1. Field of the Invention
The present invention relates to an image scanning apparatus and an image scanning method and in particular, to an image scanning apparatus and an image scanning method using a sub scan mechanism for combining a linear partial image obtained by a linear image sensor, thus inputting a two-dimensional manuscript image.
2. Description of the Related Art
Conventionally, various types of image scanning apparatus have been suggested. Among them, an image scanner apparatus uses a linear image sensor as a pickup device in the image input mechanism and a sub scan mechanism for combining partial images obtained by the linear image sensor for inputting a two-dimensional manuscript.
The image scanner apparatus can be divided into an indirect type image scanner apparatus in which the manuscript surface is apart from the image input mechanism supported by a stand or the like and a flat bed type image scanner in which the manuscript surface is placed downward on the image input mechanism unitizing the manuscript surface and the image input mechanism.
In the conventional indirect type image scanner apparatus, the brightness of the manuscript surface depends on the natural light or the ordinary illumination on the ceiling and no particular illumination is used for the image scanner or an auxiliary illumination is used for illuminating the entire manuscript surface.
In the indirect image scanner not using any auxiliary illumination, the brightness of the manuscript surface may not be sufficient, which relatively increases the noise level of the image sensor output, adversely affecting the image read in. Moreover, in the indirect image scanner using an auxiliary illumination, the auxiliary illumination may dazzle eyes of a user and cause an unpleasant heat.
Such an image scanning apparatus or image scanning method is disclosed, for example, in Japanese Patent Publication 3-136569 [1], in which a manuscript is placed around a cylindrical member and the manuscript is scanned by a CCD line sensor in the main scan direction while the sub scan is performed by rotation of the cylindrical member, so as to store an image of the manuscript. This image scanning apparatus cannot realize a high-speed and stable image reading.
Moreover, Japanese Patent Publication 7-177318 [2] discloses an image scanning apparatus in which a unitary block of a light source and a line image sensor is detachably fixed to a slit provided on a manuscript table and displaced manually, so as to enable to read a transient manuscript as well. However, since the unit is displaced manually, it is difficult to obtain a high-speed and stable image reading.
Furthermore, Japanese Patent Publication 8-223363 [3] discloses an image scanning apparatus in which three color lights are successively applied by a light emitting device for each line, so as to scan the entire manuscript surface to read an image. This image scanning apparatus, the light emitting device is displaced by a motor and a chain for scanning. Accordingly, it is difficult to perform a high-speed and stable image reading.
Furthermore, Japanese Patent Publication 8-315122 [4] discloses a transparent type image scanning apparatus, in which a mesh gradation is inserted between a manuscript and a light source so as to correct a transmitting light amount in the direction of a line image sensor. However, document [4] has no disclosure on the light amount adjustment in a reflection type image scanning apparatus.
On the other hand, Japanese Patent Publication 9-261419 [5] discloses a reflection type image scanning apparatus in which a slit-shaped light emitted from a light source is used to scan a manuscript by displacing a reflection mirror and a line image sensor is displaced in synchronization with the slit-shaped light beam scan. However, since the line image sensor moves a great distance as a parallel displacement, a complicated synchronization mechanism is required. Moreover, the parallel displacement of the image sensor may cause a vibration which deteriorates the image. Accordingly, it is difficult to obtain a high-speed and stable image reading.
Additionally, Japanese Patent Publication 7-193682 [6] discloses a reflection type image scanning apparatus, in which an optical mark is applied to a position corresponding to a manuscript scan range. Moreover, Japanese Patent Publication 8-9102 [7] discloses a scanner technique associated with an image scanner including an image read unit having an image formation device, an image read device, and an illumination device which are constituted as a unitary block. Furthermore, Japanese Patent Publication 10-336404 [8] discloses a reflection type image scanning apparatus in which a reference region is provided on a manuscript table so as to compensate a brightness change of the illumination light depending on a frequency of a fluorescent lamp provided on a ceiling or the like.
However, none of the aforementioned documents [6 ] [7], and [8] discloses an image reading mechanism in a stand type image scanning apparatus for scanning a slit-shaped light beam or a technique for detecting the brightness of the light beam reflection for controlling the light beam light quantity.
Among the indirect type image scanners, those not using an auxiliary illumination for the image input mechanism have a problem that the brightness on the manuscript surface is not sufficient, which relatively increases the noise level of the output of the image sensor, adversely affecting the image which has been read in, and those using an auxiliary illumination for illuminating the entire manuscript surface have a problem that eyes of a user are dazzled and the heat is unpleasant for the user.
It is therefore an object of the present invention to provide an image scanning apparatus and an image scanning method realized as an indirect type image scanner apparatus capable of a high-speed, high-quality image input without causing to dazzle eyes of a user while securing a necessary brightness.
The image scanning apparatus according to a first embodiment of the present invention comprises a support arm, a stand block supporting the support arm, a scan type illumination device mounted on the support arm for applying a slit-shaped light beam onto a surface of a manuscript, and a manuscript image scanning device for scanning a manuscript image illuminated by the slit-shaped light beam and reflected from the surface of the manuscript, wherein the scan type illumination device is constructed so as to apply the slit-shaped light beam in a direction vertical to the longitudinal direction of the slit shape of the slit-shaped light beam, the image scanning device includes a manuscript image input block for inputting a reflected light containing a manuscript image reflected from the surface of the manuscript and a light detecting device supplied with the reflected light containing the manuscript image which is output from the manuscript image input block, and the manuscript image input block is constructed in such a manner that the reflected light containing the manuscript image reflected from the manuscript surface is selectively applied to a predetermined portion of the light receiving surface in the light detecting device in synchronization with the scan operation of the scan type illumination device.
The image scanning method according to a second embodiment of the present invention uses an image scanning apparatus comprising a support arm, a stand block supporting the support arm, a scan illumination device mounted on the support arm for applying a slit-shaped light beam onto a surface of a manuscript, and a manuscript image scanning device for inputting a manuscript image illuminated by the slit-shaped light beam and reflected from the manuscript surface; the method comprising steps of: applying the slit-shaped light beam from the scan type illumination device; causing the slit-shaped light beam to scan in a direction vertical to the longitudinal direction of the slit in the slit-shaped light beam; in the manuscript image input block, receiving a light reflected from the manuscript surface containing a manuscript image, and selectively applying the reflected light containing the manuscript image to a predetermined portion of the light receiving elements in the light detecting device provided in the image scanning device; and displacing the manuscript image input block in synchronization with the scan operation by the scan type illumination device.