Provided is an additive for lubricating oils which enhances frictional characteristics of slide parts in internal combustion engines and driving system transmission engines and which exhibit an excellent fuel consumption reducing effect. A sensor is connected to the arm supporting member, andor a resilient member is interconnected between the arm supporting member and either the leg supporting member or the frame. An error is detected in the first bit sequence, and the address associated with the bit sequence is compared to addresses stored in an address database of a content addressable memory component to determine if there is a match. By utilizing this correction optical system, it becomes possible to reduce the size of the focal point detection apparatus while assuring a large focal point detection area.