JPS63252067A - Image read input device equipped with gamma correction function - Google Patents

Abstract

PURPOSE:To attain pseudo halftone binarization processing suitable for a gamma coefficient of a printer to be used by printing a test pattern and adding a circuit measuring the density and applying the optimum gamma correction to an image read input device. CONSTITUTION:A gradation pattern generating circuit 7 generates a pattern of each intermediate gradation using pseudo halftone expression, outputs the result through a printer output section 8 to print out a pseud halftone gradation pattern. The optical image being the result of print is quantized by a photoelectric converting circuit 1 and an A/D conversion circuit 2. The gamma characteristic curve of the printer is obtained from the quantized optical image to write the gamma correction value onto the gamma correction table 3 from the curve. Then the original is read by the photoelectric conversion circuit 1 and its output is sent to an external output section 5 and a printer output section 8 via the A/D conversion circuit 2, the gamma correction table 3 and the binarization circuit 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the field of information processing, and more particularly to an image reading input device.

[Prior Art] - An image reading input device is used as a means for inputting image information to a TFF information processing device.

This is generally due to the optical
The 1r1 information is converted into electromagnetic -In information by a photoelectric conversion means, and the image information can be processed in a tn information processing device. Most human-powered image reading devices convert optical density into binary electromagnetic information using a certain threshold. There are some that can perform binarization.

[Problems to be Solved by the Invention] When performing pseudo-halftone expression, a display device or a printer is often used as the final output device. Printers include wire dot, inkjet, thermal, thermal transfer, and electrophotographic printers, all of which form an image using dots. When expressing pseudo-halftones with a printer, area gradation is used that expresses the intermediate temperature by the number of dots. However, the size of the dots formed depends on the printer method and type.
Since the dot pitch and density are different, the relationship between the number of dots used for area gradation and the density, that is, the gamma characteristic, is a value unique to each printer. Image reading and input devices perform processing assuming a specific gamma coefficient, so if a printer with a different gamma coefficient is used, there is a problem in that the output density from the printer will be different compared to the original.

The present invention solves the problems caused by the difference in gamma coefficients mentioned above, and provides a human-powered image reading device that performs pseudo-halftone binarization processing compatible with the gamma coefficients of the printer used.

[Means for solving the problems] In the present invention, as means for solving the above-mentioned problems,
A circuit that prints a test pattern using the printer used, measures its density, and applies optimal gamma correction was added to the human-powered image reading device.

[Operation] The gamma correction circuit of the present invention determines the gamma characteristic curve of the printer from the result of reading the density of the test pattern printed by the printer, and writes the gamma correction value to the gamma correction table from the curve.

[Examples] The present invention will be explained in detail in accordance with Examples. 1st
The figure is a circuit (14 diagram) of an image reading input device showing an embodiment of the present invention. The optical image of the original is converted into an electric signal by a photoelectric conversion circuit 1.
However, in the next A/D conversion circuit 2, it is converted into digital number 18 and quantized. This fostering quantizes to a level equal to or greater than the required number of gradations. In this example, floor 1!
Let 117 be 10. The quantized digital 1M number is usually gamma corrected LUT3 (lookup table)
The signal is passed through the binarization circuit 4 and converted into a binary digital number 18. The gamma correction LUT 3 is a tabular representation of the input/output relationship assuming a specific gamma correction curve. The binarization circuit 4 is a circuit for binarization for pseudo-halftone expression, and examples of binarization methods include dithering, multi-stage quantization, and minimum average error method. is known and used for N2. The binarized digital number 18 is outputted to the computer through the external output section 5. Further, in this embodiment, the data is directly output to the printer through the printer output unit 8.

Next, a gamma correction function (hereinafter referred to as gamma correction optimization function) tailored to the gamma characteristics of the printer to be used, which is an object of the present invention, will be explained. In the gamma correction optimization mode, first, the gradation pattern generation circuit 7 generates pattern No. 18 for each halftone using pseudo halftone expression, and outputs it to the printer through the printer output section 8, and the printer generates the pseudo halftone gradation. Print the tone pattern. FIG. 2 is an example of a pseudo halftone pattern, expressing 10 gradations.

The optical image of the printing result is transferred to charging conversion circuit 1 and A/D conversion circuit 2.
quantized by FIG. 3 is a gamma characteristic diagram.

The horizontal axis is human input data to the printer, which can be thought of as the gradations from O to 9 in FIG. The vertical axis is the reflectance of each gradation pattern or the area ratio of the white background. Normally(
Image processing is performed assuming the characteristics of (a), but if the printer used has the characteristics of (b), the overall print result will be whitish, and if the printer used has the characteristics of (c), the print result will be blackish. Next, read the output pseudo halftone pattern. FIG. 4 is a correct explanatory diagram of gamma t+Ii. It is assumed that the horizontal axis represents each gradation, and the vertical axis represents the normalized value of the A/D converted photoelectric conversion output value, resulting in a result as shown by a black circle, for example. The curve connecting these black circles is the gamma characteristic of the printer. Note that since the pseudo halftone pattern requires a certain width, the average value photoelectrically converted over the width is used. If a curve symmetrical with respect to this curve with respect to Y=X is found, this becomes the optimal gamma correction circuit. In this case, the horizontal axis is the A/D conversion value, and the vertical axis is f gamma corrections.

Color/Z can be considered as a way to obtain the Irk gamma correction curve, but for example, the black circles are simply replaced with the X and Y axes.

This is the point of the white circle. If this continues, there may be no white circle points that exactly match the Δ/D conversion value, so tili intervals are drawn between the white circle points. Linear interpolation is the simplest, but interpolation using spline curves can also be considered. The triangle mark is the interpolated point. This result is a gamma correction LUT
will be written to. The above is the explanation of the gamma correction optimization function.

In the present invention, the image reading input device is provided with a printer output section and a gradation pattern generation circuit, but these are not necessarily necessary, and even if software is prepared to print a pseudo gradation pattern using a computer's printer output, the same result can be achieved. Effects can be obtained.

[Effects of the Invention] According to the present invention, it is not affected by the gamma characteristics of the printer.
An image reading input device that performs optimal and constant image processing can be provided. Another advantage is that it does not require any changes to the mechanism, and can be handled by changing or adding circuits.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention. FIG. 2 is a diagram of a pseudo halftone gradation printing pattern. Figure 3 is a gamma characteristic diagram. FIG. 4 is an explanatory diagram of gamma correction. 1... Charging conversion circuit 2... A/D conversion circuit 3... Gamma correction L U 1' 4... Binarization circuit 5... External output section 6... Gamma correction circuit 7. ...Tone pattern correction circuit 8...Printer output section and above Applicant: Seiko Epson Corporation, 8 Agent: Patent Attorney Mogami 11! ! 1 person °
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Power A/D 1 Massage Grudge Figure 4

Claims (1)

[Claims] In an image reading input device that has a binarization processing function that enables pseudo halftone expression when converting optical information of a document into electromagnetic information using a photoelectric conversion means, a printing and recording device is used to convert optical information of a document into electromagnetic information in a predetermined format. An image reading/input device with a gamma correction function, characterized in that it reads printed output, automatically measures the gamma characteristics of the printing and recording device, and performs gamma correction compatible with the printing and recording device.