Viewing a hologram depends on which type it is. Reflection holograms require the use of a bright spot light and adjusting the viewing angle until the image is found. Transmission holograms require using the laser that was used to create the holograms and looking through them to see the image.
When a hologram is reconstructed so that it can be permanently recorded, one of two methods can be used. Reflection holography uses a laser that is striking the object that is the subject of the hologram and the recording medium from opposite sides of the recording medium. Transmission holography uses a laser that is striking the object and the recording medium from the same side of the medium.