20:
63:
are embedded in photochromic lenses. They are transparent to visible light without significant ultraviolet component, which is normal for artificial lighting. In another sort of technology, organic photochromic molecules, when exposed to ultraviolet (UV) rays as in direct sunlight, undergo a chemical
322:
With the photochromic material dispersed in the glass substrate, the degree of darkening depends on the thickness of glass, which poses problems with variable-thickness lenses in prescription glasses. With plastic lenses, the material is typically embedded into the surface layer of the plastic in a
331:
Typically, photochromic lenses darken substantially in response to UV light in less than one minute, and continue to darken a little more over the next fifteen minutes. The lenses begin to clear in the absence of UV light, and will be noticeably lighter within two minutes, mostly clear within five
51:
that are dark in bright sunlight, but clear, or more rarely, lightly tinted in low ambient light conditions. They darken significantly within about a minute of exposure to bright light and take somewhat longer to clear. A range of clear and dark transmittances is available.
64:
process that causes them to change shape and absorb a significant percentage of the visible light, i.e., they darken. These processes are reversible; once the lens is removed from strong sources of UV rays the photochromic compounds return to their transparent state.
339:
Because photochromic compounds fade back to their clear state by a thermal process, the higher the temperature, the less dark photochromic lenses will be. This thermal effect is called "temperature dependency" and prevents these devices from achieving true
344:
darkness in very hot weather. Conversely, photochromic lenses will get very dark in cold weather conditions. Once inside, away from the triggering UV light, the cold lenses take longer to regain their transparency than warm lenses.
212:
317:
268:
364:
provide tinted lenses that use photochromism to go from a dark to a darker state. They are typically used for outdoor sunglasses rather than as general-purpose lenses.
113:) to achieve the reversible darkening effect. These lenses darken when exposed to ultraviolet light of the intensity present in sunlight, but not in artificial light.
353:
116:
In glass lenses, when in the presence of UV-A light (wavelengths of 320–400 nm) electrons from the glass combine with the colourless silver
110:
970:
441:
522:
332:
minutes, and fully back to their non-exposed state in about fifteen minutes. A report by the
Institute of Ophthalmology at the
217:
Back in the shade, this reaction is reversed. The silver returns to its original ionic state, and the lenses become clear.
126:
39:
radiation. In the absence of activating light, the lenses return to their clear state. Photochromic lenses may be made of
23:
A photochromic eyeglass lens, part of the lens darkened after exposure to sunlight while the other part remained covered
274:
995:
791:
398:
Armistead, W. H.; Stookey, S. D. (April 10, 1964). "Photochromic
Silicate Glasses Sensitized by Silver Halides".
223:
907:
884:
740:
357:
1093:
1083:
515:
1073:
811:
771:
692:
582:
333:
105:) in a glass substrate. Plastic photochromic lenses use organic photochromic molecules (for example
1088:
1040:
672:
1035:
902:
776:
348:
A number of sunglass manufacturers and suppliers including INVU, BIkershades, Tifosi, Intercast,
445:
508:
844:
652:
336:
suggested that at their clearest photochromic lenses can absorb up to 20% of ambient light.
1000:
874:
786:
622:
612:
407:
373:
912:
8:
1020:
947:
942:
864:
839:
806:
667:
120:
to form elemental silver. Because elemental silver is visible, the lenses appear darker.
460:
411:
927:
849:
597:
587:
1078:
1005:
975:
932:
854:
766:
423:
73:
796:
781:
551:
490:
415:
990:
985:
834:
730:
707:
702:
687:
682:
677:
637:
607:
419:
102:
56:
35:
that darkens on exposure to light of sufficiently high frequency, most commonly
952:
922:
917:
1067:
859:
816:
722:
697:
592:
98:
94:
40:
662:
1025:
980:
937:
627:
602:
556:
427:
349:
77:
32:
1050:
1015:
735:
617:
47:. Glass lenses use visible light to darken. They are principally used in
36:
1045:
1010:
879:
647:
642:
500:
16:
Optical lenses that darken on exposure to certain wavelengths of light
1030:
801:
577:
572:
341:
106:
19:
750:
378:
48:
44:
826:
632:
361:
117:
72:
Photochromic lenses were developed by
William H. Armistead and
60:
745:
712:
546:
531:
461:"UCL in the News: Lookout's lenses blamed for sea accident"
207:{\displaystyle {\ce {AgCl + e^- <=> Ag + Cl^-}}}
168:
277:
226:
129:
97:
properties through the embedding of microcrystalline
311:
262:
206:
176:
175:
158:
157:
93:The glass version of these lenses achieves their
1065:
397:
312:{\displaystyle {\ce {Ag^+ + Cl^- -> AgCl}}}
971:Conservation and restoration of glass objects
516:
458:
263:{\displaystyle {\ce {Ag - e^- -> Ag^+}}}
523:
509:
530:
323:uniform thickness of up to 150 ÎĽm.
55:In one sort of technology, molecules of
18:
151:
1066:
504:
83:
13:
442:"THE TECHNOLOGY WITHIN THE LENSES"
14:
1105:
482:
1041:Radioactive waste vitrification
996:Glass fiber reinforced concrete
80:Glass Works Inc. in the 1960s.
452:
434:
391:
302:
246:
178:
153:
1:
908:Chemically strengthened glass
459:Selva Kumar (19 April 2007).
384:
741:Glass-ceramic-to-metal seals
420:10.1126/science.144.3615.150
326:
88:
67:
7:
367:
10:
1110:
961:
893:
825:
772:Chemical vapor deposition
759:
721:
693:Ultra low expansion glass
583:Borophosphosilicate glass
565:
539:
334:University College London
1011:Glass-reinforced plastic
673:Sodium hexametaphosphate
903:Anti-reflective coating
777:Glass batch calculation
658:Photochromic lens glass
489:"Photochromic lenses",
313:
264:
208:
74:Stanley Donald Stookey
24:
1036:Prince Rupert's drops
885:Transparent materials
845:Gradient-index optics
653:Phosphosilicate glass
314:
265:
209:
22:
1001:Glass ionomer cement
875:Photosensitive glass
802:Liquidus temperature
623:Fluorosilicate glass
374:Photosensitive glass
275:
224:
127:
1021:Glass-to-metal seal
943:Self-cleaning glass
865:Optical lens design
412:1964Sci...144..150A
164:
1094:Glass applications
1084:Glass compositions
1006:Glass microspheres
928:Hydrogen darkening
850:Hydrogen darkening
598:Chalcogenide glass
588:Borosilicate glass
309:
260:
204:
183:
59:or another silver
25:
1074:Corrective lenses
1059:
1058:
976:Glass-coated wire
948:sol–gel technique
933:Insulated glazing
870:Photochromic lens
855:Optical amplifier
807:sol–gel technique
406:(3615): 150–154.
358:Serengeti Eyewear
307:
295:
282:
252:
239:
230:
196:
189:
185:
140:
133:
84:Technical details
29:photochromic lens
1101:
797:Ion implantation
552:Glass transition
525:
518:
511:
502:
501:
496:
476:
475:
473:
471:
456:
450:
449:
444:. Archived from
438:
432:
431:
395:
318:
316:
315:
310:
308:
305:
301:
300:
293:
288:
287:
280:
269:
267:
266:
261:
259:
258:
257:
250:
245:
244:
237:
235:
228:
213:
211:
210:
205:
203:
202:
201:
194:
187:
186:
184:
182:
181:
174:
166:
165:
163:
156:
148:
146:
145:
138:
131:
37:ultraviolet (UV)
1109:
1108:
1104:
1103:
1102:
1100:
1099:
1098:
1089:Glass chemistry
1064:
1063:
1060:
1055:
991:Glass electrode
986:Glass databases
963:
957:
895:
889:
821:
755:
731:Bioactive glass
717:
703:Vitreous enamel
688:Thoriated glass
683:Tellurite glass
668:Soda–lime glass
638:Gold ruby glass
608:Cranberry glass
561:
535:
529:
492:How stuff works
488:
485:
480:
479:
469:
467:
457:
453:
440:
439:
435:
396:
392:
387:
370:
329:
296:
292:
283:
279:
278:
276:
273:
272:
253:
249:
240:
236:
231:
227:
225:
222:
221:
197:
193:
177:
170:
169:
167:
159:
152:
150:
149:
147:
141:
137:
130:
128:
125:
124:
103:silver chloride
91:
86:
70:
57:silver chloride
17:
12:
11:
5:
1107:
1097:
1096:
1091:
1086:
1081:
1076:
1057:
1056:
1054:
1053:
1048:
1043:
1038:
1033:
1028:
1023:
1018:
1013:
1008:
1003:
998:
993:
988:
983:
978:
973:
967:
965:
959:
958:
956:
955:
953:Tempered glass
950:
945:
940:
935:
930:
925:
923:DNA microarray
920:
918:Dealkalization
915:
910:
905:
899:
897:
891:
890:
888:
887:
882:
877:
872:
867:
862:
857:
852:
847:
842:
837:
831:
829:
823:
822:
820:
819:
814:
809:
804:
799:
794:
792:Glass modeling
789:
784:
779:
774:
769:
763:
761:
757:
756:
754:
753:
748:
743:
738:
733:
727:
725:
723:Glass-ceramics
719:
718:
716:
715:
710:
705:
700:
695:
690:
685:
680:
675:
670:
665:
663:Silicate glass
660:
655:
650:
645:
640:
635:
630:
625:
620:
615:
610:
605:
600:
595:
590:
585:
580:
575:
569:
567:
563:
562:
560:
559:
554:
549:
543:
541:
537:
536:
534:science topics
528:
527:
520:
513:
505:
499:
498:
484:
483:External links
481:
478:
477:
451:
448:on 2012-12-16.
433:
389:
388:
386:
383:
382:
381:
376:
369:
366:
328:
325:
320:
319:
304:
299:
291:
286:
270:
256:
248:
243:
234:
215:
214:
200:
192:
180:
173:
162:
155:
144:
136:
99:silver halides
90:
87:
85:
82:
69:
66:
15:
9:
6:
4:
3:
2:
1106:
1095:
1092:
1090:
1087:
1085:
1082:
1080:
1077:
1075:
1072:
1071:
1069:
1062:
1052:
1049:
1047:
1044:
1042:
1039:
1037:
1034:
1032:
1029:
1027:
1024:
1022:
1019:
1017:
1014:
1012:
1009:
1007:
1004:
1002:
999:
997:
994:
992:
989:
987:
984:
982:
979:
977:
974:
972:
969:
968:
966:
960:
954:
951:
949:
946:
944:
941:
939:
936:
934:
931:
929:
926:
924:
921:
919:
916:
914:
911:
909:
906:
904:
901:
900:
898:
892:
886:
883:
881:
878:
876:
873:
871:
868:
866:
863:
861:
860:Optical fiber
858:
856:
853:
851:
848:
846:
843:
841:
838:
836:
833:
832:
830:
828:
824:
818:
817:Vitrification
815:
813:
810:
808:
805:
803:
800:
798:
795:
793:
790:
788:
787:Glass melting
785:
783:
782:Glass forming
780:
778:
775:
773:
770:
768:
765:
764:
762:
758:
752:
749:
747:
744:
742:
739:
737:
734:
732:
729:
728:
726:
724:
720:
714:
711:
709:
706:
704:
701:
699:
698:Uranium glass
696:
694:
691:
689:
686:
684:
681:
679:
678:Soluble glass
676:
674:
671:
669:
666:
664:
661:
659:
656:
654:
651:
649:
646:
644:
641:
639:
636:
634:
631:
629:
626:
624:
621:
619:
616:
614:
611:
609:
606:
604:
601:
599:
596:
594:
593:Ceramic glaze
591:
589:
586:
584:
581:
579:
576:
574:
571:
570:
568:
564:
558:
555:
553:
550:
548:
545:
544:
542:
538:
533:
526:
521:
519:
514:
512:
507:
506:
503:
494:
493:
487:
486:
466:
462:
455:
447:
443:
437:
429:
425:
421:
417:
413:
409:
405:
401:
394:
390:
380:
377:
375:
372:
371:
365:
363:
359:
355:
351:
346:
343:
337:
335:
324:
297:
289:
284:
271:
254:
241:
232:
220:
219:
218:
198:
190:
171:
160:
142:
134:
123:
122:
121:
119:
114:
112:
111:naphthopyrans
108:
104:
100:
96:
81:
79:
75:
65:
62:
58:
53:
50:
46:
43:, or another
42:
41:polycarbonate
38:
34:
30:
21:
1061:
1026:Porous glass
981:Safety glass
938:Porous glass
896:modification
869:
708:Wood's glass
657:
628:Fused quartz
603:Cobalt glass
557:Supercooling
495:, 2000-06-29
491:
468:. Retrieved
464:
454:
446:the original
436:
403:
399:
393:
347:
338:
330:
321:
216:
115:
95:photochromic
92:
71:
54:
33:optical lens
28:
26:
1051:Glass fiber
1016:Glass cloth
760:Preparation
736:CorningWare
618:Flint glass
613:Crown glass
566:Formulation
470:28 February
1068:Categories
1046:Windshield
880:Refraction
840:Dispersion
648:Milk glass
643:Lead glass
385:References
913:Corrosion
812:Viscosity
767:Annealing
327:Variables
303:⟶
298:−
247:⟶
242:−
233:−
199:−
179:⇀
172:−
161:−
154:↽
143:−
101:(usually
89:Mechanism
68:Invention
1079:Chromism
1031:Pre-preg
835:Achromat
578:Bioglass
573:AgInSbTe
465:UCL News
428:17808277
368:See also
342:sunglass
107:oxazines
962:Diverse
894:Surface
751:Zerodur
408:Bibcode
400:Science
379:Essilor
118:cations
78:Corning
76:at the
49:glasses
45:plastic
964:topics
827:Optics
633:GeSbTe
540:Basics
426:
362:Persol
360:, and
350:Oakley
61:halide
31:is an
746:Macor
713:ZBLAN
547:Glass
532:Glass
354:ZEISS
472:2014
424:PMID
306:AgCl
132:AgCl
109:and
416:doi
404:144
1070::
463:.
422:.
414:.
402:.
356:,
352:,
294:Cl
281:Ag
251:Ag
229:Ag
195:Cl
188:Ag
27:A
524:e
517:t
510:v
497:.
474:.
430:.
418::
410::
290:+
285:+
255:+
238:e
191:+
139:e
135:+
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
