ISO 10110 Optical Drawing Standard

ISO 10110 is a 13-part standard describing the preparation of drawings for optical components and systems. Each part covers a different aspect of the optical drawing.

Part 1 covers the mechanical aspects of optical drawings that are specific to optics and not alreadycovered in one of the ISO mechanical drawing standards. Important points to note are

●  The use of the metric system for linear dimensions is established, although the standard does allow use of the English system (and must be stated on the drawing). The use of the metric system per ASME Y14.5M will satisfy the ISO standards, except that a comma is used in the ISO standard instead a period to signify decimal point.

●  GD&T as described in the ISO system is used for presentation and dimensioning of optical components and assemblies. The ISO standards are very similar to ASME Y14.5M, but there are several important differences which should be reviewed and understood.

●  First angle projection is used (as opposed to prevalent third-angle projection used in the US) for illustration of parts

Part 2 covers stress birefringence of the part. The indication in the drawing is 0/X, where X is themaximum birefringence in nm/cm. OPD due to stress birefringence is a*σ*K, where a is path length incm, σ is residual stress in N/mm, and K is difference in photoelastic constants in 10-7 mm / N. A retardation > 20 nm / cm corresponds to a coarse anneal, and a retardation of < 10 nm/cm is a fine anneal.

Part 3 covers bubbles and inclusions. The callout is 1/NxA where N is the number of allowed bubbles or inclusions, and A is the length of the side of a square in mm. A2 is the area that the bubble or inclusion obscures. The obscured area may be sub-divided into smaller bubbles, provided that the obscured area is no larger than designated. A typical designation would be 1/3x.1 (3 bubbles allowed, each covering an area no larger than 0.12 = 0.01 mm2). This system is also used for designation of surface defects as covered in Part 7.

Part 4 covers imperfections due to inhomogeneity (variations in index of refraction from nominal) and striae (variations in index of refraction inside the glass part). The callout is 2/A;B, where A is the class number for inhomogeneity and B is the class for striae.

Part 5 describes the surface form tolerances for the optical surfaces. This is indicated on the drawing by 3/A(B/C). A is the maximum spherical sag error from test plate. A dash can be substituted for A where the radius tolerance is a dimension. B is the p-v maximum irregularity, and C is the maximum rotationally symmetric p-v figure error (best fit aspheric surface). The units are fringes (one half wavelength of 546.07 nm) and RMS specification for fringes can be used. For example, 3/4(1) implies the sag tolerance is 4 fringes and the p-v irregularity is no greater than 1 fringe. A callout of 3/-(2) implies a p-v irregularity of 2 fringes, and the radius of curvature is tolerance by the radius specification if the surface is spherical (untoleranced if plano).

Part 6 covers centering tolerances (centring). The callout is 4/α, where α is the angle between the datum and the surface. The indication is always the same for each surface, but the method of indicating the datum follows mechanical drawing practice. A polished surface can be a datum, and is often the best choice.

Part 7 covers surface imperfection tolerances. The callout is 5/NxA, and is similar to that of Part 3. Coating imperfections are preceded by a C, long scratches preceded by an L, and edge chips by an E. Examples are: 5/NxA; CN’xA’; LN”xA”, EA’”. A’” is the chip protrusion from the edge.

Part 8 covers the surface texture, and uses a texture symbol as the designator. This designates the quality of polish applied to the optical surfaces, and indicates ground surfaces (typically applied to edges).

Part 9 specifies surface treatment and coatings, The clear aperture (referenced as the optically effective surface in ISO 10110) must be specified in the drawing. The box that identifies the coating requirements specifies them according to ISO 9211. A common example for a surface with transmission requirement greater than 0.9 for a wavelength range from 450 to 750 nm would be . The callout can also refer to a graph,

with a callout stating “spectral reflectance as in graph xx for angle of incidence < 15°”. Graph xx would then be indicated elsewhere on the drawing. The coating could also be referred to as a manufacturer’s coating trade name, and would not need to be reproduced on the optical element drawing. The coating callout can also indicate a surface to be cemented.

ISO 10110-10 describes how to represent the data of the lens element in tabular form. While the ISO 10110 standard attempts to present optical components with a minimum amount of notes, the amount of information presented can become imposing. This is particularly true for simple lens elements, where a simpler method of presenting the information could be used to avoid ambiguity and errors in reading.

Part 11 describes maximum allowable tolerances on features of the optical elements when thosetolerances are not specifically called out on the optical drawing. This is different than how tolerances are handled in the US. Typically, an ASME Y14.5M drawing will have block (or shop) tolerances called out on the part, and these are in no way standardized in Y14.5M. Part 11 of ISO 10110 is an attempt to guarantee that no optical element will be manufactured to looser tolerances than specified in the standard unless specifically called out in the drawing.

Part 12 of ISO 10110 involves specifying aspheric surfaces. The procedures used to indicate aspheres on optical drawings are similar to those for ordinary surfaces, with a few exceptions. First, the type of surface should be indicated clearly. The radius on the face of the drawing is replaced by the word “asphere” or by the type of asphere for standard types. The equation which describes the surface should be given in a note. Slope tolerance and sampling length should be specified. Datums and datum systems are defined differently in ISO 10110-12 than they are in ISO 5459. The details of the datum system used in Part 12 stem from the fact that aspheric surfaces are frequently located mechanically during fabrication and in the optical system. If an alternate datum system is desired, a note on the drawing should be included saying, for example, “Indications of datums according to ISO 5459”.

Part 13 describes indications for laser power damage, or laser irradiation damage thresholds. The indication is given by 6/Hth; λ; pdg; fp; nTS x np for pulsed lasers, or 6/Eth; λ; nTS for continuous lasers. The 6/ code is associated with 3/, 4/, and 5/ codes on the drawing. “6/” is the indication for laser damage specification. λ is the wavelength of the laser. “pdg” is the pulse duration group number from ISO 11254, “fp” is the pulse repetition rate in Hz; “nTS” is the number of test sites on the sample surface.