JP2003149050A - Colorimetric apparatus, colorimetric method, colorimetry control program, and recording medium in which colorimetry control program has been stored and can be read by computer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and precisely measure general substance colors using a general color imaging means. SOLUTION: This is a digital still camera provided with a CCD 16 which receives an optical image of an object of measurement via a photographing optical system, and outputs a specified three-primary-color image signal according to its light intensity, an EEPROM 86 which stores a plurality of sets of conversion coefficient groups for converting the three-primary-color image signal into colorimetric values based on a specified standard trichromatic system, a selection portion 95 for selecting a set of conversion coefficient groups out of the plurality of sets of conversion coefficient groups, according to a three- primary-color image signal outputted from the CCD 16 when an image of the object of measurement is taken, and a colorimetry computing portion 96 for computing colorimetric values based on the standard trichromatic system from the three-primary-color image signal obtained by the CCD 16 using the conversion coefficient groups selected by this selection portion 95.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a colorimetry technique for performing accurate colorimetry using a relatively simple color image pickup means.

[0002]

2. Description of the Related Art Conventionally, in a tristimulus value direct reading colorimeter, a CI
Color matching functions x (λ), y (λ), z of tristimulus values X, Y, Z of E
Light from a measurement target is received through a filter having a spectral transmission characteristic that matches (λ) with high accuracy, and a colorimetric value is obtained based on the received light intensity.

[0003]

However, a filter that matches the color matching function is expensive and is not suitable for general users to easily perform color measurement. There has been a demand for simple and accurate color measurement using a CCD.

Therefore, conventionally used color CC
There has been proposed a colorimetric device that quantitatively and accurately measures the attribute of a color to be measured using a D camera (Japanese Patent Laid-Open No. 200-200200).
0-9535). In this apparatus, the emission spectral characteristic of a measurement target such as a cathode ray tube or a liquid crystal display is estimated using the measurement data and the storage data, and the chromaticity coordinate value is calculated using the estimation result.

However, this colorimetric device is limited to measuring light-emitting bodies such as cathode ray tubes and liquid crystal displays, and does not disclose accurate measurement of general object colors.

The present invention has been made in view of the above,
A color measuring device, a color measuring method, a color measuring control program, and a computer readable program storing a color measuring control program capable of easily and accurately measuring a general object color by using a general color image pickup means. The purpose of the present invention is to provide a stable recording medium.

[0007]

The invention according to claim 1 is
A color image pickup means for receiving an optical image of an object to be measured through a photographing optical system and outputting a predetermined three-primary-color image signal corresponding to the light intensity; A storage means for storing a plurality of sets of conversion coefficient groups for converting into color values, and one of the plurality of sets of conversion coefficient groups in accordance with the three primary color image signals output from the color imaging means when the measurement target is imaged. Selecting means for selecting a set of conversion coefficient groups, and a colorimetric value based on the standard three-color color system from the three primary color image signals obtained by the color imaging means using the conversion coefficient group selected by the selecting means. It is characterized by including a conversion calculation means for calculating.

According to this structure, when the object to be measured is imaged, the color imager receives the optical image of the object to be measured through the photographing optical system, and outputs the predetermined three primary color image signals corresponding to the light intensity. To be done. For example, when photoelectric conversion elements having R, G, B color filters are two-dimensionally arranged to form a color image pickup means, image signals R, G, B are output as three primary color image signals. It

On the other hand, the storage means stores a plurality of sets of conversion coefficient groups for converting the three primary color image signals into colorimetric values based on a predetermined standard three-color color system. As the predetermined standard three-color color system, for example, the XYZ color system adopted by CIE is used.

Then, one set of conversion coefficient groups is selected from a plurality of sets of conversion coefficient groups in accordance with the three primary color image signals output from the color image pickup means, and the selected conversion coefficient group is used to convert the three primary color image signals. A colorimetric value is calculated based on the standard three-color color system.

As a result, the conversion coefficient group suitable for the image signals of the three primary colors obtained by imaging the object to be measured is selected, so that the colorimetric values based on the standard three-color color system can be accurately obtained.

According to a second aspect of the present invention, there is provided a digital still camera having the color image pickup means, and a personal computer having the storage means, the selection means and the conversion calculation means. A transmitting means for transmitting the three primary color image signals output from the color image capturing means to the personal computer when the image is captured, the personal computer receiving means for receiving the three primary color image signals transmitted from the digital still camera. It is characterized by having.

According to this structure, when the measurement target is imaged, the color imaging means of the digital still camera allows
An optical image of a measurement target is received via a photographing optical system, and predetermined three-primary-color image signals corresponding to the light intensity are output. The three-primary-color image signals are transmitted from a digital still camera to a personal computer, and a personal computer Receives the three primary color image signals.

The personal computer is provided with, for example, a colorimetric control program that causes the personal computer to function as the selecting means and the conversion computing means, so that the personal computer responds to the received three-primary-color image signals.
A set of conversion coefficient groups is selected from a plurality of sets of conversion coefficient groups,
The selected conversion coefficient group is used to calculate the colorimetric value based on the standard three-color color system from the three primary color image signals. Therefore, the calculation load on the digital still camera is reduced.

According to a third aspect of the present invention, the color image pickup means, the selection means, and the conversion calculation means are provided in a digital still camera, and the digital still camera sets a color measurement mode as an operation mode. It is characterized in that it is provided with an operating means that can be operated from the outside, and that the selecting means and the conversion calculating means operate when the color measurement mode is set.

According to this structure, when the operation means is operated and the colorimetric mode is set as the operation mode, the selection means and the conversion operation means operate. Therefore, by using the digital still camera, an object to be measured can be measured. Colorimetric values based on the standard three-color color system can be calculated easily and accurately.

According to a fourth aspect of the present invention, the digital still camera includes display means and display control means for displaying a photographing procedure for color measurement on the display means when the color measurement mode is set. It is characterized by being

According to this structure, when the color measurement mode is set, the photographing procedure for color measurement is displayed on the display means.
This will guide the user through the color measurement procedure,
Even a user who is unfamiliar with the color measurement operation, which is different from the procedure of normal photographing, can surely be made to perform the color measurement.

According to a fifth aspect of the present invention, the plurality of sets of conversion coefficient groups stored in the storage means include a plurality of correction subjects whose colorimetric values based on the standard three-color color system are known. It is characterized in that it is obtained based on the relationship between the plurality of the three primary color image signals obtained by imaging by the imaging means and the known colorimetric values.

According to this structure, the plurality of sets of conversion coefficient groups stored in the storage means pick up a plurality of correction subjects whose colorimetric values based on the standard three-color color system are known by the color image pickup means. Since it was obtained based on the relationship between a plurality of three primary color image signals obtained and the known colorimetric values, by using these conversion coefficient groups, the three primary color image signals when the measurement target was imaged Colorimetric values based on the standard three-color color system can be accurately obtained.

According to a sixth aspect of the present invention, the plurality of sets of conversion coefficient groups stored in the storage means are a set of first conversion coefficient groups obtained by using all of the plurality of correction subjects. The hue value is composed of a plurality of sets of second conversion coefficient groups respectively obtained by using a predetermined number of correction subjects belonging to a predetermined range, and the selection means captures an image of the measurement target by the color imaging means. The colorimetric value based on the standard three-color color system is provisionally calculated from the three primary color image signals obtained by using the first conversion coefficient group, and the hue value is calculated using the result, and the plurality of sets of the second color group are calculated. It is characterized in that a set of second conversion coefficient groups corresponding to the hue value is selected from the conversion coefficient group.

According to this structure, the colorimetric values based on the standard three-color color system are provisionally calculated from the three primary color image signals obtained by imaging the object to be measured by the color imaging means using the first conversion coefficient group. The hue value is calculated using the result, and one set of second conversion coefficient groups corresponding to the hue value is selected from the plurality of sets of second conversion coefficient groups.

Since the colorimetric value based on the standard three-color color system is calculated by using the selected second conversion coefficient group, the colorimetric value can be calculated with higher accuracy.

According to a seventh aspect of the present invention, a plurality of the three primary color image signals obtained by picking up a plurality of correction subjects whose colorimetric values based on the standard three-color color system are known by the color image pickup means, The present invention is characterized in that a coefficient calculation means for calculating a plurality of sets of the conversion coefficient groups based on the relationship with a known colorimetric value and storing the calculation results in the storage means is provided.

According to this configuration, a plurality of three-primary-color image signals obtained by picking up a plurality of correction subjects whose colorimetric values based on the standard three-color color system are known by the color imaging means, and the known colorimetric measurements. Since a plurality of sets of conversion coefficient groups are calculated based on the relationship with the values and the calculation results are stored in the storage means, even if the spectral characteristics of the color image pickup means change due to deterioration over time, a plurality of sets of conversion coefficients are obtained. By calculating the group again and storing it in the storage means, the highly accurate colorimetric value calculating function can be maintained for a long period of time.

According to an eighth aspect of the present invention, a plurality of sets of conversion coefficient groups for converting the three primary color image signals into colorimetric values based on a predetermined standard three-color color system are stored in advance, and the conversion coefficient group is stored through the photographing optical system. A light image of a measurement target is received by a color image pickup means that outputs predetermined three primary color image signals corresponding to the light intensity, and the plurality of sets of the plurality of sets are set in accordance with the three primary color image signals output when the measurement target is imaged. A set of conversion coefficient groups is selected from the conversion coefficient group, and a colorimetric value based on the standard three-color color coordinate system is calculated from the three primary color image signals obtained by the color image pickup means using the selected conversion coefficient group. It is characterized by doing.

According to this structure, when the measurement target is imaged, the predetermined three primary color image signals corresponding to the light intensities when the optical image of the measurement target is received from the color imaging means are output from the color imaging means. To be done. For example, when photoelectric conversion elements having R, G, B color filters are two-dimensionally arranged to form a color image pickup means, image signals R, G, B are output as three primary color image signals. It

On the other hand, a plurality of sets of conversion coefficient groups for converting the three primary color image signals into colorimetric values based on a predetermined standard three-color color system are stored. As the predetermined standard three-color color system, for example, the XYZ color system adopted by CIE is used.

Then, one set of conversion coefficient groups is selected from a plurality of sets of conversion coefficient groups in accordance with the three primary color image signals output from the color image pickup means, and the selected conversion coefficient group is used to convert the three primary color image signals. A colorimetric value is calculated based on the standard three-color color system.

As a result, the conversion coefficient group suitable for the three primary color image signals obtained by imaging the measurement object is selected, so that the colorimetric value based on the standard three-color color system can be accurately obtained.

According to a ninth aspect of the present invention, there is provided a colorimetric control program for measuring a color of an object to be measured, which receives an optical image of the object to be measured through a photographing optical system, and a predetermined value corresponding to the light intensity. Color image pickup means for outputting the three primary color image signals, and storage means for storing a plurality of sets of conversion coefficient groups for converting the three primary color image signals into colorimetric values based on a predetermined standard three color color system. Selecting means for selecting one set of conversion coefficient groups from the plurality of sets of conversion coefficient groups in accordance with the three primary color image signals output from the color image pickup means when the color device picks up an image of a measurement object; A colorimetric measurement functioning as a conversion calculation means for calculating a colorimetric value based on the standard three-color color system from the three primary color image signals obtained by the color image pickup means using the conversion coefficient group selected by Control program It is a non.

According to this structure, when the measurement target is imaged, the predetermined three primary color image signals corresponding to the light intensities when the optical image of the measurement target is received from the color imaging means are output from the color imaging means. To be done. On the other hand, a plurality of sets of conversion coefficient groups for converting the three primary color image signals into colorimetric values based on a predetermined standard three color system are stored.

When this color measurement control program is read and executed by a computer, one set of conversion coefficient groups is selected from a plurality of sets of conversion coefficient groups in accordance with the three primary color image signals output from the color image pickup means. A colorimetric value based on the standard three-color color system is calculated from the three primary color image signals using the selected conversion coefficient group.

As a result, the conversion coefficient group suitable for the image signals of the three primary colors obtained by picking up the image of the object to be measured is selected, so that the colorimetric values based on the standard three-color color system can be accurately obtained.

A tenth aspect of the present invention is a computer-readable recording medium in which the colorimetric control program according to the ninth aspect is stored.

According to this structure, when the measurement target is imaged, the predetermined three primary color image signals corresponding to the light intensities when the optical image of the measurement target is received from the color imaging means are output from the color imaging means. To be done. On the other hand, a plurality of sets of conversion coefficient groups for converting the three primary color image signals into colorimetric values based on a predetermined standard three color system are stored.

When the computer executes the colorimetric control program stored in this recording medium, the colorimetric control program is read and executed. In accordance with the three primary color image signals output from the color image pickup means, one set of conversion coefficient groups is converted. A coefficient group is selected, and a colorimetric value based on the standard three-color color system is calculated from the three primary color image signals using the selected conversion coefficient group.

As a result, the conversion coefficient group suitable for the three primary color image signals obtained by imaging the measurement object is selected, so that the colorimetric value based on the standard three-color colorimetric system can be accurately obtained.

Incidentally, in the color measuring device according to claim 7,
The coefficient calculation means calculates a set of first conversion coefficient groups using all of the plurality of correction subjects, and uses a plurality of correction subjects of a predetermined number whose hue value is within a predetermined range. Each of the two conversion coefficient groups is calculated, and the selecting means uses the first conversion coefficient group to obtain a colorimetric value based on the standard three-color color system from the three primary color image signals obtained by the color imaging means. It is also possible to tentatively calculate, calculate a hue value based on the result, and select a set of second conversion coefficient groups corresponding to the hue value from the plurality of sets of second conversion coefficient groups.

According to this structure, the colorimetric values based on the standard three-color color system are provisionally calculated from the three primary color image signals obtained by imaging the object to be measured by the color imaging means using the first conversion coefficient group, and The hue value is calculated using the result, and one set of second conversion coefficient groups corresponding to the hue value is selected from the plurality of sets of second conversion coefficient groups.

Since the colorimetric value based on the standard three-color color system is calculated using the selected second conversion coefficient group, the colorimetric value can be calculated with higher accuracy.

A color measuring device having the above structure or claim 6
In the color measurement device described above, the predetermined range to which the hue values of the predetermined number of correction subjects used to calculate the plurality of sets of second conversion coefficient groups belong to each other, and the hue ranges are adjacent to each other. It may be set to do.

According to this structure, a colorimetric value based on the standard three-color color system is provisionally calculated from the three primary color image signals obtained by the color image pickup means using the first conversion coefficient group, and the hue value is based on the result. Is calculated, and one set of second conversion coefficient groups corresponding to the hue value is selected from the plurality of sets of second conversion coefficient groups.

At this time, the first hue value calculated based on the colorimetric value tentatively calculated for the first measurement object and the first hue value calculated based on the tentatively calculated colorimetric value for the second measurement object. When the second hue value and the second hue value are located on opposite sides of the predetermined boundary, the difference between the first hue value and the second hue value is small, that is, the first measurement target and the second measurement value. Even when the target color difference is small, the selected second conversion coefficient group is different.

However, since the different second conversion coefficient groups are calculated by using the correction subject whose part is common to each other, the calorimetric values of the first measurement object and the second measurement object are calculated. In this case, it is possible to prevent a step from occurring and the calculated colorimetric values are greatly different from each other, and the colorimetric values based on the standard three-color color system can be accurately obtained.

[0046]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the configuration of a digital still camera, which is an embodiment of a color measuring device according to the present invention, will be described with reference to FIGS.

As shown in FIG. 1, the present digital still camera 1 is composed of a single-lens reflex camera having a camera body 2 and an interchangeable lens 3 which is detachably attached to the front center of the camera body 2. As shown in FIG. 2, the electronic viewfinder 4 is provided on the top of the camera body 2.
(EVF: Electronic View Finder) and pop-up type flash 5 (FIG. 4) are provided.

In FIG. 1, a battery storage chamber 12 and a card storage chamber 13 are provided inside the grip portion 11. Four AA batteries are used as the power source for the camera in the battery compartment 12.
A dry battery is stored, and a memory card 14 for recording image data of a captured image is detachably stored in the card storage chamber 13.

Further, a color image pickup device 16 is arranged at an appropriate position within the camera body 2 on the optical axis 15 of the interchangeable lens 3 when the interchangeable lens 3 is mounted on the mount portion.

A color image pickup device (hereinafter referred to as "CCD") 16 has a CCD (Charge Cou) as shown in FIG.
area sensor 1 in which pled devices) are arranged two-dimensionally
R (red), G (green), B (blue) on the surface of each CCD of 7.
Color filter 18 of is attached in a checkered pattern,
It is configured by a so-called Bayer type single plate type color area sensor, and in the present embodiment, for example, 1600.
(X direction) x 1200 (Y direction) = 1.92 million CCDs
(Hereinafter, also referred to as “pixel”).

As shown in FIG. 3, the area sensor 1
If the pixel position of the i-th row and the j-th column of 7 is (i, j), R,
For each of the G and B color filters, R is (2h + 1, 2k +
1) and G are (2h + 2,2k + 1), (2h + 1,2k
+2) and B are arranged at pixel positions of (2h + 2,2k + 2). However, i = 1,2, ..., n, j = 1,2, ..., m, n = 1600, m = 1200, h = 0,1,2, ..., n / 2 (= 800), k = 0, 1, 2, ..., M / 2 (= 600).

In FIG. 2, on the upper surface of the camera body 2,
A shutter button 19 is provided. The shutter button 19 is configured so that it can be operated in a "half-pressed state" in which it is pressed halfway and in an "full-pressed state" in which it is further pressed. When a preparatory operation (a preparatory operation such as setting of an exposure control value and focus adjustment) for photographing a still image is executed and the shutter button 19 is fully pressed, the photographing operation (CCD 1
6 is exposed, and the image signal obtained by the exposure is subjected to predetermined image processing and recorded in the memory card 14).

The electronic viewfinder 4 includes the eyepiece lens 2
0, a finder window 21 is provided, and a finder display section 22 (FIG. 4) is incorporated. Viewfinder display 2
In the present embodiment, reference numeral 2 is a color liquid crystal display device having, for example, 200 (X direction) × 150 (Y direction) = 30000 pixels, and a monitor image of a subject photographed by the CCD 16, that is, the shutter button 19 is operated. The image of the subject captured by the CCD 16 as a moving image is displayed in the non-shooting standby state. Eyepiece 20
For guiding the monitor image displayed on the finder display section 22 to the outside of the finder window 21. With such a configuration, the photographer can visually recognize the subject by looking through the finder window 21 on the monitor image displayed on the finder display unit 22.

The monitor image is displayed on the finder display section 22.
Since it is for displaying on the
The CCD 16 is operated in an operation mode (hereinafter referred to as “draft mode”) different from normal still image shooting to shoot a monitor image of the same size as the display size of the finder display unit 22. That is, in this embodiment,
Since the finder display section 22 is composed of 200 × 150 pixels, the CCD 16
Light is received by all the pixels of, but image data is read by X,
The pixel number is set to 200 in both Y directions by thinning-out with 8 pixel pitch, that is, 1/8.
A × 150 monitor image is obtained at high speed.

An external display section 23 is provided in the rear surface of the camera body 2 substantially in the center thereof. In the present embodiment, the external display unit 23 has, for example, a pixel count of 200 (X direction) × 150 (Y
Direction) = 30000 color liquid crystal display device, and displays a menu screen for setting a mode related to exposure control, a mode related to a shooting scene, shooting conditions, etc. in the recording mode, and a memory card 1 in the playback mode.
The captured image recorded in No. 4 is reproduced and displayed.

On the left side of the external display section 23 is the power switch 3
1 is provided. The power switch 31 also serves as a mode setting switch that switches and sets a recording mode (a mode that performs a function of taking a picture) and a reproduction mode (a mode that reproduces a recorded image on the external display unit 23). That is,
The power switch 31 is a three-point slide switch. When the contact is set to the central "OFF" position, the power is turned off. When the contact is set to the upper "REC" position, the power is turned on and the recording mode is changed. When the contact is set and the contact is set to the lower "PLAY" position, the power is turned on and the reproduction mode is set.

A quad switch 32 is provided on the upper right side of the external display section 23. The quadruple switch 32 has a circular operation button, and pressing operations in four directions of up, down, left, and right on the operation button are detected as operations of the upper switch 32U, the lower switch 32D, the left switch 32L, and the right switch 32R, respectively. It is like this. The quad switch 32 has multiple functions, and for example, the external display unit 23
It functions as an operation switch for changing the item selected on the menu screen for shooting scene setting displayed in, and changes the selected playback target frame on the index screen where multiple thumbnail images are displayed in an array. Functioning as an operating switch for the left switch 32
The L and right switch 32R functions as a zoom switch for changing the focal length of the zoom lens of the interchangeable lens 3.

At the lower right position of the external display unit 23, a cancel switch 33 and a confirm switch 3 are provided as switches for performing operations relating to the display and display contents of the external display unit 23.
4, a menu display switch 35 and a display changeover switch 36 are provided.

The cancel switch 33 is a switch for canceling the contents selected on the menu screen. The confirmation switch 34 is a switch for confirming the content selected on the menu screen. The menu display switch 35 is a switch for displaying a menu screen on the external display unit 23, and for switching the contents of the menu screen (for example, a shooting scene setting screen and a mode setting screen regarding exposure control).
Each time the menu display switch 35 is pressed, the menu screen switches. The display changeover switch 36 is a switch for making a display on the external display section 23 or turning off the display. Every time the display changeover switch 36 is pressed, the external display section 23 is displayed.
Are alternately displayed and hidden. In order to save battery power, the external display unit 23 is not displayed when the camera is activated.

Next, the electrical configuration of the digital still camera 1 will be described with reference to FIGS. Note that, in FIG. 4, the same components as those in FIGS. 1 to 3 are denoted by the same reference numerals, and the interchangeable lens 3 is illustrated in two locations for convenience of description.

The digital still camera 1 includes an interchangeable lens 3, an image pickup section 40, a signal processing section 50, a light emission control section 58, a lens control section 60, a display section 70, an operation section 80, an overall control section 90 and the like.

The interchangeable lens 3 is provided with a focus lens 6, a zoom lens 7 and a diaphragm 8 for adjusting the amount of transmitted light, and stores peculiar information (information such as the open F value and focal length) relating to the lens. Lens ROM2
It is equipped with 4. The lens ROM 24 has an electrical contact 25
It is connected to the overall control unit 90 via.

The image pickup section 40 photoelectrically converts the subject light image incident through the interchangeable lens 3 and outputs it as an image signal, and includes a CCD 16, a timing generator 41, and a timing control circuit 42.

The CCD 16 is the timing generator 4
Based on the drive control signal (accumulation start signal / accumulation end signal) input from 1, the subject light image is received for a predetermined exposure time and converted into an image signal (charge accumulation signal), and the image signal is output from the timing generator 41. The signal is sent to the signal processing unit 50 in accordance with the input read control signal (horizontal synchronizing signal, vertical synchronizing signal, transfer signal, etc.).

At this time, the image signal has the respective color components R, G, B.
And is sent to the signal processing unit 50. That is,
The image signal of the color component R is transmitted by sequentially reading the image signal received by each pixel at the pixel position (2h + 1, 2k + 1), and the pixel position (2h + 2, 2k + 1), (2h +
The image signal of the color component G is transmitted by sequentially reading the image signal received by each pixel of (1, 2k + 2), and the image signal received by each pixel of the pixel position (2h + 2, 2k + 2) is sequentially read to obtain the color. The image signal of the component B is transmitted.

In the following description, for convenience of description, the light-receiving signal of each pixel is distinguished from the image signal forming a photographed image by the set thereof in order to distinguish the light-receiving signal of each pixel from the pixel signal (analog value). ) Or pixel data (digital value).

The timing generator 41 generates a drive control signal based on the control signal input from the timing control circuit 42 and a read control signal based on the reference clock signal, and sends them to the CCD 16.

The timing control circuit 42 controls the photographing operation of the CCD 16 and generates a photographing control signal based on the control signal input from the overall control section 90. This shooting control signal is a control signal for displaying a moving image of a subject (hereinafter referred to as “live view image”) on the finder display unit 22 of the electronic viewfinder 4 while the shooting is in standby in the recording mode. A control signal for operating a still image of a subject (hereinafter referred to as “recorded image”), a reference clock signal, and a timing signal for synchronizing the image signal sent from the CCD 16 with the signal processing unit 50 (synchronization). Clock signal) etc. This timing signal is input to the analog signal processing circuit 51 and the A / D conversion circuit 52 in the signal processing unit 50.

The signal processing section 50 performs predetermined analog signal processing and digital signal processing on the image signal sent from the CCD 16, and the signal processing of the image signal is performed for each pixel signal constituting the image signal. . The signal processing unit 50 includes an analog signal processing circuit 51, an A / D conversion circuit 52, a black level correction circuit 53, a white balance (W
B) The circuit 54, the γ correction circuit 55, and the image memory 56 are provided, and the black level correction circuit 53, the WB circuit 54, and the γ correction circuit 55 constitute a circuit that performs digital signal processing.

The analog signal processing circuit 51 includes the CCD 16
And a CDS (correlated double sampling) circuit for performing a predetermined analog signal processing on an image signal of an analog value output from the CDS (correlated double sampling) circuit,
An AGC (auto gain control) circuit for adjusting the level of the image signal is provided.

The A / D conversion circuit 52 converts the image signal output from the analog signal processing circuit 51 into a digital value image signal (hereinafter referred to as "image data").
A pixel signal obtained by receiving light at each pixel is converted into, for example, 10-bit pixel data. The black level correction circuit 53 is
The black level of each pixel data that has been / D converted is corrected to a reference black level.

The WB circuit 54 adjusts the white balance of the photographed image, and converts the level of the pixel data of each color component R, G, B by using the level conversion table input from the overall control unit 90. Adjust the white balance of the shot image. The conversion coefficient of each color component in the level conversion table is set by the overall control unit 90 for each captured image.

The γ correction circuit 55 performs gradation correction by correcting the γ characteristic of pixel data, and has, for example, five types of γ correction tables having different γ characteristics as a look-up table (LUT) and set. The γ correction of the pixel data is performed by a predetermined γ correction table according to the captured scene. In this γ correction process, 10-bit pixel data is converted into 8-bit (256 gradations) pixel data. The pixel data before the γ correction processing is set to 10-bit data in order to prevent the image quality from being deteriorated when the γ correction is performed with the γ characteristic having strong nonlinearity. Further, the pixel data of each color component R, G, B has undergone a predetermined level conversion in the WB circuit 54, and these pixel data are respectively γ-corrected by the γ-correction table.

The image memory 56 is a memory for temporarily storing the image data for which signal processing has been completed, and has a capacity capable of storing, for example, image data for 8 frames in this embodiment.

The storage capacity for storing one frame of image data is 19 since the number of pixels of the CCD 16 is 1600 × 1200 = 1920,000 in this embodiment.
The capacity is capable of storing 20,000 color pixel data.

The light emission control unit 58 controls the light emission of the flash 5 based on the light emission control signal input from the overall control unit 90. The light emission control signal includes a light emission preparation instruction, a light emission timing, and a light emission amount. Be done.

The light emission control unit 58 charges the main capacitor to make the light emission possible when the light emission preparation instruction signal is sent from the overall control unit 90, and synchronizes with the timing signal when the light emission timing signal is further sent. To discharge the stored charge of the main capacitor, which causes the flash 5
Light up. Then, when the light emission stop signal is sent from the overall control unit 90, the discharge of the main capacitor is stopped,
As a result, the flash 5 emits a required amount of light.

The lens controller 60 includes a focus lens driving motor (FM) 27 and a zoom lens driving motor (ZM) 28, and an aperture control circuit 61, a focus control circuit 62, and a zoom control circuit 63. .

The aperture control circuit 61 controls the aperture value of the aperture 8. The aperture control circuit 61 drives the aperture 8 based on the aperture value input from the overall control unit 90 and sets the aperture amount to the aperture value. . The focus control circuit 62 controls the drive of the FM 27, and the AF input from the overall control unit 90.
F based on a control signal (for example, a control value such as the number of drive pulses)
The focus lens 6 is moved to the focal position by driving M27. The driving force of the FM 27 is transmitted to the focus lens 6 via the coupler 26.

The zoom control circuit 63 controls the drive of the ZM 28 and is based on the zoom control signal (operation information of the quad switch 32) input from the overall control section 90.
28 is driven to move the zoom lens 7. The zoom control circuit 63 receives the operation information of the right switch 32R of the quad switch 32 from the overall control section 90,
The ZM 28 is driven in the positive direction to move the zoom lens 7 to the wide-angle side, and the left switch 3 of the quad switch 32 is selected.
When the 2L operation information is input, the ZM 28 is driven in the reverse direction to move the zoom lens 7 to the telephoto side.
The driving force of the ZM 28 is transmitted to the zoom lens 7 via the coupler 26.

The display section 70 is the finder display section (E
A VF 22 and an external display unit (LCD) 23 are provided, and VRAMs 71 and 72 are provided. VRAM7
Reference numeral 1 denotes a buffer memory for storing a display image on the external display unit 23, which corresponds to 3 pixels corresponding to the number of pixels of the external display unit 23.
It has a memory capacity capable of storing 10,000 color pixel data. The RAM 72 is a buffer memory for storing a display image on the finder display unit 22, and has a memory capacity capable of storing 30,000 color pixel data corresponding to the number of pixels of the finder display unit 22.

The operation section 80 has a lock switch 81 which is turned on when the shutter button 19 (FIG. 2) is half pressed.
And a release switch 82 that is turned on when the shutter button 19 (FIG. 2) is fully pressed.
The switch groups 31 to 36 shown in are included, and these operation information are input to the overall control unit 90.

The EEPROM 86 is a C of the overall control unit 90.
The control program for controlling the operation of the PU is stored, and the color measurement control program is included as a part of the control program. The RAM 87 temporarily stores various data in arithmetic processing and control processing.

The overall control unit 90 is composed of a CPU and the like,
The operation of each part of the digital still camera 1 is controlled according to the control program stored in the EEPROM 86. When the shutter button 19 is half pressed and the ON signal of the lock switch 81 is detected, a still image of the subject is taken. When the shutter button 19 is fully pressed and the ON signal of the release switch 82 is detected, a preparatory operation for setting (exposure control value setting, preparatory operation such as focus adjustment) is performed.
Shooting operation (exposure of the CCD 16 and subjecting the image signal obtained by the exposure to predetermined image processing
4 has a function of executing a series of operations recorded in 4).

The overall control unit 90 uses the card I / F 11
It is configured to be connectable to the memory card 14 via 1. The card I / F 111 is an interface for writing image data to the memory card 14 and reading image data. Further, the overall control unit 90 is configured to be connectable to an external personal computer (PC) 113 via the communication I / F 112. I for communication
The / F 112 is, for example, an interface conforming to the USB standard and is for enabling communication with the PC 113.

The overall control section 90 includes an operation mode control section 91 and a colorimetric control section 92 as functional blocks.

The operation mode control unit 91 controls the setting of the operation mode of the camera, and is set based on the operation on the operation unit 80 performed while the menu screen for mode setting is displayed. The operation mode includes a shooting mode and a colorimetric mode, and the shooting mode includes a shooting scene mode and an exposure control mode.

On the menu screen, for example, a plurality of items are displayed in an array, and the currently selected item is displayed to show the selected state (for example, cursor or reverse display). As the initial screen for selecting the operation mode, the external display unit 23 displays a menu screen as shown in FIG. 5, for example. Note that, in FIG. 5, for the sake of convenience of description, the thick frame display is used to indicate the reverse display.

In the menu screen of FIG. 5, when the upper switch 32U of the quad switch 32 is pressed, the reverse display position cyclically moves upward, and when the lower switch 32D of the quad switch 32 is pressed, the reverse display position is displayed. Moves cyclically downward. Then, when the confirmation switch 34 is pressed, the item (shooting mode in FIG. 5) highlighted at that time is set as the operation mode.

Therefore, the user operates the quadruple switches 32 in the vertical direction on the menu screen for selecting the operation mode to select a desired operation mode, and operates the confirm switch 34 to set the operation mode. be able to.

As the mode relating to the shooting scene, the shooting scene is selected from portrait, landscape, night view, etc., for example.

The mode relating to exposure control is a mode relating to how to determine the exposure control value at the time of photographing (image recording), that is, the aperture value of the diaphragm 8 and the exposure time. In this embodiment, the mode relating to the exposure control includes, for example, a program mode, a shutter priority mode, and an aperture priority mode.
The exposure control value is set by using one of a plurality of preset program charts. In the program mode, the exposure control value is set by using a standard program chart, and the shutter is set. In the priority mode, the exposure control value is set using the program diagram that gives priority to the shutter speed (exposure time) over the aperture value, and in the aperture priority mode, the program diagram that gives priority to the aperture value over the shutter speed is used. The exposure control value is set.

Also in the modes relating to these photographing scenes and the modes relating to the exposure control, the quad switch 32 is used.
Similarly, a desired mode can be set by using.
The set contents are stored in the RAM 87.

The color measurement control section 92 operates each section of the digital still camera 1 in accordance with a predetermined color measurement procedure when the color measurement mode is set as the operation mode. As a functional block, the color measurement procedure display control section 93, coefficient calculator 9
4, a selection unit 95, and a colorimetric calculation unit 96. Details of the operation including the color measurement procedure will be described later with reference to a flowchart and the like.

When the color measurement mode is set, the color measurement control unit 92 fixes the zoom lens 7 and the diaphragm 8 at predetermined positions and operates the analog signal processing circuit 51 and the digital signal processing circuits 53 to 55. Stop the CCD
The image signal output from 16 is subjected to arithmetic processing on the digital value converted by the A / D converter 52.

The colorimetric procedure display control section 93 displays a colorimetric wizard for guiding the user's operation on the external display section 23 when the colorimetric mode is set as the operation mode.

The coefficient calculator 94 calculates a plurality of conversion matrices (a plurality of sets of conversion coefficient groups) based on the pixel data obtained by performing the correction photographing, and stores the calculation results in the EEPROM 86.

The selecting section 95 uses the EEP based on the pixel data output from the CCD 16 when the color measurement object is imaged.
One conversion matrix is selected from a plurality of conversion matrices stored in the ROM 86.

The colorimetric calculation section 96 calculates a colorimetric value using the image pickup result output from the CCD 16 and the conversion matrix selected by the selection section 95.

Next, referring to FIGS. 7 to 12, the operation procedure of the digital still camera 1 according to the color measurement control program will be described according to the flowchart of FIG.

When the colorimetric wizard is selected and the confirmation switch 34 is pressed while the menu screen shown in FIG. 5 is displayed on the external display section 23, the mode is shifted to the colorimetric mode and the routine of FIG. 6 is started. First, correction shooting is performed (# 100).

The subject of the correction shooting is: a white calibration plate for shading correction that corrects the sensitivity variations of the CCD, and a black calibration for which the tristimulus value Y is close to 0 for offset correction that corrects the effects of dark current and stray light. A plate, a gray scale chart consisting of a plurality of gray patches with known different tristimulus values X, Y and Z, and a conversion consisting of a plurality of color patches with known tristimulus values X, Y and Z respectively Matrix creation chart, is used.

At this time, the screen shown in FIG. 7 prompts the user to shoot the white calibration plate, and then the screen shown in FIG. 8 prompts the user to shoot the gray scale chart. Here, as shown in FIGS. 7 and 8, the type of chart to be photographed is displayed on the upper end portion 73 of the display unit 23, and the frame 7 for alignment is displayed.
4 is displayed almost in the center of the display unit 23. Therefore, the user may perform shooting so that each chart fits within this frame 74. Further, subsequently, photographing of the black calibration plate and the conversion matrix creating chart is prompted (not shown).

The gray scale chart and the black calibration plate for offset correction are photographed with an exposure of ± 1 in EV value in addition to the shutter speed (exposure time) of proper exposure,
The conversion matrix creation chart is photographed once with proper exposure. Here, the “appropriate exposure” is the maximum exposure time such that the R, G, and B values of the pixel having the maximum brightness do not overflow. In addition, the frame 74
The position of may be finely adjusted so as to match the chart to be photographed.

When a specific switch or a combination of specific switches of the operation unit 80 is operated (for example, the upper switch 32U of the quad switch 32 and the confirmation switch 34 are simultaneously pressed), the color measurement wizard is terminated. Then, the normal shooting mode may be restored.

Returning to FIG. 6, the correction data is then created using the result of the above-mentioned correction shooting (# 105).
This creation procedure will be described later with reference to FIG.

During the preparation of the correction data, as shown in FIG. 9, the fact that the calculation is in progress indicates that the upper end portion 7 of the external display unit 23 is being operated.
It is displayed in 3. During this time, no operation other than cancellation by the cancel switch 33 is accepted. The calculation for color measurement may be collectively performed after the shooting operation. In that case, the display shown in FIG. 9 and the control for prohibiting operation acceptance other than cancellation are unnecessary.

If the correction data could not be created due to image defects, calculation errors, etc., FIG.
As indicated by 0, an error message is displayed for a predetermined time, and then the normal shooting mode is resumed.

Returning to FIG. 6, next, three kinds of exposure times of the proper exposure time and EV value of ± 1 are taken, that is, the colorimetric object is shot under the same shooting conditions as the correction shooting (#).
110). At this time, on the external display unit 23, a message prompting the user to shoot is displayed on the upper end portion 73 as shown in FIG. Further, when a plurality of shots are required (for example, when the lightness difference of the colorimetric target is large and the shots set to the exposure time of +2 and −2 in EV value are added), that effect is displayed. It is also possible to display a frame 75 capable of measurement with a colorimetric accuracy of a predetermined level or higher as shown in FIG. 12, and prompt the user to arrange a colorimetric object in this frame 75.

Returning to FIG. 6, the calorimetric values are calculated using the photographing result and the correction data (# 115),
The obtained colorimetric value is stored in the EEPROM 86 or the memory card 14 (# 120). This saving is performed in a preset format.

As shown in FIGS. 7 to 12, when the color measurement mode is set, a mark 76 indicating the color measurement mode is displayed at the lower right corner of the external display section 23. Further, the step number 77 of the color measurement procedure is displayed at the lower end.

When the flash light emission is prohibited in the colorimetric mode, a light emission prohibition mark may be displayed in FIGS. 7 to 12.

Further, in the memory card 14, the obtained colorimetric values X, Y, Z are converted into the L * a * b * color system, and the T
It may be stored as an IFF (Tag Image File Format) image. In addition, TIFF images that store R, G, and B values of captured images and JPEG (Joint Photographic coding)
(Experts Group) The colorimetric value may be recorded as a comment in the area for recording the shooting date and time set in the image file.

Next, referring to FIG. 14 to FIG.
The procedure of creating the correction data in # 105 of FIG. 6 will be described with reference to the flowchart of FIG.

In FIG. 13, first, the shading correction data is calculated by using the photographing result of the white calibration plate (# 200). At this time, the G value of a predetermined area at the center of the captured image is used as a reference G value, and the shading correction amount of the G value of each pixel is calculated by P (i, j) = G (i, j) / Gref. Here, P (i, j) is the shading correction amount of the pixel at the position (i, j), and G (i, j) is the position (i, j).
The G value and Gref of the pixel of are the reference G values.

Then, the shading correction amounts of the other pixels R and B are obtained by interpolation using the surrounding G values. For example, shading correction for the R value is performed by R '(i, j) = R (i, j) / P (i, j). However, R '(i, j) is the value after shading correction, and R (i, j) is the R value of the pixel at position (i, j) (value before shading correction).

In the present embodiment, the shading correction amount at each pixel position is obtained using only the G value, but the shading correction amount at each pixel position is calculated using the R value or the B value instead of the G value. You may ask. Further, the shading correction amount of each pixel R, G, B may be obtained by using the R, G, B values respectively.

Next, the R, G, B values of the image for offset correction which has been subjected to the shading correction are set as the offset correction data (# 205). This offset correction data is calculated for each shutter speed (exposure time) for each pixel (i, j).

Alternatively, it may be obtained for each block having a predetermined number of pixels. Further, instead of the black calibration plate for offset correction, R of the gray scale chart,
You may make it calculate using the minimum value of G and B value.

Then, the gamma correction data is calculated (# 210). First, shading correction is performed on the R, G, and B values of each gray patch, and the offset correction data is further subtracted. From the R, G, B values thus obtained and the known Y value, the gamma and slope of each R, G, B value are calculated as gamma correction data. For example, in the case of the R value, it is calculated by the following procedure.

The relationship between the gamma and the slope and the Y value and the R value is represented by R = ^{Ar.Y Gr} . However, Ar is the slope of the R value, and Gr is the gamma of the R value.

When the above equation is modified, Y = (R / Ar) ^{1 / Gr} . Taking the logarithm of this both sides, the _{log 10 Y = (1 / Gr} ) · (log 10 R-log 10 Ar). Here, if log ₁₀ Y = x and log ₁₀ R = y are set,
Linear approximation equation y = a · x + b = Gr · x + log 10 Ar is obtained.

Therefore, when the above linear approximation formula is obtained from the R value and the Y value of each gray patch by using, for example, the least squares method, its coefficient (slope) a = Gr is a gamma of the R value and a constant (intercept) b. = 10 ^b = Ar calculated from log ₁₀ Ar is obtained as the slope of the R value.

Similarly, gamma and slope of G and B values are calculated. The calculation of gamma and inclination is performed for each shutter speed (exposure time). For example, gamma correction of the R value is performed by R '(i, j) = [R (i, j) / Ar] ^{1 / Gr} .

Then, the transformation matrix is obtained (# 21
5). First, shading correction is applied to a captured image of a conversion matrix creating chart, offset correction data is subtracted, and gamma correction is applied to obtain R, G, and B values of each corrected color patch.

Then, in accordance with the following steps (I) to (V), based on the pixel values R, G, B of the respective color patches and the known tristimulus values X, Y, Z, a 3 × 3 first image is obtained. A conversion matrix is created and six 3 × 3 second conversion matrices are created for each hue.

(I) X, Y, Z values of each color patch are L *
The hue H is calculated by converting to the a * b * color system.

This conversion is performed by L * = 116 (Y / Yn) ¹ / 3−16 a * = 500 [(X / Xn) ¹ / 3− (Y / Yn) ^1/3 ] b * = 200 [( Y / Yn) ¹ / 3- (Z / Zn) ^1/3 ] is used. However, Xn, Yn,
Zn is the tristimulus value of the perfect diffuse reflection surface.

Then, the hue H is obtained from H = tan ⁻¹ (b / a).

(II) The hues of R, G, B values and C, M, Y values, which are the center when creating a plurality of (for example, six in this embodiment) conversion matrices, are obtained in accordance with the following steps. . These hues are the center of the divided range that divides the hue range into six, and an example thereof is shown in the innermost ring in FIG.

The spectral sensitivity characteristics R (λ), G (λ), B (λ) of the CCD 16 shown in FIG. 15 and the spectral distribution A (λ) of the illumination light shown in FIG. 16 are obtained.

As the spectral sensitivity characteristic of the CCD 16, for example, the result of inspection at the time of factory shipment may be used. in this case,
An input unit for inputting the spectral sensitivity characteristic may be provided, and
The inspection result may be stored in the EEPROM 86 in advance. Further, the spectral distribution A of the illumination light may be configured so that data can be input from the outside using the switch of the operation unit 80.

The product of the spectral sensitivity characteristics R, G, B of the CCD 16 and the spectral distribution A of the illumination light is obtained, and the spectral sensitivity characteristics RA (λ), GA (λ), BA of the CCD 16 under the illumination light are obtained.
Find (λ). The characteristics RA, GA, BA are shown in FIG.

The tristimulus values X, Y, Z of the illumination light A and the tristimulus values X, Y, Z of the spectral sensitivity characteristics RA, GA, BA are obtained. For example, the tristimulus values Xr, Yr, Zr of the characteristic RA are
It is calculated by the following formula. Xr = ∫RA (λ) x (λ) dλ Yr = ∫RA (λ) y (λ) dλ Zr = ∫RA (λ) z (λ) dλ where x (λ), y (λ), z ( λ) is a color matching function shown in FIG. Further, the integration range is a visible light wavelength range, for example, 38
It is 0 nm to 780 nm.

The tristimulus values Xg, Yg, Zg of the characteristic GA and the tristimulus values Xb, Yb, Zb of the characteristic BA are similarly obtained.

The X, Y, and Z values of the spectral sensitivity characteristics RA, GA, and BA are converted into the L * a * b * color system by using the above-mentioned known conversion formulas, and the X, Y, and Z values are converted into R, G, and B corresponding values. Each hue H is obtained. At this time, the tristimulus values X, Y, Z of the illumination light A obtained above are used as reference whites Xn, Yn, Zn.

By adding 180 ° or π radian to each of the hues H of R, G and B, the hue H of C, M and Y values is obtained. Thus obtained R, G,
The hues of B, C, M and Y are shown in the innermost ring in the chromaticity diagram of FIG.

Instead of steps (1) to (3), general hues of R, G, B values and C, M, Y values of main colors may be used.

Also, in the step, for example, daylight,
The spectral distributions of a plurality of types of illumination light such as fluorescent light and flash light may be stored in the EEPROM 86 in advance, and the spectral distribution to be used may be selected by operating the operation unit 80. When using a flash, it is sufficient to keep ambient light from entering. Further, when the flash is used under a fluorescent lamp, the light amount ratio may be set by the operation unit 80.

In the step, a value that equally divides the hues of R and G values is a hue of Y value, a value that divides the hues of G and B values is the hue of C value, and a hue of B and R values is equal. The divided value may be the hue of M value.

(III) Find the applicable range of the transformation matrix. The hues of the R, G, B, C, M, and Y values obtained by the above procedure are set to 2
A boundary for equal division is calculated, and this boundary is used as a boundary for applying the transformation matrix. That is, as will be described later, an area in which the hue obtained by the tentatively calculated colorimetric value is surrounded by this boundary, for example, areas MR, MG, MB, which are shaded in the second ring from the inside in FIG. For those included in MC, MM, MY, the colorimetric values are calculated using the same conversion matrix.

(IV) The hue range used for creating the conversion matrix is obtained. Regarding the hues of R, G, B, C, M, and Y values determined in step (II), the hue difference with the smaller hue difference among the adjacent colors is calculated, and the hue difference is set to the larger hue difference. The hue range obtained by applying is the hue range used for creating the conversion matrix.

For example, in FIG. 14, of the colors C and M adjacent to the hue of B value, the M value and B that have the smaller hue difference are used.
The hue range B (shown in the outermost circle) obtained by applying the hue difference θ to the C value side, which has the larger hue difference, is used for the conversion matrix creation. Range.

By setting the hue range in this way, the color patches used for creating the conversion matrix are used in duplicate in the adjacent hue ranges, as shown in the outermost circumference and the ring immediately inside thereof in FIG. Will be done. At the boundary of the conversion matrix application range MR, MG, MB, MC, MM, MY, since the conversion matrix to be applied is switched, a step may occur in the conversion result. Since the color patches are set to be used overlappingly in the adjacent hue ranges, it is possible to suppress the occurrence of such a step.

(V) Create a transformation matrix. First, using all the color patches of the conversion matrix creation chart, for example, from the R, G, and B values after gamma correction to X,
A 3 × 3 first conversion matrix Mall for Y and Z values is created.

Of the color patches of the conversion matrix creating chart, only the color patches in the hue range determined in step (IV) are used, for example, from the R, G, B values after gamma correction by the least square method. Six second 3 × 3 conversion matrices Mr, Mg, Mb, Mc, Mm, My to X, Y, Z values are created.

By the above steps (I) to (V), FIG.
The conversion matrix creation step of # 215 is performed, and the routine of FIG. 13 ends.

Next, the procedure of the colorimetric value acquisition step of # 115 of FIG. 6 will be described with reference to the flowchart of FIG.

First, the validity of each pixel in the photographed image to be measured is checked (# 300). That is, for each pixel at an appropriate shutter speed (exposure time), it is confirmed whether the R, G, B values exceed a predetermined value (for example, 245 when the digital value is 8 bits).
For pixels exceeding a predetermined value, pixels of a captured image with a shutter speed (exposure time) that is one step shorter are used.

Similarly, for each pixel, R, G, B
The value is a predetermined value (for example, 1 when the digital value is 8 bits)
Check if it is less than 5). As for pixels less than the predetermined value, the pixels of the captured image whose exposure time is one step longer are used.

Then, shading correction is performed (# 305). That is, for example, if it is an R value, it is corrected by R'k (i, j) = Rk (i, j) / P (i, j). Here, R'k (i, j) is the R value after shading correction of the pixel in (i, j) when the shutter speed is k, and Rk (i, j) is (i when the shutter speed is k , J) is the R value of the pixel, P (i, j) is
It is the shading correction amount of the pixel at (i, j).

Then, offset correction is performed (# 3
10). That is, for example, in the case of the R value, the correction is performed by R ″ k (i, j) = R′k (i, j) −Ork (i, j). However, R ″ k (i, j) is the R value after the offset correction of the pixel at (i, j) when the shutter speed is k, and Ork (i, j) is (when the shutter speed is k) It is the R offset correction amount of the pixel at i, j).

Then, gamma correction is performed (# 31).
5). That is, for example, in the case of the R value, the correction is performed by R ′ ″ k (i, j) = [R ″ k (i, j) / Ark] ^{1 / Grk} . Where R '''k (i, j) is the R value after gamma correction of the pixel at (i, j) when the shutter speed is k, Ark is the slope of the R value when the shutter speed is k, Grk is R when the shutter speed is k
The gamma of the value.

Next, using the first conversion matrix Mall, temporary conversion is performed by the following equation (# 320).

[0155]

[Equation 1]

However, R '''(i, j), G''' (i, j),
B ″ ′ (i, j) is the R, G, B value after gamma correction of the pixel at (i, j), Xt (i, j), Yt (i, j), Zt.
(i, j) is the provisional colorimetric value of the pixel at (i, j), 3 × on the right side
The three matrices are the first conversion matrix Mall.

Next, the provisional colorimetric values Xt, Yt, Zt are converted into the L * a * b * color system by the above known conversion formula, and the hue H is calculated (# 325). Then, the divided hue ranges MR, MM, MB, MC, MG, MY (see FIG. 14).
Of the second ring from the inside), the hue range to which the hue H calculated in # 325 belongs is determined, the second conversion matrix corresponding to the hue range is selected, and the second conversion matrix is selected. Using the following equation, conversion is performed to obtain a colorimetric value (# 330).

[0158]

[Equation 2]

However, X (i, j), Y (i, j), Z (i,
j) is the colorimetric value of the pixel at position (i, j), and is 3 × on the right side.
The 3 matrix is the selected second transformation matrix.

As described above, according to the present embodiment, the first conversion matrix created by using all the color patches of the conversion matrix creation color chart is used to image the measuring object and CCD.
16 tentatively calculates a colorimetric value by the XYZ colorimetric system from the R, G, B values output from 16 and selects one of the plurality of second conversion matrices according to the hue of the tentative colorimetric value. And using the selected second transformation matrix, R, G,
Since the colorimetric value is calculated from the B value, the proper second conversion matrix can be used for the hue of the measurement target, and thus the colorimetric value by the XYZ color system can be accurately obtained. it can.

Further, according to the present embodiment, since the user performs the photographing for correction and obtains the first and second conversion matrices, it is possible to reduce the influence of the change with time of the characteristics of the CCD 16 and the like. Therefore, the highly accurate colorimetric value calculation function can be maintained for a long period of time.

The present invention is not limited to the above embodiment,
The following modifications can be adopted.

(1) In the above embodiment, the calorimetric values are calculated in the digital still camera 1, but the invention is not limited to this. For example, as shown in FIG. 4, a personal computer (PC) 113 may be connected to the digital still camera 1 to cause the PC 113 to perform arithmetic processing and the like.

In this embodiment, the digital still camera 1
Has a colorimetry mode as in the above embodiment, and performs correction photography and colorimetry target photography in the same procedure. Then, the obtained image data is sent to the PC 1 via the communication cable.
The data is sent to the PC 13, and the PC 113 calculates correction data and colorimetric values.

The image data may be sent to the PC 113 via the memory card 14 instead of the communication cable.

(2) In the above embodiment, the correction data and the colorimetric value are calculated for each pixel, but the present invention is not limited to this. For example, it may be performed for each block including a predetermined number of pixels. Further, as shown in FIG. 20, the patch areas 114 including a predetermined number of pixels may be set at predetermined intervals, and each value may be calculated using the average value of the pixels included in the patch area 114.

According to this modification, the time required for calculating the correction data and the colorimetric value can be shortened as compared with the above-described embodiment, and it is effective for the colorimetric object in which the color does not change finely.

(3) Further, only the shading correction data and the offset correction data are applied to the patch area 11 shown in FIG.
It is calculated for each 4 pixels, and the colorimetric value is calculated for each pixel (i, j).
You may carry out every. In this case, the pixel (i,
The correction data in j) may be obtained by interpolating surrounding data.

(4) When an object in which the same color is distributed over a certain area, such as a color chart, is to be measured, R and G are used by using pixel data of only a highly reliable region in the photographed image. , B values may be averaged, and the colorimetric value may be calculated using the average value. Here, the highly reliable region is, for example, a predetermined region near the center of the measurement target. The correction data may be calculated using the measurement value of the pixel at the center of the area.

This area may be designated, for example, by operating the quad switch 32 or by a mouse connected to the PC 113.

It is also possible to cover the measurement object other than this area with a matte black cover so that only the colorimetric area is exposed for photographing. As a result, R, G, and
It is possible to prevent the B value from being changed by being pulled by the brightness of the peripheral region, and to accurately calculate the colorimetric value.

(5) In the above embodiment, a 3 × 3 matrix is used as the transformation matrix, but the present invention is not limited to this, and 3 × n is used.
May be used. For example, as shown in the following equation, R,
A 3 × 4 matrix in which a constant term is added in addition to the G and B values may be used. According to this aspect, it is possible to add an offset in the numerical conversion, which allows the colorimetric value to be calculated with higher accuracy.

[0173]

[Equation 3]

Further, as shown in the following equation, a 3 × 11 matrix in which a quadratic term and a cubic term are added in addition to the primary term of the R, G, B values may be used. According to this aspect, it is possible to perform the numerical conversion in consideration of the non-linearity of the spectral sensitivity characteristic of each CCD of the area sensor 17 that constitutes the CCD 16 and the spectral transmission characteristic of the color filter 18 (see FIG. 3). The colorimetric value can be calculated accurately.

[0175]

[Equation 4]

(6) In the above-described embodiment, the user performs the photographing for correction, obtains the first and second conversion matrices, and EEPRO.
It is stored in M86, but is not limited to this. Before the digital still camera 1 is shipped from the factory, correction photographing is performed in advance to obtain the first and second conversion matrices, and the result is EE
It may be stored in the PROM 86. In this case, the correction shooting may be performed under various shooting conditions such as illumination light so that the user can select it when the color measurement is performed.

According to this aspect, it is possible to save the user the trouble of taking the image for correction, and it is possible to perform the color measurement more easily.

(7) In the above embodiment, the correction photographing is performed every time the colorimetric mode is set, but the invention is not limited to this. When the shooting conditions such as the position of the zoom lens and the focus lens and the illumination light are fixed, # 100 and # 105 in FIG. 6 are performed only once and the result is EEP.
It may be stored in the ROM 86 and not performed again.

(8) In the above embodiment, the overall controller 90
The control program is stored in the EEPROM 86, but the control program is not limited to this. For example, a control program including a colorimetric control program including the routines shown in FIGS. 6, 13, and 19 may be stored in the memory card 14 and downloaded to the EEPROM 86 or the RAM 87.

[0180]

As described above, according to claims 1, 8 and
According to the inventions of 9 and 10, a plurality of sets of conversion coefficient groups for converting a three-primary-color image signal into a colorimetric value based on a predetermined standard three-color color system are stored, and a color is recorded when a measurement target is imaged. According to the three primary color image signals output from the image pickup means, select one set of conversion coefficient group from the plurality of sets of conversion coefficient group,
Since the colorimetric values based on the standard three-color color system are calculated from the three primary color image signals obtained by the color image pickup means using the selected conversion coefficient group, the three primary colors obtained by the image pickup of the measurement target Since the conversion coefficient group suitable for the image signal is selected, the colorimetric value based on the standard three-color color system can be accurately obtained.

According to the second aspect of the invention, the digital still camera including the color image pickup means and the personal computer including the storage means, the selection means and the conversion calculation means are provided, and the three primary color image signals are transmitted from the digital still camera to the personal computer. Since I am trying to transmit to a computer,
The calculation load on the digital still camera can be reduced.

According to the third aspect of the present invention, the colorimetric mode is set by the operating means, so that the colorimetric value based on the standard three-color color system of the measuring object can be easily and accurately set by using the digital still camera. It is possible to calculate well.

According to the invention of claim 4, since the photographing procedure for color measurement is displayed on the display means when the color measurement mode is set, even for a user who is unfamiliar with the color measurement operation, It is possible to reliably perform color measurement.

According to the invention of claim 5, a plurality of sets of conversion coefficient groups are obtained by imaging a plurality of correction subjects whose colorimetric values based on the standard three-color color system are known by the color imaging means. Since it is determined based on the relationship between the three primary color image signals and the known colorimetric value, by using these conversion coefficient groups, the standard three color system from the three primary color image signals when the measurement target is imaged. The colorimetric value based on can be accurately obtained.

According to the invention of claim 6, a colorimetric value based on the standard three-color color system is provisionally calculated from the three primary color image signals obtained by imaging the object to be measured by the color imaging means using the first conversion coefficient group. Then, the hue value is calculated using the result, and one set of second conversion coefficient groups corresponding to the hue value is selected from the plurality of sets of second conversion coefficient groups. Since the colorimetric values based on the standard three-color color system are calculated using the second conversion coefficient group, the colorimetric values can be calculated with higher accuracy.

According to the invention of claim 7, a plurality of three primary color image signals obtained by picking up a plurality of correction subjects whose colorimetric values based on the standard three-color color system are known by the color image pickup means, and the known three primary color image signals. Since a plurality of sets of conversion coefficient groups are calculated based on the relationship with the colorimetric value of, and the calculation results are stored in the storage means, even if the spectral characteristics of the color image pickup means change with time, By newly calculating the conversion coefficient group of and storing it in the storage means, it is possible to maintain a highly accurate colorimetric value calculation function for a long period of time.

[Brief description of drawings]

FIG. 1 is a top view showing an arrangement of main members incorporated in a digital still camera which is an embodiment of a color measuring device according to the present invention.

FIG. 2 is a rear view of the digital still camera.

FIG. 3 is a diagram illustrating a configuration of a color image sensor.

FIG. 4 is a block diagram showing an electrical configuration of a digital still camera.

FIG. 5 is a diagram showing an example of a menu screen displayed on an external display unit when an operation mode is selected.

FIG. 6 is a flowchart showing a main routine of a color measurement operation procedure.

FIG. 7 is a diagram showing an example of a screen displayed on an external display unit as a color measurement wizard.

FIG. 8 is a diagram showing an example of a screen displayed on an external display unit as a color measurement wizard.

FIG. 9 is a diagram showing an example of a screen displayed on an external display unit as a color measurement wizard.

FIG. 10 is a diagram showing an example of a screen displayed on an external display unit as a color measurement wizard.

FIG. 11 is a diagram showing an example of a screen displayed on the external display unit as a color measurement wizard.

FIG. 12 is a diagram showing an example of a screen displayed on an external display unit as a color measurement wizard.

FIG. 13 is a flowchart showing a procedure of a correction data creation subroutine.

FIG. 14 is a chromaticity diagram of the L * a * b color system for explaining the creation of a conversion matrix.

FIG. 15 is a diagram showing a spectral sensitivity characteristic of a CCD.

FIG. 16 is a diagram showing a spectral luminance characteristic of a fluorescent lamp as an example of illumination light.

17 is a diagram showing a product of the characteristic shown in FIG. 14 and the characteristic shown in FIG.

FIG. 18: Color matching functions x (λ), y of tristimulus values X, Y, Z
It is a figure which shows ((lambda)) and z ((lambda)).

19 is a flowchart showing a colorimetric value acquisition subroutine of # 115 in FIG.

FIG. 20 is a diagram showing an area provided with a correction pixel and a predetermined number of pixels for calculating a colorimetric value, which is provided on the imaging surface.

[Explanation of symbols]

14 Memory card (recording medium) 16 CCD (color image pickup means) 23 External display 80 Operation unit (operation means) 86 EEPROM (storage means) 90 Overall control unit 91 Shooting mode control unit 92 Color measurement control section 93 Colorimetric procedure display control unit 94 Coefficient calculation unit 95 Selector 96 Colorimetric calculator (conversion calculator)

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) // H04N 101: 00 H04N 101: 00 F term (reference) 2G020 AA04 AA08 DA12 DA23 DA34 DA65 2H054 AA01 5C065 AA03 BB48 DD02 EE03 FF02 GG26 5C066 AA01 CA17 EC03 EC05 GA01 KE01 KE04 KE07 KM05 KM13

Claims (10)

[Claims] 1. A color image pickup means for receiving an optical image of an object to be measured through a photographing optical system and outputting predetermined three-primary-color image signals corresponding to the light intensity, and a standard standard three-color table for the three-primary-color image signals. A storage unit that stores a plurality of sets of conversion coefficient groups for converting colorimetric values based on a color system, and a plurality of sets of the plurality of sets according to the three primary color image signals output from the color image pickup unit when the measurement target is imaged Selecting means for selecting a set of conversion coefficient groups from the conversion coefficient group, and using the conversion coefficient group selected by the selecting means, from the three primary color image signals obtained by the color image pickup means to the standard three color system A colorimetric apparatus, comprising: a conversion calculation unit that calculates a colorimetric value based on the colorimetric value. 2. A digital still camera including the color image pickup means, and a personal computer including the storage means, a selection means, and a conversion calculation means, wherein the digital still camera includes the digital still camera and the personal computer. The personal computer includes a transmitting unit that transmits the three primary color image signals output from the color image capturing unit to the personal computer, and the personal computer includes a receiving unit that receives the three primary color image signals transmitted from the digital still camera. The color measurement device according to claim 1, wherein the color measurement device is a color measurement device. 3. The color image pickup means, the selection means, and the conversion calculation means are arranged in a digital still camera, and the digital still camera can be operated from the outside to set a colorimetric mode as a photographing mode. 2. The colorimetric apparatus according to claim 1, further comprising various operating means, wherein the selecting means and the conversion computing means operate when the colorimetric mode is set. 4. The digital still camera comprises display means and display control means for displaying a photographing procedure for color measurement on the display means when the color measurement mode is set. The color measurement device according to claim 3, wherein the color measurement device is a color measurement device. 5. The plurality of sets of conversion coefficient groups stored in the storage means capture a plurality of correction subjects whose colorimetric values based on the standard three-color color system are known by the color imaging means. The colorimetric apparatus according to claim 1, wherein the colorimetric apparatus is obtained based on a relationship between a plurality of obtained three primary color image signals and the known colorimetric value. 6. A plurality of sets of conversion coefficient groups stored in the storage means, and a set of first conversion coefficient groups obtained by using all of the plurality of correction subjects, and a hue value within a predetermined range. And a plurality of sets of second conversion coefficient groups respectively obtained by using a predetermined number of correction subjects belonging to the three primary color image signals obtained by imaging the measurement target by the color imaging means. Then, a colorimetric value based on the standard three-color color system is tentatively calculated using the first conversion coefficient group, and a hue value is calculated using the result, and the hue value is calculated from the plurality of sets of the second conversion coefficient group. The colorimetric apparatus according to claim 5, wherein a set of second conversion coefficient groups corresponding to the hue value is selected. 7. A plurality of the three primary color image signals obtained by imaging a plurality of correction subjects whose colorimetric values based on the standard three-color color system are known by the color imaging means and the known colorimetric values. 5. The colorimetric apparatus according to claim 1, further comprising a coefficient calculation unit that calculates a plurality of sets of the conversion coefficient groups based on the relationship and stores the calculation results in the storage unit. . 8. A plurality of sets of conversion coefficient groups for converting the three primary color image signals into colorimetric values based on a predetermined standard three-color color system are stored, and an optical image of an object to be measured is taken through a photographing optical system. From a plurality of conversion coefficient groups corresponding to the three primary color image signals output when the object to be measured is imaged from the color image pickup means that receives predetermined three primary color image signals according to the light intensity Is selected, and a colorimetric value based on the standard three-color color system is calculated from the three primary color image signals obtained by the color image pickup means using the selected conversion coefficient group. Color measurement method. 9. A colorimetric control program for measuring a color of an object to be measured, which receives an optical image of the object to be measured through a photographing optical system and outputs predetermined three primary color image signals corresponding to the light intensity. A colorimetric device having a color image pickup means for storing the three primary color image signals and a storage means for storing a plurality of conversion coefficient groups for converting the three primary color image signals into colorimetric values based on a predetermined standard three color system. Selecting means for selecting one set of conversion coefficient groups from the plurality of sets of conversion coefficient groups in accordance with the three primary color image signals output from the color image pickup means when the image is captured, and the conversion coefficient selected by the selecting means. A colorimetric control program which functions as a conversion operation means for calculating a colorimetric value based on the standard three-color color system from the three primary color image signals obtained by the color imaging means using a group. 10. A computer-readable recording medium in which the colorimetric control program according to claim 9 is stored.