1. Light which enters the light trap (140) is absorbed.

2. The light trap may be coated or treated to increase absorption of visible and infrared radiation.

3. The light trap absorbs all the light when no test piece is inserted in the light beam.

4. The light trap absorbs all the light when no test piece is inserted in the light beam

5. The light trap shall absorb all the light when no test piece is inserted in the light beam.

6. The light trap shall absorb all the light when no test piece is inserted in the light beam

7. In the normally open embodiment, the blade combines with a light absorptive slotless backup plate (80) to define the light trap.

8. The normally closed embodiment includes a light absorptive tongue (54) between the poles (38 and 40) which combines with the reflective blade to define a light trap.