The principle and conditions of discriminating high temperature forgings in multicolor ccd image

Research of Materials Science December 2014, Volume 3, Issue 4, PP.92-95

The Principle and Conditions of Discriminating High Temperature Forgings in Multicolor CCD Image Zhonghui Yin#1,2, Chun Li 2 1. School of Mechanical Engineering, Anhui University of Science and Technology, Huainan Anhui 232001, China 2. School of Energy & Power Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China #

Email: zhhyin@aust.edu.cn

Abstract In order to realize boundary identification and provide basic for size measurement of the high temperature forging by multicolor CCD, the paper analyses the monochrome irradiation response characteristic of the high temperature forging and its surrounding scenery and the irradiation response characteristic of the multicolor CCD. The result is obtained that the intersection point critical wavelength exists in the monochrome irradiation response characteristic curves of multicolor CCD to the forging and the surrounding. When wavelength is more than the critical wavelength, monochrome irradiation response of high temperature forging will be greater than that of the surrounding scenery, and the pixel gray of high temperature forging is greater than that of the surrounding scenery. It is put forward that the principle of discriminating the high temperature forging from its surrounding scenery by using the pixel gray difference in the wavelength of more than the critical wavelength. It is presented that the condition of discriminating high temperature forgings in multicolor CCD image is the pixel gray of the high temperature forging is greater than that of all the sceneries. In order to discriminating high temperature forgings in multicolor CCD image, critical wavelength must locate in the photosensitive area of the multicolor CCD. The smaller the critical wavelength is the better the discriminating effectiveness is.

Keywords: High Temperature Forging; Multicolor CCD; Critical Wavelength; Irradiation Response; Gray Difference; Discrimination

1 Introduction Size measurement of large size high temperature forging is the important technical guarantee to its high quality and production qualification ratio. But online rapid discrimination and size measurement of the large size high temperature forging are very difficult for the abominable forging environment. Its online size measurement is still the technical challenges, although the oversize ingot of 438 million tons can be forged with the 1.85 million tons oil forging press in CITIC HEAVY INDUSTRIES CO.LTD. The forging materials waste caused by low (lack of high) precision size measure is very serious. For example, the utilization ratio of forging materials is only 50 percent to 55 percent in China, 60 percent to 65 percent in Korea and 70 percent to 75 percent in Japan [1]. Therefore, many famous domestic research institutes and experts have made mass research on the size measurement of high temperature forgings[2-7].The measurement based on monochrome CCD, one of the researched methods of size measurement of large size hot forgings, has become the main research target for its advantages of remote control, rapid response, high-precision, low price and no special requirement for the environment. Because the high precision monochrome CCD and its image processing software are very hard to obtain, the monochrome CCD measurement system is difficult to apply in engineering applications. The paper puts forward the principle and conditions of discriminating the boundary of the high temperature forging during the forging process based on multicolor CCD technology for the high precision multicolor CCD and its image processing software are easy to get and provides the basic to realizes the size measurement of the high temperature forging on-line.

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2 The Principle of Discriminating High Temperature Forgings in Multicolor CCD Image In order to discriminate the high temperature forging from its surrounding scenery, the difference between the forging and its surrounding scenery should exist in the image. According to the radiation characteristic, the main photosensitive imaging factors of high temperature forging and its surrounding scenery are their self-radiation and reflection radiation of lighting luminous. The high temperature forging can be regarded as blackbody because its temperature is high enough. The radiation of the high temperature forging is mainly self-radiation spectrum for its self-radiation is very strong and its reflection radiation is weak. The monochrome irradiation response of multicolor CCD to the high temperature forging can be calculated as following Eq.1.

C2

for for for M ccd ccd ( )  dccd  C1 5 (e ,   f ccd ( )  E

T for

 1)1

(1)

for ccd , 

In the Eq.1 M is monochrome irradiation response of multicolor CCD to the high temperature forging, fccd ( ) is the characteristics response coefficient of multicolor CCD[8], Efor is monochrome radiant irradiance to for color CCD of high temperature forging, d ccd is attenuation coefficient of the high temperature forging radiate to CCD, C1 is the first Planck constant, C2 is the second Planck constant, T for is temperature of the forging.

The self-radiation of the surrounding scenery is very weaker for their lower temperature and their radiation is mainly reflection radiation of the background light and the radiation of the high temperature forging. The monochrome irradiation response of multicolor CCD to the scenery can be calculated as following Eq.2.

C2

M

sce ccd , 

 f ccd ( )  E  f ccd ( )  D sce

lig sce , ccd

 C1 (e 5

Tlig

 1)1

C2

for 5  f ccd ( )  Dsce , ccd  C1 (e

T for

(2)

 1) 1

sce sce In the Eq.2 M ccd is ,  is monochrome irradiation response of multicolor CCD to surrounding scenery, E lig monochrome radiant irradiance to color CCD of scenery, d sce,ccd is attenuation coefficient of the background light for reflected by scenery to CCD, d sce , ccd is attenuation coefficient of the high temperature forging reflected by scenery to CCD, Tlig is temperature of the background light.

The monochrome irradiation response characteristic curves of multicolor CCD to the high temperature forging and the surrounding are showed as Fig. 1.

FIG. 1 THE MONOCHROME IRRADIATION RESPONSE CHARACTERISTIC CURVES OF MULTICOLOR CCD TO THE HIGH TEMPERATURE FORGING AND THE SCENERY

From Fig.1 we can see that the monochrome irradiation response characteristic curves of high temperature forging intersect with the curves of the surrounding. Let the intersection point be critical wavelength ci [9]. When wavelength   ci , monochrome irradiation response of high temperature forging less than that of the surrounding, - 93 http://www.ivypub.org/rms

the pixel gray of high temperature forging less than that of the surrounding in the CCD image; when wavelength   ci , monochrome irradiation response of high temperature forging equal with that of the surrounding, which means high temperature forging and the scenery has the same the pixel gray; when wavelength   ci , monochrome irradiation response of high temperature forging will be more than that of the surrounding, the pixel gray of high temperature forging more than that of the scenery. So we can discriminate the high temperature forging from its scenery by using the pixel gray difference between the hot forging and its surrounding scenery within   ci .

3 The Conditions of Discriminating High Temperature Forgings in Multicolor CCD Image According to the relationship between gray value and irradiation response[10], the gray of the high temperature forging can be calculated as following Eq.3. for for M ccd = f ccd ( )  Eccd 

  f ccd (  )  d 0

(3)

C2

for ccd

 C1 (e 5

T for

 1) 1 d 

for ccd

for In the Eq.3 M is irradiation response of multicolor CCD to high temperature forging, Eccd is irradiance to color CCD of high temperature forging.

The gray of the surrounding scenery can be calculated as following Eq.4. sce sce M ccd  f ccd ( )  Eccd



lig 5   f ccd ( )  Dsce , ccd  C1 (e

C2

Tlig

0



for 5  1)1 d    f ccd ( )  Dsce , ccd  C1 (e

C2

T for

0

 1) 1 d 

(4)

sce sce In the Eq.4 M ccd is irradiation response of multicolor CCD to surrounding scenery, Eccd is irradiance to color CCD scenery.

The gray difference between the high temperature forging and the surrounding scenery can be calculated as following Eq.5. for sce for sce   M ccd  M ccd  f ccd ( )  ( Eccd  Eccd ) 

for  f ccd (  )  [  d ccd  C1 5 (e

C2

T for

0



  f ccd ( )  D 0



lig 5  1)1 d    f ccd ( )  Dsce , ccd  C1 (e

C2

Tlig

0

 1)1 d 

(5)

C2

for sce , ccd

 C1 (e 5

T for

 1)1 d  ]

In the Eq.5  is the pixel gray difference between the high temperature forging and the scenery.

Assuming that there are n sceneries around a high temperature forging in multicolor CCD image, the pixel gray difference between the high temperature forging and the scenery i is calculated as following Eq.6. for sce ,i for sce ,i i  M ccd  M ccd  fccd ( )  ( Eccd  Eccd )0

(6) (i  1, 2n) sce ,i In the Eq.6  i is the pixel gray difference between the high temperature forging and the scenery i, M ccd is sce ,i irradiation response of multicolor CCD to the scenery i, Eccd is irradiance to multicolor CCD of the scenery i. that is for sce ,i for sce,i i  M ccd  M ccd  fccd ( )  ( Eccd  Eccd )0

(i  1, 2n)

Or

for sce ,i for sce ,i i  M ccd  M ccd  fccd（ )  ( Eccd  Eccd )0

(7)

(8) (i  1, 2n) Because the whole forging temperature is uniformity, its pixel gray is basically the same. But the pixel gray of the sceneries around are different for their different material, surface conditions and position. The dark surrounding - 94 http://www.ivypub.org/rms

scenery probably exits around the forging. It is difficult to satisfy Eq.8 for brightness of the high temperature forging need to be weaker than that of the darkest scenery. In order to let every pixel gray difference between the high temperature forging and each scenery exist, the condition as following Eq.7 must be satisfied. That means the pixel gray of the high temperature forging should be greater than that of the brightest scenery. The Eq.7 is the conditions of discriminating high temperature forgings in multicolor CCD image.

In order to discriminating high temperature forgings in multicolor CCD image, critical wavelength ci must locate in the photosensitive area of the multicolor CCD from Fig.1. The smaller the ci is the better the discriminating effectiveness is. It provides theoretical direction for realizing the conditions of discriminating high temperature forgings in multicolor CCD image.

4 Conclusion According to spectral response characterization of the high temperature forging and its peripheral sceneries, following conclusions can be obtained through research on principle and conditions of discriminating the high temperature forging in the multicolor CCD image.

1) The intersection point ci exists in the monochrome irradiation response characteristic curves of multicolor CCD to the high temperature forging and the surrounding. When wavelength   ci , monochrome irradiation response of high temperature forging less than that of the surrounding, the pixel gray of high temperature forging less than that of the surrounding scenery in the CCD image; when wavelength   ci , monochrome irradiation response of high temperature forging equal with that of the surrounding, which means high temperature forging and the scenery has the same the pixel gray; when wavelength   ci , monochrome irradiation response of high temperature forging will be more than that of the surrounding, the pixel gray of high temperature forging more than that of the scenery.

So we can discriminate the high temperature forging from its scenery by using the pixel gray difference between the forging and its scenery within   ci .

2) The condition of discriminating high temperature forgings in multicolor CCD image is the pixel gray of the high for sce,i for sce,i temperature forging is greater than that of all the sceneries. That is i  M ccd  M ccd  fccd ( )  ( Eccd  Eccd )0

(i  1, 2n) .

3) In order to discriminating high temperature forgings in multicolor CCD image, critical wavelength ci must locate in the photosensitive area of the multicolor CCD from Fig.1. The smaller the ci is the better the discriminating effectiveness is. It provides theoretical direction for realizing the conditions of discriminating high temperature forgings in multicolor CCD image.

Acknowledgements Subsidized project on Key Discipline Construction by Shanghai City (J50501).

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