JPH036985A - Method and apparatus for correcting light source fluctuation - Google Patents

Abstract

PURPOSE:To correct light source fluctuation without needing blank for correction or the like for an object by dividing a light from a light source into a lighting light and a corrected light and correcting the picture while the picture due to the correction light is used as reference when a reference reflection body is provided to the object. CONSTITUTION:A reflected light radiating from a light source 1 to an object is made incident in a part of an image sensor 11 to output an object picture and a light split from the said light source radiates to other part to output a correction picture. Then the picture caused by the light made incident in part of the image sensor when the reference reflection body is provided to the object is used as a reference object picture. Then the picture caused by the light split from the light source at that time is used as a reference correction picture and the object picture is corrected based on the reference correction picture and the correction picture. Since the reflected light of the object and the correction light caused by splitting the same light source are made incident in one and same image sensor to obtain an object picture and the correction picture, the correction picture with high accuracy is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a light source variation correction method and apparatus for correcting image variations due to light source variations, and in particular to color image reading that is sensitive to light source variations; The present invention relates to a method and apparatus for correcting light source fluctuations when performing color measurement or inspection.

[Prior art] An image of the same pattern being printed at a certain period on the surface of a strip-shaped object (for example, a printed matter) moving at a certain speed is captured and displayed as a still image on a display to inspect the finished state of the print. In such cases, a blank area where no pattern is included is provided on the surface of the strip-shaped object, and data from the blank area of the image captured from the line sensor camera into the image memory is used to correct for fluctuations in the light source.

However, stains on the margins result in correction errors, and in recent years, the margin area of band-shaped objects has been decreasing for the purpose of saving resources and reducing costs, so there has been a desire to develop a method that does not use margins.

In addition, a photoelectric element separate from the line sensor for reading patterns is built into the light source device, and a portion of the light from the light source is directed onto the photoelectric element to correct the brightness of the light source, and when reading color images, the photoelectric element is The color-separated output was led to a signal processing circuit and used as a correction signal. However, in order to extract color information more accurately than color images, another correction function was required to correct the discrepancy between the spectral sensitivity of the photoelectric element and the spectral sensitivity of the color line sensor.

(Problem to be solved by the invention) In the case of color images, variations in the reflectance of the object due to variations in the wavelength of the light source greatly affect the image.For this reason, a light source with little variation is used, and if there is further variation, the variation is It is necessary to correct the image accordingly. Conventionally, a margin was provided on the object to perform this correction, but the situation has become such that it is no longer possible to provide such a margin. Therefore, the present invention aims to correct the image. An object of the present invention is to provide a method and apparatus for correcting an image due to light source fluctuations by inputting correction illumination divided from a light source into a part of an image sensor without using a light source.

[Means for solving the problem] In order to achieve the above object, the light from the light source is divided into illumination light for the object and correction light, and the light reflected from the object by the illumination light is incident on a part of the image sensor. Then, the correction light may be incident on the other part, and the image generated by the correction light when a reference reflector is provided on the object may be used as the reference correction image and the reference for image correction. The correction method is to output reflected light emitted from a light source onto a target object to a part of the image sensor to output an image of the target object, and to output a corrected image by irradiating another part with divided light from the light source. , an image generated by entering the part of the image sensor when a reference reflector is provided on the object is used as a reference object image, and light split from the light source at that time is incident on the other part; The method is characterized in that the generated image is used as a reference corrected image, and the object image is corrected based on the reference corrected image and the corrected image, and output as a 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 defined as a second reference object image, and the reference object image and the second reference object The correction target image may be normalized based on the difference with the image. Further, the object may be a strip-shaped object that moves at a predetermined speed and exhibits the same features at a certain period on its surface. In this case, the image sensor may be a one-dimensional image sensor. A device for realizing the light source fluctuation correction method includes a light source device that divides and emits light from a light source into illumination light that illuminates an object and correction light that detects fluctuations in the light source; an optical system that forms an image of the image, an image sensor that receives the image formed by the optical system in one part and receives the correction light in another part and outputs it as an object image and a corrected image, respectively, and the output of the image sensor. is input and an image signal is output, and the image generated by entering the part of the image sensor when the base-semi-reflector is provided on the target object is used as a reference image, and the correction light from the light source at that time is used as the other image. Based on the reference corrected image and the corrected image, an image generated by incidence on a part of the reference corrected image is set as a reference corrected image,
The present invention is characterized by comprising an image processing device that corrects the object image and outputs it as a correction target image signal, and an image display device that displays the image signal of the image processing device.

[Function] With the above configuration, a reference object image generated when a reference reflector is provided on the object, a reference correction image generated by correction light split from the light source at that time, and a target object image of the object. Using the corrected image at that time, the object image is corrected based on the ratio between the reference corrected image and the corrected image. In this way, the object image is corrected for variations in the light source using the light source when the reference reflector is provided on the object as a reference. In addition, a reference object image formed by a reference reflector (e.g., a perfect diffuse reflection surface) is used as one reference, and a second reference object image formed by a second reference reflector (e.g., a horse body) is used as the other reference, and the difference between the two is calculated. The corrected object image can be normalized based on the corrected object image.

The same features (
For example, an image of a strip-shaped object representing a printed pattern),
Since it is obtained in a state in which fluctuations in the light source have been corrected, it is possible to accurately detect changes in the characteristic object itself. In this case, a one-dimensional image sensor may be used since the feature appears at a constant period.

In addition, in the present invention, since the reflected light of the object and the correction light generated by dividing the same light source are incident on the same image sensor to obtain the object image and the correction image, there is no variation in the characteristics of both images, and the accuracy is A well-corrected image can be obtained.

〔Example〕

An embodiment of the present invention will be described using FIGS. 1 to 3.

FIG. 1 is a block diagram showing the configuration of this embodiment. 1st
In the figure, 1 is a light source, for example, a xenon lamp is used. 2. is a spherical reflecting mirror; 3 is a semi-transparent mirror made of quartz glass that takes heat resistance into consideration; 4 is a semi-transparent mirror made of quartz glass for dividing the path of illumination light from light source 2 into two; 4 is illumination light from light a] that illuminates the object The end of the light guide on the light source 1 side is provided at a position where the light flux of the light source 1 is focused by the spherical reflecting mirror 2, and the other end irradiates the object with illumination light. 5 is a correction light guide that guides the light divided by the semi-transparent mirror 3;
Reference numeral 6 denotes a belt-shaped object that moves at high speed as an object and has a pattern drawn at a constant period on its surface; 7 is a roller that guides the belt-shaped object 6; 8 is a pulse oscillator that detects the speed of the roller 7; and 9 is for illumination. An optical lens forms an image of the light reflected from the pattern of the strip-shaped object 6 illuminated by the light guide 4; 10 is a glass filter for spectral sensitivity correction; 11 is a single-plate color line sensor; 12 is the output of the color line sensor 11; A video amplifier for amplification; 13 an A/D converter for converting the analog output of the video amplifier 12 into a digital value; 14 an A/D converter;
an image memory 15 for inputting and storing the output of the converter 13;
16 is a CRT display that directly displays the output of the D/A converter; 17 is a keyboard; 18 is a printer;
is an image processing circuit that counts pulses generated by the pulse generator 8 and outputs a write address signal synchronized with the pattern repetition period to the image memo 4, and also performs image processing.

Next, the operation will be explained.

A strip-shaped object 6 moving at high speed on a roll is illuminated with elongated strip-shaped illumination from an illumination light guide 4 in a direction perpendicular to the moving direction of the strip-shaped object 6. The reflected light from the strip-shaped object 6 passes through an optical lens 9 for focusing placed above the roll 7 and a glass filter 10 for spectral sensitivity correction to form an image on a part of the color licensor 11 in a correction light guide 5. The light from the glass filter 10 for spectral sensitivity correction
The light enters another part of the color line sensor II through the light. At this time, the position where the reflected light from the illumination light guide 4 described above forms an image on the color line sensor 11 and the position where the light from the correction light guide 5 enters are arranged separately. The video amplifier 12 of the color line sensor 11 amplifies it to a required voltage range, and the A/D converter 13 converts it into a digital signal.

A pulse generator 8 is attached to the shaft of a roll 7 used for guiding the belt-shaped object 6. An image processing circuit 19 is used to count the pulses generated in accordance with the rotation of the roll 7, thereby creating a pattern on the surface of the belt-shaped object 6. The video at this time generates a write address signal for the image memory that is synchronized with the repeating cycle of the pattern, and writes the A/D-converted pattern signal and the signal from the correction light guide 5 to the image memo January 4. The signal waveform is shown in Figure 2. The video signal is red (R) and green (G).
), blue (B), HA, H, in Figure 2.

H, indicates the position shown in FIG. 3(a).

The picture signal written in the image memory 14 is read out in accordance with the display timing of the CRT display 16, and the D
/A conversion and displayed on the CRT display 16 as a still image.

As a means of calibrating an apparatus for measuring color, a white strip-shaped object 6 is moved on a roll, or a sample piece corresponding to a perfectly diffuse reflective surface, such as a magnesium oxide or barium sulfate surface, is used instead of the white strip-shaped object 6. Placed in the field of view of the color line sensor 11, and using pulses generated by a frequency oscillator instead of pulses generated by the pulse generator 8, a white image and a correction signal from the correction light guide 5 at this time are captured into the image memory. .

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

The image of the white sample piece is taken into the image memory 14 and the vertical address V of the memory and the horizontal pixels H, -H,
, H construction, the data of the intersection position is stored in the data area (E(P,
A ) ) llam , (E(P,B))□5(E(
P, C)) □* --- (E(P, W) ). I, (
E(P,X)), ,I.

On the other hand, as a black level calibration means, by moving a black strip-shaped object 6 on a roll, or by shielding the color line sensor 11 instead of the black strip-shaped object 6, and instead of the pulse generated by the pulse generator 8, A black image is taken into the image memory 14 using pulses generated by a frequency oscillator. Data at the intersection of the vertical address V of the image memory 14 and the horizontal pixels H4 to Ht=, Hx is stored in the data area CG (P ,A) )□,, (G(
P, B) ) □w, (G (P, C) ) llG
Store in g---(G(P,W))□. Image memo IJ14 of the pattern drawn on the surface of the moving strip-shaped object 6
From the still image displayed on the CRT display 16, a plurality of points from which image data is to be extracted are specified using the keyboard. The state of the image memo January 4 at this time is shown in FIG. 3(b).

P,,P,,P,indicate the points specified for extracting image data.The coordinates of the specified points P,,P,,P3 are each 4.
(vt l Hd), (”+z Hl), (Vz
H,).

Further, the correction signal from the correction light guide 5 corresponding to the specified point from which image data is extracted can be read from the position on the image memory indicated by the point Q, ,Q, ,Q, P + ,
Pz, P! , (The contents of the image memory 14 at each point L, Qz, Qz are stored in the data area (F(1, d)) true,
m, CF(n, g)) llG1. CF(r,
i)) IGl, (F (+, x)) ism(F
(n, x)) mGt, (F(r, X))
The pattern data stored in the data area is corrected using the correction data stored in the IGI, and the corrected data is stored in the data area [D (1, d)) vG.
,, (D (n.

g)) IGg, CD(r, i)] Store in RGI.

(F(+,x)). .

X (F (1, d)) *r, m X (F(n, g)) IGm X (F(r, i)). .

Color data normalized using white data for calibration and black data on designated points from which image data is extracted is obtained as follows.

(B (+, d) ) □, = CD (1, d) ) +1. z (G(p,d)
) RGI(E(p,d) )□*(C(p,d
) ) *r, *(B(n,g) ) IGl = CD(n,g) ) llam CG(p,g)
) man(E(p, g) )□* CG(p, g
))□.

(B(r,i))□1 = (D(r,i)) maw CG(p,i)
) IGm(E(p,i)) ass (G
(p, i)) The effects of aGs books are described below.

■ By using the same detection element for color measurement and light source correction, and by aligning the spectral characteristics from the light source to the detection element, causes such as changes in the power in voltage of the light source, changes in temperature, and lamp deterioration can be eliminated. This improves the accuracy of color data by suppressing the effects of fluctuations in the spectral energy of illumination light caused by

■ The pattern of the moving strip-shaped object and the image for light source correction are captured in the image memory every time the line sensor scans.
When extracting the color data of the color measurement points specified on the pattern, the correction data is extracted from the light source correction image corresponding to each color measurement point on a one-to-one basis, so the reliability is high.
This is effective in cases where it takes time to capture a still image if the speed of the moving object is slow, and variations in the light source may occur while capturing images one by one in the scanning line direction. .

■ Images for pattern and light source correction imported into the image memory, white data for calibration measured for each pixel of the line sensor,
The black data and the light source correction data can be temporarily stored in an external storage device, and then read out again to extract color data at an arbitrary position specified on the picture. With this, it is possible to memorize a pattern to be used as a reference, and to set an arbitrary position of the pattern as a comparison target when it is desired to compare the color deviation with a newly read image.

〔Effect of the invention〕

According to the present invention, the light from the light source is divided into the illumination light of the object and the correction light, and the light reflected from the object by the illumination light is incident on one part of the image sensor, and the correction light is incident on the other part. Since the image is corrected using the image obtained by the correction light when the reference reflector is provided on the object as a reference, it is possible to correct light source fluctuations without requiring a margin for correction on the object.

[Brief explanation of drawings]

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

Claims (5)

[Claims] (1) Reflected light irradiated onto the object from a light source enters a part of the image sensor to output an object image, and the other part is irradiated with divided light from the light source to output a corrected image, When the reference reflector is provided on the object, the image generated by entering the part of the image sensor is taken as a reference object image, and the light split from the light source at that time is generated by entering the other part. A light source fluctuation correction method characterized in that the object image is corrected based on the reference corrected image and the corrected image, using the corrected image as a reference corrected image, and outputted as a correction target image. (2) When the object is provided with a second reference reflector, an image generated by being incident on the part of the image sensor is defined as a second reference object image, and the reference object image and the second reference object are 2. The light source fluctuation correction method according to claim 1, wherein the correction target image is normalized based on a difference from an object image. (3) The light source fluctuation correction method according to claim 1 or 2, wherein the object is a band-shaped object that moves at a predetermined speed and has the same feature on its surface at a certain period. (4) The light source fluctuation correction method according to claim 3, wherein the image sensor is a one-dimensional image sensor. (5) a light source device that divides and emits light from a light source into illumination light that irradiates an object and correction light that detects fluctuations in the light source; and an optical system that forms an image of reflected light from the object; An image sensor that receives the image formed by the optical system in one part and receives the correction light in another part and outputs the image as an object image and a correction image, respectively, and inputs the output of the image sensor and outputs an image signal. At the same time, when a reference reflector is provided on the object, the image generated by being incident on the part of the image sensor is set as a reference image, and the correction light from the light source at that time is made to be incident on the other part, and the image is generated. an image processing device that uses an image as a reference corrected image to correct the object image based on the reference corrected image and the corrected image and outputs it as a correction target image signal; and an image processing device that displays the image signal of the image processing device. A light source fluctuation correction device comprising: an image display device.