BP250
Broadband UV Bandpass Filter

The BP250 filter is a very broadband UV filter for deep-UV imaging. It is expensive, offered in a limited number of sizes, and not intended for use with standard CCD/CMOS cameras.

To take advantage of this filter, essentially a more expensive camera or viewer with deep-UV sensitivity and a more expensive objective lens designed specifically for UV imaging are required.

This filter has peak transmission of approximately 40% around 235nm, and transmission gradually slopes downward to less than 0.3% at 405nm.

This one filter and the polarizers are the only ones we make that are not hard coated and/or single substrate. The BP250 is made with two pieces of specially coated glass cemented together with the soft coating faces to the inside for protection. Due to the unique coating(s) to achieve the deep UV transmission only, the BP250 is also the most expensive filter we offer. Costly as it is, it's the only filter that does with the BP250 does.

Download Excel Spreadsheet with data and curve for this filter.

Examples of filter effectiveness.

Standard Threaded Mounts:
We offer standard filter sizes from stock – 22.5mm to 62mm – for same- or next-day shipping. Larger filters – 67mm to 105mm – are made to order and are normally not returnable.

Click here for PDF drawing of standard mounts

Slip Mounts:
If your lens does not have threads for mounting a filter, Slip Mount adapters are available. Slip Mounts can attach a regular filter to a lens or attach a very large filter to accommodate a wide angle lens. Please call to order Slip Mount adapters.

C-Mounts:
3mm thick threaded mount for adding a filter between lens and camera
Click here for PDF drawing of c-mounts

Transmission chart (typical)
Passes 290-380nm
Reflects 390-1200nm

1100
1090
1080
1070
1060
1050
1040
1030
1020
1010

1000
990
980
970
960
950
940
930
920
910

900
890
880
870
860
850
840
830
820
810

800
790
780
770
760
750
740
730
720
710

700
690
680
670
660

0.00
0.00
0.11
0.07
0.01
0.15
0.00
0.02
0.01
0.05

0.02
0.05
0.06
0.03
0.00
0.00
0.10
0.00
0.04
0.14

0.00
0.02
0.00
0.04
0.02
0.01
0.01
0.02
0.00
0.01

0.02
0.01
0.00
0.02
0.00
0.03
0.01
0.00
0.00
0.00

0.01
0.02
0.00
0.00
0.00

650
640
630
620
610
600
590
580
570
560

550
540
530
520
510
500
490
480
470
460

450
440
430
420
410
400
390
380
370
360

350
340
330
320
310
300
290
280
270
260

250
240
230
220
210

0.00
0.00
0.02
0.02
0.02
0.02
0.02
0.02
0.03
0.02

0.03
0.05
0.03
0.04
0.05
0.06
0.06
0.07
0.10
0.11

0.13
0.16
0.19
0.23
0.29
0.36
0.46
0.58
0.76
1.00

1.33
1.81
2.46
3.44
4.87
7.00
10.11
14.66
20.73
27.93

34.62
38.70
38.85
34.76
27.04