Abstract: An AC driving signal of a frequency in the vicinity of the resonance frequency of a piezoelectric transformer is generated by a variable oscillation circuit and the waveform of the output signal of the variable oscillation circuit is shaped so as to be substantially sinusoidal by a waveform shaping circuit and the output of the waveform shaping circuit is subjected by a driving circuit to current amplification or voltage amplification so as to be amplified to a level sufficient for driving the piezoelectric transformer and the output of the driving circuit is subjected to current limitation, and then input to the piezoelectric transformer and the output signal of the transformer is applied to a cold cathode fluorescent lamp so that the cold cathode fluorescent lamp is lit and even if the impedance of the cold cathode fluorescent lamp decreases, the piezoelectric transformer cannot supply a large current.

Abstract: In a distance measuring apparatus in accordance with the present invention, a light beam of a wide solid angle is projected on a photographic object by means of a strobo light source, and reflected rays are received by a photoelectric device array which has a predetermined number of photoelectric devices each with narrow directivity which are comparable to solid angles necessary to see the object from the photoelectric devices disposed with their optical axes at predetermined angular pitches. When the output of a photoelectric device, which is issuing maximum amplitude output, is selected by means of a maximum value detector circuit, and a distance signal is discriminated from background noises such as sun light or electric illumination light by passing through a differentiating circuit, and then being processed by a function circuit and fed to a lens driving system or indicator.