Scanning beam position detecting apparatus for use in electronic printer

Claim 2

An electronic image printing apparatus for printing images on an image recording medium, said apparatus comprising: a housing assembly; means disposed in said housing assembly for mounting the image recording medium; means for producing at least one writing beam in response to electronic signals corresponding to an image of a subject selected for printing; means for producing a reference beam; means for optically directing and scanning the writing and reference beams in synchronism and spaced relation with respect to each other along at least one predetermined scanning path; means extending in spaced parallel relation along the entire extent of the scanning path for encoding and reflecting the reference beam incident thereon into a plurality of pulses of reflected radiation which pulses are representative of the position of the writing beam along the scanning path; means for detecting the reflected reference beam pulses to produce corresponding feedback control signals indicative of the writing beam position along the scanning path, and means for effecting the displacement of said scanning path with respect to the image recording medium to provide a two dimensional image scan.

Claim 3

An electronic image printing apparatus for printing images on an image recording medium, said apparatus comprising: a housing assembly; means disposed in said housing assembly for mounting the image recording medium; means operable for producing at least a writing beam in response to electronic signals corresponding to an image of a subject selected for printing; means operable for producing a reference beam; means for optically directing and for scanning the writing and reference beams in synchronism and displaced relation with respect to each other along at least a scanning path; encoding means for reflecting the reference beams incident thereon into a plurality of pulses of reflected light which pulses are representative of the position of the writing beam along the scanning path, said encoding means including a Fresnel mirror device positioned generally coextensively along the scanning path and immediately juxtaposed to an image plane on the image recording medium, said Fresnel mirror device reflecting the reference beam pulses; means for detecting a plurality of reflected reference beam pulses to produce corresponding feedback control signals; and, means for effecting the displacement of said scanning path with respect to the image recording medium to provide a two-dimensional image scan.

Claim 4

An electronic image printing apparatus for printing images on an image recording medium, said apparatus comprising: a housing assembly; means disposed in said housing assembly for mounting the image recording medium; means operable for producing at least a writing beam in response to electronic signals corresponding to an image of a subject selected for printing; means operable for producing a reference beam; means for optically directing and for scanning the writing and reference beams in synchronism and displaced relation with respect to each other along at least a scanning path; encoding means for reflecting the reference beams incident thereon into a plurality of pulses of reflected light which pulses are representative of the position of the writing beam along the scanning path, said encoding means including a Fresnel mirror device positioned generally coextensively along the scanning path and immediately juxtaposed to an image plane on the image recording medium, said Fresnel mirror device reflecting the reference beam pulses; means for detecting a plurality of reflected reference beam pulses to produce corresponding feedback control signals; and, means for effecting the displacement of said scanning path with respect to the image recording medium to provide a two-dimensional image scan.

Claim 5

The apparatus of claim 2 wherein: said Fresnel mirror device has a plurality of facets formed along one surface thereof and generally coextensive with the scanning path and reflective surfaces on selected facets, said facets including said reflective surfaces modulating the reference beam incident thereon to produce the reflected pulses which pulses are representative of the writing beam position.

Claim 6

The apparatus of claim 2 wherein: said detecting means is located immediately adjacent said reference beam producing means so that said reflected surfaces of said facets direct the reflected pulses thereto.

Claim 7

The apparatus of claim 2 wherein: said detecting means is at a location immediately adjacent said Fresnel mirror device which location is at an image of an exit pupil of said optical means.

Claim 8

The apparatus of claim 2 wherein: said means for effecting displacement includes means for driving the image recording medium in a printing direction.

Claim 9

An electronic image printing apparatus for printing images on an image recording medium, said apparatus comprising: a housing assembly; means disposed in said housing assembly for mounting the image recording medium; means operable for providing at least a writing beam in response to electronic signals corresponding to an image of a subject selected for printing; means operable for producing a reference beam; means for optically directing and for scanning the writing and reference beams in synchronism and displaced relation with respect to each other along at least a scanning path; encoding means for reflecting the reference beam incident thereon into plurality of pulses of reflected light which pulses are representative of the position of the writing and reference beam along the scanning path; said encoding means including a holographic encoding device extending generally coextensively with the scanning path and arranged to intercept the scanning reference beam and is immediately juxtaposed to an image plane on the image recording medium, said holographic encoding device is effective for defining the plurality of reflected pulses by having alternating reflective and non-reflective areas and directing the reference beam pulses at least towards said detecting means; means for detecting a plurality of reflected reference beam pulses to produce corresponding feedback control signals; and, means for effecting displacement of said scanning path with respect to the image recording medium to provide a two dimensional image scan.

Claim 10

An electronic image printing apparatus for printing images on an image recording medium, said apparatus comprising: a housing assembly; means disposed in said housing assembly for mounting the image recording medium; means operable for providing at least a writing beam in response to electronic signals corresponding to an image of a subject selected for printing; means operable for producing a reference beam; means for optically directing and for scanning the writing and reference beams in synchronism and displaced relation with respect to each other along at least a scanning path; encoding means for reflecting the reference beam incident thereon into plurality of pulses of reflected light which pulses are representative of the position of the writing and reference beam along the scanning path; said encoding means including a holographic encoding device extending generally coextensively with the scanning path and arranged to intercept the scanning reference beam and is immediately juxtaposed to an image plane on the image recording medium, said holographic encoding device is effective for defining the plurality of reflected pulses by having alternating reflective and non-reflective areas and directing the reference beam pulses at least towards said detecting means; means for detecting a plurality of reflected reference beam pulses to produce corresponding feedback control signals; and, means for effecting displacement of said scanning path with respect to the image recording medium to provide a two dimensional image scan.

Claim 11

The apparatus of claim 7 wherein: said holographic encoding device is of the phase type and is generally planar in configuration, said holographic encoding device being in engagement with the image recording medium at the image plane.

Claim 12

The apparatus of claim 7 wherein: said detecting means is located immediately adjacent said holographic encoding device which location is at an image of an exit pupil of said optical means.

Claim 13

The apparatus of claim 7 wherein: a lens device is positioned adjacent to said detecting means so as to change the magnification of the image of the pupil plane and cause convergence of the reflected pulses travelling from said holographic encoding device to said detecting means.

Claim 14

The apparatus of claim 2 wherein: said means for effecting displacement includes means for driving the image recording medium in a printing direction.

Claim 15

An electronic image printing apparatus for printing images on an image recording medium, said apparatus comprising: a housing assembly; means disposed in said housing assembly for mounting the recording medium; means operable for providing at least a writing beam in response to electronic signals corresponding to an image of a subject selected for printing; means for producing a reference beam; means for optically directing and for scanning the writing and reference beams in synchronism and displaced relation with respect to each other along at least a scanning path; encoding means for reflecting the reference beam incident thereon into a plurality of pulses of reflected light which pulses of reflected light are directed to at least said detecting means, the pulses are representative of the position of the writing beam along the scanning path; said encoding means including an encoding element comprised of alternating reflective and non-reflective areas extending along the scanning path, said encoding element being immediately juxtaposed to the image recording medium along the scanning path at the image plane; said encoding means further including a holographic lens which is generally coextensive with the scanning path and said encoding element, said lens arranged generally parallel and spaced from said encoding element; said holographic lens converges and directs the reflected light pulses from said encoding element towards at least said detecting means; means for detecting a plurality of reflected reference beam pulses to produce corresponding feedback control signals; and, means for effecting displacement of said scanning path with respect to the image recording medium to provide a two-dimensional image scan.

Claim 16

An electronic image printing apparatus for printing images on an image recording medium, said apparatus comprising: a housing assembly; means disposed in said housing assembly for mounting the recording medium; means operable for providing at least a writing beam in response to electronic signals corresponding to an image of a subject selected for printing; means for producing a reference beam; means for optically directing and for scanning the writing and reference beams in synchronism and displaced relation with respect to each other along at least a scanning path; encoding means for reflecting the reference beam incident thereon into a plurality of pulses of reflected light which pulses of reflected light are directed to at least said detecting means, the pulses are representative of the position of the writing beam along the scanning path; said encoding means including an encoding element comprised of alternating reflective and non-reflective areas extending along the scanning path, said encoding element being immediately juxtaposed to the image recording medium along the scanning path at the image plane; said encoding means further including a holographic lens which is generally coextensive with the scanning path and said encoding element, said lens arranged generally parallel and spaced from said encoding element; said holographic lens converges and directs the reflected light pulses from said encoding element towards at least said detecting means; means for detecting a plurality of reflected reference beam pulses to produce corresponding feedback control signals; and, means for effecting displacement of said scanning path with respect to the image recording medium to provide a two-dimensional image scan.

Claim 17

An electronic image printing apparatus for printing images on an image recording medium, said apparatus comprising: a housing assembly; means disposed in said housing assembly for mounting the recording medium; means operable for providing at least a writing beam in response to electronic signals corresponding to an image of a subject selected for printing; means for producing a reference beam; means for optically directing and for scanning the writing and reference beams in synchronism and displaced relation with respect to each other along at least a scanning path; encoding means including an encoding device for reflecting the reference beam incident thereon into a plurality of pulses of reflected light which pulses are directed to at least a common area and are representative of the position of the writing beam along the scanning path; and, ellipsoidal means extending along the scanning path for reflecting the pulses from said encoding device to said detecting means, said ellipsoidal means includes at least one surface which intercepts the transmitted pulses and directs them by reflection towards a reflecting surface, said reflecting surface having an ellipsoidal configuration which is shaped and dimensioned to insure that light reflected therefrom is directed to a common point at which is located said detecting means; means for detecting a plurality of reflected reference beam pulses to produce corresponding feedback control signals; and, means for effecting displacement of said scanning path with respect to the image recording medium to provide a two-dimensional image scan.

Claim 18

An electronic image printing apparatus for printing images on an image recording medium, said apparatus comprising: a housing assembly; means disposed in said housing assembly for mounting the recording medium; means operable for providing at least a writing beam in response to electronic signals corresponding to an image of a subject selected for printing; means for producing a reference beam; means for optically directing and for scanning the writing and reference beams in synchronism and displaced relation with respect to each other along at least a scanning path; encoding means including an encoding device for reflecting the reference beam incident thereon into a plurality of pulses of reflected light which pulses are directed to at least a common area and are representative of the position of the writing beam along the scanning path; and, ellipsoidal means extending along the scanning path for reflecting the pulses from said encoding device to said detecting means, said ellipsoidal means includes at least one surface which intercepts the transmitted pulses and directs them by reflection towards a reflecting surface, said reflecting surface having an ellipsoidal configuration which is shaped and dimensioned to insure that light reflected therefrom is directed to a common point at which is located said detecting means; means for detecting a plurality of reflected reference beam pulses to produce corresponding feedback control signals; and, means for effecting displacement of said scanning path with respect to the image recording medium to provide a two-dimensional image scan.

Claim 19

The apparatus of claim 13 wherein: said ellipsoidal means is a solid transparent block and said encoding device is attached to said block, said block directs the pulses by total internal reflection and lightpiping; said encoding device having a plurality of alternating transmissive and non-transmissive areas extending along the scanning path and arranged to transmit the reference beam incident thereon into a plurality of the pulses of light which pulses are representative of the position of the writing beam along the scanning path.

Claim 20

The apparatus of claim 14 wherein: said means for effecting displacement includes means for driving the image recording medium in a printing direction.

Claim 21

An electronic image printing apparatus for printing images on an image recording medium, said apparatus comprising: a housing assembly; means disposed in said housing assembly for mounting the recording medium; means operable for providing at least a writing beam in response to electronic signals corresponding to an image of a subject selected for printing; means for producing a reference beam; means for optically directing and for scanning the writing and reference beams in synchronism and displaced relation with respect to each other along at least a scanning path; encoding means for reflecting the reference beam incident thereon into a plurality of pulses of reflected light which pulses are directed to at least a common area and are representative of the position of the writing beam along the scanning path; means for detecting a plurality of reflected reference beam pulses to produce corresponding feedback control signals; said encoding means including an encoding device having a plurality of alternating reflective and non-reflective areas extending along the scanning path and arranged to reflect the reference beam incident thereon into a plurality of pulses of reflected light which pulses are representative of writing beam position along the scanning path; and ellipsoidal means extending along the scanning path for reflecting the reflected pulses from said encoding device to said detecting means, said ellipsoidal means includes a reflecting surface having an ellipsoidal configuration which is shaped and dimensioned to insure that light reflected therefrom is directed to a common point at which is located said detecting means; and means for effecting displacement of said scanning path with respect to the image recording medium to provide a two-dimensional image scan.

Claim 22

An electronic image printing apparatus for printing images on an image recording medium, said apparatus comprising: a housing assembly; means disposed in said housing assembly for mounting the recording medium; means operable for providing at least a writing beam in response to electronic signals corresponding to an image of a subject selected for printing; means for producing a reference beam; means for optically directing and for scanning the writing and reference beams in synchronism and displaced relation with respect to each other along at least a scanning path; encoding means for reflecting the reference beam incident thereon into a plurality of pulses of reflected light which pulses are directed to at least a common area and are representative of the position of the writing beam along the scanning path; means for detecting a plurality of reflected reference beam pulses to produce corresponding feedback control signals; said encoding means including an encoding device having a plurality of alternating reflective and non-reflective areas extending along the scanning path and arranged to reflect the reference beam incident thereon into a plurality of pulses of reflected light which pulses are representative of writing beam position along the scanning path; and ellipsoidal means extending along the scanning path for reflecting the reflected pulses from said encoding device to said detecting means, said ellipsoidal means includes a reflecting surface having an ellipsoidal configuration which is shaped and dimensioned to insure that light reflected therefrom is directed to a common point at which is located said detecting means; and means for effecting displacement of said scanning path with respect to the image recording medium to provide a two-dimensional image scan.

Claim 23

The apparatus of claim 16 wherein: said ellipsoidal means is a solid transparent block and said encoding device is integral with said block, said device and said block direct the pulses by reflection and lightpiping.

Claim 24

The apparatus of claim 16 wherein: said means for effecting displacement includes means for driving the image recording medium in a printing direction.

Claim 25

Apparatus for detecting positions of a scanning beam in an electronic printer having means operable for producing a scanning beam; means for mounting and driving an image recording medium in at least a printing direction; and means for optically directing and scanning the scanning beam along a scanning path on the image recording medium, said apparatus comprising: means operable for producing a reference beam; said directing and scanning means scanning the reference beam in synchronism and displaced from the scanning beam along the scanning path which is generally transverse to the printing direction; means for detecting a plurality of reflected pulses of the reference beam for producing corresponding feedback control signals; and, encoding means for reflecting the reference beam incident thereon into a plurality of pulses of reflected light which pulses are directed to at least said detecting means and are representative of the position of the scanning beam along the scanning path; said encoding means being positioned generally coextensively along the scanning path and being immediately juxtaposed to an image plane on the image recording medium, said encoding means including Fresnel mirror device which directs at least some of the reference beam pulses to said detecting means.

Claim 26

Apparatus for detecting positions of a scanning beam in an electronic printer having means operable for producing a scanning beam; means for mounting and driving an image recording medium in at least a printing direction; and means for optically directing and scanning the scanning beam along a scanning path on the image recording medium, said apparatus comprising: means operable for producing a reference beam; said directing and scanning means scanning the reference beam in synchronism and displaced from the scanning beam along the scanning path which is generally transverse to the printing direction; means for detecting a plurality of reflected pulses of the reference beam for producing corresponding feedback control signals; and, encoding means for reflecting the reference beam incident thereon into a plurality of pulses of reflected light which pulses are directed to at least said detecting means and are representative of the position of the scanning beam along the scanning path; said encoding means being positioned generally coextensively along the scanning path and being immediately juxtaposed to an image plane on the image recording medium, said encoding means including Fresnel mirror device which directs at least some of the reference beam pulses to said detecting means.

Claim 27

The apparatus of claim 19 wherein: said Fresnel mirror device has a plurality of facets formed along one surface thereof and generally coextensive with the scanning path and reflective surfaces on selected facets, said facets including said reflecting surfaces for modulating the reference beam incident thereon to produce the reflected pulses, which pulses are representative of writing beam positions.

Claim 28

The apparatus of claim 19 wherein: said detecting means is located immediately adjacent said Fresnel mirror device which location is at an image of an exit pupil of said optical means.

Claim 29

The apparatus of claim 19 wherein: said detecting means is located immediately adjacent said reference beam producing means.

Claim 30

Apparatus for detecting positions of a writing beam in an electronic printer having means operable for producing a scanning beam; means for mounting and driving an image recording medium in at least a printing direction; and means for optically directing and scanning the scanning beam along a scanning path on the image recording medium, said apparatus comprising: means operable for producing a reference beam; said directing and scanning means scanning the reference beam in synchronism and displaced from the scanning beam along the scanning path which is generally transverse to the printing direction; means for detecting a plurality of reflected pulses of the reference beam for producing corresponding feedback control signals; encoding means for reflecting the reference beam incident thereon into a plurality of pulses of reflected light which pulses are directed to at least said detecting means and are representative of the position of the scanning beam along the scanning path; said encoding means including a holographic encoding device extending generally coextensively with the scanning path and being arranged to intercept the scanning reference beam and is immediately juxtaposed to an image plane on the image recording medium; said holographic encoding device is effective for producing said plurality of reflected pulses by defining alternating reflective and non-reflective areas and directing the reference beam pulses at least towards said detecting means.

Claim 31

Apparatus for detecting positions of a writing beam in an electronic printer having means operable for producing a scanning beam; means for mounting and driving an image recording medium in at least a printing direction; and means for optically directing and scanning the scanning beam along a scanning path on the image recording medium, said apparatus comprising: means operable for producing a reference beam; said directing and scanning means scanning the reference beam in synchronism and displaced from the scanning beam along the scanning path which is generally transverse to the printing direction; means for detecting a plurality of reflected pulses of the reference beam for producing corresponding feedback control signals; encoding means for reflecting the reference beam incident thereon into a plurality of pulses of reflected light which pulses are directed to at least said detecting means and are representative of the position of the scanning beam along the scanning path; said encoding means including a holographic encoding device extending generally coextensively with the scanning path and being arranged to intercept the scanning reference beam and is immediately juxtaposed to an image plane on the image recording medium; said holographic encoding device is effective for producing said plurality of reflected pulses by defining alternating reflective and non-reflective areas and directing the reference beam pulses at least towards said detecting means.

Claim 32

The apparatus of claim 23 wherein: said holographic encoding device is of the phase type and is generally planar in configuration, said holographic encoding material being in engagement with the image recording medium at the image plane.

Claim 33

The apparatus of claim 23 wherein: said detecting means is located immediately adjacent said holographic encoding device which location is at an image of an exit pupil of said optical means.

Claim 34

The apparatus of claim 25 wherein: a lens device is positioned adjacent to said detecting means so as to change the magnification of the reflected pulses and cause convergence of the reflected pulses from said holographic encoding device.

Claim 35

Apparatus for detecting positions of a writing beam in an electronic apparatus having means operable for producing a scanning beam; means for mounting and driving an image recording medium in at least a printing direction; and means for optically scanning the scanning beam along a scanning path on the image recording medium, said apparatus comprising: means operable for producing a reference beam; said scanning means scanning the reference beam in synchronism and displaced from the scanning beam along the scanning path which is generally transverse to the printing direction; means for detecting a plurality of reflected pulses of the reference beam for producing corresponding feedback control signals; encoding means for reflecting the reference beam incident thereon and into a plurality of pulses of reflected light which pulses of reflected light are directed to at least a common area and are representative of the positions of the scanning beam along the scanning path; said encoding means including an encoding element comprised of alternating reflective and non-reflective areas extending along the scanning path, said encoding element immediately juxtaposed to the image recording medium along the scanning path at the image plane; said encoding means further including a holographic lens which is generally coextensive with the scanning path and said encoding element; said lens arranged generally parallel to and spaced from said encoding element; said holographic lens converges and directs the reflected light pulses form said encoding element towards at least said detecting means.

Claim 36

Apparatus for detecting positions of a writing beam in an electronic apparatus having means operable for producing a scanning beam; means for mounting and driving an image recording medium in at least a printing direction; and means for optically scanning the scanning beam along a scanning path on the image recording medium, said apparatus comprising: means operable for producing a reference beam; said scanning means scanning the reference beam in synchronism and displaced from the scanning beam along the scanning path which is generally transverse to the printing direction; means for detecting a plurality of reflected pulses of the reference beam for producing corresponding feedback control signals; encoding means for reflecting the reference beam incident thereon and into a plurality of pulses of reflected light which pulses of reflected light are directed to at least a common area and are representative of the positions of the scanning beam along the scanning path; said encoding means including an encoding element comprised of alternating reflective and non-reflective areas extending along the scanning path, said encoding element immediately juxtaposed to the image recording medium along the scanning path at the image plane; said encoding means further including a holographic lens which is generally coextensive with the scanning path and said encoding element; said lens arranged generally parallel to and spaced from said encoding element; said holographic lens converges and directs the reflected light pulses form said encoding element towards at least said detecting means.

Claim 37

Apparatus for detecting positions of a scanning beam in an electronic apparatus having means operable for producing a scanning beam; means for mounting and driving an image recording medium in at least a printing direction; and means for optically scanning the scanning beam along a scanning path on the image recording medium, said apparatus comprising: means operable for producing a reference beam; said scanning means scanning the reference beam in synchronism and displaced from the scanning beam along the scanning path which is generally transverse to the printing direction; means for detecting a plurality of reflected pulses of the reference beam for producing corresponding feedback control signals; encoding means for reflecting the reference beam incident thereon into a plurality of pulses of reflected light which pulses are directed to at least a common area and are representative of the positions of the scanning beam along the scanning path; said encoding means including an encoding device having a plurality of alternating reflective and non-reflective areas extending along the scanning path and arranged to reflect the reference beam incident thereon into a plurality of pulses of reflected light at least towards said detecting means, the pulses being representative of scanning beam position, and ellipsoidal means extending along the scanning path for reflecting the reflected pulses from said encoding device to said detecting means said ellipsoidal means includes at least one surface which allows passage of the reference beam to said encoding device and which intercepts the reflected pulses and directs them by reflection towards a reflecting surface, said reflecting surface having an ellipsoidal configuration which is shaped and dimensioned to insure that all light reflected therefrom is directed to a common point at which is located said detecting means.

Claim 38

Apparatus for detecting positions of a scanning beam in an electronic apparatus having means operable for producing a scanning beam; means for mounting and driving an image recording medium in at least a printing direction; and means for optically scanning the scanning beam along a scanning path on the image recording medium, said apparatus comprising: means operable for producing a reference beam; said scanning means scanning the reference beam in synchronism and displaced from the scanning beam along the scanning path which is generally transverse to the printing direction; means for detecting a plurality of reflected pulses of the reference beam for producing corresponding feedback control signals; encoding means for reflecting the reference beam incident thereon into a plurality of pulses of reflected light which pulses are directed to at least a common area and are representative of the positions of the scanning beam along the scanning path; said encoding means including an encoding device having a plurality of alternating reflective and non-reflective areas extending along the scanning path and arranged to reflect the reference beam incident thereon into a plurality of pulses of reflected light at least towards said detecting means, the pulses being representative of scanning beam position, and ellipsoidal means extending along the scanning path for reflecting the reflected pulses from said encoding device to said detecting means said ellipsoidal means includes at least one surface which allows passage of the reference beam to said encoding device and which intercepts the reflected pulses and directs them by reflection towards a reflecting surface, said reflecting surface having an ellipsoidal configuration which is shaped and dimensioned to insure that all light reflected therefrom is directed to a common point at which is located said detecting means.

Claim 39

The apparatus of claim 28 wherein: said ellipsoidal means is a solid transparent block and said encoding device is integral with said block, said device and said block direct the pulses by reflection and lightpiping

Claim 40

Apparatus for detecting positions of a scanning beam in an electronic apparatus having means operable for producing a scanning beam; means for mounting and driving an image recording medium in at least a printing direction; and means for optically scanning the scanning beam along a scanning path on the image recording medium, said apparatus comprising: means operable for producing a reference beam; said scanning means scanning the reference beam in synchronism and displaced from the scanning beam along the scanning path which is generally transverse to the printing direction; means for detecting a plurality of reflected pulses of the reference beam for producing corresponding feedback control signals; encoding means for reflecting the reference beam incident thereon into a plurality of pulses of reflected light which pulses are directed to at least a common area and are representative of the positions of the scanning beam along the scanning path; and, ellipsoidal means extending along the scanning path for reflecting the pulses from said encoding device to said detecting means, said ellipsoidal means includes a reflecting surface having a elliptical configuration which is shaped and dimensioned to insure that light reflected therefrom is directed to a common point at which is located said detecting means.

Claim 41

Apparatus for detecting positions of a scanning beam in an electronic apparatus having means operable for producing a scanning beam; means for mounting and driving an image recording medium in at least a printing direction; and means for optically scanning the scanning beam along a scanning path on the image recording medium, said apparatus comprising: means operable for producing a reference beam; said scanning means scanning the reference beam in synchronism and displaced from the scanning beam along the scanning path which is generally transverse to the printing direction; means for detecting a plurality of reflected pulses of the reference beam for producing corresponding feedback control signals; encoding means for reflecting the reference beam incident thereon into a plurality of pulses of reflected light which pulses are directed to at least a common area and are representative of the positions of the scanning beam along the scanning path; and, ellipsoidal means extending along the scanning path for reflecting the pulses from said encoding device to said detecting means, said ellipsoidal means includes a reflecting surface having a elliptical configuration which is shaped and dimensioned to insure that light reflected therefrom is directed to a common point at which is located said detecting means.

Claim 42

The apparatus of claim 30 wherein: said ellipsoidal means is a solid transparent block and said encoding device is attached thereto, said block directs the pulses by total internal reflection and lightpiping and, said encoding device having a plurality of alternating transmissive and non-transmissive areas extending along the scanning path and arranged to transmit the reference beam incident thereon into a plurality of the pulses of light which pulses are representative of the position of the writing beam along the scanning path.