The X-ray tube in focus

The RFM (Real-time FocusMeter) is a tool for determining the X-ray tube focal spot in a quick and easy way. No film is needed and the method is simple to apply. The greatest advantage of using this technique is the speed - in less than one minute a complete examination is carried out which gives you both the size and shape for different generator settings. The result of a measurement is available "at once" and can be examined and displayed on a computer screen and the method makes it possible to measure, for instance, the focal spot width and length for different angles from the radiation beam axis. With this method it is also possible to measure focal spot down to 100 µm.

Methods and Automatic Alignment

The RFM is based on the slit method according to the IEC 336 recommendation. The 10 µm wide slit makes it possible to measure focal spot sizes down to 0.10 mm, according to IEC 60336.

The RFM can be automatically aligned. With a specially designed alignment pattern, and four CCD arrays, the RFM determines its position in the beam. It also calculates the enlargement factor and the distance from the focal spot to the detector.

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Main features

• Fast and accurate
• Automatic alignment
• Focal spot size
• Shape (Line Spread Function)
• Modulation Transfer Function, MTF
• Root Mean Square (RMS) calculations
• Microsoft Access based database for saving data
• Export function for LSF data
• Only one exposure per axis
• High sensitivity
• Mammo focal spot sizes down to 0.1 (IEC 60336)
• No film needed
• Real-time measurements
• Windows software

Specifications general

Supporting standards:	IEC 60336
	DIN 6823
	NEMA XR5
Tube focal spot types:	Radiographic
	CT
	Mammographic
	Dental
Exposure time:	minimum 10 ms
kV range:	22-150 kV
Charge range, tube:	10-100 mAs (at 70 cm)
Enlargement factor:	0.8-5 (automatically calculated)
Measurement range:	0.1-5mm
Resolution:	25/E µm (E=enlargement calculated)
MTF magn. Factor:	1 < M =< 10
Measured values:	focus IEC or DIN or NEMA
	focus RTI (length and width)
	MTF at -3 dB, M=2
	RMS (Root Mean Square)
	Zoom mode with user controlled cursors for measurements on LFS and MTF graphs.
Alignment system:	Automatic

Trigger system

Trigger modes	Automatic  (with external trig detector)
	Auto start, adjustable delay & window
	Manual start, adjustable window
Delay	0-50 000 ms
Window	10-50 000 ms

Accessories

R100 Trig detector To start and stop measurements automatically.
RFM Holder pro Holder for the Real-time FocusMeter.

The RFM Pro consists of a modified Real-time FocusMeter (RFM) and the RFM Holder Pro. In the RFM Pro the motors for xy-movement are removed. That makes the positioning of the detector more accurate according to the tube housing. The RFM Pro is intended for use with the RFM always mounted in the holder. The RFM Holder Pro is used by world leading X-ray tube manufacturers. It expands the use of the RFM when a higher degree of accuracy and repeatability of the positioning is required for example when doing absolute measurements in an X-ray tube production line.