WO2017029441A1

WO2017029441A1 - Optical system generating special visual effects

Info

Publication number: WO2017029441A1
Application number: PCT/FR2016/051955
Authority: WO
Inventors: Adrien SICART
Original assignee: Sicart Adrien
Priority date: 2015-08-17
Filing date: 2016-07-27
Publication date: 2017-02-23
Also published as: FR3040217A1; FR3040217B1

Abstract

The present invention concerns an optical system generating visual effects on a sensitive surface (6), comprising an optical axis (5) and projecting an image onto said sensitive surface, at least a first lens (1) and a second lens (2) constituting an objective lens and disposed on said optical axis (5). According to the invention, the optical device further comprises a first optical means (7) having a surface of variable opacity, disposed on the optical axis (5), said opacity being controlled by a processor such that the visual effects obtained on the sensitive surface (6) cannot be easily deduced from the initial visual effects, and affect the defocused areas of the image.

Description

OPTICAL SYSTEM GENERATING SPECIAL VISUAL EFFECTS

TECHNICAL FIELD OF THE INVENTION

The invention relates to the field of photography; more specifically, it relates to an optical system capable of generating special visual effects on an image. The invention finds particular interest in the cinema, music videos or not, advertising clips and other media, when it comes to creating visual effects and key determinants.

STATE OF THE PRIOR ART

US 5 550 610 discloses an optical system for creating static special effects on an image. More precisely, this system makes it possible to integrate given visual effects in particular locations of the images. These specific locations are the point light sources in the background; for this purpose, a specific element such as a liquid crystal display (LCD) is placed in the plane of the diaphragm, for the purpose. Thus, this system makes it possible to obtain specific visual effects, making appear in the image shapes that are identical to the initial shape defined at the level of the LCD screen. This limitation can be inconvenient.

US 3,843,235 which discloses an apodization filter able to create progressive blurs from Gaussian distributions of opacity at the plane of the diaphragm, for the purpose.

Until now, the visual effects do not interact significantly with the specifics of the photographed scene, except the point lights in the background. [0005] A need also exists to obtain very visible visual effects, which are well controlled.

SUMMARY OF THE INVENTION

The invention aims to overcome the drawbacks of the state of the art and in particular to provide an optical system capable of intrinsically generating various special effects, and can react in a very specific and controlled way to geometric shapes present in the filmed scene.

For this purpose, an optical system is provided that generates visual effects on a sensitive surface, comprising an optical axis and projecting an image on the sensitive surface, at least a first and a second lens constituting an objective and disposed on said optical axis.

According to a first aspect of the invention, the optical system further comprises an optical means having a variable opacity surface disposed on the optical axis, said opacity being controlled by a processor so that the visual effects obtained. on the sensitive surface are not reproductions (or copies) identical to the shapes present on the surface of the optical means; and visual effects affect the defocused areas of the image.

By 'variable opacity surface' is meant a surface that allows more or less light to pass; the variation can be temporal or geographical and can affect only certain wavelengths.

A processor is any means capable of executing orders, such as instructions from a computer.

In the usual way, the defocused areas correspond to areas where the light rays from the same point of the photographed scene are not concentrated at a point on the sensor.

Thus, in a new and unexpected way, the present invention makes it possible to obtain special effects, static or otherwise, on a static or kinematic image. The shapes created can for example be moire effects. Such effects are not easily achievable according to the prior art; in addition, the visual effects obtained according to the invention are variable at infinity.

[0013] In a new and unexpected way, the visual effects obtained are not directly deductible from the visual effects displayed on the variable opacity surface. Interestingly, the optical means may have a variable transparent surface capable of modifying the aperture (F-stop) and / or transmitivity (T-stop) of the lens.

In addition, the variation of the opacity of the transparent surface is advantageously controlled by a computer-type means, whether the image is in black and white or in color.

Moreover, the objective can be structurally modified so that the defocused areas where the visual effects apply do not only include areas ahead and behind the net plane. This characteristic goes against the known prior art which proposes visual effects in the net plane; it is therefore innovative to produce specific visual effects outside the net, in a simple and perfectly controlled way.

Interestingly, the lens has a Petzval surface disposed at an axial distance greater than or equal to three times the distance for an optical system having the same focal length and the same sensor size. This aspect is contrary to known systems which allow and tend to bring the Petzval surface as close as possible to the sensor.

In accordance with an interesting aspect of the invention, the optical means has a variable transparent surface with a variable opening (F-stop) and a transmittivity (T-stop) constant. This is to vary the depth of field and the transmission of light. More specifically, the size of the transparent light-transmitting surface and its opacity are varied so that the amount of light is constant.

According to an alternative of the invention, the brightness is varied only, but not the depth of field; only the opacity is changed. More specifically, the optical means has a variable transparent surface with a constant aperture (F-stop) and a variable transmittivity (T-stop).

Without departing from the scope of the invention, the system may comprise at least one specific transparent form generated on the optical means, capable of multiplying the images in the defocused areas. In the case where the optical means is able to process color images, it is here possible to separate the colors in the defocused areas while maintaining a natural rendering in the focused areas.

According to another aspect of the invention, said at least one variable opacity surface is movable in translation on the optical means which creates an impression of movement. An impression of movement of the device is here advantageously obtained, without it being physically set in motion. Of course this characteristic is very interesting especially in that it reduces wear and the risk of malfunction of the device. According to yet another aspect of the invention, the objective comprises a tilting device.

According to a preferred embodiment of the invention, said at least one optical means is an LCD type screen.

The sensitive surface may be an electronic sensor or a film.

BRIEF DESCRIPTION OF THE FIGURES

Other features and advantages of the invention will emerge on reading the description which follows, with reference to the appended figures, which illustrate:

Figure 1 is a schematic view of an optical system according to one embodiment of the invention;

Figure 2, an example on the sensitive surface of a color liquid crystal screen;

Figure 3, another example on the sensitive surface of a color LCD screen;

FIG. 4 relates to the sensitive surface of a liquid crystal screen according to one embodiment of the invention;

Fig. 5 is a diagram of a sensitive surface of a liquid crystal screen according to another embodiment of the invention;

FIG. 5A a representation of an image without the implementation of the invention; FIG. 5B a representation with implementation of the invention and a visual effect of the duplication of the patterns belonging to defocused zones;

FIG. 6A a representation of an image without the implementation of the invention;

- Figure 6B a representation with implementation of the invention and gray visual effect, obtained outside the main pattern;

FIG. 7A a representation of another image without implementation of the invention; and

Figure 7B a representation of the image of Figure 7A, with implementation of the invention and obtaining a moire-type background image behind the main pattern.

For clarity, identical or similar elements are identified by identical reference signs throughout the figures. DETAILED DESCRIPTION OF AN EMBODIMENT

[0028] Figure 1 illustrates the essential elements of an optical system according to a preferred embodiment of the invention; in this example, the system comprises three bi-convex lenses 1, 2, 3, a concave plane lens 4 (or divergent meniscus), all arranged on an axis 5 coming from a light source (not shown), and which is projected on a sensitive surface 6 such as an electronic sensor or a film. In addition, the system according to the invention comprises at least one optical means 7 having a variable opacity. The lenses 1, 2, 3, 4, the sensitive surface 6 and the optical means 7 are placed in the path of the light beam 5 (also called the optical axis 5 in the remainder of this text). According to the embodiment of the invention illustrated in FIG. 1, from the light source to the electronic sensor 6 there are respectively: a concave plane lens 4, a bi-convex lens 1, the optical medium 7, a second biconvex lens 2 and a third biconvex lens 3.

The optical means 7 is preferably disposed at the plane of the diaphragm. Advantageously, the optical means 7 is a liquid crystal screen 7, working either in black and white, or in color. Interestingly, the means 7 has a variable opacity surface controlled by a processor (not shown); the liquid crystal screen 7 is disposed in the plane of the diaphragm. As will be explained later, the opacity of the means 7 is such that the visual effects obtained on the sensitive surface 6 are different from the initial visual effects, unlike the prior art. Interestingly, the control of the opacity is such that its variation affects the defocused areas of the image.

Thus, the final appearance of the image is decorrelated, different from the initial appearance; moreover, the use of a liquid crystal display (LCD) has the advantage of very fast processing, in real time, of the image. An LCD allows use in video; the filmmakers can thus easily and fluidly use the present invention, and obtain special effects without mechanical intervention on the lens.

In addition, unlike the prior art which uses one or more movement control mechanisms, no noise or wear is generated here since no mechanism is present.

Interestingly, depending on the contrast of the LCD, the opacity can be controlled very finely; it has a real impact on the final image. By way of illustration, if the transmission of the 'transparent' zones is 30% (for a black and white LCD), or 10% (for a color LCD), the transmission of the non-transparent areas must be less than 0.05. % in these conditions there are no artifacts. The known LCDs achieve this result, with a contrast of 1000: 1 and up. Below this value, there are artifacts prejudicial to the quality of the image. Regarding the field of photography, a very wide range of visual effects can be obtained, as well as a very fast change, even instantaneous effects due to the image control by the processor.

The present invention allows to change the size of the light passing surface, and its opacity so that the amount of light received by the electronic sensor 6 is constant. Advantageously, this modification is instantaneous, perfectly controlled and accurate. It is also possible to vary the size of the light passing surface, without varying the opacity; only the depth of field is here modified, but not the transmission of light.

If one chooses to vary only the brightness, only the opacity will be changed; the size of the light-transmitting surface will not vary.

In the case where the first optical means 7 is a color LCD, in the defocused areas, it is conceivable to separate the colors as shown in Figures 2 and 3, by dividing the total area into primary or secondary colors or Rainbow. Of course, there is an infinite number of possibilities for separating colors; the separation into three primary colors is an illustrative example.

In order to obtain blurs, if it is desired to create progressive blurs, we will rely on a Gaussian distribution of the opacity on the LCD 7; if one wishes to obtain more accentuated blurs, one will use an inverse distribution of a Gaussian distribution. [0040] Figure 4 illustrates an LCD screen having transparent windows 71 provided in its opaque surface 70; FIG. 5 illustrates an LCD screen provided with two transparent disks 71 within its opaque surface 70.

It is possible with an LCD screen according to Figure 4 to achieve a doubling or a reduction of the scene patterns, only in the defocused areas.

The comparison of FIGS. 5A and 5B illustrates this possibility offered by the invention. We see here that the elements (in three dimensions) located in the defocused areas, that is to say outside the net plane, are multiplied.

According to the examples given in Figures 5A, 5B, 6A, 6B, 7A and 7B, only the pattern placed in the net area of the image is kept intact. This main pattern is here illustrated by a shape consisting of a circle above a cone. In the defocused areas of the image, the visual effects obtained are not directly deductible from the initial effects. In other words, the visual effects obtained on the sensitive surface 6 are not copies (or identical reproductions) of the shapes present on the surface of the optical means 7. Figure 6A shows an effect of black and white stripes behind the pattern; Figure 6B illustrates a uniform gray effect behind the main pattern; Figure 7A shows fine scratches obtained behind the main pattern placed in the net plane. Furthermore, the following additional effects can advantageously be obtained according to the invention:

- an impression of camera movement - while it remains fixed - using a disc passing light, non-static on the LCD;

- If the image has geometric patterns, use geometric patterns specifically selected on the optical means 7 by convolution, to obtain moire effects, potentially mobile. Figure 7B illustrates a moire effect in the background, behind the pattern placed in the net area of the image.

For three-dimensional projections, a single lens cooperates with a first disk placed to the left of the first optical means 7, and with a second disk placed to the right of the first optical means 7; this arrangement allows to obtain alternately (and synchronously with the electronic sensor 6), images corresponding to a left eye and a right eye, which corresponds to a three-dimensional image.

If we combine the effects mentioned above with a tilting lens or sharpness plans, then the net area remains legible while the other areas, which would normally be blurred, are here with effects specific visuals.

[0050] Structurally modified lenses may have curved sharpness planes or sharp 'points' instead of planes. In known manner, the sharpness area is a plane and the defocused areas correspond to the rest of the scene. According to the invention, with the characteristic optical modifications described above, it is possible to constrain the sharpness zone to a different shape such as, for example, a disk, an inclined plane, a hyperbola, a hemisphere. Defocused zones arranged differently are thus obtained, which makes it possible to locate the effects differently from the known prior art. Of course, the skilled person can make structural and / or functional and / or ergonomic changes to this invention without departing from the scope.

Claims

An optical system generating visual effects on a sensitive surface (6), comprising an optical axis (5) and projecting an image on said sensitive surface, at least a first (1) and a second (2) lenses constituting an objective (8) and arranged on said optical axis (5), characterized in that it further comprises an optical means (7) having a variable opacity surface, said optical means (7) being arranged on the optical axis (5). ); a control processor of said opacity capable of ensuring that the visual effects obtained on the sensitive surface (6) are not identical reproductions of the shapes present on the surface of the optical means (7), and that the effects Visuals affect the defocused areas of the image.

Optical system according to the preceding claim characterized in that the variation of the opacity of the transparent surface is controlled by a computer-type means.

Optical system according to one of the preceding claims, characterized in that the objective (8) is structurally modified so that the defocused areas where the visual effects apply do not only comprise zones in front and behind a plane parallel to the sensor. Optical system according to any one of the preceding claims, characterized in that the objective (8) has a Petzval surface disposed at an axial distance greater than or equal to three times the distance for an optical system having the same focal length and the same sensor size.

Optical system according to any one of the preceding claims, characterized in that it comprises at least one specific transparent form generated on said optical means (7), capable of multiplying images in said defocused areas.

Optical system according to any one of the preceding claims characterized in that said optical means (7) is able to process color images, separating the colors in the defocused areas while maintaining a natural rendering in the focused areas.

Optical system according to any one of the preceding claims, characterized in that the said at least one surface with variable opacity of the medium optic (7) is movable in axial translation to create an impression of movement.

8. Optical system according to any one of the preceding claims characterized in that said objective comprises a tilting device.

9. Optical system according to any one of the preceding claims characterized in that said optical means (7) is an LCD type screen.