TECHNICAL FIELD

The present invention relates to image forming apparatuses that record respective images on the front and back sides of a recording paper sheet and particularly relates to a technique for aligning the images to be formed on the front and back sides of the recording paper sheet.

BACKGROUND ART

There is a type of image forming apparatus that can read a front-side image of an original document and a back-side image thereof, record the front-side image of the original document on the front side of a recording paper sheet, subsequently turn over the recording paper sheet, and record the back-side image of the original document on the back side of the recording paper sheet. In this case, despite a desire to align the images to be formed on the front and back sides of the recording paper sheet, the front-side and back-side images of the original document may be formed out of alignment on the front and back sides of the recording paper sheet and not exactly coincide in position.

To cope with the above, in Patent Literature 1, an accurate position adjustment is made by using an image read by a scanner to extract one edge of a recording paper sheet contained in the image, determine the coordinates of both ends of the one edge of the recording paper sheet with respect to an origin of the image, determine a vertical deviation, a lateral deviation, and a tilt of the recording paper sheet from the coordinates of both ends of the one edge of the recording paper sheet, and correct the deviations and tilt of the recording paper sheet by image processing and further determining a misalignment of images between the front and back sides of the recording paper sheet.

Alternatively, in Patent Literature 2, correcting patterns printed on the front and back sides of a recording medium are read at once by a double-sided reader to detect the respective positions of the correcting patterns, the amount of correction for print misalignment is calculated from the detected correcting patterns on both sides, and the print misalignment between the front and back sides during double-sided printing is corrected based on the calculated amount of correction.

CITATION LIST

Patent Literature

Patent Literature 1: JP-A-2005-091823Patent Literature 2: JP-A-2011-186241

SUMMARY OF INVENTION

Technical Problem

Meanwhile, as a method of utilizing an image forming apparatus, there is a method of utilizing it by reading a front-side image and a back-side image of a small document, such as a business card or any other card, forming the front-side image and back-side image of the document on the front side and back side of a recording paper sheet, and cutting out the front-side image and back-side image of the document from the recording paper sheet to reproduce the small document, such as a business card, on both sides of which images are formed. Also in this case, it is necessary to bring the front-side image and back-side image of the document into alignment and coincidence between the front and back sides of the recording paper sheet. Furthermore, in this case, it is desirable to make it possible to concurrently read the front-side images and back-side images of a plurality of small documents and cut out reproductions of these documents from a single recording paper sheet.

However, in Patent Literature 1, since deviations and a tilt of a recording paper sheet are corrected with reference to the origin of an image read by a scanner, even images of small documents cannot concurrently be formed and need to be formed on a document-by-document basis.

On the other hand, in Patent Literature 2, since it is necessary to print correcting patterns on the front and back sides of a recording medium, it is not possible to make reproductions of general business cards and other cards.

The present invention has been made in view of the above circumstances and has an object of enabling, even from a plurality of small documents, their front-side and back-side images to be formed on a single recording paper sheet, with alignment and coincidence of the front-side and back-side images of each document between the front and back sides of the single recording paper sheet.

Solution to Problem

An image forming apparatus according to an aspect of the present invention includes: an image reading section that reads images of an original document; a control section that allows the image reading section to read a front-side image of the original document in a first scan and then read a back-side image of the original document in a second scan; an image processing section that detects the front-side image of the original document from a whole image of a scan area read in the first scan by the image reading section, detects the back-side image of the original document from a whole image of a scan area read in the second scan by the image reading section, and performs image processing of moving or rotating the front-side image or the back-side image of the original document to move a position of the front-side image or the back-side image of the original document in the whole image of the scan area to a position where the front-side image and the back-side image are brought into alignment and coincidence between a front side and a back side of a recording paper sheet; and an image forming section that, under control of the control section, forms on the front side of the recording paper sheet the whole image of the scan area read in the first scan and subjected to the image processing by the image processing section and forms on the back side of the recording paper sheet the whole image of the scan area read in the second scan and subjected to the image processing by the image processing section.

Advantageous Effects of Invention

The present invention enables, even from a plurality of small documents, their front-side and back-side images to be formed on a single recording paper sheet, with alignment and coincidence of the front-side and back-side images of each document between the front and back sides of the single recording paper sheet.

