Inspection apparatus

Claim 2

Apparatus for measuring the cross sectional diameter of a beam of radiation comprising filter means (104,122), radiation detector means (106,124,127), means (103,121) for passing said beam via said filter means (104,122) to said radiation detector means (106,124), characterised in that said filter means (104,122) has an optical axis (100), and transmissive and reflective portions (107,108), or transmissive and absorptive portions (107,108), or reflective and absorptive portions (107,108), each of said portions (107,108) having an arcuate width at each radial distance from said optical axis (100) such that there is a predetermined relationship between the diameter of the beam and the amount of radiation passed or reflected by said filter means (104,122).

Claim 3

Apparatus as claimed in claims 1 characterised in that one of said portions (107,108) comprise a plurality of petal shaped parts (107).

Claim 4

Apparatus as claimed in any of claims 1 or 2 characterised in that said predetermined relationship is substantially linear.

Claim 5

Apparatus as claimed in any of claims 1 to 3 characterised in that means (132,141) is provided to normalise a signal provided by said radiation detector means (106,127) to take into account other variations of the amount of radiation in the beam.

Claim 6

Apparatus as claimed in claim 4 characterised in that said means (132,141) provided to normalise the signal comprises means for collecting radiation from the same source as provides said beam of radiation.

Claim 7

Apparatus as claimed in any of claims 1 to 5 characterised in that said radiation detector means (106,124) includes radiation collector means (106,124).

Claim 8

7 Apparatus as claimed in claim 6characterised in that said radiation collector means (106,124) comprises the end of an optical fibre.

Claim 9

8 Apparatus as claimed in any of claims 1 to 7 in which the portions (107,108) are reflective and transmissive, characterised in that said radiation detector means (106,124,127) comprises first radiation detector means (124) for receiving radiation transmitted by said filter means (122), and second radiation detector means (127) is provided to receive radiation reflected by said filter means (122).

Claim 10

Apparatus as claimed in claim 8 characterised in that said filter means (122) includes, on its optical axis (100), a small part (125) absorptive of the radiation.

Claim 11

Apparatus as claimed in claim 8 or 9 characterised in that means is provided to receive signals from the first and second radiation detector means (124,127) to provide an output signal which is indicative of the diameter of the said beam.

Claim 12

Apparatus for measuring the position of a surface comprising means for passing a beam of radiation to said surface (27), means (39,103) for collecting radiation scattered from said surface (27), means for passing said collected radiation to a filter means (104,122), radiation detector means (106,124,127) for collecting radiation reflected from or transmitted by said filter means (104,122), said filter means (104,122) being arranged so that there is a predetermined relationship between the diameter of the beam of radiation passing to said filter means (104,122) and the amount of radiation passed or reflected by said filter (104,122) to said radiation detector means (106,124,127), the arrangement being such that movement of said surface (27) causes a change in the diameter of the radiation at said filter means (104,122) whereby said movement of said surface (27) is detected by variations in the amount of radiation reaching said radiation detector means (106,124,127).

Claim 13

Apparatus for measuring the position of a surface comprising means for passing a beam of radiation to said surface (27), means (39,103) for collecting radiation scattered from said surface (27), means for passing said collected radiation to a filter means (104,122), radiation detector means (106,124,127) for collecting radiation reflected from or transmitted by said filter means (104,122), said filter means (104,122) being arranged so that there is a predetermined relationship between the diameter of the beam of radiation passing to said filter means (104,122) and the amount of radiation passed or reflected by said filter (104,122) to said radiation detector means (106,124,127), the arrangement being such that movement of said surface (27) causes a change in the diameter of the radiation at said filter means (104,122) whereby said movement of said surface (27) is detected by variations in the amount of radiation reaching said radiation detector means (106,124,127).