Lighting:

In order to specifically measure the amount of light entering the eye, personal circadian light meter called the Daysimeter has been developed. This is the first device created to accurately measure and characterize light (intensity, spectrum, timing, and duration) entering the eye that affects the human body's clock.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". A Daysimeter what type of personal meter?
circadian light meter