标准红外长通滤波器，应用于顺序分类的长波通滤光片
LWP的英文全称Long Wave Pass，意为长波通或高波通。美国Andover公司推出的红外长通滤光片，又被称为长波通滤波片或红外高波通滤波器。长波通滤光片在特定波长下提供锐截止。Andover长通滤波片通常用于顺序分类，它们隔离了广泛的光谱区域，同时提供所需波段的高透射率，以及深入抑制不需要的波段。Andover长波通滤光片由光学质量的红外透射基板上的坚硬耐用的表面电介质镀膜构成，这些长波通滤波片能承受与任何高质量光学部件相关的正常清洁和处理。
高波通滤光片提供三种标准尺寸的滤波片：12.5mm、25mm和50mm直径，具有统一的中心厚度1mm，此外Andover也提供定制尺寸和形状，以及定制的光学特性。中红外高波通滤波片的工作温度涵盖-62°C至+71°C，因此具有广泛的应用。硅或锗是红外长波通滤光片的主要基底材料，其平行度小于10弧分，平均反射率小于0.1%，平均透过率>85% （from 1.05 x cut-on to 2.0 x cut-on）。中红外长通滤波片的平面度小于5 waves （at cut-on W/L），斜率小于7% (12% for 1.05µm filter)。
Andover中红外高波通滤光片的标准品：
| 型号 | 5%波长(nm) | 类型 | 尺寸(mm) | 厚度(mm) | Scratch-Dig | 通光孔径 | 平面度 |
| 1.05ILP-12.5 | 1050.0±40 | LWP | 12.5+0/-0.2 | 1.0±0.2 | 80/50 | 11.0mm-min | 5 or better at of Interest |
| 1.05ILP-25 | 1050.0±40 | LWP | 25.0 +0/-0.2 | 1.0±0.2 | 80/50 | 22.0mm-min | 5 or better at of Interest |
| 1.05ILP-50 | 1050.0±40 | LWP | 50.0 +0/-0.2 | 1.0±0.2 | 80/50 | 45mm-min | 5 or better at of Interest |
| 1.65ILP-12.5 | 1650.0±70 | LWP | 12.5 +0/-0.2 | 1.0±0.2 | 80/50 | 11.0mm-min | 5 or better at of Interest |
| 1.65ILP-25 | 1650.0±70 | LWP | 25.0 +0/-0.2 | 1.0±-0.2 | 80/50 | 22.0mm-min | 5 or better at of Interest |
| 1.65ILP-50 | 1650.0±70 | LWP | 50.0 +0/-0.2 | 1.0±0.2 | 80/50 | 45mm-min | 5 or better at of Interest |
| 2.40ILP-12.5 | 2400.0±90 | LWP | 12.5 +0/-0.2 | 1.0±0.2 | 80/50 | 11.0mm-min | 5 or better at of Interest |
| 2.40ILP-25 | 2400.0±90 | LWP | 25.0 +0/-0.2 | 1.0±0.2 | 80/50 | 22.0mm-min | 5 or better at of Interest |
| 2.40ILP-50 | 2400.0±90 | LWP | 50.0 +0/-0.2 | 1.0±0.2 | 80/50 | 45mm-min | 5 or better at of Interest |
| 3.60ILP-12.5 | 3600.0±140 | LWP | 12.5 +0/-0.2 | 1.0±0.2 | 80/50 | 11.0mm-min | 5 or better at of Interest |
| 3.60ILP-25 | 3600.0±140 | LWP | 25.0 +0/-0.2 | 1.0±0.2 | 80/50 | 22.0mm-min | 5 or better at of Interest |
| 3.60ILP-50 | 3600.0±140 | LWP | 50.0 +0/-0.2 | 1.0±0.2 | 80/50 | 45mm-min | 5 or better at of Interest |
| 4.50ILP-12.5 | 4500.0±180 | LWP | 12.5 +0/-0.2 | 1.0±0.2 | 80/50 | 11.0mm-min | 5 or better at of Interest |
| 4.50ILP-25 | 4500.0±180 | LWP | 25.0 +0/-0.2 | 1.0±0.2 | 80/50 | 22.0mm-min | 5 or better at of Interest |
| 4.50ILP-50 | 4500.0±180 | LWP | 50.0 +0/-0.2 | 1.0±0.2 | 80/50 | 45mm-min | 5 or better at of Interest |
| 6.00ILP-12.5 | 6000.0±240 | LWP | 12.5 +0/-0.2 | 1.0±0.2 | 80/50 | 11.0mm-min | 5 or better at of Interest |
| 6.00ILP-25 | 6000.0±240 | LWP | 25.0 +0/-0.2 | 1.0±0.2 | 80/50 | 22.0mm-min | 5 or better at of Interest |
| 6.00ILP-50 | 6000.0±240 | LWP | 50.0 +0/-0.2 | 1.0±0.2 | 80/50 | 45mm-min | 5 or better at of Interest |
| 7.30ILP-12.5 | 7300.0±290 | LWP | 12.5 +0/-0.2 | 1.0±0.2 | 80/50 | 11.0mm-min | 5 or better at of Interest |
| 7.30ILP-25 | 7300.0±290 | LWP | 25.0 +0/-0.2 | 1.0±0.2 | 80/50 | 22.0mm-min | 5 or better at of Interest |
| 7.30ILP-50 | 7300.0±290 | LWP | 50.0 +0/-0.2 | 1.0±0.2 | 80/50 | 45mm-min | 5 or better at of Interest |
长波通滤波片的主要特点：
- 用于分离宽光谱区域
- 由坚硬、耐用的表面涂层构成
- 有标准和定制波长可供选择
红外长通滤光片的主要应用：
- 顺序分类
- 傅里叶变换红外光谱
- 热成像
