Proximity Sensor for X-Ray Apparatus

• US 20070269012A1
• Filed: 08/26/2005
• Published: 11/22/2007
• Est. Priority Date: 08/31/2004
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Somers, Petrus
• Granted Patent: US 7,548,075 B2
• Time in Patent Office: Days
• US Class Current: 378/117
• CPC Class Codes: A61B 6/102 Protection against mechanical damage, e.g. anti-collision devices
• CPC Class Codes: H03K 17/955 using a capacitive detector
• CPC Class Codes: H03K 2217/960765 Details of shielding arrangements
• CPC Class Codes: H03K 2217/960775 Emitter-receiver or "fringe" type detection, i.e. one or more field emitting electrodes and corresponding one or more receiving electrodes

Abstract

A capacitive proximity sensor comprising an emitter electrode (104) capacitively coupled to receive an electrode (102). A first active guard electrode (110), driven by the output of a unity gain amplifier (108), is provided in respect of the receive electrode (102), to shield parts thereof not facing a potential obstacle (122), and a grounded shield (126) is provided in respect of the emitter electrode (104) to shield parts thereof not facing a potential obstacle (122). A second active guard electrode (103) is provided between the emitter and receiver electrodes (104, 102), just behind the cover (106), which is also driven by the output of the amplifier (108). The second active guard electrode (103) acts to block shortened electric field lines (124) between the emitter and receiver electrodes (104, 102), thereby improving accuracy and reliability of the sensor.

Claims

1. A proximity sensor, comprising an emitter electrode (104) and a receiver electrode (102), and means (101) for generating an electric field (124) from said emitter electrode (104) to said receiver electrode (102), wherein detection of an object (122) in the proximity of the sensor is indicated by a reduction of sensor output voltage, the sensor further comprising an electrically driven guard electrode (103) located between said emitter and receiver electrodes (104, 102).

2. A proximity sensor according to claim 1, further comprising a second, electrically driven guard electrode (110) in respect of said receiver electrode (102), to shield parts thereof not facing a potential object (122).

3. A proximity sensor according to claim 2, wherein said receiver electrode (102) is connected to the input of an amplifier (108), the output of which drives said first and second guard electrodes (103, 110).

4. A proximity sensor according to claim 3, wherein the gain of said amplifier (108) is substantially unity.

5. A proximity sensor according to claim 1, wherein a grounded shield (126) is provided in respect of said emitter electrode (104), to shield parts thereof not facing a potential object (122).

6. A swing arm (1) for an imaging system, the swing arm (1) comprising a radiation source (4) and detector (5), and further comprising one or more proximity sensors according to claim 1.

7. An imaging system, comprising a swing arm (1) according to claim 6, motive means for moving said swing arm (1) to a desired position relative to a subject to be imaged, and means for controlling said motive means according to the output of said one or more proximity sensors.