Workable Specification For Cast Filters

Cast allyl carbonate is a high quality substrate for optical filters. However this is still a plastic material, and although at SEM we take every care in its production, blemishes do occur. These blemishes take the form of small inclusions and fine, trapped fibres. So that SEM can quantify the quality of products made from allyl carbonate, it is important to lay down a specification and inspection criteria. This is a specification that we feel is obtainable and repeatable, when viewed against our past performance. With individual project discussions, it may be possible to tighten up the specification, but this will be done by inspecting out defects and will have obvious implications on price.

Inspection Conditions.

The panel should be viewed from the front face under daylight conditions, with normal non-directional lighting. Viewing should take 15 seconds and from a distance of 450 mm.

Blemishes.

SIZE	CRITERIA (Window Area)	CRITERIA (Non Window Area)
<0.15 mm	Disregard	Disregard
0.15 - 0.3 mm	1 per 100 x 100 mm	2 per 100 x 100 mm
0.3 - 0.5 mm	0 per panel	1 per panel
0.5 - 0.75	0 per panel	0 per panel

Small Fibres.
Small fibres in cast allyl carbonate are not like the surface fibres in coated material. In coatings the fibre creates an inclusion on the surface which is highly visible. With the cast product fibres are very fine and are trapped within the material. These are difficult to see and do not produce a surface defect. These fibres are only visible when illuminated with a direct, bright light and do not effect the quality of a display.

Scratching.
No scratching is allowed on the panels.

Summary.
Please be assured that we will attempt to produce the best quality panels that we can at all times. This specification is an indication of worst case conditions.