What is the difference between a black light, a Woods Lamp, and a pet urine-detection light?

(Aren't they all exactly the same?) I was just wondering why I should pay $40 for one of the fancy "Pet Urine Detection" lights at Petco or PetSmart when I could probably just go down to my local head shop and get a plain ol' black light for around $10. Someone please enlighten me! -- Thanks