1. An optical pickup apparatus comprising:
a laser diode;
an objective lens made of a synthetic resin, the objective lens configured to focus laser light emitted from the laser diode to a signal recording layer of an optical disc;
a collimating lens arranged in an optical path between the laser diode and the objective lens, wherein:
the collimating lens has a radius of curvature greater than a radius of curvature of the objective lens; and
an annular diffraction grating is formed on a surface of the collimating lens farthest from the objective lens, the annular diffraction grating configured to correct chromatic aberration that occurs in response to a change in a refractive index of the objective lens with a change in wavelength of the laser light, and
a mirror arranged in the optical path between the collimating lens and the objective lens, the mirror reflecting the laser light passed through the collimating lens in a direction of the objective lens; wherein:
the collimating lens is moved in an optical axis direction of the laser light to correct for spherical aberration occurring in response to a change in temperature when performing a recording operation for the optical disc, and
the collimating lens corrects, due to the annular diffraction grating, chromatic aberration occurring when switching from the recording operation to a reproducing operation for the optical disc.
2. The optical pickup apparatus according to claim 1, wherein
the collimating lens is moved in the optical axis direction in accordance with a rotational operation of a motor.
3. The optical pickup apparatus according to claim 2, wherein
the motor is a stepping motor; and
a rotation amount of the stepping motor is set by the number of driving pulses corresponding to an amount of moving the collimating lens in the optical axis direction.
4. The optical pickup apparatus according to claim 1, wherein:
the intensity of the laser light emitted from the laser diode onto the signal recording layer of the optical disc is maintained.
5. The optical pickup apparatus according to claim 1, wherein the annular diffraction grating is formed on a surface of the collimating lens closest to the objective lens and on the surface of the collimating lens farthest from the objective lens.
6. The optical pickup apparatus according to claim 1, wherein the annular diffraction grating is formed on the surface of the collimating lens in a sawtooth shape.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method of providing a stabilizing extracapsular surgical repair for anarticulating joint between a femur and a tibia in a canine subject, comprising:
(a) obtaining a first image showing said articulating joint in a fully flexed position and obtaining a second image showing said articulating joint in a fully extended position;
(b) in said images identifying a pair of points between which to provide an extracapsular tension-carrying structure interconnecting said two bones, said pair of points being a reference point on said tibia and an isometric point on said femur, said reference and isometric points being located in said joint so as to be separated by a separation distance that is equal in both of said first and second images;
(c) locating said reference point in said tibia in said articulating joint in said subject;
(d) thereafter, locating a trial isometric point on said femur in said subject by fastening a first marking element at said reference point and holding a second marking element in said second locating portion of said device at said separation distance with said articulating joint in a first one of a fully extended position and a fully flexed position;
(e) moving said articulating joint to the other one of said fully extended and fully flexed positions and observing whether said reference point and said trial isometric point are then separated by said separation distance; and adjusting the position of said second locating member with respect to said trial isometric point until an isometric point is located on said second one of said bones of said articulating joint; and
(f) surgically attaching a tension-bearing repair structure to said bones so that it is attached at said reference and said isometric points so as to provide tension-bearing structure extending between respectively said reference point and said isometric point as thus located in said joint.
2. The method of claim 1, including the further step of using a scale and thereby verifying that said separation distance between said reference point and said isometric point is equal when said joint is flexed and when it is extended.