# US 2016/0249803 A1 · Focusing system and method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2016/0249803 A1 - Document ID: US20160249803A1 - Status: Published application - Kind: A1 - Application number: 14/632,971 - Filed: 2015-02-26 - Published: 2016-09-01 - Earliest claimed: 2015-02-26 - Assignees: Canon Kabushiki Kaisha - Applicants: Canon Kabushiki Kaisha - Inventors: Kenichi SAITO - Web page: https://patentgrep.com/patent/US20160249803A1 ## CPC - A61B 3/12: for looking at the eye fundus, e.g. ophthalmoscopes (A61B3/13 takes precedence) - A61B 3/0075: {provided with adjusting devices, e.g. operated by control lever} - A61B 3/1015: {for wavefront analysis} - A61B 3/1025: {for confocal scanning} - A61B 3/14: Arrangements specially adapted for eye photography - G02B 17/023: {for extending or folding an optical path, e.g. delay lines} - G02B 26/06: for controlling the phase of light (G02B26/08 takes precedence {, measuring optical phase difference G01J9/00}) - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract An apparatus for measuring a fundus of a subject. The apparatus includes a focusing unit which adjusts a defocus of the apparatus. The focusing unit includes a first focusing mirror and a second focusing mirror. The first focusing mirror and second focusing mirror are arranged so that an incident beam from the light source entering the focusing unit and an emitted beam exiting the focusing unit are substantially parallel to each other. Adjustment of the defocus is accomplished by moving both first focusing mirror and second focusing mirror such that incident beam and emitted beam remain substantially parallel to each other. The apparatus includes a wavefront sensor for detecting a shape of a wavefront. The apparatus includes a wavefront correction device. The wavefront correction device adjusts a wavefront of the light from the light source based on the shape of the wavefront detected by the wavefront sensor. ## Claims ### Claim 1 An apparatus for measuring a fundus of a subject comprising: an input for receiving light from a light source; a plurality of optically conjugate planes; a focusing unit which adjusts a defocus comprising: a first focusing mirror; and a second focusing mirror; wherein the first focusing mirror and the second focusing mirror are arranged so that an incident beam from the light source entering the focusing unit and an emitted beam exiting the focusing unit are substantially parallel to each other; wherein adjustment of the defocus is accomplished by moving both the first focusing mirror and the second focusing mirror such that the incident beam and the emitted beam remain substantially parallel to each other, and wherein the plurality of optically conjugate planes do not substantially move as the defocus is adjusted by moving both the first focusing mirror and the second focusing mirror; a wavefront sensor for detecting a shape of a wavefront; and a wavefront correction device; wherein the wavefront correction device adjusts a wavefront of the light from the light source based on the shape of the wavefront detected by the wavefront sensor. ### Claim 2 (depends on 1) The apparatus of claim 1, further comprising the light source. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein the first focusing mirror is a concave mirror. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein the second focusing mirror is a convex mirror. ### Claim 5 (depends on 1) The apparatus of claim 1, wherein the relative position of the first focusing mirror to the second focusing mirror remains unchanged during focusing. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the wavefront sensor detects aberrations after the focusing unit has corrected the defocus by moving the first focusing mirror and the second focusing mirror, and the wavefront correction device corrects aberrations based on the aberrations detected after the focusing unit has corrected the defocus. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein: the wavefront sensor detects the defocus generated by the subject; the focusing unit corrects the defocus by moving the first focusing mirror and the second focusing mirror based on the defocus detected by the wavefront sensor. ### Claim 8 (depends on 1) The apparatus of claim 1, wherein the wavefront correction device corrects aberrations while the focusing unit is correcting defocus. ### Claim 9 (depends on 8) The apparatus of claim 8, wherein the wavefront correction device starts correcting aberrations after the focusing has started correcting defocus and the defocus is below a threshold, and the focusing unit continues to adjust defocus. ### Claim 10 (depends on 1) The apparatus of claim 1, wherein the defocus is generated by the subject. ### Claim 11 (depends on 1) The apparatus of claim 1, wherein the incident beam and the emitted beam remain parallel such that an optical axis of the incident beam and an optical axis of the emitted beam are parallel and are not collinear with each other. ### Claim 12 (depends on 1) The apparatus of claim 1, wherein the focusing unit does not include an optical lens. ### Claim 13 (depends on 1) The apparatus of claim 1, wherein the adjustment of the defocus is accomplished by moving both the first focusing mirror and the second focusing mirror along a path that is substantially parallel to an optical axis of the incident beam and an optical axis of the emitted beam. ### Claim 14 (depends on 1) The apparatus of claim 1, wherein the incident beam is not collimated when it strikes the first focusing mirror. ### Claim 15 (depends on 1) The apparatus of claim 1, further comprising a detector for detecting light from the subject which has been reflected by the focusing mirrors and has been corrected by the wavefront correction device. ### Claim 16 (depends on 1) The apparatus of claim 1, further comprising a scanner for scanning the light from light source across the subject. ### Claim 17 (depends on 16) The apparatus of claim 16, wherein the scanner is positioned between the wavefront correction device and the focusing unit. ### Claim 18 (depends on 1) The apparatus of claim 1 wherein: the wavefront sensor is positioned at a first conjugate plane among the plurality of optically conjugate planes, wherein all of the conjugate planes among the plurality of optically conjugate planes are substantially optically conjugate with each other; and the wavefront correction device is positioned at a second conjugate plane among the plurality of conjugate planes ### Claim 19 (depends on 18) The apparatus of claim 18 wherein a plurality of curved mirrors are used to position: the wavefront sensor at the first conjugate plane among the plurality of conjugate planes; and the wavefront correction device at the second conjugate plane among the plurality of conjugate planes. ### Claim 20 (depends on 18) The apparatus of claim 18 further comprising: a detector for detecting light from the subject is positioned at a fourth conjugate plane among the plurality of conjugate planes; and a scanner for scanning the light from light source across the subject is positioned at a fifth conjugate plane among the plurality of conjugate planes.