| 摘要 |
PURPOSE:To obtain a constant film darkening degree corresponding to the thickness of a subject by adjusting the photographing mAs according to the subject thickness signal obtained by an automatic perspective brightness adjuster, in an automatic exposure control type X-ray generator in which the exposure conditions on X-ray photographing are properly controlled. CONSTITUTION:The voltage V2 increases rectilinearly relative to the thickness of a subject and is supplied with the bias of a comparator 26 which is proper for obtaining mAs through adjustment setting. As the bulb current is constant, the photographing time (s) is contrilled actually. Electric charging from a power source 19 to the integrator consisting of a resistor 21, condenser 24, amplifier 25 etc. is started simultaneously with start of X-ray radiation. The output voltage V1 of the integrator increase with the lapse of time, and when t sec. lapses after start of radiation, the relation V1<V2 is satisfied. At this time point, the comparator 26 is reversed, an excitation coil 27 is energized, a contact 17 is opened, excitation of an excitation coil 15 is deenergized, and X-ray radiation is suspended. This time t gives the mAs value for providing a proper film darkening degree corresponding of the thickness of a subject together with the constant bulb current mA. |
