1. An optical pickup comprising:
a laser light source for emitting first laser light having a first wavelength as a center wavelength, second laser light having a second wavelength longer than the first wavelength as a center wavelength, and third laser light having a third wavelength longer than the second wavelength as a center wavelength;
an objective lens for focusing the first laser light, the second laser light, and the third laser light onto the optical disc;
a servo mechanism for changing the position of the objective lens;
an optical element disposed on a light path of laser light reflected from an optical disc onto which one of the first laser light, the second laser light, and the third laser light is directed, the optical element astigmatizing the first to third laser lights;
a diffractive optical element for causing one specific laser light or two specific laser lights of the first to third laser lights astigmatized by the optical element to diffract in specific diffraction angles; and
a photodetector for detecting the first diffracted light as a diffracted light of the first laser light that exits the diffractive optical element, the second diffracted light as a diffracted light of the second laser light that exits the diffractive optical element, and the third diffracted light as a diffracted light of the third laser light that exits the diffractive optical element,
wherein the diffractive optical element has:
a first diffractive region and a second diffractive region which are different to each other and are formed by dividing the diffractive optical element by a straight line intersecting at an optical axis of the diffractive optical element; and
the first diffractive region and the second diffractive region are structured so that the +1-order light output from the first diffractive region when laser light is incident on the first diffractive region propagates in a different direction from the +1-order light output from the second diffractive region when the same laser light is incident on the second diffractive region, and the \u22121-order light output from the first diffractive region when laser light is incident on the first diffractive region propagates in a different direction from the \u22121-order light output from the second diffractive region when the same laser light is incident on the second diffractive region.
2. The optical pickup of claim 1, wherein
the diffractive optical element outputs, when the first laser light is incident, the first diffracted light, outputs, when the second laser light is incident, the second diffracted light, and outputs, when the third laser light is incident, the third diffracted light, and
the diffractive optical element is structured so that 0-order light is a maximal component of each of the first diffracted light and the second diffracted light and +1-order light or \u22121-order light is a maximal component of the third diffracted light, or so that 0-order light is a maximal component of each of the second diffracted light and the third diffracted light and +1-order light or \u22121-order light is a maximal component of the first diffracted light.
3. The optical pickup of claim 1, wherein:
the first laser light is blue laser light;
the second laser light is red laser light; and
the third laser light is infrared laser light.
4. The optical pickup of claim 1, wherein:
the first wavelength is 0.405 \u03bcm;
the second wavelength is 0.65 \u03bcm; and
the third wavelength is 0.78 \u03bcm.
5. The optical pickup of claim 1, wherein:
the diffractive optical element is divided into four diffraction regions by two straight lines intersecting at the optical axis of the optical means;
said first diffractive region consists of two of the four diffractive regions, disposed in symmetrical positions with respect to said optical axis; and
said second diffractive region consists of another two of the four diffractive regions.
6. The optical pickup of claim 1, wherein the optical means has an optical member with a plurality of stepped diffraction grating grooves.
7. The optical pickup of claim 6, wherein the diffraction grating grooves are annular grooves centered on the optical axis of the optical means.
8. The optical pickup of claim 6, wherein the diffraction grating grooves have widths that narrow with increasing distance from the optical axis of the optical means.
9. The optical pickup of claim 6, wherein the diffraction grating grooves have widths and depths selected so that the 0-order light is the maximal component of each of the first diffracted light and the second diffracted light and the +1-order light or the \u22121-order light is the maximal component of the third diffracted light, or so that the 0-order light is the maximal component of each of the second diffracted light and the third diffracted light and the +1-order light or the \u22121-order light is the maximal component of the first diffracted light.
10. The optical pickup of claim 1, wherein the optical means has an optical member with a plurality of blazed diffraction grating grooves.
11. The optical pickup of claim 1, further comprising:
a circuit for sending a signal based on an output of the photodetector to the servo mechanism;
wherein the servo mechanism changes the position of the objective lens on the basis of the output of the photodetector.
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 bobbin for a sewing machine, which is rotatably disposed in a rotary shuttle device of the sewing machine to supply an under thread when performing a sewing operation, comprising a winding shaft 10 which is separatably inserted onto a fixing shaft of the rotary shuttle device and on which the under thread is substantially wound, a first flange 12 which is integrally formed at one end of the winding shaft 10, a second flange 14 which is integrally formed at the other end of the winding shaft 10, and a partition flange 16 for forming a first winding portion 18 between the first flange 12 and the partition flange 16 and forming a second winding portion 20 between the second flange 14 and the partition flange 16, characterized in that
a plurality of trough portions 22 and ridge portions 24 are alternately formed at an entire outer circumference of the partition flange 16, each of the trough portions 22 and the ridge portions 24 has the same gradient each other, and a side portion 22a is formed at both sides of each trough portion 22 to prevent the under thread from being previously slipped.
2. The bobbin of claim 1, wherein the partition flange 16 is formed with 6 to 12 trough portions 22 and ridge portions 24.
3. A bobbin for a sewing machine, which is rotatably disposed in a rotary shuttle device of the sewing machine to supply an under thread when performing a sewing operation, comprising a winding shaft 10 which is separatably inserted onto a fixing shaft of the rotary shuttle device and on which the under thread is substantially wound, a first flange 12 which is integrally formed at one end of the winding shaft 10, a second flange 14 which is integrally formed at the other end of the winding shaft 10, and a partition flange 26 for forming a first winding portion 18 between the first flange 12 and the partition flange 26 and forming a second winding portion 20 between the second flange 14 and the partition flange 26, characterized in that
a plurality of saw-toothed protrusions 34 is formed at an entire outer circumference of the partition flange 26, and the protrusions 34 has a linear sidewall 32a that is orientated in a radial direction of the partition flange 26.