Abstract: A logarithmic amplifier comprises an amplifier provided with a feedback circuit, a logarithmic conversion device in the feedback circuit, an oscillation preventing circuit which is provided with a capacitor connected in parallel with the logarithmic conversion device, and a control circuit. The control circuit controls the oscillation preventing circuit in accordance with the current fed into the logarithmic amplifier, so that the amount of certain components in the output from the amplifier, which components are fed back to an input terminal of the amplifier through the oscillation preventing circuit, decreases as the current fed into the logarithmic amplifier becomes smaller. An image read-out apparatus comprises a photoelectric detector which detects light from a recording medium, which light is emitted by the recording medium when it is scanned, and the logarithmic amplifier into which the output current generated by the photoelectric detector is fed. An image having good sharpness is thereby obtained.

Abstract: Scanning and synchronizing light beams are deflected by a light deflector. The scanning light beam is used to scan an object surface, whereas the synchronizing light beam is applied to a grid for generating a synchronizing signal to detect the scanning position of the scanning light beam on the object surface. The grid includes a starting point control area, corresponding to a main scanning cycle starting position on the object surface, for modulating the synchronizing light beam applied to the grid so that light having passed through the starting point control area will have a different phase than the light from the other portion of the grid.

Abstract: A light beam scanning apparatus scans an object such as a stimulable phosphor sheet by applying a light beam deflected in a main scanning direction to the object while moving the object in an auxiliary scanning direction substantially normal to the main scanning direction. The light beam scanning apparatus includes first and second light detectors such as photodiodes juxtaposed in the main scanning direction and having respective light detecting surfaces extending in the auxiliary scanning direction. The first and second light detectors produce respective output signals at a predetermined ratio when the light beam for scanning the object in the main scanning direction is in a reference main scanning position, and produce respective output signals at a ratio varied from the predetermined ratio when the light beam is deviated from the reference main scanning positon.

Abstract: An image read-out apparatus for exposing a recording medium carrying an image stored therein to a light beam, and photoelectrically detecting light carrying the image information obtained from the recording medium by use of a photomultiplier comprises a comparator for comparing an output current signal of the photomultiplier with a predetermined reference value, and a voltage detector for detecting the voltage generated at a bleeder resistor of the photomultiplier. The apparatus also comprises a selection circuit for receiving the output current signal of the photomultiplier, a voltage signal detected by the voltage detector, and an output of the comparator, selecting the output current signal of the photomultiplier when the output current signal of the photomultiplier is equal to or lower than the reference value, and selecting the voltage signal when the output current signal of the photomultiplier is higher than the reference value.

Abstract: A method of detecting stored radiation energy level on a stimulable phosphor sheet comprises the steps of storing a predetermined level of radiation energy on a stimulable phosphor sheet for test before image read-out is carried out by scanning a stimulable phosphor sheet carrying a radiation image stored thereon with stimulating rays which cause the stimulable phosphor sheet to emit light and detecting the emitted light by a photomultiplier, carrying out the scanning and light detection for the stimulable phosphor sheet for test, and detecting a voltage Vo generated at a bleeder resistor of the photomultiplier at each scanning position. In the course of carrying out image read-out from the stimulable phosphor sheet carrying the radiation image stored thereon, a voltage V generated at the bleeder resistor is detected at each scanning position, and the voltage V is compared with the voltage Vo. Based on the value V-Vo, a radiation energy level exceeding the predetermined level is detected.

Abstract: In a radiation image recording and reproducing system using a stimulable phosphor sheet, a voltage generated at a bleeder resistor of a photomultiplier for conducting image read-out is detected at the step of radiation image read-out at least for the stimulable phosphor sheet or a portion thereof where the level of X-ray exposure amount is higher than a predetermined level, and the exposure amount of erasing light is controlled on the basis of the detected voltage. Or, the erasing light exposure amount is controlled on the basis of an output current of the photomultiplier when the output current is equal to or smaller than a predetermined value when is smaller than a saturated value of the output current, and the bleeder resistor voltage of the photomultiplier is detected and the erasing light exposure amount is controlled on the basis of the detected voltage when the output current of the photomultiplier is larger than the predetermined value.

Abstract: A method of coalescing two or more laser beams employs an optical merging element such as a polarization beam splitter to make the laser beams substantially merged into a single laser beam of multiplied power. In the merged laser beam, however, the original laser beams cannot easily be perfectly aligned with each other. In order to have the laser beams perfectly mingled or coalesced at the position where they are focused on an object to be processed or an original to be read out or a recording medium, the original laser beams substantially merged into a single laser beam are collimated so that the collimated laser beams may be directed to the same focusing position on the object.

Abstract: In a radiation image read-out system, a stimulable phosphor sheet carrying a radiation image stored therein is two-dimensionally scanned with stimulating rays, with the main scanning being effected by use of a multifaceted mirror having a plurality of deflecting surfaces. Light emitted by the stimulable phosphor sheet upon exposure to the stimulating rays is detected and converted into an electric image signal. When any of the deflecting surfaces is inclined from its predetermined position, the electric image signal obtained from the scan line drawn by the inclined deflecting surface becomes incorrect. The electric image signal obtained from the scan line drawn by the inclined deflecting surface is corrected by use of a correction coefficient which is predetermined for each deflecting surface according to the amount of inclination from the predetermined position thereof.

Abstract: A laser apparatus comprises a laser tube supported by a plurality of mounts on a supporting plate, a case housing the laser tube, temperature sensors positioned on the mounts or the supporting plate near the mounts or the laser tube, and a plurality of fans positioned on a wall of the case. The fans are positioned to generate air streams passing over the respective sections the temperatures of which are detected by the temperature sensors and operated in accordance with electric outputs of the temperature sensors, thereby maintaining the temperatures at the respective sections at a predetermined level.