Patent attributes
A spirit level is provided that incorporates an illuminated optical indicator of the level orientation. The spirit level housing is at least partially translucent. At least one light-emitting diode (LED) is disposed within the housing for illuminating the translucent portions of the housing. Vertical, horizontal and angular orientation indication assemblies are provided including a tubular curved glass vial having a constant inner diameter at a viewing point and having a slight upward curve and incompletely filled with a liquid to create a bubble. An angle sensing circuit electrically connected to a battery controls the LED's to illuminate in a first color in a vertical orientation and in a second color in a horizontal orientation. Gradual changing of the color and/or the intensity of the light occurs during transition of the orientation between the vertical orientation and the horizontal orientation.