JPH10105145A - Picture processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely specify environment illuminating light with simple constitution without being affected by a bright line of a light source by providing a light detecting means having sensitivity in a wavelength band which does not coincide with a peak of main luminance of a fluorescent lamp. SOLUTION: An original picture 10 is read, an input picture signal 11 is taken in a color picture processing section 20 in a form of RGB signals, and converted to a chromaticity signal XYZ by an input signal processing section 21. An environment illuminating light measuring means 40 is constituted with a short wavelength light detecting means which has the highest sensitivity in 490nm other than main bright line of a short wavelength in spectroscopic sensitivity characteristics, and a long wavelength light detecting means which has the highest sensitivity in a red color of 690nm. The environment illuminating light measuring means 40 measures environment illuminating light 01 in which main brightness used for observing a printed matter 31 is a fluorescent lamp, and stored the data in a memory 41. A CPU specifies a light source by an environment illuminating light specifying means 42 in accordance with environment illuminating light information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for measuring ambient illumination light and performing color correction.

[0002]

2. Description of the Related Art Manuscript data is loaded into a computer C
It has become common practice in general offices and the like to display on a color display screen such as an RT, make a necessary design or color change, and then output to a printer or the like to obtain a hard copy.

However, the color display (CRT, etc.) is a light source color, whereas the output color from a printer is an object color, and the color reproduction range and the coloring mechanism are different due to the difference in the illumination light of the observation environment and the like. . Therefore, a color space that can be represented by CMYK data in the case of a printer is converted into a color space value XYZ or the like defined by the International Commission on Illumination (CIE) based on RGB signals in each device, for example, a CRT. Convert to device color signal and output. However, different devices usually have an error in color reproduction or an inconsistent reproduction range even with the same color space value. For this reason, a conversion table called a profile is used at the time of signal conversion, and color data is subjected to a certain correction and converted to an output signal. This profile can be obtained by giving various color image data to the target device, measuring the color image output, and creating a table corresponding to the image data and the colorimetric values (in the case of a printer). ). However, since the ambient illumination light at the time of creating these profiles is assumed to be the value of the standard illumination light determined by the CIE having the spectral intensity as shown in FIG. 4, when the ambient illumination light changes, the CRT and the printer output are changed. Objects look different colors due to the different rate of color change. Therefore, when strict color matching is performed, standard illumination light at the time of profile creation and environmental illumination light are made substantially the same, and the type of environmental illumination light is measured and a color correction process is further performed.

[0004]

However, it is not easy to make the standard lighting and the environmental lighting at the time of profile creation almost the same in any place, and it is troublesome and expensive, so that it is difficult for general offices. Such is difficult. Further, in the conventional method of measuring the environment illumination light to be observed and performing color correction, FIG.
As shown in FIG. 3, 3 of visible light (wavelength 380 to 780 nm)
Measurement is performed by a photodetector having color and RGB sensitivities, and color temperature and environmental illumination light are determined to perform color correction. However, the conventional method of measuring and correcting the color temperature of three colors has a problem that it cannot be applied to a fluorescent lamp whose color rendering property is deteriorated by the effect of the bright line, or a light source in which the fluorescent lamp is mixed with the other. For example, such illumination light often seen in offices and the like is shown in FIG.
As shown in (1), when measured by a spectroscopic method, the effects of outdoor light and bright lines are clearly apparent, and there was a problem only with the detection of flicker and bright lines of a fluorescent lamp. In addition, since the wavelength output of the bright line is large and the light output of the other wavelengths is relatively small in the measurement of the light detection means of the three colors in which the bright line is mixed, it is necessary to accurately measure the fluctuation of the illumination light in which the external light is mixed. Was difficult. For this reason, it is inevitable to use a spectroscopic measurement method which is time-consuming and costly.

The present invention has been made in view of the above points, and has as its object to provide an environment illumination light that can be accurately specified with a simple configuration without being affected by a bright line of a light source.

[0006]

In order to achieve the above object, an image processing apparatus according to the present invention has the following features.

The first invention of the present application is directed to a short-wavelength light detecting portion having sensitivity in a wavelength band in which a main spectral sensitivity characteristic peak does not coincide with a peak of a main bright line of a fluorescent lamp, and a long-wavelength light detecting portion having spectral sensitivity characteristic in red. An environmental illumination light measuring unit including a wavelength light detecting unit, and an environmental illumination light specifying unit that specifies environmental illumination light using a signal from the environmental illumination light measuring unit.

The second invention of the present application is directed to a short-wavelength light detecting portion having sensitivity in a wavelength band in which a main spectral sensitivity characteristic peak does not coincide with a peak of a maximum emission line of a light source, and a long-wavelength light detecting portion having spectral sensitivity characteristic in red. An environmental illumination light measuring unit configured by a detection unit, and an environmental illumination light specifying unit that specifies the environmental illumination light based on a signal from the environmental light measuring unit are provided.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of an image input / output block configuration used when a color image processing apparatus inputs image data and outputs it to a printer or monitor according to an embodiment of the present invention. Things.

Reference numeral 01 denotes a fluorescent lamp whose main brightness is ambient light and has a spectral intensity distribution as shown in FIG.
And the print destination 31 and the output monitor 32 are illuminated. Reference numeral 11 denotes an input image signal obtained by standard illumination light and captured, for example, in the form of an NTSC RGB signal. Reference numeral 20 denotes a color image processing unit which performs processing for converting an image signal into a signal suitable for output under fluorescent lamp illumination. The color image processing unit performs density correction and gamma correction on the input signal using correction parameters based on the characteristics of the input image signal, and converts the input signal into a chromaticity signal XYZ. A color correction processing unit 22 that performs optimal correction in consideration of light information and the like; a printer color processing unit 23 that converts the color-corrected signal X'Y'Z 'into signals C, M, Y, and Bk suitable for printer output And a monitor color processing unit 24 for converting the signal X'Y'Z 'into a signal RGB suitable for monitor output. The whole is controlled by a CPU (not shown).
A CMYBk signal 30 obtains a printed matter 31 as an output image by a printer unit (not shown).
The output is displayed on a monitor 32 such as an RT.

The color correction processing section 22 performs correction based on environmental illumination light different from the standard illumination light.
2a, a light source correction table 22b for generating a correction amount signal from the environmental illumination light specifying means 42, scanner illumination information and the like, and a lookup table 22c for performing color correction depending on standard illumination light. Reference numeral 40 denotes an environment illumination light detection unit which detects the environment illumination light 01 for observing the printed matter 31 and the monitor 32, and can store chromaticity value and brightness data in the memory 41.

The environmental illumination light measuring means has a light receiving portion arranged as shown in FIG. 2A and a spectral sensitivity characteristic as shown in FIG. 2B, and receives light selected by a silicon photocell and a filter. It has a spectral sensitivity characteristic of light detecting means having the highest sensitivity at 490 nm other than the main bright line of the fluorescent lamp, and light detecting means having the highest sensitivity of 690 nm in red. By adopting such a configuration, the change of the illumination light excluding the strong influence of the bright line is measured in a state of good SN.

In the method of specifying the illumination light source, the intensity of the red light and the intensity on the short wavelength side included in the illumination vary greatly depending on the illumination light source as shown in FIGS. The ratio is calculated, and the brightness is compared with the light source data stored in advance in consideration of the brightness of the illumination and the like. FIG. 6 is a plot of the output from the ambient illumination light measuring means and the ratio thereof in accordance with the change in the ambient light. The vertical axis represents the total output from the two light detecting means, and the horizontal axis represents the light detection having sensitivity to red. It shows the ratio of the output from the short-wavelength light detecting means to the output from the means, and the plot point A is the value of the reference illumination light in a white fluorescent lamp.

Based on such values, the environmental illumination light identifying means 42 determines that the output of the short wavelength is small if the measurement result at the point B is small, so that the point F is a red output at the point F. Judging by the small size and the brightness, it is judged as a fluorescent light. Similarly, at point D, the output is large and bright, so daylight, and at C, G, H, the brightness is slightly bright, so it is judged that outdoor light has entered the fluorescent lighting, and the afternoon (point G) and blue sky (Point C). Point E is dark and has a lot of redness, so it is assumed to be an old fluorescent lamp.

Next, the operation will be described with reference to FIG. The original image 10 is read by a scanner (not shown), is captured in the form of an RGB signal as an input image signal 11 obtained by standard illumination, and is subjected to density correction and γ correction by a known method in an input signal processing unit 21. It is converted into a chromaticity signal XYZ.

Further, a look-up table 22 based on a matrix corresponding to the standard illumination light in the color correction processing section 20
A color matching process for converting into chromaticity signals XF, YF, ZF using c is performed. This color matching process is performed by selecting a profile corresponding to the output device from a plurality of profiles stored in advance and using a look-up table in the profile. The profile is stored in a RAM (not shown), and selection of the profile and setting of the lookup table in the lookup table 22c are performed by a CPU (not shown).

According to this color matching process, color correction can be performed in consideration of the difference in the color reproduction range between the input device and the output device.

On the other hand, the ambient light measuring means 40
Since the environmental illumination light 01 for observing 1 is measured and its data is stored in the memory 41, the CPU (not shown) specifies the light source by the environmental illumination light specifying means 42 according to the measured environmental illumination light information. Then, the three primary color RWGWBW signals of the white data to be corrected corresponding to the specified light source are sent to the ambient illumination light correction processing 22a from the external light correction table unit 22b obtained in advance by experiments, so that the signals are used for correction. Control.

The ambient light illumination correction process considers that the reference white point changes with the illumination light, and for example,
This is performed by using the color adaptation prediction formula of Von Kries.

[0020]

[Outside 1]

Here, (M) is a constant that can be represented by a 3 × 3 matrix defined from the basic primary colors, and is created based on standard illumination light. (D) is the shift amount of the white spot color and can be expressed as follows.

[0022]

[Outside 2] Here, Rk = RW / FR Gk = GW / FG Bk = BW / FB, and the three primary colors FR, FG, and FB relating to the standard illumination light are tristimulus values FX and FY that indicate a printing paper or a monitor white point under the standard illumination light. , FZ.

According to the environmental illumination light correction processing, XF, YF and ZF depending on the standard light source can be corrected to X ', Y' and Z 'which are color-adapted to environmental light different from the standard.

The environment illumination light correction process reproduces a color different from that of the standard illumination light and corrects the color to match the fluctuated environment illumination light.

Naturally, for a substance whose density (brightness) exceeds the output range, further correction can be made by a known method.

When the measured ambient light is the same as the standard illumination light, the tristimulus value signals X ', Y', Z 'whose outputs of the look-up table 22c have been corrected under the control of a CPU (not shown). To the printer color processing unit 23.

The tristimulus value signals X 'corrected by the color correction unit,
The Y 'and Z' are converted into C, M, Y, and Bk signals 30 suitable for printer output by the printer color processing unit 23, and the R ', G', B 'optimum for monitor display are displayed by the monitor color processing unit 22c. Is converted to These conversions are performed using known methods,
A printed matter 31 as an output image and a monitor image are obtained.

In the color image processing apparatus incorporating the above configuration, the intensity of the illumination light excluding the bright line is measured by the environmental illumination light measuring means having sensitivity other than the main bright line of the fluorescent lamp. Environment illumination light output can be obtained accurately even when the illumination light changes. Further, the environmental illumination light specifying means can grasp the change of the reference environmental illumination light from the ratio and output of the long wavelength light output of the environmental illumination light and the short wavelength light output excluding the fluorescent light emission line, and can specify the type of the illumination light.

Even if the standard illumination light for which the profile data is created is different from the environment illumination light to be observed, the environment illumination light measuring means measures the environment illumination light in accordance with the change in the illumination light, and the color correction means measures the environment illumination light. Since color correction is performed according to the illumination light, reproduction color creation can be accurately realized even with a printed matter, a previewer using a CRT, or the like. Furthermore, only two colors may be measured for measuring the environment illumination light, which has a simple structure and is advantageous in cost.

(Modification) In the above embodiment, the spectral sensitivity characteristic of the ambient light measuring means is 490n other than the main bright line of the fluorescent lamp.
m with the highest sensitivity and a maximum sensitivity of 690n
Although two light detection units having sensitivity to red of m are configured, the wavelength of the highest sensitivity is not limited to the above-described wavelength. Further, a configuration may be employed in which a photodetector having the highest sensitivity at 570 nm or 390 nm is used in combination.

The present invention relates to a plurality of devices (for example, host computer, interface device, reader, printer, etc.)
Or a device composed of one device (for example, a copying machine or a facsimile machine).

In order to operate various devices to realize the functions of the above-described embodiment, a device connected to the various devices or a computer in a system is provided with software for realizing the functions of the above-described embodiments. The present invention also includes a program code supplied and executed by operating the various devices according to a stored program in a computer (CPU or MPU) of the system or apparatus.

In this case, the software program code itself implements the functions of the above-described embodiment, and the program code itself and means for supplying the program code to a computer, such as the program code The storage medium storing the information constitutes the present invention.

As a storage medium for storing such a program code, for example, a floppy disk, hard disk, optical disk, magneto-optical disk, CD-ROM, magnetic tape, nonvolatile memory card, ROM or the like can be used.

When the computer executes the supplied program code, not only the functions of the above-described embodiment are realized, but also the OS (Operating System) running on the computer, or another program. Needless to say, the program code is included in the embodiment of the present invention even when the functions of the above-described embodiment are realized in cooperation with application software or the like.

Further, the supplied program code is stored in a memory provided on a function expansion board of a computer or a function expansion unit connected to the computer, and then provided on the function expansion board or the function storage unit based on the instruction of the program code. It is needless to say that the present invention includes a case where the CPU or the like performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0037]

As described above, the environment illumination light can be accurately specified with a simple configuration without being affected by the bright line of the light source.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment.

FIG. 2 is a diagram illustrating a sensor unit and relative spectral sensitivity of an ambient light measuring unit in the embodiment.

FIG. 3 is a diagram illustrating a relative spectral intensity of a fluorescent lamp and a spectral sensitivity of an ambient light measuring unit in the embodiment.

FIG. 4 is a diagram showing standard illumination light.

FIG. 5 is a diagram showing an example of relative spectral intensity when external light is mixed in a fluorescent lamp.

FIG. 6 is a diagram in which outputs from environmental illumination light measuring means and a ratio thereof are plotted for various types of illumination in the embodiment.

FIG. 7 is a diagram showing an example of the relative spectral intensity of a fluorescent lamp and the spectral sensitivity of a conventional ambient light measuring means.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 1/48 H04N 1/40 D 9/64 1/46 A

Claims (6)

[Claims] 1. A short-wavelength light detection section having sensitivity in a wavelength band in which a main spectral sensitivity characteristic peak does not coincide with a peak of a main emission line of a fluorescent lamp, and a long-wavelength light detection section having spectral sensitivity characteristic in red. An image processing apparatus comprising: an environment illumination light measurement unit configured; and an environment illumination light identification unit that identifies environment illumination light using a signal from the environment illumination light measurement unit. 2. The environment illumination light specifying means specifies the environment illumination light from a relationship between an output ratio between the long wavelength light detection unit and the short wavelength detection unit and an output magnitude of the long wavelength light detection unit. The image processing apparatus according to claim 1, wherein: 3. The image processing apparatus according to claim 1, further comprising performing color correction based on the specified environmental illumination light. 4. The image processing apparatus according to claim 3, wherein the color correction unit performs an environment illumination light correction process and a color matching process according to an output device. 5. A short-wavelength light detecting section having a sensitivity in a wavelength band in which a main spectral sensitivity characteristic does not coincide with a peak of a maximum emission line of a light source, and a long-wavelength detecting section having a spectral sensitivity characteristic in red. An image processing apparatus comprising: an environmental illumination light measuring unit; and an environmental illumination light identifying unit that identifies environmental illumination light based on a signal from the environmental light measuring unit. 6. The environment light specifying unit specifies the environment illumination light based on an output ratio and an output magnitude of the short wavelength detection unit and the long wavelength detection unit.
The image processing apparatus according to any one of the preceding claims.