Non-spherical iris diaphragm

Abstract

An iris diaphragm (1) having an optical axis (O), comprising: a fixed ring (RF); a moving ring (RM) designed to rotate about the optical axis relative to the fixed ring and comprising a plurality (n) of guiding guideways (GG); a plurality (n) of blades (L) defining an elliptical diaphragm aperture (OE) having a major axis (a) and a minor axis (b), each blade being pivotable about a respective axis relative to the fixed ring and each blade (L) comprising a respective moving pin (PM) capable of moving in one of the respective guiding guideways (GG) by running along a respective guiding guideway; and a control ring (RC) designed to rotate about the optical axis relative to a fixed ring and including a control guideway (GC) which can be moved by one of the moving pins, called control pin (PC), advancing along the control guideway, and the shape of each guiding guideway (GG) along which each moving pin (PM) advances is designed such that the rotation of this control ring (RC) about the optical axis causes the control pin (PC) to cause a rotation of this moving ring (RM) and a movement of the moving pin (PM) in the guiding guideway (GG) to change the area of ​​the elliptical aperture (OE) without changing the orientation of the major and minor axes and without changing the ratio of the major axis to the minor axis.

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 miniaturization or a large number of different aperture sizes use an iris diaphragm which allows continuous adjustment between maximum and minimum aperture.

[0005] The iris diaphragm includes a set of curved, arcuate edged blades which together define an aperture in the shape of a regular polygon.

[0006] 1 shows a prior art iris diaphragm PA with an aperture O in configuration A, which has a larger 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 for a blur effect with an almost circular appearance and a clearer transition with a clear focus zone. The more blades there are, the more closely the shape of the area corresponds to 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 cine 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.

[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 having a structure suitable for defining an elliptical aperture producing a defocus effect whose type and orientation do not vary depending on the diaphragm aperture size. Summary of the Invention [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 moving ring designed to rotate about an optical axis relative to a fixed ring and including a plurality (n) of guiding guideways; - a plurality (n) of blades defining an elliptical aperture having a major axis a and a minor axis b, each blade being pivotable relative to the fixed ring about a respective axis and including a respective moving pin capable of moving in one of the respective guiding guideways by running along the respective guiding guideways; - a control ring designed to rotate about an optical axis relative to a fixed ring and including a control guideway in which one of the moving pins, called the control pin, can move by advancing along the control guideway; Including, the shape of each guiding guideway through which each moving pin travels is designed so that the control pin causes a rotation of this moving ring and a movement of the moving pin in the guiding guideway, such that a rotation of this control ring about the optical axis changes the area of ​​the elliptical opening without changing the orientation of the major and minor axes and without changing the ratio of the major axis to the minor axis, It is an iris diaphragm.

[0011] According to one preferred embodiment of the invention, the fixed ring and the control ring are configured such that the moving ring rotates about the optical axis in a predetermined sector.

[0012] According to one preferred embodiment of the present invention, the blades are disposed between a fixed ring and a moving ring. Optionally, the moving ring is disposed between the control ring and the fixed ring.

[0013] According to one preferred embodiment of the invention, the blades have different shapes.

[0014] In accordance with one preferred embodiment of the present invention, the ring is configured to define the maximum major dimension of the elliptical opening.

[0015] 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:

[0016] In the drawings, elements are drawn to scale unless otherwise indicated. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic diagram of a prior art iris diaphragm. [Diagram 2] 1 is an iris diaphragm according to the present invention. [Figure 3A] 1A and 1B are a front view, a cross-sectional view, and a perspective view, respectively, of a fixing ring according to embodiment M1 of the present invention. [Figure 3B] 1A and 1B are a front view, a cross-sectional view, and a perspective view, respectively, of a fixing ring according to embodiment M1 of the present invention. [Figure 3C] 1A and 1B are a front view, a cross-sectional view, and a perspective view, respectively, of a fixing ring according to embodiment M1 of the present invention. [Figure 4A] A front view of the fixing ring and blades of embodiment M1 for different aperture opening sizes. [Figure 4B] A front view of the fixing ring and blades of embodiment M1 for different aperture opening sizes. [Figure 4C] A front view of the fixing ring and blades of embodiment M1 for different aperture opening sizes. [Figure 4D] 13 shows the blade of embodiment M1 for different aperture opening sizes. [Figure 5A] 13A and 13B are front views of a fixed ring RC from maximum aperture size to minimum aperture size, respectively, and only two of the 16 blades, L1 and L2. [Figure 5B] 13A and 13B are front views of a fixed ring RC from maximum aperture size to minimum aperture size, respectively, and only two of the 16 blades, L1 and L2. [Figure 5C] 13A and 13B are front views of a fixed ring RC from maximum aperture size to minimum aperture size, respectively, and only two of the 16 blades, L1 and L2. [Figure 6A] 13A and 13B are front and exploded views of the aperture stack of embodiment M1 for different aperture sizes. [Figure 6B] 13A and 13B are front and exploded views of the aperture stack of embodiment M1 for different aperture sizes. [Figure 6C] 13A and 13B are front and exploded views of the aperture stack of embodiment M1 for different aperture sizes. [Figure 7A]FIG. 11 is a front view of the aperture of embodiment M1 for two aperture opening sizes. [Figure 7B] FIG. 11 is a front view of the aperture of embodiment M1 for two aperture opening sizes. [Figure 7C] FIG. 1 is an exploded view of the aperture of embodiment M1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 2 diagrammatically illustrates 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.

[0019] The diaphragm 1 comprises a fixed ring RF (not visible in Fig. 2 but shown in Figs. 3A-3C). This fixed ring RF constitutes the only element of the diaphragm since it remains fixed with respect to the optical axis O of the diaphragm. It 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.

[0020] The diaphragm comprises a moving ring RM, which is designed to rotate about the optical axis O relative to the fixed ring RF. The moving ring RM is not shown in Fig. 2 but is visible in Figs. 6A-6C and 7C. As will be explained later, the moving ring RM is the element of the diaphragm that ensures that the aperture maintains its shape when the size of the diaphragm 1 is reduced or increased. To that end, the moving ring comprises a number (n) of guiding guideways GG (Figs. 6A-6C and 7C).

[0021] The diaphragm comprises a plurality (n) of blades L, the edges of which are curved and which together define an aperture in the shape of a regular polygon. In the present invention, the blades define an elliptical diaphragm aperture OE. The elliptical aperture has a major axis a and a minor axis b. What is meant here by "elliptical aperture" is that the regular polygon defined by the blades is approximately elliptical. Taking into account the elliptical shape of the aperture OE, the defocus effect obtained with the diaphragm of the present invention is itself elliptical in shape. In order to be able to change the aperture size, in the diaphragm of the present invention, each blade can be pivoted relative to the fixed ring about a respective axis. The rotation of each blade L relative to the fixed ring RF about a respective axis is thus achieved by the respective pivot connections connecting the fixed ring RF to the blade L. Furthermore, each blade L comprises a respective moving pin PM (not visible in FIG. 2 but visible in FIGS. 6A and 6B) which can be moved in one of the guiding guideways GG by advancing along the respective guiding guideways GG. By "including pins" it is meant that a movable pin PM is attached to each blade L, or in other words, that a movable pin PM is set on each blade L.

[0022] 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 about which the moving ring RM rotates and, therefore, the moving pin PM can move. To that end, the control ring RC comprises a control guideway GC in which one of the moving pins PM, called the control pin PC, can move by advancing along the control guideway GC. This control pin PC is thus a longer moving pin PM that passes through the guiding guideway GG of the moving ring RM and advances along the control guideway GC of the control ring RC. The control pin PC can thus move along the two guideways GG and GC. The rotation of the control ring RC therefore causes a rotation of the moving ring RM by the control pin PC and, therefore, a movement of the moving pin PM in the guiding guideway GG. The layout and movement of the various elements of the diaphragm can be seen in Figs. 3A to 7C.

[0023] Unlike the iris diaphragms of the prior art, the elliptical aperture OE of the diaphragm 1 of the present invention produces a defocus effect whose type of shape and orientation do not change depending on the diaphragm aperture size. That means that the shape and orientation of the elliptical aperture OE remain the same regardless of the diaphragm aperture size. The shape of each guiding guideway GG, along which each moving pin PM travels, is therefore designed in such a way that the rotation of the control ring RC about the optical axis causes a rotation of this moving ring RM and a movement of the moving pin PM in the guiding guideway GG by the control pin PC, which changes the area of ​​the elliptical aperture OE without changing the orientation of the major axis a and the minor axis b and without changing the ratio a / b of the major axis to the minor axis.

[0024] The present invention is not limited to the guiding guideway shapes illustrated in the drawings (e.g., Figs. 6A-6C), but should be understood to include all shapes of guiding guideways, as long as these shapes allow the desired effect to be obtained, i.e., the effect of maintaining the shape and orientation of the elliptical opening. In light of the present specification and Figs. 2-8, 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 guiding guideways contained in the moving pins that guide the movement of the moving pins of the blades, and thus the rotation of the blades, in combination with a control ring that causes the moving pins to move.

[0025] According to one preferred embodiment of the invention, the fixed ring RC and the control ring RC are configured such that the moving 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 fixed ring RF includes a collar Col which indicates a slot R. Furthermore, the iris includes a peg T which is fixed to the control ring and which can move in the slot by progressing along it. The length of progression of the peg T in the slot R determines the amount of possible angular rotation of the control ring RC and the ring RM, and thus limits the maximum and minimum aperture size that the elliptical aperture OE can achieve. FIG. 2 illustrates the fact that a user's action on the peg T, indicated by the arrow in FIG. 2, 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 with respect to the collar.

[0026] The iris of Fig. 2 further comprises a retaining ring B which is fixed to the collar and is designed to hold the various rings RF, RM and RC close to each other without restricting the rotation of the rings RC and RM relative to the ring RF. More precisely, the retaining ring B prevents translational movement of the rings RC and RM along the optical axis O relative to the fixed ring RF. The retaining ring B is for example manufactured in the form of an internal retaining ring fitted into a groove in the collar Col.

[0027] In the embodiment M1 of Fig. 2, by way of non-limiting example, the major axis a of the elliptical opening OE is horizontal (in the direction x). Alternatively, according to another embodiment, by way of non-limiting example, the major axis a of the elliptical opening OE is in a direction different from the direction x (e.g., in the direction y).

[0028] Rings RM, RC and 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.

[0029] 3A-7C are representations of various elements of the aperture of the embodiment M1 illustrated in FIG. 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 the skilled person without departing from the scope of the invention. In particular, in the embodiment of FIGS. 2-7C, 16 blades, each with a respective guiding guideway, are depicted. Instead, according to another embodiment, a number of blades and guiding guideways different from 16 are used in the aperture. The more the number of blades and guideways, the more closely the shape of the defocus area corresponds to a perfect ellipse for the full aperture size of the aperture 1. Furthermore, the use of a large number of guideways makes it easier to maintain the orientation of the major and minor axes without changing the ratio of the major axis to the minor axis. Therefore, it is preferable to have at least 10 blades and guiding guideways in the aperture of the present invention.

[0030] 3A-3C are respectively a front view, a cross-sectional view and a perspective view of the fixing ring RF of embodiment M1. In this embodiment M1, the fixing ring RF has a collar Col with a slot R to restrict the rotation of the control ring about the optical axis in a predetermined sector shape by a peg T attached to the control ring. As described above, the rotation of each blade relative to the fixing ring about each axis is achieved by respective pivot connections connecting the fixing ring to the blades. In the aperture of embodiment M1, as a non-limiting example, the pivot connections are achieved by a number (n) of fixing pins PF included in the fixing ring, and each blade can pivot about each fixing pin. Alternatively, in another embodiment, the fixing pins are included in the blades rather than the fixing ring. The ring RF includes a central opening OM inscribed by an elliptical opening defined by the blades L.

[0031] 4A-4C illustrate front views of the fixed ring RF and the blades L of the embodiment M1 for different aperture sizes (ranging from the maximum aperture size in the case of FIG. 4A to the minimum aperture size in the case of FIG. 4C). To get a clearer overview of the movement of the blades as a function of the aperture size, FIGS. 5A-5C illustrate front views of the fixed ring RC and only two of the 16 blades, L1 and L2, for different aperture sizes (ranging from the maximum aperture size in the case of FIG. 5A to the minimum aperture size in the case of FIG. 5C). As a preference, the blades L are arranged in such a way that they substantially extend 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 each other overlapping each other. Each blade L extends in the plane xy. The thickness of the blades is very thin compared to the blade dimensions in the plane xy. Moreover, the elliptical aperture OE may be considered to extend in the plane xy. The blades L, the moving pin PM, the fixed pin PF and the control pin PC of the embodiment M1 are visible in FIG. 4D. From Figure 4D it can be seen that the blades do not all have the same shape so that they can define an elliptical shaped aperture over the full range of possible aperture sizes. More specifically, in embodiment M1 the blades are rotationally symmetric about the optical axis.

[0032] These Figures 4A to 5C show how the blades pivot about axes formed by each fixed pin PF depending on the opening size, this pivoting being based on the movement of a moving pin along a guiding guideway GG (not depicted in Figures 4A to 5C).

[0033] A control pin PC, which corresponds to a moving pin that is longer than the other moving pins, is shown in Figures 4A to 4C. As mentioned above, it is the movement of the control ring RC that causes the movement of the pin PC in the control guideway GC.

[0034] In embodiment M1, partially illustrated in Figures 4A-5C, the blades are stacked facing the fixing ring in the aperture, this arrangement allowing each pivot connection of the blades (by the fixing pin PF between the fixing ring and the blade) to be of lower height and therefore stronger.

[0035] 6A and 6B illustrate front views of the aperture stack of embodiment M1, where the stack is formed of a fixed ring RF, a blade L and a moving ring RM, for two aperture aperture sizes (the larger aperture size in the case of FIG. 6A and the smallest aperture size in the case of FIG. 6B). FIG. 6C shows an exploded perspective view of this stack. As these figures show, the movement of each blade relative to the fixed ring does not have the same effect on the change in the shape and orientation of the elliptical aperture. For example, due to the position of the blade, the movement of a certain blade affects the major axis a to be more changed than the movement of other blades. This is because in the present invention in embodiment M1, and more generally in the present invention, the shape of each guiding guideway is adapted depending on the position and shape of the blade associated with the guiding guideway.

[0036] In the aperture stack of embodiment M1 partially illustrated in Figures 6A-6C, the moving ring is disposed between the control ring and the fixed ring, and the blade is disposed between the moving ring and the fixed ring. This mechanical design is the simplest, in which the blade can be in a pivot connection relationship with the fixed ring, and the moving pin of the blade can move along the guiding guideway. Furthermore, this design allows the blade to be partially protected by the rings RM and RF.

[0037] Figures 7A and 7B illustrate front views of the aperture of embodiment M1 for two aperture aperture sizes (larger aperture size for Figure 7A and smaller aperture size for Figure 7B). The aperture of embodiment M1 includes a stack formed of the fixed ring RF of embodiment M1, blade L, moving ring RM, control ring, and retaining ring B designed to hold the stack in place under the collar Col. Figure 7C shows a perspective view and partial exploded view of the elements of the aperture of embodiment M1.

[0038] In order for the shape of the aperture formed by the aperture to remain elliptical from the maximum aperture aperture size to the minimum aperture aperture size, it is necessary that the aperture OE formed by the blade is not cut off by any one of the rings RC, RM and RF. This means that at least the central aperture of one of the rings is cut off by the maximum dimension a of the major axis a of the elliptical aperture. m In this embodiment M1, the slot R is arranged so that the rotation of the control ring RC about the optical axis occurs in a predetermined sector and a m The advance of the nail T is limited so that a is equal to the diameter of the apertures of the rings RC, RF and RM. This maximum dimension is called the maximum aperture configuration, i.e., the major axis a = a m An example is shown in FIG. 7A corresponding to the configuration in the above case.

[0039] The stack of the various elements in the aperture of the embodiment M1 illustrated in Figures 7A-7C is such that the moving ring is arranged between the control ring and the fixed ring. This arrangement is preferred since it is the simplest design that allows the control ring and the moving ring to move without being hindered by the pivot connection connecting the blades and the fixed ring. Alternatively, according to another embodiment, the stack of elements in the aperture is different from the stack illustrated in Figures 7A-7C. However, this other embodiment adds a lot of complexity to the design of the various elements and is therefore not preferred.

Claims

1. An iris diaphragm (1) having an optical axis (O), A fixing ring (RF); a moving ring (RM) designed to rotate about the optical axis relative to the fixed ring and including a plurality (n) of guiding guideways (GG); a plurality (n) of blades (L) defining an elliptical aperture (OE) having a major axis (a) and a minor axis (b), each blade being pivotable relative to said fixed ring about a respective axis and including a respective moving pin (PM) being movable in one of said respective guiding guideways (GG) by advancing along said respective guiding guideways; a control ring (RC) designed to rotate about the optical axis relative to the fixed ring and including a control guideway (GC) along which one of the moving pins, called a control pin (PC), can move; Including, the shape of each guiding guideway (GG) through which each moving pin (PM) travels is designed so that the control pin (PC) causes a rotation of the moving ring (RM) and a movement of the moving pin (PM) in the guiding guideway (GG) such that a rotation of the control ring (RC) about the optical axis changes the area of ​​the elliptical opening (OE) without changing the orientation of the major and minor axes and without changing the ratio of the major axis to the minor axis, Iris diaphragm (1).

2. 2. The iris diaphragm of claim 1, wherein the fixed ring and the control ring are configured to allow the moving ring to rotate about the optical axis in a predetermined sector.

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

4. The iris diaphragm of claim 3 , wherein the moving ring is disposed between the control ring and the fixed ring.

5. 3. The iris diaphragm of claim 1, wherein the blades have different shapes.

6. 3. An iris diaphragm according to claim 1 or 2, wherein the ring is configured to define a maximum dimension of the major axis of the elliptical aperture.

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