JPH1198371A - Environmental light measuring instrument, device and method for processing image and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and highly accurately find the color rendering property of environmental light to affect color reproduction by providing a 1st sensor, of which the main beam split sensitivity characteristics have sensitivity near the main bright line of a fluorescent lamp, and a 2nd sensor, of which the main beam split sensitivity characteristics do not contain the main bright line, and finding the color rendering property of environmental light based on the outputs of the 1st and 2nd sensors. SOLUTION: An environmental illumination light measuring means 40 is arranged with the sensors having the following beam split sensitivity characteristics. Concerning a photodetecting means G sensor, the beam split sensitivity characteristics have the peak sensitivity at 546 nm in the main bright line of the fluorescent lamp, a photodetecting means B sensor has the peak sensitivity at 485 nm containing no bright line, and a photodetecting means R sensor has the peak sensitivity at 680 nm not containing the other main bright line. Thus, light intensity in the bright line wavelength part of environmental illumination light and light intensity in a wavelength part except for the bright line can be measured. An environmental light specifying means 41 specifies lightness, color temperature and color rendering property and sends them to a color image processing means 20 as signals.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ambient light measuring device for measuring ambient light, and an image processing device, method and recording medium for obtaining color rendering in accordance with the result of ambient light measurement.

[0002]

2. Description of the Related Art It is common practice to take image data and document data into a computer, display them on a color display screen such as a CRT, make necessary changes in the design and color, and then output them to a printer to obtain a hard copy. It has come to be.

[0003] A color matching process is performed to match the colors of the display image and the hard copy. In the color matching process, conversion between color signals according to a device, for example, conversion from RGB signals according to a CRT to CMYBk signals according to a printer depends on a device defined by the International Standards Committee (CIE). This is performed via a color space (for example, XYZ, etc.) that does not. The correspondence between the signal corresponding to each device and the color space independent of the device is stored in the profile as a conversion table.

[0004] For example, a profile of a printer is created by measuring the color image output from a target device given various color image data and creating a table in which the image data and the colorimetric values correspond to each other. You.

The environment illumination light at the time of creating these profiles has a CIE having a spectral distribution as shown by the curves a and b in FIG.
Since it is assumed that the value is based on the standard illumination light determined in the above, it is possible to correct more accurately by the profile under these illuminations. However, accurate correction cannot be performed when the environment illumination light being observed has illumination having a spectral distribution as shown by the curves c and d in FIG.

[0006] This is because the color rendering property is poor due to the light of the bright line near the wavelength of 550 nm. Under such environmental lighting with poor color rendering properties, even the same printer output product looks different because the color change rate is different. Therefore, conventionally, when performing strict color matching, standard illumination light at the time of profile creation and environmental illumination light are made almost the same, and the type of environmental illumination light is measured and a color correction process is further added. ing.

[0007]

However, it is difficult for a general office to make the standard illumination and the environmental illumination light the same when creating a profile, because it is necessary to perform complicated work using expensive equipment. It is. Further, in the conventional method of measuring the environment illumination light to be observed and performing color correction, as shown in FIG. 7, three colors of visible light (for example, wavelength 380 to 780 nm), RG
The measurement is performed using a photodetector having B color sensitivity, and the color temperature and the ambient illumination light are determined and corrected. However, the conventional method of measuring and correcting color temperatures of three colors has a problem in that a fluorescent light source having a bright line cannot be identified because the wavelength range to be detected is wide.

For this reason, in the improved conventional method, bright lines and flicker are detected to determine whether or not the illumination is fluorescent light. However, the lighting often found in offices and the like is a mixture of fluorescent lamps and other types, and for example, as shown in FIG. 5, when measured by a spectroscopic method, the effect of the bright line is clearly visible in the outdoor light. Because it appears, it is determined to be fluorescent lamp illumination.

However, even if color image processing is performed as fluorescent lamp illumination, the reproduced color becomes inaccurate. In addition, the color rendering properties are different depending on the type of the fluorescent lamp and the elapsed time of use, and similarly, the reproduced color becomes inaccurate. For this reason, in order to perform accurate color reproduction, a spectral measurement method that is time-consuming and costly must be used.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and the first invention of the present application is to enable easy and highly accurate determination of the color rendering of ambient light which affects color reproduction. Aim.

Another object of the present invention is to provide an ambient light measuring device capable of measuring ambient light with a simple configuration.

[0012]

Means for Solving the Problems In order to achieve the above object, the present invention is characterized by having the following configuration.

According to the first aspect of the present invention, there is provided a first sensor having a main spectral sensitivity characteristic near a main bright line of a fluorescent lamp, and a first sensor having a main spectral sensitivity characteristic not including the main bright line of the fluorescent lamp. And a means for obtaining color rendering of ambient light based on outputs of the first sensor and the second sensor.

The invention described in claim 6 of the present application is the first light detecting means whose main spectral sensitivity characteristic has a sensitivity near the wavelength of 546 nm, which is the main emission line of a fluorescent lamp, and the main spectral sensitivity characteristic includes the main emission line. And a second photodetector having sensitivity in a wavelength band longer than 650 nm and near 480 nm.

[0015] The invention described in claim 7 of the present application is the first light detecting means whose main spectral sensitivity characteristic has a sensitivity near the wavelength of 546 nm, which is the main emission line of a fluorescent lamp, and the main spectral sensitivity characteristic includes the main emission line. A second light detecting unit having sensitivity in a wavelength band longer than 650 nm, and a color temperature measuring unit for measuring a color temperature of ambient light.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. 1 shows an example of a color image processing unit according to Embodiment 1. In FIG. 1, the color image processing unit is applied to a system for outputting to a printer or monitor.

FIG. 1 shows an example of a block configuration of an image input / output device used for inputting image data and outputting it to a printer or monitor in a color image processing device according to an embodiment of the present invention. .

Reference numeral 01 denotes environmental illumination light that illuminates the original image 10, the print destination 31 and the output monitor 32. Reference numeral 11 denotes an input image signal obtained by standard illumination light, for example, NTS.
This is an image signal captured in the form of a C RGB signal. 2
Reference numeral 0 denotes a color image processing unit which performs processing for converting an image signal into a signal suitable for output under illumination of an observation environment. The color image processing unit 21 performs density correction and gamma correction using a correction parameter as an input signal and converts the input signal into a chromaticity signal XYZ. The input signal processing unit 21 performs optimal correction by adding environmental illumination light information to the chromaticity signal. Color correction processing unit 22 to be added, color-corrected signals X ', Y', Z '
Printer color processing unit 23 which converts the signals into signals C, M, Y, and Bk suitable for printer output, as well as signals X ', Y', Z '
Is converted to signals R, G, and B suitable for monitor output.
U controlled.

A printed matter 31 is formed by a printer unit (not shown) based on the C, M, Y, and Bk signals 30.
The displayed image is displayed on a monitor 3 such as a CRT based on the R, G, and B signals.
2 is displayed.

The color correction processing section 22 includes an environment illumination light correction processing section 22a, a light source correction table 22b for generating a correction amount signal from scanner illumination information and the like, and a lookup table 2
2c, etc. Reference numeral 40 denotes an environment illumination light measuring unit which measures the environment illumination light 01 illuminating the printed matter 31 and the monitor 32 and can store data corresponding to the illumination light in the memory 41.

In the environment illumination light measuring means, a sensor having a spectral sensitivity characteristic as shown in FIG. 3 is arranged as shown in FIG. Each sensor is configured to receive light selected by a combination of a silicon photocell and an interference filter. The light detection means G sensor has the highest sensitivity at 546 nm of the main emission line of the fluorescent lamp, the light detection means B sensor has the highest sensitivity at 485 nm not including the main emission line, and the light detection means R sensor has another spectral sensitivity characteristic. It has the highest sensitivity at 680 nm without one main emission line. With this configuration, it is possible to measure the light intensity at the emission line wavelength portion of the environmental illumination light and the light intensity at the wavelength portion excluding the emission line.

Although the wavelength selection filter used in the above-described sensor is a combination of a silicon photocell and an interference filter, it can also be realized by a combination of an interference filter and a color filter or a combination of color filters in terms of cost.

Reference numeral 41 denotes an ambient light specifying means, which includes lightness, color temperature,
The color rendering property is specified and sent to the color image processing unit 20 as a signal.

The method of specifying the illumination light source is such that the brightness of green at the emission line wavelength portion included in the illumination and the brightness of blue light and red light excluding the emission line portion greatly vary depending on the illumination light source as shown in FIGS. After measuring the brightness of the emission line wavelength portion and the outputs of the blue portion and the red portion other than the emission line portion, calculate the ratio of each to the total light amount, and further take into account the brightness of the illumination, etc. Lightness, color temperature, and color rendering are specified by comparing with light source data stored in the memory.

FIG. 6 shows the output ratio of the detecting means B to the total output of the three detectors of the environmental illumination light measuring means (horizontal axis in FIG. 6).
And the difference between the output ratios of the detection means G and the detection means R (vertical axis in the figure) is plotted in accordance with the change in ambient light.

The color rendering is determined by the size of the vertical axis in FIG. 6. For example, if the value is 0.2 or less, it is determined that the color rendering is good.
If the value is 0.45 or more, it is determined that the color rendering properties are poor. If the value is 0.2 to 0.45, the color rendering properties are determined to be intermediate. In the example of FIG. 6, even with the same fluorescent lamp illumination, points F1 and D2,
It is positioned and classified at the point F3 or the like. F1 is a normal fluorescent lamp and has poor color rendering properties, F3 is a high color rendering fluorescent lamp and has good color rendering properties, and D2 is an ordinary fluorescent lamp mixed with daylight outdoor light and judged to have an intermediate color rendering property.

The color temperature is determined by the magnitude of the horizontal axis in FIG. 6. For example, when the value is 0.2 or less, the color temperature is low, and between 0.2 and 0.35, the intermediate color temperature is 0. 35 or more are judged to be high color temperatures and are grouped. In the example of FIG. 6, A1
The point is specified as a low color temperature of the standard light source A, the point F3 is specified as a medium color temperature of the high color rendering fluorescent lamp, and the point D1 is specified as a high color temperature of the standard illumination D65.

The color rendering properties and color temperatures are grouped in this way, and the color rendering property and color temperature attribute signals from the ambient light specifying means are sent to the color correction 22, and the coefficients suitable for each grouping are selected. Is done.

The color temperature may be grouped using a known color thermometer instead of the detection means B. Further, the thresholds for specifying the color rendering property and the color temperature are values set based on the characteristics of each detection unit, and differ depending on the characteristics of each detection unit.

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 known by an input signal processing unit 21 to perform known density correction and γ.
The correction is performed and converted into a chromaticity signal XYZ.

Then, a color space compression process for adjusting the difference in the color reproduction range between the devices is performed using a look-up table, and is converted into chromaticity signals XF, YF, and ZF.

On the other hand, the ambient light measuring means 40 measures the ambient illumination light 01 for observing the original 10 and the printed matter 31 and stores it as environmental illumination light information. The CPU (not shown) controls the brightness 42 and the color temperature 4 according to the measured environmental illumination light information.
3. The color rendering 44 is specified, and the three primary color RWGWBW signals of the white data to be corrected are sent to the environment illumination light correction processing unit from the external light correction table unit 22b which is obtained in advance by an experiment so that the signals are used for correction. Control.

The correction of the illumination light color temperature and the brightness is determined by using, for example, a (VonKries) color adaptation prediction formula, assuming that the reference white point changes.

In the method of von Cries, the standard illuminating light in which a matrix has been created is created by, for example, the above-described fluorescent lighting, and the tristimulus values FX and FY of the white point of the monitor or the monitor paper when the observed environmental illuminating light is the same. , FZ, the three primary colors FRFGFB determined by a known conversion method, and the corrected value of a print or the like illuminated with ambient light different from the standard is a tristimulus value X'Y'Z '. It can be expressed as follows.

[0035]

[Outside 1]

Here, (M) is 3 defined from the basic primary colors.
(D) is a constant that can be represented by a matrix of 3 and is a shift amount of the white point, and can be represented as follows.

[0037]

[Outside 2] Here, Rk = RW / FR Gk = GW / FG Bk = BW / FB.

Further, the color rendering property is corrected by using a color rendering property conversion matrix corresponding to the color rendering property. This is because the correction coefficient is, for example, a standard illumination D65 having a good color rendering property,
To determine X1, Y1, Z1 of each color chart, and then measure the same color chart with a light source representative of the color rendering group, obtain chromaticity values X2, Y2, Z2 of each color chart, and It can be obtained by obtaining a coefficient optimal for conversion from the chromaticity value by a least square method in the form of a 3 × 3 matrix. In the memory, conversion coefficients corresponding to each color rendering property created in this way are stored.

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

The tristimulus value signals X ', Y', and Z 'corrected by the color correction section by applying such correction are output to the printer color processing section 23.
The C / M / Y / Bk signals 30 suitable for printer output are converted to R ', G', and B 'which are optimal for monitor display by the monitor color processing unit 22c. These conversions are performed using a known method, and the printed matter 31 as an output image is printed.
Or, a monitor image is obtained.

By performing such processing, a different color is reproduced as compared with the standard illumination light, and the color is corrected so as to match the fluctuating environmental illumination light.

In this embodiment, the ambient light measuring means has a spectral sensitivity characteristic having the highest sensitivity at 546 nm of the main emission line of the fluorescent lamp, and the light detecting means R having a maximum sensitivity of 680 nm in red. Although the maximum sensitivity is constituted by the photodetector B having a sensitivity of 485 nm to red, the wavelength of the maximum sensitivity is not strictly limited to the above-mentioned wavelength. Further, a color temperature specifying unit may be provided separately, or a color temperature specifying unit may be provided instead of the light detection unit R having a maximum sensitivity of 490 nm and having sensitivity to blue. The color image correction process in this case is almost the same as in the above embodiment.

It is also possible to provide a color temperature specifying means in place of the light detecting means B having a maximum sensitivity of 490 nm and having a sensitivity to blue light. In this case, the color temperature is corrected without being grouped, and the color rendering property is improved. The light detection means G and the light detection means R
Is performed at the output ratio. The process and result of the processing are almost the same as in the above embodiment.

According to the present embodiment described above, the brightness, color temperature,
Color rendering can be accurately specified, and color correction can be performed in accordance with ambient illumination light.

Therefore, even if the standard illumination light for which the profile data is created and the environmental illumination light to be observed are different, it is possible to obtain an output image whose color matches the input image.

<Other Embodiments> Even if the present invention is applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, a printer, etc.), a single device (for example, a copying machine or a facsimile machine) can be used. May be applied to such a device.

Further, software for realizing the functions of the above-described embodiment is installed in an apparatus or a computer in the system connected to the various devices so as to operate the various devices so as to realize the functions of the above-described embodiment. 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 realizes 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 in a function expansion board of a computer or a function expansion unit connected to the computer, and then stored in the function expansion board or the function storage unit based on an instruction of the program code. It is needless to say that the present invention includes a case where a provided CPU or the like performs part or all of the actual processing, and the processing realizes the functions of the above-described embodiments.

[0052]

According to the first aspect of the present invention, it is possible to easily and accurately determine the color rendering of environmental light which affects color reproduction.

Further, according to the second aspect of the present invention, it is possible to provide an ambient light measuring device capable of measuring ambient light with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of an image processing apparatus.

FIG. 2 is a diagram showing a configuration of an ambient light measuring unit.

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

FIG. 4 is a diagram showing the relative spectral intensity of standard illumination light.

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

FIG. 6 is a view for explaining the specification of the color temperature and the color rendering by the ambient light specifying unit.

FIG. 7 is a diagram showing the relative spectral intensity of a fluorescent lamp and the spectral sensitivity of a conventional environment measuring means.

Claims (9)

[Claims] A first sensor having a main spectral sensitivity characteristic near a main emission line of the fluorescent lamp; a second sensor having a main spectral sensitivity characteristic not including the main emission line of the fluorescent lamp; An image processing apparatus comprising: means for obtaining color rendering properties of ambient light based on outputs from a sensor and the second sensor. 2. The image processing apparatus according to claim 1, wherein the second sensor has a blue sensor that detects a blue component and a red sensor that detects a red component. 3. The image processing apparatus according to claim 1, further comprising performing a color process according to a color rendering property of the ambient light. 4. The image processing apparatus according to claim 3, wherein the color processing performs a color adaptation conversion process. 5. The image processing apparatus according to claim 1, wherein said means for calculating the color rendering property of the environment light calculates brightness and color temperature of the environment light. 6. A first light detecting means having a sensitivity near a wavelength of 546 nm whose main spectral sensitivity characteristic is a main emission line of a fluorescent lamp, and 650n whose main spectral sensitivity characteristic does not include said main emission line.
an ambient light measuring device, comprising: a second light detecting means having a wavelength band longer than m and having a sensitivity near 480 nm. 7. A first light detecting means having a sensitivity near a wavelength of 546 nm whose main spectral sensitivity characteristic is a main emission line of a fluorescent lamp, and 650n whose main spectral sensitivity characteristic does not include said main emission line.
An ambient light measuring device comprising: a second light detecting unit having sensitivity in a wavelength band longer than m; and a color temperature measuring unit for measuring a color temperature of ambient light. 8. An output from a first sensor whose main spectral sensitivity characteristic has sensitivity near a main emission line of a fluorescent lamp and a second output whose main spectral sensitivity characteristic does not include the main emission line of the fluorescent lamp.
An image processing method comprising: inputting an output from a sensor of (1) to obtain color rendering of ambient light. 9. A recording medium storing a program in a computer-readable state, wherein a main spectral sensitivity characteristic is an output from a first sensor having a sensitivity near a main bright line of a fluorescent lamp and a main spectral sensitivity characteristic. A recording medium which receives an output from a second sensor that does not include a main emission line of the fluorescent lamp and records a program for obtaining color rendering of ambient light.