Iris diaphragm having a given shape without shape rotation

Abstract

1. An iris diaphragm (1) having an optical axis (O), comprising: a fixed ring (RF); and a plurality of blades (L) [of formula (I)] defining a diaphragm aperture (OD) of a predetermined shape, the blades being movable in a plane perpendicular to the optical axis relative to the fixed ring, each blade comprising a control pin (PC); and a control ring (RC) designed to rotate about the optical axis relative to the fixed ring and comprising m control guideways (GC), each control pin (PC) being movable along each one of the control guideways by advancing along each of the control guideways, the rotation of the control ring (RC) about the optical axis causes the movement of the control pins (PC) in the control guideways to change the area of ​​the aperture while maintaining a predetermined aperture shape without causing a rotation of the predetermined shape relative to the fixed ring.

Description

[Technical field]

[0001] The present invention relates to the field of iris diaphragms. [Background technology]

[0002] Objective lenses in photographic equipment and cinematographic cameras are generally equipped with a circular aperture arranged transversely to the optical axis of the lens. Circularity over the entire aperture is desirable in order to take full advantage of the qualities of objective lenses, which are constructed of spherical lenses with minimal aberrations in the recorded image.

[0003] To generate these apertures, one can use a simple hole in a wall interposed in the optical path, or several holes arranged in a moving element that allows simple adjustment of different aperture diameters.

[0004] Other optical systems requiring greater compactness or a large number of different aperture values ​​use an iris diaphragm which allows continuous adjustment between maximum and minimum aperture.

[0005] The iris diaphragm consists of a set of blades whose edges form a regular polygon.

[0006] 1 shows a prior art iris diaphragm PA with an aperture O in configuration A, which has a smaller aperture than configuration B. The iris diaphragm PA includes a number of blades L, typically made of metal or plastic. To allow for adjustment of the aperture size, each blade is connected to a ring R, for example by a pivot connection whose axis is perpendicular to the plane of the diaphragm, or can be translated relative to the ring R. By controlled movement of the blades, the aperture O can be reduced or increased. The aperture of the iris diaphragm is typically controlled by a peg T located on the end face of the ring of the diaphragm.

[0007] The number and shape of the blades that make up the iris are variable. The shape of this aperture determines the shape of the out-of-focus background area or blur. Thus, a large-aperture objective with an aperture made up of many (8 or 9) circular blades allows a proper circular-looking blur effect and a clearer transition with a clear focus zone. The more blades there are, the more closely the shape of the spot matches the shape of a perfect disk. Conversely, a particular objective produces a pentagonal or hexagonal blur effect, depending on the number of blades that make up the aperture of the objective. The shape of the blur area may be oval, depending on the optical design of the objective, especially when using anamorphic objectives (for example, in the case of cinema objectives).

[0008] Controlling the shape and orientation of the bokeh effect is important in certain applications (photography and cinema). In prior art diaphragms, the shape rotates depending on the aperture size of the diaphragm. This effect is undesirable. Summary of the Invention [Problem to be solved by the invention]

[0009] The object of the present invention is to overcome certain problems of the prior art. The subject of the present invention is therefore an iris diaphragm of a given shape, the structure of which is suitable for defining an aperture producing a defocus effect whose type and orientation of shape does not vary depending on the diaphragm aperture size. [Means for solving the problem]

[0010] To this end, one subject of the invention is an iris diaphragm having an optical axis, - a fixing ring; a plurality (m∈N>1) of blades defining a diaphragm aperture of a predetermined shape, the blades being movable in a plane perpendicular to the optical axis relative to a fixed ring, each blade including a control pin; a control ring designed to rotate about an optical axis relative to a fixed ring and including m control guideways, each control pin being capable of moving along each one of the control guideways by advancing along each of the control guideways; Including, - by movement of a control pin in a control guideway, a movement in a plane perpendicular to the optical axis of the blade relative to the fixed ring is caused, so that a rotation of the control ring about the optical axis changes the area of ​​the aperture while maintaining a predetermined aperture shape, without causing a rotation of the predetermined shape relative to the fixed ring; It is an iris diaphragm.

[0011] According to embodiment M1 of the present invention, the fixed ring comprises a plurality (n∈N≧2m) of guiding guideways, each blade comprises two respective moving pins that can each move in one of the guiding guideways by running along the respective guiding guideways, the shape of each guiding guideway being such that a rotation of the control ring about the optical axis causes each of the moving pins to move along the guiding guideway and thus the blade to move relative to the fixed ring. As an option, m=2 and the predetermined shape is a cat's eye.

[0012] As an option, in embodiment M1, each blade is associated with two respective guiding guideways in which the two moving pins of this blade can move.

[0013] As an option, in embodiment M1, the control pin of each blade is located between the two moving pins of this blade.

[0014] Optionally, in the present invention, the fixing ring and the control ring are configured such that the control ring rotates about the optical axis in a predetermined sector. Optionally, the fixing ring and the control ring are configured to define a maximum lateral dimension of the aperture.

[0015] As a preference, in the present invention, the blades and the guiding guideways exhibit centrosymmetrical relationship with respect to the optical axis.

[0016] Other characteristics, details and advantages of the invention will become apparent from reading the description given with reference to the attached drawings, each given by way of example, in which: [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic diagram of a prior art iris diaphragm. [Diagram 2] FIG. 2 is an exploded view of an aperture according to an embodiment of the present invention. [Figure 3A] 11A-11C are front views of the fixing ring and blades of an aperture according to one embodiment of the present invention for different aperture opening sizes. [Figure 3B] 11A-11C are front views of the fixing ring and blades of an aperture according to one embodiment of the present invention for different aperture opening sizes. [Figure 3C] 11A-11C are front views of the fixing ring and blades of an aperture according to one embodiment of the present invention for different aperture opening sizes. [Figure 4A] 1A-1C are front views of an aperture according to one embodiment of the present invention for different aperture opening sizes. [Figure 4B] 1A-1C are front views of an aperture according to one embodiment of the present invention for different aperture opening sizes. [Figure 4C] 1A-1C are front views of an aperture according to one embodiment of the present invention for different aperture opening sizes. [Diagram 5] FIG. 2 is an exploded view of an aperture according to an embodiment of the present invention. [Figure 6A] 11A-11C are front views of the fixing ring and blades of an aperture according to one embodiment of the present invention for different aperture opening sizes. [Figure 6B] 11A-11C are front views of the fixing ring and blades of an aperture according to one embodiment of the present invention for different aperture opening sizes. [Figure 6C] 11A-11C are front views of the fixing ring and blades of an aperture according to one embodiment of the present invention for different aperture opening sizes.

[0018] In the drawings, elements are drawn to scale unless otherwise indicated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] 2 illustrates diagrammatically an exploded view of an iris diaphragm 1 according to the invention, which is particularly suitable for camera or photographic objectives. The configuration illustrated in this drawing, hereinafter referred to as embodiment M1, is given as a non-limiting example and can be modified by variations obvious to a person skilled in the art without departing from the scope of the invention.

[0020] The diaphragm 1 comprises a fixed ring RF which constitutes the only element of the diaphragm since it remains fixed relative to the optical axis O of the diaphragm. This is the element about which the other parts of the diaphragm 1 move. In the illustration of Fig. 2, by way of example, the optical axis O is perpendicular to the plane xy of the diaphragm and lies in the direction z.

[0021] The diaphragm comprises a plurality (m∈N>1), i.e. at least two blades L, whose edges are curved arcs and which together define an aperture OD in the form of a regular polygon. In the present invention, the blades define an aperture aperture OD of a predetermined shape. As a non-limiting example, in the embodiment M1 illustrated in FIG. 2, the diaphragm 1 comprises m=2 blades and the predetermined shape of the aperture is a "cat's eye", i.e. a shape defined by the intersection of two circular or elliptical arcs. Alternatively, according to another embodiment, the diaphragm 1 comprises m>2 blades and the predetermined shape of the aperture is more complex (see, for example, FIGS. 5-6C).

[0022] Taking into account the predetermined shape of the aperture OD, the defocus effect obtained with the diaphragm of the invention itself has the same predetermined shape.

[0023] In order to be able to change the aperture size, in the diaphragm of the invention, each blade can move in a plane perpendicular to the optical axis relative to the fixing ring. As will be explained later, this movement can be caused in different ways. Furthermore, each blade includes a control pin PC. What is meant by "includes a pin" is that a control pin PC is attached to each blade L, or in other words that a control pin PC is set on each blade L.

[0024] Finally, the diaphragm 1 comprises a control ring RC, which is designed to rotate about the optical axis relative to the fixed ring RF. The control ring RC is an element of the diaphragm that can move the control pins PC relative to the fixed ring RF. To do so, the control ring comprises as many control guideways GC as there are blades, and each control pin PC can move in each one of the control guideways by progressing along each of them. Thus, the rotation of the control ring RC causes the movement of the control pins PC in the control guideways GC. The layout and movement of the various elements of the diaphragm of embodiment M1 can be seen in Figs. 2 to 4C.

[0025] Unlike the iris diaphragm of the prior art, the aperture OD of the diaphragm 1 of the present invention provides a defocus effect whose type of shape and orientation do not change with the diaphragm aperture size. Therefore, the shape and orientation of the aperture OD must remain the same regardless of the aperture size of the diaphragm of the present invention. To achieve that, a movement of the control pin PC in the control guideway causes a movement of the blade in a plane perpendicular to the optical axis relative to the fixed ring, so that a rotation of the control ring RC about the optical axis changes the area of ​​the aperture while maintaining a predetermined aperture shape without causing a rotation of the predetermined shape relative to the fixed ring. Here, what is meant by "maintaining a predetermined shape" is that an increase or decrease in the diaphragm aperture size keeps the aperture OD in the same type of shape, and only the area of ​​the aperture changes.

[0026] According to embodiment M1, there is a guiding guideway GG that allows the blade to move relative to the fixed ring RF. More precisely, the fixed ring RF comprises a plurality (n∈N≧2m), i.e. at least four guiding guideways GG, and each blade comprises two respective moving pins PM that can each move in one of the respective guiding guideways GG by advancing along the respective guiding guideway. The shape of each guiding guideway is therefore such that a rotation of the control ring RC about the optical axis causes each of the moving pins PM to move along the guiding guideway GG, and thus the blade to move relative to the fixed ring. Alternatively, according to another embodiment, the positions of the moving pins and the guiding guideway are reversed, i.e. the guiding guideway is comprised in the blade and the moving pins in the fixed ring.

[0027] The present invention is not limited to the guiding guideway shapes illustrated in Figures 2 to 4C, but should be understood to include all shapes of guiding guideways, as long as they allow the desired effect to be obtained, i.e., the effect of maintaining the shape and orientation of the opening. In light of the specification and drawings of the present invention, a person skilled in the art will know how to adapt the shape of the guiding guideway and the shape of the blade without unreasonable trial and error. The gist of the present invention is that the opening shape and orientation can be maintained by the use of a guiding guideway that guides the movement of the moving pin of the blade, coupled with a control ring that causes the moving pin to move, and thus causes the blade to move relative to the fixed ring.

[0028] Preferably, the number of moving pins PM per blade is equal to two, in order to avoid obtaining a statically indeterminate system. Each blade is therefore associated with two respective guiding guideways in which the two moving pins of this blade can move. Furthermore, in order to limit the mechanical stresses as the moving pins move in the guiding guideways, the control pin of each blade is preferably arranged between the two moving pins of this blade.

[0029] As a preference, the blades L are arranged in such a way that they extend substantially in a plane perpendicular to the optical axis (and therefore parallel to the plane xy of the fixed ring RF). In fact, the blades L slide over one another overlapping each other. Each blade L extends in the plane xy. The blade thickness is very small compared to the blade dimensions in the plane xy. Furthermore, the opening OD may be considered to extend in the plane xy. In embodiment M1, the blades and the guiding guideways exhibit centrosymmetricity with respect to the optical axis.

[0030] According to one preferred embodiment of the invention, the fixing ring RF and the control ring RC are configured such that the control ring rotates around the optical axis in a predefined sector. As a non-limiting example, in the iris of embodiment M1 of FIG. 2, the fixing ring RF includes a collar Col presenting a slot R. Furthermore, the iris includes a peg T fixed to the control ring and capable of moving in the slot by advancing along the slot. The length of advance of the peg T in the slot R determines the magnitude of possible angular rotation of the control ring RC and thus limits the maximum and minimum aperture size that the aperture OD can achieve. FIG. 2 illustrates the fact that a user action on the peg T, indicated by the arrow in FIGS. 4A-4C, can rotate the control ring and move the control pin in the control guideway. Instead, according to another embodiment, the rotation is achieved, for example, by a rotating knob offset relative to the collar.

[0031] The iris of Fig. 2 further comprises a retaining ring B, which is fixed to the collar and is designed to hold the elements RF, L and RC close to each other without restricting the rotation of the ring RC relative to the ring RF. More precisely, the retaining ring B prevents translational movement of the ring RC along the optical axis O relative to the fixed ring RF. The retaining ring B is, for example, made in the form of an internal retaining ring fitted into a groove in the collar Col.

[0032] The rings RF, RC are formed from a material that is diffusive to visible light (eg, anodized aluminum tinted black) and then coated with a matte black lubricant treatment that reduces unwanted light.

[0033] In the aperture stack of embodiment M1, the blade is arranged between the control ring and the fixed ring. This mechanical design is the simplest, in which the moving pin of the blade can move in the guideway. Moreover, this design allows the blade to be partially protected by the rings RC and RF.

[0034] Figures 3A-4C are representations of various elements of the aperture of the embodiment M1 illustrated in Figure 2. As mentioned above, the representations are given as non-limiting examples, and the embodiment M1 illustrated in these figures can be modified by variations obvious to a person skilled in the art without departing from the scope of the invention.

[0035] 3A-3C illustrate front views of the fixed ring RF and blade L of the aperture of embodiment M1 for different aperture aperture sizes (ranging from maximum aperture size in FIG. 3A to minimum aperture size in FIG. 3C). These figures illustrate how the blade moves relative to the fixed ring depending on the aperture size, which movement is caused by the movement of a moving pin along a leading guideway GG.

[0036] 4A-4C illustrate front views of the aperture of embodiment M1 for different aperture opening sizes (ranging from the largest aperture size in FIG. 4A to the smallest aperture size in FIG. 4C). The aperture of embodiment M1 includes a stack formed of a fixed ring RF designed to hold the stack in place under a collar Col, a blade L, a control ring RC and a retaining ring B. These figures show how movement of the nail T in the slot R causes the control ring to rotate, which causes the control pin to move in the control guideway GC, which causes the moving pin to move along the guiding guideway GG.

[0037] In order for the shape of the aperture formed by the diaphragm to remain a given shape from the maximum aperture size to the minimum aperture size, it is necessary that the aperture OD formed by the blades is not cut off by one of the rings RC and RF. That means that the rings RC and RF must have a central opening that defines (in the plane xy) the maximum lateral dimension of the diaphragm aperture. This maximum lateral dimension d m is illustrated in FIG. 4A, which corresponds to the maximum aperture configuration. In embodiment M1, the slot R has a diameter of d m The travel of nail T is limited so as to produce a rotation of control ring RC about the optical axis in a predetermined sector, the sector being equal to the diameter of the openings in rings RC and RF.

[0038] 5 illustrates diagrammatically an exploded view of an iris diaphragm 1 according to embodiment M2 of the present invention. In this embodiment, by way of non-limiting example, the diaphragm includes m=3 blades and the fixed ring RF includes n=6 guiding guideways GG. The aperture (and therefore the defocus effect) formed by the blades thus has a substantially triangular shape. As in embodiment M1, each blade includes a control pin PC, which means that the control ring RC includes three control guideways GC (one for each control pin).

[0039] 6A-6C illustrate front views of the fixed ring RF and blade L of the aperture of embodiment M2 for different aperture aperture sizes (ranging from maximum aperture size in FIG. 6A to minimum aperture size in FIG. 6C). These figures illustrate how the blade moves relative to the fixed ring depending on the aperture size, which movement is caused by the movement of a moving pin along a leading guideway GG.

[0040] According to other embodiments of the invention, apertures with more than three blades can be devised to define more complex apertures and therefore defocus shapes.

Claims

1. An iris diaphragm (1) having an optical axis (O), - a fixed ring (RF), a plurality (m∈N>1) of blades (L) defining a diaphragm aperture (OD) of a predetermined shape, said blades being movable in a plane perpendicular to said optical axis relative to said fixing ring, each blade (L) including a control pin (PC); a control ring (RC) designed to rotate about said optical axis relative to said fixed ring and including m control guideways (GC), each control pin (PC) being able to move along each one of said control guideways by advancing along each of said control guideways; Including, a rotation of the control ring (RC) about the optical axis causes the movement of the blades in the plane perpendicular to the optical axis relative to the fixed ring by the movement of the control pins (PC) in the control guideways, so that the area of ​​the aperture is changed while maintaining the predetermined aperture shape without causing a rotation of the predetermined shape relative to the fixed ring; the fixed ring further comprises a plurality (n∈N≧2m) of guiding guideways (GG), each blade comprising two respective moving pins (PM) each capable of moving in one of the guiding guideways (GG) by advancing along said respective guiding guideways, the shape of each guiding guideway being such that said rotation of said control ring (RC) about said optical axis causes each of said moving pins (PM) to move along said guiding guideways (GG) and thus causes said blades to move relative to said fixed ring, Iris diaphragm (1).

2. 2. The iris diaphragm of claim 1, wherein each blade is associated with two respective guiding guideways along which the two moving pins of that blade can move.

3. 3. The iris diaphragm of claim 2, wherein the control pin of each blade is located between the two moving pins of that blade.

4. 4. The iris diaphragm of claim 2, comprising m=2 blades, and the predetermined shape is a cat's eye.

5. 4. An iris diaphragm according to any one of claims 1 to 3, wherein the fixing ring and the control ring are configured so that the control ring rotates about the optical axis in a predetermined sector shape.

6. The iris diaphragm of claim 5 , wherein the fixing ring and the control ring are configured to define a maximum lateral dimension of the aperture.

7. 4. The iris diaphragm according to claim 1, wherein the plurality of blades are disposed between the fixed ring and the control ring.

8. 4. The iris diaphragm according to claim 1, wherein the blades and the guiding guideways exhibit centrosymmetrical relationship with respect to the optical axis.

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