Electronic camera

Optical photomicrographs were taken on an Jena photomicroscope equipped with a B100 M electronic camera (Jena, Germany supplied by Acts Instruments, Peagram, TN). Illumination was provided by a Cuda Products 1-150 illuminator (Acts Instruments). The images were recorded at a shutter speed of 1/125 s on Kodak 400 ASA film. The magnification was 100X. 

J. P. Vigier, and M. Duchesne, Sur la reciprocity de la reponse de la camera electronique aux tres faibles flux de lumiere coherente [On the reciprocity of the response of the electron camera to weak coherent light flux (SbCs3 layer properties)], C. R. Acad. Sci. Paris 273B, 911 (1971). 

Fig. 3. Lyman a bridhtness isophotes of Comet Kohoutek 1973 XII, intensities in Kilo-Rayleigh, derived from photographs taken with an electronic camera by Carruthers et al. (see Keller )...

E. Fossum. CMOS image sensors electronic camera-on-a-chip. IEEE Trans. On Electronic Devices, Oct. 1997, pp. 1689 - 1698. 

Color or opacity by automatic optical scanners with CCD electronic cameras for reflected light (viz. ColorMaster and ScanMaster). The devices are used for separating green from namral PET bottles, or opaque (blended) PE bottles from transparent. 

To get further independent information about the oscillations of the building an additional accelerometer was installed on the abutment as a sensor on the object. The double integrated accelerations of the abutment, produced by the retarding train, over the time, also represent the oscillations and movements of the abutment. Finally an interpretation in a joint model will be shown, which combines the heterogeneous data of the electronic camera and the accelerometer. 

In the equations (1) Dy,Dg means the distance between opposite electrodes, I to I4 means the intensity of the currents on the electrodes and Ky,Kx means calibration functions for the whole electronic camera system, which include distortions of the sensor and the used lens and other distortions. 

USING THE ELECTRONIC CAMERA TO MEASURE OSCILLATIONS OF AN ABUTMENT OF A BRIDGE... 

With classical geodetic measurement methods it is not possible to observe the abutment during the brake tests on the described boundary conditions. Therefore we used the electronic camera as basic instrument on an external station to observe the abutment motion on a selected bridge (Fig. 4). 

For the calibration of the electronic camera in the field on the job, the diode was mounted on a cross slide which was attached to the abutment. So it was possible to move the diode on defined values before and after the brake tests to determine the calibration functions Ky and Kx of (1) (Fig. 5). As computer unit to register the signals from the electronic camera we have used an HP 200/300. With this system we obtained a measurement frequency of 40Hz. So we were within the boundary conditions. 

Figure 5 Cross slide to calibration the electronic camera...

On the selected test bridge the Deutsche Bundesbahn has executed about 60 brake tests on 3 days. The period of each braking was about 30 seconds, during which the brake power was always the same. Our institute has observed the abutment, which was the reference for the measurements of the Deutsche Bundesbahn, with the electronic camera during each test. 

Figure 6 Original measurements of the electronic camera include the theoretical braking deceleration curve...

If we copy the time scale of the theoretical braking deceleration curve onto the figure which shows the measured abutment movements, we can also see, that the character of the movements is identical to the theoretical curve. Model and reality are corresponding. The maximum amplitude of the movement is about 0.5 mm during stopping the train. The accuracy is represented by the noise of the measurements and has a value of 0.1mm. This is the result if we use only an electronic camera as measuring instrument. All other brake tests show much the same results. So our example is representative for the selected test bridge. 

Nevertheless the measured accelerations during a brake test show, that we can get information of movements of the abutment in addition to the measurements of the electronic camera (Fig. 8). More distinctly than in the measurements of the electronic camera we can see the train driving onto the bridge, the start point of the braking and the oscillation of the abutment during the stopping of the train. We will use this information from the accelerometer to interpret the geometrical measurements of the electronic camera. 

INTERPRETATION OF THE MEASUREMENTS WITH ELECTRONIC CAMERA AND ACCELEROMETER IN A JOINT MODEL... 

Figures 6 and 8 show the pure, but calibrated measurements of the electronic camera and the accelerometer on the abutment. This data is superimposed by a noise. The noisebandwidth before the beginning of the braking is representing the variance of the observations. The problem which we have to solve is to determine the movements of the abutment in the direction of the brakepower, which is the direction of the bridge axis, by using the observations of the electronic camera and of the accelerometer. To achieve this we have to treat both data in a joint model with the performance function S t).

A different way to manipulate the heterogeneous data of the electronic camera and of the accelerometer in a joint model is possible, if we consider the horizontal movements of the abutment as a dynamic process. Then we can estimate the state of the system for each moment within the measuring time from all measurements in advance by using a Kalman Filter (Schrick 1977). In addition to the measurements for a Kalman Filter we need a priori knowledge of the dynamic system, start values and characteristic quantities of the system error and measuring error. I will give only a short summary of the nesessary algorithm here, whereby the dynamic system is not forced. 

Observations are the way s t) from the measurements of the electronic camera and the accelerations s t) from measurements of the accelerometer and the observation equations are... 

Bayer, G., Heck, U., Monicke, H.-J. (1990) Automatic Observation of Moving Objects with Electronic Cameras. International Symposium Data Acquisition for the Investigation of Deformations, Page 42-51, Katowice, Poland. 

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