Ricoh Company, Ltd.

Kenta Watase

Koji Hirakura

Yasuo Sawada

Takeshi Iijima

Takahiko Kitamura

An optical information recording medium includes a ROM region in which information has been recorded in the form of pits in a substrate, and from which the recorded information can be reproduced upon application of a laser beam thereto, and a recording region in which information can be recorded in the form of pits from which the recorded information can be reproduced upon application of a laser beam thereto, with the improvement wherein a reflective layer is provided in a ROM region portion of the substrate in the ROM region, and a recording layer is overlaid on both the reflective layer in the ROM region portion and a recording portion of the substrate in the recording region.

Optical information recording medium

A toner concentration control system for use in electrophotographic copying machines or the like, wherein light from a single light source is simultaneously detected by two photosensors, or by two sensing portions of a single photosensor, the light striking one of the photosensors (or portions) directly and the other after being reflected from developer comprising toner and carrier particles as the developer passes a viewing window in a chute provided for the transport thereof within the copying machine, the intensity of the reflected light being inversely proportional to the concentration of toner in the developer, whereby, by comparison of the output of the photosensors (or portions) by conventional means, the concentration of toner in the developer can be determined and adjusted, the photosensors (or portions) having been carefully selected as a pair of their essentially identical characteristics and response to ambient conditions so that, for example, their parallel deterioration with time or their identical response to changes in temperature will not adversely affect the accuracy of the toner-concentration determination, the portion of the embodiment comprising the light paths, the photosensors, the light source and the external surface of the viewing window being completely sealed from the remainder of the interior of the copying machine, thereby eliminating the adverse affects on measurement and long-term reliability of inevitable airborne particles of developer.

Toner concentration control apparatus

A toner concentration control apparatus of the type for allowing developer to pass through a chute, which is capable of detecting stopping of the flow of the developer in the chute, clogging of the chute with the developer, or coating of a viewing window formed in the chute with the developer, and upon occurrence of such abnormalities, minimizing the trouble therefrom in the operation of the copying machine, in which light from a single light source is simultaneously detected by two photosensors, the light striking one of the photosensors directly and the other after being reflected from the developer comprising toner and carrier particles as the developer passes a viewing window in the chute provided for the detection of the toner concentration within the copying machine, and the output of the photosensors is compared with each other and the concentration of toner in the developer can be determined and adjusted by the comparison value. In addition, the output of the photosensor which receives the light reflected from the developer contains an A.C. component signal which indicates the flow of the developer along the inside of the viewing window, and a D.C. component signal which corresponds to the concentration of toner in the developer, and, by detecting the presence or absence of the A.C. component signal, abnormalities in the flow of developer are detected.

A powdered developer (26) comprising carrier and toner particles is caused to flow by gravity downwardly through a passageway (71). A transparent electrode (62) is disposed in the passageway (71). A light source (64) and photosensor (66) are arranged on opposite sides of the electrode (62) for sensing an amount of attracted toner. The electrode (62) is first de-energized and cleaned by aprtially restricting the passageway (71) below the electrode (62) and allowing developer (26) to accumulate in the passageway (71) from the restriction upwardly past the electrode (62) while a restricted amount of developer (26) flows downwardly through the restriction. Then, the restriction is removed and the passageway (71) blocked above the electrode (62), allowing the accumulated developer (26) to flow downwardly past the electrode (62). Then, the passageway (71) is completely unblocked and the electrode (62) energized with an electric potential causing toner to be attracted thereto. After a predetermined length of time the passageway (71 ) above the electrode (62) is blocked and the output of the photosensor (66) indicates the amount of toner attracted to the electrode (62) and thereby the developing ability of the developer (26). The output of the photosensor (66) after cleaning the electrode (62) may be compared with the final output to provide a reference valve which is compensated for variables such as electrode contamination, electric potential variation and the like.

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Tokyo, Japan

Kenta Watase