Abstract: An electrophotographic image forming apparatus includes a first electrostatic-capacity generating portion disposed at such a position that the first electrostatic capacity generating portion contacts the developer accommodated in the developer accommodating portion. The first electrostatic capacity generates portion generating an electrostatic capacity corresponding to an amount of the developer. A second electrostatic-capacity generating portion is disposed at such a position that the second electrostatic-capacity generating portion does not contact the developer accommodated in the developer-accommodating portion. The second electrostatic capacity generating portion generates a reference electrostatic capacity.

Abstract: A process cartridge detachably mountable to an electrophotographic image forming apparatus, the process cartridge including (a) an electrophotographic photosensitive member; (b) process means actable on the electrophotographic photosensitive member; (c) a measuring electrode member having input-side and output-side electrodes having at least one juxtaposed portions, the measuring electrode member being disposed at such a position that it is contacted to a developer; (d) a reference electrode member having input-side and output-side electrodes having at least one juxtaposed portion, the reference electrode member being disposed at such a position that it is out of contact to the developer; (e) an output contact for the measuring electrode member, connected electrically to the output side electrode of the measuring electrode member; (f) an output contact for the reference electrode member, connected electrically to the output side electrode of the reference electrode member; and (g) a common input contact conne

Abstract: A semiconductor laser is caused to emit laser light continuously on a plurality of scanning lines prior to image formation in a laser printer. An electric current to be applied is controlled so that the detected light quantity from the semiconductor laser becomes equal to the desired light quantity. The light quantity detected during pulsed emission with the applied current is used as the desired light quantity for APC which is performed at a space between sheets when a non-image area is scanned. Alternatively, laser light is emitted on a plurality of lines before the start of printing when printing of multiple pages is to be performed in a laser beam printer, to perform light quantity control. Then, laser light is emitted during scanning of a nonimage area between pages, to perform light quantity control. When light quantity control is performed between sheets, a value obtained by correcting an error between the quantities of light in both types of light quantity control is set as the desired light quantity.