Abstract: An illuminating device according to the present invention comprises a first reflector for irradiating forward light beams from a light source, a second reflector that has an aperture and is disposed in front of the first reflector so as to reflect toward the light source the light beams from the first reflector to condense the light beams, a third reflector disposed so as to make the light beams condensed by the second reflector exit through the aperture, and a reflector moving means that moves the second reflector or the third reflector along an optical axis.

Abstract: An illuminating device according to the present invention comprises a first reflector for irradiating forward light beams from a light source, a second reflector that has an aperture and is disposed in front of the first reflector so as to reflect toward the light source the light beams from the first reflector to condense the light beams, a third reflector disposed so as to make the light beams condensed by the second reflector exit through the aperture, and a reflector moving means that moves the second reflector or the third reflector along an optical axis.

Abstract: Lepidocrocite suitable for obtaining excellent magnetic powders and magnetic recording media is manufactured by oxidizing an aqueous suspension of ferrous hydroxide obtained from a ferrous salt and an alkali by blowing an amount of an oxygen-containing gas into the suspension, in which the blowing amount of the oxygen-containing gas is appropriately controlled in three steps, according to three steps of the oxidation reaction of the ferrous hydroxide. In a preferred embodiment, average oxygen absorption rates in the three oxidization steps are defined and the blowing of the oxygen-containing gas is controlled thereby.