JPH07203476A - Color image converter - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a color image conversion device that converts a color image captured by a color image capturing device into a stable signal that can be handled by a monochrome image processing device in a short time and outputs the stable signal. [Constitution] A video signal picked up by a color image pickup device is converted into color components, and a color difference between each pixel and the reference color is obtained from the color component of each pixel and the color component of a reference color registered in advance. , And outputs a signal level corresponding to the color difference to the monochromatic image processing device. In addition, the video signal captured by the color imaging device is converted into a hue component, and the hue difference between each pixel and the reference color is obtained from the color component of each pixel and the color component of the reference color registered in advance. , And outputs a signal level corresponding to the hue difference to the monochromatic image processing device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image conversion device for converting a color image picked up by a color image pickup device into a monochromatic image.

[0002]

2. Description of the Related Art Conventionally, image processing apparatuses have been used for visual inspection of products in a factory automation line or the like, but most of them are simple color image processing apparatuses having a simple structure. However, since the single-color image processing device performs processing only by the light and shade of the image, that is, the lightness, if there is no lightness difference even if the colors are different, the difference cannot be detected and the inspection becomes impossible. In addition, brightness is an amount that depends on the amount of illumination light, and is strongly affected by uneven lighting and fluctuations in illumination.
Brightness measurement requires homogeneous and stable illumination. Therefore, the burden of installing and maintaining such lighting equipment becomes large. On the other hand, in order to overcome the above-mentioned problems of the monochromatic image processing device, a dedicated color image processing device has been used. However, the use of these devices is limited due to their high price and complicated operation. In addition, a user who is already using the monochromatic image processing device may not be able to handle monochromatic image processing due to an increase or change in the inspection product type. In addition, if color image processing is required due to a demand for improved inspection accuracy, introducing a new color image processing device causes waste in terms of cost, and a great deal of effort is required to learn the operation of the new device and change the system. It costs.

[0003]

Therefore, an image conversion apparatus is conceivable for converting a color image picked up by a color image pick-up apparatus into a monochromatic image which can be handled by a monochromatic image processing apparatus by some method. In this case, since it may be added as an adapter in front of the monochromatic image processing apparatus, the cost and labor involved in the introduction can be reduced. The following is an example of such an image conversion device. In the "color television camera for image processing" described in Japanese Patent Application Laid-Open No. 2-92089, a hue signal, a saturation signal, and a luminance signal (corresponding to brightness) are each output as a monochromatic image signal from the television camera. In this color television camera for image processing, signals of hue, saturation, and lightness are each output as a single-color image signal. However, the hue signal proposed here has the following disadvantages. is there.

FIG. 1 shows an example of a chromaticity plane of a certain color space. In FIG. 1, four colors C indicated by black dots
The hues of 1, C2, C3, and C4 are the angles θ, respectively.
It becomes 1, θ2, θ3 and 0. FIG. 2 shows an example of an image containing these four colors C1, C2, C3 and C4.
Here, the level of the output hue signal is 0 ° = 0V,
When the hue is determined to be 360 ° = 0.7 V, the hue signal on the scanning line indicated by the alternate long and short dash line in the image shown in FIG. 2 becomes as shown in FIG. 3 in one horizontal scanning period H. That is, after the horizontal synchronizing signal is output, the colors C1, C2, C1, C
Signals corresponding to the hues of 3, C1, C4, and C1 are output. Since C1 has a hue close to 0 °, it is close to 0V, and C3 has a hue close to 360 °, and thus has a level close to 0.7V, and C2 has a level close to 180 °, and therefore has an intermediate signal level. . In this case, C1 and C2 or C2 and C
In the relationship of 3, the difference in hue and the difference in signal level match, but C
Although there is a very small difference in hue between 1 and C3, there is a problem in that the signal levels greatly differ. further,
As shown in FIG. 3, for a color such as C4 near the hue of 0 °, the signal level reciprocates between 0V and 0.7V and becomes extremely unstable. This phenomenon is an essential problem of the concept of hue regardless of the relationship between the type of color space or the value of hue and the output signal level. Therefore, using the hue signal is practically problematic. In addition, the monochromatic image processing device is
Many have only one input terminal. In this case, it is necessary to prepare an external switching device to sequentially switch the signals of hue, saturation and lightness for processing. Even in a device having a plurality of input terminals, the processing is sequentially switched internally, so that the processing time becomes long in any case. Moreover, since three signals cannot be processed simultaneously, it cannot be applied to a moving object.

Further, the present inventors have disclosed in JP-A-5-21560.
The “color image extracting device” proposed in Japanese Patent Publication No. 9 extracts an image of a designated reference color from a video signal picked up by a color image pickup device and outputs it as a monochromatic binary image. The image conversion by the color image extracting device does not have the inconvenience of the color television camera for image processing described above. However, this image conversion device can be applied to an image in which it is easy to extract a region by color, but cannot be applied to an arbitrary image in which there is no clear color boundary. Further, since the output is a binary image, it cannot be applied to grayscale image processing that handles a multivalued monochromatic image.

It is a first object of the present invention to provide a color image conversion device for converting a color image picked up by a color image pick-up device into a stable signal which can be handled by a monochromatic image processing device and outputting the signal. A second object of the present invention is to provide a color image conversion device that converts a color image captured by a color image capturing device into one signal that can be handled by a single color image processing device and outputs the signal in a short processing time.

[0007]

A first color image conversion apparatus according to the present invention includes a color component conversion unit for converting a video signal picked up by a color image pickup apparatus into color components, and a color component for a reference color. Reference color registration means for registering, color difference calculation means for obtaining a color difference between the color of each pixel and the reference color from the color component of each pixel converted by the color component conversion means and the color component of the reference color registered in advance, An image output means for outputting a monochromatic image signal having a signal level corresponding to the obtained color difference value is provided. A second color image conversion apparatus according to the present invention includes a hue conversion unit that converts a video signal captured by a color imaging apparatus into a hue, a reference color registration unit that registers the hue of a reference color, and a hue conversion unit. It comprises a hue difference calculation means for obtaining a hue difference between the color of each pixel and the reference color from the hue of each pixel and the hue of the reference color registered in advance, and a signal level corresponding to the value of the obtained hue difference. An image output means for outputting a monochromatic image signal is provided.

[0008]

In the color image conversion device, it is preferable that the number of signals converted from the video signal to be sent to the monochromatic image processing device is one, and the signal level becomes unstable in a specific color. It should not occur. Therefore, in the present invention, the color video signal is converted into a signal which is essentially stable against a color change such as a color difference or a hue difference,
Output to a monochromatic image processing device. In the first color image conversion device according to the present invention, the color difference between each pixel and the reference color is obtained from the color component of each pixel converted from the video signal and the color component of the reference color registered in advance, The signal level corresponding to the color difference is output. FIG. 2 shows four colors C1, C2, C3 and C.
An example of an image including 4 is shown. When the color difference between the pixels C2, C3, and C4 in FIG. 2 is obtained when C1 in FIG. 1 is used as the reference color, the color difference between C1 and C2 is E2,
The color difference between C1 and C3 is E3, and the color difference between C1 and C4 is E
It becomes 4. (However, for the sake of explanation, it is assumed that all colors have the same lightness and are on the same chromaticity plane.)
In this case, the output signal on the scanning line indicated by the alternate long and short dash line in the image shown in FIG. 2 is as shown in FIG. 4 in one horizontal scanning period H. That is, after the horizontal synchronizing signal is output, the signals corresponding to the color differences of the colors C1, C2, C1, C3, C1, C4, and C1 are sequentially output. As shown in FIG. 4, the larger the color difference, the larger the signal level. Therefore,
Unstable output values for a particular color do not occur. Here, the minimum color difference value and the maximum color difference value are set to 0V and 0.7V, respectively. The inconvenience of an unstable phenomenon in a specific color as shown in FIG. 3 does not occur in the conventional color television camera for image processing. Further, since there is only one signal, there is no need for a switcher or the like for inputting to one input terminal of the monochromatic image processing device, and the monochromatic image processing device can easily handle it. Furthermore, it can be applied to arbitrary images.

Further, in the second color image conversion apparatus according to the present invention, the color of each pixel and the color of the reference color are calculated from the hue of each pixel converted from the video signal and the hue of the reference color registered in advance. The phase difference is obtained and a signal level corresponding to the hue difference is output. In the above-mentioned FIG. 1, each pixel C in FIG.
When the hue difference between C2, C3 and C4 is calculated, the hue difference between C1 and C2 is H2 when C1 is the reference color, and
The hue difference between C1 and C3 is H3, and the hue difference between C1 and C4 is H
It becomes 4. In this case, the output signal on the scanning line indicated by the alternate long and short dash line of the image shown in FIG. 2 is as shown in FIG. 5 in one horizontal scanning period H. That is, after the horizontal synchronizing signal is output, the colors C1, C2, C1, C3, C
A signal corresponding to the hue difference of 1, C4 and C1 is output.
As shown in FIG. 5, the larger the hue difference, the larger the signal level. Also in this case, as in the first color image conversion apparatus, the inconvenience phenomenon of an instability in a specific color does not occur. Here, the level of the hue difference signal to be output is 0 V for the minimum value of the hue difference and 0.7 V for the maximum value of the hue difference.
Stipulate.

[0010]

Embodiments of the color image conversion apparatus of the present invention will be described below with reference to the accompanying drawings. FIG. 6 shows an embodiment of the first color image conversion apparatus according to the present invention. less than,
The color image conversion device will be described with reference to FIG. The RGB analog signal from the color image pickup camera 1 is L ^* , a ^* , b ^* conversion circuit 2 in the color image conversion device indicated by the broken line to L ^* ,
Converted to digital values corresponding to a ^* and b ^* values. Conversion from the RGB color system to the L ^* a ^* b ^* color system is known and will not be described here. Next, the color difference calculation circuit 6 converts the converted L
^{From the *} , a ^* , b ^* values and the L ^* ₀ , a ^* ₀ , b ^* ₀ output from the reference color registration operation control unit 10, that is, the L ^* , a ^* , b ^* values of the reference color, The color difference ΔE ^* represented by (1) is calculated and output.

[Number 1] ^{△ E * = ((L *} -L * 0) 2 + (a * -a * 0) 2 + (b * -b * 0) 2) 1/2 (1)

Next, the color difference ΔE obtained by the color difference calculation circuit 6
^The gradation of ^* is converted by the gradation conversion circuit 7. The reason for gradation conversion is as follows. Since the level of the monochromatic image signal is generally 0.7 VPP, it is necessary to perform scaling so that the color difference value and the signal level of the monochromatic image signal match. For example, if color difference = 0 is fixed to 0V and the maximum possible color difference is fixed to 0.7V, gradation conversion is not necessary, but in this case, the signal level of an image without a small color difference becomes extremely small and the resolution is reduced. Is reduced. Therefore, the gradation conversion circuit 7 performs full-scale adjustment so that the level becomes appropriate. (For example, 0 to 20 color difference
Convert to 0.7V. ) In addition, D of color difference ΔE ^*
There is a method of changing the amplification factor of the analog circuit after the A conversion, but it is disadvantageous in terms of S / N ratio. In addition, if the gradation conversion circuit is configured by a look-up table, not only full scale adjustment but also a specific color difference range (for example, a range of color difference 10 to 20) is adjusted to be 0 to 0.7V. You can also easily perform non-linear conversion. Next, DA
The conversion circuit 8 converts the digital value from the gradation conversion circuit 7 into an analog signal. The first image composition circuit 9
The analog signal from the A conversion circuit 8 and the synchronizing signal included in the video signal from the color camera 1 are combined and output to the monochromatic image processing device 15 as a monochromatic image signal.

In this color image conversion device, the reference color is registered by (1) on the monitor screen displaying the captured image,
Area designating means for designating a desired area, (2) registration period designating means for designating a period for registering a reference color, and (3)
The area designated by the area designating means is included in either the color range of the video signal included in the period designated by the registration period designating means or the color range already stored in the color range storing means. This is performed using a color range storage unit that newly stores a color as a reference color range.

Specifically, the video signal from the color camera 1 is combined with the output of the window generating circuit 11 and the second image combining circuit 14, and the monitor TV 16 displays the original image and the window. The user operates the cursor button 13 while watching the image on the monitor television 16 to move the window to a desired area on the screen and specify the area desired to be set as the reference color. Next, when the user presses the registration button 1, all the colors L ^* , a ^* included in the period in which the registration button 1 is pressed in the area set in the window are instructed by the reference color registration operation control unit 10. b ^*
Are stored in the reference L ^* memory 3, the reference a ^* memory 4, and the reference b ^* memory 5, respectively. When the registration button 12 is released, the reference color registration operation control unit 10 reads out the contents of each memory, obtains the median value of each range of L ^* , a ^* , and b ^* , and sets the reference color data in the color difference calculation circuit 6. Output.

FIG. 7 shows an embodiment of the second color image conversion apparatus according to the present invention. The color image conversion device will be described below with reference to FIG. 7. First, RGB analog signal from the color imaging camera 101, L ^* in the color image converter shown in broken lines, a ^*, b ^* by the conversion circuit 102 L ^*, a ^*, is converted into a digital value corresponding to the b ^* values It The transformed L ^* , a
^{The *} and b ^* values are further converted into the hue H represented by the equation (2) by the hue calculation circuit 103.

H = tan ^-1 (b ^* / a ^* ) (a ^* >0; b ^* > 0) H = tan ^-1 (b ^* / a ^* ) + 360 ° (a ^* >0; b ^* < 0) (2) H = tan ⁻¹ (b ^* / a ^* ) + 180 ° (a ^* <0)

Next, the hue difference calculation circuit 105 calculates from the hue calculated by the hue calculation circuit 103 and the hue H _{0 of the} reference color output from the reference color registration operation control unit 109 from the equation (3).
The hue difference ΔH represented by is calculated.

Equation 3] △ H = ABS (H-H 0) (3) The computed hue difference △ H, since the signal level value of the hue difference and monochrome image signal is a properly scaled to match, The gradation conversion circuit 106 performs gradation conversion.
The DA conversion circuit 107 converts the digital value from the gradation conversion circuit 106 into an analog signal. First image composition circuit 1
Reference numeral 08 synthesizes the analog signal from the DA conversion circuit 107 and the synchronization signal included in the video signal from the color camera 101 and outputs the synthesized signal to the monochromatic image processing device 114 as a monochromatic image signal.

In this color image converting apparatus, the reference color is registered as follows. First, the video signal from the color camera 101 is synthesized by the output of the window generation circuit 110 and the second image synthesis circuit 113, and the monitor television 11
An original image and a window are displayed at 5. By operating the cursor button 112 while watching the image on the monitor television 115, the window is moved to a desired area on the screen and the area desired to be set as the reference color is designated. Next, when the registration button 111 is pressed, the reference color registration operation control unit 109
In response to the command, the range of the hue H of all the colors included in the period in which the registration button 111 is pressed in the area set in the window is stored in the reference H memory 104. When the registration button 111 is released, the reference color registration operation control unit 109
Reads the contents of the reference H memory 104, obtains the median value of the range of hue H, and outputs it to the hue difference calculation circuit 105 as reference color data.

In the first and second embodiments described above, registration signals from the outside may be used instead of the registration buttons 12 and 111. Cursor buttons 13, 112
Instead of, a mouse or the like may be used. Also, RS23
A registration instruction may be given by communication such as 2C. Further, in setting the reference color, the median value of the values stored in the reference H memory 104 is used, but a simple average value or an average value of data from which abnormal values are deleted may be used.

In the first embodiment described above, the color difference ΔE ^*
Although the color image conversion apparatus using is described, the color difference ΔE! Described next may be used. In this case, the tristimulus X, Y, and Z values of the XYZ color system are converted into the values a! And b! Of the Lab color system, as in the following Expression (4).

[Expression 4] a! = 500 (Y ₀ X / X ₀ Y) ^1/3 −1) (4) b! = 200 (1− (Y ₀ Z / Z ₀ Y) ^1/3 ) where X ₀ , Y ₀ , Z ₀ represent white X, Y, Z values. Here, the color difference ΔE! Calculated by the color difference calculation circuit 210 is a normalized color difference defined by the following equation (5).

[Equation 5] ΔE! = ((A! −a ₀ !) ² + (b! −b ₀ !) ² ) ^1/2 (5) where a ₀ !, B ₀ ! Represents!, B!

Color difference ΔE! Used in this modification.
Are not affected by the fluctuation of the light amount L.
That is, the light amount L is not included in the equation (5). Therefore, there is an advantage that the influence of uneven lighting can be avoided. Table 1 shows the color difference ΔE ^* when the amount of light changes ^.
This is an example showing the behavior of ΔE! In Table 1, A
When the light intensity of a color is changed to a reference color and the light intensity is halved, ΔE ^* has a color difference of 19.3 for the same color, which is larger than the original color difference A and B of 9.7. Therefore, it is impossible to distinguish the two colors under such a severe condition.
On the other hand, with ΔE !, there is no color difference even if the light intensity changes,
The two colors are sufficiently distinguishable.

[0020]

[Table 1]

However, ΔE! Has the following problems. (1) Since ΔE ^* is a uniform perceptual color difference, the human sense and its numerical value match, but ΔE! Does not necessarily match the human sense. (2) Since no brightness component is included, it is not possible to distinguish between colors that differ only in brightness. Therefore, the color difference
E! Is effective when there is no need to match the human sense, there is no inspection object in which the difference in brightness is dominant, and fluctuations in the amount of illumination light are large. Of course, it is possible to use a switch or the like to switch between two types of color differences depending on the application and the inspection object.

Next, as a modification of the color image conversion apparatus,
A color image conversion device for easily switching between E ^* and ΔE! Will be described. In this modification, the color component conversion is performed by converting (1) R, G, B analog signals captured by the color image capturing device into X,
XYZ conversion means for converting into Y and Z analog signals,
(2) Digitizing means for converting each of the X, Y, Z analog signals into digital values, and (3) a bit string composed of Y digital values, the output of which is connected to the address terminal of the Y digitizing means. L corresponding to the Y value at the fixed address
^The L ^* memory storing the value of ^* and (4) the outputs of the digitizing means of X and Y are connected to the address terminals, and the addresses of X and Y are determined by the bit string composed of the digital values of X and Y. A ^* memory storing the value of a ^* corresponding to the value and (5) the outputs of the Y and Z digitizing means are connected to the address terminals,
This is performed using a b ^* memory in which the value of b ^* corresponding to the values of Y and Z is stored at an address determined by a bit string composed of digital values of Y and Z.

In this color image conversion apparatus, La shown in FIG.
The b conversion circuit is used. In this Lab conversion circuit, the tristimulus X, Y, Z values of the XYZ color system are converted into the values a !, b! Of the Lab color system, as in the following equation (6).

## EQU6 ## L ^* = 116 * (Y / 100) ¹ / 3-16 a ^* = 500 * {(X / 98.1) ¹ / 3- (Y / 100) ^1/3 } (6) b ^* = 200 * {(Y / 100) ¹ / 3- (Z / 118.2) ^1/3 } The Lab conversion circuit will be described.
The analog video signal from 1 is converted by the XYZ conversion circuit 202 into X, Y, and Z signals of the XYZ color system. These Y, X, and Z signals are converted into AD converters 203 and 20, respectively.
ROM for L as an 8-bit digital value from 4, 205
206, ROM for a 207, and ROM for b 208. Here, the ROM 206 for L, the ROM 207 for a, and the ROM 208 for b are 128 Kbytes (address lines A0 to A0).
A16 17) ROM, address terminal A16
Is connected to the switch 209.

Address terminals A0 to A of the ROM 206 for L
7 is connected to the output Y of the AD converter 203, and the address terminals A8 to A15 are fixed to "0". When the address terminal A16 is "0", the address terminal A0
The address determined by the bit string of ~A7 corresponding to the Y value L ^*
Value is written, and "0" is written in other addresses. Therefore, by switching the switch 209, the L ^* ROM 206 outputs the L ^* value or "0" corresponding to the Y value.

Further, the address terminal A of the ROM 207 for a
0 to A7 are connected to the output of the AD converter 203, and the address terminals A8 to A15 are connected to the output X of the AD converter 204. Further, when A16 is "0", the value of a ^* corresponding to the X value and the Y value is written in the address determined by the bit string of the address terminals A0 to A15. When the address terminal A16 is "1", the address terminals A0 to A0 are written. The address determined by the bit string of A15 corresponds to X value and Y value a!
The value of is written. Therefore, by switching the switch 209, the a ^* value or the a! Value corresponding to the X value and the Y value is output from the ROM 207 for a.

Further, the address terminals A0 to A7 of the ROM 208 for b are connected to the output of the AD converter 205, and the address terminals A8 to A15 are connected to the output of the AD converter 203. When the address terminal A16 is "0", the value of b ^* corresponding to the Y value and the Z value is written in the address determined by the bit string of the address terminals A0 to A15. A
The value of b! Corresponding to the Y value and the Z value is written in the address determined by the bit string of 0 to A15. Therefore, by switching the switch 209, the b ROM value 208 outputs the b ^* value or the b! Value corresponding to the Y value and the Z value. The color difference calculation circuit 210

Equation 7] △ E = ((L-L 0) 2 + (a-a 0) 2 + (b-b 0) 2) may be calculating ^1/2 (7). However, L ₀ , a ₀ , and b ₀ are the reference colors L, a, and b. Further, in the case of ΔE !, L and L ₀ are 0.
Is.

[0027]

The color image conversion apparatus according to the present invention can convert a color image captured by the color image capturing apparatus into a stable signal that can be handled by the single color image processing apparatus and output the signal to the single color image processing apparatus. The color image conversion device according to the present invention can convert a color image captured by the color image capturing device into one signal that can be handled by the monochrome image processing device, and output the signal to the monochrome image processing device in a short processing time.

[Brief description of drawings]

FIG. 1 is a graph showing an example of a chromaticity plane of a color space.

FIG. 2 is a diagram of an example of an image including four colors C1, C2, C3 and C4.

FIG. 3 is a diagram of a hue signal on a scanning line indicated by a chain line of the image shown in FIG.

FIG. 4 is a diagram of color difference signals on a scanning line indicated by a chain line of the image shown in FIG.

5 is a diagram of a hue difference signal on a scanning line indicated by an alternate long and short dash line of the image shown in FIG.

FIG. 6 is a block diagram of a first color image conversion device according to the present invention.

FIG. 7 is a block diagram of a second color image conversion device according to the present invention.

FIG. 8 is a block diagram of a Lab conversion circuit used in a color image conversion device that can easily switch between ΔE ^* and ΔE !.

[Explanation of symbols]

1 ... Color camera, 2 ... Lab conversion circuit, 3, 4,
5 ... Reference memory, 6 ... Color difference calculation circuit, 101 ... Color camera, 102 ... L ^* a ^* b ^* conversion circuit, 104 ... Reference H memory, 105 ... Hue difference calculation circuit, 201 ... Color camera, 210 ... Color difference calculation circuit .

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Noboru Yamazaki 14-5 Shimokitada-cho, Neyagawa-shi, Osaka Kurashiki Spinning Co., Ltd.

Claims (2)

[Claims] 1. A video signal picked up by a color image pickup device,
From the color component conversion means for converting to the color component, the reference color registration means for registering the color component of the reference color, the color component of each pixel converted by the color component conversion means and the color component of the reference color registered in advance, Color image conversion comprising: a color difference calculating means for obtaining a color difference between the color of each pixel and a reference color; and an image output means for outputting a monochromatic image signal having a signal level corresponding to the obtained color difference value. apparatus. 2. A video signal picked up by a color image pickup device,
Hue conversion means for converting the hue, reference color registration means for registering the hue of the reference color, hue of each pixel converted by the hue conversion means and the hue of the reference color previously registered, and the color of each pixel and the reference A color image conversion device comprising: a hue difference calculation means for obtaining a hue difference from a color; and an image output means for outputting a monochromatic image signal having a signal level corresponding to the obtained hue difference value.