JP2655546B2 - Light source fluctuation correction method and device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source fluctuation correction method and apparatus for correcting an image fluctuation due to a light source fluctuation, and more particularly to a color image reading sensitive to a light source fluctuation. The present invention relates to a method and an apparatus for correcting light source fluctuation when performing color measurement or inspection.

[Conventional technology]

In a case where an image in which the same pattern is printed on a surface of a band-shaped object (a printed matter as an example) moving at a certain speed is printed at a fixed cycle, the image is displayed on a display as a still image, and the completed printing state is inspected. A margin is formed on the surface of the object without a picture, and the fluctuation of the light source is corrected using the margin data of the image taken from the line sensor camera into the image memory.

However, the margin area of the belt-shaped object tends to decrease for the purpose of saving the resources and reducing the cost in recent years, for example, because the stain in the blank portion causes a correction error, and the development of a method using no blank space has been desired.

In addition, a photoelectric element different from the line sensor for reading a picture is incorporated into the light source device, and a part of light from the light source is applied to the photoelectric element to correct the luminance of the light source. The color-separated output was guided to a signal processing circuit and used as a correction signal. However, in order to extract color information more accurately than a color image, another correction function is required to correct the difference between the spectral sensitivity of the photoelectric element and the spectral sensitivity of the color line sensor.

[Problems to be solved by the invention]

In the case of a color image, a change in the reflectance of the object due to a change in the wavelength of the light source greatly affects the image. For this reason, it is necessary to use a light source with little fluctuation, and when the light source fluctuates further, it is necessary to correct the image according to the fluctuation. Conventionally, a blank is provided on the object to perform this correction. However, this situation has not been provided. Accordingly, an object of the present invention is to provide a method and an apparatus for correcting an image due to light source fluctuation by causing a correction light beam divided from a light source to enter a part of an image sensor without using such a margin. I do.

[Means for solving the problem]

In order to achieve the above object, the light from the light source is split into illumination light and correction light for the target object, reflected light of the target object by the irradiation light is incident on one part of the image sensor, and correction light is emitted on the other part. And the image generated by the correction light when the reference reflector is provided on the object may be used as the reference correction image as a reference for image correction, and the light source fluctuation correction method of the present invention uses the light source fluctuation correction method at a predetermined speed from the light source. Moved, reflected light illuminated on the object consisting of a band-like body representing the same feature at a constant cycle on the surface is incident on a part of the image sensor to output an object image, and the other part A corrected image is output by irradiating the divided light from the light source, and an image generated by being incident on the part of the image sensor when the reference reflector is temporarily provided on the object is referred to as a reference object image. The light split from the light source is Is characterized in that outputs the reference corrected image and the corrected image and the object image is also Ki not a preparative image generated shines as a reference corrected image as a correction to the correction target image. Further, an image generated by being incident on the part of the image sensor when a second reference reflector is provided on the object is used as a second reference object image, and the reference object image and the second reference object are used. The correction target image may be normalized based on a difference from the image. The image sensor may be a one-dimensional image sensor. Also,
An apparatus for realizing the light source fluctuation correction method of the present invention includes a light source device that divides light from a light source into proof light for irradiating an object and correction light for detecting fluctuation of the light source, and emits the light. An optical system that forms an image of the reflected light, an image sensor that partially receives the image formed by the optical system, receives the correction light at another part, and outputs the corrected light as an object image and a corrected image, respectively, and the image sensor And outputs an image signal and outputs an image signal, and sets the image generated by being incident on the part of the image sensor when the reference reflector is temporarily provided on the object as the reference image, and corrects the correction light from the light source at that time. An image processing device that corrects the target object image and outputs the corrected target image signal as a correction target image signal, based on the reference correction image and the correction image as an image generated by being incident on another part. Shows the image signal of the image processing apparatus. It is characterized in that an image display device for.

[Action]

With the above configuration, a reference target image generated when the reference reflector is temporarily provided on the target, and a reference correction image generated by the correction light divided from the light source at that time are obtained. Then, using the target image of the target and the corrected image at that time, the target image is corrected by the ratio between the reference corrected image and the corrected image. In this way, the object image is corrected for the light source fluctuation based on the light source when the reference reflector is temporarily provided on the object. Thus, an image of a band moving at a predetermined speed and representing the same feature (for example, a printed pattern) on the surface at a constant cycle can be obtained in a state where the fluctuation of the light source is corrected, and thus the feature itself is obtained. Can be accurately detected. In addition, a reference object image formed by a reference reflector (for example, a fully expanded reflection surface) is used as one reference, and a second reference object image formed by a second reference reflector (for example, a black body) is used as the other reference.
The object image corrected based on the difference between the two can be normalized.

In this case, a one-dimensional image sensor may be used because the feature appears at a constant period.

Further, in the present invention, the reflected light and the correction light of the object generated by dividing the same light source into the same image sensor are incident to obtain an object image and a corrected image. A good corrected image can be obtained.

〔Example〕

One embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a block diagram showing the configuration of the present embodiment. In FIG. 1, reference numeral 1 denotes a light source, for example, a xenon lamp. 2 is a spherical reflecting mirror, 3 is a semi-transparent mirror made of, for example, quartz glass in consideration of heat resistance for dividing the path of the illumination light from the light source 1 into two, and 4 is irradiating the object with the illumination light from the light source 1 An end on the light source 1 side is provided at a position where the light flux of the light source 1 is condensed by the spherical reflector 2, and the other end irradiates the object with illumination light. 5 is a correction light guide for guiding the light split by the translucent mirror 3,
Reference numeral 6 denotes a band-shaped object which moves at high speed as a target and has a pattern drawn on the surface at a constant period, 7 denotes a roller for guiding the band-shaped object 6, 8 denotes a pulse generator for detecting the rotational position of the roller 7, and 9 denotes a pulse generator. An optical lens for forming an image of reflected light of a picture of the band-shaped object 6 illuminated by the illumination light guide 4; 10 a glass filter for correcting spectral sensitivity; 11 a single-plate type color line sensor; A video amplifier that amplifies the output, 13 is an A / D converter that converts the analog output of the video amplifier 12 into a digital value, 14 is an image memory that inputs and stores the output of the A / D converter 13, and 15 is an image memory 14 is a D / A converter that converts the output to analog, 16 is a CRT display that displays the output of the D / A converter as an image, 17 is a keyboard, 18 is a printer, and 19 is a counter that counts the pulses generated by the pulse generator 8. Synchronized with the pattern repetition cycle An image processing circuit that outputs the written address signal to the image memory 14 and performs image processing.

 Next, the operation will be described.

An elongated strip-shaped illumination is applied to the strip-shaped object 6 moving on the roll at a high speed from the illumination light guide 4 in a direction perpendicular to the moving direction of the strip-shaped object 6. The reflected light of the illumination from the band-shaped object 6 forms an image on a part of the color licensing sensor 11 through an optical lens 9 for focusing placed above the roll 7 and a glass filter 10 for correcting spectral sensitivity. The light from the correction light guide 5 is incident on another part of the color line sensor 11 through the glass filter 10 for correcting spectral sensitivity. At this time, the position where the reflected light from the illumination light guide 4 forms an image on the color line sensor 11 and the position where the light from the correction light guide 5 is incident are separated from each other. The signal is amplified to a required voltage range by the video amplifier 12 of the color line sensor 11 and converted into a digital signal by the A / D converter 13.

A pulse generator 8 is mounted on a shaft of a roll 7 used for guiding the band-shaped object 6. The image processing circuit 19 counts the pulses generated in accordance with the rotation of the roll 7 to generate a write address signal of the image memory synchronized with the repetition period of the pattern drawn on the surface of the belt-shaped object 6.
The A / D converted picture signal and the signal of the correction light guide 5 are written in the image memory 14. The waveform of the video signal at this time is shown in FIG. The video signal consists of red (R), green (G), and blue (B). H _A , H _W , and H _{X in} FIG. 2 are those in FIG.
Are shown. The picture signal written in the image memory 14 is read out in accordance with the display timing of the CRT display 16, D / A converted, and displayed on the CRT display 16 as a still image.

By moving the white band-shaped object 6 on a roll as a calibration means of a device for measuring color, or by replacing a white band-shaped object 6 with a sample piece corresponding to a perfect diffuse reflection surface, for example, a magnesium oxide or barium sulfate surface. It is placed in the field of view of the color line sensor 11, and a white image and a correction signal from the correction light guide 5 at this time are taken into an image memory using a pulse generated by a frequency oscillator instead of a pulse generated by the pulse generator 8. .

FIG. 3 shows the state of the image memory 14 at this time.

White vertical address memory transfer images in the image memory 14 by the sample piece V _P and horizontal pixels H _A ~H _W, H _X data the intersection position between the data area [E (P, A)] _RGB ,
[E (P, B)] _RGB , [E (P, C)] _RGB … [E (P, W)]
_RGB , [E (P, X)] Store in _RGB .

On the other hand, by moving the black band object 6 on a roll as black level calibration means, or by shielding the color line sensor 11 in place of the black band object 6, instead of the pulse generated by the pulse generator 8, A black image is stored in the image memory 14 using the pulse generated by the frequency oscillator.
Take in. Pixel H _A to H _W of the vertical address V _P and the horizontal direction of the image memory 14, H _X and data data area [G (P, A)] of the intersection of _RGB [G (P, B)] _RGB [G (P, C)] _RGB …
[G (P, W)] Store in _RGB . The picture drawn on the surface of the moving band-shaped object 6 is taken into the image memory 14. A plurality of points where image data is to be extracted from the still images displayed on the CRT display 16 are designated using a keyboard. The state of the image memory 14 at this time is shown in FIG.

P ₁ , P ₂ and P ₃ indicate points designated for extracting image data. The coordinates of the designated points P ₁ , P ₂ , and P ₃ are ( _VL , _Hd ),
(V _n , H _g ) and (V _r , H _i ).

The correction signal by the correction light guide 5 that corresponds to the specified point to extract image data read from the Q _1, Q _2, the position of the image memory in terms of Q ₃ refers. P ₁ , P ₂ , P ₃ , Q ₁ ,
The contents of the image memory 14 at each point of Q ₂ and Q ₃ are stored in the data area [F
(L, d)] _RGB , [F (n, g)] _RGB , [F (r, i)]
_RGB [F (l, x)] _RGB , [F (n, x)] _RGB , [F (r,
x)] Store in _RGB . The picture data stored in the data area is corrected using the correction data as follows, and the corrected data is stored in the data area [D (l, d)] _RGB [D (n,
g)] _RGB , [D (r, i)] Store in _RGB .

The color data normalized using the calibration white data and black data on the designated point from which the image data is extracted is obtained as follows.

The effects of the present embodiment will be described below.

The detection elements for color measurement and light source correction are the same, and the spectral characteristics from the light source to the detection element are aligned to cause changes in the power supply voltage of the light source, changes in temperature, deterioration of the lamp, etc. The accuracy of color data is improved by suppressing the influence of fluctuations in the spectral energy of illumination light.

When the image of the moving band-shaped object and the image for light source correction are fetched into the image memory for each scan of the line sensor, and when extracting the color data of the specified color measurement point on the image,
Since the correction data is extracted from the light source correction image corresponding to each color measurement point on a one-to-one basis and corrected, the reliability is high. This is because it takes time to capture a still image when the speed of the moving object is slow, and the light source may fluctuate while capturing one image in the scanning line direction. This is effective in such a case. .

The picture and light source correction image taken into the image memory and the calibration white data, black data and light source correction data measured for each line sensor image are temporarily stored in an external storage device, and are read out again. Color data at an arbitrary position designated on the picture can be extracted. Thus, a pattern to be used as a reference can be stored, and an arbitrary position of the pattern can be set as a comparison target when it is desired to compare a color shift with a newly read image.

〔The invention's effect〕

According to the present invention, light from a light source is split into illumination light and correction light for an object, reflection light of the object by the illumination light is incident on a part of the image sensor, and correction light is incident on another part. In this case, the image is corrected based on the image by the correction light when the reference reflector is provided on the object, so that the light source fluctuation can be corrected without requiring a correction margin or the like on the object.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention, FIG. 2 is a diagram showing a waveform of a video signal, and FIG. 3 is a diagram showing a state of an image memory. DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Spherical reflecting mirror 3 ... Semi-transparent mirror 4 ... Lighting guide 5 for illumination 5 ... Light guide for correction 6 ... Strip-shaped object 7 ... Roll 8 ... Pulse generator 9 …… Optical lens, 10… Glass filter 11 …… Color line sensor 12 …… Video amplifier, 13 …… A / D converter 14 …… Image memory, 15 …… D / A converter 16 …… CRT display 17 …… Keyboard, 18… Printer 19 …… Image processing circuit

Claims (4)

(57) [Claims] 1. A light source, which moves at a predetermined speed from a light source and irradiates an object consisting of a band-like body representing the same feature on the surface at a constant period, enters a part of an image sensor to reflect the light. Outputting an image and irradiating the other part with the divided light from the light source to output a corrected image, the light is incident on the part of the image sensor when a reference reflector is temporarily provided on the object, and is generated. The image obtained as the reference target image is an image generated when the light split from the light source at that time is incident on the other part, and the reference correction image, the correction image, and the reference target image are used as the reference correction image. A light source fluctuation correction method, wherein the object image is corrected and output as a corrected object image. 2. An image generated by being incident on the part of the image sensor when a second reference reflector is provided on the object, is generated by a second reference reflector.
2. The light source fluctuation correction method according to claim 1, wherein the correction target image is normalized based on a difference between the reference target image and the second reference target image. . 3. The method according to claim 1, wherein the image sensor is a one-dimensional image sensor. 4. A light source for moving a light from a light source at a predetermined speed and irradiating an object consisting of a band-like body representing the same feature with a constant period on the surface and a correction for detecting a fluctuation of the light source. A light source device that splits and emits light, an optical system that forms an image of the reflected light of the object, and a part that receives the image formed by the optical system and another part that receives the correction light. An image of the target object, an image sensor that outputs as a corrected image, and an input of the output of the image sensor to output an image signal and enter the part of the image sensor when the target object is provided with a reference reflector temporarily. The resulting image is used as a reference target image, and an image generated when the correction light from the light source at that time is incident on the other part is used as the reference correction image, and both the reference correction image, the correction image, and the reference target image are used. Toshiki Corrects the object image and corrects it The image processing apparatus and a light source fluctuation correction device characterized by comprising an image display device for displaying an image signal of the image processing apparatus for outputting as an image signal.