JPH05136945A - Picture reader - Google Patents

Abstract

PURPOSE:To obtain the picture reader whose size is made small with simple configuration by specifying one reflecting face of a reflecting mirror. CONSTITUTION:An incidence optical path of a picture light from a read picture till an image sensor 7 is formed at least one of reflecting mirrors 4, 11 and an image forming lens 6. One reflecting face of the reflecting mirrors 4, 11 is formed by a convex curved face whose radius of curvature is R, and the relation of equation I is satisfied, where (a) is the optical path length between the reflecting mirrors 4, 11 whose reflecting face is made of a convex curved face and a read picture 2, (f) is a focal distance of an image forming lens 6, and (m) is a synthesized magnification of the image forming lens 6 and the reflecting mirrors 4, 11 whose reflecting face is made of a convex curved face. Thus, the optical path length from the read picture 2 till the image sensor 7 is reduced to make the reader 10 made small. Thus, the picture reader 10 with simple configuration whose size is made small is obtained.

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 used in facsimiles, digital copying machines and the like.

[0002]

2. Description of the Related Art In a device such as a facsimile or a digital copying machine, an image reading device optically reads a read image of a document or the like and converts it into electrical image information to realize image transmission or copying. ing.

An apparatus disclosed in Japanese Patent Laid-Open No. 60-22864 will be described as a first conventional example of such an image reading apparatus with reference to FIG. In this image reading device 1, the illumination lamp 3 and the first folding mirror 4 are arranged at positions facing the read image 2, and the second folding mirror 5 is arranged on the reflection optical path of the first folding mirror 4. ing. Then, a CCD, which is a line type image sensor, is formed on the reflection optical path of the second folding mirror 5 via an imaging lens 6.
(Charge Coupled Device) 7 is arranged.

In the image reading apparatus 1 having such a configuration, the image light of the read image 2 illuminated by the illumination lamp 3 is reflected by the first and second folding mirrors 4 and 5, and the CCD 7 is formed by the imaging lens 6. By forming an image on the upper side, the CCD 7 photoelectrically converts the optical image information of the read image 2 into electrical image information. The image reading device 1
Then, the incident optical path of the image light from the read image 2 to the CCD 7 is folded back by the two folding mirrors 4 and 5 to realize the downsizing of the apparatus and to secure the optical path length to improve the reading accuracy. ..

Next, an apparatus disclosed in Japanese Patent Laid-Open No. 1-106567 will be described as a second conventional example of an image reading apparatus with reference to FIG. In this image reading device 8, the second folding mirror 5 of the image reading device 1 described above as the first conventional example is enlarged, and the third folding mirror 9 is arranged at a position facing the second folding mirror 5 to form an optical path. It has a structure that is repeatedly folded.

In the image reading device 8 having such a structure, the image light of the read image 2 illuminated by the illumination lamp 3 is reflected by the three folding mirrors 4, 5, 9 and then is formed by the imaging lens 6. By forming an image on the CCD 7, this CCD 7
Is adapted to photoelectrically convert the optical image information of the read image 2 into electrical image information. In the image reading device 8, the incident light path of the image light from the read image 2 to the CCD 7 is repeatedly folded between the second and third folding mirrors 5 and 9 so that the image reading described above as the first conventional example is performed. It is designed to be smaller than the device 1.

[0007]

In the image reading apparatus 1 described above as the first conventional example, the optical path length is ensured by folding the incident optical path of the image light by the first and second folding mirrors 4 and 5. The image reading apparatus 8 described above as the second conventional example is designed to be small in size, and by repeatedly folding the incident light path of the image light by two folding mirrors 4, 5 and 9. The device is becoming smaller.

Here, the image reading devices 1 and 8 as described above.
Then, generally, the focal length of the imaging lens 6 is f, the distance between the principal points of the imaging lens 6 is HH ′, and the read image 2 to the CCD 7
Letting L be the object image distance, which is the optical path length up to, and m be the composite magnification of the conjugate optical system, the relationship of L = (m + 1) ² (f + HH ′) / m is satisfied. For example, in a facsimile apparatus (not shown) that scans and scans a B4 size document, the composite magnification m of the conjugate optical system is about 0.1 because of the scanning line density and the element density of the image sensor. From the relationship, the focal length f of the imaging lens is about 30 (mm) and the distance between principal points HH 'is about 0 (mm), so the object image distance L is as long as about 300 (mm). ..

Therefore, in the above-mentioned image reading devices 1 and 8, the number of times the incident light path of the image light is turned back is increased to reduce the size of the device while ensuring the object image distance. However, in this case, since the loss of optical information increases due to the increase in the number of reflections, the reading accuracy deteriorates, and it becomes necessary to increase the number of folding mirrors 4, 5 and 9 and increase the size of the shape. The weight reduction and productivity of the device will also be hindered.

The present invention provides an image reading apparatus which has a simple structure and can be miniaturized.

[0011]

In an image reading apparatus in which an incident light path of image light from a read image to an image sensor is formed by at least one folding mirror and an imaging lens, one reflecting surface of the folding mirror has a curvature. The reflecting surface is formed by a convex curved surface having a radius R and the reflecting surface has a convex curved surface and the optical path length between the folding mirror and the read image is f, the focal length of the imaging lens is f, and the imaging lens and the reflecting surface are convex curved surfaces. When the composite magnification with the folding mirror is m, the relationship of f> aRm / {R−m ² (2a + R)} is satisfied.

[0012]

The length of the optical path from the read image to the image sensor can be shortened to reduce the size of the apparatus, and an image reading apparatus that can be downsized with a simple structure can be obtained.

[0013]

Embodiments of the present invention will be described with reference to FIGS. First, in the image reading apparatus 10, as illustrated in FIG. 1, the LED (Li
An illumination lamp 3 such as a ght Emitting Diode) array and a first folding mirror 4 are arranged, and a second folding mirror 11 having a reflecting surface formed of a convex curved surface is arranged on the reflection optical path of the first folding mirror 4. Has been done. Then, the CCD 7 which is a line type image sensor is arranged on the reflection optical path of the second folding mirror 11 via the imaging lens 6.

Here, the above-mentioned conventional image reading apparatus 1,
8, the focal length of the imaging lens 6 is generally f, the distance between the principal points of the imaging lens 6 is HH ', and the read image 2 is taken from the CCD.
It is formed so as to satisfy the relationship of L = (m + 1) ² (f + HH ′) / m (1) where L is the object image distance which is the optical path length to 7 and m is the composite magnification of the conjugate optical system. However, in the image reading apparatus 10 of the present embodiment, the radius of curvature of the convex reflecting surface of the second folding mirror 11 is R, the optical path length between the second folding mirror 11 and the read image 2 is a, When the synthetic magnification of the double folding mirror 11 and the imaging lens 6 is m, it is formed so as to satisfy the relationship of f> aRm / {R−m ² (2a + R)} (2).

The image forming lens 6 referred to here includes, for example, a lens device in which a plurality of optical lenses are continuously arranged coaxially and integrated.

In the image reading apparatus 10 having such a configuration, the image light of the read image 2 illuminated by the illumination lamp 3 is reflected by the first and second folding mirrors 4 and 11, and the CCD 7 is formed by the imaging lens 6. By focusing on the image, this CCD7
Is adapted to photoelectrically convert the optical image information of the read image 2 into electrical image information.

In this image reading apparatus 10, the reflecting surface of the second folding mirror 11 is formed as a convex curved surface and the conditional expression (2) described above is satisfied.
The object image distance L, which is the optical path length up to, is shortened, and the device is downsized. Moreover, in the image reading apparatus 10, since it is not necessary to increase the number of reflections of the image light in order to realize such miniaturization, the loss of optical information is reduced and the reading accuracy is good, and the folding mirror 4 is provided. Since it is not necessary to increase the number of 11 and 11 or increase the size of the shape, it is possible to reduce the weight and improve the productivity.

Here, it will be verified below based on FIG. 2 that the object image distance L is shortened by the conditional expression (2) as described above. First, the optical path length from the read image 2 to the second folding mirror 11 is a, the optical path length from the second folding mirror 11 to the first principal point of the imaging lens 6 is c, and the principal point of the imaging lens 6 is Assuming that the distance between them is HH 'and the optical path length from the second principal point of the imaging lens 6 to the CCD 7 is d, the object image distance L
L = a + c + HH '+ d (3) Therefore, assuming that the radius of curvature of the convex reflecting surface of the second folding mirror 11 is R, and the optical path length from the reflecting surface of the second folding mirror 11 to the virtual image 12 of the read image 2 is b, from the existing relational expression, 2 / R = 1 / b-1 / a (4) and the focal length of the imaging lens 6 is f, then 1 / f = 1 / (b + c) + 1 / d (5) 6 is m ₁ , the magnification of the second folding mirror 11 is m ₂ , and the synthetic magnification of the imaging lens 6 and the second folding mirror 11 is m, m ₁ = b / a (6) m ₂ = D / (b + c) (7) m = m ₁ m ₂ (8) Therefore, the conditional expressions (4) to (8) described above are changed to conditional expressions.
Substituting into (3), L = 2a ² / (2a + R) + {R + m (2a + R)} ² (f + HH ′) / Rm (2a + R) (9) For example, when the reflecting surface of the second folding mirror 11 is formed to be a flat surface by using the same imaging lens 6 as that of the image reading apparatus 10, the object image distance L'where the composite magnification of the conjugate optical system is m From the conditional expression (1), L ′ = (m + 1) ² (f + HH ′) / m (10), so that the reflecting surface of the second folding mirror 11 is a convex curved surface, the object image distance L is reduced. The conditional expression to be shortened is the above conditional expression
From (9) and (10), (m + 1) ² (f + HH ′) / m> 2a ² / (2a + R) + {R + m (2a + R)} ² (f + HH ′) / Rm (2a + R) ... (11). Therefore, by modifying the conditional expression (11), the conditional expression (2) of the present invention can be obtained.

Therefore, in the image reading apparatus 10 actually designed by the applicant based on the above conditions, the imaging lens 6 with a focal length of 30 (mm) and the line type with an element pitch of 14 (μm) are used. The CCD 7 is used to set the optical path length a from the read image 2 to the second folding mirror 11 to 140 (mm), and the radius of curvature R of the reflecting surface of the second folding mirror 11 to 500 (mm). The synthetic magnification m of the imaging lens 6 and the imaging lens 6 was set to 0.112. Then, when these numerical values are substituted into the conditional expression (2) of the present invention, "30>16" is satisfied, which satisfies the condition. Therefore, the object image distance L in this case is 287 (mm) from the conditional expression (9).
Under the same conditions, the object image distance L'when the reflecting surface of the second folding mirror 11 is a flat surface is 331 (m) from the conditional expression (10).
m), it was confirmed that the image reading device 10 can shorten the object image distance L satisfactorily.

In this embodiment, the folding mirrors 4 and 11 are used.
Exemplifies two image reading devices 10, but the present invention is not limited to the above-described form, and as illustrated in FIG. 3, the folding mirrors 4, 11, 13 have three image reading devices 14 and the like. Can also be implemented. By doing so, as shown in the drawing, the imaging lens 6 is formed on the second folding mirror 11.
It is possible to arrange the CCD 7 and the CCD 7 so as to favorably downsize the image reading device 14. In the image reading device 14 actually designed by the applicant with such a structure, the image forming lens 6 having a focal length of 22 (mm) and the line type CCD 7 having an element pitch of 14 (μm) are used. The optical path length a from the read image 2 to the second folding mirror 11 is 100 (mm), the radius of curvature R of the reflecting surface of the second folding mirror 11 is 400 (mm), the second folding mirror 11 and the imaging lens 6 are Combined ratio m of 0.112
And Therefore, when these numerical values are substituted into the conditional expression (2) of the present invention, “22> 11.4” is satisfied, which satisfies the condition. Therefore, when the object image distance L in this case is calculated, the conditional expression
From (9) to 212 (mm), the object image distance L'when the reflecting surface of the second folding mirror 11 is a flat surface under the same condition is a conditional expression.
(10) to 243 (mm), so this image reading device 14
It was confirmed that the object image distance L can be shortened satisfactorily.

[0021]

As described above, the present invention is an image reading apparatus in which an incident light path of image light from a read image to an image sensor is formed by at least one folding mirror and an imaging lens. The reflecting surface is formed by a convex curved surface having a radius of curvature R, and the optical path length between the folding mirror having the convex curved surface and the read image is a, the focal length of the image forming lens is f, the image forming lens and the reflecting surface. Let m be the composite magnification of the convex curved surface with the folding mirror, the optical path length from the read image to the image sensor can be determined by satisfying the relationship of f> aRm / {R−m ² (2a + R)}. This has effects such as shortening and downsizing the apparatus, and obtaining an image reading apparatus that can be downsized with a simple structure.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a dimensional relationship of each component.

FIG. 3 is a side view showing a modified example.

FIG. 4 is a side view showing a first conventional example.

FIG. 5 is a side view showing a second conventional example.

[Explanation of symbols]

 2 Read image 4, 11, 13 Folding mirror 6 Imaging lens 7 Image sensor 10, 14 Image reading device

Claims (1)

[Claims] 1. An image reading apparatus in which an incident light path of image light from a read image to an image sensor is formed by at least one folding mirror and an imaging lens, and one reflecting surface of the folding mirror has a convex surface with a radius of curvature R. The optical path length between the folding mirror whose reflection surface is a convex curved surface and the read image is a, the focal length of the imaging lens is f, the imaging lens and the folding mirror whose reflective surface is a convex curved surface. The image reading apparatus is characterized in that the relation f> aRm / {R−m ² (2a + R)} is satisfied, where m is the composite magnification of.