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An improved ophthalmic instrument including a wavefront sensor that estimates aberrations in reflections of the light formed as a spot image on the retina of the human eye. The wavefront sensor includes a beam splitter operably disposed between a lenslet array and multiple imaging devices. The lensl

An improved ophthalmic instrument including a wavefront sensor that estimates aberrations in reflections of the light formed as a spot image on the retina of the human eye. The wavefront sensor includes a beam splitter operably disposed between a lenslet array and multiple imaging devices. The lenslet array forms a first array of spots, and the multiple imaging devices capture multiple images of the first array of spots for use in estimating the aberrations of the eye in a manner that minimizes the adverse effects of eye movement on the accuracy of such estimates. The beam splitter preferably comprises a prismatic beam splitter that splits light incident thereto into multiple arms. The multiple image devices may capture at least a first image of the first array of spots at best focus and a second image of the first array of spots near best focus for use in dynamically identifying sub-arrays (pixel areas) of the Hartmann spot imaging device (e.g., the imaging device that will be used for the determination of Hartmann spot positions) that avoid dot crossover for a particular wavefront measurement. An additional imaging device may be operably coupled to the beam splitter to capture at least one image of the pupil image plane of the lenslet array for use in identifying fiducial points therein (or for automatically identifying lenslet centers therein), thereby minimizing the adverse effects of eye movement on the accuracy of such measurements.

대표청구항 ▼

An improved ophthalmic instrument including a wavefront sensor that estimates aberrations in reflections of the light formed as a spot image on the retina of the human eye. The wavefront sensor includes a beam splitter operably disposed between a lenslet array and multiple imaging devices. The lensl

An improved ophthalmic instrument including a wavefront sensor that estimates aberrations in reflections of the light formed as a spot image on the retina of the human eye. The wavefront sensor includes a beam splitter operably disposed between a lenslet array and multiple imaging devices. The lenslet array forms a first array of spots, and the multiple imaging devices capture multiple images of the first array of spots for use in estimating the aberrations of the eye in a manner that minimizes the adverse effects of eye movement on the accuracy of such estimates. The beam splitter preferably comprises a prismatic beam splitter that splits light incident thereto into multiple arms. The multiple image devices may capture at least a first image of the first array of spots at best focus and a second image of the first array of spots near best focus for use in dynamically identifying sub-arrays (pixel areas) of the Hartmann spot imaging device (e.g., the imaging device that will be used for the determination of Hartmann spot positions) that avoid dot crossover for a particular wavefront measurement. An additional imaging device may be operably coupled to the beam splitter to capture at least one image of the pupil image plane of the lenslet array for use in identifying fiducial points therein (or for automatically identifying lenslet centers therein), thereby minimizing the adverse effects of eye movement on the accuracy of such measurements. 1. An ink jet printhead comprising: a plurality of nozzles; and at least one respective heater element corresponding to each nozzle, wherein each heater element is arranged for being in thermal contact with a bubble forming liquid, each heater element is configured to heat at least part of the bubble forming liquid to a temperature above its boiling point to form therein a collapsible gas bubble having a point of collapse, thereby to cause the ejection of a drop of an ejectable liquid through the nozzle corresponding to that heater element, and each heater element is configured such that the point of collapse of a bubble formed thereby is spaced from that heater element. 2. The printhead of claim 1 being configured to support the bubble forming liquid in thermal contact with each said heater element, and to support the ejectable liquid adjacent each nozzle. 3. The printhead of claim 1 wherein the bubble forming liquid and the ejectable liquid are of a common body of liquid. 4. The printhead of claim 1 being configured to print on a page and to be a page-width printhead. 5. The printhead of claim 1 wherein each heater element is configured such that the point of collapse of a bubble formed thereby is at a position at which there is no solid material forming part of the printhead. 6. The printhead of claim 1 wherein each heater element has parts defining a gap between them and is configured such that the point of collapse of a bubble formed thereby is within the gap corresponding to that heater element. 7. The printhead of claim 1 wherein each heater element is in the form of a suspended beam, arranged for being suspended over at least a portion of the bubble forming liquid so as to be in thermal contact therewith. 8. The printhead of claim 1 wherein each heater element is configured such that an actuation energy of less than 500 nanojoules (nJ) is required to be applied to that heater element to heat that heater element sufficiently to form a said bubble in the bubble forming liquid thereby to cause the ejection of a said drop. 9. The printhead of claim 1 configured to receive a supply of the ejectable liquid at an ambient temperature, wherein each heater element is configured such that the energy required to be applied thereto to heat said part to cause the ejection of a said drop is less than the energy required to heat a volume of said ejectable liquid equal to the volume of the said drop, from a temperature equal to said ambient temperature to said boiling point. 10. The printhead of claim 1 comprising a substrate having a substrate surface, wherein each nozzle has a nozzle aperture opening through the substrate surface and wherein the areal density of the nozzles relative to the substrate surface exceeds 10,000 nozzles per square cm of substrate surface. 11. The printhead of claim 1 wherein each heater element has two opposite sides and is configured such that a said gas bubble formed by that heater element is formed at both of said sides of that element. 12. The printhead of claim 1 comprising a structure that is formed by chemical vapor deposition (CVD), each nozzle being incorporated on the structure. 13. The printhead of claim 1 comprising a structure that is less than 10 microns thick, the nozzles being incorporated on the structure. 14. The printhead of claim 1 comprising a plurality of nozzle chambers, each corresponding to a respective nozzle and a plurality of said heater elements being disposed within each chamber, the heater elements within each chamber being formed on different respective layers to one another. 15. The printhead of claim 1 wherein each heater element is formed of solid material more than 90% of which, by atomic proportion, is constituted by at least one periodic element having an atomic number below 50. 16. The printhead of claim 1 wherein each heater element includes solid material and is configured for a mass of less than 10 nanograms of the solid material of that heater element to be heated to a temperature above said boiling point thereby to heat said part of the bubble forming liquid to a temperature above said boiling point thereby to cause the ejection of a said drop. 17. The printhead of claim 1 wherein each heater element is substantially covered by a conformal protective coating, the coating of each heater element having been applied substantially to all sides of the heater element simultaneously such that the coating is seamless. 18. A printer system incorporating a printhead, the printhead comprising: a plurality of nozzles; and at least one respective heater element corresponding to each nozzle, wherein each heater element is arranged for being in thermal contact with a bubble forming liquid, each heater element is configured to heat at least part of the bubble forming liquid to a temperature above its boiling point to form therein a collapsible gas bubble having a point of collapse, thereby to cause the ejection of a drop of an ejectable liquid through the nozzle corresponding to that heater element, and each heater element is configured such that the point of collapse of a bubble formed thereby is spaced from that heater element. 19. The system of claim 18 being configured to support the bubble forming liquid in thermal contact with each said heater element, and to support the ejectable liquid adjacent each nozzle. 20. The system of claim 18 wherein the bubble forming liquid and the ejectable liquid are of a common body of liquid. 21. The system of claim 18 being configured to print on a page and to be a page-width printhead. 22. The system of claim 18 wherein each heater element is configured such that the point of collapse of a bubble formed thereby is at a position at which there is no solid material forming part of the printhead. 23. The system of claim 18 wherein each heater element has parts defining a gap between them and is configured such that the point of collapse of a bubble formed thereby is within the gap corresponding to that heater element. 24. The system of claim 18 wherein each heater element is in the form of a suspended beam, arranged for being suspended over at least a portion of the bubble forming liquid so as to be in thermal contact therewith. 25. The system of claim 18 wherein each heater element is configured such that an actuation energy of less than 500 nanojoules (nJ) is required to be applied to that heater element to heat that heater element sufficiently to form a said bubble in the bubble forming liquid thereby to cause the ejection of a said drop. 26. The system of claim 18, wherein the printhead is configured to receive a supply of the ejectable liquid at an ambient temperature, and wherein each heater element is configured such that the energy required to be applied thereto to heat said part to cause the ejection of a said drop is less than the energy required to heat a volume of said ejectable liquid equal to the volume of the said drop, from a temperature equal to said ambient temperature to said boiling point. 27. The system of claim 18 comprising a substrate having a substrate surface, wherein each nozzle has a nozzle aperture opening through the substrate surface and wherein the areal density of the nozzles relative to the substrate surface exceeds 10,000 nozzles per square cm of substrate surface. 28. The system of claim 18 wherein each heater element has two opposite sides and is configured such that a said gas bubble formed by that heater element is formed at both of said sides of that element. 29. The system of claim 18 comprising a structure that is formed by chemical vapor deposition (CVD), each nozzle being incorporated on the structure. 30. The system of claim 18 comprising a structure that is less than 10 microns thick, the nozzles being incorporated on the structure. 31. The system of claim 18 comprising a plurality of nozzle chambers, each corresponding to a respective nozzle and a plurality of said heater elements being disposed