WO2015153213A1

WO2015153213A1 - Variable neutral density filter system

Info

Publication number: WO2015153213A1
Application number: PCT/US2015/022401
Authority: WO
Inventors: Andy SUBRATIE; Carey DUFFY
Original assignee: The Tiffen Company, Llc
Priority date: 2014-03-31
Filing date: 2015-03-25
Publication date: 2015-10-08

Abstract

A variable neutral density filter system having a static housing ring and a rotating housing ring, each ring to which filters can be attached. The rings are rotatable with respect to one another. The variable neutral density filter system can be attached to a matte box and a camera lens.

Description

VARIABLE NEUTRAL DENSITY FILTER SYSTEM

Background

A variable neutral density filter has two pieces of polarized glass, one is fixed and the

other rotates with respect to the first to increase and decrease light transmission. They come in different diameters and are threaded onto a camera lens. Typically, photographers will have multiple lenses. It is common to have a variety of lenses, some with the same diameter and others with different diameters. This requires either a variable neutral density filter for each lens, or removing a filter and refitting it every time a photographer changes between identically sized lenses. The traditional procedure is particularly problematic for cine lenses since not all cine lenses have a threaded internal diameter and the lens diameter is often not compatible with the filters.

Switching filters is usually not an option because of time constraints when filming.

SUMMARY

A variable neutral density filter system is disclosed having a static housing ring and a rotating housing ring, each ring to which filters can be attached. A first retaining ring is engaged with the static housing ring and has a first filter secured therein. A second retaining ring is engaged with the rotating housing ring and a second filter is secured in the second retaining ring. The static housing ring is rotatably engageable with the rotating housing ring. The rotating housing ring is further engageable with a dialing ring that couples the rotating housing ring to a lens adapter. The lens adapter is engageable with a camera lens. The second retaining ring may also be configured to hold a third filter. The static housing ring is further configured to engage with a matte box.

In an illustrative embodiment of the invention, the thickness of at least one of the first and second filters is in the range of about 1.5 mm to about 3.0 mm and at least one of the first and second filters has a thickness of about 2.2 mm.

The invention includes an apparatus comprising the variable neutral density filter system attached to a matte box and camera. The invention further includes a method of securing a variable neutral density filter system to a camera. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is an exploded views of a prior art donut with one round filter.

Figures 2A and 2B are exploded side and perspective views, respectively, of a variable neutral density filter system according to an illustrative embodiment of the invention.

Figure 3 depicts a variable neutral density filter system assembled with a camera lens and matte box according to an illustrative embodiment of the invention.

Figures 4A and 4B are a plan and a side view, respectively, of a variable neutral density filter system according to an illustrative embodiment of the invention.

Figure 5 A is a cross-sectional view taken through H-H of Figure 5B of a variable neutral density filter system according to an illustrative embodiment of the invention, wherein the static housing ring and the rotating housing ring are not fully engaged.

Figure 6A is a cross-sectional view taken through K-K of Figure 6B of a variable neutral density filter system according to an illustrative embodiment of the invention, wherein the static housing ring and the rotating housing ring are engaged.

DETAILED DESCRIPTION

A variable neutral filter system for use with imaging devices is disclosed. The system includes the variable neutral filter packaged into a device called a donut. Donuts create a light seal between a camera lens and matte box. The donut housing is preferably designed so that it interfaces with standard matte boxes, allows for the glass to rotate independently and provides the maximum field of view for conventional industry lenses.

FIG. 1 depicts an exploded view of a conventional donut ring 100. Donut ring 100 consists of a housing ring 102 into which one round glass filter 110 is disposed, the 'polarized glass', which is held in place by a retaining ring 104. A rubber ring 106 attaches to housing ring 102 and supports a lens adapter 108. Housing ring 102 is placed in a matte box and the camera lens is inserted into lens adapter 108 allowing donut ring 100 to form a light seal between the camera lens and the matte box. The variable neutral filter system according to an illustrative embodiment of the invention includes two filter housings configured for rotation relative to one another, instead of the single filter housing present in conventional do nuts. The variable neutral filter system is configured to mount a camera lens on a matte box. The term "camera" is used herein broadly to mean

"imaging device." "Matte box" is used herein to include a device to hold glass or plastic filters in place in front of a camera lens.

FIGS. 2 A and 2B depict exploded side and perspective views, respectively, of a variable neutral density filter support system 200 according to an illustrative embodiment of the invention. Static housing ring 202 accommodates a first filter 208. First filter 208 is secured within static housing ring 202 by a first retaining ring 206. First filter 208 is preferably a polarized glass filter. Static housing component 202 has an outer portion 210 for mounting static housing ring 202 to a matte box via threaded engagement or other suitable engagement mechanism (see FIG. 3). Opposing the outer portion 210 of static housing component 202 is a circumferential flange 212 that extends radially outward to form a surface that abuts a complimentary circumferential flange 222 extending radially outwardly from rotating housing ring 214. Rotating housing ring 214 outer diameter and static housing ring inner diameter are sized for a rotatable push fit. Examples of other interfaces between rotating housing ring 214 and static housing ring 202 include interference fit, press fit, and click fit. Note that the rings vary in diameter along their depth, so that only portions extending from the respective flanges toward one another need to be sized for rotational, push fit engagement. The cross-sectional profile of each housing ring will be discussed further below.

Rotating housing ring 214 accommodates a second filter 220. Second filter 220 is secured within rotating housing ring 214 by a second retaining ring 218. Second filter 220 is preferably a polarized glass filter. Preferably the gap between first filter ring 208 and second filter ring 220 is minimized with the limitation typically being the ability to safely assemble the system without damage to the filters or other system parts, and proper operation of rings 202, 214 with respect to one another.

A rubber dialing ring 224, or ring of other suitable material, preferably with a surface that facilitates secure grasping such as shown in FIG. 2B, attaches to rotating housing ring 214. Lens adapter 226 is connected to rotating housing ring 214 using ring 224, whose cross section has varying diameters along its depth that lock into channels in rotating housing 214 and lens adapter 226. Rotating housing ring 214 can have space for a third filter that would be sandwiched between second filter 220 and second retaining ring 218. Additional filters could be inserted in a similar manner and location. Lens adapter 226 allows the variable neutral density filter system to interface with camera lenses of differing diameters. Preferably lens adapter 226 is a plastic adapter ring that is fitted to a flexible rubber ring, such as ring 224. It can be designed to accept any size lenses, including the largest available camera lens. To accommodate smaller lenses, adapter rings of various interior diameters can be inserted into lens adapter 226, such as by threaded engagement.

FIG.3 depicts a variable neutral density filter system 200 attached to a camera lens 230 and a matte box 232, according to an illustrative embodiment of the invention. Static housing ring 202 is placed in matte box 232, and camera lens 230 is inserted into lens adapter 226, allowing variable neutral density filter system 200 to form a light seal between the camera lens and the matte box. A user can turn rotating housing ring 214, which is outside of matte box 230, to vary the light transmission. Rotating housing ring 214 rotates with respect to static housing ring 202. Flange 212, which extends from static housing ring 202, abuts matte box 232 when variable neutral density filter system 200 is fully inserted into matte box 232.

FIGS. 4 A and 4B depict a plan and side view, respectively, of variable neutral density filter system 200, showing how rotating housing ring 214 is inserted into static housing ring 202.

FIGS. 5 A and 6 A depict the interface between static housing ring 202 and rotating housing ring 214, wherein FIG. 5 A shows rings 202, 214 separated, but aligned, and FIG. 6A shows rings 202, 214 engaged with one another. FIG. 5 A is a cross-section taken through line H-H of FIG. 5B. FIG. 6A is a cross section taken through line K-K of FIG. 6B. As can be seen in FIG. 6A, rotating housing ring 214 and static housing ring 202 can come together, preferably in a push fit engagement, until flange 212 of static housing 202 abuts flange 222 of rotating housing ring 214. Rings 202, 214 should be sized to remain secure with a minimum of play or wobble between them. Housing ring 214 should rotate relatively freely with respect to static housing ring 202, but preferably should remain relative to one another as positioned by the user under normal use, until further adjustments are made. Various factors may affect the play between housing rings 202, 214, such as temperature, foreign matter and damage for example.

Static housing ring 202 further engages rotating housing ring 214 by an inner hook 234 in static housing 202 that engages with a complimentary slot 236 in rotating housing 214. Variations on the specific shapes of hook 234 and slot 236 and flanges 212, 222 can be used for rotational coupling of rings 202 and 214, provided rotating housing ring 214 can rotate with respect to static housing ring 202 about the lens's optical axis. Further, the relative arrangement of the two housing components could be reversed such that the static housing component is positioned rearward while the rotating housing component is forward. A challenging aspect of fitting a variable neutral density filter to a donut is the limitation of field of view, due to the close proximity of the donut to the camera lens. In order to maximize the field of view of variable neutral density filter system 200, filters 208, 220 can be constructed of ground glass that is about 2.2 mm thick and is arranged be as close to the front element of lens 230 as possible, i.e. the front piece of glass on the lens that is attached to the camera. An illustrative range of glass thickness is about 1.5 mm to about 3 mm, with a preferred range of about 2.0 mm to about 2.4 mm. The front element of lens 230 can touch the filter glass, but is preferably positioned slightly behind the filter glass to avoid scratching. The closeness of lens 230 to filters 208, 220 depends, at least in part, on the focal length and the diameter of lens 230. A wide angle lens might stop being effective once you move it about 2-3 mm behind the glass. However, a small telephoto might be functional even from 20-30 mm or further away.

Various embodiments of the invention have been described, each having a different combination of elements. The invention is not limited to the specific embodiments disclosed, and may include different combinations of the elements disclosed or omission of some elements and the equivalents of such structures. While the invention has been described by illustrative embodiments, additional advantages and modifications will occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to specific details shown and described herein. Modifications, for example, to the number of filters and component engagement mechanisms, may be made without departing from the spirit and scope of the invention. Accordingly, it is intended that the invention not be limited to the specific illustrative embodiments, but be interpreted within the full spirit and scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A variable neutral density filter system comprising:

a static housing ring;

a first retaining ring engageable with the static housing ring;

a first filter secured in the first retaining ring;

a rotating housing ring;

a second retaining ring engageable with the rotating housing ring;

a second filter secured in the second retaining ring;

the static housing ring rotatably engageable with the rotating housing ring;

the rotating housing ring, further engageable with a dialing ring;

a lens adapter engageable with the dialing ring and further engageable with a camera lens.

2. The system of claim 1 wherein the static housing ring is fixed with respect to the optical axis of the first filter.

3. The system of claim 2 wherein the rotating housing ring is configured to independently rotate about the optical axis of the second filter to vary light transmission.

4. The system of claim 3 wherein the second retaining ring is configured to hold a third filter.

5. The system of claim 1 wherein the static housing ring is configured to engage with a matte box.

6. The system of claim 1 wherein the thickness of at least one of the first and second filters is in the range of about 1.5 mm to about 3.0 mm.

7. The system of claim 6 wherein the thickness of each of the first and second filters is in the range of about 1.5 mm to about 3.0 mm.

8. The system of claim 1 wherein at least one of the first and second filters has a thickness of about 2.2 mm.

9. The system of claim 1 wherein both the first and second filters have a thickness of about 2.2 mm.

10. The system of claim 1 wherein the distance of the second filter to the front element of a wide angle lens is in the range of about 2 mm to about 3 mm.

11. The system of claim 1 wherein the distance of the second filter to the front element of a telephoto lens is in the range of about 20 mm to about 30 mm.

12. The system of claim 1 wherein at least one of the first and second filters are polarized filters.

13. An apparatus comprising:

a variable neutral density filter system according to claim 1 ; and

a matte box in which the variable neutral density filter system is mountable.

14. A method of securing a variable neutral density filter system to a camera comprising: provided a variable neutral density filter system according to claim 1 ; and

attaching the variable neutral density filter system to a matte box and camera lens.

15. A variable neutral density filter system comprising:

a static housing ring;

a rotating housing ring;

a first retaining ring engageable with one of either the static housing ring or the rotating housing ring;

a first polarized filter secured in the first retaining ring;

a second retaining ring engageable with one of the other of the static housing ring or the rotating housing ring;

a second polarized filter secured in the second retaining ring;

the static housing ring rotatably engageable with the rotating housing ring;

the one of the other of either the rotating housing ring or the static housing ring that is engaeable with the second retaining ring, is further engageable with a dialing ring; and