1. A telescopic support for a member, the member defining a work surface, said support comprising:
an outer leg part having
a tubular body defining a longitudinal axis and having an interior passage through which the longitudinal axis extends centrally; and
one or more longitudinally-extending splines extending radially, inwardly from the tubular body; and
an inner leg part having:
a shuttle body part disposed at least in part in the tubular body; and
rollers rotably mounted to the shuttle body part to support the inner leg part for longitudinal reciprocating movement in the tubular body,
wherein said rollers include, for at least one of said one or more splines, at least one grooved roller having a peripheral groove which receives said spline during said reciprocating movement to constrain said outer and inner leg parts against relative rotation about the longitudinal axis.
2. A support according to claim 1, wherein the one or more splines consists of three splines, equally-spaced from one another around an inner periphery of the tubular body.
3. A support according to claim 1, wherein the tubular body is an extruded member.
4. A support according to claim 3, wherein the tubular body is aluminum.
5. A support according to claim 2, wherein the splines are formed separately from the tubular body and snap-fit secured thereto in the outer leg part.
6. A support according to claim 5, wherein the splines are steel rods of round cross-section.
7. A support according to claim 2, wherein the inner leg part further comprises a fluted body part rigidly secured to the shuttle body part and longitudinally-extending therefrom, the fluted body part having longitudinally-extending external grooves which the splines traverse in spaced-relation when the fluted body moves within the tubular body during said longitudinal reciprocating movement.
8. A support according to claim 7, wherein the fluted body is an extruded member.
9. A support according to claim 8, wherein the fluted body is aluminum.
10. A support according to claim 1, wherein said rollers include, for at least one of said one or more splines, a pair of the grooved rollers, longitudinally-spaced from one another, to provide for longitudinal alignment of the outer and inner leg parts during said reciprocating movement.
11. A support according to claim 3, wherein said rollers include three pairs of grooved rollers, the rollers forming each pair being longitudinally spaced from one another.
12. A support according to claim 1, wherein the fit between the outer leg part and the inner leg part defines a negative allowance and wherein the tubular body deforms elastically during said reciprocating movement to accommodate such negative allowance.
13. A support according to claim 1, further comprising:
a longitudinally extending threaded driveshaft rotatably mounted to the inner leg part; and
a threaded receiver rigidly mounted to the outer leg part and in threaded receipt of the driveshaft to provide for said reciprocating movement of the outer and inner leg parts upon rotation of the driveshaft.
14. A support according to claim 13, further comprising:
a motor coupled to said driveshaft to provide for said rotation thereof.
15. A height-adjustable pedestal-style table comprising:
a foot defining a base for the table in use;
a telescopic support comprising:
an outer leg part having: a tubular body secured to the foot and extending vertically therefrom in use, said tubular body defining a longitudinal axis and having an interior passage through which the longitudinal axis extends centrally; and one or more longitudinally-extending splines extending radially, inwardly from the tubular body; and
an inner leg part having: a shuttle body part disposed at least in part in the tubular body; and rollers rotably mounted to the shuttle body part to support the inner leg part for longitudinal reciprocating movement in the tubular body, wherein said rollers include, for at least one of said one or more splines, at least one grooved roller having a peripheral groove which receives said spline during said reciprocating movement to constrain said outer and inner leg parts against relative rotation about the longitudinal axis; and
a member secured to the inner leg part and defining a work surface of the table in use.
16. A telescopic support comprising:
an outer leg part having
a tubular body defining a longitudinal axis and having an interior passage through which the longitudinal axis extends centrally; and
an inner leg part having:
a shuttle body part disposed at least in part in the tubular body; and
rollers rotably mounted to the shuttle body part to support the inner leg part for longitudinal reciprocating movement in the tubular body,
wherein the fit between the outer leg part and the inner leg part defines a negative allowance and the tubular body deforms elastically during said reciprocating movement to accommodate such negative allowance.
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 zoom lens comprising:
a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a fifth lens unit having a positive refractive power in this order from an object side to an image side,
wherein, during zooming, the lens units move along predetermined loci such that an interval between adjacent lens units varies, and the first lens unit and the third lens unit move toward the object side at a telephoto end in comparison with a wide angle end,
wherein the third lens unit includes at least two positive lenses formed of a material which satisfies the following conditional expressions,
\u03b8gF3P\u2212(\u22121.665\xd710\u22127\xb7\u03bdd3P3+5.213\xd710\u22125\xb7\u03bdd3P2\u22125.656\xd710\u22123\xb7\u03bdd3P+0.737)>0
50.0<\u03bdd3P<100.0
where \u03b8gF3P is a partial dispersion ratio of the material and \u03bdd3P is the Abbe number of the positive lens included in the third lens unit, and
wherein the zoom lens satisfies the following conditional expressions
0.01<f3ft<0.15
0.5<|f4f3|<2.5
3.00<M3fw<30.00
where fw is a focal length of the zoom lens at the wide angle end, ft is a focal length of the zoom lens at the telephoto end, f3 is a focal length of the third lens unit, f4 is a focal length of the fourth lens unit, and M3 is an amount of movement of the third lens unit at the time of zooming from the wide angle end to the telephoto end.
2. The zoom lens according to claim 1, wherein the conditional expression
0.01<|f4ft|<0.25
is satisfied.
3. The zoom lens according to claim 1, wherein the conditional expression
0.01<|f2ft|<0.10
where f2 is a focal distance of the second lens unit is satisfied.
4. The zoom lens according to claim 1, wherein the conditional expression
2.0<f3fw<8.0
is satisfied.
5. The zoom lens according to claim 1, wherein the conditional expression
0.8<M1M3<5.0
where M1 is an amount of movement of the first lens unit at the time of zooming from the wide angle end to the telephoto end, is satisfied.
6. The zoom lens according to claim 1, wherein the conditional expression
71.0<\u03bdd3Pave<100.0
where \u03bdd3Pave is an average value of the Abbe number of all positive lenses included in the third lens unit, is satisfied.
7. The zoom lens according to claim 1, comprising
a sixth lens unit having a positive refractive power on the image side of the fifth lens unit.
8. The zoom lens according to claim 1, wherein
focusing from an object at infinity to an object at short-distance is achieved by moving the fifth lens unit parallel to the optical axis in a direction towards the object side.
9. The zoom lens according to claim 1, comprising an aperture stop configured to move along a locus different from the loci of movement of the lens units at the time of zooming.
10. An image pickup apparatus comprising:
a zoom lens; and
an image sensor configured to receive an image formed by the zoom lens, wherein
the zoom lens comprises, in order from an object side to an image side,
a first lens unit having a positive refractive power, a second lens unit having a negative refractive power, a third lens unit having a positive refractive power, a fourth lens unit having a negative refractive power, and a fifth lens unit having a positive refractive power in this order,
wherein, during zooming, the lens units move to draw predetermined loci such that an interval between lens units varies, and the first lens unit and the third lens unit move toward the object side at the telephoto end in comparison with a wide angle end,
wherein the third lens unit includes at least two positive lenses formed of a material which satisfies the following conditional expressions,
\u03b8gF3P\u2212(\u22121.665\xd710\u22127\xb7\u03bdd3P3+5.213\xd710\u22125\xb7\u03bdd3P2\u22125.656\xd710\u22123\xb7\u03bdd3P+0.737)>0
50.0<\u03bdd3P<100.0
where \u03b8gF3P is a partial dispersion ratio of a material and \u03bdd3P is the Abbe number of the positive lens included in the third lens unit, and
wherein the zoom lens satisfies the following conditional expressions
0.01<f3ft<0.15
0.5<|f4f3|<2.5
3.00<M3fw<30.00
where fw is a focal length of the zoom lens at the wide angle end, ft is a focal length of the zoom lens at the telephoto end, f3 is a focal length of the third lens unit, f4 is a focal length of the fourth lens unit, and M3 is an amount of movement of the third lens unit at the time of zooming from the wide angle end to the telephoto end.