Manual Focus Control Device

Abstract

A focus control device is adapted to adjust a camera lens. The device comprises a rotational input device (1), a variable gear ratio means (10) and a rotational output means so coupled to communicate a first rotational movement applied to said rotational input device to said variable gear ratio means (10) and to communicate a second rotational movement from said variable gear ratio means (10) to said rotational output means. The variable gear ratio means provides a variable adjustment of the angular velocity of said second rotational movement relative to the angular velocity of said first rotational movement.

Claims

1. A manual focus control device adapted to adjust a camera lens comprising a rotational input device (1), a variable gear ratio means (10) and a rotational output means so coupled to communicate a first rotational movement applied from said rotational input device to said variable gear ratio means and to communicate a second rotational movement from said variable gear ratio means to said rotational output means; characterised in that said variable gear ratio means provides a variable adjustment of the angular velocity of said second rotational movement relative to the angular velocity of said first rotational movement.

2. A device according to claim 1, wherein said variable gear ratio means is an infinitely variable gear ratio means.

3. A device according to either of the preceding claims, wherein said variable gear ratio means further comprises a first gear arranged on a first shaft (5) which is coupled to said rotational input device; whereby said first gear comprises a first variable radius means.

4. A device according to claim 3, wherein said variable gear ratio means further comprises a second gear arranged on a second shaft (5) which is coupled with said rotational output device; whereby said second gear comprises a second variable radius means.

5. A device according to claim 4, wherein said variable gear ratio means further comprising a belt located about said first gear and said second gear, which in use, communicates a third rotational movement from said first gear to said second gear.

6. A device according to claim 5, wherein said belt is a ‘V’ belt (14).

7. A device according to claim 3 or 5, wherein said first variable radius means further comprises a first conical roller (12a) and a second conical roller (12b) arranged on said first shaft, whereby the diameter of said first conical rollers is reduced in a direction towards said second conical roller; and said second conical roller is reduced in a direction towards said first conical roller

8. A device according to claim 7 wherein the position of said second conical roller is adjustable along said first shaft relative to said first conical roller.

9. A device according to claim 7 or 8, wherein said first and second conical rollers are pulled together via a first resilient spring member.

10. A device according to claim 4 or 5, wherein said second variable radius means further comprises a third conical roller (13a) and a fourth conical roller (13b) arranged on said second shaft (5), whereby the diameter of said third conical rollers is reduced in a direction towards said fourth conical roller; and said fourth conical roller is reduced in a direction towards said third conical roller

11. A device according to claim 10, wherein said fourth conical roller is adjustable along said second shaft relative to said third conical roller.

12. A device according to claim 10 or 11, wherein said third and fourth conical rollers are pulled together via a second resilient spring member.

13. A device according to any of the preceding claims, further comprising a position indicator (3) arranged on the output of said rotational input device.

14. A device according to any of the claims 1 to 12, further comprising a position indicator arranged on the output of the variable gear ratio means.

15. A device according to any of the claims 1 to 12, further comprising a position indicator arranged on the input of the variable gear ratio means.

16. A device according to any of the preceding claims, wherein said rotational input device further comprising a first adjustable stop element which cooperates with said position indicator when said position indicator moves in a first direction.

17. A device according to any of the preceding claims, further comprising a second adjustable stop element which cooperates with said position indicator when said position indicator moves in a second direction.

18. A device according to any of the preceding claims, further comprising a third adjustable stop element located between the output of said variable gear ratio means and the input of said rotational output means.

19. A device according to any of the preceding claims, further comprising a drag means located between the output of said rotational input device and the input of said variable gear ratio means.

20. A device according to any of the preceding claims 1 to 19, further comprising a drag means located between the output of said variable gear ratio means and the input to said rotational output means.

21. A device according to either of the preceding claim 19 or 20, wherein said drag means provides an adjustable resistance to the rotational movement communicated from said rotational input device to said variable gear ratio means.

22. A device according to any of claims 19 to 21, wherein said drag means further comprises a fluid shearing means for providing said resistance.

23. A device according to any of claims 19 to 21, wherein said drag means further comprises a lubricated friction means for providing said resistance.

24. A lens comprising a focus control device according to any of the preceding claims.

25. A camera comprising a focus control device according to any of the preceding claims.

26. A focus control device as substantially hereinbefore described by the text and/or Figures.

27. A focus control device adapted to adjust a camera lens comprising a rotational input device, a gear ratio means and a rotational output means so coupled to communicate a first rotational movement applied to said rotational input device to said gear ratio means and to communicate a second rotational movement from said gear ratio means to said rotational output means; characterised in that said focus control device further comprises drag means located between the output of said rotational input device and the input of said variable gear ratio means.

28. A device according to claim 27, wherein said gear ratio means comprises a fixed gear ratio.

29. A device according to claim 28, further comprising a second fixed gear ratios; whereby said fixed gear and said second fixed gear are selectable

30. A device according to any of the preceding claims 27 to 29, wherein said drag means is located between the output of said gear ratio means and the input to said rotational output means.

31. A device according to any of the preceding claims 27 to 30, wherein said drag means provides an adjustable resistance to the rotational movement communicated from said rotational input device to said gear ratio means.

32. A device according to any of the preceding claims 27 to 31, wherein said drag means further comprises a fluid shearing means for providing said resistance.

33. A device according to any of the preceding claims 27 to 31, wherein said drag means further comprises a lubricated friction means for providing said resistance.

Description

BRIEF DESCRIPTION OF FIGURES

[0043] FIG. 1 is an isometric view of a current follow focus.

[0044] FIG. 2 is a second isometric view of the same current follow focus from the opposite point of view.

[0045] FIG. 3 is the same follow focus as in FIG. 2 and from the same angle as in FIG. 2 but with the case work removed to show internal details of the drive train.

[0046] FIG. 4 is a block diagram of the invention. FIG. 5 shows a possible variable ratio drive train at one extreme of its adjustment.

[0047] FIG. 6 shows the same variable ratio drive train as FIG. 5 but at the opposite extreme of its adjustment.

DETAILED DESCRIPTION OF THE FIGURES

[0048] FIGS. 1 and 2 show a current follow focus having a hand wheel (1) which is connected to a final drive roller (2) via a fixed gear ratio (not shown as it is internal to the follow focus), a position indicator (3) that is connected to the hand wheel (1) and a bracket with a pair of slots (8) that are used to mount the follow focus to a camera rig. The position indicator (3) is intended to be a visual indicator and also in a preferred embodiment readily markable by a user to enable a user to move away from a focus position and subsequently return thereto. In one embodiment, as illustrated, the indicator can be a disc, markable by a conventional pencil or the like. This feature, along with the indicator being separate from the camera and lens allows for the fact that any focus or zoom indication of a particular lens position on the input changes whenever the variable ratio drive is changed. The indicator on the output of a variable drive would stay the same but is less sensitive, and so less accurate for high drive ratios.

[0049] FIG. 3 shows the same follow focus as in FIGS. 1 and 2 but with the covers removed so the drive system used in this follow focus can be seen. The drive system consists of;

[0050] a fixed ratio belt drive consisting of a larger pulley (4a) that is connected to, and turns with the hand wheel (1) and a smaller pulley (4b) that is connected to and turns with a drive shaft (5);

[0051] a fixed ratio pair of helical gears consisting of a first helical gear (6a) that is connected to and turns with drive shaft (5) and a second helical gear (6b). The helical gears are used to turn the drive through 90 degrees so it now rotates about an axis parallel to the lens.

[0052] The drive system also includes a fixed ratio belt drive consisting of a first pulley (7a) which is connected to and turns with second helical gear (6b) and a second pulley (7b) which is connected to and turns with the final drive roller (2).

[0053] FIG. 4 shows a schematic diagram of the follow focus invention. For clarity, items that are substantially the same as those in the current focus use the same number suffixed with an apostrophe. The follow focus consists of;

[0054] a hand wheel (1′) that is connected and turns with a first drive shaft (8);

[0055] a drag unit (9) that is connected to the hand wheel, whereby the drag unit produces a resistive force to the movement of the hand wheel, the resistive force being linked to the angular velocity of the hand wheel;

[0056] a variable ratio drive element (10) takes in the rotation on first drive shaft (8) and outputs a rotation on a second drive shaft (5′). The variable drive train has a velocity ratio so that the angular velocity of the second drive shaft (5′) is X times that of the angular velocity of the first drive shaft (8). The variable drive train is constructed so that the user can change this value X.

[0057] a fixed ratio pair of helical gears consisting of a first helical gear (6a′) that is connected to and turns with the second drive shaft (5′) and a second helical gear (6b′). The helical gears are used to turn the drive through 90 degrees so it now rotates about an axis parallel to the lens.

[0058] The follow focus also includes a fixed ratio belt drive consisting of a first pulley (7a′) which is connected to and turns with second helical gear (6b′) and a second pulley (7b′) which is connected to and turns with the final drive roller (2′).

[0059] The final drive roller (2′) is in contact with the focus ring (11) of the lens and so drives this focus ring (11) with a fixed gear ratio. The focus ring (11) is part of the lens and not strictly part of the follow focus so is shown with a dotted line.

[0060] A position indicator (3′) is connected to the second drive shaft (5′) and indicates the rotational displacement of the second drive shaft (5′). Because the gear ratio between the second drive shaft (5′) and focus ring (11) is fixed the angular displacement shown by the position indicator (3′) is proportional to that of the focus ring (11). So the position indicator (3′) provides a direct indication of the angular displacement of the focus ring (11).

[0061] In addition the position indicator (3′) could incorporate one or more adjustable hard stops these stops can be moved to a position and locked in place by the user. They then stop the position indicator (3′) from rotating past this point; thus limiting the rotation of the focus ring (11) beyond this point. This allows the user to carry out variation of the focus with a high degree of repeatability by; [0062] 1. a use of the hand wheel (1) on the follow focus to adjust the focus ring (11) on the lens to a certain rotational displacement that gives the correct focus, [0063] 2. seting the adjustable hard stop on the position indicator (3′) to the current position. [0064] 3. using the hand wheel (1) on the follow the focus to move focus ring (11) to a different rotational displacement, [0065] 4. then rapidly rotate the hand wheel (1) of the follow focus back until the position indicator (3′) hits the hard stop preventing further rotation. The focus ring (11) will now be back at the original rotational displacement that gave the correct focus.

[0066] FIGS. 5 and 6 show an embodiment of the variable ratio drive element (10), which comprises a first pair of conical rollers (12a) and (12b) that are mounted so that they rotate with drive shaft (8) but can move along the first drive shaft (8). A second pair of conical rollers (13a) and (13b) are mounted so that they rotate with second drive shaft (5′) but can move along the drive shaft (5′). A V belt (14) sits between the first pair of conical rollers (12a), (12b) and the second pair of conical rollers (13a) and (13b).

[0067] By allowing the user to control the gap between one pair of the conical rollers the radius at which the belt (14) sits relative to the corresponding shaft can be controlled. The belt (14) can be tensioned by spring loading the other pair of conical rollers to adjust the spacing therebetween, so that the spacing will automatically reduce, forcing the belt (14) out to a larger radius from the corresponding shaft. Because the radius of the belt (14) around the first drive shaft (8) and the radius of the belt (14) around second drive shaft (5′) has been altered, the gear ratio of the drive has changed, so the user can effectively control the gear ratio of the drive train. Because the gear ratio is varied by controlling the spacing between the rollers the user can set the gear ratio to any value between the maximum and minimum gear ratio that the drive train is capable of, this ability is referred to as an infinitely variable gear ratio. For example let us assume the user can control the spacing between conical rollers (13a) and (13b) and that conical rollers (12a) and (12b) are sprung together.

[0068] In FIG. 5 the user has set conical rollers (13a) and (13b) close together pushing the belt (14) out to a large radius around the second drive shaft (5′). This means a large amount of belt (14) is used in wrapping around conical rollers (13a) and (13b). This leaves only a small amount of belt (14) to wrap around conical rollers (12a) and (12b) forcing the belt (14) to come down to a small radius around the first drive shaft (8). The spacing between conical rollers (12a) and (12b) is thereby forced to increase. Due to the different radius of the belt (14) around first drive shaft (8) and second drive shaft (5′) the first drive shaft (8) will have to complete several rotations for each rotation of the second drive shaft (5′).

[0069] In FIG. 6 the user has set conical rollers (13a) and (13b) far apart. This allows the belt (14) to slip down between the rollers so that it is at a small radius around the second drive shaft (5′). This means a small amount of belt (14) is used in wrapping around conical rollers (13a) and (13b). This leaves a large amount of belt (14) to wrap around conical rollers (12a) and (12b). Because conical rollers (12a) and (12b) are sprung loaded they are forced together pushing the belt (14) out to a large radius relative to first drive shaft (8). Due to the different radius of the belt (14) around first drive shaft (8) and second drive shaft (5′) the first drive shaft (8) will have to complete only a portion of a rotation for each rotation of the second drive shaft (5′) so the gear ratio has changed from when the drive was in the configuration shown in FIG. 5.

[0070] It is seen from FIGS. 5 and 6, that in a preferred embodiment the conical rollers (12a, 12b) on the first drive shaft are orientated towards each other such that the diameter of each of the rollers reduces in the direction of the other roller. A similar configuration is also shown in the conical rollers (13a, 13b) on the second drive shaft.

[0071] The same effect could be achieved by allowing the user to control the spacing between conical rollers (12a) and (12b) and having conical rollers (13a) and (13b) sprung together.

[0072] In an alternative embodiment of the invention, the drag unit (9) could be located subsequent to the variable ratio drive element (10). This would produce a resistive force to rotation of the focus ring (11), whereby the resistive force is linked to the angular velocity of the focus ring (11).

[0073] The advantages of the follow focus are: [0074] Quick and easy to adjust the “sensitivity” of the follow focus by changing the gear ratio between the hand wheel of the follow focus and the focus ring of the lens. [0075] Infinitely adjustable gear ratio rather than discreet steps. [0076] Only need one final drive roller which matches the tooth form of the focus ring on the lens. [0077] Stop marks do not need resetting when gear ratio is changed. [0078] Adjustable physical stops do not need resetting when gear ratio is changed. [0079] Uses belts giving zero backlash drive with minimal cost

[0080] In another alternative embodiment of the invention, the variable ratio drive element (10) is replaced with a fixed gear ratio drive element, which takes in the rotation on first drive shaft (8) and outputs a rotation on a second drive shaft (5′). Whereby, the angular velocity of the second drive shaft is X times that of the angular velocity of the first drive shaft (8). The drive train is constructed so that this value X is fixed and therefore the angular velocity of the second drive shaft is therefore not adjustable.

[0081] In another embodiment of the invention, the drive train incorporates a gear ratio drive element comprising a stepped variable gear ratio (e.g. “coarse” and “fine” for 2 ratios; or 3 or more selectable gear ratios within the gear box, if required. T

[0082] he features of the follow focus device are set out as follows: [0083] 1. A follow focus including: [0084] a. a user input device such as a hand wheel, lever or other component; [0085] b. a variable gear ratio system; and [0086] c. an interface that transmits the drive to the lens. [0087] 2. As point 1 with an infinitely variable gear ratio system. [0088] 3. As point 2 with the infinitely variable gear ratio system being provided by a V belt and conical pulley arrangement as per FIGS. 5 and 6. [0089] 4. As point 1 with a position indicator being provided to indicate rotation of the hand wheel or the drive to the lens. [0090] 5. As point 4 with the position indicator being provided after the variable gear ratio system so indicating rotation of the drive to the lens. [0091] 6. As point 4 with the position indicator being provided before the variable gear ratio system so indicating rotation of the user input device. [0092] 7. As point 1 with one or more adjustable physical stop being provided to stop rotation of the hand wheel or the drive to the lens beyond a user defined point. [0093] 8. As point 7 with one or more adjustable physical stop being provided before the variable gear ratio system to stop rotation when the hand wheel gets to a certain position. [0094] 9. As point 7 with one or more adjustable physical stop being provided after the variable gear ratio system to stop rotation when the user input device gets to a certain position. [0095] 10. A follow focus including: [0096] a. a user input device such as a hand wheel, lever or other component; [0097] b. a drag unit that produces a resisting torque that is related to the speed of rotational movement; and [0098] c. an interface that transmits the drive to the lens. [0099] 11. As point 10 where the amount of drag is adjustable by the user so that it will produce more or less resistance in response to the same angular velocity. [0100] 12. As point 10 with the drag being provided by shearing fluid. [0101] 13. As point 10 with the drag being provided by lubricated fiction. [0102] 14. As points 1 and 10 with the drag unit positioned between the user input device and the variable gear ratio system so that the resisting torque is related to the rotational velocity of the user input device. [0103] 15. As points 1 and 10 with the drag unit positioned between the variable gear ratio system and the drive to the lens so that the resisting torque is related to the rotational velocity of the drive to the lens.