JPH0454423B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multicolor inkjet recording device,
In particular, it is possible to obtain a color recorded image that is more faithful to the original, regardless of the physical properties of the recording paper, recording liquid, etc. due to humidity.

In a multicolor inkjet recording device that reads an original color document and forms a color recorded image on a recording paper, etc., multicolor ink, for example, yellow, magenta, and cyan ink, is ejected from different inkjet nozzles. A color recorded image that is faithful to a color original is reproduced depending on the degree of overlapping of inks or the degree of arrangement of ink dots corresponding to each color. However, the yellow, magenta, cyan, etc. inks and recording paper used in this type of multicolor inkjet recording device are easily affected by temperature and humidity.In particular, the physical properties of the ink change depending on the temperature, and the ink on the recording paper The degree of bleeding depends on the size and water absorption of the recording paper due to humidity, so even if the recording is performed under the same recording conditions, the recorded images will differ depending on the temperature and humidity.

FIGS. 1 and 2 show the spectral reflectance of cyan, magenta, and yellow inks applied to high-quality paper under various temperature and humidity conditions and thoroughly dried. In Figure 1, solid line a shows the spectral reflectance characteristics when cyan ink is applied to high-quality paper under conditions of temperature T2℃ and humidity H1%, and solid lines b and c show the same conditions as solid line a. The spectral reflectance characteristics when magenta and yellow inks are applied are shown below. Also,
Broken line d indicates temperature T1℃ lower than temperature T2℃ and humidity H1
%, and the broken lines e and f show the spectral reflectance characteristics when magenta and yellow inks were applied under the same conditions as the broken line d. They are shown below. According to Figure 1, if the humidity is constant,
Images obtained by applying magenta and yellow inks at a certain temperature have spectral reflectance characteristics shifted toward shorter wavelengths than images obtained at higher temperatures, and cyan It can be seen that the lower the temperature of the ink, the higher the density.
Note that, from these facts, the overall image obtained by overlapping each ink becomes an image shifted to the shorter wavelength side as the temperature is lower.

In addition, in Fig. 2, the solid line g is the temperature T2℃,
It shows the spectral reflectance characteristics when cyan ink is applied under the condition of humidity H1%, and solid lines h and i show the spectral reflectance when magenta and yellow ink are applied under the same conditions as solid line g. Each shows its characteristics. Furthermore, dashed line j shows the spectral reflectance characteristics when cyan ink is applied under the conditions of temperature T2℃ and humidity H2% higher than humidity H1%, and dashed line k shows the spectral reflectance characteristics under the same conditions as in the case of broken line j. It shows the spectral reflectance characteristics when magenta and yellow inks are applied. From Figure 2, it can be seen that when each ink is applied at a constant temperature in an atmosphere with different humidity, the image of each ink obtained under conditions of higher humidity is different from that obtained under conditions of lower humidity. It can be seen that a spectral reflectance characteristic in which the slope of the slope of the spectral characteristic is steeper and short wavelengths are emphasized is obtained as compared to the image obtained with the spectral characteristic.

In this way, when forming a color recorded image by ejecting cyan, magenta, and yellow inks onto recording paper under different conditions of temperature and humidity, even though the same color original is used, If the humidity is lower than the specified humidity determined depending on the ink and recording paper used, a reddish image may be obtained, and conversely, if the humidity is increased, a bluish image may be obtained. The inventor has discovered that this can occur.

Therefore, an object of the present invention is to provide a multicolor inkjet that can eliminate the above-mentioned drawbacks and reproduce recorded images with more faithful tones to color originals without being affected by changes in the physical properties of recording paper due to changes in humidity. The purpose is to provide a recording device.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 3 shows an example of the configuration of the multicolor inkjet recording apparatus of the present invention, where 1 is a drum around which a color original 2 and recording paper 3 are wound, and 4 is a drum 1.
This is a drive motor for rotating. 5 is a reader that scans and reads the color original 2, and separates the light from the color original 2 into each color component of blue (B), red (R), and green (G), and calculates the amount of reflected light of each color component. The difference in the current value is interpreted as a change in the current value. That is, the reader 5 is red,
It has a photo sensor that detects blue and green light respectively, detects a spot usually about 60 μm in size that forms an image on a color document, and outputs document color component signals corresponding to red, blue, and green, respectively. 6 is an inkjet nozzle, and in this example, cyan, magenta,
Consisting of three nozzles corresponding to each color of yellow,
A recorded image is formed on the recording paper 3 by ejecting cyan (C), magenta (M), and yellow (Y) inks from each nozzle.

Reference numeral 7 denotes a support base to which the reader 5 and the inkjet nozzle 6 are fixed. Two sliders 8 are attached to this support stand 7, and the support stand 7 can move left and right on the rail 9 via the slider 8, so that the reader 5 and the inkjet nozzle 6 are interlocked to move left and right. be able to move. That is, the pulse motor 10 is installed at one end of the drum 1.
A pulley 11 is fixed to the output shaft of the pulse motor 10. Further, a pulley 12 is disposed on the other end side of the drum 1, and a pulley 12 is provided between the pulley 11 and the pulley 12 for moving the support base 7 parallel to the rotation axis 1A of the drum 1. The wire 13 is stretched. The wire 13 is fixed to the retaining plate 14, thereby connecting it to the support base 7. By driving the pulse motor 10, the wire 13 is driven, and the support base 7 is capable of linearly reciprocating in the direction of the rotation axis 1A of the drum 1.
Therefore, due to the rotation of the drum 1 itself and the linear movement of the reader 5 and inkjet nozzle 6 in the direction of the rotation axis 1A, the reader 5 and inkjet nozzle 6 read the original color document 2 and the recording paper 3. This means that the entire surface can be scanned in both the horizontal and vertical directions.

15 is a temperature detector, for example a thermistor;
It has the temperature resistance value characteristics shown in FIG. That is, the resistance value decreases as the temperature increases. 1
Reference numeral 6 denotes a humidity detector, for example, Hume Serum (trade name: manufactured by Matsushita), which has the humidity resistance value characteristics shown in FIG. That is, the resistance value decreases as the relative humidity increases. 17 is a color signal correction control circuit to which the color component signal of the color original 2 read by the above-mentioned reader 5, the temperature detection signal detected by the temperature detector 15, and the humidity detection signal detected by the humidity detector 16 are supplied. , the color component signal is corrected and converted based on the temperature detection signal and the humidity detection signal, and the recording color component signal is supplied as a nozzle drive signal to the inkjet nozzle 6 via a drive circuit described later with reference to FIG. Controls the inkjet nozzle 6. As a result, cyan, magenta, and yellow ink droplets are ejected from the inkjet nozzle 6, and a recorded color image is formed on the recording paper 3 by subtractive color mixing.

FIG. 6 shows the color signal correction control circuit 1 shown in FIG.
7, the details of the reader 5, the temperature detector 15 and the humidity detector 16 are shown, where 110 to 112 are:
The reader 5 is configured with a photo sensor for detecting red, green, and blue light, respectively, and detects changes in the amount of reflected light of each color component of red, green, and blue in the color original 2 as a change in photocurrent. This is to obtain red, green, and blue color component signals. 113-115
are preamplifiers that convert photocurrent signals obtained by photo sensors 110 to 112 into voltage signals and amplify them, and supply them to one input terminal of gain correction circuits 119 to 121 via resistors 116 to 118, respectively. . The other input terminals of the gain correction circuits 119-121 are connected to the ground potential via resistors 122-124.

122 is a temperature detector having the characteristics shown in FIG. 4, and corresponds to the detector 15 in FIG. 3. A preamplifier 123 amplifies changes in the voltage signal due to changes in the resistance value of the temperature detector 122. 124 is the fifth
This is a humidity detector having the characteristics shown in the figure, and corresponds to the detector 16 in FIG. This humidity detector 124
A preamplifier 125 amplifies a change in the voltage signal due to a change in the resistance value of the preamplifier 125 . Note that a predetermined potential Vet is applied to these temperature detector 122 and humidity detector 124. These preamplifiers 123
The temperature detection signal and humidity detection signal amplified by and 125 are supplied to respective terminals of an arithmetic circuit 126, and a control signal A corresponding to the detected temperature and humidity is supplied to each of amplifier circuits 127-129. The arithmetic circuit 126 calculates that when the output signal of the preamplifier 125 corresponding to the humidity increases, that is, when the humidity increases, the output signal A decreases, and when the output signal of the preamplifier 123 corresponding to the temperature increases, that is, when the humidity increases, the output signal A decreases. , the output signal A is configured to increase as the temperature increases. In addition, the amplifier circuit 1
27 is configured such that its output voltage increases when the input signal A decreases (humidity increases or temperature decreases), and its output voltage decreases when the input signal increases (humidity decreases or temperature increases). On the other hand, the amplifier circuit 129 is configured such that when the input signal A decreases, its output voltage decreases, and when the input signal A increases, its output voltage increases. It is assumed that the amplifier circuit 128 generates a substantially constant output based on the input signal A.

130-132 are gain correction circuits 119-1
These are MOS type field effect transistors (hereinafter referred to as MOSFETs) inserted in each of the 21 feedback circuits. The gates of these MOSFETs 130 to 132 are connected to the aforementioned amplifier circuits 127 to 129.
Apply the output voltage of each. The amplification factors of the gain correction circuits 119 to 121 are the same as those of each of these MOSFETs.
determined by a resistance value of 130 to 132,
It increases as the resistance value of MOSFETs 130 to 132 increases. Therefore, the amplification factors of the gain correction circuits 119 to 121 change depending on the ambient temperature or atmospheric humidity, and the color component signals R, G, and B input to the gain correction circuits 119 to 121, respectively, are changed depending on the temperature or humidity. Each is amplified with an amplification factor depending on .

Reference numeral 133 denotes a color signal calculation unit, which receives the corrected color component signals R, G, and B of analog values from the gain correction circuits 119 to 121, and executes the following calculation to obtain the color component signals R, G, and B. Ink ejection signal C ₀ ,
Convert to M ₀ and Y ₀ .

C ₀ M ₀ Y ₀ = a ₁₁ , −a ₁₂ , −a ₁₃ −a ₂₁ , a ₂₂ , −a ₂₃ −a ₃₁ , −a ₃₂ , a ₃₃ R G B However, a ₁₁ 〜 a ₃₃ >0 These Each signal C ₀ , M ₀ , Y ₀ is supplied to the ink jet nozzle 6 shown in the third figure via ink jet nozzle drive circuits 134-136. At this time, the signal actually supplied is the inverted version of the above calculation result, and if the calculation result is negative, it is set to 0 and then inverted.

For example, in the above calculation formula, R>0, G=B
= 0, the calculation result is C ₀ = a ₁₁ R>0, M ₀ =-
a ₂₁ R<0, Y ₀ = -a ₃₁ R<0, and if we perform processing to set the negative signal to 0, C ₀ = a ₁₁ R, M ₀
=0, Y ₀ =0. After that, we perform a reversal, but
This inversion means that the luminance signals R, G, B are maximum/minimum (=
0), the density signals C ₀ , M ₀ ,
Y ₀ is converted to have the minimum (=0)/maximum density. Of course, if the luminance is an intermediate value, the inverted density will also be an intermediate value. Therefore, in the above example, when R is the maximum brightness, the signal after inversion becomes C ₀ ′=0, M ₀ ′=Y ₀ ′=maximum density,
Cyan ink will not be ejected. In addition,
In the following explanation, it is assumed that the signals subjected to the above-mentioned inversion and other processing are treated as C ₀ , M ₀ , and Y ₀ .

Ink droplets corresponding to each signal obtained as described above are ejected from each inkjet nozzle 6. As a result, a recorded and reproduced image is formed on the recording paper 3.

In the multicolor inkjet recording apparatus constructed as described above, suppose that in an atmosphere of temperature T2°C shown in FIG. 4 and humidity H1% shown in FIG. 5, only the humidity becomes high and rises to humidity H2%. At this time,
As can be seen from FIG. 5, the resistance value of the humidity detector 124 decreases from RH1 to RH2, and the preamplifier 1
25's output voltage increases. As a result, the output signal A of the arithmetic circuit 126 decreases as described above, so the output voltage of the amplifier circuit 127 increases and the output voltage of the amplifier circuit 129 decreases. At the same time, the resistance value of the MOSFET 130 to which the output voltage of the amplifier circuit 127 is applied to the gate decreases, and the output voltage of the amplifier circuit 129 is applied to the gate.
The resistance value of MOSFET 132 increases.
The resistance value of MOSFET 131 hardly changes because its gate input voltage is almost constant. In this way, the amplification factor of the gain correction circuit 119 decreases, the amplification factor of the gain correction circuit 120 remains almost constant, and the amplification factor of the gain correction circuit 121 increases, so that the gain correction circuits 119 to 121 each output The color component signals R, G, and B are as follows: R (humidity H2%) < R (humidity H1%) G (humidity H2%) G (humidity H1%) B (humidity H2%) > B (humidity H1%) The ink ejection signals C ₀ , M ₀ , and Y ₀ calculated based on these signals R, G, and B are as follows: C ₀ (humidity H2%) < C ₀ (humidity H1%) M ₀ (humidity H2%) M ₀ (Humidity H1%) Y ₀ (Humidity H2%) > Y ₀ (Humidity H1%). Therefore, in the ink ejection signals C ₀ , M ₀ , and Y ₀ output from the color signal calculator 133, the higher the humidity is at a certain temperature, the more the long wavelength range is emphasized, and the short wavelength range is suppressed. Here, the ink ejection signals C ₀ , M ₀ , and Y ₀ are supplied to the ink jet nozzle 6 (see FIG. 3) via the ink jet nozzle drive circuits 134 to 136 to increase the humidity. Accordingly, the number of recorded dots per unit area is controlled to form a recorded image that emphasizes the long wavelength region.

Next, it is assumed that in the atmosphere with the temperature T2°C shown in FIG. 4 and the humidity H1% shown in FIG. 5, only the temperature becomes higher and rises to the temperature T2°C. At this time, the fourth
As can be seen from the figure, the resistance value of the temperature detector 122 decreases from RT1 to RT2, and the resistance value of the temperature detector 122 decreases from RT1 to RT2.
The output voltage of increases. As a result, the arithmetic circuit 12
Since the output signal A of 6 increases as described above,
The output voltage of the amplifier circuit 127 decreases, and the output voltage of the amplifier circuit 127 decreases.
The output voltage of 29 increases. MOSFET 13 to which the output voltage of the amplifier circuit 127 is applied to the gate
The resistance value of MOSFET 132 increases, and the resistance value of MOSFET 132, whose gate is applied with the output voltage of amplifier circuit 129, decreases. Therefore, the gain correction circuit 119
Since the amplification factor of the gain correction circuit 121 increases and the amplification factor of the gain correction circuit 121 decreases, the gain correction circuits 119 to 12
Color component signals R, G, B each output from 1
is R (temperature T2℃) > R (temperature T1℃) G (temperature T2℃) G (temperature T1℃) B (temperature T2℃) < B (temperature T1℃), and these signals R, G, B _The ink ejection signals _{C 0} , M _{0 , and} Y ₀ calculated based _on Temperature T2℃) < Y ₀ (Temperature T1℃). Therefore, in the ink ejection signals C ₀ , M ₀ , and Y ₀ outputted from the color signal calculator 133, the higher the temperature under constant humidity, the more the short wavelength range is emphasized and the long wavelength range is suppressed. Here, the ink ejection signals C ₀ , M ₀ , Y ₀ are supplied to the ink jet nozzle 6 (see FIG. 3) via the ink jet nozzle drive circuits 134 to 136 to increase the temperature. Accordingly, the number of recorded dots per unit area is controlled to form a recorded image that emphasizes the short wavelength region.

In this example, as the temperature rises and humidity falls, the ejection of each ink is controlled so as to emphasize short wavelengths, and as the temperature falls and humidity rises, the ejection of each ink is controlled so as to emphasize long wavelengths. Since the ejection is controlled, a recorded image that is more faithful to the color original can be obtained.

Note that in this example, the correction of the recorded image density was controlled by the number of recorded dots per unit area of each color, but in the present invention, a plurality of nozzles with different orifice diameters are used for the same color, When ejecting ink, the color density of a recorded image can also be controlled by ejecting ink from appropriately selected nozzles. In addition, the color density of the recorded image can be controlled by using a plurality of nozzles that eject color ink of different densities for the same color, and by appropriately selecting these plurality of nozzles.
Any form of color density control may be used during recording.

As explained above, according to this embodiment, the original color component signals are converted into temperature detection signals and humidity detection signals corresponding to the temperature and humidity detected by the temperature detector that detects the ambient temperature and the humidity detector that detects the ambient humidity, respectively. Each signal is amplified by an amplification factor based on the signal, and the corrected color component signal amplified by each amplification factor is converted into an ink ejection signal to form a recorded image, so changes in ink physical properties due to temperature changes, It is possible to prevent variations in recorded images due to changes in the mixing ratio of ink compositions such as dyes and pigments, changes in recording paper size and water absorption due to changes in humidity, etc., and it is possible to obtain recorded color images that are more faithful to the original. .

As explained above, according to the present invention, a corrected color signal corrected according to the detected atmospheric humidity is converted into an ink ejection signal, so it is possible to prevent variations in recorded images due to changes in humidity, and to produce high-quality images. can be obtained.

In particular, according to the present invention, the relatively short wavelength components of the color component signal are emphasized when the humidity decreases, and the relatively long wavelength components are emphasized when the humidity increases. To obtain an inkjet image faithful to the original and excellent in color reproducibility by preventing an inkjet image with a shading or a bluish inkjet image from being obtained due to increased humidity.

[Brief explanation of drawings]

FIGS. 1 and 2 are spectral reflectance characteristic curve diagrams of recorded images formed on recording paper using each ink,
FIG. 3 is a block diagram showing an example of the structure of the multicolor inkjet recording apparatus of the present invention, FIG. 4 is a characteristic curve diagram of the temperature detector shown in FIG. 3, and FIG. 5 is a characteristic curve of the humidity detector shown in FIG. 3. 6 are block diagrams showing detailed examples of the color signal correction control circuit, reader, temperature detector, and humidity detector shown in FIG. 3, respectively. 1...Drum, 2...Color original, 3...Recording paper, 4...Drive motor, 5...Reader, 6...Inkjet nozzle, 7...Support stand, 8...Slider, 9... Rail, 10...Pulse motor, 1
1, 12...Pulley, 13...Wire, 14...
Retaining plate, 15...Temperature detector, 16...Humidity detector, 17...Color signal correction control circuit, 110-11
2...Photo sensor, 113 to 115, 123,
125...Preamplifier, 116-118, 122
~124...Resistor, 119-121...Gain correction circuit, 126...Arithmetic circuit, 127-129...
...Amplification circuit, 130-132...MOS type field effect transistor, 133...Color signal calculator, 13
4-136...Drive circuit.

Claims (1)

[Scope of Claims] 1. A multicolor inkjet recording device that drives inkjet nozzles to form a recorded image on recording paper based on a given color component signal, comprising: a humidity detector that detects atmospheric humidity; Based on the humidity detection signal corresponding to the humidity detected by the humidity detector, it automatically emphasizes relatively short wavelength components when humidity decreases, and emphasizes relatively long wavelength components when humidity increases. In order to
a circuit that corrects the color component signal to obtain a corrected color component signal; and a conversion circuit that converts the corrected color component signal into an ink ejection signal, and drives the inkjet nozzle based on the ink ejection signal. A multicolor inkjet recording apparatus characterized in that a recorded image is formed on the recording paper by