JP2010219714A - Illumination device and image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adopt a white light LED of high luminance suitable for use in a linear illumination device, as a light source of an original document reader in terms of securing color reproducibility, by overcoming the problem that the classification is performed by the chromaticity of the synthetic light of the light emitting color of a blue light emitting chip and a complementary color emitted by exciting a phosphor and the variance of a light emitting spectrum, especially the peak wavelength of blue light, is large. <P>SOLUTION: In the illumination device and the image reading apparatus, the white LED 31 of the high luminance classified by the chromaticity, the phosphor for emitting the complementary color of the blue light among light from the white LED 31, an optical filter 70 for attenuating the light from a blue LED 41 among the light from the white LED 31, and the blue LED 41 classified by the peak wavelength complementing attenuation light from the blue LED 41 are used as the light source. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an illuminating device and an image reading apparatus using the illuminating device, and more particularly to an illuminating device using a light guide with white LED as a light source.

  In general, a facsimile reader, an image reader, or the like uses a document reading device including a contact image sensor that reads a document surface as image information.

  For example, in (Patent Document 1), a light guide is used, light is incident from the surface of both ends (both ends or one end), and a large number of triangular wave-shaped light refraction regions provided on one side surface of the light guide and / or There has been proposed a linear illumination device that is refracted or reflected by a reflection region and is emitted linearly.

  As a result, variations in the illuminance on the document surface are reduced, the distance from the linear illumination device to the document surface can be shortened, the light transmission efficiency can be dramatically improved, and an LED chip as a light source can be obtained. The number can be drastically reduced, and the cost can be reduced.

  6 is an explanatory diagram of an emission spectrum of a high-intensity white LED, FIG. 10 is an explanatory diagram of a chromaticity distribution range of the high-intensity white LED, FIG. 13 is an explanatory diagram of the spectral sensitivity of the photoelectric conversion element array, and FIG. 17 is an explanatory diagram of the chromaticity distribution range of the high-intensity white LED, FIG. 18 is an explanatory diagram of the reflectance of the blank paper, and FIG. 19 is an explanatory diagram of the color difference [ΔE] of the document. .

Light is made incident from the end (both ends or one end) surface of the light guide, refracted or reflected by a number of triangular wave-shaped light refraction areas and / or reflection areas provided on one side surface of the light guide, and emitted linearly. As a high-brightness LED suitable for use in the linear illumination device, white light is emitted by emitting a single color blue light-emitting chip and exciting a phosphor with part of the light emission to emit a complementary color of blue. White LEDs that convert color to light are known.
JP-A-10-150526

  However, the above-mentioned types of white LEDs are classified according to the chromaticity of the combined light of the emission color of the blue light emitting chip and the blue complementary color emitted by exciting the phosphor, and the emission spectrum, particularly the blue light emitting chip. Since the variation in the peak wavelength of the emitted color is large, it has been difficult to adopt it as the light source of the document reading apparatus from the viewpoint of ensuring color reproducibility.

  A light emission spectrum having a significantly different peak wavelength of the blue light emitting chip as in the example shown in FIG. 6 is also included in the chromaticity distribution range of the white LED as shown in FIG.

  Further, as in the example shown in FIG. 18, the reflectance of the original to be read even in the case of a blank sheet is not uniform depending on the wavelength of light, and is not flat particularly in the vicinity of blue (wavelength 380 to 480 nm). Further, as in the example shown in FIG. 15, even in the case of gray scale (white to gray to black), the reflectance of the original to be read is not uniform depending on the wavelength of light, and is not flat particularly in the vicinity of blue (wavelength 380 to 480 nm). .

Here, a photoelectric conversion element array having a spectral sensitivity as in the example shown in FIG. 3 using a white LED having a light emission spectrum with a significantly different peak wavelength of the blue light emitting chip as in the example shown in FIG. The color difference [ΔE] from the colorimetric value under the standard light D65 when a gray scale (white to gray to black) document is read as shown in FIG. There is a problem that the color difference [ΔE] is 3 or more (colors appear to be worn because the peak frequencies of the three blue LED chips are shifted).

  Therefore, a high-intensity white LED with a wide variation range of the peak wavelength of blue light has been difficult to adopt as a light source for an original reading apparatus from the viewpoint of ensuring color reproducibility.

  In order to solve the above-described problems, the present invention provides a white LED that emits white light that is color-converted by exciting blue light emitted from the first blue light emitting chip with a phosphor to emit a complementary color of blue. And an optical filter for attenuating the blue light emitted by the blue light emitting chip out of the white light emitted by the white LED, and a second blue light emission for emitting light in a color region that complements the blue region attenuated through the optical filter An illumination device using a chip as a light source was obtained.

(Embodiment 1)
FIG. 1 is a configuration diagram of an illumination device according to an embodiment of the present application, FIG. 2 is a cross-sectional view of the illumination device according to an embodiment of the present application, and FIG. 3 is an optical used in the illumination device according to an embodiment of the present application. FIG. 4 is an explanatory diagram of spectral characteristics of a bandpass filter (optical filter) used in the illumination device according to the embodiment of the present application, and FIG. 5 is an optical path description of the illumination device according to the embodiment of the present application. FIG.

  The illuminating device of FIG. 1 is typically a contact image sensor. As shown in FIG. 2, a platen 20 made of a translucent glass plate for closely contacting a document 10 and reading image information on the document 10 is provided. A linear illumination device (white) 30 as a first light emitting unit that irradiates the document 10 via the platen 20, and a linear illumination device (blue) 40 as a second light emitting unit that irradiates the document 10; A rod lens array 50 that receives reflected light (secondary reflected light) from the document surface and a photoelectric conversion element array 60 are included.

  As shown in FIG. 3, the linear illumination device (white) 30 serving as the first light emitting unit has an optical filter 70 disposed between a light emitting diode (LED) element 35 and a light guide 95, and a light emitting diode (LED ) The light from the element 35 passes through the optical filter 70 and is guided to the light guide 95.

  That is, in the linear illumination device (white) 30, a light emitting diode (1) that constitutes a first light emitting unit having an emission spectrum of a substantially blue first color gamut (wavelength of about 380 to about 480 nm) as shown in FIG. LED) element 35 emits light, and the phosphor is excited to emit a complementary color of the first color gamut (blue). A blue light whose intensity has been attenuated by passing through the optical filter 70 is mixed with complementary color light excited by a phosphor, and a white LED that converts color to white light is used as a light emitting diode (LED) element.

  Further, the linear illumination device (white) 30 uses an optical filter 70 having spectral characteristics as shown in FIG. 4 and attenuating light from the blue light emitting chip of the white LED described above.

  The linear illumination device (blue) 40 has a configuration as shown in FIG. 5 and uses a blue LED as a light emitting diode (LED) element 45.

  Next, the operating principle of this document reading apparatus will be described. FIG. 7 is a block diagram of an image reading apparatus according to an embodiment of the present application. The illumination light (white) 80 emitted from the linear illumination device (white) 30 and the illumination light (blue) 90 emitted from the linear illumination device (blue) 40 are irradiated onto the document 10 placed on the platen 20.

  Therefore, the reflected light corresponding to the density and color of the original 10 passes through the rod lens array 50 and forms an image on the photoelectric conversion element array 60. In the photoelectric conversion element array 60, the optical signal is converted into an electric signal and amplified, converted in the photoelectric conversion element array (A / D conversion) 61 from an analog signal to a digital signal, and finally stored as sensor data in a storage device 63. Is remembered.

  Conventionally, a xenon lamp (XE) is used as a light source of an original reading apparatus. However, the xenon lamp requires an inverter circuit or the like for driving, and has a problem that it is expensive as a system constituting the light source.

  Therefore, an LED array 110 is used in which a plurality of LED chips 110 are linearly arranged at predetermined intervals on an LED mounting substrate 100 on which circuit conductors as shown in FIG. 8 are formed. FIG. 8 is a configuration diagram of the LED array 100.

  However, in the conventional LED array 100, the illumination efficiency is low due to the directional characteristics of the LED chip 110, and the variation in the illuminance on the original surface is large, which has been a cause of deterioration in image reading performance. Further, it is necessary to provide a certain distance from the document surface to the LED array 100, the size of the unit itself is large, and the use of a large number of LED chips 110 causes a cost increase.

  FIG. 9 is a basic configuration diagram of the linear illumination device. The linear illumination device shown in FIG. 9 has a longitudinal direction of a light guide 140 made of a translucent material configured such that a cross-sectional area (diameter of a circle) decreases from the connecting portion 120 to the other end portion 130. A light refracting / reflecting region 150 made up of a large number of triangular wave prisms is provided on the side surface, and light from a light emitting diode (LED) element 160 provided at the end of the light guide 140 is introduced into the light guide 140. In addition to propagating, the light is refracted and emitted from the exit surface 145 above the light guide 140 by the light refraction / reflection region 150 to irradiate a line along the longitudinal direction of the light guide 140.

  Here, the LED chip 110 as a light source is mounted on the circuit board in the LED holding unit 170 provided at the end of the light guide 140 and reflects light to the concave reflection surface 180 formed in the LED holding unit 170. Thus, light is incident on the light guide 140 and guided to the light guide 140 through the connecting portion 120. In FIG. 5, the connecting portion 120 is formed in a cylindrical shape, and a light diffusion layer 175 is provided on the inner periphery thereof, and is a connecting portion that guides light from the LED chip 110 to the light guide 140.

  With this configuration, the light component that reaches the side surface of the connection portion 120 out of the light incident on the connection portion 120 is diffused by the light diffusion layer 175 so that most of the light component can enter the light guide 140. The light component incident on the light guide 140 is also emitted directly from the side surface of the light guide 140 or reaches the photorefractive / reflective region 150 while repeating total reflection on the side surface several times. The document is bent (ie, subjected to angle conversion) and emitted upward from the light guide 140 to illuminate the document.

  The light is not emitted directly from the side surface of the connection part 120 to the outside of the light guide 140 by the light diffusion layer 175, but is repeatedly reflected in the connection part 120 and guided to the light guide 140. Since the light is reflected from the reflection area 150 in the direction indicated by the solid line arrow in FIG. 5 and is emitted from the emission surface 145, the illuminance on the document surface can be made uniform.

  However, unlike the LED array 100 as described above, which easily increases the number of LED chips 110, a high-brightness LED chip 110 is required to obtain a sufficient amount of light. In order to realize color image reading, LEDs of three primary colors or white LEDs of R (red), G (green), and B (blue) light are required.

  Since the white LED has a chromaticity distribution range as shown in FIG. 10 as an example, an arithmetic unit 62 as correction means as shown in FIG. 7 is required.

  Here, the principle of operation of the correcting means will be described with reference to FIG. In FIG. 7, white LEDs 31 and blue LEDs 41 are used as light sources.

  The white LED 31 is driven with a constant current by a white LED drive circuit 32, and the blue LED 41 is driven with a constant current by a blue LED drive circuit 42. In FIG. 7, the photoelectric conversion element array 61 measures the wavelengths of the three primary colors of R (red), G (green), and B (blue) light, and outputs them as sensor data. The computing device 62 calculates illuminance from the sensor data stored in the storage device 63. Illuminance is stored as a set value in the storage device 63, and the calculation device 62 compares the sensor data with the set value stored in the storage device 63, and the current value is stored in the storage device 63 during shading. Correct and adjust to the set value. Finally, the corrected set value is stored in the storage device 63.

  Thereafter, at the time of image reading, the current value of the current flowing through the white LED drive circuit 32 and the blue LED drive circuit 42 is set and adjusted to the set value stored in the storage device 63. The read image data corrects the non-uniformity of the “light quantity distribution and RGB spectral sensitivity” corresponding to the sensor data stored at the time of shading, and the “illumination device” and “ Correction is performed using a “correction coefficient” unique to the “document reading device” to ensure color reproducibility.

  FIG. 11 is an explanatory diagram of an emission spectrum after complementing the lighting device according to the embodiment of the present application, and FIG. 12 is an explanatory diagram of a distribution range of chromaticity after complementing the lighting device according to the embodiment of the present application. 13 is an explanatory diagram of the spectral sensitivity of the photoelectric conversion element array used in the illumination device according to the embodiment of the present application, and FIG. 14 is an explanatory diagram of the color difference [ΔE] of the document after complementation.

The emission spectrum of the synthesized light after complementation is as shown in FIG. 11, and has a chromaticity range as shown in FIG. When a gray scale (white to gray to black) document shown in FIG. 15 is read by the photoelectric conversion element array having the spectral sensitivity shown in FIG. 13, the color difference from the colorimetric value under the standard light D65 [Δ E] is as shown in FIG. 14 and is improved within a color difference [ΔE] of 3 on a gray scale (white to gray to black).

Color difference [ΔE] is an L * a * b * color system in which color differences perceived to be equal in size are one of uniform color spaces that are intended to correspond to equal distances in space. The distance between two colors in (CIE 1976) is the same, and when the degree of color difference seems to be the same psychologically, the distance between the two colors is the same.

An example of the sensation for the color difference [ΔE] is shown below. Color difference [ΔE] 1.5 to 3.0: Level generally considered to be the same color Color difference [ΔE] 3.0 to 6.0: Range that can be handled as the same color at the impression level Color difference [ΔE] 6.0 to 12.0: Perceived as different colors.

  As shown in FIG. 7, the white LED 31 is driven by the white LED drive circuit 32 and the blue LED 41 is independently driven by the constant current by the blue LED drive circuit 42. The current value of the constant current drive is R (red), Comparison is made so that the illuminance calculated from the sensor data from the photoelectric conversion element array 60 that measures the wavelengths of the three primary colors of G (green) and B (blue) light becomes a set value stored in the storage device 63. The white LED driving circuit 32 and the blue LED driving circuit 42 are configured to be calculated and adjusted so that a current that is a set value stored in the storage device 63 during shading flows through the white LED 31 and the blue LED 41. Adjustment is performed and the adjustment value is stored in the storage device 63.

  Thereafter, at the time of image reading, the white LED drive circuit 32 and the blue LED drive circuit 42 are set and adjusted to the adjustment values stored in the storage device 63. The read image data corrects the non-uniformity of the “light quantity distribution and RGB spectral sensitivity” corresponding to the sensor data stored at the time of shading, and the “illumination device” and “ Correction is performed using a “correction coefficient” unique to the “document reading device” to ensure color reproducibility.

  In the present embodiment, the contact image sensor described above is used in an image reading system.

  FIG. 16 is a basic configuration diagram of the image reading system.

  The image reading system 200 includes a contact image sensor 210, a platen 220, a motor 230, a support shaft 240, a drive shaft 250, and a document pressing cover 260.

  The image reading system 200 includes a line provided in the contact image sensor 210 to read image information of the document 270 placed on the platen 220 that transmits light by operating an operation unit (not shown). The shape illumination devices 30 and 40 irradiate the original 270 with light. The contact image sensor 210 moves on two shafts arranged in parallel by a driving shaft 250 that is rotated on a support shaft 240 by a motor 230.

  Therefore, while the contact image sensor 210 is moved in parallel with the platen 220 by the motor 230, the reflected light from the document 270 is collected by the rod lens array and incident on the photoelectric conversion element array, and an electric signal is output by the photoelectric conversion element array. And output to an information processing apparatus (not shown).

  According to such a configuration, it is possible to realize an image reading system that is inexpensive, small, and has high reading performance.

  As described above, according to the present invention, a sufficient amount of light on the surface of the original can be ensured, the illumination on the surface of the original is uniform, the amount of light is relatively large, and the linear illumination is ensured in color reproducibility. Since the apparatus can be provided, it is extremely useful as a light source for image reading and illumination of an electronic blackboard, an image forming apparatus (printer, etc.), an image reading unit used in an image processing apparatus, or an image reading apparatus (scanner). is there.

The block diagram of the illuminating device which concerns on one embodiment of this application Sectional drawing of the illuminating device which concerns on one embodiment of this application Arrangement diagram of optical filter used for lighting device according to one embodiment of the present application Explanatory drawing of the spectral characteristic of the band pass filter (optical filter) used for the illuminating device which concerns on one embodiment of this application Optical path explanatory drawing of the illuminating device which concerns on one embodiment of this application Explanatory diagram of emission spectrum of high brightness white LED Block diagram of an image reading apparatus according to an embodiment of the present application Configuration diagram of LED array Basic configuration diagram of linear illumination device Explanatory diagram of chromaticity distribution range of high-intensity white LED Explanatory drawing of the emission spectrum after the complement of the illuminating device which concerns on one embodiment of this application Explanatory drawing of the distribution range of the chromaticity after the complement of the illuminating device which concerns on one embodiment of this application Explanatory diagram of spectral sensitivity of photoelectric conversion element array Explanatory drawing of color difference [△ E] of original after complement Illustration of the reflectance of the document Basic configuration of image reading system Illustration of chromaticity distribution range of high-intensity white LED Illustration of reflectivity of blank paper Illustration of color difference [△ E] of the document

10 Document 20 Platen 30 Linear illumination device (white)
35 Light-Emitting Diode (LED) Element 40 Linear Lighting Device (Blue)
50 Rod lens array 60 Light receiving device 70 Optical filter 80 Illumination light (white)
90 Illumination light (blue)
95 Light guide

Claims (5)

A first light emitting unit that emits light of a first color gamut;
A second light emitting unit that emits light of a second color gamut in a color gamut included in the color gamut of the first color gamut light;
A filter that transmits a part of the first color gamut light emitted by the first light emitting unit and attenuates the amount of light;
A fluorescent member for converting a part of the first color gamut light emitted by the first light emitting unit into its complementary color;
The first color gamut light transmitted from the filter whose light amount has been compensated by the second color gamut light emitted by the second light emitting unit, and the first color gamut emitted from the fluorescent member. An illuminating device that emits white light using a complementary color of light. A first light emitting unit that emits light of a first color gamut;
A second light emitting unit that emits light of a second color gamut in a color gamut included in the color gamut of the first color gamut light;
A filter that transmits a part of the first color gamut light emitted by the first light emitting unit and attenuates the amount of light;
A fluorescent member for converting a part of the first color gamut light emitted by the first light emitting unit into its complementary color;
The first color gamut light transmitted from the filter whose light amount has been compensated by the second color gamut light emitted by the second light emitting unit, and the first color gamut emitted from the fluorescent member. An illuminating device that emits white light using a complementary color of light. First and second light emitting units each having a blue light emitting chip for emitting blue light;
A filter that transmits a part of the blue light emitted by the blue light emitting chip of the first light emitting unit and attenuates the amount of light;
A fluorescent member that converts a part of the blue light emitted by the first light emitting unit into its complementary color;
White light is emitted by the blue light transmitted through the filter whose light amount is compensated by the blue light emitted by the second light emitting unit and the complementary color of the blue light emitted from the fluorescent member. Lighting device. The lighting device according to claim 1, wherein the first light emitting unit and the second light emitting unit are connected to a light guide that guides the emitted light. 5. The illumination device according to claim 1, wherein the illumination device is used in an electronic blackboard, an image forming apparatus (printer or the like), an image reading unit or an image reading apparatus used in an image processing apparatus.

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