TWI454179B - A white light emitting device for an image reading device, and a linear lighting device using the same - Google Patents

Description

White light-emitting device of image reading device and linear illumination device using same

The present invention relates to a white light emitting device for an image reading device and a linear lighting device using the same. In particular, it relates to a white light-emitting device equipped with a white LED used in an image reading device and a linear illumination device using the same.

In a machine such as a facsimile machine, a photocopier, or a hand-held scanner, an image reading device such as an image sensor is used as a device for reading an original. Generally, such an image reading apparatus uses a short image path length and is easily assembled to a close-contact type image sensor of a machine.

The close-contact type image sensor has a linear illumination device that illuminates a document surface linearly across a main scanning range. As a linear illumination device, a light guide that is long in size is used, and light incident on a light source disposed on an end surface of the light guide body is transmitted while being reflected by the internal surface and transmitted by a linear emission surface in the longitudinal direction. Irradiation type is known.

A light source of such a linear illumination device is known as a white LED composed of a blue LED chip and a YAG-based phosphor. The white LED light source, corresponding to the reading of the color image, is simpler than the multi-chip LED emitting RGB three-color light, and has the advantages of brightness characteristics, miniaturization, and weight reduction, and the luminous efficiency is improved as a close-contact type image. The light source of the sensor is used.

Further, a linear illumination device in which an LED composed of a plurality of light-emitting elements is disposed as a light source on an end surface of a light guide body is required to be sufficiently mixed in the light guide body without fading the color balance, and the light-emitting color of the plurality of wafers is released. It is required to illuminate a color original as a line of illumination with a uniform hue. In order to solve these problems, Patent Document 1 and the like disclose an invention having a feature in the shape of a light guide.

Further, Patent Document 2 discloses that when a white LED is mass-produced, a considerable degree of unevenness occurs between the emission wavelength of the blue LED chip and the emission luminance. Further, the amount of the fluorescent particles mixed in the YAG-based phosphor of the covering member or the unevenness of the dispersion affect the white light to be mixed, and as a result, the completed white LED greatly occurs in both hue and brightness. Ragged.

Here, referring to Fig. 16, a part of the chromaticity coordinates is used to explain the uneven distribution of the luminescent color of the white LED when the batch is mass-produced. The map shown in Fig. 16 is disclosed in Patent Document 2. The respective black dots shown in Fig. 16 show the color tone data of each of the white LEDs, and the color tone thereof is shown as being striped in the upper right direction. More specifically, in accordance with the chromaticity of JIS Z 8110, the white region almost blue on the line passing through the white dots by the blue color is dispersed in a strip shape. Here, the dispersion in the wide direction (arrow line A) is mainly due to the variation of the hue due to the variation of the emission wavelength of the blue light-emitting element, and the dispersion in the long-side direction (arrow line B) is mainly due to the fact that the cover member is mixed with the firefly. The amount of light particles or the staggered dispersion of the resulting hue. In addition, since the emission wavelength of the blue light-emitting element is largely different between batches, the dispersion in the width direction of the actual mass production (arrow line A) is further expanded (see Patent Document 2).

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2006-287923

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2004-119743

[Patent Document 3] Japanese Patent No. 3990437

Here, when such a white LED is used to constitute a light source of a linear illumination device for an image reading device, only a white LED whose luminescent color is selected in a desired chromaticity range is used, and the center color is used. It is better from the viewpoint of uneven color tone. However, when only a white LED of a specific grading product is used, other grades of the product become useless, and there is a problem that the total cost required to start the white LED is high.

The present invention has been made in view of the foregoing problems, and provides a white light-emitting device that combines and constitutes a white LED that emits light with a wide whiteness deviating from a desired whiteness, and color-mixes its luminescent color to emit a desired chromaticity. And use his linear lighting device. Further, in order to increase the productivity of the white LED by increasing the usability of the white LED having a wide range of chromaticity, the manufacturing cost of the white light-emitting device is lowered.

A white light-emitting device related to the image reading device of the present invention is used for reading an image using a white LED having a blue LED chip and a phosphor. The white light-emitting device of the device is characterized in that: a white light emitting white chromaticity which is shifted by a specific white area of a CIE (International Commission on Illumination) chromaticity diagram to the blue side, and a white light emitting by the aforementioned specific a second white LED having a chromaticity shifted toward the yellow side of the white region, the light source portion disposed adjacent to the optical axis in the same direction, and the blue LED chip independently driving the first and second white LEDs a current control means for controlling, by the PWM, a driving current of at least one of the first and second white LEDs, by inversely proportional to a target chromaticity point of the CIE chromaticity diagram to the first white LED Setting a distance between the illuminating chromaticity point and a distance from the target chromaticity point to the illuminating chromaticity point of the second white LED to set a respective pulse width for driving the first and second white LEDs And adjusting the color mixture of the light from the first and second white LEDs to the chromaticity of the specific white area.

A white light-emitting device according to the image reading device of the present invention is a white light-emitting device using an image reading device having a blue LED chip and a white LED of a phosphor, and is characterized in that: white light is emitted by CIE The first white LED of the chromaticity of the specific white area of the chromaticity diagram shifted to the blue side and the second white LED of the chromaticity of the white light that is shifted from the specific white area to the yellow side make the optical axis approximately the same direction a light source unit disposed adjacent to the ground, and a current control means for independently driving the blue LED chips of the first and second white LEDs; the current control means continuously supplying a constant current to the first and second white The white light in the LED emits a white LED that is close to the chromaticity of the target chromaticity point of the CIE chromaticity diagram, and the PWM control current is supplied to the other white LED, so that the duty ratio of the PWM control is set to be inversely proportional to a distance between a chromaticity of the white LED of the one of the CIE chromaticity diagrams and the target chromaticity point, and a distance between a chromaticity of the other white LED and the target chromaticity point, and Mixing the first and second integral white LED emitting the white chromaticity to the specific region from.

In the linear illumination device according to the present invention, the light incident from the light source disposed toward the incident surface of the end surface of the rod-shaped light guide formed of the transparent member in the longitudinal direction is in the rod-shaped light guide. The inner surface reflection is simultaneously emitted by the light exit surface provided along the longitudinal direction, and the light source is the white light emitting device described above.

A linear illumination device according to the present invention is characterized in that the outer shape of the radiation surface of the white light-emitting device is such that it can be accommodated in the outer shape of the incident surface of the light guide.

According to the white light-emitting device according to the present invention, a white LED having a wide range of chromaticity can be utilized by using a white LED of a luminescent color which deviates from the chromaticity of a specific white region among the classified white regions provided as the article. In other words, the product cost of the white LED is lowered by reducing the number of unused products of the white LEDs formed by the former blue LED chips and the YAG-based phosphors.

Further, according to the white light-emitting device according to the present invention, in order to compensate for the chromaticity variation of the disadvantage of the white LED, it is not necessary to newly emit an LED chip emitting light of a different wavelength or to add a different type of fluorescent substance or to change the phosphor. The composition is such a complicated configuration as that of the prior art, and the illumination of a specific white region of the target can be performed.

Further, for example, by using the white light-emitting device according to the present invention as a light source of the linear illumination device, it is possible to economically manufacture a bright linear illumination device that is illuminated with a specific white color.

According to the present invention, the inventors of the present invention reviewed the characteristics of a white LED having a blue LED chip and a fluorescent material, and reviewed a white light-emitting device and a white-emitting illumination device that emit a high-output light with a uniform whiteness, and the light-emitting device is easily constructed. The present invention has been completed.

Further, the white color as the illumination light source of the present embodiment is typically determined according to the JIS standard shown in FIG. 4, and is determined according to JIS Z 8110 with reference to FIG. 1 "General color chromaticity distinction of various colors of the system". The classification is white, (blue) white, (purple) white, (yellow) white, (green) white, (light) pink, and is referred to as a typical "white" in the present invention.

The operation of adjusting the mixing ratio of the light so that the color of the illumination source becomes the target white is called white balance. This adjustment is performed using a measurement sensor jig. In the present embodiment, the spectrophotometer is used to measure or calculate the brightness, brightness, chromaticity, and xy coordinates on the CIE chromaticity diagram of the white LED. However, even if a measurement sensor fixture other than the spectrophotometer is used to adjust the white balance, there is no problem in implementing the present invention.

Each manufacturer of white LEDs is graded to provide a white point (x = 0.33, y = 0.33) on the CIE chromaticity diagram, so that a certain width and length of the typical white area is used as the illumination of the white LED. region. For example, the product catalogue (2008 edition) of Nichia Chemical Industry Co., Ltd. (hereinafter referred to as N company) is classified into four regions of a0, b1, b2, and c0 as shown in Fig. 5A. The coordinate values of the corners of the respective regions are shown in Fig. 5B. In addition, in the Toyota Synthetic Co., Ltd. (hereinafter referred to as T), the blue LED + phosphor type white LED product catalogue (2008 edition), as shown in FIG. 6A, the illuminating regions are classified into AA, AB, B3 to B6, 7 areas of C0. The coordinate values of the corners of the respective regions are shown in Fig. 6B. The total area after the classification of the two companies is the same on the CIE chromaticity diagram and overlaps, and the level of the subdivision is different.

Here, for the description of the present embodiment, these hierarchical regions are reclassified into three regions of the A, B, and C regions. In short, the a0 area of the N company is the same area as the (AA+AB) area of the T company (hereinafter referred to as the A area), the c0 area of the N company is the same area as the C0 area of the T company (hereinafter referred to as the C area), The (b1+b2) region of the N company is the same region (hereinafter referred to as the B region) as the (B3+B4+B5+B6) region of the T company, and is an overlapping region. The light-emitting area thus regraded in this manner is shown in Fig. 7A. The A region, the B region, and the C region shown in FIG. 7A are regions in which the luminescent chromaticity of the commercially available product of the white LED is classified. Further, the coordinate values of the corners of the respective regions are shown in Fig. 7B. In Fig. 7A, there are white dots (x = 0.33, y = 0.33) on the boundary between the B region and the C region, and the B region is closer to the blue region than the white dots as shown in Fig. 7A.

Hereinafter, this (A+B+C) region is referred to as a hierarchical white region. Further, the B region is referred to as a specific white region (a desired color tone), which is a target color tone of the luminescent color of the white light-emitting device in the embodiment. In this way, the manufacturer grades the white light of the white LED after the white light region, and the specific white area (B area) is located at the center thereof, and the specific white area is shifted to the blue side to connect the A area to the yellow area. Move to the area on the CIE chromaticity diagram of the C area. Further, as shown in FIG. 7B, the coordinate value (x, y) on the CIE chromaticity diagram is a specific white area (B area) of (0.296, 0.276), (0.283, 0.305), (0.330, 0.360), (0.330). , 0.318) The chromaticity in the range surrounded by 4 points. In addition, the A region is chromatic in the range surrounded by 4 points such as (0.280, 0.248), (0.264, 0.267), (0.283, 0.305), (0.296, 0.276), and the C region is (0.330, 0.318), ( The chromaticity in the range surrounded by four points such as 0.330, 0.360), (0.361, 0.385), (0.356, 0.351).

In addition, the image reading device used in the white light-emitting device or the linear illumination device according to the present invention does not cause the light source or its reflected light to be directly recognized by the human eye, but the photoelectric conversion sensor receives light. Identify the institution. Therefore, the center hue of the illuminating color is not necessarily the white point on the CIE chromaticity diagram (x=0.33, y=0.33), and the color tone of the selected light source is considered in consideration of the economical cost of the light source within the range that can be adjusted by the image reading apparatus. .

Further, as the coordinates of the center of the B region, the coordinate values of the corners common to the B3 to B6 regions shown in FIG. 6A (x=0.307, y=0.315) are used, and the target coordinate value to which the chromaticity should be achieved in the present embodiment ( Target chromaticity point). Therefore, the light source of the image reading apparatus of the present invention is preferably formed by using only the white LED of the B region, and it is preferable that the color unevenness can be easily suppressed, but the A area and the C area become unused. This is a subject that should be considered from a cost perspective.

The present invention provides a white LED that emits chromaticity of a gradation white area provided by a manufacturer, and adjusts the hues of the illuminating color using a white LED that emits an A region or a C region deviating from a specific white region (B region) as a luminescent color. And a white light emitting device or a linear lighting device. As a result, the number of white LEDs that become useless is reduced. Hereinafter, specific examples of the invention will be described.

[Example 1]

In the white light-emitting device used in the image reading device of the first embodiment, two white LEDs are provided. Any of the white LEDs includes a blue LED wafer and a phosphor layer that is excited by the emitted light from the blue LED wafer to emit yellow light. Also, yellow is a complementary color of blue. Here, the white light-emitting device 20 in which two white LEDs are provided will be described with reference to FIGS. 1 to 4 and FIG. 9 at the same time.

The white light-emitting device 20 of the present embodiment is configured to include a light source unit 10 and a current control unit 33. FIG. 1 shows a light source unit 10 of a white light-emitting device 20. In the light source unit 10, the first white LED 11 that emits white light of the A region shifted from the specific white region (B region) to the blue side among the above-described hierarchical white regions (A region + B region + C region) And a second white LED 12 that emits white light of the C region shifted from the specific white region (B region) to the yellow side is attached to the printed circuit board 15 adjacent thereto. Further, the first and second white LEDs 11 and 12 have their main light-emitting directions, that is, the optical axes are parallel to each other, and are arranged adjacent to each other so as to be approximately the same direction. On the printed circuit board 15, as the wiring 16 for supplying electricity, an anode line common to the two white LEDs 11 and 12 and two cathode lines connected to the respective white LEDs 11 and 12 are provided. These anode lines and the two cathode lines are connected to the external current control unit 33 (see FIG. 2) by terminals A, K1, and K2, respectively. The first and second white LEDs 11 and 12 constituting the light source unit 10 of the white light-emitting device 20 are individually driven independently by the current control unit 33. Further, in Fig. 1, the phosphor layer covering the blue LED chip is not shown.

As the white LED used in this embodiment, for example, a commercially available surface mount type LED package having an aspect ratio of about 2.0 × 1.2 mm (manufactured by Nichia Chemical Industry Co., Ltd.; NESW007A) is used, and the luminescent color tone is designated as the A area. And white LEDs in the C area. In addition, when a white LED of the above-mentioned model is purchased, a person who emits a light in the A region and a light in which the C region is emitted in a state in which a fixed forward current of 10 mA is emitted can be used by the above-described measurement sensor jig.

In the white light-emitting device according to the present invention, it is necessary to mix the white light of two white LEDs to obtain the chromaticity of the B region, and the relationship is described with reference to the CIE chromaticity diagram shown in FIG. Further, the coordinate values of the corners of the respective regions are the same as those of Fig. 7B. Here, the first white LED emits the white light LA1 of the chromaticity point PA1 of the A region on the CIE chromaticity diagram shown in FIG. 8, and the second white LED emits the white of the chromaticity point PC1 of the C region shown in FIG. Light LC1.

In order to match the color mixture of the illuminating colors of the first and second white LEDs to the point PD0 shown in FIG. 8, the brightness of the white light LA1 of the point PA1 and the brightness of the white light LC1 of the point PC1 are weighted to make a weighted average. The value of the chromaticity coordinate of the point PA1 and the chromaticity coordinate of the point PC1 become a specific chromaticity coordinate, and the brightness can be adjusted. Further, the point PD0 is a target point at which the color mixture should arrive, and the coordinate value is (x=0.307, y=0.315), which is a coordinate at the center of the aforementioned B region.

In the present embodiment, according to the adjustment of the brightness (brightness) of the illuminating color of the white LED, it is preferable to change the pulse width of the pulse width by changing the pulse width of the LED chip with a small change in the color tone. get on.

Next, a method of adjusting the color mixture of the white light-emitting device 20 of the present embodiment will be described. FIG. 2 shows an example of a circuit for driving the white light-emitting device 20. This circuit includes a light source unit 10 and a current control unit 33 of a current control means. The light source unit 10 corresponds to the portion shown in Fig. 1 . The current control unit 33 controls the current control units for the currents flowing to the first and second white LEDs 11 and 12 to be independently provided. For example, in each of the first and second white LEDs 11, 12, the current adjustment circuits 21, 22 of the two cathode terminals K1, K2 of the light source unit 10 are connected in parallel with each other. Further, the transistors T1 and T2 of the respective white LEDs 11 and 12 are connected to the current adjustment circuits 21 and 22, respectively. The transistors T1 and T2 are connected to the ground GND.

The current adjustment circuits 21 and 22 are provided with, for example, an operational amplifier, a transistor, and a current limiting resistor R1 or a current limiting resistor R2. The current control unit 33 causes a constant forward current to flow in each of the white LEDs 11 and 12, and the transistors T1 and T2 are switched by PWM control to control the lighting of the white LEDs 11 and 12. Such a current control unit 33 functions as a current The function of the control means.

Next, a description will be given of a current control for causing the illuminating color of the white light-emitting device 20 of the present embodiment to be mixed, which is a target point that should substantially reach the chromaticity diagram. FIG. 3 is a timing chart for PWM control of the lighting times of the first and second white LEDs 11, 12.

First, the period T of the pulse wave is set to 10 msec, and the current for driving the first and second white LEDs 11 and 12 is set to 10 mA by the current adjustment circuits 21 and 22, and the lighting time t1 of the first white LED 11 is made every time. One cycle is 5 milliseconds, and the white light-emitting device 20 is operated. Further, the drive currents of the white LEDs 11 and 12 are respectively set by the current adjustment circuits 21 and 22, and the lighting time t1 is adjusted by the transistor T1.

Next, the measurement sensor clip is placed at a position where the light emission from the two white LEDs 11 and 12 above the light-emitting surface of the white light-emitting device 20 can be sufficiently mixed, or the measurement sensor holder is placed above the scattering plate, and the white light-emitting device 20 is started. The chromaticity of the luminescent color is determined. Here, the chromaticity measurement is started with the tens of times or more of the period T as the measurement time.

Thereafter, the lighting time t2 corresponding to one cycle of the white LED 12 is adjusted by the transistor T2, and it is found that the chromaticity measurement value according to the light emission of the white light-emitting device 20 is almost the same as the central point PD0 of the B region shown in FIG. 8 (x= 0.307, y = 0.315) consistent lighting time t2.

Here, in order to make the chromaticity of the luminescent color mixed by the white light-emitting device 20 almost coincide with the point PD0 of the coordinate value of the almost central portion of the target B region on the CIE chromaticity diagram, by the current control unit 33 The PWM control causes the first white LED 11 to be lit with a duty ratio D1=t1/T, and the second white LED 12 can be lit with a duty ratio D2=t2/T.

Moreover, the color mixture corresponding to the first white LED corresponding to the coordinate position in the A region, or the coordinate position corresponding to the second white LED in the C region, the color mixture may not be matched. Point PD0. However, since it can be blended into the chromaticity in the B region, it is satisfied that the problem of the present invention is sufficiently solved. In addition, all of the graded white areas are A-zone + B-zone + C-zones are arched so that when a white LED of light having an extreme inner side of the arcuate shape of the A-zone and the C-zone is selected, the color of the mixed color is obtained. The degree coordinates are slightly off the B area. In this case, it is only necessary to judge whether or not the chromaticity of the color mixture is allowed.

A white light-emitting device that suppresses color unevenness with respect to a white LED that selects only a light that emits a relatively narrow specific white region, the white light-emitting device according to the present invention is used in combination with a graded white region provided as a product A white LED that illuminates the chromaticity of a particular white area. That is, according to the present invention, by reducing the hue deviation inherent to the white LED formed by the blue LED chip and the YAG-based phosphor, the number of white LEDs that are not used in the previous selection can be reduced.

In addition, according to the present invention, in order to compensate for the chromaticity of the defects of the white LED, there is no need for a new LED chip emitting light of different wavelengths or adding a different kind of fluorescent substance or changing the composition of the phosphor. The complicated configuration is carried out, and the production of a white light-emitting device that can emit light of a specific white area of a target is possible.

Further, as the current control of the white light-emitting device 20, the magnitude of the current for driving the white LEDs 11 and 12 may be controlled instead of the PWM mode control. The control of the magnitude of the current can be performed by the current adjustment circuits 21, 22. In addition, the control of the combined PWM method and the control of the current magnitude are also possible.

Further, in the foregoing embodiment, the chromaticity of the light emission of the white LED is explained in accordance with the graded white area provided by the manufacturer. However, the distribution of the chromaticity of the white LED light emitted by the blue LED chip and the YAG-based phosphor can also obtain the blue light-emitting region of the blue LED chip and the yellow region of the phosphor light emission on the CIE chromaticity diagram. The white area between them is a distribution of strips 66 as shown in FIG. According to the previously defined specification JIS Z 8110, a typical white area 67 of FIG. 1 (refer to FIG. 9) is extended to the outside of the hierarchical white area (A area + B area + C area) 65 as a CIE chromaticity diagram. The point on the blue side (x = 0.23, y = 0.21) from the white point to the yellow side (x = 0.41, y = 0.41) is almost an elliptical area of a long diameter. The present invention can also use the white LED of the strip-like region 66 of the chromaticity of the illuminating color distribution of the white LED in the typical white region 67.

The white LED that emits the white light of the chromaticity of the blue side of the desired white area (B area) is the first white LED, and the outer side of the graded white area is similarly emitted. The white LED in which the strip-shaped region 66 is shifted from the chromaticity of the yellow side of the desired chromaticity region (B region) is the second white LED, and a white light-emitting device is prepared in the same manner as in the above-described embodiment. Next, even when the illuminating color of the first white LED is the chromaticity of the white region which is more biased toward the blue side than the A region, or the luminescent color of the second white LED is the color of the white region which is more yellow than the C region In the case of the degree, the illuminance chromaticity of the white light-emitting device 20 may be similarly set to the chromaticity in the B region by the PWM control of the current control unit 33.

When the chromaticity of the light emission of the first or second white LED is selected in a wide area among the strip-shaped regions 66, the target chromaticity point or the specific white area of the mixed color of the two white LEDs is not necessarily limited. In the B region, as long as the central region between the chromaticity points of the two white LEDs is illuminated, the chromaticity point of the mixed color may be shifted to the blue side or the yellow side than the B region.

Thus, by making the chromaticity of the wide area outside the gradation white area selectable as the illuminating color of the first or second white LED, the usability of the white LED can be further increased to reduce the product cost.

[Embodiment 2]

In the second embodiment, the PWM control of the driving current for further improving the brightness of the white light-emitting device in which the two white LEDs used in the white light-emitting device of the first embodiment are used to multiply the luminescent colors of the two colors is further improved. Further, with the PWM control of the present embodiment, it is possible to select a white light-emitting device using a white LED whose chromaticity range of light emission is distributed over a wide area. Further, the luminescent colors of the first and second white LEDs of the second embodiment will be described with respect to the chromaticity in the A region and the C region, respectively, as in the first embodiment.

First, in the CIE chromaticity diagram, when the distance between the coordinate point of the chromaticity of each of the two white LEDs 11 and 12 to be used and the target point PD0 of the chromaticity after the color mixture is different, the adjustment is made. The current control of the chromaticity of the white light-emitting device composed of white LEDs. At this time, it is preferable to select the luminosity of the fixed current of the first white LED 11 and the second white LED 12 to be almost the same. In order to make the luminosity uniform, the luminosity level can be specified and purchased by the manufacturer or separately driven to measure the luminosity.

For example, as shown in the CIE chromaticity diagram of FIG. 10, the chromaticity LA2 of the illuminating color of the first white LED 11 is located at PA2 of the A area, and the chromaticity LC2 of the illuminating color of the second white LED 12 is located at the PC2 of the C area. The case where the line connecting the two points PA2 and PC2 is connected and adjusted to the hue of the point PD0 located almost at the center of the B area will be described. Therefore, the brightness of each of the illuminating colors may be adjusted so that the weights of the PA2 and the PC2 are weighted and the weighted average of the illuminating colors LA2 and LC2 is the coordinate value of the PD0. In the case of this embodiment, as shown in FIG. 10, the distance ratio between the distance (PA2-PD0) and the distance (PC2-PD0) is 1 to 2, so the ratio of the brightness of the illuminating colors LA2 and LC2 is adjusted to In contrast to the distance ratio of 2 to 1, the luminescent color of the color mixture from the white light-emitting device is changed to almost the chromaticity of the dot PD0.

The above description is as shown in FIG. 10, where the chromaticity PA2 of the first white LED, the target chromaticity point PD0 of the mixed color, and the chromaticity PC2 of the second white LED are almost the same straight line on the CIE chromaticity diagram. However, even if these are not on the same line, if the brightness of the illuminating colors LA2 and LC2 is set inversely proportional to the distance between the distance (PA2-PD0) and the distance (PC2-PD0), the mixed colors of the illuminating colors of the two can be appropriate. The ground is roughly the chromaticity of a specific white area (B area).

When the adjustment method of the color mixture is separately expressed, the brightness of the white LED that emits light at the chromaticity of the target point PD0 close to the mixed color chromaticity is the other one that emits light at a chromaticity farther from the position of the target point PD0. The white LED is higher. In the white light-emitting device of the present embodiment in which the two white LEDs have almost the same luminosity, the current control unit 33 is used to continuously supply the drive current of the white LED 11 which is closer to the target point PD0 by the current adjustment circuit 21 of FIG. Constant current (not pulse current). In this state, the drive current of only the other white LED 12 is also supplied by PWM control, and the pulse width t2 is determined so that the mixed color of the two white LEDs is combined with the target chromaticity in the same manner as in the first embodiment (see the figure). 11).

In addition to the current control shown in FIG. 11, the current control unit 33 is used to set the period T to 100 milliseconds, and t1 (the pulse width of the drive current PWM controlled by the white LED 11) is set to 90 milliseconds, and t2 is set to 45. In milliseconds, the color mixture is almost the target chromaticity, but its brightness confirms that the current control of Fig. 11 is higher. Of course, it is also appropriate to drive the white LED 11 continuously by setting t1 to be the same as the period, and setting t2 to half of t1 and driving the white LED 12.

The method of setting the pulse width of the above PWM control is performed, and for each of the first and second white LEDs, the chromaticity of each illuminance is measured in advance by the sensor fixture, and the chromaticity map is calculated separately from the CIE. The distance between the target chromaticity points PD0 after the color mixture. The drive current of this short white LED is supplied at a constant current. Further, when the current is supplied by the PWM control, the load ratio of the pulse width P is set to be extremely large. On the other hand, it is used to drive white LEDs with a long distance. The pulse width p used is preferably set to be inversely proportional to the pulse width P to the distance ratio. Of course, as in the first embodiment, it is also possible to monitor the color mixture by the sensor fixture, and to adjust the pulse width of the white LED that drives the longer distance from the target chromaticity point.

In the present embodiment, the ratio (t1/t2) of the pulse width t1 of the white LED 11 which is closer to the point PD0 and the pulse width t2 of the farther white LED 12 is set to be larger because t1 is extremely large. Big. In this case, it means that the distance (PC2-PD0) of the distance (PA2-PD0) can be lengthened, and the use of the white LED that emits light of a chromaticity farther from the target point PD0 of the color mixture can be utilized. This situation can improve the usability of white LEDs that emit light that deviates from the chromaticity of a particular white area (B area), and can reduce the total cost of purchasing white LEDs.

[Example 3]

Embodiment 3 relates to a linear illumination device 50 using the white light-emitting device 20 of Embodiment 1. This linear illumination device 50 will be described in detail with reference to Figs.

The linear illumination device 50 of the present embodiment is used, for example, for a document surface such as a paper surface of an illumination image reading device. As shown in FIG. 12, the linear illumination device 50 is provided with a rod-shaped light guide 51 made of a transparent material, and a light source unit 10 disposed to face the incident surface 54 provided at one end portion thereof. . The terminal wire 62 is interposed in the light source unit 10, and the current control unit 33 (not shown in Fig. 12) is connected as in the first embodiment. Next, the light guide body 51 is provided with a light guiding portion 52 that allows light incident on the incident surface 54 to be reflected on the inner surface of the light guiding body 51 while being guided in the longitudinal direction, and has a light spanning distance from the light guiding portion. The light exiting portion 53 of the light exiting surface for emitting light in a line direction in the side direction.

Further, the light from the light source unit 10 is incident on the incident surface 54 of the light guide 51 without being wasted, and as shown in FIG. 13, the outer size of the radiation surface 63 of the light emitted from the light source unit 10 is guided. The outer shape of the incident surface 54 of the light body 51 is designed to be sufficiently accommodated. For example, on the side of the light emitted from the light source unit 10, one white LED having a size of 1.2 mm × 2 mm is arranged as shown in Fig. 13, and the outer surface of the light source unit 10 on the side of the emitted light is 2.5. Mm (lateral direction) × 2 mm (longitudinal direction). On the other hand, the outer dimension of the incident surface 54 of the light guiding body 51 shown in FIG. 12 is 3.5 mm (W direction) × 2.5 mm (H direction). Further, by arranging the radiation surface 63 of the light source unit 10 as close as possible to the incident surface 54 of the light guide 51, the light from the white light-emitting device 20 is incident on the light guide 51 without waste.

Further, as the light guide body 51, for example, a light guide body for a three primary color light source that is disposed (arranged in a different position) corresponding to three types of wavelengths (for example, red, green, and blue) may be used. In short, light from a plurality of light sources having different wavelengths can be used to receive light from the incident surface, and each wavelength can be appropriately reflected and scattered in the light guide body, and the output of each wavelength can be equally distributed across the longitudinal direction to output light. The linear lighting is used by the designer. The details of the light guide having such a function are disclosed, for example, in Patent Document 1.

That is, the color of the illuminating color differs between the two white LEDs 11 and 12 of the light source unit 10 of the white light-emitting device 20 used as the light source, and the two illuminating center points are not at the same position, even from the white illuminating device. When the distance from 20 to the incident surface 54 is short and the color mixture is not sufficiently mixed therebetween, the light guide 51 can sufficiently mix the incident light from the incident surface 54 to emit a linear light having a uniform whiteness distribution.

The inventors of the present invention confirmed the aforementioned effects of the linear illumination device 50 of the present embodiment by the following steps. First, as shown in FIG. 14, the linear illumination device 50 is incorporated in a close-contact type image sensor unit (hereinafter simply referred to as a CIS unit) 60 constituting the image reading device. Further, although not shown, the current control unit 33 of the white light-emitting device 20 is connected via the connector 61.

In this CIS unit 60, the reflected light from the paper original 59 is imaged by the lens array 55 to the line sensor 56. As the linear sensor 56, a pixel sequence of three straight lines for photoelectric conversion for receiving light of each of red (R), green (G), and blue (B) is used (not shown). . The line sensor 56 is provided with three types of color filters corresponding to the transmission wavelength region of RGB on each pixel column. That is, each of the pixel columns functions in a light sensitivity corresponding to each of the RGB colors. Such a sensor array is described, for example, in Patent Document 3 and the like.

In other words, the CIS unit 60 can split the white reflected light from the paper original 59 into RGB colors, and measure the illuminance in each pixel arranged in the longitudinal direction of the pixel column. The illuminance measurement value of each of the pixels is expressed as an illuminance distribution corresponding to the other end surface of the one end surface of the longitudinal direction of the light guide 51.

Next, after the paper original 59 is replaced with the determined reference white paper surface, the first and second white LEDs 11 and 12 are driven by the current control unit 33 in the same manner as in the first embodiment. Next, the illumination light of the linear illumination device 50 is measured by using the contrast degree of each of the RGB colors as the illuminance distribution in the linear direction. At this time, the currents flowing to the two white LEDs 11, 12 are set to 10 mA, respectively. As a result of measuring the illuminance distribution, as shown in FIG. 15, the contrast ratios of the red and green phases are almost the same value, and the distribution in the longitudinal direction is approximately uniform. In addition, the distribution of blue in the long-side direction is an almost uniform distribution, showing a high degree of contrast compared to red and green.

The illuminating color of the white illuminating device 20 used in the linear illuminating device 50 of the third embodiment is a light source adjusted in the chromaticity of the region B of Fig. 7A in the first embodiment, and the blue contrast is slightly increased. . However, the difference in the degree of contrast between the red, green, and blue colors can be adjusted by controlling the data processing unit of the image reading device of the CIS unit. An advantage of taking the light emission from the white light-emitting device 20 of the first embodiment into the light guide 51 and linearly illuminating the paper surface is to illuminate the light guides 51 with different hues from the two white LEDs. The color is fully mixed. A disadvantage of the white LED composed of the blue LED chip and the YAG-based phosphor is that the yellow light is strong around the light-emitting beam, and there is color unevenness in the center and the periphery of the light beam. 15 is a diagram in which the respective illuminating colors from the first and second white LEDs are sufficiently scattered in the light guiding body 51 to be mixed, and the original surface is illuminated by a linear beam, and the reflected light is linearly sensed via the lens array 55. The device 56 is photoelectrically converted by light and output. As shown in Fig. 15, there is a difference in the contrast between the RGB colors (the blue difference is large), but the light from the original spans the main scanning direction of the CIS unit (from the side of the incident surface to the opposite side), so that the colors are not uneven. The color mixing of the ground confirmed that the system was almost uniform and homogeneous. Therefore, the linear illumination device of the present embodiment is an invention that effectively utilizes the characteristics of the white light-emitting device 20 of the first embodiment. Further, the white light-emitting device of the second embodiment should also be used as a linear illumination device having the same effect.

[Industry use possibility]

The white light-emitting device and the linear illumination device according to the present invention are effectively utilized in a corresponding color image reading device such as an image scanner, a facsimile machine, or a copying machine.

10. . . Light source unit of white light-emitting device

11. . . First white light emitting element

12. . . Second white light emitting element

13. . . Blue LED chip

20. . . White light device

33. . . Current control unit

50. . . Linear lighting device

51. . . Light guide

54. . . Incident surface

55. . . Lens array

56. . . Linear sensor

57. . . Printed circuit board for CIS

58. . . Transparent glass mandrel support table

59. . . Paper original

60. . . Closed-type image sensor unit, CIS unit

63. . . Radiation surface

65. . . Graded white area

66. . . Banded area

67. . . Typical white area

Fig. 1 is a perspective view showing a light source unit of a white light-emitting device according to Embodiment 1 of the present invention.

Fig. 2 is a view showing an example of a circuit diagram for driving a white light-emitting device according to Embodiment 1 of the present invention.

Fig. 3 is a view for explaining lighting time control of two white LEDs according to Embodiment 1 of the present invention.

Fig. 4 is a view showing a typical white area using a chromaticity coordinate according to the JIS Z 8110 standard.

Fig. 5A shows an example in which the light-emitting area of a manufacturer's white LED is divided into four levels and displayed on the CIE chromaticity diagram.

Figure 5B is a coordinate value of a corner of each region of the hierarchy according to Figure 5A.

Fig. 6A shows an example in which the light-emitting area of a manufacturer's white LED is divided into 7 levels and displayed on the CIE chromaticity diagram.

Fig. 6B is a coordinate value of a corner of each region according to the classification of Fig. 6A.

Fig. 7A is a diagram showing the luminescent chromaticity of a white LED commercially available product in the A, B, and C regions and displayed on the CIE chromaticity diagram.

Figure 7B is a coordinate value for each corner of the A, B, and C regions of the reclassification of Figure 7A.

Fig. 8 is a chromaticity diagram for explaining control of color light emission from two white LEDs of the white light-emitting device according to Embodiment 1 of the present invention.

Fig. 9 is a view for explaining a white light-emitting device used as a first or second white LED which emits chromaticity of a strip-shaped region on the outer side by a graded white region.

Fig. 10 is a view showing the chromaticity of luminescence of a white light-emitting device according to Embodiment 2 of the present invention.

Fig. 11 is a view for explaining lighting time control of two white LEDs according to Embodiment 2 of the present invention.

Fig. 12 is a perspective view showing the configuration of a linear illumination device according to Embodiment 3 of the present invention.

Fig. 13 is a view for explaining the radiation surface of the white light-emitting device used in the light source of the linear illumination device according to the third embodiment of the present invention.

Figure 14 is a cross-sectional view showing a CIS unit incorporated in a linear illumination device according to Embodiment 3 of the present invention.

Fig. 15 is a view showing an illuminance distribution diagram for dividing the illumination light into the longitudinal direction of RGB of the linear illumination device according to the third embodiment of the present invention.

Figure 16 is a diagram showing the distribution of chromaticity variations of white LEDs.

10. . . Light source unit of white light-emitting device

11. . . First white light emitting element

12. . . Second white light emitting element

13. . . Blue LED chip

15. . . A printed circuit board

16. . . Wiring

20. . . White light device

A. . . Terminal

K1, K2. . . Terminal

Claims (6)

A white light-emitting device is a white light-emitting device using an image reading device having a blue LED (light emitting diode) chip and a white LED of a phosphor, and is characterized by: white light emitting by CIE (International Commission on Illumination) The first white LED of the chromaticity of the specific white area of the chromaticity diagram shifted to the blue side and the second white LED of the chromaticity of the white light that is shifted from the specific white area to the yellow side make the optical axis approximately the same direction a light source unit disposed adjacent to the ground, and a current control means for independently driving the blue LED chips of the first and second white LEDs; and the current control means PWM (pulse width modulation) controlling the first And a driving current of at least one of the second white LEDs by inversely proportional to a distance from the target chromaticity point to the luminescent chromaticity point of the first white LED of the CIE chromaticity diagram and the target chromaticity point Setting a pulse width for driving the first and second white LEDs to a distance from the illuminance chromaticity point of the second white LED, and adjusting a mixture of the first and second white LEDs To the white chromaticity of a particular area. A white light-emitting device is a white light-emitting device using an image reading device having a blue LED (light emitting diode) chip and a white LED of a phosphor, and is characterized by: white light emitting by CIE (International Commission on Illumination) The first white LED of the chromaticity of the specific white area shifted to the blue side of the chromaticity diagram and the second white of the chromaticity of the white light that is shifted toward the yellow side by the specific white area a light source unit in which the LEDs are arranged adjacent to each other in the same direction, and a current control means for independently driving the blue LED chips of the first and second white LEDs; and the current control means continuously supplies a constant current Among the first and second white LEDs, white emits a white LED that is close to the chromaticity of the target chromaticity point of the CIE chromaticity diagram, and supplies a PWM-controlled current to the other white LED, so that the aforementioned PWM control The load ratio is set to be inversely proportional to the distance between the chromaticity of the white LED of the one of the CIE chromaticity diagrams and the target chromaticity point, and the distance between the chromaticity of the other white LED and the target chromaticity point. The value is adjusted by adjusting the color mixture of the first and second white LEDs to the chromaticity of the specific white area. A linear illumination device that reflects light incident on a light surface of a rod-shaped light guide body by a light source disposed toward an incident surface of an end surface of a rod-shaped light guide body formed of a transparent member A linear illumination device that emits light along a light-emitting surface provided along a longitudinal direction, wherein the light source is a white light-emitting device according to claim 1 of the patent application. The linear illumination device according to claim 3, wherein the outer shape of the radiation surface of the white light-emitting device is such that it can be accommodated in the outer shape of the incident surface of the light guide. A linear illumination device that reflects light incident on a light surface of a rod-shaped light guide body by a light source disposed toward an incident surface of an end surface of a rod-shaped light guide body formed of a transparent member Along the length A linear illumination device that emits light to a light-emitting surface that is provided is characterized in that the light source is a white light-emitting device according to claim 2 of the patent application. The linear illumination device according to claim 5, wherein the outer shape of the radiation surface of the white light-emitting device is a size that can be accommodated in the outer shape of the incident surface of the light guide.