JP3004338B2 - Image processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to an image processing apparatus that performs color processing in consideration of a shot amount.

[Prior art]

In a conventional color copying apparatus using an ink jet recording method, the color reproduction range is determined by the resolution of the head or the like of the paper or ink (dye or the like) used for printing or the recording section, and the masking coefficient and γ in image processing are determined. Use image coefficients such as correction and offset that are uniquely optimized based on the color difference from the target reproduction color (対 象 Lab) and the amount of ink applied to recording paper (g / mm ² ). ing. However, with the development of peripheral devices and option devices in recent years, not only reflection originals but also positive / negative films,
Some devices, such as VTRs and personal computers, which are configured to output an optimal color image by switching an image coefficient in image processing by an image input device so as to be able to capture and output an image signal. Also, in order to be able to respond to the diversification of output paper, for example, various output papers are used to perform image processing suitable for recording on various output papers such as heavy coated paper, light coated paper, plain paper, OHP film, etc. Switching to a corresponding image coefficient to provide an optimal color image has also appeared.

[Problems to be solved by the invention]

However, in the above conventional example, as described above, the image coefficient is uniquely determined for various input devices and various types of paper from the relationship between the color difference between the reproduced color of the color sample to be compared and the amount of ink applied. I was wearing it. For this reason, for the average color original, satisfactory results were obtained for both the color difference and the ink ejection amount.
In order to change the overlap of M and Y inks to K ink by inking (UCR), when trying to reduce the amount of ink applied, the color difference generally increases (especially the brightness decreases) in the relationship between the color difference and the amount of ink applied. ). In addition, since the ink ejection amount is determined by the recording paper, the image coefficient is uniquely determined by the ink ejection amount (the image difference that minimizes the color difference while satisfying the ink ejection amount). Is determined by the coefficient). Therefore, when a color original having a high lightness L is output, the color difference from the original increases. Conversely, when outputting a color original with low lightness L,
Occurrence of streaks due to unevenness of the paper (e.g., click ringing) and bleeding of the ink (e.g., bleeding) was observed, giving the user discomfort. Further, in the case of an OHP film, the above-mentioned phenomena tended to appear remarkably due to a transmission image transferred through the OHP film. In addition, when a place having a high brightness and a place having a low brightness are mixed in the original, the above-mentioned phenomenon is particularly remarkable. In the case of a serial type device as shown in FIG. 10, the above-described phenomenon particularly occurred at a serial connection portion.

[Means for Solving the Problems]

SUMMARY An advantage of some aspects of the invention is to solve the above-described problems, and the invention has the following configuration as a means for solving the above-described problems. That is, an image processing apparatus that converts input image information into image information suitable for a recording apparatus that records a color image, and a ratio detecting unit that detects at least one of an image ratio and an image density ratio of an input image signal. And image processing means for performing image processing on the input image signal based on a balance image coefficient between the color reproducibility and the shot amount in the recording device with respect to the detection ratio of the ratio detection means. For example, the image processing apparatus further includes a dividing unit for dividing the input image information into predetermined regions, and performs the above-described processing separately for each divided region by the dividing unit. Further, for example, the recording apparatus performs recording by causing a state change such as film boiling in the ink by thermal energy to generate bubbles, and discharging the ink from a discharge port using the bubbles. It is characterized by. Alternatively, an image processing apparatus for inputting a color image and performing color processing, a storage unit for storing a color condition for emphasizing color reproducibility and a color processing condition for emphasizing a shot amount, and an input unit for inputting a color image Selecting means for selecting a color processing condition corresponding to the color image from the color processing conditions stored in the storage means; and a color for performing color processing on the color image using the color processing condition selected by the selecting means. And processing means.

【Example】

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, an example in which the present invention is applied to a digital color copying apparatus using an ink jet recording method will be described.

FIG. 1 is a block diagram of an embodiment according to the present invention. In FIG. 1, reference numeral 1 denotes a photoelectric conversion element for performing optical-electrical conversion of an image of an input document for each of RGB color components. Some resolution 400d
A line type CCD of pi, 2 is an A / D conversion circuit for converting R, G, B analog signals from the CCD 1 into 8-bit digital signals, and 3 is a shading section for correcting white and black data. A white / black correction circuit, 4 a black character detection circuit for detecting black characters in the original, 5 a logarithmic conversion circuit for converting a luminance (light) signal (RGB) into a density signal (CMY), 6 a color reproduction and an ink ejection amount Masking / UCR (inking) circuit for deciding color, 7 is a gamma correction / offset circuit for correcting density gradation and fog, 8 is multi-valued data (8 bits) and binary data (0, 1). Signal). Reference numeral 9 denotes a black character processing circuit for performing black character processing on a black character portion detected by the black character detection circuit 4. Reference numeral 10 denotes an input of an RGB image signal from the white / black correction circuit 3, and the image ratio and image density for the entire input range are determined by R · R. Calculate for each G / B color,
An image ratio detecting circuit 11 for making a judgment for optimizing the image coefficient, 11 is an image coefficient converting circuit for calculating or switching the image coefficient according to the condition judged by the image ratio detecting circuit 10, and 15 is a CPU, ROM , A control unit for controlling the entire copying apparatus of the present embodiment, and an operation unit 16 for inputting various instructions. Reference numeral 20 denotes a printer unit for performing ink jet recording. An image processing operation by the press-can method of the present embodiment having the above configuration will be described below with reference to the flowchart of FIG. The control unit 15 copies the operation unit 16 in step S1.
Monitor the input of SW. When the copy SW of the operation unit 16 is input, the process proceeds from step S1 to step S2, and the image reading unit (CCD1) of the reader presses the R while the image reading unit (CCD1) performs R by the image ratio circuit 10 in step S3.
Calculation of image ratio (calculation of duty (%)) for the entire range of each color of G and B (however, each of R, G, and B counts for a density level of 128 or less) and, at the same time, calculation of image density (Calculation of the maximum ink ejection amount V _max (g / mm ² ) expected from the signal values of each of R, G, and B)
Perform Here, the image ratio = ｛the total count × 100
(%)｝ / {Total number of pixels (reader signal)}, image density (average) = (sum of the density of each pixel) / (total number of pixels), maximum ink ejection amount V _max (g / mm ² ) = (number of colors) × V (p
l / dot) × n (dot / mm ² ). Then, in step S4, as a result of the calculation in step S3, it is checked whether it is necessary to change the image coefficient. If there is no need to change, the process proceeds to step S6. If there is a need to change, the process proceeds to step 5 from step S4. This determination is made by ascertaining the characteristics of the document from the results of and in step S3. The determination for changing the image coefficient is based on the “criterion 1” shown in FIG. 3A according to the image ratio, and the “determination criterion” shown in FIG. 3B according to the image density. For example, based on “2”, for example, an image coefficient “a” emphasizing color reproduction (when the brightness L is relatively high), an image coefficient “b” emphasizing the amount of ink ejection (when the brightness L is relatively low), and color reproduction / ink injection Image coefficient c that is compatible with the amount (when black characters and natural images are mixed)
Judgment is made instantly as in In FIG. 3A, the image ratio is counted as “1” when R + G + B ≧ 1.5, and as “0” when R + G + B <1.5. In step S5, the used image coefficient is calculated according to the above judgment, and the image coefficient is switched to the calculation result. In this embodiment, three kinds of masking coefficients in the calculation of the used image coefficient by the image coefficient switching type and the color difference (△ La) of the contrast color 76 by the simulation at that time are used.
The maximum ink ejection amount V _max data by b) Data and R · G · B signal shown in Figure 4. In FIG. 4, the color difference between the original and the simulation, which is the difference between the color reproduced by the simulation (△ Lab), and the color difference between the original and the simulation, and the color difference between the reproduced color obtained by recording the result is about one. It is known that there is a difference and the color reproducibility of actual recording is poor. However, since the tendency of the simulation and the tendency of the actual recording showed a good match, the result of the simulation is shown here. Murakami CA-35 was used for color measurement. When the calculations and the like are performed in this manner, the image coefficients (masking coefficient, γ correction, offset, etc.) are determined in step S6, and the determined image coefficients are set in each circuit.
Shifts to a normal copy operation. Thereafter, as shown in step S8, image processing according to the determined image coefficient is performed, and a recording image signal is output to the printer unit 20 for recording. Note that the processes in steps S7 and S8 are well known as long as the image coefficients are given, and therefore detailed description is omitted. Using the three types of image coefficients a, b, and c shown in FIG. 3, the image ratio / density detection / image coefficient switching devices 10 and 11 of this embodiment are added and removed. Various color originals were output to examine the effect of this embodiment. As a result, when the image ratio / density detection / image coefficient switching devices 10 and 11 of the present embodiment are added, especially in the case of a document having a high brightness L and a document having a low brightness L, compared with a device similar to the conventional device which is not added. It was confirmed that there was no adverse effect due to the improvement in color reproducibility and the increase in the amount of applied ink, and the switching could be performed smoothly. By the way, in the case of the conventional type apparatus which does not add the image ratio / density detection / image coefficient switching devices 10 and 11, the image coefficient c is inputted. FIG. 5 shows the color reproduction range of the ink jet recording apparatus, which is the printer unit 20 in this embodiment, by the above operation. FIG. 6 shows the difference between the original and actual reproduction color spaces based on the image coefficients of this embodiment. The above description has been made with an example in which a press scan is performed using a line CCD having a resolution of 400 dpi.
In the case of performing the pre-scanning, it is desirable to implement a pre-scanning method that can make an appropriate judgment by a method that does not take much time in the pre-scanning, such as the oblique scan. Next, the configuration of the printer unit 20 shown in FIG. 1 will be described. FIG. 8 is a perspective view of the vicinity of a head of an ink jet recording apparatus using a heating element. In the same figure, reference numeral 51 denotes a head unit, and nozzles 52 are yellow, magenta, cyan,
There are a total of four black. 53 is an ink supply tube, 54
Is the main tank. The configuration of the nozzle 52 is shown in FIG. 55 is an upper plate, 56 is a bottom plate, 57 is a heating element, 58 is an orifice portion, and 59 is ink. When a voltage is applied to the heating element 57, heat is generated, and bubbles are formed around the element 57. When the application of the voltage is completed, the bubbles shrink. The ink near the orifice portion 58 is ejected from the orifice portion 58 in accordance with the formation and contraction of the bubble. The recording head generates a state change such as film boiling in the ink by thermal energy to generate a bubble, and the ink is discharged from a discharge port (nozzle) to a recording material using the valve. This is a so-called bubble jet type recording head that discharges characters and records characters and images.
In this recording head, the size of a heating resistor (heater) provided in each nozzle is much smaller than that of a piezoelectric element used for conventional ink jet recording, so that high-density multiple nozzles can be provided. High quality recorded images can be obtained, and it has characteristics such as high speed and low noise. In FIG. 10, reference numeral 101 denotes a head unit in which a number of ink jet heads are arranged in the sub-scanning direction for one type of colorant, and has black, yellow, cyan, and magenta units. Reference numeral 107 denotes an ink tank for each head unit, 109 denotes a signal line, and 104 denotes a carriage drive motor for moving a carriage 105 having the head unit attached thereto along a rail 103 in cooperation with a transport belt 105. 106 is a recording paper, 120 is a platen, 111 and 112 are recording paper transport rollers, 113 is a recording paper roll, and 114 is a guide roller. The head unit 101 is composed of a plurality of ink jet heads using the heating elements shown in FIG. 9, but of course, an ink jet head using electromechanical conversion means such as a piezo element can also be used.

Second Embodiment The above description has been given of the image processing by the press-key method, but the present invention is not limited to the above example. Utilizing real-time feedback
A second embodiment according to the present invention will be described below with reference to a flowchart shown in FIG. Also in the case of the second embodiment, first, in step S11, it is monitored that the copy switch of the operation section 16 is pressed down, and when the copy switch is inputted, step S12 is performed.
The scanning of the image reading unit (CCD) of the reader is started, and the image signal (8 bits for each of R, G, and B) is transmitted in the next step S13.
The image data is input to image input processing units such as the A / D converter 2 and the white / black correction circuit 3. In this embodiment, a real-time feedback is performed by using a serial CCD that reads 128 pixels at a resolution of 400 dpi and a scanning speed (drive frequency) of 4 KHz. However, even if a line-type CCD is used, it can be realized even if the signal processing speed is increased, or a sweepback is performed using a temporary memory. By having a line memory for one scan, such processing becomes possible. In this way, the image signal from CCD1 is repeatedly sent to the image input processing unit as serial data of 128 pixels,
In this case, the image is divided in a certain pixel unit (area) by the image dividing unit 12 indicated by a one-dot chain line in FIG. In this embodiment, 128 pixels × 128 scans [about 8.125 × 8.125
(Mm ² )] unit, and the following steps S14 to S17 are performed for each of the divided block units.
Is determined. The processing of steps S14 to S17 is the same as the processing of steps S3 to S6 of the first embodiment described above.
The image ratio and the image density are calculated in the same manner as in the first embodiment, and the optimum image coefficient is determined (determined) for each block.
I do. Then, the process proceeds from step S17 to step S18 to check whether or not the image coefficients have been determined for all the divided blocks. If there is a block for which the image coefficient has not yet been determined, the flow returns to step S13 to execute the next block division and the image coefficient determination processing for the divided block. When all the image coefficients are determined in this manner, the process proceeds from step S18 to step S21, and the image coefficients determined for each block are set in each processing circuit. Then, in step S22, image processing according to the determined image coefficient is performed for each block, and recorded and output from the printer unit 20. In this case, the image processing for each block area is performed using the previously determined image coefficient for each block. As described above, according to the second embodiment, for example, A4
A document (about 203 × 284 mm ² ) is divided into about 875 blocks, and the entire image is recorded while processing each block. By performing this process, there has been a wide variety of color originals having a very wide contrast range up to now, and the determination of the image coefficients by the press key of the first embodiment has an overall balance. However, if emphasis is placed on color reproduction for the image coefficient in a portion having a high density, the amount of ink to be applied in a high portion is increased, and there is a possibility that cockling or bleeding may occur as an adverse effect, which can be effectively prevented. In particular, even in the serial scan method, the above-described phenomenon is adversely affected at the connection portion of the serial, and a connection streak composed of black streaks does not occur, and image recording with high image quality can be performed. As an example of a document, splicing streaks composed of black streaks are likely to occur particularly in people with black hair, but according to the second embodiment, these can be effectively prevented. In general, reproducibility of human skin color is particularly important. Conventionally, when importance is placed on color reproduction, streaks are generated in black hair. However, as in the second embodiment, by optimizing the image coefficients for each image block, it is possible to form an image with good color reproducibility even within one document and without any adverse effect due to an increase in the amount of ink applied. This was confirmed by an example. In the above description, the image is divided into 128 × 128 pixels. However, it is desirable to optimize the divided area according to changes in resolution, processing speed, and the like.

[Other embodiments]

In the above description, the case where the printer unit 20 is of the ink jet recording system has been described. However, the present invention is not limited to the above recording system, and other color recording systems such as a dot print system, a thermal transfer system, and an electrophotographic system are used. Is similarly applicable. In addition, the present invention is not limited to a copying machine, and can be similarly effectively applied to general digital color image processing. For example, the present invention can be applied to a wide range of image processing such as a processing order, various image coefficients, a binarization processing method, and edge / smoothing processing. Furthermore, it can be applied to both serial / line systems,
The present invention can be similarly applied to a connection process of a serial connection portion. Furthermore, the feedback method for changing the image coefficient is as follows.
Either pre-scan or real-time can be applied effectively. Instead of directly calculating the image ratio or the image density ratio, another parameter that changes according to the image density may be used. That is, for example, since the above-described printer 20 uses a head using thermal energy, it is considered that the temperature of the head is related to the image density. Therefore, the image density may be detected by measuring the head temperature. Further, the printer is not limited to the binary printer, but may be a multi-value printer. The input image signal is not limited to R, G, and B, but (Y,
I, Q), (L *, a *, b *). In this case, the image density can be evaluated using luminance Y and lightness L *. As described above, at the time of inputting a color original, a circuit that determines at least the image ratio (print duty) and the image density ratio of the original to determine the balance between color reproduction and ink ejection amount, Thus, by combining with a circuit for calculating or switching image coefficients (masking coefficient, γ, offset, etc.), optimum color reproducibility for various color originals and high image quality without adverse effects due to an increase in ink ejection amount are obtained. An ink jet recorded image can be provided. In particular, it is effective as a countermeasure against a connecting streak generated at a connecting portion of a serial type.

【The invention's effect】

As described above, according to the present invention, it is possible to prevent a decrease in the image quality of an output image due to an increase in the shot amount, and obtain a good output image.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment according to the present invention, FIG. 2 is an operation flowchart of the embodiment, and FIG. 3 (A) is a calculation example of an image ratio and how to change an image coefficient in the embodiment. FIG. 3 (B) is a diagram showing an example of a criterion for judging whether or not the image density is calculated in this embodiment, and FIG. 4 is a diagram showing an example of a criterion for judging whether to change the image coefficient. Each image coefficient and color difference (△ Lab),
FIG. 5 is a diagram showing the relationship between the ink ejection amounts, FIG. 5 is a diagram showing the color reproduction range of the ink jet recording apparatus used in this embodiment, and FIG. FIG. 7 is a flowchart showing the operation of the second embodiment according to the present invention, and FIGS. 8 to 10 are views for explaining the printer 20. In the drawing, 1 ... CCD, 2 ... A / D converter, 3 ... White / black correction circuit, 4 ... Black character detection circuit, 5 ... Log conversion circuit, 6
... Masking / UCR circuit, 7 .gamma. / Offset conversion circuit, 8 binarization circuit, 9 black text processing circuit, 10
... Image ratio detection circuit, 11 ... Image coefficient conversion circuit, 12 ...
An image dividing circuit, 15... A control unit, 16... An operation unit, 20... A printer unit.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiromitsu Hirabayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Atsushi Arai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-2-3365 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41J 2/01

Claims (4)

(57) [Claims] 1. An image processing apparatus for converting input image information into image information suitable for a recording apparatus for recording a color image, wherein at least one of an image ratio and an image density ratio of an input image signal is detected. A ratio detection unit, and an image processing unit that performs image processing on the input image signal by a balance image coefficient between color reproducibility and a shot amount in the recording device with respect to a detection ratio of the ratio detection unit. Image processing device. 2. The image processing apparatus according to claim 1, further comprising: a dividing unit that divides the input image information into predetermined regions, wherein each of the divided regions is divided separately by the dividing unit.
An image processing apparatus for performing the processing described in the above. 3. The recording apparatus according to claim 1, wherein the thermal energy causes a state change such as film boiling in the ink to generate bubbles, and the bubbles are used to discharge the ink and discharge the ink from an opening for printing. The image processing apparatus according to claim 1, wherein the image processing is performed. 4. An image processing apparatus for inputting a color image and performing color processing, comprising: storage means for storing a color condition for emphasizing color reproducibility and a color processing condition for emphasizing a shot amount; and inputting the color image. Input means, selecting means for selecting a color processing condition corresponding to the color image from color processing conditions stored in the storage means, and colorizing the color image using the color processing conditions selected by the selecting means. An image processing apparatus comprising: a color processing unit that performs processing.