JPH11261763A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader using a compound eye lens which is small in size, high in read accuracy and reduced in the blurring of a formed image due to a floated original. SOLUTION: In this image reader provided with a lighting means 25 that emits a light to an original face 29, a light collection means 26 that forms an image of a reflected light from the original face 29 receiving the light emitted from the means 25, and a light receiving means 24 that receives the light of the formed image and applies photoelectric conversion to the light, the light collection means 26 is configured by arranged plural lenses 36a, 36b whose focal distance differs from each other and having at least two kinds of focal distances. Thus, a fog of an image formed on the light receiving section due to a floated original is reduced without lighting an aperture angle and then the reader with a small size and high read precision is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for reading an image of an original or the like as an input device of a computer, a facsimile, a copying machine, or the like.

[0002]

2. Description of the Related Art An image reading device is used as an image input device.
It has excellent operability and versatility, and is widely used in recent years in the fields of OA equipment, information equipment, and the like. The image reading devices used in these devices are classified into a reduced image forming optical system method and an equal-magnification image forming optical system method (or close contact type), depending on the structure of the optical system.
The reduced image forming optical system is configured as shown in FIG. 15, for example, and irradiates an original 129 with a linear light source 105 such as a fluorescent lamp to reduce reflected light on a read line L of the original 129. The image is formed on the CCD 101 via the lens 106 and the image data of the document surface is read.
This method has the disadvantages that the cost of parts is low and the depth of focus is deep, but it is difficult to reduce the size, it takes time and labor to assemble and assemble, and there is a large blur at the periphery of the image. On the other hand, the contact type is easy to miniaturize, and in recent years, the demand for home-use facsimile machines, small copiers and the like has been increased. 2. Description of the Related Art (1: 1 imaging optical system) image reading apparatuses are becoming widespread. FIG. 16 is a cross-sectional view of such a conventional contact-type image reading apparatus described in, for example, JP-A-6-342131, and its outline will be described.

The image reading dense device shown in FIG. 16 is an original reading light receiving element 12 in which a plurality of sensor pixels for performing photoelectric conversion are arranged.
1, a light-receiving element array 124 including a protective film 122 and a substrate 123 on which the protective film 122 is mounted, and an LED array 125 including a plurality of light-emitting diodes (hereinafter, referred to as LEDs) that are linear light sources for irradiating a document. A lens array 126 for forming an image of the document 129 on the light receiving element array 124 serving as a light receiving portion, and a transparent plate 12 on which the document 129 is placed.
7 and an outer case 128 supporting these members.

[0004] The operation of the above image reading apparatus uses an LED.
The original surface is illuminated by the array 125, and the diffuse reflected light on the reading line of the original surface is imaged on the light receiving element array 124 by the lens array 126, and the density information of the original 129 which the reflected light has, that is, the intensity of light To the light receiving element array 1
The sensor pixels of the individual document reading light receiving elements 121 in 24 convert the signals into electric signals and send out the signals as serial or parallel signal outputs for each reading line. Then, the relative position between the original 129 and the sensor pixel row is moved in a direction perpendicular to the line, and the data transmission for each line is repeated, thereby converting the two-dimensional image information into a time-series electric signal.

However, the above-mentioned contact type image reading apparatus has the following problems. The lens array 126
Is a compound eye lens composed of a plurality of individually condensing rod lenses arranged in the direction perpendicular to the drawing, which causes images to overlap on the light receiving side and increases the synthetic aperture angle. There is a problem that the image quality is deteriorated when the depth of field is shallow, and the original is broken or the original has irregularities such as cut and paste. In addition, it is not possible to read a double-page spread or the like of a book, and the use of such an image reading apparatus has been limited.

The state of image formation in the lens array 126 using the rod lens will be described with reference to FIG.
A lens array 126 shown in FIG.
a are aligned in the line direction, and each rod lens 1
Reference numeral 26a is made of a light transmitting material having a refractive index distribution in a direction perpendicular to the optical axis. Each rod lens 126a is shown in FIG.
As shown in FIG. 7A, a range of the diameter X0 on the original surface is imaged on a sensor surface on which the sensor pixels are arranged, at an equal magnification of an erect image. Consider a certain light emitting point p and its imaging q. When p is at the reference position, it is assumed that the light converging point is just on the sensor surface, and that no blur occurs in the image q. As shown in FIG. 17B, when the light emitting point p moves by x to p ′, the light converging point also moves by x behind the sensor surface, and the image q on the sensor surface causes a blur of H amount. . When the rod lens 126a is used alone, the amount H of blur is substantially H = {x, and depends on the aperture angle Θ. When a plurality of rod lenses 126a are arranged as shown in FIG. 17C, the opening angle becomes Θ 'which is larger than 、, the amount of blur becomes H' which is larger than H, and substantially H '= Θ'x Becomes And rod lens 12
As the number of arrays 6a increases, the aperture angle increases due to the overlap of the imaging ranges X0, and the blur increases. Thus, there has been a problem that the aperture angle is wide, the relative depth of field is shallow, and the ratio of the amount of blurring of the image q to the movement of the light emitting point p is large.

If an attempt is made to reduce the aperture angle 小 さ く of each rod lens in order to eliminate such a defect, the optical path length from p to q becomes long. Invites upsizing. Further, if a large number of rod lenses having a small diameter are used to reduce the opening angle Θ, such a rod lens itself becomes expensive.
A contact-type image reading apparatus shown in FIG. 18 improved for the purpose of improving these disadvantages is disclosed in Japanese Patent Application Laid-Open No. 6-342.
No. 131 is described. In FIG. 18, 11
Reference numeral 0 denotes an aperture limiting member, and each of the rod lenses 12
6a, it is arranged on the emission side. The other points are the same as those of the image reading apparatus shown in FIG. In the present example, the aperture limiting member 110 limits the aperture angles of the individual rod lenses 126a, limits the overlap of images between the rod lenses, and reduces the amount of blur.

However, in this case, the positional relationship of the aperture limiting member 110 must be precisely adjusted for each rod lens 126a, which is disadvantageous in terms of assemblability.
In addition, the amount of light passing therethrough is limited by the aperture limiting member 110, the intensity of light incident on the light receiving element array 124 is weakened, the S / N ratio in photoelectric conversion is reduced, and the noise of the generated signal tends to increase. .

According to the present invention, when the above-mentioned problems in the conventional image reading apparatus, that is, when an equal-magnification imaging method using a compound eye lens is adopted in order to reduce the size of the apparatus, the aperture angle is generally wide. The problem that the depth of field is shallow, the problem of using a rod lens with a large depth of field in an attempt to improve this problem leads to an increase in the size of the device and an increase in component costs, and the use of an aperture limiting member for the rod lens. If provided, it is disadvantageous in assembling, and it is an object to solve the problem of increasing the signal noise of the light receiving element. And
An object of the present invention is to solve these problems and provide an image reading apparatus that can cope with various types of originals such as bent, uneven, spread, and can accurately read an image of the original, and is easy to assemble. .

[0010]

According to one aspect of the present invention, there is provided a lighting device for irradiating a document surface, a condensing device for forming an image of the reflected light from the irradiated document surface, In an image reading apparatus provided with a light receiving means for receiving the formed light and performing photoelectric conversion, the light condensing means is configured by arranging a plurality of lenses having at least two kinds of focal lengths having different focal lengths from each other. It is characterized by that.

According to a second aspect of the present invention, there is provided the first means, wherein the plurality of lenses are arranged so that the respective focal points coincide substantially on the same plane in the light receiving means. It is characterized by being.

As a third means for solving the above-mentioned problems, the present invention relates to the first means or the second means,
Lenses having different focal lengths in the light condensing means are rod lenses whose refractive index changes in a direction perpendicular to the optical axis,
It is characterized by being arranged at positions shifted from each other in the optical axis direction.

According to a fourth aspect of the present invention, there is provided the light condensing means according to any one of the first to third means, wherein the lenses are arranged in a plurality of rows so as to focus on each other. It is characterized in that lenses having different distances are arranged in different rows.

According to a fifth aspect of the present invention, there is provided the light condensing means according to any one of the first to fourth means, wherein adjacent lenses have different focal lengths. It is characterized in that the lenses are arranged to be lenses.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment which is one of the preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of a contact-type image reading apparatus according to the present embodiment, and FIG. 2 is a cross-sectional view taken along line AA of FIG. FIG.
As shown in FIG. 1, the contact-type image reading apparatus of the present embodiment has a document reading light receiving element 2 in which a plurality of sensor pixels for performing photoelectric conversion are arranged.
1, a light-receiving element array 24 composed of a protective film 22, and a substrate 23 on which the protective film 22 is mounted, an LED array 25 that is a linear light source for irradiating a document, and the light-receiving element that is a light receiving unit for transmitting an image of the document 29. Lens array 2 that forms an image on array 24
6, the supporting frame 37 holding the lens array 26 and the original 2
9 comprises a transparent plate 27 on which the components 9 are placed, and an outer case 28 for supporting these members.

The operation of the contact type image reading apparatus is as follows. The document surface is illuminated by the LED array 25, and the diffuse reflected light on the reading line of the document surface is transmitted to the lens array 26.
An image is formed on the light receiving element array 24 by the light receiving element array 24, and the density information of the original 29 which the reflected light has, that is, the intensity of light, is
The sensor pixels of the individual document reading light receiving elements 21 in 4 convert the signals into electric signals, and send out the signals as serial or parallel signal outputs for each reading line. Then, by moving the relative position between the original 29 and the sensor pixel row in the direction perpendicular to the line and repeating the data transmission for each line, the two-dimensional image information is converted into a time-series electric signal.

As shown in FIGS. 1 and 2, the lens array 26 has two types of rod lenses having different focal lengths TC in a direction parallel to the reading line on the original surface, that is, a first rod lens 36a and a second rod lens. 36b are alternately arranged, and are held by the holding frame 37.

The first rod lens 36a and the second rod lens 36b are both made of a light transmitting material having a refractive index distribution in a direction perpendicular to the optical axis, similarly to the conventional rod lens 126a shown in FIG. Thus, there is a relationship TC1 <TC2 between the focal length TC1 of the first rod lens 36a and the focal length TC2 of the second rod lens 36b. S
Reference numeral denotes a sensor surface of the light receiving element array 24 on which the document reading light receiving element 21 is arranged. As shown in FIG.
The first focal plane Sa where the focal point A1 on the transparent plate 27 side of the rod lens 36a is located is offset dc = TC2-TC1 from the second focal plane Sba where the focal point A2 on the transparent plate 27 side of the second rod lens 36b is located. , The focal point B1 of the first rod lens 36a on the light receiving element array 24 side and the light receiving element array 2 of the second rod lens 36b.
The first rod lens 36a and the second rod lens 36b such that the focal point B2 on the fourth side is located on the sensor surface S.
Are also shifted from each other in the optical axis direction. In FIG. 2, the display of the transparent plate 27 and the original 29 shown in FIG. 1 is omitted, but the upper surface of the transparent plate 27 is the first focal plane S.
It is arranged so as to be in the vicinity of a.

By the way, regarding the rod lens used in the present embodiment, light emitted from one point on one focal plane is located at an erect symmetrical position on the other focal plane separated by a focal distance (TC). Focus on one point. However, when the light emitting point is far from the focal plane, the light is generally not always condensed at an equal-length erect position. This is because it is considered that a unique focal length (TC) or a focal point cannot be specified in the first place if the light-emitting point is always converged to a position of the same magnification erect even if it is away from the focal plane. It is. Regarding the light condensing action when the light emitting point is far from the focal plane, two cases have conventionally been considered depending on the distribution or size of the refractive index of the rod lens. The first case is a case where light is condensed on a point that is located at an erect non-equivalent (reduced or enlarged) position with respect to the light emitting point. In the second case, if the light emitting point is not far from the focal plane, the light is condensed at a point approximately at the same magnification erect with respect to the light emitting point.
Hereinafter, the light collecting action in the present example will be sequentially described assuming the first case and the second case.

FIG. 3 is a sectional view showing the principle of the light-collecting action of the image reading apparatus of the present embodiment when light-collection in the first case is assumed. (A) is a cross-sectional view parallel to the line direction (the arrangement direction of the rod lenses) showing the entirety, (b) is a detailed view of a portion B in (a), and (c) is a view taken along CC in (b). It is. For convenience of explanation, the light condensing action of one first rod lens 36a and one second rod lens 36b adjacent to each other will be described. When the light-emitting point A01 is located on the first focal plane Sa, of the light emitted, the light ray that has entered the first rod lens 36a is the first light that is in the same-length erect position with respect to the first rod lens 36 as the output light s1. The light is condensed on a condensing point B01. Here, B01 coincides with the sensor surface S. On the other hand, of the light emitted from the light emitting point A01, the light incident on the second rod lens 36b is emitted as the emitted light s2, but is not condensed at one point on the sensor surface S, and the offset amount of the focal plane as described later. This produces an image having a blur in the range of approximately proportional to dc. In other words, the light s2 passing through the second rod lens 36b is substantially equal to the second condensing point B02 at the erect position substantially dc behind the sensor surface S.
And is incident on the sensor surface S.

The opening angle of the first rod lens 36a viewed from the focal point A1 is Θ1, and the second rod lens 36b is viewed from the focal point A2.
開口 2 is the opening angle when viewing. The image formed on the sensor surface S by the light s1 emitted from the first rod lens 36a is q1,
Assuming that the image formed on the sensor surface S by the light s2 emitted from the second rod lens 36b is q2, as shown in FIGS. 3B and 3C, q1 and q2 are generated at positions where a part thereof overlaps. , Q1 is H1 = 0, and the blur H2 of q2 is approximately H2 = Θ2 · dc.

FIGS. 4A and 4B are diagrams showing the relationship between the movement of the light emitting point and the blur, wherein FIG. 4A is a cross-sectional view showing the entirety, FIG. 4B is an enlarged view of a portion D in FIG. b) EE
It is an arrow view. As shown in FIG. 4 (a), the light emitting point A01 is located at the first focal plane Sa, and is located at x0 ahead of the original position by x.
When moving to the point 1 ', the first focal point B01 moves to the point B01' ahead of the original position by x and the second focal point B02.
Moves to the point B02 'forward by x from the original position, and
The absolute values of the distance of 01 ′ and B02 ′ from the sensor surface S are | x | and | dc−x |, respectively. At this time, the blur amount H1 of the image q1 due to the light passing through the first rod lens 36a is substantially H1 = {1 | x |, and the blur amount H2 of the image q2 due to the light passing through the second rod lens 36b is approximately H2 = {2 | dc-x |

Next, assuming that the light is condensed in the second case, a case in which incident light from a light emitting point outside the focal plane is also condensed to an approximately equal-length erect position with respect to the rod lens is shown in FIG. It is shown in FIG. Of the light emitted from the point A01 ', which is x in front of the first focal plane Sa, the light ray incident on the first rod lens 36a is condensed as the outgoing light s11 at the first condensing point B011 behind x of the sensor surface S. Out in the direction of On the other hand, A0
Of the light emitted from the point 1 ', the light incident on the second rod lens 36b is dc-x from the sensor surface S as outgoing light s12.
The light is emitted in a direction in which the light is condensed at a second light condensing point B012 just ahead (when x> dc, it is only x-dc backward). At this time, the amount of blur H1 of the image q1 due to the light s11 passing through the first rod lens 36a is substantially H1 = {1 | x |, and the amount of blur H2 of the image q2 due to the light s12 passing through the second rod lens 36b is Approximately, H2 = {2 | dc-x | Therefore, in the case of the light condensing function shown in FIG. 4 and the case of the light condensing function shown in FIG. 5, the same result is obtained as to the relationship between the movement of the light emitting point and the blur of the image.

FIG. 6 shows the movement amount x of the light emitting point A0 from the reference position and the image q1 formed by the light passing through the first rod lens 36a.
FIG. 9 is a diagram illustrating a relationship between the amount of blur H1 and the amount of blur H2 of an image q2 due to light passing through the second rod lens 36b.
Here, if the amount of blur for any one of the images is equal to or less than a predetermined value, the original reading light receiving element 2 disposed on the light receiving surface is used.
1 can operate normally.

Therefore, the smaller one of H1 and H2 shown in FIG. 6 is taken as the effective blur amount HE,
FIG. 7 shows a graph in comparison with the blur amount H of the conventional rod lens shown in FIG. However, in this case, it is assumed that Θ shown in FIG. 17B and Θ1 shown in FIG. 4 are equal. The solid line indicates HE and the broken line indicates H. In the case of the light condensing means including the first rod lens 36a and the second rod lens b of the present embodiment shown in FIG. 2, the effective blur amount for the movement of the light emitting point should be kept small over a wider range than before. Can be. For example, when x is (3/2) dc, the amount of blur can be reduced to 1/3 or less of the conventional value.

As described above, when the two images are superimposed on each other and attention is paid to the light receiving effect of one of the images having smaller blur, even if the light emitting point moves, the smaller blur is obtained. In this case, since the blur can be reduced, the depth of focus can be substantially increased without reducing the aperture angle. In this manner, the effective blur (the blur of the smaller image) can be reduced, and the original reading light receiving element 21 can be operated with high accuracy.
This effect is the same also in a lens array in which a plurality of rod lenses 36 are aligned, and the effect of Θ ′ in FIG.
The effective depth of focus can be reduced substantially without reducing the synthetic aperture angle corresponding to. Therefore, in this example, it is not necessary to provide a member for restricting the opening or to reduce the diameter of the rod or to increase the distance between the light emitting point and the light receiving point in order to reduce the opening angle.

As described above, by using two types of rod lenses having different focal lengths TC in combination, a bifocal lens for condensing light from one light emitting point at two different positions is formed, and is moved from the reference point. It is possible to effectively reduce the effective blur of the image due to this (the smaller of the smaller image). In addition, since there is no limiting member and the aperture angle can be widened as described above, the size of the apparatus can be reduced, and the light amount on the light receiving surface can be sufficiently obtained. Thus, in the contact type image reading apparatus according to the present embodiment shown in FIG.
If a gap is formed between the transparent plate 27 and the original 29 due to bending or spread of the original 29, and the light emitting point of the reflected light on the original surface is shifted forward from the position of the surface of the transparent plate 27, this shift is caused. As a result, the amount of blurring that occurs in image formation in the document reading light receiving element 21 disposed on the light receiving surface can be greatly reduced compared with the conventional art. Data can be read accurately.

In this example, as shown in FIGS. 3 and 4, the light emitting point A0 (A0 ') is set to the first rod lens 36.
Although the case where the light emitting point A0 'is located on one side from the extension of this boundary has been described above on the extension of the boundary between the first rod lens 36a and the second rod lens 36b, the same principle applies. A first light converging point B01 'and a first light converging point B02' are formed at the erect position, and a bifocal lens system is formed, thereby producing the same operation and effect as described above.

Hereinafter, an example of an image reading apparatus according to another preferred embodiment of the present invention will be described with reference to the drawings. 8A and 8B are diagrams illustrating the configuration of the image reading apparatus according to the present embodiment, in which FIG. 8A is a cross-sectional view and FIG. 8B is a top view. In (b), the display of the original 29 and the transparent plate 27 is omitted. As shown in FIG. 8, the contact type image reading apparatus of the present example includes a document reading light receiving element 21 in which a plurality of sensor pixels for performing photoelectric conversion are arranged, a protective film 22, and a substrate 23 on which the protective film 22 is mounted. A light receiving element array 24, an LED array 25 as a linear light source for irradiating the original, and an original 29
A lens array 26 for forming an image of the image on the light receiving element array 24 serving as a light receiving portion, a support frame 37 for holding the lens array 26, a transparent plate 27 for placing a document 29, and an outer case for supporting these members 28.

As shown in FIG. 8B, the lens array 26 has two types of rods having different focal lengths TC in a direction parallel to the reading line L on the document surface irradiated on the LED array 25. The lenses, that is, the first rod lens 36a and the second rod lens 36b are divided into two rows and arranged in two rows, and are held by the holding frame 37. The first rod lens 36a and the second rod lens 36b are respectively the same as those shown in FIG.
The positional relationship in the optical axis direction is the same as that shown in FIG. However, the planar positional relationship is different as follows.

The planar arrangement of the first rod lens 36a and the second rod lens 36b will be described with reference to FIG.
As shown in (b), the first rod lenses 36a are in contact with or close to each other and are arranged in one row in parallel with the read line L, and the second rod lenses 36b are also in contact or close to each other and the read is performed. They are arranged in the other row in parallel with the line B. And two adjacent first
One second rod lens 36b is commonly in contact with or close to the rod lens 36a, and one first rod lens 36b is commonly in contact with or close to two adjacent second rod lenses 36b. Thus, they are arranged shifted from each other by a half pitch. The central axis 36ac of the first rod lens 36a and the central axis 36b of the second rod lens 36b
In the plane perpendicular to the axis, c forms an equilateral triangle or a shape or a substantially equilateral triangle.

A sectional view of the section including both the central axes 36ac and 36bc (a sectional view taken along the line AA in FIG. 8B) is omitted, but is the same as that shown in FIG. Therefore, the principle of the light collecting action of the lens array 26 of this embodiment is basically the same as the light collecting action of the lens array 26 in the embodiment shown in FIG. 1, and by forming a bifocal lens system. Has the effect of reducing blurring of the image on the sensor surface (the effective blurring). However, in the case of this example, three rod lenses (two first rod lenses 36a and one second rod lens 36b, or one first rod lens 36b) arbitrarily corresponding to one point on the reading line L The optical axes of the rod lens 36a and the two second rod lenses 36b) are close to each other, and an effect of further reducing image blurring due to aberration caused by the separation of the optical axes is obtained.

Hereinafter, a modification of the image reading apparatus shown in FIG. 8 will be described with reference to the drawings. FIG. 9 is a cross-sectional view illustrating a configuration of the image reading apparatus according to the present example. This example is an image reading apparatus of a non-contact type and the same magnification image forming method. As shown in FIG. 9, an original reading light receiving element 21 in which a plurality of sensor pixels for performing photoelectric conversion are arranged, a protective film 22, and a mounting film Substrate 2
3; a LED array 25 as a linear light source for irradiating the original; a lens array 26 for forming an image of the original 29 on the light receiving element array 24 as a light receiving portion; Support frame 37 for holding 26
And a reading unit 10 comprising an outer case 28 supporting these members, and a document 29 placed below the reading unit 10 for placing the original 29 and moving relative to the reading unit 10 in the direction of the arrow. And a mounting table driving unit (not shown).

The configuration of the reading unit 10 is the same as that of the image reading apparatus shown in FIG. 8 except that the transparent plate 27 is removed. The mounting table 12 is held upside down facing the mounting table 12 at a position where a predetermined gap can be secured. The operation principle and effects of the image reading apparatus of this embodiment are basically the same as those in the case of the image reading shown in FIG. 8, but since the image can be read with the original 29 facing up, a booklet For example, when an original is sequentially read in a two-page spread state, image handling is facilitated.

An example which is another preferred embodiment of the present invention will be described below with reference to the drawings. FIG.
1A and 1B are diagrams illustrating a configuration of a contact-type image reading device for reading a color image according to the present embodiment, in which FIG. 1A is a cross-sectional view thereof, and FIG. 1B is a cross-sectional view taken along line DD in FIG. The contact type image reading apparatus of the present example includes a document reading light receiving element 21 in which a plurality of sensor pixels performing photoelectric conversion are arranged, a protective film 22, and a light receiving element array 24 including a substrate 23 on which the protective film 22 is mounted.
An LED array 25 which will be described later, which is a color linear light source for irradiating the original, a lens array 26 for forming an image of the original 29 on the light receiving element array 24 which is a light receiving portion, a support frame 37 for holding the lens array, and the original 29 On which the transparent plate 27 is placed
And an outer case 28 supporting these members. Here, the configuration of the lens array 26 is the same as that of the image reading apparatus shown in FIG.

The operation of the contact type image reading apparatus for reading a color image shown in FIG. 10 will be described. As shown in FIG. 10B, the LED array 25, which is a linear light source for irradiating the original, emits substantially red light on the LED substrate 25c.
ED (R LED) 25R, LED that emits almost green light
(G LED) 25G and LED emitting almost blue light
(B LED) Three kinds of LEDs of 25B are mixed and arranged in a line in the direction of the reading line. These LEDs are turned on in a time-division manner for each color by applying a driving voltage between driving electrodes (not shown) by a light source driving circuit (not shown), and irradiate a reading line on the original surface,
The reflected light of the component of the corresponding color on the document surface is generated for each of the colors R, G, and B.

The light reflected on the original surface also enters the portion of the lens array 26 corresponding to the reflection point in a time-division manner for each of the R, G, and B colors. FIG. 11 is a view showing the light condensing action in the lens array 26 of the present example. When the light emitting point A01 'is located forward of the first focal plane Sa by x, the first rod lens 36a and the second rod lens 36b for each of RG and B light in the same manner as in the embodiment shown in FIG. Causes the first converging point B01 'and the second converging point B02', respectively. The refractive indexes of the first rod lens 36a and the second rod lens 36b tend to increase as the wavelength of the light becomes shorter. Therefore, in general, the light converging point tends to be shifted for each color, and the outgoing lights s11R, s11G, s11B of the R, G, B of the first rod lens 36a and the R, G, B of the second rod lens 36b. Outgoing light s12R, s12G,
According to s12, as shown in FIG.
B02r ', B02g', and B02b 'are generated using 1r', B01g ', and B01b' as second focusing points.

However, since the optical path in the rod lens has an undulating property, the chromatic aberration is corrected, and the shift of the focal point for each color can be made relatively small. By using rod lenses having a small color difference as the first rod lens 36a and the second rod lens 36b, the first light-condensing points B01r ', B01g', and B01b 'for each color can be mutually connected regardless of the color. The two light-condensing points B02r ', B02g', and B02b 'can be made to substantially coincide with each other regardless of the color. As a result, regarding reading of each color of the color image of the original, FIG.
According to the same principle as that of the contact type image reading apparatus shown in the above, the same operation and effect can be obtained, and a color image can be read with high accuracy. Further, even when a rod lens with less chromatic aberration cannot be used due to cost and size,
Two focal points are formed for each of the colors R, G, and B, and the effective blur on the sensor surface for each color can be reduced as compared with the related art.

Further, as a preferred embodiment of the present invention, as shown in FIG. 12, the lens array 26 includes a first rod lens 36a having a focal length TC1, a second rod lens 36b having a focal length TC2, and a focal length TC3. The third rod lens 36c is arranged periodically and sequentially in the direction of the reading line. FIG. 12A is a cross-sectional view parallel to the arrangement direction of the lens array 26, and FIG.
It is an enlarged view of the F section shown in (a). Here, the focal length has a relationship of TC1 <TC2 <TC3.

A1, A2, and A3 denote focal points of the first rod lens 36a, the second rod lens 36b, and the third rod lens 36c on the opposite side to the sensor surface S, respectively.
2, B3 are the sensor surfaces S of the first rod lens 36a, the second rod lens 36b, and the third rod lens 36c, respectively.
Side focus. Sa is a first focal plane where the focal point A1 is located, Sb is a second focal plane where the focal point A2 is located, Sc
Is a third focal plane where the focal point A3 is located. And
In front of the first focal plane Sa, the offset amount dc1 = TC2
The second focal plane Sb is located at a distance of −TC1 and the third focal plane Sa is located at a distance of an offset dc2 = TC3−TC2 in front of the second focal plane Sb. The first rod lens 36a and the second rod lens 36 are arranged such that both B2 and B3 are located on the sensor surface S.
b are sequentially shifted in the optical axis direction. In this example, the offset amount is approximately dc1 = dc2 = dc.
In a relationship.

The light condensing action of the lens array 26 of the present embodiment will be described. Of the light emitted from the light emitting point A0 'located x in front of the first focal plane Sa, the light that has passed through the first rod lens 36a is collected at a first light condensing point B01' that is substantially x away from the sensor surface S. The light that has passed through the second rod lens 36b is separated from the sensor surface S by approximately | dc−x |
The light is condensed toward the light condensing point B02 ', and the third rod lens 36
The light passing through c is converged toward a third converging point B01 ′, which is approximately | 2dc−x | away from the sensor surface S, and image formations q1, q2, and q3 occur on the sensor surface S, respectively. The focal points A1, A2, and A3 are the first rod lenses 36, respectively.
a, second rod lens 36b, third rod lens 36c
Are assumed to be Θ1, Θ2, and Θ3, respectively, and the amounts of blurring of the imagings q1, q2, and q3 are denoted by H, respectively.
Assuming that 1, H2 and H3, H1 = Θ1 | x | and H2 = Θ2 | x−dc by the same principle as described above.
|, H3 = Θ3 | x−2dc |

FIG. 13 shows the movement amount x of the light emitting point A0 'from the reference position and the blur amount H1 of the images q1, q2, q3.
It is a figure which shows the relationship between H2 and H3. Here, the amount of blur (H
If the minimum value among 1, H2, and H3) is equal to or less than the predetermined value, the original reading light receiving element disposed on the light receiving sensor surface can be normally operated.

Therefore, the smaller one of H1, H2 and H3 shown in FIG. 13 is taken to be the effective blur amount HE, which is shown in FIG. The effective amount of blur is shown in FIG.
The effective blur amount HE shown in FIG. For example, when x is (5/2) dc, the amount of blur can be reduced to 1/5 of the conventional value. This is because a three-focus lens system is configured in the lens array 26 of the present embodiment.

Further, as a preferred embodiment of the present invention, there is an image reading apparatus using the lens array 26 shown in FIG. 14 as a modification of the lens array 26 shown in FIG. FIG. 14A is a side view showing the configuration of the lens eye of the present example, and FIG. 13B is a top view. The lens array 26 of the present example includes a first rod lens 3 similar to that shown in FIG.
6a, second rod lens 36b, third rod lens 36
The positional relationship between these rod lenses in the optical axis direction is the same as that of the lens array 26 shown in FIG.

However, regarding the planar arrangement, see FIG.
According to a positional relationship similar to that shown and described in (b), they are arranged in two rows in a direction parallel to the read line L,
In each row, the first rod lens 36a, the second rod lens 36b, and the third rod lens 36c are periodically arranged in order from the left side to the right side in the drawing. The phases of the cycles are shifted, and the first rod lens 36a, the second rod lens 36b, and the third rod lens 36c which are close to each other in a plan view always form a substantially equilateral triangle. With such an arrangement, the lens array 26 of this example has the effect of reducing aberration due to the approach of the optical axis as described above, in addition to the effect of the three focal points, and effectively reduces blurring of image formation on the sensor surface. Can be reduced.

Although the embodiments of the present invention have been described with reference to the respective embodiments, the present invention is not limited to these embodiments, but can be widely applied to those having similar effects.

[0047]

As described above, according to the present invention, in an image reading apparatus having a condensing means composed of a compound eye lens, image blurring of a light receiving portion due to floating of a document can be reduced without limiting the aperture angle. In addition, it is possible to provide a small-sized device with high reading accuracy.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a diagram illustrating an operation of the image reading apparatus illustrated in FIG. 1;

FIG. 4 is a diagram showing the operation of the image reading apparatus shown in FIG.

FIG. 5 is a diagram illustrating an operation of the image reading apparatus illustrated in FIG. 1;

FIG. 6 is a diagram illustrating an operation of the image reading apparatus illustrated in FIG. 1;

FIG. 7 is a diagram showing the operation of the image reading apparatus shown in FIG.

FIGS. 8A and 8B are diagrams showing a configuration of an image reading apparatus according to an embodiment of the present invention, wherein FIG. 8A is a cross-sectional view and FIG. 8B is a top view.

FIG. 9 is a cross-sectional view illustrating a configuration of an image reading apparatus according to an embodiment of the present invention.

FIG. 10 is a cross-sectional view illustrating a configuration of an image reading apparatus according to an embodiment of the present invention.

FIG. 11 is a diagram illustrating the operation of the image reading apparatus illustrated in FIG. 10;

FIG. 12 is a diagram illustrating an operation of a main part of an image reading apparatus according to an embodiment of the present invention.

FIG. 13 is a diagram illustrating an operation of a main part of an image reading apparatus according to an embodiment of the present invention.

FIG. 14 is a diagram illustrating a configuration of a main part of an image reading apparatus according to an embodiment of the present invention.

FIG. 15 is a perspective view illustrating a configuration of a conventional image reading apparatus.

FIG. 16 is a cross-sectional view illustrating a configuration of a conventional image reading apparatus.

FIG. 17 is a view showing the operation of the image reading apparatus shown in FIG.

FIG. 18 is a cross-sectional view illustrating a configuration of a conventional image reading apparatus.

[Explanation of symbols]

 Reference Signs List 24 light receiving element array 25 LED array 26 lens array 27 transparent plate 28 outer case 29 original 36 rod lens

Claims (5)

[Claims] 1. An image comprising: an illuminating unit for irradiating an original surface; a condensing unit for forming an image of the reflected light from the illuminated original surface; and a light receiving unit for receiving the imaged light and performing photoelectric conversion. In the reading apparatus, the light condensing means is configured by arranging a plurality of lenses having at least two kinds of focal lengths having different focal lengths. 2. The image reading apparatus according to claim 1, wherein the plurality of lenses are arranged such that respective focal points coincide with substantially the same surface in the light receiving unit. 3. A lens having a different focal length in the condensing means is a rod lens whose refractive index changes in a direction perpendicular to the optical axis, and is disposed at a position shifted from each other in the optical axis direction. The image reading device according to claim 1. 4. The light condensing means according to claim 1, wherein lenses are arranged in a plurality of rows, and lenses having different focal lengths are arranged in different rows. Image reading device. 5. A lens according to claim 1, wherein said condensing means has lenses arranged so that adjacent lenses have different focal lengths. Image reading device.