JP2017098771A - Illumination device and image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illumination device and an image reading device, capable of easily and efficiently coping with a difference in color tint of a light source.SOLUTION: The illumination device includes a light guide unit having a light guide body including a light source, an incident surface on which light from the light source is incident, and an exit surface from which light from the incident surface is emitted. The light guide unit has correction means for correcting chromaticity of light from the light source.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an illuminating device and an image reading device, and is particularly suitable for an image scanner, a copying machine, a facsimile, and the like that illuminate a document surface and read an image by a line sequential method.

  2. Description of the Related Art Conventionally, a technique using an LED (Light Emitting Diode) as a light source of a document illumination device that is an illumination device in an image reading device is known. Then, an array arrangement type illumination device in which a plurality of LEDs are arranged in the main scanning direction, or LEDs are arranged on a longitudinal end face (end portion) of a light guide made of translucent resin or the like. It is divided into an end arrangement type illumination device for propagating the radiated light flux to the light guide.

  Here, the white LED that has been conventionally used in an array arrangement type image reading apparatus is an LED that is generally used for backlight illumination of a display or the like as a main application. On the other hand, the high-intensity LEDs used in the edge-arranged lighting device have a background that has been developed for general lighting equipment applications, and both tend to be greatly different in color even though they are the same white.

  The former white LED is provided with a finely subdivided color rank, because a single lighting device is configured using a plurality of white LEDs as an array arrangement type. On the other hand, the latter high-intensity LED has a feature that it has a high luminance and is less demanded on the market for general lighting equipment use, and has an extremely wide range of chromaticity ranks compared to white LEDs for array arrangement type. .

  Here, it is known that the luminescent color is assumed to be ranked in a desired chromaticity range in relation to dealing with the difference in color even with the same white color (Patent Document 1). Further, by setting a matrix coefficient of color space conversion means for converting the color space of the image signal (sensor RGB signal) according to the color tone rank of the light source, it is possible to improve the color reproducibility when the original is read. Known (Patent Document 2).

  Also, on the chromaticity diagram, there are a pseudo white LED shifted from the predetermined white region to the blue side and a pseudo white LED shifted to the yellow side, and the two pseudo white LEDs emit PWM light to modulate the pulse width and mix the colors. It is known that light is adjusted to chromaticity in a predetermined white region by emitting light (Patent Document 3).

JP 2004-119743 A JP 2003-008911 A JP 2011-040366 A

  However, using only the selected rank as known in Patent Document 1 is not efficient because other rank products are wasted, and the total cost is high.

  In the configuration of Patent Document 2, it is necessary to generate a plurality of color space conversion matrices for a range of light source chromaticity variation that can be assumed in advance. Although it seems that it can be easily realized at first glance, it is actually necessary to acquire multi-color patches (for example, 100 color patches) and generate an optimum matrix so that the acquired color information of each patch falls within a desired color difference. It is difficult to prepare a large number of color conversion matrices in advance.

  Further, in the configuration of Patent Document 3, the PWM modifiable frequency is about 20 kHz at present, and cannot be supported by high-speed reading. Further, since one of the two lamps emits PWM light, the light is emitted from the light guide and the original. The amount of illumination for illuminating the surface is not doubled and the efficiency is insufficient.

  An object of the present invention is to provide an illuminating device and an image reading apparatus that can easily and efficiently cope with the difference in color of light sources.

  In order to achieve the above object, an illumination device according to the present invention includes a light guide including a light source, an incident surface on which light from the light source is incident, and an exit surface on which light from the incident surface is emitted. A light guide unit, wherein the light guide unit has correction means for correcting chromaticity of light from the light source.

  Another illumination device according to the present invention includes a light guide unit including at least a light guide including a light source, an incident surface on which light from the light source is incident, and an output surface from which light from the light source is emitted. A chromaticity difference on a chromaticity coordinate of a CIExy chromaticity diagram between a chromaticity of light from the light source and a chromaticity of light from the light source emitted from the emission surface. Where Δcx and Δcy are the following conditions:

Δcx> 0.005
Δcy> 0.005

  According to the present invention, it is possible to provide an illuminating device and an image reading device that can easily and efficiently cope with different colors of light sources.

1 is a schematic view of a main part of an image reading apparatus equipped with an illumination device according to an embodiment of the present invention. Schematic of the principal part of the illuminating device which concerns on embodiment of this invention. Sub-scanning sectional view of an illumination device according to an embodiment of the present invention The A section enlarged view of the illuminating device which concerns on embodiment of this invention. Sectional drawing of the principal part in alignment with the BB line of the illuminating device which concerns on embodiment of this invention. Sectional drawing of the principal part in alignment with the CC line of the illuminating device which concerns on embodiment of this invention. (A) is a figure explaining the chromaticity rank of LED which is a light source in the illuminating device which concerns on embodiment of this invention on a chromaticity diagram, (b) is a principal part simplification figure. The figure explaining the spectral characteristic of the high-intensity LED in the illuminating device which concerns on embodiment of this invention. The figure explaining the spectral characteristic of standard illuminant D65 which is a standard light source The figure explaining distribution of chromaticity variation of general pseudo white LED

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

(Image reading device)
FIG. 1 is a sub-scan sectional view of an image reading apparatus equipped with a document illumination device as an illumination device according to an embodiment of the present invention. Here, in the present specification, “main scanning direction”, “sub-scanning direction”, “main-scanning section”, and “sub-scanning section” are defined as follows. That is, the main scanning direction is the direction perpendicular to the paper surface in FIG. 1 (first direction which is the longitudinal direction), the sub-scanning direction is the A direction (second direction) in the paper surface, and the main scanning section is the first direction. The cross section including the second direction (first cross section) and the sub-scanning cross section are the paper surface (second cross section) in FIG.

  In FIG. 1, reference numeral 107 denotes a carriage (integrated scanning optical system unit). The carriage 107 is a sensor (photoelectric conversion element) that reads a light beam from the document 101 illuminated by the document illumination device 103 that illuminates the document 101 placed on the document glass (document table) 102. A line sensor or image sensor) 105.

  Further, a plurality of folding mirrors 104 a to 104 d for guiding the light beam from the original 101 to the sensor 105 are provided. An image forming optical system (reduction optical system, image forming lens) 106 is provided as an image reading optical system that forms an image of a light beam based on image information from the document 101 on the surface of the sensor 105 as an image surface.

  The carriage 107 configured in this way is scanned in the direction of arrow A (sub-scanning direction) shown in the figure by a driving motor (sub-scanning motor) 108 as driving means. Each element constituting the carriage 107 scans a document without changing the relative positional relationship between the elements.

  In FIG. 1, the plurality of folding mirrors include a first folding mirror 104a, a second folding mirror 104b, a third folding mirror 104c, and a fourth folding mirror 104d in order along the optical path from the document 101 side. Each mirror is arranged so that the light flux from the original 101 enters the first folding mirror 104a to the second folding mirror 104b and from the second folding mirror 104b to the third folding mirror 104c. Furthermore, it arrange | positions so that it may inject into the 4th folding mirror 104d from the 3rd folding mirror 104c.

  The light beam incident on the fourth folding mirror 104d forms an image on the surface of the sensor 105 by the imaging optical system 106. In such a configuration, the image information of the document read by the sensor 105 is sent as an electrical signal to a specific image processing unit (not shown), and is output after being subjected to specific signal processing. Yes. The image reading apparatus 100 also has a power supply unit (not shown) for driving the carriage 107.

(Lighting device)
The document illumination device 103 as the illumination device according to the embodiment of the present invention will be described in more detail. FIG. 2 is a cross-sectional view in the longitudinal direction (first direction, main scanning direction) of the document illumination apparatus 103 according to the present embodiment. The document illumination device 103 includes a light source 110 that is a high-intensity white LED, a light guide 111 as a light guide unit that will be described in detail below, and a diffuse reflector (diffuse reflector) 118 provided outside the light guide 111. It consists of. FIG. 3 is a sub-scan sectional view of the document illumination device 103.

  As shown in FIG. 2, the light source 110 is disposed on one end surface (end portion) in the longitudinal direction (first direction) of the light guide 111, and the other end surface (end portion) has a diffuse reflection member. 119 is installed. The diffuse reflection unit 118 provided outside the light guide 111 is made of, for example, a white sheet. In this embodiment, the diffuse reflection portion 118 is a white sheet made of polyethylene terephthalate (PET resin) mixed with fine particles of a white color material. The light guide 111 is made of a member made of optical synthetic resin such as glass material or plastic, and in this embodiment, acrylic (PMMA) which is easy to mold is used.

(Light guide unit)
The light guide unit 109 excluding the light source 110 from the document illumination device 103 includes a light guide 111 that is long in the longitudinal direction (first direction, main scanning direction) and a separate diffuse reflector 118. As shown in FIG. 2, the light guide 111 has an incident surface 112 on which light from the light source 110 disposed on the end surface (end portion) in the longitudinal direction (first direction) is incident, and is directed from the light source toward the document 101. An emission surface 113 that emits light and a deflection surface 115 that faces the emission surface 113 are provided. As shown in FIG. 2, the deflecting surface 115 has a function of emitting a light beam incident from the incident surface 112 and traveling in the longitudinal direction (first direction) to the outside of the light guide 111. A first region 116 and a rectangular prism (second region) 117;

  Next, the diffuse reflection unit 118 will be described. The diffuse reflector 118 facing the deflecting surface 115 causes Lambertian reflection of the light refracted (transmitted) on the side surface of the rectangular prism (second region) 117 to the reflecting surface (first region) 116 of the deflecting surface 115. It has a function of making it incident (the transmitted light is emitted from the exit surface 113). FIG. 6 is a cross-sectional view of the light guide unit at the reflection surface (first region) 116 of the deflection surface 115, and FIG. 5 is a cross-sectional view of the light guide unit at the rectangular prism (second region) 117.

  As shown in FIG. 4, the light ray A 1 incident on the rectangular prism (second region) 117 is refracted (transmitted) on the side surface of the rectangular prism (second region) 117 and is arranged away from the second side surface 115. The diffuse reflection unit 118 diffuses the light. The diffuse reflection light diffused by the diffuse reflection unit 118 is incident on the reflection surface (first region) 116 of the light guide 111 and is further emitted from the emission surface 113 to irradiate the document 101. In this way, almost all of the light rays that pass through the emission surface 113 and illuminate the document surface are incident on the diffuse reflection portion 118 once.

(Light source chromaticity and diffuse reflection member)
As shown in FIG. 10, the pseudo white LED has a large variation in color tone. FIG. 10 shows the distribution of the variation in emission color tone when a certain white LED is mass-produced. As shown in the figure, the color tone is distributed in a band extending upward to the right. More specifically, the color tone is distributed in a band from a blue color according to the chromaticity classification of JIS Z 8110 to a white area substantially on a line passing through a white point and passing yellow. ing.

  Here, the dispersion in the width direction (arrow A) is mainly a variation in color tone caused by the variation in the emission wavelength of the blue LED, and the dispersion in the longitudinal direction (arrow line B) is the amount of fluorescent particles mixed mainly in the covering member. This is a variation in color tone caused by variation in dispersion. Since the emission wavelength of the blue LED has a large variation between lots, the dispersion in the width direction (arrow line A) is further widened in actual mass production.

  Therefore, each pseudo white LED manufacturer is in a typical white area near the white point (x = 0.33, y = 0.33) on the CIExy chromaticity diagram shown in FIG. A region having a certain width and length is provided by being ranked as a light emitting region of the pseudo white LED. For example, the ranks of the rectangular upper chromaticity regions A, B, and C in FIG. 7 are the provision ranks of the high-brightness LEDs, and the rectangular chromaticity regions a, b, c, d, e, and f are the low-brightness LEDs. (Low-brightness LEDs are LEDs used in array-arranged lighting devices).

  Here, the high luminance LED has a large hue variation factor compared to the low luminance LED, and there is little demand for subdivision of the chromaticity rank because it is a general lighting fixture application, and the area of the chromaticity rank to be provided is wide. The lower the brightness LED is, the more difficult it is to subdivide the chromaticity rank. When trying to select the rank equivalent to the low brightness LED, it becomes a custom product and the cost is significantly increased.

  As a document illuminating device that is an illuminating device in an image reading device, an edge arrangement type illuminating device is an evolutionary system compared to a conventional array arrangement type illuminating device, but both have advantages and disadvantages. is there. Although the array arrangement type illumination device has a low luminance relative to the high-intensity LED due to its configuration, the illumination device has a wide range of illumination light quantity by increasing / decreasing the number of LEDs although there are restrictions on the arrangement. Can be provided.

  On the other hand, the edge arrangement type illuminating device using high luminance LEDs is characterized in that the number of the high luminance LEDs as the light source is one or two and the number of light sources is smaller than that of the array arrangement type illuminating device. However, high-intensity LEDs are in high demand for general lighting equipment, and their development is active, but at the present time there are difficulties in terms of light quantity and light conversion efficiency. Therefore, it is difficult to deal with all the light quantity ranges required by the image reading apparatus at the present time.

  In the present embodiment, an image reading apparatus optimized for an array arrangement type illumination device can be replaced with an end arrangement type illumination device. Since the luminous efficiency of LEDs is increasing recently, the number of LEDs used can be reduced (compensating for the reduction in the number of light sources with the height of the light output compared to the array arrangement type), and the end arrangement with high cost merit There is a need for a type of lighting device.

  If such an end arrangement type illumination device can be used for the same light guide as the light guide for the array arrangement type, as long as the light distribution characteristics of the light source are not significantly different, a wide range of image reading can be performed by selecting LEDs. The required performance of the equipment can be satisfied. That is, on the premise that a light guide with high optical efficiency can be formed, it is possible to deal with a wide range of image reading apparatuses at low cost only by selecting an LED.

  In the image reading apparatus in which the illumination device according to the present embodiment is used, the human eye does not directly recognize the illumination light or its original reflected light, but has a configuration in which the photoelectric conversion element receives and recognizes it. Therefore, the central color tone of the luminescent color does not necessarily have to be the white point (x = 0.33, y = 0.33) on the CIExy chromaticity diagram, and the sensitivity and total efficiency of the photoelectric conversion element as the image reading device can be improved. It is set as appropriate in consideration.

  The low-brightness LED used in the array arrangement type illumination device uses rectangular chromaticity ranks a, b, c, d, e, and f on the CIExy chromaticity coordinates in FIG. The center color tone of the illumination color in the image design is (x = 0.304, y = 0.299). In FIG. 7A, a point (position) corresponding to the center color tone of the illumination color in the image design is indicated as T.

  On the other hand, the high-intensity LED used in the edge-arranged illumination device has been developed mainly for general lighting equipment, and the high-intensity LED used in this embodiment is different from the low-intensity LED. On the chromaticity coordinates, both x and y are greatly shifted to the + side. That is, the hue is relatively large, and the color is shifted in the red-green direction. In the present embodiment, it is assumed that the sample of the S point (x = 0.316, y = 0.327) in the CIExy chromaticity diagram of FIG.

  In the end arrangement type illumination device according to the present embodiment, a light guide unit including a light guide including an incident surface on which light from a light source is incident and an output surface from which light from the incident surface is emitted is a light source. Chromaticity correction means (correction means) for correcting the chromaticity of the light from. Then, when the chromaticity of the light from the light source is deviated from the target chromaticity, the correcting unit brings the chromaticity of the light from the light source emitted from the emission surface of the light guide 111 closer to the target chromaticity. Since almost all of the illumination light directed to the irradiated surface (document surface) passes through the diffuse reflection unit 118, the diffuse reflection unit 118 functions as a correction unit, and the chromaticity is corrected by the diffuse spectral reflection characteristic of the diffuse reflection unit 118. To do.

  In the present embodiment, the target chromaticity of the illumination light on the illuminated surface of the edge-arranged illumination device is assumed to be (x = 0.304, y = 0.299). In FIG. 7A, the point (position) corresponding to this target chromaticity is T. That is, in this embodiment, the chromaticity in FIG. 7A is made to approach the point T from the point S by the diffuse reflection unit 118 as the correcting means.

  FIG. 8 is an emission spectrum of a high-intensity LED whose chromaticity is indicated by a point S. The chromaticity of the illumination light after correction with the spectral reflectance characteristics of the diffuse reflection unit 118 allows the ranks a, b, c, d, e, and f in FIG. 7A as the chromaticity range of the illumination color. Therefore, it suffices if it is within the chromaticity region including a, b, c, d, e, and f. In FIG. 7B, the allowable range is simplified as W, and the corrected chromaticity within the allowable range is indicated as S ′. If it is within the permissible range of the permissible range W, this is a range that can be used as the system of the image reading apparatus.

  Here, when the chromaticity difference between the target chromaticity (point T) and the light source (point S) is defined as dix and diy, dix = 0.012 and diy = 0.028. In order to correct this chromaticity difference, the characteristics required for the diffuse reflection unit 118 are calculated as follows. Since the chromaticity of the diffuse reflection unit 118 is chromaticity of the object and depends on the illumination light by definition, a standard light source (standardized artificial light source) called standard illuminant D65 is used as the reference light for colorimetry. FIG. 9 is a graph of the spectrum defined as standard illuminant D65.

  On the chromaticity coordinates, the object color having a flat spectral reflectance in the entire spectral region where the spectral characteristics are not changed even when the light source color is mixed is (xb = 0.3127, yb = 0.3291). In FIG. 7A, this point (position) is U. Therefore, in order to correct the color of the light source color, (xr = xb−dix, yr =) when the chromaticity of the diffuse reflector 118 is (xr, yr) with (xb, yr) as a reference. yb-diy) may be selected.

  At this time, the chromaticity of the corrected illumination light only needs to satisfy a region including a, b, c, d, e, and f on the chromaticity diagram. As for xr, ± 0.005 and yr of ± 0.01 can be allowed. Therefore, it may be selected so as to satisfy the following expression.

  In the present embodiment, the diffuse reflector 118 satisfies (xr = 0.006, yr = 0.3009), so that the chromaticity (x = 0.316, y = 0. 327) becomes the chromaticity of the illumination light (x = 0.304, y = 0.299) after correction.

  That is, in FIG. 7B, when the chromaticity difference between the light source (point S) and the chromaticity (point S ′) corrected by the diffuse reflector 118 is Δcx and Δcy, the following expression is satisfied.

Δcx> 0.005
Δcy> 0.005
In the present embodiment, when the chromaticity difference on the chromaticity coordinates of the CIExy chromaticity diagram between the chromaticity of the point T and the chromaticity of the point S ′ is Δdx and Δdy, the following expressions are satisfied.

−0.005 <Δdx <0.005
−0.01 <Δdy <0.01
Here, the target chromaticity of the diffuse reflector 118 is created by arbitrarily combining the so-called diffusive white color material (BaSO4, TiO2, etc.) and the spectral reflectance characteristics of the base of the white color material. It is possible.

  Moreover, the diffuse reflection part 118 can be made to function as a correction | amendment means by setting it as the structure provided with the some diffuse reflection sheet from which a hue differs, or the coating surface by the composite coating material from which a hue differs.

  Up to this point, the correction of the light source chromaticity of a high-brightness LED of a sample has been described. However, it is possible to correct a light source color in an arbitrary rank other than the described light source color based on the same concept. . In practice, it is efficient to subdivide the light source colors to be used into several ranks and use the diffuse reflection unit 118 having chromaticity that can satisfy the conditional expression in a similar manner in combination.

  According to the present embodiment, almost all of the light beam incident on the light guide 111 irradiates the separate diffuse reflector 118 that is the secondary light source surface via the deflecting surface 115, and the light beam diffused and reflected almost lambertian is deflected. The incident surface is re-entered through the surface 115 and illuminates the irradiated surface through the exit surface. That is, almost all the light beams are directed to the irradiated surface through the diffuse reflection unit 118 provided independently, and therefore, even when a light source having a light source color different from the desired chromaticity enters, the chromaticity of the diffuse reflection unit 118 is changed. By selecting as appropriate, it becomes easy to obtain illumination light having a desired chromaticity on the irradiated surface.

  For the above-described reason, an image reading device optimized for an array arrangement type illumination device can also have a chromaticity substantially the same as that of the array arrangement type illumination device by appropriately selecting the chromaticity of the diffuse reflection portion. A lighting device can be provided. As described above, according to the present embodiment, the edge type illumination device having a different light source color can be applied to the image reading device optimized for the array type illumination device without any problem.

  Then, by completing and correcting the variation in color of the pseudo white LED within the illumination device, the availability of the image reading device can be improved and the cost reduction can be realized by relaxing the color rank selection.

(Modification)
As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

(Modification 1)
In the present embodiment, the description has been made with the focus on correcting chromaticity only by the diffuse reflection unit 118, but the present invention is not limited to this. For example, in the configuration of the combined method in which the chromaticity difference between the chromaticity variation center of the high-brightness LED and the target chromaticity (point T) is corrected by the transmittance of the light guide, and the residual is corrected by the diffuse reflection unit 118. It can be corrected. As specific means for changing the transmittance of the light guide, for example, a method of providing a coating on the emission surface 113 or adding a blooming material to a resin that is a material of the light guide can be applied.

  Further, instead of correcting all the chromaticity only by the diffuse reflection unit 118, all can be corrected by the light guide 111 alone. In other words, the correcting means may be provided in at least one of the diffuse reflector 118 and the light guide 111.

(Modification 2)
In the above-described embodiment, the image reading apparatus optimized for the array arrangement type illumination device is simply replaced with the end arrangement type illumination device, and good color reproducibility is obtained without changing other members. However, the reverse relationship may be used. In other words, the image reading device optimized for the end arrangement type illumination device can be replaced with an array arrangement type illumination device, and good color reproducibility can be maintained without changing other members. You can also.

110 .. Light source, 111 .. Light guide, 112 .. Incident surface, 113 .. Outgoing surface, 118 .. Diffuse reflection part (diffuse reflection member)

Claims (12)

A light source;
A light guide unit having a light guide including an incident surface on which light from the light source is incident and an exit surface from which light from the incident surface is emitted;
A lighting device comprising:
The illumination device according to claim 1, wherein the light guide unit includes a correction unit that corrects chromaticity of light from the light source. When the chromaticity difference on the chromaticity coordinates of the CIExy chromaticity diagram between the chromaticity of the light from the light source and the chromaticity of the light corrected by the correcting unit is Δcx and Δcy, the following conditions are satisfied. The lighting device according to claim 1, wherein:
Δcx> 0.005
Δcy> 0.005   The correction unit is configured to bring the chromaticity of light from the light source emitted from the emission surface closer to the target chromaticity when the chromaticity of light from the light source deviates from the target chromaticity. The illumination device according to claim 1 or 2. A light source;
A light guide unit including at least a light guide including an incident surface on which light from the light source is incident and an exit surface from which light from the light source is emitted;
A lighting device comprising:
When the chromaticity difference on the chromaticity coordinates of the CIExy chromaticity diagram between the chromaticity of the light from the light source and the chromaticity of the light from the light source emitted from the emission surface is represented by Δcx and Δcy, An illumination device characterized by satisfying a condition.
Δcx> 0.005
Δcy> 0.005 The light guide and the exit surface are elongated in a first direction;
The incident surface is an end surface in the first direction;
The light guide has a deflection surface that emits a light beam that is incident from the incident surface and travels in the first direction to the outside of the light guide member,
The light guide unit opposes the deflection surface to the outside of the light guide, and causes the light beam emitted from the deflection surface to the outside of the light guide to re-enter the light guide through the deflection surface. The illuminating device according to claim 1, further comprising a diffuse reflection portion that leads to the light exit surface.   The lighting device according to claim 5, wherein the correction unit is provided in at least one of the diffuse reflection part and the light guide.   The illumination device according to claim 5, wherein the diffuse reflection unit includes a plurality of diffuse reflection sheets having different hues.   The illuminating device according to claim 5 or 6, wherein the diffuse reflection section includes a painted surface made of a composite paint having different hues.   The lighting device according to claim 1, wherein the light guide body corrects chromaticity by transmittance as the correction unit. When the chromaticity difference on the chromaticity coordinates in the CIExy chromaticity diagram of the chromaticity of the light emitted from the light source that is emitted from the emission surface with respect to the target chromaticity is Δdx and Δdy, the following conditions are satisfied: The lighting device according to claim 3, wherein
−0.005 <Δdx <0.005
−0.01 <Δdy <0.01 The correction means, when the chromaticity of the light from the light source is deviated from the target chromaticity, the chromaticity of the light from the light source emitted from the emission surface is brought close to the target chromaticity,
The chromaticity difference on the chromaticity coordinates of the CIExy chromaticity diagram of the illuminance of the light source with respect to the target chromaticity is defined as dix, diy,
When the chromaticity of the diffuse reflection portion is xr, yr with reference to xb = 0.3127, yb = 0.3291 which are chromaticities in the standard illuminant D65,
The lighting apparatus according to claim 5, wherein the following expression is satisfied.
The lighting device according to any one of claims 1 to 11,
A sensor for reading an image of a document illuminated by the illumination device;
An imaging optical system for imaging a light flux from the original on the sensor;
An image reading apparatus comprising: