Patent Publication Number: US-2020292916-A1

Title: Double-ring lens filter holder

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims priority under 35 U.S.C. 119 from Taiwan Patent Application No. 108108635 filed on Mar. 14, 2019, which is hereby specifically incorporated herein by this reference thereto. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a lens filter holder, especially to a double-ring lens filter holder that can adjust filtering effect by adjusting relative angular position of two filters. 
     2. Description of the Prior Art(s) 
     A filter is an auxiliary photography device that is mounted in front of a lens. In addition to lens protection, the filter also absorbs light at different wavelengths to form special effects on images of photography works. Polarizing filters and neutral density filters are two types of filters that are commonly used. 
     The polarizing filter is mainly designed to exclusively allow light from particular optical axes to pass through the filter, which turns unpolarized natural light into polarized light. As a result, the polarizing filter eliminates the light reflected from places such as surfaces of non-metallic objects or water surface to brighten the color of the images. 
     The neutral density filter, by reducing the amount of light passing through the neutral density filter, allows users to reduce shutter speed of a camera, so as to produce photos with shallow depth of field even under strong light conditions. 
     A conventional lens filter holder, as shown in U.S. Pat. No. 10,146,061, comprises: a limiting ring; a lock ring mounted around a rear end of the limiting ring; and a fixed filter, an adjusting ring and a compression ring mounted within a space that is surrounded by the limiting ring. The fixed filter, the adjusting ring, and the compression ring are sequentially arranged from a rear end of the limiting ring to a front end of the limiting ring. The fixed filter is securely attached to the limiting ring and a rotary filter is attached to the adjusting ring. The lock ring may be connected with a camera lens. The adjusting ring along with the rotary filter can be driven to rotate relative to the limiting ring. The compression ring is detachably connected with the limiting ring, so as to hold the adjusting ring in the limiting ring and to prevent the adjusting ring from falling out of the limiting ring. When the conventional lens filter holder is in use, a user can simultaneously rotate the fixed filter and the rotary filer by rotating the limiting ring, or individually rotate the rotary filter that is disposed at a front side of the convention lens filter holder, so as to adjust filtering effect of the conventional lens filter holder. 
     To a professional photographer, when the fixed filter and the rotary filters are both polarizing filters, the light is polarized when passing through the rotary filter that is disposed at the front side of the conventional lens filter holder. Then by adjusting relative angular position of the rotary filter and the fixed filter, the amount of light that passes through the two filters can be adjusted. Accordingly, the conventional lens filter holder with the two polarizing filters provides both adjustable polarizing effect and adjustable dimming effect. 
     Since the conventional lens filter holder can only individually rotate the rotary filter that is disposed at a front side of the convention lens filter holder, in order to separately adjust the polarizing effect and the dimming effect, the user can only rotate the fixed filter and the rotary filter simultaneously to adjust the polarizing effect and then individually rotate the rotary filter to adjust the dimming effect. However, as the rotary filter that is disposed at the front side of the conventional lens filter holder is rotated, the polarizing effect is affected. Consequently, the user has to adjust the relative angular position of the rotary filter and the fixed filter repeatedly, which is troublesome. 
     To overcome the shortcomings, the present invention provides a double-ring lens filter holder to mitigate or obviate the aforementioned problems. 
     SUMMARY OF THE INVENTION 
     The main objective of the present invention is to provide a double-ring lens filter holder that has a slotted ring, an adapting ring, an adjusting ring, an inner filter, a driving rod, a holding ring, and an outer filter. 
     The slotted ring has an inner radial ring portion extending radially, a rear axial ring portion axially extending from an inner annular edge of the inner radial ring portion to a rear of the slotted ring, a front axial ring portion axially extending from an outer annular edge of the inner radial ring portion to a front of the slotted ring, and an arc slot formed through the front axial ring portion. The adapting ring is mounted around the inner radial ring portion and the rear axial ring portion of the slotted ring, and engages with the slotted ring. 
     The adjusting ring is rotatably mounted within a space that is surrounded by the front axial ring portion of the slotted ring. The inner filter rotatably is mounted within a space that is surrounded by the adjusting ring, and the inner filter is securely attached to the adjusting ring. 
     The driving rod is mounted through the arc slot of the slotted ring and is securely connected to the adjusting ring. 
     The holding ring is mounted within a space that is surrounded by the front axial ring portion of the slotted ring, and the holding ring is detachably connected with the front axial ring portion. The adjusting ring is held between the holding ring and the inner radial ring portion of the slotted ring. The outer filter is mounted within a space that is surrounded by the holding ring, and the outer filter is securely attached to the holding ring. 
     When the outer filter and the inner filter are both polarizing filters, a user can rotate the slotted ring to rotate the outer filter and the inner filter simultaneously, so as to adjust a polarizing effect formed by the outer filter. Then, as the polarizing effect has been set, the user pushes the driving rod to individually rotate the following inner filter, so as to adjust relative angular position of the inner filter and the outer filter and to adjust a dimming effect. Given the foregoing structure of the double-ring lens filter holder of the present invention, the polarizing effect that has been set is not affected when adjusting the dimming effect. 
     Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a partially enlarged cross-sectional side view of a double-ring lens filter holder in accordance with the present invention; 
         FIG. 2  is an exploded cross-sectional side view of the double-ring lens filter holder in  FIG. 1 ; 
         FIG. 3  is an enlarged exploded cross-sectional side view of the double-ring lens filter holder in  FIG. 1 ; and 
         FIG. 4  is an exploded perspective view of a slotted ring, an adjusting ring, an outer ring, and a driving of the double-ring lens filter holder in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to  FIGS. 1 and 2 , a double-ring lens filter holder in accordance with the present invention comprises a slotted ring  10 , an adapting ring  20 , an adjusting ring  30 , an inner filter  31 , an outer cover ring  40 , a driving rod  50 , a holding ring  60 , and an outer filter  61 . 
     With further reference to  FIGS. 2 to 4 , the slotted ring  10  has an inner radial ring portion  11 , a rear axial ring portion  12 , a front axial ring portion  13 , an arc slot  14 , and a stop protrusion  15 . 
     The inner radial ring portion  11  extends radially and has an inner annular edge and an outer annular edge. The rear axial ring portion  12  axially extends from the inner annular edge of the inner radial ring portion  11  to a rear of the slotted ring  10 . The front axial ring portion  13  axially extends from the outer annular edge of the inner radial ring portion  11  to a front of the slotted ring  10 . 
     The arc slot  14  is formed through the front axial ring portion  13 . A radian of the arc slot  14  is less than π/2. That is, the arc slot  14  subtends to a central angle that is less than 90 degrees. The stop protrusion  15  is formed on an outer annular surface of the front axial ring portion  13  and is disposed between the arc slot  14  and a front annular edge of the front axial ring portion  13 . As shown in  FIG. 4 , in the preferred embodiment, the stop protrusion  15  is formed as a circle. However, in other embodiments, the stop protrusion  15  may be formed by multiple protrusions that are arranged in a circle. 
     The adapting ring  20  is mounted around the inner radial ring portion  11  and the rear axial ring portion  12  of the slotted ring  10 , and engages with the slotted ring  10 , such that the slotted ring  10  is capable of rotating relative to the adapting ring  20 . The adapting ring  20  has a connection ring portion  21 , an outer radial ring portion  22 , and an outer thread  23 . 
     The connection ring portion  21  extends axially and is mounted around the rear axial ring portion  12 . The outer radial ring portion  22  radially extends from the connection ring portion  21  and is mounted around the inner radial ring portion  11 . The outer radial ring portion  22  protrudes outwardly from the outer annular surface of the front axial ring portion  13 . Accordingly, an annular recess AA is formed between the outer radial ring portion  22  and the stop protrusion  15 . The arc slot  14  is disposed at a bottom of the annular recess AA. 
     The outer thread  23  is formed in an outer annular surface of the connection ring portion  21  and may engage with an inner thread formed inside a front portion of a camera lens for the double-ring lens filter holder to be mounted on the front portion of the camera lens. 
     The adjusting ring  30  is rotatably mounted within a space that is surrounded by the front axial ring portion  13  of the slotted ring  10 . The inner filter  31  is rotatably mounted within a space that is surrounded by the adjusting ring  31 , and the inner filter  31  is securely attached to the adjusting ring  30 . 
     The outer cover ring  40  is rotatably mounted around the front axial ring portion  13  of the slotted ring  10  and in the annular recess AA and has a through hole  41 . The through hole  41  is formed through the outer cover ring  40  and corresponds in position to the arc slot  14  of the slotted ring  10 . 
     The driving rod  50  is mounted through the through hole  41  of the outer cover ring  40  and the arc slot  14  of the slotted ring  10  and is securely connected to the adjusting ring  30 . By pushing the driving rod  50  to move along the arc slot  14 , users can rotate the adjusting ring  30  and the inner filter  31 . With the outer cover ring  40  covering the arc slot  14 , dust can be prevented from entering an interior of the double-ring lens filter holder via the arc slot  14 . 
     The holding ring  60  is mounted within a space that is surrounded by the front axial ring portion  13  of the slotted ring  10 , and the holding ring  60  is detachably connected with the front axial ring portion  13 . The adjusting ring  30  is held between the holding ring  60  and the inner radial ring portion  11  of the slotted ring  10 . In the preferred embodiment, the holding ring  60  and the front axial ring portion  13  connects with each other via threads. The outer filter  61  is mounted within a space that is surrounded by the holding ring  60 , and the outer filter  61  is securely attached to the holding ring  60 . 
     The double-ring lens filter holder as described has the following advantages. When the outer filter  61  and the inner filter  31  are both polarizing filters, light is polarized when passing through the outer filter  61  and then is further dimmed when passing through the inner filter  31 . Therefore, a user can rotate the slotted ring  10  to rotate the outer filter  61  and the inner filter  31  simultaneously, so as to adjust the polarizing effect formed by the outer filter  61 . Then, as the polarizing effect has been set, the user pushes the driving rod  50  to individually rotate the following inner filter  31 , so as to adjust relative angular position of the inner filter  31  and the outer filter  61  and to adjust the dimming effect. Given the foregoing structure of the double-ring lens filter holder of the present invention, the polarizing effect that has been set is not affected when adjusting the dimming effect. 
     Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and features of the invention, the disclosure is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.