1. A zoom lens, in order from an object side, comprising:
a first lens group having positive refractive power;
a second lens group having negative refractive power;
a third lens group having positive refractive power;
a fourth lens group having positive refractive power; and
a fifth lens group having negative refractive power;
wherein the second lens group, the fourth lens group, and the fifth lens group are relatively moved with each other, for zooming between a wide-angle end and a telephoto end.
2. The zoom lens as recited in claim 1, wherein the zoom lens satisfies the following condition: 4.0<ftfw<6.0,
wherein, fw is a focal length of the zoom lens at the wide-angle end, and ft is a focal length of the zoom lens at the telephoto end.
3. The zoom lens as recited in claim 1, wherein the zoom lens satisfies the following condition: 2.0<|fG1fG2|<4.0,
wherein, fG1 is a focal length of the first lens group, and fG2 is a focal length of the second lens group.
4. The zoom lens as recited in claim 1, wherein the second lens group, the fourth lens group and the fifth lens group are relatively moved toward the third lens group, so that the zoom lens focuses from the wide-angle end to the telephoto end.
5. The zoom lens as recited in claim 1, wherein the first lens group, the second lens group, the third lens group and the fifth lens group respectively comprise at least one aspheric lens or free-form lens.
6. The zoom lens as recited in claim 1, wherein the first lens group, the second lens group, the third lens group and the fifth lens group respectively comprise at least one plastic lens.
7. The zoom lens as recited in claim 1, wherein the first lens group comprises, in order from the object side to an image-forming side, a first lens having negative refractive power, a second lens having positive refractive power and a third lens having positive refractive power.
8. The zoom lens as recited in claim 7, wherein the first lens group further comprises a reflector.
9. The zoom lens as recited in claim 8, wherein the reflector is a prism, and the zoom lens satisfies the following condition: 1.5<PLfw<2.2,
wherein, PL is an optical path length of incident beams within the prism, and fw is a focal length of the zoom lens at the wide-angle end.
10. The zoom lens as recited in claim 9, wherein the prism is disposed between the first lens and the second lens.
11. The zoom lens as recited in claim 7, wherein the third lens is an aspheric lens, a free-form lens or a plastic lens.
12. The zoom lens as recited in claim 1, wherein the second lens group comprises, in order from the object side to an image-forming side, a first lens having negative refractive power, a second lens having negative refractive power and a third lens having positive refractive power.
13. The zoom lens as recited in claim 12, wherein the first lens is an aspheric lens, a free-form lens or a plastic lens.
14. The zoom lens as recited in claim 12, wherein the second lens and the third lens are glued to be a doublet lens.
15. The zoom lens as recited in claim 1, wherein the fourth lens group comprises, in order from the object side to an image-forming side, a first lens having positive refractive power, a second lens having positive refractive power and a third lens having negative refractive power.
16. The zoom lens as recited in claim 15, wherein the second lens and the third lens are glued to be a doublet lens.
17. The zoom lens as recited in claim 1, wherein the third lens group comprises a first lens having positive refractive power, and the fifth lens group comprises a first lens having negative refractive power.
18. The zoom lens as recited in claim 17, wherein both the first lens of the third lens group and the first lens of the fifth lens group are aspheric lenses, free-form lenses or plastic lenses.
19. The zoom lens as recited in claim 1, further comprising a stop disposed between the third lens group and the fourth lens group.
20. The zoom lens as recited in claim 1, further comprising a filter disposed between the fifth lens group and an image-forming plane of the zoom lens.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1-11. (canceled)
12. An apparatus for cooking food by contact, comprising:
a continuous cooking surface having an underside;
heating means for heating the underside of the continuous cooking surface, the heating means being housed in at least one combustion, each chamber having a bottom wall, the operation of the heating means being controlled by valve means, thermostatic means, and user interface means; and
a portable gas fuel tank for supplying fuel to the heating means;
wherein the continuous cooking surface, the at least one combustion chamber, the heating means, and the valve means form a cooking unit that is removably mounted on a supporting cart suited to house the portable gas fuel tank and to allow the use of the apparatus either in an indoor or in an outdoor environment.
13. The apparatus according to claim 12, further comprising:
thread seats disposed in the underside of the continuous cooking surface; and
screw systems for connecting the bottom walls of the combustion chambers to the thread seats;
whereby the combustion chambers may be easily removed from the apparatus by removing the screw systems.
14. The apparatus according to claim 12, wherein the combustion chambers are arranged side by side, each combustion chamber being operably associated with a gas burner, such that the cooking surface may be selectively heated according to a plurality of different temperature zones in response to control of the heating means.
15. The apparatus according to claim 12, further comprising:
an outer casing having the shape of a truncated cone;
a gas burner disposed within the at least one combustion chamber; and
ventilation holes through the bottom wall of the combustion chamber, the ventilation holes being sized, shaped, and located to supply outside air to the heating means, so as to allow a selected gas combustion;
wherein the cooking surface has a substantially circular shape; and
wherein the combustion chamber is defined by a peripheral sheet having a shape of a truncated cone which, at the top, is closed by the cooking surface and, at the bottom, is closed by the bottom wall.
16. The apparatus according to claim 15, wherein the gas burner is constructed of chromed steel having a tubular cross-section, the gas burner extending in a substantially circular shape.
17. The apparatus according to claim 12, wherein the cooking unit comprises:
two combustion chambers arranged in a side by side relationship;
a gas burner disposed within each combustion chamber, each gas burner being constructed of chromed steel having a tubular cross-section, each gas burner extending to form one or more semi-circular branches, so as to distribute heat within semi-circular portions of the cooking surface.
18. The apparatus according to claim 12, wherein the cooking surface comprises:
a flat base portion;
a drain port in the peripheral edge of the base portion;
a peripheral raised frame formed by an inner strip that is obliquely raised from the base portion, and by a flat outer strip; and
a plurality of holes passing through the outer strip for exhausting hot air from the cooking chamber;
wherein the base portion is inclined toward the drain port at an angle ranging from about 1\xb0 to about 2\xb0 with respect to a horizontal plane.
19. The apparatus according to claim 12, further comprising:
a container carried by the cart for collecting cooking by-products;
a collecting tube aligned with the drain port for delivering the cooking by-products from the drain port to the container.
20. The apparatus according to claim 12, wherein the cart comprises:
an upper annular element having a radially extending upper rim;
a lower disk-shaped plate;
at least one stanchion coupled between the upper annular element and the lower disk-shaped plate;
a circular handle coupled to the upper annular element;
at least one support tray having an inner curvilinear edge, the support tray being configured to be supported by the underneath surface of the upper rim and the upper surface of the circular handle.
21. The apparatus according to claim 20, wherein the cart is made of stainless steel.
22. The apparatus according to claim 20, wherein the cart further comprises:
two doors having semi-circular cross-sections, each door being hingedly coupled to a stanchion, the doors being movable between a closed position defining a cylindrical enclosure, and an open position allowing access to the portable gas fuel tank.
23. The apparatus according to claim 12, further comprising:
two doors operably associated with the cart, each door having semi-circular cross-section, the doors being movable between a closed position defining a cylindrical enclosure, and an open position allowing access to the portable gas fuel tank.
24. The apparatus according to claim 22, further comprising:
at least one ventilation hole in the lower disk-shaped plate for allowing fresh air to flow toward the heating means when the doors are in the closed position.
25. The apparatus according to claim 23, further comprising:
at least one ventilation hole in the cart for allowing fresh air to flow toward the heating means when the doors are in the closed position.