Ophthalmic lens manufacture

Abstract: In the manufacture of an ophthalmic lens according to a prescription P, a lens blank is ground to the desired dioptre surface and finished on a lens surfacing machine LSM. The prescription details of the lens are fed into a computer C which is programmed to determine the appropriate speed and time for lens surfacing after grinding, and produce on a printer PR a corresponding document or job sheet JS which combines visual information 1 for an operative as to the lapping die or lap to be selected and a "job" identifier 2 which provides computer identification of the particular job to which the prescription P and document JS relate. The identification of the job by the computer C results in computer control of the lens surfacing machine LSM in respect of lapping speed and time for the lens finishing operation.

Description: The invention relates to the manufacture of ophthalmic lenses, and is particularly concerned with the final surfacing (smoothing and polishing) of the lenses on a lens surfacing machine. With such a machine the lens surfacing is achieved in a "lapping" operation with relative orbital motion of the lens, ground to the required dioptre surface, and a matching die or "lap" on which an abrasive/polishing pad conforming to the lap surface is adhered. The invention is particularly applicable to the surfacing of spectacle lenses starting from the individual prescription supplied by an optician or optometrist. The lapping speed and time and pressure of the machine are variable, and for surfacing a given lens these variables are more or less critical, and any material departure from the optimum values results in an expensive already-ground lens blank being scrapped. At present the machine speed and time is determined by an operative on the basis of skill and experience, and a careless or unskilled operative can produce much expensive scrap. There is in any case a tendency to operate the machine at mean values and not to change these for different lenses unless it is absolutely necessary, with the result that even when of acceptable quality the resultant lenses are not as good as they might have been. The invention overcomes this problem and ensures that near-optimum machine times and speeds are used at all times. AT-E-37678 discloses a process and apparatus for the computer control of edge grinding of an optical lens blank. With this apparatus data corresponding to the positions of the pupils of the intended wearer of the finished spectacles in relation to the position of the spectacle frame is input into the computer by displaying an image of the spectacle rim on a screen, and moving that image on the screen according to the known positions of the pupils of the wearer. The present invention extends computer control to the final surfacing of the optical surface of a lens. According to the invention, the lens prescription details are fed into a computer which is programmed to determine the appropriate speed and time for lens surfacing after grinding, and to produce a corresponding document which combines visual information for an operative as to the lapping die or lap to be selected and a job identifier which provides computer identification of the particular job to which the prescription and document relate, with identification thereof by computer resulting in computer control of the lens surfacing machine in respect of lapping speed and time. Said document may employ any form of information storage/display, but it is preferably a hard copy document in the form of a job sheet produced on a printer controlled by the producing computer and it will for convenience be described as such hereinafter, but without any intention of so limiting the invention or its application. The job identifier is preferably in the form of a printed bar code which, for job identification, is read by a reading head connected to the identifying computer. A single computer is preferably employed, both to prepare the job sheet from the prescription and to control the speed and time of the the lens surfacing machine. However, if desired separate computers may be employed - one to produce the job sheet and the other to identify the job therefrom and to control the machine. In this case the job sheet will include details of the speed and time information for the machine adapted to be read by said other computer, and information may be included in the form of a second bar code to be read by that computer. Prior to the surfacing operation pre-ground lens blanks are selected and finally ground to the desired dioptre surfaces. At present the lens blanks are selected from stock according to a chart prepared by lens designers, with the stock including blanks of various types of lens material, and the computer of the invention may be programmed to identify the appropriate blanks for grinding as well as to determine the speed and time of the surfacing machine. If desired the computer may also be programmed to control the lens grinding machine as well as the lens surfacing machine. Normally lens surfacing consists of two or more lapping operations, with a coarse pad followed by at least one finer pad, either on the same or on different machines. The computer may be programmed to control all the lapping operations for different speeds and times, when this is appropriate. The invention includes within its scope not only a process of manufacture of an ophthalmic lens employing a lens surfacing machine as aforesaid but also a control system for a lens surfacing machine according to claim 11. The invention will now be further described with reference to the accompanying drawing in the form of a flow diagram illustrating, by way of example, a lens surfacing procedure in accordance with the invention. The procedure commences with the lens prescription P provided by an optician or optometrist and which specifies the required powers of two spectacle lenses. The lens particulars are fed into a computer C controlling a printer PR which prints a job sheet JS. This job sheet is passed to the workshop W and includes visual instructions 1 for an operative and a job identifying bar code 2. The instructions 1 identify the lens blanks to be selected from stock at LB and contain setting up details for the lens grinding machine GM on which the lenses are ground to the prescription. The instructions 1 also identify the lapping dies to be selected from stock at LD, the ground lenses and the dies selected according to the printed instructions being placed on the lens surfacing machine LSM by the operative. The bar code 2 is now scanned by a reader head RH connected via lead 3 to the computer C, which thus identifies the particular job and from its memory selects the previously computed operating speed and time for the machine LSM appropriate to that job, the machine LSM being controlled correspondingly by the computer C via a control link 4. Normally the so-surfaced lenses will be passed to a second lens surfacing machine (not shown) similar to the machine LSM but with the dies fitted with a finer lapping pad. This second machine is similarly controlled by the computer C after identifying the job by reading the bar code 2.

Claims: Process of manufacture of an ophthalmic lens employing a lens surfacing machine (LSM), characterised in that the prescription (P) details of the lens are fed into a computer (C) which is programmed to determine the appropriate speed and time for lens surfacing after grinding, and to produce a corresponding document (JS) which combines visual information (1) for an operative as to the lapping die or lap to be selected and a job identifier (2) which provides computer identification of the particular job to which the prescription (P) and document (JS) relate, with identification thereof by computer resulting in computer control of the lens surfacing machine (LSM) in respect of lapping speed and time. Process of manufacture of an ophthalmic lens according to Claim 1, wherein said document is a hard copy document in the form of a job sheet (JS) produced on a printer (PR) controlled by the producing computer (C). Process of manufacture of an ophthalmic lens according to Claim 1 or Claim 2, wherein the job identifier is in the form of a printed bar code (2) which, for job identification, is read by a reading head (RH) connected to the identifying computer (C). Process of manufacture of an ophthalmic lens according to any one of the preceding claims, wherein a single computer (C) is employed, both to prepare the job sheet (JS) from the prescription (P) and to control the speed and time of the lens surfacing machine (LSM). Process of manufacture of an ophthalmic lens according to any one of Claims 1 to 3, wherein two separate computers are employed - one to produce the job sheet (JS) and the other to identify the job therefrom and to control the lens surfacing machine (LSM). Process of manufacture of an ophthalmic lens according to Claim 5, wherein the job sheet (JS) includes details of the speed and time information for the lens surfacing machine (LSM) adapted to be read by said other computer. Process of manufacture of an ophthalmic lens according to Claim 3 and Claim 6, wherein said speed and time information is included in the form of a second bar code to be read by said other computer. Process of manufacture of an ophthalmic lens according to any one of the preceding claims, wherein the computer (C) which identifies the job and determines the speed and time of the lens surfacing machine (LSM) also identifies the appropriate blank for grinding to the desired dioptre surface prior to the computer-controlled surfacing operation. Process of manufacture of an ophthalmic lens according to Claim 8, wherein the computer (C) which controls the lens surfacing machine (LSM) also controls the lens grinding machine (GM). Process of manufacture of an ophthalmic lens according to any one of the preceding claims, wherein the lens surfacing procedure consists of two or more lapping operations, with a coarse pad followed by at least one finer pad, either on the same or on different machines, and the computer (C) is programmed to control all the lapping operations for different speeds and times, as appropriate. A control system for a machine (LSM) used in the manufacture of an ophthalmic lens comprising a computer (C) adapted to be fed with data (P) relating to the lens and computer-controlled control means for the machine (LSM), characterised in that the machine (LSM) is a lens surfacing machine, in that the computer (C) is adapted to be fed with prescription details (P) of the lens, by means (PR) to produce a document (JS), in that the computer (C) is programmed to determine the appropriate speed and time for lens surfacing after grinding and to control said document-producing means (PR) to produce a document (JS) which combines visual information (1) for an operative as to the lapping die or lap to be selected and a job identifier (2) which provides computer identification of the particular job to which the prescription (P) and document (JS) relate, and by computer associated identifying means (RH) for reading the document (JS) with resultant computer control of the machine (LSM) in respect of lapping speed and time.

Inventors: NORVILLE FRANK GOODWIN, NORVILLE, FRANK GOODWIN
Applicants: NORVILLE OPTICAL CO LTD, NORVILLE OPTICAL COMPANY LIMITED
Application year: 1991
Main classification: B24B13
IPC codes: B24B13, G05B19