EP0352952A2 — Optical apparatus

Claim 1

Independent Claim 137 words

A method of range measurement comprising the steps of passing a laser beam through an optical system (12, 23) so as to be projected into an object field containing an object (28) to be ranged, detecting light reflected from the object, varying the focus distance (D) between an output (56) of the optical system and the position at which the beam is focused by operation of a focus distance varying means (31, 32 or 62), measuring a parameter of the detected light which is characteristic of laser speckle, determining a setting of the focus distance varying means at which the value of the speckle parameter is consistent with the beam being focused onto the object, and determining from calibration of the focus distance varying means the corresponding value of focus distance as a measurement of range (R).

Claim 2

Independent Claim 137 words

A method of range measurement comprising the steps of passing a laser beam through an optical system (12, 23) so as to be projected into an object field containing an object (28) to be ranged, detecting light reflected from the object, varying the focus distance (D) between an output (56) of the optical system and the position at which the beam is focused by operation of a focus distance varying means (31, 32 or 62), measuring a parameter of the detected light which is characteristic of laser speckle, determining a setting of the focus distance varying means at which the value of the speckle parameter is consistent with the beam being focused onto the object, and determining from calibration of the focus distance varying means the corresponding value of focus distance as a measurement of range (R).

Claim 3

Dependent Claim 87 words

A method as claimed in claim 1 in which the beam is directed on to a selected area of the object and scanned across the selected area, the reflected light being detected by means of a photodetector (27) producing an electrical output signal, the speckle parameter being measured as the output of circuit means (94, 106, 107) responsive to noise in the output signal and the presence of maximum noise in the output signal being taken as being consistent with the beam being focused onto the object.

Claim 4

Independent Claim 40 words

A method as claimed in either of claims 1 and 2 wherein the focus distance varying means comprises a mirror system (62) which is movable to vary the path length travelled by a converging or diverging portion of the beam.

Claim 5

Independent Claim 31 words

A method as claimed in either of claims 1 and 2 wherein the focus distance varying means comprises at least one axially movable lens (31,32) in the path of the beam.

Claim 6

Independent Claim 91 words

A method as claimed in any of claims 2 to 4 in which range is measured by means of apparatus comprising the optical system, the apparatus being selectively operable to generate a television image of the object field by scanning the beam in raster fashion, the apparatus being switchable between ranging mode and imaging mode as required, and wherein the apparatus includes means (52) operable to vary the depth of focus of the beam such that in the ranging mode the depth of focus is less than in the imaging mode.

Claim 7

Dependent Claim 54 words

A method as claimed in claim 5 wherein the depth of focus is varied by actuation of a zoom lens (52) of the optical system which provides a field angle at the output of the optical system which is reduced in the ranging mode relative to the field angle provided in the imaging mode.

Claim 8

Dependent Claim 31 words

A method as claimed in claim 5 wherein the depth of focus is varied by passing the beam through different lenses (152, 153) in the ranging mode and imaging mode respectively.

Claim 9

Independent Claim 112 words

A method as claimed in any of claims 5 to 7 wherein the apparatus further comprises a scanning head (39) including at least one pivoting mirror (16, 18, 69), the scanning head being operable in the imaging mode to deflect the laser beam into an input (35) of the optical system such that the angle between the beam and optical axis is scanned in raster fashion, a corresponding raster scan being produced in the beam (38) projected from the output of the optical system to scan the object, and the scanning head being operable in the ranging mode to provide scanning of the beam only over a selected area of the object.

Claim 10

Independent Claim 64 words

A method as claimed in any of claims 5 to 8 wherein the beam is deflected towards the selected area by light deflecting means (81, 87) operable to vary the direction of the optical axis at the output of the optical system when the selected area would otherwise be located outside of the reduced field angle of the optical system in the ranging mode.

Claim 11

Independent Claim 22 words

A method as claimed in any preceding claim wherein the optical system further comprises an optical relay (12) of an endoscope (10).

Claim 12

Dependent Claim 216 words

Imaging apparatus comprising an optical system (12, 23) defining an optical axis, a scanning head (39) connected to an input (35) of the optical system, a laser light source (14) connected to an input of the scanning head, the scanning head being operable to project a laser beam (15) into the input of the optical system such that the angle between the beam and the axis is scanned in raster fashion, the optical system having an output (56) comprising a light transmitting window from which the laser beam is projected towards an object field, a light receiving window (54) located adjacent the transmitting window for collecting light reflected from the object field, detection means (27, 94, 106, 107) producing an electrical output signal responsive to light collected by the light receiving window, and electronic apparatus (29) operable to produce a television signal from the detector means output signal whereby a television image of an object in the object field may be obtained, wherein the optical system comprises an endoscope (10) having an elongate tube (11), the transmitting window and the receiving window being mounted in a distal end (36) of the tube for insertion into inaccessible areas, and the optical system including an optical relay (12) through which the optical axis extends longitudinally within the tube.

Claim 13

Dependent Claim 216 words

Imaging apparatus comprising an optical system (12, 23) defining an optical axis, a scanning head (39) connected to an input (35) of the optical system, a laser light source (14) connected to an input of the scanning head, the scanning head being operable to project a laser beam (15) into the input of the optical system such that the angle between the beam and the axis is scanned in raster fashion, the optical system having an output (56) comprising a light transmitting window from which the laser beam is projected towards an object field, a light receiving window (54) located adjacent the transmitting window for collecting light reflected from the object field, detection means (27, 94, 106, 107) producing an electrical output signal responsive to light collected by the light receiving window, and electronic apparatus (29) operable to produce a television signal from the detector means output signal whereby a television image of an object in the object field may be obtained, wherein the optical system comprises an endoscope (10) having an elongate tube (11), the transmitting window and the receiving window being mounted in a distal end (36) of the tube for insertion into inaccessible areas, and the optical system including an optical relay (12) through which the optical axis extends longitudinally within the tube.

Claim 14

Dependent Claim 25 words

Imaging apparatus as claimed in claim 11 further comprising ranging means operable to measure the range of an object in the object field under inspection.

Claim 15

Dependent Claim 105 words

Apparatus as claimed in claim 12 wherein the ranging means comprises means (31, 32 or 62) varying the focus distance (D) between the light transmitting window (56) and the position at which the beam is focused and circuit means (94, 106, 107) responsive to noise characteristic of laser speckle in the output signal of the detection means, the electronic apparatus being operable to determine a setting of the focus distance varying means at which maximum noise is present in the output signal and to determine from calibration of the focus distance varying means the corresponding value of focus distance as a measure of range (R).

Claim 16

Dependent Claim 63 words

Apparatus as claimed in claim 13 wherein the electronic apparatus includes a frame store (96) containing image information of each pixel of the television image, the frame store information being refreshed at the scanning rate of the scanning head and the television signal being derived from the information in the frame store at a scanning rate which is independent of the scanning head.

Claim 17

Dependent Claim 48 words

Apparatus as claimed in claim 14 wherein the electronic apparatus provides for an image generated by a previous scan in image mode operation to be stored in the frame store during operation of the apparatus in ranging mode such that a television image may continue to be displayed.

Claim 18

Dependent Claim 39 words

Apparatus as claimed in any of claims 11 to 15 wherein the detection means comprises a fibre optic link (37) extending between the light receiving window and a photodetector (27) at the proximal end (35) of the endoscope tube.

Claim 19

Dependent Claim 39 words

Apparatus as claimed in any of claims 11 to 16 wherein the scanning head is removably connected to the endoscope tube, the endoscope tube being connectable to an eyepiece (162) for use in direct viewing as a conventional endoscope.

Claim 20

Dependent Claim 39 words

Apparatus as claimed in any of claims 11 to 17 wherein the optical system includes a zoom lens (52) located in the distal end portion (36) of the tube and means (57, 91) for remotely actuating the zoom lens.

Claim 21

Dependent Claim 90 words

An optical assembly comprising an objective lens (77) and a field lens (80) which is movable relative to the objective lens between a first position adjacent the objective lens and a second position spaced from the objective lens, the field lens and objective lens in combination defining a focal plane (86) which is at the same location relative to the objective lens for both first and second positions of the field lens and wherein the field lens passes through the focal plane in moving between the first and second positions.

Claim 22

Dependent Claim 90 words

An optical assembly comprising an objective lens (77) and a field lens (80) which is movable relative to the objective lens between a first position adjacent the objective lens and a second position spaced from the objective lens, the field lens and objective lens in combination defining a focal plane (86) which is at the same location relative to the objective lens for both first and second positions of the field lens and wherein the field lens passes through the focal plane in moving between the first and second positions.

Claim 23

Dependent Claim 26 words

An optical assembly as claimed in claim 19 wherein at least one of the field lens and the objective lens comprises a plurality of lens elements.

Claim 24

Dependent Claim 17 words

An optical assembly as claimed in claim 19 wherein the field lens comprises a single thick element.

Claim 25

Dependent Claim 25 words

An optical assembly as claimed in any of claims 19 to 21 wherein the objective lens and the field lens are both of positive power.

Claim 26

Dependent Claim 18 words

An optical assembly as claimed in any of claims 19 to 22 wherein the field lens is asymetric.

Claim 27

Dependent Claim 35 words

An optical assembly as claimed in any of claims 19 to 23 wherein the field lens and objective lens in combination comprise a zoom lens arranged in series with an optical relay of an endoscope.

Optical apparatus

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