Abstract: A distance-measuring method includes acquiring a first curvature angle of a curved portion in a first state in which an endoscope is inserted into a body cavity and captures an observation target, a second curvature angle of the curved portion in a second state in which an insertion direction of the endoscope is changed with a position of a trocar as a pivot point while capturing the same observation target as in the first state, a change amount in an insertion angle due to a change in the insertion direction, and an insertion amount of the endoscope from the pivot point of the trocar to the curved portion, so as to calculate a distance from a distal end portion of the endoscope to the observation target in a state in which the endoscope is inserted into the body cavity via the trocar.

Abstract: Test signals are recorded on a prescribed area in an optical disc. The prescribed area is scanned by a laser beam while the power of the laser beam is changed among different DC erasing values. The different DC erasing values are assigned to the recorded test signals, respectively. The recorded test signals are reproduced from the prescribed area to obtain reproduced signals. Parameter values of the respective reproduced signals are detected. The detected parameter values correspond to the different DC erasing values, respectively. Among the detected parameter values, a detected parameter value is decided which matches a target. One corresponding to the decided parameter value is selected from the different DC erasing values. A prescribed coefficient and the selected DC erasing value are multiplied to calculate an optimum level of an erasing power of the laser beam.

Abstract: Reflected light caused by reflection of a laser beam at a first layer of an optical disc is converted into a main signal. Reflected light caused by reflection of the laser beam at a second layer of the optical disc is converted into a sub signal. An address of a currently-accessed position in the first layer is detected from the main signal. A reference address in the first layer corresponds to a boundary between a signal recorded area and a signal unrecorded area in the second layer. A specified address in the first layer corresponds to a position radially separated from the position at the reference address by an allowable range. A misalignment between tracks on the first and second layers is concluded to be within the allowable range in cases where the sub signal substantially takes a reference level when the detected address reaches the specified address.

Abstract: Reflected light caused by reflection of a laser beam at a first layer of an optical disc is converted into a main signal. Reflected light caused by reflection of the laser beam at a second layer of the optical disc is converted into a sub signal. An address of a currently-accessed position in the first layer is detected from the main signal. A reference address in the first layer corresponds to a boundary between a signal recorded area and a signal unrecorded area in the second layer. A specified address in the first layer corresponds to a position radially separated from the position at the reference address by an allowable range. A misalignment between tracks on the first and second layers is concluded to be within the allowable range in cases where the sub signal substantially takes a reference level when the detected address reaches the specified address.

Abstract: Test signals are recorded on a prescribed area in an optical disc. The prescribed area is scanned by a laser beam while the power of the laser beam is changed among different DC erasing values. The different DC erasing values are assigned to the recorded test signals, respectively. The recorded test signals are reproduced from the prescribed area to obtain reproduced signals. Parameter values of the respective reproduced signals are detected. The detected parameter values correspond to the different DC erasing values, respectively. Among the detected parameter values, a detected parameter value is decided which matches a target. One corresponding to the decided parameter value is selected from the different DC erasing values. A prescribed coefficient and the selected DC erasing value are multiplied to calculate an optimum level of an erasing power of the laser beam.

Abstract: User data is recorded on a data area in first one of recording layers in a rewritable optical disc through the use of a laser beam having a power changing among different values including a first erasing power value. Test signals are recorded and reproduced on and from a section in a trial write area in the first recording layer. A region in the first recording layer is illuminated with the laser beam having a power equal to a second erasing power value to be subjected to signal erasure before the test signals are recorded and reproduced on and from the section in the trial write area. The region includes the section in the trial write area. The second erasing power value is equal to the first erasing power value multiplied by a coefficient in the range of 1.5 to 3.

Abstract: An optical disk apparatus capable of automatically setting a pickup lens suitable for an optional optical disk selected from a plurality of optical disks having different thicknesses. Current flowing through an actuator is detected with a detector circuit, A/D converted, and supplied to a controller. The controller detects the in-focus positions at the surface and reflection film of an optical disk in accordance with an FOK signal and an FZC signal, calculates the current values flowing through the actuator at the in-focus positions, and judges the thickness of the optical disk in accordance with a difference between the current values.

Abstract: A laser driver circuit of an optical disk recording/reproducing apparatus includes a laser output detecting unit for detecting a digital average value of a laser output, first and second memories for storing a digital value of a current to be supplied to a laser diode, first and second D/A converters for converting the digital values stored in the first and second memories into analog values, and a current supplying unit for supplying a current proportional to an output of the first D/A converter or a current proportional to a sum of outputs of the first and second D/A converters to the laser diode.