Abstract: An apparatus for monitoring optical equipment in an optical circuit is disclosed in which the apparatus may include an optical device situated to receive an optical input signal and to reflect a portion of the energy of the received optical input signal, thereby providing a reflected input signal; a first photodiode located along a path of the reflected input signal, and operable to receive optical energy from the reflected optical input signal and from ambient optical power; a second photodiode located substantially outside the reflection path of the optical input signal; and means for calculating a magnitude of a power level of the optical input signal from values of outputs from the first and second photodiodes.

Abstract: The toner for developing an electrostatic latent images of the present invention, comprising colored resin particles containing at least a binder resin and a colorant wherein said colored resin particles have a volume average particle diameter (Dv) in the range from 4 to 10 ?m and an average circularity in the range from 0.930 to 0.995 and, a zeta potential (E1) of the toner after laid still under a condition at a temperature of 23° C. and a humidity of 50% for one day and night is in the range from ?50 to ?10 mV and a difference is less than 5 mV between a zeta potential (E2) of the toner after laid still under an environment of temperature of 50° C. and humidity of 80% for two weeks and El. According to the present invention, there are provided toners for developing electrostatic images, which forms images without losing quality due to environmental changes and also has excellent storage stability and flowability.