Abstract: A zoom lens is equipped with: a first lens group having an overall negative refractive power and a second lens group having an overall positive refractive power in sequence from the object side to the image plane side. Zoom magnification is changed from a wide-angle end to a telephoto end by moving the first lens group to the image plane side and then reversing the motion to the object side while the second lens group is moved to the object side. The condition (1) 0.90<=(DG1+DG2)/fw<=2.30 and the condition (2) 0.5<=|fG1|/fG2<=1.6 are met, where DG1 is the thickness of the first lens group; DG2 is the thickness of the second lens group; fw is the focal length of the lens system at the wide-angle and; fG1 is the focal length of the first lens group; and fG2 is the focal length of the second lens group.

Abstract: A zoom lens is equipped with: a first lens group having an overall negative refractive power and a second lens group having an overall positive refractive power in sequence from the object side to the image plane side. Zoom magnification is changed from a wide-angle end to a telephoto end by moving the first lens group to the image plane side and then reversing the motion to the object side while the second lens group is moved to the object side. The condition (1) 0.90<=(DG1+DG2)/fw<=2.30 and the condition (2) 0.5<=|fG1|/fG2<=1.6 are met, where DG1 is the thickness of the first lens group; DG2 is the thickness of the second lens group; fw is the focal length of the lens system at the wide-angle and; fG1 is the focal length of the first lens group; and fG2 is the focal length of the second lens group.

Abstract: The present invention includes, from the object side to the image plane side, an aperture stop with a predetermined diameter, a first lens with a positive refractive power and a bi-convex shape with convex surfaces facing the object side and the image plane side, a second lens being formed as a meniscus shape with a concave surface facing the object side having a negative refractive power, and a third lens being formed as a meniscus shape with a convex surface facing the object side having a positive refractive power. By having a positive refractive power for the first lens and third lens and a negative refractive power for the second lens, a suitable back focus can be maintained while reducing the total length of the lens system. The imaging lens is thin and compact and has superior optical properties suited for mobile cameras mounted in portable telephones and PDAs.

Abstract: The present invention includes, from the object side to the image plane side, an aperture stop with a predetermined diameter, a first lens with a positive refractive power and a bi-convex shape with convex surfaces facing the object side and the image plane side, a second lens being formed as a meniscus shape with a concave surface facing the object side having a negative refractive power, and a third lens being formed as a meniscus shape with a convex surface facing the object side having a positive refractive power. By having a positive refractive power for the first lens and third lens and a negative refractive power for the second lens, a suitable back focus can be maintained while reducing the total length of the lens system. The imaging lens is thin and compact and has superior optical properties suited for mobile cameras mounted in portable telephones and PDAs.

Abstract: A musical instrument produces nineteen tones in each octave, and the nineteen tones have respective fundamental frequencies regulated to a geometrical series of .sup.19 .sqroot.2 so as to be highly harmonized without difficult in performance.