The Active Treatment Phase will be 6 weeks or until target plaque has cleared, whichever comes first. During the Active Treatment Phase, the plaque randomized to Arm B will receive the active occlusive hydrogel patch and will be changed every 5 days or less as needed. During the Active Treatment Phase, the plaque randomized to Arm A will receive the window patch and replaced as needed. The light will be applied to the target plaque assigned to Arm B every day with the hydrogel patch in place. The subject will return to the clinic every two weeks (Visit 3, 4 and 5) for assessments. Subjects who terminate early will be asked to complete all Week 6/ET assessments prior to commencement of any alternative therapy for psoriasis (if possible). Subjects who discontinue from the study during the Active Treatment Phase may be replaced and only will be followed if an AE is present.