GB792051A - Improvements in or relating to circuit arrangements for automatically terminating x-ray exposures - Google Patents
Improvements in or relating to circuit arrangements for automatically terminating x-ray exposuresInfo
- Publication number
- GB792051A GB792051A GB17220/54A GB1722054A GB792051A GB 792051 A GB792051 A GB 792051A GB 17220/54 A GB17220/54 A GB 17220/54A GB 1722054 A GB1722054 A GB 1722054A GB 792051 A GB792051 A GB 792051A
- Authority
- GB
- United Kingdom
- Prior art keywords
- exposure
- cells
- circuit
- capacitors
- film
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05G—X-RAY TECHNIQUE
- H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
- H05G1/08—Electrical details
- H05G1/26—Measuring, controlling or protecting
- H05G1/30—Controlling
- H05G1/38—Exposure time
- H05G1/42—Exposure time using arrangements for switching when a predetermined dose of radiation has been applied, e.g. in which the switching instant is determined by measuring the electrical energy supplied to the tube
- H05G1/44—Exposure time using arrangements for switching when a predetermined dose of radiation has been applied, e.g. in which the switching instant is determined by measuring the electrical energy supplied to the tube in which the switching instant is determined by measuring the amount of radiation directly
Landscapes
- Health & Medical Sciences (AREA)
- General Health & Medical Sciences (AREA)
- Toxicology (AREA)
- X-Ray Techniques (AREA)
Abstract
792,051. Photo-electric control of X-ray exposure times. PHILIPS ELECTRICAL INDUSTRIES, Ltd. June 11, 1954 [June 16, 1953], No. 17220/54. Addition to 751,786. Class 40 (3). In a circuit arrangement for automatically terminating an X-ray exposure a radiationsensitive indicator disposed behind the subject comprises a number of radiation cells individually responsive to radiation passing through different parts of the subject. The output current of each cell alters the charge on a capacitor connected in the grid circuit of a corresponding discharge tube and the summated anode currents of the discharge tubes operates to cut off the X-rays when it attains a preset value. The invention resides in so arranging the circuit that when the intensity of X-rays on any of the cells exceeds a predetermined average value the corresponding discharge tube is driven to cut off or saturation before the summated currents attain the preset value. X-rays from tube 3 supplied by the mains 20, fall on film 5 after passage through the subject 4 under examination and then produce a light pattern on fluorescent screen 2 corresponding to the local variations of X-ray intensity on the film. The photo-cells 1 are each responsive to light from different parts of the fluorescent screen 2. Immediately prior to an exposure the normally closed switch 16 is opened to charge capacitors 7 to the voltage of battery 10. When the exposure is started the switch is closed but the triodes are cut off by the high negative bias. The resistances of photo-cells 1 are reduced by the fluorescence from the screen in response to X-rays incident on the film 5, thereby allowing current to flow from battery 6 to reduce the charge on associated capacitors 7. The anode current in the triodes 8 rises until when the summated currents exceed a predetermined level relay 13 operates to open the energizing circuit of the X-ray tube. If the intensity of illumination of the film is markedly uneven certain of the capacitors become discharged well before the others but the effect of this high local illumination in the exposure time is reduced by the fact that grid current limits the current in the associated valve so that it is the illumination of the least illuminated parts of the film which ultimately determines the exposure time. In an alternative arrangement the capacitors are uncharged at the start of an exposure and a relay corresponding to 13 is energized to close the supply circuit. On exposure the capacitors are charged to drive the grids negative so that when the total current falls to a preset level the relay releases to open-circuit the X-ray tube supply. In this case the effect of excessive illumination of individual cells is reduced by their being driven to cut-off. The fluorescent screen may be dispersed and cells giving a response to X-rays used instead of the photo -cells.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NL179143A NL100600C (en) | 1953-06-16 | 1953-06-16 | Device for producing X-ray images, in which an indicator for measuring the X-ray intensity is arranged behind the object to be photographed |
GB6235/54A GB751786A (en) | 1953-03-03 | 1954-03-03 | Improvements in or relating to devices for automatically determining the optimum exposure time in radiography |
Publications (1)
Publication Number | Publication Date |
---|---|
GB792051A true GB792051A (en) | 1958-03-19 |
Family
ID=19834436
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB17220/54A Expired GB792051A (en) | 1953-06-16 | 1954-06-11 | Improvements in or relating to circuit arrangements for automatically terminating x-ray exposures |
Country Status (1)
Country | Link |
---|---|
GB (1) | GB792051A (en) |
-
1954
- 1954-06-11 GB GB17220/54A patent/GB792051A/en not_active Expired
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