted with the face-up 1-wire type LED chip 7b shown in FIG. Even so, the pattern 30 of the LED substrate 3 can be configured in the same pattern.

  Next, the operation will be described with reference to FIGS. Power is supplied to the LED substrate 3 from a VLED terminal provided on the flexible cable 6 to light each LED chip. In the first embodiment, since there are three divided individual patterns (C1, C2, C3), a plurality of light source colors of a plurality of wavelengths are mounted for each individual wavelength. The light emitted from the light source 7 of the LED substrate 3 enters from the end of the light guide 1, propagates in the main scanning direction while totally reflecting the light guide 1, and is gradually scattered in the light guide 1. Illumination light that is irregularly reflected by the pattern 1a and is entirely uniform is applied to the reading position of the document.

  The light reflected by the image information on the document surface is converged by the lens and photoelectrically converted by the light receiving unit. The photoelectric conversion output preferably has a wide dynamic range. When the photoelectric conversion output is driven at high speed, the drive current of the light source 7 increases. For example, when the light source 7 is pulse-driven, when the loss voltage of the light source 7 is 1.5 V in addition to the amount of heat generated by light, a drive current of about 50 mA is necessary, so a loss power of about 75 mW per LED chip. appear. Furthermore, since the light source 7 is mounted with LED light sources of a plurality of emission colors such as RGB at the same time and is driven at the same time in addition to being lit in a single color, even greater Joule heat is generated.

  Therefore, in order to prevent distortion due to stress due to thermal expansion and contraction of the light guide 1 and the LED substrate 3, the elastic portion 10a of the spring plate 10 is provided in a portion in contact with the rigid image sensor casing to prevent the occurrence of distortion. .

  Further, Joule heat is efficiently applied to the heat radiating plate 4 installed on the back surface of the LED substrate 3 by installing the light source 7 on the LED substrate 3 side over the entire hollow region of the holder 2 in the irradiation region for the light guide 1. Dissipate. Furthermore, the parallelism of the light source 7 installed at both ends is ensured by sliding the position change accompanying the thermal expansion and contraction of the light guide 1 and the LED substrate 3 using the guide hole portion 5 provided in the heat radiating plate 4. .

  As described above, the pattern 30 of the LED substrate 3 can have the same configuration even though the position change of the light source that fluctuates in the irradiation region with respect to the end of the light guide 1 is alleviated and the light source 7 is an LED chip having a different type of configuration. There is an effect that a dedicated pattern configuration is not required.

Embodiment 2. FIG.
A second embodiment of the present invention will be described with reference to FIG. FIG. 7 is an LED board mounting diagram mounted on the image sensor illumination device according to Embodiment 2 of the present invention. In FIG. 7, reference numeral 60 denotes a through hole (thermal via) provided in the LED substrate 3, and reference numeral 70 denotes a die bonding target indicating an adhesion reference position when the light source 7 is adhered. In the first embodiment, the surface pattern of the LED substrate 3 is used to form a square arrangement configuration using different types of light sources 7a and 7b. However, in the second embodiment, the back surface pattern of the LED substrate 3 using the through holes 60. The light source arrangement similar to the shape of the end portion of the light guide 1 or the hollow portion region of the holder 2 becomes possible. For example, as shown in FIG. 8, the light guide is configured by forming a pattern extending from the terminal from the flexible cable 6 through the through hole 60 even when the power supply voltage to be supplied is different as shown in FIG. Even if 1 has a circular cross section, an arrangement corresponding to the shape of the light guide 1 is possible.

  In Embodiments 1 and 2, the case where the end portion is a circular light guide or a circular hollow holder has been described. However, the light guide has a substantially rectangular shape, a substantially rectangular shape, or another elliptical shape. The LED chip may be arranged along the outer edge inside the outer edge of the hollow region of the corresponding holder, and the LED chip may be additionally arranged in the central region of the hollow region.

  As described above, since a large number of LED chips can be arranged by installing the light source 7 in a similar manner inside the outer edge of the light guide 1, it is possible to configure an image sensor illumination device equipped with a high-intensity light source.

It is a block diagram of the illuminating device for image sensors by Embodiment 1 of this invention. It is a fragmentary sectional view of the illuminating device for image sensors by Embodiment 1 of this invention. It is a LED chip single-piece figure of the illuminating device for image sensors by Embodiment 1 of this invention. It is a LED board mounting figure of the illuminating device for image sensors by Embodiment 1 of this invention. It is a LED board mounting figure of the illuminating device for image sensors by Embodiment 1 of this invention. It is a circuit diagram of the light source part for image sensors by Embodiment 1 of this invention. It is a LED board mounting figure of the illuminating device for image sensors by Embodiment 2 of this invention. It is a circuit diagram of the light source part for image sensors by Embodiment 2 of this invention.

1 ・ ・ Light guide 1a ・ ・ Light scattering layer 2 ・ ・ Holder 3 ・ ・ Board (LED board)
4. ・ Heat dissipation plate (Heat dissipation plate) 5. ・ Guide (Guide hole)
6. ・ Flexible cable 6a ・ ・ Electrode (Flexible lead terminal)
7..Light source 7a..Face-up 2-wire type LED chip 7b..Face-up 1-wire type LED chip 8..Heat dissipation sheet or heat release grease 9..Air gap 10..Spring plate 10a..Elastic part 11.・ ・ Housing 12 ・ ・ Transparent body 30 ・ ・ Pattern 30a ・ ・ Common pattern (VLED)
30b ·· Individual pattern (C1) 30c · · Individual pattern 30d · · Individual pattern 40 · · Pattern gap 41 · · Non-flow preventing pattern gap 50 · · Wire (gold wire) 60 · · Through hole 70 · · Die bond target

Claims (1)

A light guide extending in the reading width direction of the document, and a hole provided at both ends of the light guide, and an outer peripheral end of the light guide inserted into a part of one end of the hole A holder for holding the light guide, a substrate disposed in the other end space of the hole so as to face the end of the light guide, and the light guide of the substrate A plurality of LED chips of a single-sided two-electrode structure and a double-sided electrode structure along the outer edge of the space part on the other end side of the hole on the surface opposite to the end of the hole, and corresponding to the LED chips of the single-sided two-electrode structure. A first mounting pad on which the LED chip having the single-sided two-electrode structure is placed, and a second electrode on which the back electrode of the LED chip having the double-sided electrode structure is mounted corresponding to the LED chip having the double-sided electrode structure. Mounting pads and an outer side of the first mounting pad. A plurality of first connection pads provided on the substrate for connecting one or the other electrode of each of the LED chips of the single-sided two-electrode structure with a metal wire, and inside the first mounting pad. The one side 2 adjacent to the other one side electrode of the LED chip of the single-sided two-electrode structure that is arranged and connected to one or the other electrode of the LED chip of the single-sided two-electrode structure adjacent to each other by the metal wire A plurality of second connection pads provided on the substrate to which the LED chips having an electrode structure are connected in series, and the second mounting pads are arranged outside, and the second mounting pads are patterned. A plurality of third connection pads provided on the substrate to be connected to each other, and an LED chip having the double-sided electrode structure disposed outside the second mounting pads. A plurality of fourth connection pads provided on the substrate for connecting the surface electrodes with metal wires, and arranged on the inner side of the second mounting pads, and the surface electrodes of the LED chips having the double-sided electrode structure The second mounting pad on which the LED chip having the double-sided electrode structure connected to the LED chip having the double-sided electrode structure and connected to the fourth connecting pad is mounted via a pattern. connect Te and a plurality of fifth connecting pads to be connected in series to the LED chip adjacent the double-sided electrode structure, respectively disposed on opposite faces an end of the light guide body of the substrate, a plurality of the A pattern in which the LED chip having a single-sided two-electrode structure and the plurality of LED chips having the double-sided electrode structure are electrically connected through a through hole is formed on the substrate with the LED chip having the single-sided two-electrode structure and Fine the double-sided electrode structure of the LED chip mounting surface opposite the image sensor lighting apparatus disposed in the plane of the.

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