Distance measuring apparatus using multiple switched interferometers

Claim 2

A distance measuring apparatus comprising: a reflecting mirror which moves in first and second directions that are perpendicular to each other and which has at least one reflecting member extending in said first direction by an amount less than a range within which said reflecting mirror moves in said first direction; at least two laser interferometers for irradiating said at least one reflecting member with respective laser beams and measuring distance from said reflecting mirror in said second direction based on reflected laser beams from said at least one reflecting member, said at least two laser interferometers being arranged so that the respective laser beams are separated in said first direction by an interval less than said amount; and a selection circuit for selecting an output from one of said laser interferometers as a measurement of distance from said reflecting mirror in said second direction, the selecting being performed while said reflecting mirror is moving and being dependent upon whether or not one of said laser beams is reflected from said at least one reflecting member or more than one of said laser beams are reflected from said at least one reflecting member.

Claim 3

A distance measuring apparatus according to claim 1, wherein said selection circuit performs selecting when more than one of said laser beams are reflected from one said reflecting member at the same time.

Claim 4

A distance measuring apparatus according to claim 1, wherein said selection circuit also sets a distance measurement result of one of said laser interferometers as a distance measurement result of another of said laser interferometers when an output of said other laser interferometer is selected in place of an output of said one laser interferometer.

Claim 5

A distance measuring apparatus according to claim 3, further comprising a correction control circuit which corrects a distance measurement result of said other laser interferometer based on a difference between distance measurement results of said one and said other laser interferometer when said selection circuit selects an output of said other laser interferometer.

Claim 6

A distance measuring apparatus according to claim 1, wherein each of said at least two laser interferometers includes a rotation amount detector for irradiating said at least one reflecting member with a plurality of laser beams at the same time and determining a rotation amount of said reflecting mirror based on measurement results obtained from said plurality of laser beams.

Claim 7

A distance measuring apparatus comprising: reflecting means which moves in a first direction and which has two reflecting members, each extending in said first direction by an amount less than a range within which said reflecting means moves in said first direction; at least two distance measuring means for irradiating said reflecting means with respective light beams and measuring distance from said reflecting means in a second direction perpendicular to said first direction, based on reflected light from said reflecting means, said at least two distance measuring means being arranged so that the respective light beams are separated in said first direction by an interval less than said amount; and selection means for selecting an output from one of said distance measuring means as a measurement of distance from said reflecting means in said second direction, the selecting being performed while said reflecting means is moving and being dependent upon whether or not one of said light beams is reflected from said reflecting means or more than one of said light beams are reflected from said reflecting means, said two reflecting members each extending in said first direction by an amount greater than an interval between two of said light beams and separated by an interval narrower than said interval between said two light beams, whereby at least one of said two light beams always irradiates one of said two reflecting members while said reflecting means is moving in said first direction within said range.

Claim 8

A distance measuring apparatus comprising: reflecting means which moves in a first direction and which has two reflecting members, each extending in said first direction by an amount less than a range within which said reflecting means moves in said first direction; at least two distance measuring means for irradiating said reflecting means with respective light beams and measuring distance from said reflecting means in a second direction perpendicular to said first direction, based on reflected light from said reflecting means, said at least two distance measuring means being arranged so that the respective light beams are separated in said first direction by an interval less than said amount; and selection means for selecting an output from one of said distance measuring means as a measurement of distance from said reflecting means in said second direction, the selecting being performed while said reflecting means is moving and being dependent upon whether or not one of said light beams is reflected from said reflecting means or more than one of said light beams are reflected from said reflecting means, said two reflecting members each extending in said first direction by an amount greater than an interval between two of said light beams and separated by an interval narrower than said interval between said two light beams, whereby at least one of said two light beams always irradiates one of said two reflecting members while said reflecting means is moving in said first direction within said range.

Claim 9

A distance measuring apparatus according to claim 6, wherein said selection means performs selecting when one of said two light beams is reflected from one of said two reflecting members and the other of said two light beams is reflected from the other of said two reflecting members and also performs selecting when both of said two light beams are reflected from one of said two reflecting members.

Claim 10

A distance measuring apparatus for measuring distance from a moving object, said object moving in a first direction, said distance from the moving object being measured in a second direction perpendicular to said first direction, said apparatus comprising: a first reflecting member attached to said moving object and extending in said first direction; a second reflecting member attached to said moving object and extending in a direction parallel to said first direction, said first and second reflecting members being shifted from each other in a third direction perpendicular to both of said first and second directions; first distance measuring means for irradiating said first reflecting member with a first light beam and measuring distance from said moving object in said second direction based on reflected light from said first reflecting member; second distance measuring means for irradiating said second reflecting member with a second light beam and measuring distance from said moving object in said second direction based on reflected light from said second reflecting member, said first and second light beams being separated from each other in said third direction; wherein said first and second reflecting members are arranged so that a state in which said first and second light beams irradiate said first and second reflecting members, respectively, and a state in which only one of said light beams irradiates one of said reflecting members, occur alternately while said object is moving in said first direction; and selection means for selecting an output from one of said first and second distance measuring means as a measurement of distance from said object in said second direction, the selecting being performed while said object is moving and being dependent upon whether or not one of said first and second light beams is reflected from one of said reflecting members or said first and second light beams are reflected from said first and second reflecting members, respectively, at the same time.

Claim 11

A distance measuring apparatus for measuring distance from a moving object, said object moving in a first direction, said distance from the moving object being measured in a second direction perpendicular to said first direction, said apparatus comprising: a first reflecting member attached to said moving object and extending in said first direction; a second reflecting member attached to said moving object and extending in a direction parallel to said first direction, said first and second reflecting members being shifted from each other in a third direction perpendicular to both of said first and second directions; first distance measuring means for irradiating said first reflecting member with a first light beam and measuring distance from said moving object in said second direction based on reflected light from said first reflecting member; second distance measuring means for irradiating said second reflecting member with a second light beam and measuring distance from said moving object in said second direction based on reflected light from said second reflecting member, said first and second light beams being separated from each other in said third direction; wherein said first and second reflecting members are arranged so that a state in which said first and second light beams irradiate said first and second reflecting members, respectively, and a state in which only one of said light beams irradiates one of said reflecting members, occur alternately while said object is moving in said first direction; and selection means for selecting an output from one of said first and second distance measuring means as a measurement of distance from said object in said second direction, the selecting being performed while said object is moving and being dependent upon whether or not one of said first and second light beams is reflected from one of said reflecting members or said first and second light beams are reflected from said first and second reflecting members, respectively, at the same time.

Claim 12

A distance measuring apparatus according to claim 8, wherein said first and second reflecting members overlap and said selection means performs selecting when said first and second light beams are reflected from said first and second reflecting members, respectively, at the same time.

Claim 13

A distance measuring apparatus according to claim 8, wherein said selection means also sets a distance measurement result of one of said first and second distance measuring means as a distance measurement result of the other of said first and second distance measuring means when an output of said other distance measuring means is selected in place of an output of said one distance measuring means.

Claim 14

A distance measuring apparatus according to claim 10, further comprising correction control means which corrects a distance measurement result of said other distance measuring means based on a difference between distance measurement results of said first and second distance measuring means when said selection means selects an output of said other distance measuring means.

Claim 15

A distance measuring apparatus according to claim 8, wherein each of said first and second distance measuring means includes a rotation amount detecting means for irradiating each of said first and second reflecting members, respectively, with a plurality of light beams at the same time and determining a rotation amount of said first and second reflecting members, respectively, based on measurement results obtained from each plurality of light beams, respectively.