1. A wide angle lens, substantially consisting of three lens groups, which are:
a first lens group having a positive refractive power which is fixed in the direction of an optical axis during focusing operations;
a second lens group that moves along the optical axis during focusing operations; and
a third lens group which is fixed in the direction of the optical axis during focusing operations, provided in this order from an object side;
the first lens group comprising:
a first lens having a positive refractive power and is of a meniscus shape having a convex surface toward the object side;
a second lens having a negative refractive power and is of a meniscus shape having a convex surface toward the object side;
a third lens having a negative refractive power and a concave surface with a radius of curvature having the smaller absolute value toward an image side; and
a fourth lens having a negative refractive power, provided in this order from the object side;
the wide angle lens further comprising:
a cemented lens formed by cementing a lens having a positive refractive power and a lens having a negative refractive power together, provided more toward the image side than the fourth lens; and
an aperture stop provided adjacent to the cemented lens toward the image side thereof;
the second lens group substantially consisting of two or fewer lenses;
the third lens group comprising at least one positive lens; and
the wide angle lens satisfying the following conditional formula:
0.00<ff1<2.00 \u2003\u2003(1)
wherein f1 is the focal length of the first lens group, and f is the focal length of the entire system in a state focused on infinity.
2. A wide angle lens as defined in claim 1 that further satisfies the following conditional formula:
0.40<ff1<1.60 \u2003\u2003(1-1).
3. A wide angle lens as defined in claim 2 that further satisfies the following conditional formula:
0.50<ff1<1.50 \u2003\u2003(1-2).
4. A wide angle lens as defined in claim 1 that further satisfies the following conditional formula:
0.00<f|f2|<0.50 \u2003\u2003(2)
wherein f2 is the focal length of the second lens group.
5. A wide angle lens as defined in claim 4 that further satisfies the following conditional formula:
0.05<f|f2|0.40 \u2003\u2003(2-1).
6. A wide angle lens as defined in claim 1, wherein:
the first lens group further comprises a fifth lens having a positive refractive power, provided adjacent to the fourth lens toward the image side thereof.
7. A wide angle lens as defined in claim 1, wherein:
the second lens group substantially consists of a single lens having a positive refractive power.
8. A wide angle lens as defined in claim 1, wherein:
the second lens group substantially consists of a single cemented lens, formed by cementing a lens having a positive refractive power and a lens having a negative refractive power together.
9. A wide angle lens as defined in claim 7 that satisfies Conditional Formula (3) below:
35<\u03bd2p \u2003\u2003(3)
wherein \u03bd2p is the Abbe’s number of the positive lens within the second lens group with respect to the d line.
10. A wide angle lens as defined in claim 9 that, satisfies Conditional Formula (3-1) below:
45<\u03bd2p \u2003\u2003(3-1).
11. A wide angle lens as defined in claim 10 that satisfies Conditional Formula (3-2) below:
70<\u03bd2p \u2003\u2003(3-2).
12. A wide angle lens as defined in claim 8 that satisfies Conditional Formula (3) below:
35<\u03bd2p \u2003\u2003(3)
wherein \u03bd2p is the Abbe’s number of the positive lens within the second lens group with respect to the d line.
13. A wide angle lens as defined in claim 12 that satisfies Conditional Formula (3-1) below:
45<\u03bd2p \u2003\u2003(3-1).
14. A wide angle lens as defined in claim 13 that satisfies Conditional Formula (3-2) below:
70<\u03bd2p \u2003\u2003(3-2).
15. A wide angle lens as defined in claim 1, wherein:
the second lens group substantially consists of a single lens having a negative refractive power.
16. A wide angle lens as defined in claim 15 that satisfies Conditional Formula (4) below:
35<\u03bd2n \u2003\u2003(4)
wherein \u03bd2n is the Abbe’s number of the negative lens within the second lens group with respect to the d line.
17. An imaging apparatus, comprising:
a wide angle lens as defined in claim 1; and
an imaging element that captures images of subjects formed by the wide angle 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. A condensation drain for an exhaust gas conduit pipe, said condensation drain comprising:
an exhaust gas condensation conduit drain having essentially parallel cylindrical walls, for directing the flow of exhaust gas phase material from a gas appliance through said exhaust gas condensation conduit drain, wherein condensation from the exhaust gas phase material passing through said exhaust gas condensation conduit drain collects on the essentially cylindrical parallel walls of the exhaust gas condensation conduit drain;
said exhaust gas condensation conduit drain having an outer conduit portion with essentially parallel cylindrical walls with a length and having an exterior diameter, wherein said exterior diameter is essentially the same throughout the length of the outer conduit portion and having an interior diameter that is essentially the same throughout the length of the outer conduit portion, said outer conduit portion having an upper region, a lower region and a middle region, said upper region configured for coupling said exhaust gas condensation conduit drain to an exhaust gas conduit pipe, said middle region configured to completely receive an inner conduit portion, said inner conduit portion having a length, said inner conduit portion fully disposed within said essentially parallel cylindrical walls of said outer conduit portion, said inner conduit portion having essentially parallel cylindrical walls that are generally the same diameter along the entire length of the inner conduit portion, and having an outer diameter which is slightly less than the interior diameter of the said outer conduit portion;
said inner conduit portion having an engagement region configured for producing a frictional fit with said essentially parallel cylindrical walls of said outer conduit portion, said engagement region including a recessed ring portion, said recessed ring portion further including a washer disposed in said recessed ring portion;
a recess stop disposed in said inner conduit portion, said recess stop forming an inwardly protruding ridge on an interior cylindrical wall portion of said inner conduit portion, wherein said recess stop is configured to provide a stopping point when said inner conduit portion of said exhaust gas condensation conduit drain is coupled to one of an exhaust gas conduit pipe or a gas appliance;
said inner conduit portion including a collection lip disposed in an upper region of said inner conduit portion, said collection lip tapering inwardly away from said inner wall of said outer conduit portion of said exhaust gas condensation conduit drain, and configured to produce a collection channel between the inner wall of said outer portion of the exhaust gas condensation conduit drain and the collection lip, for collecting exhaust gas condensation from the interior walls of said exhaust gas conduit pipe and said exhaust gas condensation conduit drain, said collection lip having a diameter that is less than said diameter of said inner wall of said outer conduit portion; and
a drain port, disposed in said middle region of said outer conduit portion and fluidly coupled to said collection channel, and configured for receiving exhaust gas condensation from said collection channel.
2. The drain for a conduit of claim 1, further comprising a drain port valve wherein the valve allows liquids to pass and prevents the passage of gas.
3. The drain for a conduit of claim 1, wherein the engagement region of the inner conduit portion is permanently coupled to the outer conduit portion.
4. The drain for a conduit of claim 1, wherein the exhaust conduit runs in a substantially vertical direction.