HK1100858A - Optical image converter system - Google Patents

Description

Optical image conversion system

The invention relates to an optical image conversion system having an object-oriented recording lens for generating a real intermediate image of an object of a defined size and depth of field on a first image plane; an image converter having a recording lens disposed in the optical path behind it, facing the first image plane, for generating a real main image of the object on the second image plane; there is also a prism arrangement in the optical path, wherein a light-transmissive projection panel is arranged at the first image plane.

Image conversion systems of this type are known (EP0950912a2) in which the projection disk is arranged behind a recording lens in a lens tube, an image conversion lens being directed towards the rear of the projection disk, on the image plane of which a camera negative of a video camera or a CCD image receptor is arranged. The intermediate image generated by the recording lens on the first image plane is projected onto the second image plane, the image size and/or the image format being changed relative to the intermediate image by means of the image conversion lens. Such a system allows the use of relatively large image formats, for example 16, 32 or 70mm side lengths in the region of the first image plane, and therefore uses commercially available film camera lenses for such formats. In this way, a camera setting with a low depth of field is obtained, which is not possible with video cameras currently having a relatively small receiving chip. Furthermore, the image conversion lens ensures that an intermediate image can be projected onto a small video chip of the video camera and recorded thereon, the image having a high luminance and a preset depth of field. Image conversion systems can also be used for images and movies produced using video cameras, which can typically only be done with large movie cameras. In this way, the photographer can take video films with professional effects even without the use of expensive film material. This effect can be applied to the artistic design of a motion picture shot, especially since the depth of field can be varied over a wide range.

A disadvantage of the known image conversion system is that the light devices are arranged in a linear manner one behind the other in the light path resulting in a relatively long and heavy construction. Another characteristic of the known image conversion device is that by using another lens an additional image conversion takes place in the main image plane. Basically, this can be compensated in a relatively simple manner by using suitable rendering software. But since commercially available video cameras are not available, it has been proposed (EP0950912a2) to use an inverting prism arrangement in the light path, which may be arranged before or after the intermediate image plane. However, the structural length and/or weight of the image conversion light device cannot be reduced significantly with this arrangement either.

Starting from this, the invention is based on the task of improving a known image conversion system of the type mentioned above, such that the structural length can be significantly reduced while maintaining the same optical properties.

To accomplish this task, a combination of the features of claims 1 and 29 is proposed. Advantageous embodiments and further developments of the invention are indicated in the dependent claims.

The technical solution according to the invention is mainly based on the following ideas, namely: by suitably including a prism light path having a refractive index greater than that of air, and by deviating from the light path of the prism device, the length of the image conversion system can be significantly reduced. In order to achieve this, it is proposed according to the invention that the projection disk is arranged in an intermediate space between two prism faces in the prism arrangement, which face each other and are parallel to each other.

According to a preferred embodiment of the invention, the projection disc is located in a plane within the prism arrangement, which plane is parallel to the optical axis of the recording lens and/or the image conversion lens, and whose broadside surfaces are parallel to each other. It is particularly advantageous that the recording lens and the image conversion lens are axially parallel to each other, so that a substantially coaxial orientation can be achieved.

In a preferred embodiment of the invention, the prism device is configured as an optical image conversion unit as a whole. In this connection, it is of practical significance that at least some of the prisms in the prism arrangement are combined into a prism block (prism block), thereby providing the projection disc with a gap defined by two prism faces. In order to avoid smearing in the area of the intermediate image plane, it is particularly advantageous if at least one broad-side surface of the projection disk is glued or glued to the adjacent prism surface.

The projection disc may be configured as a matrix disc or a fiber disc. In the latter case, the fiber optic tray has a plurality of optical fibers arranged adjacent to one another parallel to the optical path, the length of which is truncated to the thickness of the tray. In order to avoid interference light, it is of practical significance that the optical fibers of the fiber tray are shielded to prevent lateral scattering of light. In practical terms, the optical fibres form a surface grid within the projection disc, and they are preferably formed of glass fibres having a light-transmissive glass core and a thin-walled cladding glass of lower refractive index, and an embedded black glass bundle. Advantageously, the diameter of the optical fibre is less than 0.01mm, preferably less than 0.006 mm. It is of practical significance that the broadside surface of the projection disk is polished to a high degree of sparkle. The high flash polishing of the fiber end face reduces the spectral transmission over the broad face of the projection disk to nearly the level of fresnel reflection loss.

In order to enhance the light output in the prism beam path, it is proposed according to a preferred embodiment of the invention that at least one convex lens is arranged in the beam path before and/or after the projection disk. The convex lens may be configured as a plano-convex lens or a biconvex lens, or as an achromatic lens. In this regard, the at least one convex lens may be disposed at different points in the optical path:

-directly at free space in front of and/or behind the projection disc;

-in a free space between two mutually facing and parallel prism faces in the prism arrangement;

-in a free space between the recording lens and the prism surface of the prism arrangement.

It has proved advantageous if the focusing width of the convex lens in the light path before the projection disc is approximately 1/4 of the straight-line viewing distance between the recording lens and the projection disc. On the other hand, the focusing width of the convex lens located behind the projection disk in the optical path should be 1/4 of the straight-line visual distance between the projection disk and the image conversion lens.

The use of an additional convex lens in the light path has proven to be advantageous, in particular when using a fiber optic disk as projection disk, since image transmission can be achieved with a projection disk with large edges and a sharp contour.

According to a preferred embodiment of the invention, the prism assembly with the projection disc is arranged in an adapter housing having an optical connector and a mechanical connector for connecting the recording lens and the video camera, respectively. In this connection, it is of practical significance that the recording lens is configured as an interchangeable lens for a standard film camera or a still camera. In particular, interchangeable lenses for 16mm, 35mm or 70mm film cameras or miniature cameras may be used.

In a further advantageous embodiment of the invention, the lens of the video camera forms the image conversion lens and a digital image receiver, preferably configured as a CCD sensor field, is arranged in the second image plane in the video camera.

It is a further feature of the invention that the image size and/or format of the real master image in the second image plane is different from the real intermediate image in the first image plane. Further, an optical device for distortion format change may be provided in the optical path, so that an image processing software supporting reproduction having a program for compensating for the distortion format change is additionally provided. In this way, it is possible to optically switch between a standard image format and a wide screen image format (e.g. 4: 3/16: 9). The optical means for anamorphic image conversion may be disposed in the prism means in the optical path, preferably behind the projection disk. They may be formed, for example, by intersecting cylindrical lenses or appropriate prism bases within a prismatic device. The optical means for anamorphic image conversion may also be provided within an image conversion lens, which is preferably configured as an interchangeable lens.

In the case of a relatively simple projection disk, the light path is always interrupted by a malfunction. This leads to errors in the intermediate images, which also occur during the imaging process at the second image plane. In order to eliminate such system errors, it is advantageous to arrange the projection disk crosswise to the beam path or in a rotating manner, wherein it is realistic to execute an oscillating movement. The rotating or displacing means used for this purpose are configured, for example, as an oscillator mechanically coupled to the projection disk. In this regard, the mechanical vibration amplitude of the oscillator should be greater than the diameter of the optical fiber within the projection disk.

It is of practical significance that the main components of the image conversion system according to the invention are combined into an adapter to be arranged in front of a video camera, which adapter according to the invention has an adapter housing, a prism arrangement located in the adapter housing, a projection disc located in the interspace between two mutually facing prism faces of the prism arrangement, a connection opening for connecting the lenses of the video camera, and a connection opening for the recording lens. It is therefore of practical significance that the image conversion system according to the invention is used in connection with a video camera, the lens of which constitutes the image conversion lens, and the image receiver of which is arranged on the second image plane. The recording lens is configured as an interchangeable lens for a film camera or a still camera. Preferably, a 35mm cinematographic camera interchangeable lens is used. However, other standard format interchangeable lenses, such as lenses for 16mm or 70mm film cameras, or for miniature cameras, may also be advantageously used.

The invention will be described in detail below with the aid of exemplary embodiments that are briefly illustrated in the drawings. As shown in the figure:

FIG. 1 is a schematic diagram of an optical image conversion system for a video camera;

FIGS. 2a to c three side views of the image conversion system according to FIG. 1;

FIG. 3 is a top view of an enlarged representation of a projection disk of the image conversion system;

FIG. 4 is a diagram of a moving projection disk for eliminating pass-through errors;

FIGS. 5a to c show three side views of an improved image conversion system compared to FIGS. 2a to c, with two convex lenses in the optical path;

FIGS. 6a to c are illustrations of an improved image conversion system with two convex lenses according to FIGS. 5a to c;

FIGS. 7a to c are three side views of an improved image conversion system having a convex lens in the optical path;

FIGS. 8a to c three side views of another image conversion system having a convex lens;

FIGS. 9a to c three side views of an improved image conversion system with two convex lenses;

the image conversion system shown in the figure can be used for a video camera. This ensures that commercially available camera lenses can be used to produce high quality lens images at the image plane of the video camera, with depth of field that can be adjusted within wide limits.

The optical image conversion system includes a recording lens 10 directed toward the object for producing a real intermediate image of the object having a defined image size and depth of field on a light-transmissive projection disk 14 defining a first image plane 12. An image conversion lens 16, which is located behind the recording lens 10 in the optical path 13 towards the rear of the projection disk 14, is used to generate a real main image on a second image plane 18, which has been changed in image size and/or format compared to the intermediate image. In addition, a prism arrangement 20 for performing image conversion is also located in the optical path 13 and has an input prism 22 facing the recording lens via an input window 21, a deflection prism coupled to an output window 26 of the input prism 22 via an interspace 24, and an output prism 32 coupled to the deflection prism 26 via an input window 28 thereof and facing the image conversion lens 16 via an output window 30 thereof. The prisms 22, 26 and 30 may be combined with each other, or at least partially combined, to form a prism body. The projection disc 14 is located in a space 24 between two mutually facing and mutually parallel prism faces in the prism arrangement 20. As shown, and particularly in fig. 2b, the broadside surfaces 34', 34 "of projection disk 14 are parallel to each other, which in prism arrangement 20 lie in a plane parallel to optical axis 36 of recording lens 10 and optical axis 38 of image conversion lens 16. The prism device is mainly used for image conversion and is used for shortening the length of an adapter of an image conversion system. As shown in fig. 2b and 2c, the optical axes 36, 38 of the recording lens 10 and the image conversion lens 16 are parallel to each other.

Basically, the projection disc can be configured as a matte disc. In a preferred embodiment of the invention, the projection disk is configured as a fiber optic disk having a plurality of optical fibers 40 arranged adjacent to one another parallel to the optical path 13, the length of which is truncated to the thickness of the disk. Optical fibers 40 form a surface grid within projection disk 14 (fig. 3). It is of practical significance that they are composed of glass fibers having a light-transmissive glass core 42 and a thin-walled cladding glass 44 of lower refractive index. The clad glass cannot be too thin in order to have a low loss of total reflection. On the other hand, in the case of thicker cladding glass, the packing density is lower, which leads to limited optical resolution. However, by means of the embedded black glass 45 between the coherent fiber bundles, the wall thickness of the cladding glass used can be significantly reduced. An increase in packing density results in a significant increase in optical resolution. The diameter of the optical fiber is about 0.006mm, so that overall high resolution can be obtained in the imaging process. Nevertheless, there is a risk that defects in the surface grid will cause systematic image errors in the second image plane 18. To eliminate image errors, it may be advantageous to have the projection disk 14 undergo an oscillating or rotating cross-motion (arrows 46, 48, 50) relative to the optical path 13 while the capture is taking place. For this purpose, projection disk 14 may be mechanically coupled to an oscillator, not shown in the figures.

In a second image plane disposed within the video camera, there is a semiconductor area image receptor (52) configured as a CCD.

The exemplary embodiments shown in fig. 5a, b, c to 9a, b, c differ from the image conversion system shown in fig. 2a to c in that at least one convex lens 53, 54, 55 and 56 is additionally provided in the optical path of the optical image conversion system. These convex lenses are mainly to ensure an enhanced light output within the light path. On the other hand, these convex lenses have the effect of enhancing the shooting quality of the edge and contour definition of the second image, and the degree of freedom of granularity.

In the case of the exemplary embodiment shown in fig. 5a to c, the first convex lens 53 is located in the free space between the recording lens 10 and the prism face 21 on the input side of the prism arrangement 20, while the second convex lens 54 is located in the free space between two prism faces facing each other and parallel to each other in the prism arrangement 20. The optimum focal width of lens 53 is 1/4 of the distance between recording lens 10 and projection disc 14, while the focal width of lens 54 is 1/4 of the distance between projection disc 14 and image conversion lens 16.

In the case of fig. 6a to c, a very compact arrangement is obtained in which the convex lenses 55, 56 are respectively located in front of and behind the projection disc 14 in the common interspace 24 between two mutually facing and parallel prism faces of the prism arrangement 20.

In the case of the exemplary embodiments of fig. 7a to c to 8a to c, one of the lenses shown in fig. 6a to c, respectively, is omitted, so that only one lens 56 or 55, respectively, is located together with the projection disk 14 in the interspace 24 between the two prism faces.

The exemplary embodiment shown in fig. 9a to c is a modification of the exemplary embodiment shown in fig. 5a to c, in which second lens 56 is placed in a common interspace 24 together with projection disc 14.

In summary, the following technical solutions are proposed: the present invention relates to an optical image conversion system for a video camera. The image conversion means comprises an object-facing recording lens 10 for producing a real intermediate image of the object with a defined image size and depth of field on a light-permeable projection disc 14 defining a first image plane 12. In addition, the image conversion system comprises an image conversion lens 16 arranged behind the recording lens 10 on the optical path 13, facing the rear side of the projection disc 14, for generating a real main image of the object on a second image plane 18, and a prism arrangement 20 located in the optical path 13. In order to achieve a compact construction of the image conversion system, it is proposed according to the invention that the projection disk 14 is located in a gap 24 between two mutually facing and mutually parallel prism faces in the prism arrangement.

Claims (52)

1. An optical image conversion system having an object-oriented recording lens (10) for producing a real intermediate image on a first image plane (12) with a defined image size and depth of field; having an image conversion lens (16) arranged behind the recording lens (10) in the optical path (13) and facing the first image surface (12) for generating a real main image of the object on a second image plane (18); and a prism device (20) arranged in the beam path (13), wherein a light-permeable projection plate is arranged on the first image plane (12), characterized in that the projection plate (14) is arranged in an intermediate space (24) between two prism surfaces facing each other and parallel to each other in the prism device (20).

2. An image conversion system as claimed in claim 1, characterized in that the projection discs (14) are located in a plane parallel to the optical axis (36) of the recording lens (10) in the prism arrangement (20), the broad surfaces (34', 34 ") of said projection discs being parallel to each other.

3. An image conversion system as claimed in claim 1 or 2, characterized in that the projection disc (14) is located in a plane of the prism arrangement (20), said plane being parallel to the optical axis (38) of the image conversion lens (16), the broad surfaces (34', 34 ") of said projection discs being parallel to each other.

4. An image conversion system as claimed in any one of claims 1 to 3, characterized in that the prism device (20) is configured as an optical inversion unit.

5. An image conversion system as claimed in any one of claims 1 to 4, characterized in that at least some of the prisms (22, 26, 32) of the prism means are combined into a prism body.

6. The image conversion system of claim 5, wherein the prism body has a void (24) defined by two prism faces for receiving the projection disk (14).

7. An image conversion system as claimed in any one of claims 1 to 6, characterized in that the broad-side surface of the projection disk (14) is polished to a high degree of glare.

8. An image conversion system as claimed in any one of claims 1 to 7, characterized in that at least one of the broadside surfaces (34', 34 ") of the projection disc (14) is glued or bonded to an adjacent prism face.

9. The image conversion system according to any of claims 1 to 8, characterized in that the recording lens (10) and the image conversion lens (16) are axially parallel to each other.

10. The image conversion system according to claim 9, characterized in that the recording lens (10) and the image conversion lens (16) are coaxially oriented.

11. An image conversion system as claimed in any one of claims 1 to 10, characterized in that the projection disc (14) is configured without an optical disc.

12. An image conversion system as claimed in any one of claims 1 to 10, characterized in that the projection disc (14) is configured as a fiber optic disc having a plurality of optical fibers (40) arranged close to each other parallel to the optical path, the length of which is cut to the thickness of the disc.

13. The image conversion system of claim 12, wherein the optical fibers (40) of the projection disk (14) are shielded to prevent laterally scattered light.

14. An image conversion system as claimed in claim 12 or 13, characterized in that the optical fibres (40) form a surface grid in the projection disc (14).

15. The image conversion system of any of claims 12 to 14, wherein the optical fibers (40) within the projection tray (14) are configured as glass fibers having a light transmissive glass core (42) and a thin-walled cladding glass (44) of lesser refractive index.

16. The image conversion system of claim 15, wherein black glass (45) is embedded between the glass fibers (42, 44).

17. An image conversion system as claimed in any one of claims 12 to 16, wherein the diameter of the optical fibre is less than 0.01mm, preferably less than 0.006 mm.

18. Image conversion system according to one of claims 1 to 17, characterized in that at least one convex lens (53, 54, 55, 56) is arranged in the light path before and/or after the projection disk (14).

19. Image conversion system according to claim 18, characterized in that at least one convex lens (55, 56) is arranged directly in the free space (24) in front of and/or behind the projection disc (14).

20. An image conversion system as claimed in claim 18, characterized in that a convex lens (54) is arranged in the free space between two mutually facing and parallel prism faces in the prism arrangement (20).

21. An image conversion system as claimed in any one of claims 18 to 20, characterized in that a convex lens (53) is arranged in the free space between the recording lens (10) and the input window (21) of the prism means (20).

22. An image conversion system as claimed in any one of claims 18 to 21, characterized in that the focusing width of the convex lens (55) arranged in front of the projection disc (14) in the optical path is approximately 1/4 of the straight-line of sight between the recording lens (10) and the projection disc (14).

23. An image conversion system as claimed in any one of claims 18 to 22, characterized in that the focusing width of the convex lens (56) arranged behind the projection disc in the optical path is approximately 1/4 of the straight-line viewing distance between the projection disc (14) and the image conversion lens (16).

24. An image conversion system as claimed in any one of claims 1 to 23, characterized in that the prism means (20) and the projection disc (14) are arranged in an adapter housing having mechanical connectors for connection to the recording lens (10) and the video camera, respectively.

25. Image conversion system according to claim 24, characterized in that the recording lens (10) is configured as a commercially available interchangeable lens for a film camera or a still camera.

26. Image conversion system according to claim 24 or 25, characterized in that the lens of the video camera forms the image conversion lens (16) and that an image receiver (52), preferably configured as a CCD sensor area, is arranged in the video camera on the second image plane (18).

27. An image conversion system as claimed in any one of claims 1 to 26, characterized in that the real main image in the second image plane (18) is of a different size and/or format than the real intermediate image in the first image plane (12).

28. An image conversion system as claimed in claim 27, characterized in that optical means for distortion format change are arranged in the optical path (13) and image processing software supporting reproduction is provided, which software has a program for compensating for the distortion format change.

29. An image conversion system as claimed in claim 27 or 28, characterized in that the optical means for distortion format change are arranged in the beam path (13) in the prism means (20).

30. The image conversion system of claim 29, wherein the optical means for distorting format changes is comprised of crossed cylindrical lenses or cylindrical prism bases within the prism means.

31. An image conversion system as claimed in claim 27 or 28, characterized in that the optical means for distortion format change are arranged in an image conversion lens (16), which is preferably configured as an interchangeable lens.

32. An image conversion system as claimed in any one of claims 1 to 31, characterized in that a rotation or displacement device is engaged on the projection disc (14) for effecting a rotation or displacement movement across the optical path.

33. An image conversion system as claimed in claim 32, characterized in that the rotating or displacing means are configured as an oscillator mechanically coupled to the projection disc (14).

34. The image conversion system of claim 33, wherein the mechanical oscillation amplitude of the oscillator is greater than a diameter of the optical fiber within the projection disk.

35. An adapter for placement in front of a video camera having an adapter housing; having prism means (20) located within the adapter housing; a projection disk (14) which is located in a gap (24) between two mutually facing prism surfaces of the prism arrangement; a connection opening having a lens for connecting to a video camera; and a connection opening for connecting the recording lens (10).

36. An adapter as claimed in claim 35, wherein said prism means (20) constitutes an inverting unit.

37. An adapter as claimed in claim 35 or 36, characterized in that at least some of the prisms (22, 26, 32) of the prism arrangement (20) are combined into one prism body.

38. The adapter of claim 37 wherein said prism body has a void defined by two prism faces for receiving a projection disk (14).

39. An adapter as claimed in claim 38, wherein at least one broadside surface of the projection disc (14) is glued or bonded to an adjacent prism face.

40. An adapter as claimed in any one of claims 35 to 39, characterized in that the projection disc (14) is configured as a compact disc-less disc.

41. An adapter according to any of claims 35 to 40, characterized in that the projection disc (14) is configured as a fibre optic disc having a plurality of optical fibres (40) arranged adjacent to each other parallel to the optical path (13), the length of which is cut to the thickness of the disc.

42. An adapter as claimed in claim 41, characterized in that the optical fibres (40) of the projection disc (14) are shielded against laterally scattered light.

43. An adapter as claimed in claim 41 or 42, characterized in that the optical fibres (40) constitute a surface grid in the projection disc (14).

44. An adapter as claimed in any one of claims 41 to 43, wherein the optical fibre (40) within the projector disc (14) is formed from a glass fibre having a light-transmissive glass core (42) and a thin-walled cladding glass (44) of lower refractive index.

45. An adapter as claimed in claim 44, wherein the black glass (45) is embedded between the glass fibres of the projection disc (14).

46. An adapter according to any of claims 42 to 45, wherein the diameter of the optical fibre (40) is less than 0.01mm, preferably less than 0.006 mm.

47. An adapter as claimed in any one of claims 35 to 46, characterized in that at least one convex lens (53, 54, 55, 56) is arranged in front of and/or behind the projection disc (14) in the prism arrangement.

48. Adapter as claimed in claim 47, characterized in that at least one convex lens (55, 56) is arranged directly in the free space (24) in front of and/or behind the projection disc (14).

49. An adapter as claimed in claim 47 or 48, characterized in that a convex lens (54) is arranged in the prism arrangement in a free space between two mutually facing and parallel prism faces.

50. An adapter as claimed in any one of claims 47 to 49, characterized in that at least one convex lens (53) is arranged in the adapter housing in front of the prism means (20).

51. Use of an optical image conversion system according to any one of claims 1 to 34 in connection with a video camera, wherein the lens of the video camera forms the image conversion lens (16) and the image receiver (52) of the video camera is arranged in the second image plane (18).

52. Use according to claim 51, characterized in that the recording lens (10) is configured as a commercially available interchangeable lens for film cameras or still cameras.