1st generation is currently the most popular type of night vision in the world. Utilizing the basic principles described in detail in our guide, a 1st generation unit will amplify the existing light several thousand times letting you clearly see in the dark. These units provide a bright and sharp image at a low cost, which is perfect, whether you are boating, observing wildlife, or providing security for your home. You may notice the following when you are looking through a 1st Gen. unit. A slight high-pitched whine when the unit is on. The image you see may be slightly blurry around the edges. This is known as Geometric Distortion. When you turn a 1st Gen. unit off it may glow green for some time. These are inherent characteristics of a 1st Gen. unit and are normal.