1. Group Designation

Optical glasses are classified into groups on the basis of refractive indexes (n_d) ,and Abbe-numbers (ν_d).

Table 1
Group/Designation Correspondence
provides an easy reference to identify "equivalent" glass types between HOYA and SCHOTT

Group Name	HOYA	SCHOTT	Group Name	HOYA	SCHOTT
Fluor Crown	FC	FK	Flint	F	F
Dense Fluor Crown	FCD	FK	Dense Barium Flint	BAFD	BaSF
Dense Phosphate Crown	PCD	PSK	Dense Flint	FD	SF
Boro Silicate Crown	BSC	BK	Special Dense Flint	FDS	SF
Crown	C	K	Fluor Flint	FF	TiF
Barium Crown	BAC	BaK	Light Lanthanum Flint	LAFL	LaF
Dense Barium Crown	BACD	SK	Lanthanum Flint	LAF	LaF
Extra Dense Barium Crown	BACED	SSK	Niobium Flint	NBF	LaF
Light Lanthanum Crown	LACL	LaK	Tantalum Flint	TAF	LaF, LaSF
Lanthanum Crown	LAC	LaK	Dense Niobium Flint	NBFD	LaF, LaSF
Tantalum Crown	TAC	LaK	Dense Tantalum Flint	TAFD	LaSF
Crown Flint	CF	KF	Abnormal Dispersion Crown	ADC	-
Extra Light Flint	FEL	LLF	Abnormal Dispersion Flint	ADF	KzFS
Barium Flint	BAF	BaF	Low Birefringence Crown	LBC	-
Light Flint	FL	LF	-	-	-

 

1) Designation of Glass Lenses Pressed Blanks and Glass Polished Lenses.
All of the optical glasses described here are environment-friendly and composed of materials free of lead and arsenic.

Direct Pressed Blanks (DP)	Re-heat Pressed Blanks (RP)
Rolled and Sliced Blanks (RS)
	<Example Name> : FCD 1 : FDS 90 : E-FDS 1

2) Designation of Molded Glass for GMO products.
These are a series of low-melting-point glasses used exclusively for GMO products. They are designated by the prefix 'M-' .

Glass molded lenses (GMO)

<Example Name> Glass molded lenses (GMO) " M-TAFD305 "

3) Designation of Preform of Molded Glass for GMO products.
These are a series of low-softening-point glasses used exclusively for GMO products.They are designated by the prefix 'MP-' or'MC-'. Preforms of less than 5000mg in weight are offered as the hot processing perform are desingnated by the prefix 'MP-'.
Preforms of over 5000mg in weight are offered as the cold processing preform are desingnated by the prefix 'MC-'.

Preform (PF)

<Example Name> Preforms for Precision Molding (Precision Gob) : MP-TAFD305 Preforms for Precision Molding (Polishing Surface) : MC-TAFD305

2. Code

In addition to our glass type designation, a six-digit code number is used in this catalog. The first three digits indicate the refractixe index (n_d) after the decimal point, and the last three digits represent the Abbe-number (ν_d).
In FCD1, for example, the n_d is 1.49700, and the ν_d is 81.61, which we indicate as 497-816.