JPH10290336A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader high in image quality, high in resolution and capable of reading selectively an optically transparent original and a reflection original in an image scanner, a digital copying machine or the like. SOLUTION: This reader is provided with a reflection lighting unit 18 that emits a light to a reflection original 15, a reflection original image forming lens 23, and a solid-state image pickup element 24, and also with an optically transparent original reader unit 28 having a transparent original use lighting unit 32 that emits a light to a transparent original 30 and an optically transparent original image forming lens 34 or the like, and an external optical light input mirror frame 27 is supported turnably with a movable carriage frame 17 in order to allow the solid-state image pickup element 24 to read the image formed by the optically transparent original image forming lens 34. Thus, the image reader is obtained with high resolution, by which the transparent original 30 or the reflection original 15 is selectively read.

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 for a flatbed type image scanner, a digital copying machine, and the like.

[0002]

2. Description of the Related Art Conventionally, an image reading apparatus has been used as an input method and an input device of a printer and a computer.

Hereinafter, a conventional image reading apparatus will be described with reference to FIG. FIG. 6 is a longitudinal sectional view of a conventional image reading apparatus.

In FIG. 6, reference numeral 1 denotes a main body of the image reading apparatus, 2 denotes an original, 3 denotes an original glass on which the original 2 is placed, 4 denotes a carriage frame for supporting each component described later, 5
Is a reflection illumination unit for irradiating the original 2 when the original 2 is a reflective original; 6 to 9 are reflection mirrors for causing the reflected light from the original 2 to reach an imaging lens 10 described later;
0 is an imaging lens for scaling the reflected light from the original 2 to a predetermined magnification and forming an image on a solid-state imaging device 11 described later;
Reference numeral 11 denotes a solid-state imaging device that converts an image of the document 2 formed by the imaging lens 10 into an electric signal. The reflection illumination unit 5, the reflection mirrors 6 to 9, the imaging lens 10, and the solid-state imaging device 11 are supported by the carriage frame 4. On the other hand, a transmission illumination unit support frame 12 supports a transmission illumination unit 13 for irradiating the original 2 when the original 2 is a light transmission original.

Here, the reading operation in the conventional image reading apparatus shown in FIG. 6 will be described. First, when the original 2 is a reflective original, the original 2 placed on the original glass 3 is irradiated with light from the reflective illumination unit 5 and the reflected light is transmitted through the reflecting mirrors 6 to 9 to form the image forming lens 10. , The imaging lens 10 changes the size of the reflected light at a predetermined magnification, and then forms an image on the solid-state imaging device 11. When reading the entire original 2, the carriage frame 4 may be used in accordance with the length of the original 2.
Are scanned in the direction of arrow A.

Next, when the original 2 is a light-transmitting original, the original 2 placed on the original glass 3 is irradiated with light from a transmission illumination unit 13 supported by a transmission illumination unit support frame 12. When the reflective illumination unit 5 supported by the carriage frame 4 is turned off, the transmission illumination unit 13 and the carriage frame 4 simultaneously move the arrow A according to the length of the document 2.
Scan in the direction. The light transmitted through the original 2 reaches the imaging lens 10 via the reflection mirrors 6 to 9 as described above, and after the imaging lens 10 changes the transmission light at a predetermined magnification, the solid-state imaging An image is formed on the element 11.

[0007]

Generally, the reading resolution required for reading a reflective original and the reading resolution required for reading a light-transmitting original are different from each other. A higher resolution is required when reading a transparent original.

However, when a high-resolution lens for reading a light-transmitting original is provided separately from a lens for reading a reflective original, the cost of the main body is increased, which is inconvenient for a user who only reads a reflective original. is there.

On the other hand, when a light-transmissive original is read, a high resolution required for the light-transmissive original cannot be realized if a lens for reading the reflective original is shared, so that the user who reads the light-transmissive original is satisfied. Can not do.

[0010] Therefore, a user who handles both a reflection original and a light transmission original needs to separately purchase a high-resolution reading device dedicated to the light transmission original.

It is an object of the present invention to solve the above-mentioned conventional problems and to provide an image reading apparatus capable of reading at a high resolution according to a document handled by a user so as to be able to be added at a low cost. .

[0012]

In order to solve the above-mentioned problems, the present invention provides a reflection illuminating lamp for irradiating a document with light, a reflection image forming means for forming an image by reflected light of the document,
In an image reading apparatus provided with a solid-state imaging device for reading a reflection image formed by a reflection image forming means, a transmission illumination lamp for irradiating a light-transmitting original with light and an image formed by transmitted light of the light-transmitting original are formed. A transmission original reading unit provided with a transmission image forming means for forming an image, and an optical path switching means for causing a solid-state imaging device to read an image formed by the transmission image forming means.

According to the present invention, by switching the optical path by the optical path switching means, it is possible to selectively read both the reflection original and the light transmission original, and to obtain an image reading apparatus having a high resolution.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a reflection illuminating lamp for irradiating a document with light, a reflection image forming means for forming an image by reflected light of the document, and In an image reading apparatus including a solid-state imaging device that reads a reflection image formed by a reflection image forming unit, a transmission illumination lamp that irradiates light to a light transmission original, and an image formed by the transmitted light of the light transmission original. A transmission original reading unit including transmission image forming means for forming an image; and an optical path switching means for causing the solid-state imaging device to read an image formed by the transmission image forming means. By switching the optical path by the optical path switching means, it is possible to selectively read both the reflection original and the light transmission original.

According to a second aspect of the present invention, there is provided a detecting means for detecting a contrast of an image formed on the solid-state imaging device by the transmitted image forming means, and the transmitting means for detecting the contrast based on a detection signal of the detecting means. A focus adjusting means for changing an optical path length from an illumination lamp to the solid-state imaging device; and has an effect of facilitating focus adjustment when reading a light-transmitting original and improving sharpness.

According to a third aspect of the present invention, there is provided a focus detection chart which can be formed by the transmission image forming means in parallel with the light transmitting original, so that accurate focus adjustment can be performed. It has the effect of being able to.

According to a fourth aspect of the present invention, the focus detection chart includes a light transmitting portion and a light shielding portion, and the accuracy of focus adjustment is enhanced to further improve the sharpness. Has the effect of being able to.

An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a vertical cross-sectional view of an image reading apparatus when reading a reflection original according to an embodiment of the present invention. FIG. 2 is a vertical cross-sectional view of the image reading apparatus when reading a light-transmitting original according to the embodiment of the present invention. FIG. 4 is a plan view of a light-transmitting original supporting frame of the image reading apparatus, FIG. 4 is an explanatory diagram of a focus detection chart reading operation of the image reading apparatus, and FIG. 5 is a solid-state image pickup when reading the focus detection chart in the embodiment of the present invention. FIG. 4 is an explanatory diagram of focus detection by an element.

In FIG. 1, reference numeral 14 denotes an image reading apparatus main body, 15 denotes a reflective original, 16 denotes an original glass on which the reflective original 15 is placed, 17 denotes a carriage frame for supporting each component described later, and 18 denotes a reflective original 15. This is a reflection lighting unit for irradiating light.

Reference numerals 19 to 22 denote reflecting mirrors for causing the reflected light of the light irradiated on the reflecting original 15 to reach the reflecting original imaging lens 23, and 23 changes the reflected light of the reflecting original 15 to a predetermined magnification. A reflection original imaging lens for doubling and forming an image on the solid-state imaging element 24; a solid-state imaging element 24 for converting the image of the reflection original 15 formed by the reflection original imaging lens 23 into an electric signal; is there.

Reference numeral 27 denotes an external light input mirror frame provided with reflection mirrors 25 and 26 for guiding external light from the light transmitting original reading unit 28 to the solid-state image pickup device 24 disposed in the carriage frame 17. is there.

The carriage illumination unit 18, the reflection mirrors 19 to 22, the reflection original imaging lens 23, the solid-state image pickup device 24, and the external light input mirror frame 27 are supported by the carriage frame 17.

In the light transmitting original reading unit 28,
Focus detection chart 2 for reading light transmitting original 30
9, a light transmission document supporting frame 31 for supporting the focus detection chart 29 and the light transmission document 30, a transmission illumination unit 32 for irradiating the light transmission document 30 with light, and a light passing through the light transmission document. A reflection mirror 33 for guiding the image to the transmission original imaging lens 34 is provided.

Here, the operation of the image reading apparatus according to the embodiment of the present invention will be described. First, when reading the reflective original 15, the light of the illumination unit 18 for reflection is applied to the reflective original 15 placed on the original glass 16, and the reflected light is transmitted through the mirrors 19 to 22 to form an image for the reflective original 15. The light is guided to the lens 23 and is imaged on the solid-state imaging device 24 at a predetermined magnification. When reading the entire reflective original 15, the carriage frame 17 is scanned in the direction of arrow A according to the length of the reflective original 15. At this time, as shown in FIG. 1, the external light input mirror frame 27 stands by below so as not to block the optical path from the reflective original imaging lens 23 to the solid-state imaging device 24.

Next, when reading the light transmitting original 30,
As shown in FIG. 2, since the external light mirror frame 27 in the carriage frame 17 rotates 90 degrees about the support shaft 27a, the light transmitted through the light transmitting original 30 is reflected by the reflection mirror 33 and the light transmitting original. Imaging lens 34 and reflection mirrors 25 and 26
And reaches the solid-state imaging device 24 via the.

Here, referring to FIGS.
The focus detection method when reading is described. When reading the light transmission original 30, as shown in FIG. 3, the focus detection chart 29 and the transmission original support frame 31 supporting the light transmission original 30 are mounted on the light transmission original reading unit 28, and the transmission illumination unit 32 is turned on. When turned on, FIG.
As shown in (2), the image of the focus detection chart 29 is formed on the solid-state imaging device 24.

At this time, the image formed on the solid-state image sensor 24 is
Black part 29a, white part 29b of focus detection chart 29
Is detected by the solid-state imaging device 24.
The output potential of each element of the solid-state imaging device 24 differs depending on the brightness of the focus detection chart 29, and is high in the white portion 29b and low in the black portion 29a of the focus detection chart 29. Taking the detected potential of each element in the Y-axis direction in the element row, the detection result as shown in FIG. 5 is obtained.

As shown in FIG. 5, when the best focus is achieved, the black portion 29a and the white portion 29b of the focus detection chart 29 are displayed.
Is clearly displayed on the solid-state imaging device 24,
When the potential difference between the adjacent elements increases and the image is out of focus, the black portion 29a and the white portion 29 of the focus detection chart 29 are displayed.
The detection result is obtained in which the boundary portion of b is projected on the solid-state imaging device 24 in a blurred state, and the potential difference between the adjacent devices is reduced due to the influence of the surrounding image. That is, as shown in FIG. 5, when the image is out of focus, the gradient becomes gentle as shown by a broken line, and when the image is best focused, the gradient becomes steep as shown by a solid line.

Accordingly, when the contrast is in the state shown by the broken line in FIG. 5, the carriage frame 17 is moved until the state shown by the solid line is reached, and By adjusting the optical path length, focus adjustment can be performed. That is, the focus detection chart 29 is displayed on the transmission illumination unit 32.
, The transmission illumination unit 32 is turned on, the focus detection chart 29 is read by the solid-state imaging device 24, and as shown by the solid line in FIG. The focus can be adjusted by moving the body 17.

When the movement of the carriage frame 17 for focus adjustment is completed and the carriage frame 17 stops at a position after the focus adjustment is completed,
The transmissive illumination unit 32 is turned on, and the transmissive document support frame 31 supporting the light transmissive document 30 moves in the direction of arrow B shown in FIG.

As described above, by providing the light transmission original reading unit 28 in the image reading apparatus main body 14,
Image processing board (not shown) of image reading device main body 14
In addition, since the solid-state imaging device 24 and the like can be shared, the cost of the light transmission original reading unit 28 can be reduced. In addition, since the optical path of the light transmitting original reading unit 28 and the optical path of the image reading apparatus main body 14 can be connected, and the defocus generated at that time can be eliminated by moving the carriage frame 17, the sharpness of the image can be reduced. It is possible to provide a high image reading device.

[0032]

As described above, according to the first aspect of the present invention, the optical path is switched by the optical path switching means, so that a single image reading apparatus can handle both the reflection original and the light transmission original. An advantageous effect of being able to selectively read is obtained.

According to the second aspect of the invention, when reading a light-transmitting original, it is possible to perform accurate focus adjustment, and an advantageous effect of improving sharpness is obtained.

According to the third aspect of the present invention, an advantageous effect that the focus detection accuracy is improved by using a specific focus detection chart can be obtained.

According to the fourth aspect of the present invention, the potential difference between the light transmitting portion and the light shielding portion can be made large, the detection accuracy of the focus position where the potential difference between the adjacent elements becomes maximum, and the sharpness can be improved. The advantageous effect that the degree can be improved is obtained.

[Brief description of the drawings]

FIG. 1 is a vertical cross-sectional view of an image reading apparatus when reading a reflection original according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of the image reading apparatus when reading a light-transmitting original according to the embodiment of the present invention.

FIG. 3 is a plan view of a light transmitting original support frame of the image reading apparatus shown in FIGS. 1 and 2;

FIG. 4 is an explanatory diagram of a reading operation of a focus detection chart of the image reading apparatus shown in FIGS. 1 and 2;

FIG. 5 is an explanatory diagram of focus detection of the solid-state imaging device at the time of reading a focus detection chart according to the embodiment of the present invention.

FIG. 6 is a longitudinal sectional view of a conventional image reading apparatus.

[Explanation of symbols]

 14 Image reading apparatus main body 15 Reflective document 16 Document glass 17 Carriage frame 18 Reflection illumination unit 19-22 Reflection mirror 23 Reflection document imaging lens 24 Solid-state imaging device 25, 26 Reflection mirror 27 External light input mirror frame 27a Support Axis 28 Light transmission original reading unit 29 Focus detection chart 30 Light transmission original 31 Light transmission original support frame 32 Lighting unit for transmission 33 Reflection mirror 34 Imaging lens for light transmission original

Claims (4)

[Claims] 1. A reflection illumination lamp for irradiating a document with light, a reflection image forming means for forming an image by reflected light of the document, and a reflection image formed by the reflection image forming means. An image reading apparatus including a solid-state imaging device, wherein a transparent illuminator for irradiating a light-transmitting original with light, and a transmitted-image forming means for forming an image by transmitting light of the light-transmitting original. An image reading apparatus comprising: a reading unit; and an optical path switching unit for causing the solid-state imaging device to read an image formed by the transmission image forming unit. 2. A detecting means for detecting a contrast of an image formed on the solid-state imaging device by the transmission image forming means, and the solid-state imaging device is controlled by the transmitting illumination lamp based on a detection signal of the detecting means. 2. The image reading apparatus according to claim 1, further comprising: a focus adjusting unit that changes an optical path length up to the distance. 3. An image reading apparatus according to claim 2, further comprising a focus detection chart which can be formed by said transmission image forming means in parallel with said light transmitting original. 4. An image reading apparatus according to claim 3, wherein said focus detection chart comprises a light transmitting portion and a light shielding portion.