RU2464608C1 - Optical system for holographic video camera - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: optical system for a holographic video camera includes an optical waveguide with an input holographic element on its surface, a lens, a visible radiation detector, an infrared radiation detector and a photoelectric converter connected to said detectors. The input holographic element is configured to split input radiation into visible and infrared parts. The optical waveguide is configured to transfer the visible part of radiation towards the visible radiation detector and the infrared part towards the infrared radiation detector. The lens is configured to form an image of an object through the optical waveguide and the holographic element on the detector. The photoelectric converter is configured to determine the phase difference between output signals, which are radiation intensity distribution in images obtained from visible and infrared radiation detectors.

EFFECT: possibility of using a single lens for infrared and visible radiation, possibility of remote formation of a depth map in order to form a pseudo three-dimensional image.

9 cl, 6 dwg

Description

The invention relates to a technology for the construction of high-resolution video cameras, in particular, to the creation of optical systems for holographic video cameras operating in low light conditions.

Most of the well-known optical systems for video cameras, which allow obtaining high-quality color images in low light conditions or constructing a pseudo-three-dimensional image, are based on a combination of two separate channels for visible and infrared radiation, respectively. Many of these optical systems use complex lenses, in which part of the lenses is used only for focusing visible radiation, and the other part is only for focusing infrared radiation. Other modifications of optical systems for video cameras operating in difficult conditions are based on a single lens and a system of reflective mirrors.

A camera is known from the prior art (see US Patent Application Laid-Open No.2010,00066854) [1], capable of creating a depth map for constructing pseudo-three-dimensional images, including an imaging system having a first depth of field for one or more first colors and a second the depth of the sharply depicted space, less than the first, for one or more second colors. The imaging system may include an iris with a first aperture for the first color or colors and a second aperture larger than the first for the second color or colors. The first aperture can be defined by the outer dark ring (1), and the second by the inner color ring (2). The inner ring (2) blocks the first color (a) and skips the second color (a). The image formed by the first ring is sharper, and its sharpness can be reproduced by processing other images.

An optical system is also known in the art (see US Pat. No. 6,870,690) [2] based on the use of a single lens or optical system for imaging in two different optical ranges. A single lens or optical system is used for an image formed in two different spectral ranges, for example in the ranges of visible and infrared light. A dual-band singlet is formed from the first, larger optical element used to work with the first spectral range. The smaller element is used to work with the second spectral range and inside the aperture, cutting it from the first component, thus forming a dual-band singlet that can operate at two different wavelengths.

US Published Patent No. 5212375 [3] proposes a system for determining the focus of a digital camera based on a holographic light beam splitter. In this, closest to the claimed invention, the system provides for the presence of at least one holographic element located on the optical path of the photographic lens; such an element serves to separate the radiation into several different beams, one of which enters the imaging detector of the video camera, and at least one of the remaining beams enters the detector for focusing.

The holographic optical element (hereinafter referred to as the GOE), depending on the diffraction function of the hologram, is used as a lens, mirror, beam splitter, etc. Since the GOE works only to record the interference pattern of light beams in a thin plane, its structure and principle of operation are very simple, namely, two radiation beams passing through different regions of the optical system are separated in different directions of a single GOE located closer to the object than primary image plane, for the formation of two images on radiation receivers. Focusing is carried out by determining the phase difference between the output signals received from the radiation receivers. This allows you to get rid of several additional elements, such as a field diaphragm, a condenser lens, a mirror, aperture diaphragm. This simplifies the design of the camera and makes it more compact.

It should be noted that the GOE, which can be formed on various plastics, are cheap and simple in structure. Thus, the low cost and simplicity of the structure of a single GOE makes it possible to use it to separate the light beam into a photographic system and a focusing system, and also allows focusing during the photographing process.

The problem to which the claimed invention is directed is to develop a more compact, easy-to-manufacture and lightweight optical system for a video camera, in which a single lens can be used for visible light and infrared light, and a depth map can be created to create a pseudo-three-dimensional image remotely.

The technical result is achieved through the development of an improved optical system for a holographic video camera, while such a system includes:

- at least one optical waveguide with at least one introducing holographic element on its surface;

- at least one lens;

- detector for visible radiation;

- detector for infrared radiation;

- a photoelectric transducer connected to a detector for visible radiation and a detector for infrared radiation;

moreover, the distinguishing features of this design are that

- the introducing holographic element is configured to separate the incoming radiation into the visible and infrared parts;

- the optical waveguide is configured to transfer the visible part of the radiation in the direction of the detector for visible radiation and the infrared part of the radiation in the direction of the detector for infrared radiation;

- the lens is configured to form an image of an object through an optical waveguide and a holographic element on the detector;

- the photoelectric converter is configured to record the phase difference between the output signals, which are the distribution of radiation intensity in the images obtained from the detectors for visible and infrared radiation.

The essence of the claimed invention is further illustrated with the use of graphic materials, which show:

Figure 1. The structure of the claimed invention (introducing a holographic element and a detector for infrared radiation are located directly on one of the optical elements of the lens)

Items:

10 - common lens

20 - lens for visible radiation

30 - detector for visible radiation

50 - detector for infrared radiation

60 - optical waveguide

80 - introducing a holographic element.

Figure 2. The structure of the claimed invention (electrically controlled input holographic element)

Items:

10 - common lens

20 - lens for visible radiation

30 - detector for visible radiation

50 - detector for infrared radiation

60 - optical waveguide

80 - introducing holographic element

140 - diffraction efficiency control module.

Figure 3. The structure of the claimed invention (introducing a holographic element located directly on one of the optical elements of the lens)

Items:

10 - common lens

20 - lens for visible radiation

30 - detector for visible radiation

40 - lens for infrared radiation

50 - detector for infrared radiation

80 - introducing a holographic element.

Figure 4. The structure of the claimed invention (the introducing holographic element is located directly on one of the optical elements of the lens and the detector for infrared radiation has a high resolution)

Items:

10 - common lens

20 - lens for visible radiation

30 - detector for visible radiation

40 - lens for infrared radiation

50 - detector for infrared radiation

80 - introducing a holographic element.

Figure 5. The structure of the claimed invention (additional infrared illumination)

Items:

10 - common lens

20 - lens for visible radiation

30 - detector for visible radiation

40 - lens for infrared radiation

50 - detector for infrared radiation

80 - introducing holographic element

120 - holographic structured backlight element

130 - infrared laser.

6. The structure of the claimed invention (with reflective introducing holographic element)

Items:

10 - common lens

20 - lens for visible radiation

30 - detector for visible radiation

40 - lens for infrared radiation

50 - detector for infrared radiation

150 - reflective input holographic element.

A holographic video camera consists of: an optical waveguide with holographic optical elements deposited on its surface, which ensure separation of the incoming radiation into the visible and infrared parts; a common optical lens transmitting input radiation from the input of the system to the optical waveguide; a lens for visible radiation, which forms an image on a detector for visible light, and a lens for infrared radiation, which forms an image on a detector for infrared radiation. Holographic optical elements are selected of the reflective or transmission type with electrically or optically controlled diffraction efficiency and selectivity.

The common lens 10 projects the input image into a plane transmitting or reflecting, introducing a holographic element 80. Depending on the design, introducing holographic elements transmitting or reflecting for the corresponding wavelength are located, for example, on the surface of the optical waveguide 60 (Figure 1). Depending on the wavelength, the introducing holographic elements 80 introduce the input radiation into the optical waveguide.

A preferred embodiment of the system is to position the introducing topographic element 80 on the surfaces of the lens (FIG. 1). In this case, there is no need to use a special waveguide board, its role is played directly by one of the objective lenses. For visible and infrared, elements of a common lens are used. The infrared detector 50 may also be located directly on the surface of the common lens 10.

As the introducing holographic element 80, a hologram with controlled efficiency (for example, an electrically controlled hologram) can be used (Figure 2). In this case, the degree of refraction of the radiation is controlled by a special diffraction efficiency control module 140.

An example implementation of an optical system in a holographic video camera is shown in Figure 1. The holographic video camera contains an optical waveguide 60, introducing a holographic element 80, which divides the input radiation transmitted through the common lens 10, into the visible and infrared parts. The lens 20 for visible radiation focuses the visible part of the input radiation to the detector 30 for visible radiation, while the common lens 10 focuses the infrared part of the input radiation on the detector 50 for infrared radiation.

The incoming radiation, which includes visible and infrared components, passes through a common lens 10 and comes to an optical waveguide 60 with an input holographic element 80 on its surface. The introducing holographic element 80 has zero optical power for the visible radiation that passes through it, and, focusing with the lens 20 for visible radiation, enters the detector 30 for visible radiation. Infrared radiation is reflected from the introducing holographic element 80. Propagating in the optical waveguide 60, infrared radiation is incident on the infrared radiation detector 50.

The introducing holographic element 80 is located on the surface of one of the lenses of the lens 10 so that the incoming radiation diffracts on it, leading to the appearance of waveguide modes inside the lens, while the radiation of a certain wavelength, in this case the infrared radiation, is separated from the incoming radiation and detected by the detector 50 for infrared radiation and is not detected by the detector 30 for visible radiation.

The scheme allows the use of various types of introducing holographic elements - reflective type, transmission type, or a combination thereof.

Figure 2 shows an alternative system. The system operates as follows: the incident light diffuses on the input holographic element 80, which is made in the form of an electrically controlled holographic element and connected to the diffraction efficiency control module 140. This solution allows you to increase the efficiency of separation of infrared radiation. Moreover, the specified input holographic element 80 can also be made in the form of a set of electrically controlled holograms, each of which can operate in a separate spectral range. Thus, the diffraction efficiency control module 140 can select a spectral range necessary for operation.

Figure 3 shows another version of the system where high quality infrared channel is achieved by using special image processing.

The embodiment of the system shown in FIG. 4 is characterized in that it comprises an infrared channel with a high resolution detector and image quality identical to the visible channel.

5 shows an embodiment of a system with a illuminator for creating a depth map for a pseudo-three-dimensional image. The illuminator comprises an infrared laser 130 and a holographic structured backlight element 120 that forms stripes in the plane of the object. The illuminator illuminates the object through a holographic structured backlight element, and the image shift of the bands on the detector for infrared radiation determines the depth map of the object.

Figure 6 shows a variant of a system where an input holographic element of a reflective type is used to increase the efficiency and selectivity of the infrared channel.

All described variants of the system are connected by a single inventive concept and are designed to solve the same problem.

From the above examples it is seen that there are various options for implementing the basic concept embodied in the claimed invention.

In particular, it makes sense that in the inventive optical system the optical waveguide was made with an infrared radiation detector placed on its surface, and the lens would be made in the form of a lens for visible radiation, capable of forming an image of an object through an optical waveguide and introducing a holographic element on the detector for visible radiation.

It also makes sense that in the inventive optical system the function of the optical waveguide is performed by a common lens, configured to transfer the visible part of the radiation in the direction of the lens for visible radiation and image formation of the object on the detector for infrared radiation.

In another embodiment, it is proposed that the common lens be provided with an input holographic element on its last surface, and such a lens is configured to transfer the visible part of the radiation in the direction of the lens for visible radiation and the infrared part of the radiation in the direction of the lens for infrared radiation.

Another option provides that the inventive optical system further includes:

- holographic structured backlight element,

- infrared laser, and

- holographic structured backlight element is configured to form a strip in the plane of the object;

- the infrared laser is configured to illuminate the object through a holographic structured backlight element.

It should be noted that the introducing holographic element can be implemented in various ways, for example, it can be made as a reflective element, or made as an electrically controlled topographic element and connected to a diffraction efficiency control module, or made as a set of electrically controlled holographic elements, each of which is configured to operate in a separate spectral range.

In addition, in some embodiments of the inventive optical system, the detector for visible radiation and the detector for infrared radiation can be made in the form of matrices.

It should also be noted that since the zeroth order of the radiation transmitted through the SEE gives a small chromatic aberration, it is desirable that the photographic optical system has a small chromatic aberration margin.

The inventive optical system can be effectively used in video cameras that provide high-quality color images in low light conditions.

Claims (9)

1. The optical system of a holographic video camera, including,
- at least one optical waveguide with at least one introducing holographic element on its surface;
- at least one lens;
- detector for visible radiation;
- detector for infrared radiation;
- a photoelectric converter connected to a detector for visible radiation and a detector for infrared radiation, characterized in that
- the introducing holographic element is configured to separate the incoming radiation into visible and infrared parts;
- the optical waveguide is configured to transfer the visible part of the radiation in the direction of the detector for visible radiation and the infrared part of the radiation in the direction of the detector for infrared radiation;
- the lens is configured to image an object through an optical waveguide and a holographic element on the detector;
- the photoelectric converter is configured to record the phase difference between the output signals, which are the distribution of radiation intensity in the images obtained from the detectors for visible and infrared radiation. 2. The optical system according to claim 1, characterized in that the optical waveguide is made with an infrared radiation detector on its surface, and the lens is made in the form of a lens for visible radiation, capable of imaging an object through an optical waveguide and introducing a holographic element on the detector for visible radiation . 3. The optical system according to claim 2, characterized in that the function of the optical waveguide is performed by a common lens, configured to transfer the visible part of the radiation in the direction of the lens for visible radiation and image formation of the object on the detector for infrared radiation. 4. The optical system according to claim 3, characterized in that the common lens has an input holographic element on its last surface and is configured to transfer the visible part of the radiation in the direction of the lens for visible radiation and the infrared part of the radiation in the direction of the lens for infrared radiation. 5. The optical system according to claim 4, characterized in that it further includes: a holographic structured backlight element, an infrared laser, wherein the holographic structured backlight element is configured to form a strip in the plane of the object; an infrared laser is configured to illuminate an object through a holographic structured backlight element. 6. The optical system according to claim 2, characterized in that the introducing holographic element is made as reflective. 7. The optical system according to claim 2, characterized in that the introducing holographic element is made in the form of an electrically controlled topographic element and is connected to a diffraction efficiency control module. 8. The optical system according to claim 2, characterized in that the introducing holographic element is made in the form of a set of electrically controlled holographic elements, each of which is configured to operate in a separate spectral range. 9. The optical system according to any one of claims 1 to 3, characterized in that the detector for visible radiation and the detector for infrared radiation are made in the form of matrices.

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