JPS6474687A - Reading method for crossed square-shaped code - Google Patents

Abstract

PURPOSE:To allow scanning in a wide range of angles by setting a reference line of a prescribed size in parallel with a crossed square-shaped code set along a first direction, scanning the reference line within a prescribed angle to decide a scan starting point from the relative angle and based on one of both ends of the reference line, and reading the information on each mesh of the code. CONSTITUTION:A reference line 3 and the scanning direction of a crossed square-shaped code 1 are tilted and the coordinates X00Y00 are defined as the initial value of the line 3 when the number of continuous black picture elements exceeds a fixed value. The scans are successively carried out and a line along which the prescribed number of black picture elements are continuous is obtained. At the left end point, this end point is updated based on X20<X10<X00 together with updating of the X coordinates. No updating is carried out in case of X20<X30<.... At the right end point, the coordinates of this point are updated based on X00<X11<... together with the Y coordinates. While the X coordinates are not updated in case of X81>X91>.... The tilt of the line 3 is obtained from those coordinates and the left point is defined as a standard point. The points separate from the reference point of the line 3 in the (y) direction by 2.5, 7.5 and 9.5mm are decided as the mesh scanning start points of the code 1a for decision of the black or white meshes based on the known positional relation between the code 1 and the line 3. In such constitution, the errors in the (x) and (y) directions and the rotational direction error are allowed for recognition of the code 1.