JPS60167571A - Color printer - Google Patents

Abstract

PURPOSE:To reproduce faithfully the color of an original picture regardless of the ground color of the printer paper by providing a means which detects the color of the printer paper and correcting the color signals to be printed by the output of said color detecting means. CONSTITUTION:A printer paper 1 is fed through paper feed rolls 6 and 7 and detected by a paper position detecting sensor 5. Then a paper position detecting sensor circuit 34 works, and a light emitting part 8 of a light emitting circuit 30 for paper color detecting sensor. Thus the paper 1 is irradiated. The reflected light of the paper 1 is received by photodetecting parts 9-11 of the paper color sensor. The output signals R', G' and B' are processed by a YMC conversion circuit 21 and a gamma correction circuit 22 and stored to a latch circuit 29 (in the form of Y', M' and C' signals). Changeover switches 26 and 27 supply the input signals R, G and B to the circuit 21 and connects the circuit 22 to a subtractor circuit 28 after a delay time produced by a delay circuit 32. While the circuits 30 and 28 are turned off respectively and on after a delay time of a delay circuit 33 to produce the difference signals between signals R, G and B and signal Y', M' and C' obtained by giving the YMC conversion to signals Y, M and C respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a color printing apparatus that can faithfully reproduce the colors of an original image regardless of the background color of a printing object such as printer paper.

(Background Art) Conventionally, in color printing devices such as color inkjet printers, a printing medium (hereinafter sometimes referred to as printer paper) is used.
If a color with a background color was used, the background color would be emphasized and the color of the original painting could not be faithfully reproduced. This is because conventional color printing devices do not have a means to control input signals in accordance with the color of the object to be printed. It was difficult to make high-quality prints by using the printer as a printer.

(Purpose) Therefore, the present invention provides a color printing device that can faithfully reproduce the colors of an original image regardless of the background color of the object to be printed.
The purpose is to enable high-quality printing even when paper is used.

(Explanation based on Examples) Hereinafter, the means taken in this invention to achieve the above object will be exemplified and explained with reference to the examples shown in the drawings. The following explanation will be made regarding an example in which the present invention is applied to an inkjet color printer, in the order of the configuration of the first embodiment of the present invention, its operation, and the second embodiment. Note that the present invention can also be applied to color printing devices other than inkjet printers.

(Configuration of the first embodiment of the color printing device of the present invention) (
(Figures 1 and 2) Figure 1 is a block diagram showing a printer paper detecting means as a color inkjet printer float which is an embodiment of the color printing apparatus of the present invention, and Figure 2 is a block diagram of the control system as well. It is. In these figures, 1 is a printer paper which is an example of a printing object, 2 is a platen, and 3 is a printer head.The printer paper 1 is fed into the apparatus in the direction of arrow A, and is wound around the platen 2. and printer head 3
The data is recorded and ejected from the device. In this example, printer paper 1 is fed and recorded one by one. b4 is a white reflective plate, 5 is a mechanical paper detection sensor which is an example of a paper position detection sensor, and 6.7 is a paper feeder. It's Laura. Reference numeral 8 denotes a light emitting section of a paper color detection sensor, and the emitted light irradiates the printer paper 1 that is being fed. Numerals 9 to 1 are light-receiving sections that receive light reflected by the printer paper 1, and output signals obtained by photoelectrically converting the red, green, and blue optical signals, respectively.
R', G' and B' signals) are output.

In FIG. 2, No. 2 is the input signal to be printed (R
, G, B signals) into Y, M, C signals; 22 is a gamma correction circuit; 23 is an undercolor removal circuit; 2
Reference numeral 4 denotes a masking circuit, and 25 denotes an 0D-V conversion circuit for converting an optical density signal into a voltage. Since the configuration and function of each of these circuits are well known, a detailed explanation will be omitted. Conventionally, the control system of a color printer essentially consists of the above circuit, and the output of the gamma correction circuit 22 is directly input to the undercolor removal circuit 23. On the other hand, in the embodiment shown in FIG. 2, various circuits described below are provided for correcting the input R1G and B signals based on the output of the printer paper color detection means.

To explain this specifically, 26 and 27 are interlocking changeover switches, which are simultaneously controlled by the output of a delay circuit 32, which will be described later. The changeover switch 26 receives R, G, and B signals which are input signals, and B/ and G/ which are the respective outputs of the light receiving sections 9 to 1 described above.

The B' signal is switched and inputted as described later, and the output of the gamma correction circuit 22 is inputted to the changeover switch 27. 28 is a subtraction circuit, which is a selector switch 2.
Subtraction processing is performed between the R, G, and B signals from 7 and the R', G', and B' @ signals stored in the latch circuit 29. 30 is a paper color detection sensor light emitting circuit which drives and controls the light emitting section 8. 31 to 33 are delay circuits, and their respective outputs cause the latch circuit 29, changeover switch 36.
11, subtraction circuit 28 and paper color detection sensor light emitting circuit 5
control each oik. Reference numeral 34 denotes a paper position detection sensor circuit, which is activated by the output of the paper position detection sensor 5.

(Operation of the first embodiment of the color printing device of this invention)
(Figures 1 and 2) When the printer paper 1 is fed between the feed rollers 6 and 7 and the paper position detection sensor 5 detects that the printer paper 1 has been fed (5), the paper position detection sensor circuit 34 is activated, its output is applied to the paper color detection sensor light emitting circuit 30, and the light emitting section 8 emits light to illuminate the printer paper 1 being fed. At the same time, the output of the paper position detection sensor circuit 34 is supplied to the delay circuit 31, and the latch circuit 29 is turned on. The interlocking changeover switches 26 and 21 firstly input the aforementioned R/ and σB/ times the signals to the changeover switch 26 into the MMC conversion circuit 21, and connect the gamma correction circuit 22 to the latch circuit 29. On the other hand, the light reflected by the printer paper 1 is received by the light receiving parts 9 to 11 of the paper color detection sensor, so the output R1°g/, B/multiple signal MMC
It is processed by the conversion circuit 21 and the gamma correction circuit 22 and stored in the latch circuit 29. Below, these signals are expressed as y/,
They are called M/ and C/ signals.

Next, after a delay time by the delay circuit 32 has elapsed, the changeover switches 26 and 27 input the input R, G, and B signals to the YMC conversion circuit 21, and convert the gamma correction circuit 22 to the subtraction circuit 21.
8.

During this time, the printer paper 1 continues to be fed, while the delay (6) circuit 33 determines the timing to start printing, uses its output to turn off the paper color detection sensor light emitting circuit 3o, turns off the light emitting unit 8, and performs subtraction. Turn on circuit 28, R, G, B
Y, M which converted the signal into YMC.

A difference signal is formed between the C signal and the aforementioned y/, M/, and c/ times signals (all of which have been gamma-converted). The output of the subtraction circuit 28 is sent to the under color removal circuit 23 and the masking circuit 2.
4 and 0D-V conversion circuit 25 in a known manner,
The output Y, M, C, BK double signals drive the printer head and start printing. Note that since the paper color detection sensor section shown in FIG. 1 uses a white reflection plate 4 as a reflection plate, OHP paper is automatically regarded as white, and printing can be performed on it. According to the embodiment described above, each time the printer paper 1 is fed, the color is detected for each printer paper, and the detection output is used to determine the input R1G, B.
Since the signal is corrected, even if paper with a background color or OHP paper is used, the background color of the paper is not emphasized and the colors of the original image can be faithfully reproduced.

Note that the present invention can be applied not only to a device that feeds printer paper one sheet at a time, but also to a device that feeds printer paper continuously.

(Second Embodiment of the Color Printing Apparatus of the Invention) In carrying out the invention, the paper position detection sensor (5 in FIG. 1) is used by utilizing the output of the paper color detection sensor as follows. can be omitted and the device can be simplified. That is, the light emitting section 8 of FIG. 1 is made to emit light in advance, the printer paper 1 is fed while detecting the outputs of the light receiving sections 9 to 11, and the timing at which the output of the light receiving sections 9 to NO changes is detected. As a result, a means for determining whether the printer paper 1 has been fed to a predetermined position in the apparatus is provided, and the above timing is regarded as the timing at which the paper position detection sensor 5 shown in FIG. 1 detects the printer paper 1. All you have to do is process it.

(Effects) As described above, according to the present invention, a detection means for detecting the color of the object to be printed is provided, and the color signal to be printed is corrected based on the appearance of the detection means, so that the color signal to be printed is corrected. The colors of the original image can be faithfully reproduced without emphasizing the ground color of the subject, and high-quality printing can be performed even when using printer paper or OHP paper with a certain ratio.

Note that the object to be printed is fed while monitoring the output of the detection means, and the timing at which the output of the detection means changes is assumed to be the timing when the object to be printed has been fed to a predetermined position in the apparatus, and subsequent processing is performed. According to this embodiment, the sensor for detecting the object to be printed, which is conventionally required, can be omitted and the apparatus can be simplified.

[Brief explanation of the drawing]

The drawings show an embodiment of the color printing apparatus of the present invention, and FIG. 1 is a block diagram of its main parts, and FIG. 2 is a block diagram of its control system. Explanation of symbols 1...Printer paper which is an example of a printing object, 4...
White reflector, 5... Paper position detection sensor, 8... Light emitting part of paper color detection sensor, 9 to 11... Also light receiving part, 26.2'i... Changeover switch, 28... Subtraction circuit, 29... Latch circuit, SO... Paper color detection sensor light emitting section (9) path, 31 to 33... Delay circuit, 34... Paper position detection sensor circuit. (10)

Claims (1)

[Scope of Claims] '(1) A color printing apparatus comprising: a detection means for detecting the color of an object to be printed; and a means for correcting a color signal to be printed based on the output of the detection means. (2) The color printing apparatus according to claim (1), further comprising means for activating the detection means each time an object to be printed is fed into the apparatus. (3) The color printing apparatus according to claim (1), further comprising means for determining whether the object to be printed has been fed to a predetermined position within the apparatus based on a change in the output of the detection means.