JP3972796B2 - Image input device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image input apparatus, for example, image input of an image input apparatus (image reader, image scanner, etc.) or an image forming apparatus (color or monochrome digital copying machine, facsimile, etc.) used by being connected to a personal computer or the like. The present invention relates to an image input device that constitutes a unit.
[0002]
[Prior art]
In an apparatus that inputs a two-dimensional image by scanning a document in one direction, an illuminating device that illuminates the document surface linearly is usually mounted to read the document image. However, it is difficult to illuminate the original surface uniformly with a conventionally known illumination device, and illumination devices aimed at solving this problem have been proposed in the following Patent Documents 1 and 2. .
[0003]
[Patent Document 1]
Japanese Patent No. 3266374
[Patent Document 2]
Japanese Patent Publication No. 61-24747
[0004]
[Problems to be solved by the invention]
The illumination device described in Patent Document 1 is configured to measure and monitor the amount of light at the center portion in the tube longitudinal direction and the end portion in the tube length direction of a fluorescent lamp (cathode tube) for light source, and to control the light amount of the fluorescent lamp. . However, it does not control the light quantity distribution in the longitudinal direction of the fluorescent lamp. Therefore, the light amount unevenness of the fluorescent lamp in the longitudinal direction of the tube is not reduced, and as a result, the unevenness of the line illumination on the document surface cannot be sufficiently reduced. Patent Document 2 proposes an illumination device in which an LED (Light Emitting Diode) array is mounted as a light source on a hand scanner for reading an information pattern. However, since only a reading optical system that detects scattered light other than direct light from the information pattern is provided, it is impossible to grasp whether the document surface is uniformly illuminated with a predetermined light amount. Therefore, when the uneven illumination on the document surface is large, there is a problem that the LED output cannot be corrected sufficiently and the original image cannot be reproduced faithfully.
[0005]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide an image input apparatus capable of reading an image of a document without unevenness by illuminating the document surface with line unevenness. It is in. For this purpose, an object of the present invention is to provide an image input apparatus having a function of detecting an illuminance distribution on a document surface with high accuracy.
[0006]
[Means for Solving the Problems]
  In order to achieve the above object, an image input device according to a first aspect of the present invention is an image input device including a document illumination device that irradiates light on a document surface in order to read an image of a document. An LED array in which a plurality of LEDs are arranged substantially linearly;Each LED is located between a plurality of LEDs in a region formed by a substantially linear array of LEDs.Receives light from the document surfaceMultipleWith photoelectric conversion elementLED driving means for independently driving the plurality of LEDs, and light amount control means for performing feedback control on the LED driving means based on an output from the photoelectric conversion element.It is characterized by doing.According to a second aspect of the present invention, there is provided the image input device according to the first aspect, wherein the photoelectric conversion element is positioned between all the LEDs.
[0007]
  First3The image input device of the invention ofIn the configuration of the first or second invention, the LED and the photoelectric conversion element are arranged on the same straight line. According to a fourth aspect of the present invention, there is provided the image input device according to the first or second aspect, wherein the plurality of LEDs are arranged in a staggered two-dimensional manner, and the two-dimensional arrangement is substantially straight. The area is configured by the line width of the arrayIt is characterized by that.
[0008]
  First5The image input device of the invention ofAn image input device including a document illumination device that irradiates light on a document surface for reading an image of a document, wherein the document illumination device includes a plurality of LED groups each including a plurality of LEDs having different emission wavelengths. The document is composed of an LED array arranged in a straight line and a plurality of photoelectric conversion elements having different wavelength sensitivities, and is positioned between the plurality of LED groups in a region formed by the substantially linear array of the LED groups. A plurality of photoelectric conversion element groups for receiving light from the surface; LED driving means for independently driving the plurality of LEDs; and feedback control for the LED driving means based on the output from the photoelectric conversion elements And a light amount control means for performing. According to a sixth aspect of the present invention, in the configuration of the fifth aspect, the photoelectric conversion element group is positioned between all the LED groups.It is characterized by doing.
[0009]
  First7The image input apparatus according to the invention is the above-mentioned first.5Or the second6In the configuration of the invention ofThe LED group and the photoelectric conversion element group are arranged on the same straight line. According to an eighth aspect of the present invention, there is provided the image input device according to the fifth or sixth aspect, wherein the plurality of LED groups are two-dimensionally arranged in a staggered manner, and the two-dimensional arrangement is substantially the same as the one described above. A linear array is formed, and the region is configured with the line width of the array.It is characterized by that.
[0010]
  First9The image input apparatus according to the invention is the above-mentioned first.Any one of 1st-8thIn the configuration of the invention,An illumination optical system that focuses the light beam emitted from the LED array in a substantially straight line and forms an image on the document surface, and collects the light beam reflected on the document surface and forms an image on the photoelectric conversion element.It is characterized by having.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an image input apparatus embodying the present invention will be described with reference to the drawings. FIG. 1 shows a configuration example of main parts of an image input apparatus according to the present invention. In FIG. 1, 1 is an LED array, 2 is an illumination optical system, 3 is a document table, 4 is a document, 4S is a document surface, 5 is a book reflecting mirror, 6 is a reading optical system, 7 is an image sensor, and 8 is image processing. 9 is an image output device, and 10 is a document illumination device. This image input device corresponds to an image input unit of an image forming apparatus (color or monochrome digital copying machine, facsimile, etc.), a single image input device (image reader, image scanner, etc.), and the like. In order to read a two-dimensional image of the document (4), the document surface (4S) is provided with a document illumination device (10) that irradiates light in a line shape, and the light reflected by the document surface (4S) is used. The two-dimensional image is read. In reading the two-dimensional image, the relative scanning of the line illumination with respect to the document surface (4S) is performed in a direction perpendicular to the LED arrangement direction.
[0012]
The document illumination device (10) includes an LED array (1), an illumination optical system (2), and the like. The LED array (1) has a configuration in which a plurality of LEDs are arranged in a substantially linear shape (perpendicular to the paper surface of FIG. 1) on the substrate (1a). A light emitting element array using elements as point light sources may be used instead of the LED array (1). }. The light emitted from the LED array (1) is collected by the illumination optical system (2) only in a direction perpendicular to the LED arrangement direction, and is substantially linear (one perpendicular to the paper surface of FIG. 1). Line shape). Then, after passing through the platen glass platen (3), a substantially linear light source image is formed on the document surface (4S). The light applied to the document surface (4S) is reflected by the document surface (4S) and then passes through the document table (3) again. Then, an image is formed on the light receiving surface of the image sensor (7) by passing through the reading optical system (6). Of the luminous flux emitted from the LED array (1), a part of the luminous flux outside the incident range with respect to the illumination optical system (2) is reflected by the book reflecting mirror (5) and applied to the document surface (4S). The book reflector (5) illuminates so that black shadows do not occur at the point where the document (4) is lifted from the document table (3) when the document (4) is in the form of a booklet or book. It is a mirror.
[0013]
The optical image formed by the reading optical system (6) is converted into an electrical signal by the image sensor (7). As the image sensor (7), for example, a solid-state image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) sensor composed of a plurality of pixels is used. The signal generated by the image sensor (7) is subjected to predetermined digital image processing, image compression processing, and the like in an image processing device (8) such as a personal computer. Then, it is recorded as a digital video signal in a memory (semiconductor memory, optical disk, etc.), or in some cases via a cable or converted into an infrared signal, and then transmitted to an image output device (9) such as a printer or other equipment. Is done. Therefore, an image forming apparatus such as a digital copying machine or a facsimile is constituted by a combination of the above-described image input apparatus and an image output apparatus (9) or the like (printer or the like) that outputs an image input by the image input apparatus. The
[0014]
Here, the LED array (1) will be described in more detail with specific examples. FIGS. 2 (i) to (iv) show four types of LED arrays (1) each composed of LEDs (1t) having the same light emission color. These LED arrays (1) are formed by arranging a plurality of LEDs (1t) in a substantially straight line, and within the region (Δ) formed by the substantially linear array of LEDs (1t), A photodiode (1p) that receives the reflected light from (4S) is arranged. The emission wavelengths of the LEDs (1t) are all the same (for example, white light emission), and the wavelength sensitivities of the photodiodes (1p) are all the same corresponding to the LEDs (1t). Of course, a photoelectric conversion element other than the photodiode (1p) may be used.
[0015]
FIGS. 2 (v) to (viii) show four types of LED arrays (1) each comprising three types of LEDs (R, G, B) having different emission wavelengths. These LED arrays (1) are formed by arranging a plurality of LED groups (1u) in a substantially straight line, and each LED group (1u) consists of a red LED (R), a green LED (G) and a blue LED. The LED (B) is arranged adjacent to each other. A photodiode group (1q) that receives reflected light from the document surface (4S) is disposed in a region (Δ) in which the LED group (1u) is substantially linearly arranged. The photodiode group (1q) is composed of two or three photodiodes (r, g, b) having different wavelength sensitivities, where r is a red photodiode, g is a green photodiode, and b is a blue photodiode. It is a diode. Of course, a photoelectric conversion element group other than the photodiode group (1q) may be used.
[0016]
In the LED array (1) shown in FIG. 2 (i, ii, v to vii), a plurality of LEDs (1t) or LED groups (1u) are arranged on the same straight line, whereas FIG. In the LED array (1) shown in iv, viii), a plurality of LEDs (1t) or LED groups (1u) are two-dimensionally arranged in a zigzag pattern. When the LEDs (1t) or the LED groups (1u) are two-dimensionally arranged as described above, a larger amount of light can be obtained. If each LED (1t) or LED group (1u) has a small light emitting area, even if the arrangement is two-dimensional, the line width of the arrangement (that is, the arrangement of the LED (1t) or LED group (1u)) If the area Δ) formed in the direction perpendicular to the direction is within a few mm to a few tens of mm, it is acceptable for line illumination on the document surface (4S). Therefore, the LED array (1) shown in FIG. 2 can be regarded as a plurality of LEDs (1t) or LED groups (1u) arranged almost linearly. Since the photodiode (1p) or photodiode group (1q) is arranged in the region (Δ) formed by the arrangement, the LED (1t) or LED group (1u) and the photodiode (1p) or photodiode It can be said that the diode group (1q) is located on substantially the same straight line.
[0017]
The reflected light from the document surface (4S) received by the photodiode (1p) or the photodiode group (1q) is illumination optics among the light reflected from the document surface (4S) as shown in FIG. The light reenters the system (2) and returns to the LED array (1). In other words, the illumination optical system (2) not only acts to focus the light beam emitted from the LED array (1) in a substantially straight line and form an image on the document surface (4S), but also to the document surface (4S). It also acts to collect the light beam reflected by the light and form an image on the photodiode (1p) or the photodiode group (1q). In the original illumination device (10), light incident on the photodiode (1p) or the photodiode group (1q) among the light returned to the LED array (1) causes uneven illumination on the original surface (4S). Effectively used to control the amount of light to be reduced.
[0018]
FIG. 3 shows a configuration example of the light amount control of the document illumination device (10). In FIG. 3, reference numeral 20 denotes LED driving means for independently driving a plurality of LEDs (1t) or LED groups (1u). Further, 30 is a light amount control means for performing feedback control on the LED driving means (20) based on the output from the photodiode (1p) or the photodiode group (1q), and 31 is the photodiode (1p) or the photodiode group. It is a light quantity detection part which detects the output signal from (1q). Since the light source used in the document illuminating device (10) is an LED array (1) having a configuration in which a plurality of LEDs (1t) or LED groups (1u) are arranged substantially linearly, a conventional fluorescent tube Unlike the halogen lamp, the light amount distribution in the longitudinal direction (that is, the arrangement direction) is not fixed. In other words, it is possible to control the light amount distribution in the longitudinal direction by individually controlling the light amount of the LED (1t) or the LED group (1u), and the individual deterioration of the LED (1t) or the LED group (1u). (For example, a change in the amount of light accompanying an environmental change such as a temperature change) can also be handled.
[0019]
As described above, the LED (1t) or LED group (1u) and the photodiode (1p) or photodiode group (1q) are located on substantially the same straight line. Therefore, the reflected light from the document surface (4S) is efficiently captured by the photodiode (1p) or the photodiode group (1q), and the illuminance distribution on the document surface (4S) (that is, unevenness of line illumination) is high. It can be detected with accuracy. Based on the detection result, the light quantity control means (30) is digital or analog to each LED drive means (20) so that the individual light quantity of the LED (1t) or the LED group (1u) becomes a predetermined size. Feedback control in real time. Since the control is based on the reflected light from the original surface (4S), the original surface (4S) can be line-illuminated evenly by direct compensation control regarding the light amount distribution of the illumination light. As a result, the original image can be faithfully reproduced by reading the image of the document (4) evenly. Since the necessity of correcting image degradation due to illumination unevenness on the document surface (4S) by the image processing device (8, FIG. 1) is reduced, the reproducibility of the original image is further improved. Further, if the original illumination device (10) is used, it is possible to cope with a device in which it is difficult to reset the illumination light amount for each color, for example, a digital copying machine that is required to automatically perform color reproduction according to the original. it can. Furthermore, the LED array (1) and its control configuration can be applied to a highly discrete LED (1t) arrangement described later (FIG. 4 and the like), and the technology can be continuously applied in the future. is there.
[0020]
Fluorescent tubes (cathode tubes) and halogen lamps that have been used as light sources in the past are made of glass tubes, so a large space is required to place a photoelectric conversion element such as a photodiode nearby. become. In the document illuminating device (10), the photodiode (1p) or the photodiode group (1q) is disposed between the LED (1t) or the LED group (1u). Space saving can contribute to downsizing of the apparatus. Further, as a condensing optical system for guiding the reflected light from the document surface (4S) to the photodiode (1p) or the photodiode group (1q), an illumination optical system (2 for guiding the light to the document surface (4S)). ), The reflected light from the document surface (4S) can be captured without adding an extra condensing optical system. Therefore, it is economical and it is not necessary to secure an extra space. Also, the directional conjugate relationship between the document surface (4S) and the LED array (1) makes it possible to simultaneously achieve illumination and detection of the document surface (4S) with high accuracy.
[0021]
In the light quantity control configuration shown in FIG. 3, the detection result of each photodiode (1p) or each photodiode group (1q) is reflected in the control for the two closest LEDs (1t) or LED group (1u). However, the present invention is not limited to this. Each LED (1t) or each LED group (1u) may be controlled by comprehensive judgment based on the detection results of the plurality of photodiodes (1p) or photodiode groups (1q). Also, even if the LED array (1) has uneven light quantity, it is sufficient that the document surface (4S) is line-illuminated without unevenness, so the light quantities of all LEDs (1t) or LED groups (1u) are made the same size. There is no need.
[0022]
The photodiode (1p) or the photodiode group (1q) may be disposed between all the LEDs (1t) or the LED group (1u) as shown in FIG. 2 (i, iii, v to viii), As shown in FIG. 2 (ii, iv), a thinned arrangement may be used. A form corresponding to the performance of the illumination optical system (2) and the required illumination distribution accuracy may be adopted. Further, as shown in FIG. 2 (vi), a part of the photodiode group (1q) may be thinned out. However, as shown in Fig. 2 (v, vii, viii), it is better to correct the color shift by making the combination of the emission wavelength of the LED group (1u) and the combination of the wavelength sensitivity of the photodiode group (1q) the same. In addition, it is preferable for performing light amount control with high accuracy.
[0023]
Here, the relationship between the LED array interval of the LED array (1) and the line illumination unevenness on the document surface (4S) will be described with reference to FIG. In FIG. 4, P is the LED array interval, L is the distance from the LED array (1) to the document surface (4S), Q is the illuminance distribution on the document surface (4S), and the illumination optical system (2) and photo The diode (1p) and the like are not shown. In the general LED array (1), as shown in FIG. 4 (A), a plurality of LEDs (1t) are arranged almost linearly on the substrate (1a) with almost no gap. For this reason, even if the distance (L) from the LED array (1) to the document surface (4S) is short, the illumination unevenness generated on the document surface (4S) is small. However, if the output light quantity of the LED (1t) alone increases drastically in the future (for example, 1.5 times or more than the current level), the necessary number of LEDs (1t) will decrease, and it will be necessary to thin out the LEDs (1t). As a result, a large illumination unevenness occurs due to the discrete arrangement (for example, P ≧ 6.35 mm) of the LEDs (1t) having a large output light amount. That is, as the output light quantity of the LED (1t) alone increases and the LED array interval (P) increases, the illumination unevenness increases as shown in FIG. 4B, and the light intensity unevenness control of the LED (1t) is performed. Then, it becomes difficult to correct. If the distance (L) from the LED array (1) to the document surface (4S) is increased, the illumination unevenness can be reduced, but the document illumination device (10) is increased in size.
[0024]
Therefore, in the present embodiment, as shown in FIG. 4C, a diffusion having a function of diffusing a light beam in the arrangement direction of the LED (1t) between the LED array (1) and the document surface (4S). An optical element (D) is arranged. The diffusing optical element (D) is provided as a part of the illumination optical system (2, FIG. 1), and is configured, for example, by processing a lens surface or a mirror surface. Due to the diffusing function of the diffusing optical element (D), unevenness in the amount of light emitted from the line illumination of the document illumination device (10) can be suppressed, and uneven illumination generated on the document surface (4S) can be reduced. In addition, it is possible to reduce illumination unevenness while the distance (L) from the LED array (1) to the document surface (4S) remains the same as in the conventional case. Accordingly, it is possible to simultaneously achieve downsizing of the document illumination device (10) and suppression of unevenness in the amount of light. Economical effects such as cost reduction and energy saving by reducing the number of LEDs (1t) can be obtained. In addition, whether the LED array (1) is composed of LEDs (1t) having the same emission color or a combination of LEDs (1t) having different emission colors, the effects obtained by the diffusion optical element (D) described above can be obtained. There is no change.
[0025]
As described above, the illumination optical system (2) has a function of condensing a light beam in a direction perpendicular to the arrangement direction of the LEDs (1t). That is, the illumination optical system (2) is composed of lenses, mirrors, and the like that have unidirectional convergence in the direction perpendicular to the arrangement direction of the LEDs (1t). The diffusing function of the diffusing optical element (D) also has the same directionality as the light condensing function in the arrangement direction of the LEDs (1t). Therefore, examples of the diffusion optical element (D) include a minute lens group having a plurality of lens surfaces having a divergence function by refraction (such as a substantially cylindrical curved surface), a reflection surface having a divergence function by reflection (substantially a cylinder shape). And the like, a micromirror group having a plurality of diffraction gratings having a divergence function due to unidirectional diffraction, and a chamfer surface having a unidirectional scattering function.
[0026]
Also, considering the effectiveness of diffusion in the optical path from the LED array (1) to the document surface (4S), the diffusion optical element (D) to be used is selected according to the diffusion position in the illumination optical system (2) It is preferable to do this. For example, in the case where the diffusing function is provided in the portion close to the LED array (1) in the illumination optical system (2), a curved surface, a diffraction grating, etc. corresponding to each LED (1t) are arranged as the diffusing optical element (D). It is desirable to do. In the case where the above-mentioned diffusion function is provided in a part away from the LED array (1) in the illumination optical system (2), an optical surface (condenser lens surface, condenser mirror surface, etc.) that covers all LEDs (1t) It is desirable to arrange a slit surface or the like having a scattering function as the diffusion optical element (D).
[0027]
The optical configuration of the document illumination device (10) will be described in more detail below with a specific example. FIGS. 5 and 6 show an LED array (1) in which a plurality of LEDs (1t) are arranged in a substantially straight line with an arrangement interval of 6.35 mm (1/4 inch) or more, and from the document surface (4S). A module-type document illumination device (10) having a photodiode (1p) that receives light and an illumination optical system (2) that guides a light beam emitted from the LED array (1) to the document surface (4S), respectively. Show. 5 and 6, (A) is a cross-sectional view in a plane perpendicular to the arrangement direction of the LEDs (1t), and (B) is a plane in parallel to the arrangement direction of the LEDs (1t). It is sectional drawing. Further, (A) and (B) show cross-sectional structures orthogonal to each other, and the cross-sectional directions shown in FIGS. 5 (A) and 6 (A) correspond to the cross-sectional direction shown in FIG. In the illumination optical system (2) shown in FIGS. 5 and 6, the LED array (1) and the photodiode group (1q) composed of the plurality of LED groups (1u) described above can also be applied.
[0028]
Each of the illumination optical systems (2) shown in FIGS. 5 and 6 includes a pair of achromatic condensing lenses (G1, G2), and has a function of diffusing a light beam in the arrangement direction of the LEDs (1t). And a function of condensing the light beam in a direction perpendicular to the arrangement direction of the LEDs (1t). As shown in FIG. 5 (A) and FIG. 6 (A), the light beam is condensed with the first lens (G1) having a negative power in the direction perpendicular to the arrangement direction of the LEDs (1t) and the positive power. The second lens (G2) having an achromatic effect is obtained by a combination of negative and positive. On the other hand, the light beam is diffused by the first lens (G1) having different diffusing action in FIG. 5 (B) and FIG. 6 (B) as described below.
[0029]
In the illumination optical system (2) shown in FIG. 5, as shown in FIG. 5 (B), the first lens (G1) has the same number of minute concave lens surfaces corresponding to the LEDs (1t) on the LED array (1) side. The second lens (G2) has a positive power lens surface formed of a free-form surface on the side of the document surface (4S). The luminous flux emitted from each LED (1t) diverges on each concave lens surface of the first lens (G1) and spreads in the array direction of the LED (1t), and then the condenser function of the free curved surface of the second lens (G2) As a result, the light is condensed toward the center of the LED array (1). The light beam emitted from the end of the LED array (1) has a spread toward the outside of the document surface (4S) due to the negative power of the first lens (G1). ) Is provided by a free-form capacitor function. Therefore, it is possible to prevent the amount of light from being wasted. As a result, the light beam emitted from the illumination optical system (2) illuminates the original surface (4S) evenly while being diffused in the arrangement direction of the LEDs (1t).
[0030]
Here, a minute lens group of negative power composed of a plurality of concave surfaces is used as the diffusing optical element (D), whereby the light beam is diffused in the arrangement direction of the LEDs (1t), but this corresponds to each LED (1t). The configuration for diverging the light beam using the refracting surface is not limited to this. For example, the light beam may be diffused in the arrangement direction of the LEDs (1t) by the divergence after the image is once formed by a positive power minute lens group composed of a plurality of convex lens surfaces. The convex or concave lens surface shape (cylinder shape, spherical shape, aspherical shape, etc.) constituting the minute lens group may be set according to the relationship with the light collecting function or the like.
[0031]
In the illumination optical system (2) shown in FIG. 6, as shown in FIG. 6 (B), the first lens (G1) has a minute (unidirectional) diffraction grating corresponding to the LED (1t) in the same number. The second lens (G2) has a positive power lens surface having a free-form surface on the document surface (4S) side. The second lens (G2) is the same as the illumination optical system (2) shown in FIG. 5, and the condenser function prevents the amount of light from being wasted. The luminous flux emitted from each LED (1t) diverges at each diffraction grating of the first lens (G1) and spreads in the array direction of the LED (1t), and then the condenser function of the free curved surface of the second lens (G2) As a result, the light is condensed toward the center of the LED array (1). As a result, the light beam emitted from the illumination optical system (2) illuminates the original surface (4S) evenly while being diffused in the arrangement direction of the LEDs (1t).
[0032]
Here, a negative power micro-diffraction grating group consisting of a plurality of diffraction gratings is used as the diffusion optical element (D), thereby diffusing the luminous flux in the arrangement direction of the LEDs (1t). The configuration for diverging the light beam using the corresponding diffraction grating is not limited to this. For example, the light beam may be diffused in the array direction of the LEDs (1t) by divergence after once imaged by a plurality of positive power micro diffraction grating groups. Further, it is preferable that the period of the diffraction grating is not constant. This is because the use of a diffraction grating having a random period can effectively improve the color image reading reproducibility by the achromatic action. The free curved surface of the second lens (G2) may be designed so as to function as a concave lens as a whole (in a set of two lenses). Further, a unidirectional diffraction grating with a random period may be added to the entire surface of the free-form surface as a diffusion optical element (D).
[0033]
Next, the document illumination device (10) having a reflecting surface in the illumination optical system (2) will be described. 7A to 7C, an LED array (1) in which a plurality of LEDs (1t) are arranged in a substantially straight line with an arrangement interval of 6.35 mm (1/4 inch) or more, and an original surface ( 4S) 3 types of original illumination including the photodiode (1p) that receives the light from the LED array (1) and an illumination optical system (2) that guides the luminous flux emitted from the LED array (1) to the original surface (4S) Each device (10) is shown. In FIG. 7, the portion from the document illumination device (10) to the document surface (4S) in the image input device shown in FIG. 1 is embodied and shown in a cross section in a plane perpendicular to the arrangement direction of the LEDs (1t). Yes. Also, the book reflector (5), photodiode (1p), etc. described above are not shown. In the illumination optical system (2) shown in FIG. 7, the LED array (1) and the photodiode group (1q) composed of the plurality of LED groups (1u) described above can also be applied.
[0034]
The illumination optical system (2) shown in FIG. 7 (A) consists of one mirror (M0), and the illumination optical system (2) shown in FIG. 7 (B) consists of two mirrors (M1, M2). The illumination optical system (2) shown in FIG. 7C is composed of two mirrors (M1, M2) and one lens (G0). 5 and 6 each have a function of diffusing a light beam in the arrangement direction of the LED (1t) and a function of condensing the light beam in a direction perpendicular to the arrangement direction of the LED (1t). The same effects as the illumination optical system (2) are achieved. Condensing the luminous flux is performed by positive power in a direction perpendicular to the arrangement direction of the LEDs (1t). For example, in the illumination optical system (2) of FIG. 7 (A), the light is condensed by the positive power of the mirror (M0), and in the illumination optical system (2) of FIG. 7 (B), the first and second mirrors (M1). , M2) and the light is condensed by the positive power of the lens (G0) and the first and second mirrors (M1, M2) in the illumination optical system (2) of FIG. Is called.
[0035]
On the other hand, the diffusion of the light beam is performed by the diffusion optical element {D, FIG. 4 (C)} added to any surface of the illumination optical system (2). For example, a negative power minute mirror group composed of a plurality of minute convex reflecting surfaces (corresponding to the minute lens group in FIG. 5B). }, A negative power micro diffraction grating group consisting of a plurality of micro diffraction gratings {corresponding to the micro diffraction grating group in FIG. 6B}, etc., is a positive power capacitor reflecting surface {FIG. 5B or FIG. (B) corresponds to a positive-power condenser lens surface consisting of a free-form surface} and the like. In the case of the illumination optical system (2) in FIG. 7A, a mirror (M0) having a composite reflecting surface of a minute mirror group or minute diffraction grating group and a condenser reflecting surface is used. In the case of the illumination optical system (2) shown in FIGS. 7B and 7C, a first mirror (M1) having a minute mirror group or a minute diffraction grating group on a reflecting surface is used, and a second mirror having a condenser reflecting surface ( M2) is used. In the case of the illumination optical system (2) in FIG. 7C, a lens (G0) having a minute lens group or a minute diffraction grating group on the lens surface is used, and a second mirror (M2) having a condenser reflecting surface is used. May be.
[0036]
Since the illumination optical system (2) shown in FIG. 7A is composed of one mirror (M0), the configuration is simple and the cost can be easily reduced. In the case of the illumination optical system (2) shown in FIGS. 7A and 7B, since all the optical elements are configured by mirrors (M0, M1, M2), there is an advantage that chromatic aberration does not occur. If the lens (G0) is included as in the illumination optical system (2) shown in FIG. 7 (C), the power burden on the first mirror (M1) can be reduced or eliminated, resulting in compactness. Can contribute. However, in order to suppress chromatic aberration caused by using the lens (G0), it is desirable to use a lens (G0) having low power.
[0037]
Each of the illumination optical systems (2) shown in FIGS. 7 (A) to 7 (C) is an array of LEDs (1t) on the reflecting surface of the mirrors (M0, M1, M2), and the luminous flux emitted from the LED array (1). It is configured to reflect in a direction perpendicular to the direction. When the reflecting surfaces are used in this way, the greater the number of reflecting surfaces, the higher the degree of freedom in optical arrangement, and the original illuminating device (10) can be made more compact. This is because the illumination optical system (2) shown in FIGS. 7B and 7C is shorter in the height direction than the illumination optical system (2) shown in FIG. It is clear from the fact that the entire lighting device (10) is compact. Further, by using the reflecting surface as described above, an optical arrangement in which the LED array (1) is directed horizontally downward as in each illumination optical system (2) shown in FIGS. 7 (A) to (C). It is also possible to take
[0038]
According to the configuration of the document illumination device (10) shown in FIGS. 5 to 7, even if the individual LED output light quantity increases and the number of LEDs (1t) used decreases, linear illumination light without shading can be obtained. Therefore, it is possible to illuminate the original surface (4S) evenly without changing the distance (L, FIG. 4) from the LED array (1) to the original surface (4S). Then, by using an image input device equipped with each document illumination device (10), it is possible to read the image of the document (4) without unevenness. In addition, since it is not necessary to change the distance (L) from the LED array (1) to the document surface (4S), the increase in the output light amount of each assumed LED (1t) can be used as it is. It can be directly linked to the reduction of the number. As a result, great economic effects (low cost, energy saving, etc.) can be obtained. In addition, since each illumination optical system (2) is configured by a combination of a plurality of optical elements whose optical surfaces are processed anamorphically, the number of optical elements can be minimized, which is economical. .
[0039]
The document illumination device (10) described above can be used as an illumination device or a part thereof in devices other than the image input device. For example, if the original illumination device (10) is used as a linear light source device in an illumination device using a long fluorescent tube or a long halogen lamp as a light source, uniform illumination can be performed at low cost and in a compact manner. Examples of such an illuminating device include a backlight and a front light used for a non-light-emitting display element such as an LCD (Liquid Crystal Display). Accordingly, each of the above-described embodiments includes the inventions (I) to (V) having the following configurations, and the illuminated surface can be evenly illuminated using the LED array by the configuration. A light source device can be provided.
[0040]
(I) A light source device for forming a linear light source image for illumination, comprising: an LED array in which a plurality of LEDs are arranged substantially linearly; and a photoelectric conversion element that receives light from an irradiated surface. The light source device is characterized in that the photoelectric conversion element is located in a region formed by a substantially linear array of the LEDs.
(II) A light source device for forming a linear light source image for illumination, an LED array in which a plurality of LED groups each having a plurality of LEDs having different emission wavelengths are arranged in a substantially straight line, and wavelength sensitivity And a photoelectric conversion element group configured to receive light from the irradiated surface, the photoelectric conversion element group being located in a region formed by a substantially linear array of the LED groups. A light source device characterized by the above.
(III) Further, the luminous flux emitted from the LED array is condensed almost linearly to form an image on the illuminated surface, and the luminous flux reflected from the illuminated surface is condensed on the photoelectric conversion element. The light source device according to (I) or (II), further comprising an illumination optical system that forms an image.
(IV) The light source device according to (I), (II) or (III), further comprising LED driving means for independently driving the plurality of LEDs.
(V) The light source device according to (IV), further comprising a light amount control unit that performs feedback control on the LED driving unit based on an output from the photoelectric conversion element.
[0041]
【The invention's effect】
As described above, according to the present invention, since the photoelectric conversion element is located in a region formed by a substantially linear array of LEDs or LED groups, the illuminance distribution on the document surface can be detected with high accuracy. . In addition, an illumination optical system that collects the light beam emitted from the LED array in a substantially straight line and forms an image on the original surface, and collects the light beam reflected on the original surface and forms an image on the photoelectric conversion element. The detection accuracy is improved, and the document illumination device can be reduced in size and cost. By combining the LED driving unit and the light amount control unit, it is possible to illuminate the original surface with lines without unevenness, and it is possible to realize an image input device that can read an original image without unevenness. If the image input apparatus according to the present invention is used in combination with an image output apparatus, an inexpensive and small-sized image forming apparatus (digital copying machine, facsimile, etc.) can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a configuration example of a main part of an image input apparatus according to the present invention.
FIG. 2 is a plan view showing a specific example of an LED array.
FIG. 3 is a block diagram showing a configuration example of light amount control of the document illumination device.
FIG. 4 is a diagram for explaining unevenness of line illumination by the document illumination device and its elimination.
FIG. 5 is a cross-sectional view showing a specific example of an illumination optical system having a minute lens group.
FIG. 6 is a cross-sectional view showing a specific example of an illumination optical system having a minute diffraction grating group.
FIG. 7 is a cross-sectional view of a main part showing an image input apparatus having a reflecting surface in the illumination optical system.
[Explanation of symbols]
1 ... LED array
1t LED
1u ... LED group
1p Photodiode (photoelectric conversion element)
1q… Photodiode group (photoelectric conversion element group)
R ... Red LED
G ... Green LED
B ... Blue LED
1r Red photodiode (photoelectric conversion element)
1g Green photodiode (photoelectric conversion element)
1b… Blue photodiode (photoelectric conversion element)
2 ... Illumination optics
4S ... Original side
10… Original illumination device
20 ... LED driving means
30 ... Light intensity control means
31… Light intensity detector

Claims (9)

An image input device including a document illumination device that irradiates light on a document surface in order to read an image of a document,
The document illumination device is positioned between the LED array in which a plurality of LEDs are arranged in a substantially straight line and the plurality of LEDs in a region formed by the substantially linear arrangement of the LEDs from the document surface. A plurality of photoelectric conversion elements that receive light, an LED driving unit that independently drives the plurality of LEDs, and a light amount control unit that performs feedback control on the LED driving unit based on an output from the photoelectric conversion element an image input apparatus, characterized in that the perforated when the. The image input device according to claim 1, wherein the photoelectric conversion element is positioned between all the LEDs. The image input device according to claim 1, wherein the LED and the photoelectric conversion element are arranged on the same straight line. The plurality of LEDs are two-dimensionally arranged in a staggered pattern, the two-dimensional arrangement forms the substantially linear array, and the region is configured with the line width of the array. The image input apparatus according to claim 1, wherein: An image input device including a document illumination device that irradiates light on a document surface in order to read an image of a document,
The document illumination apparatus, the LED array substantially formed by linearly arranged a plurality of LED groups of different plurality of LED emission wavelengths consists different plurality of photoelectric conversion elements having wavelength sensitivity, the LED group And a plurality of photoelectric conversion element groups for receiving light from the original surface respectively positioned between a plurality of LED groups in a region formed by a substantially linear array, and the plurality of LEDs are independently driven. a LED driving unit, an image input apparatus characterized by chromatic and a light amount control means for performing on the basis of feedback control on an output from the photoelectric conversion element with respect to the LED driving unit. The image input device according to claim 5, wherein the photoelectric conversion element group is located between all the LED groups. The image input device according to claim 5, wherein the LED group and the photoelectric conversion element group are arranged on the same straight line. The plurality of LED groups are two-dimensionally arranged in a staggered manner, and the two-dimensional arrangement forms the substantially linear array, and the region is configured by the line width of the array. The image input apparatus according to claim 5 or 6, wherein Further, illumination optics for condensing the light beam emitted from the LED array in a substantially straight line to form an image on the original surface and condensing the light beam reflected on the original surface to form an image on the photoelectric conversion element. the image input device according to any one of claims 1-8, characterized in that it comprises a system.

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