FR2536616A1 - IMAGE ANALYZING DEVICE FOR COLOR TELEVISION CAMERA - Google Patents

Abstract

THE INVENTION RELATES TO AN IMAGE ANALYZER DEVICE FOR A COLOR TELEVISION CAMERA. THE ANALYZER INCLUDES AN OPTICAL BLOCK PB WITH A NEAR INFRARED ABSORPTION FILTER A TO ELIMINATE INFRARED LIGHT NEAR LIGHT RAYS FROM OBJECTIVE 8 IN ORDER TO AVOID UNDESIRABLE PHENOMENA SUCH AS THE APPEARANCE OF REFLECTIONS GHOST IMAGES. THE INVENTION APPLIES TO COLOR TELEVISION CAMERAS.

Description

IMAGE ANALYZING DEVICE FOR A CAMIERA OF

TELEVISION IN COLORS

  The invention relates generally to image analyzer devices for a color television camera and more particularly relates to an improvement in the optical system of such an image analyzer device comprising a photoelectric forming device. images mounted on a transparent plate when a color separator filter

inorganic type is provided.

  Television image analyzer devices

  color image having a photoelectric conversion device provided on a transparent plate, in which the photoelectric conversion device is provided with a color separator filter for the image analyzer device to produce a color video signal, have been developed and are already on the market as is well known because the optical system is simple and compact and lightweight image analyzer devices are easy to manufacture Examples of such image analyzer devices are in television cameras having a tube an analyzer having an image forming device provided on a faceplate and with a color separator filter for producing a color video signal and a single plate television camera having a color analyzer

  semiconductors with a photo conversion device

  electrical and a color separator filter in order to

  produce a video signal in color.

  In image analyzers of color television cameras, it is necessary to produce a color video signal which reproduces

  high quality images on a cathode ray tube.

  In this respect, when unnecessary reflections occur in an optical system of such an image analyzer, reflections may occur, which results in a reproduced image of poor quality In order to overcome this defect, different countermeasures have been taken so far

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in current analyzers.

  But in image analyzers equipped with an inorganic-type color separator filter that separates incoming light rays into multiple colors so that a multiple color video signal can be produced, since the inorganic separator filter reflects light rays that have wavelengths that can not be transmitted by the filter, a large amount of reflected light rays can be

  reflected several times in a trans-

  parent of the photo conversion device

  electrical, or are reflected to the input lens of the optical system first, before these rays are

  applied to the photoelectric conversion device.

  The result is undesirable phenomena such as the appearance

  reflections or ghost images These phenomena are

  particularly noteworthy when a subject emitting light rays, including light in a relatively long wavelength band, such as the flame of a candle, is analyzed by a television camera having an image forming device of the aforementioned type In other words, this light in the band of long wavelengths repeats reflections without being very attenuated, and consequently, if a candle flame is analyzed, reflections and ghost images

  occur around the flame, which deteriorates considerably.

  the quality of the image reproduced.

  The object of the invention is therefore to remedy the aforementioned drawbacks inherent in an analyzer

images of the current type.

  An object of the invention is to propose a new image analyzer device for suppressing the appearance of unwanted multiple reflections of near infrared light rays in a system.

optical.

  According to a characteristic of the invention, an optical unit comprising a near infrared absorption filter is stuck on a front plate which constitutes

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  a photoelectric conversion part of the image analyzer so that light rays transmitted by a lens are applied to the front plate after propagating in the optical unit Since the optical unit is stuck on the surface of the front plate, some light rays that are reflected by a color separator filter provided on the other surface of the faceplate are directed towards the periphery of the

  optical block, which reduces unwanted light rays.

  The invention therefore relates to a device

  color television image processor for a color television camera, said image analyzer device having a lens, a photoelectric conversion portion including a transparent faceplate, a line-like color splitter filter, and a device forming color television images responsive to the light rays applied thereto by said lens via the faceplate and the color separator filter by producing a color video signal, and an optical block with a color filter; near-infrared absorption, this optical block being placed between the objective and the front plate so that a surface of the optical block is glued on a

front plate surface.

  Other features and benefits of

  the invention will become apparent during the description which

  FIGS. 1 is a longitudinal section of a first embodiment of the invention. FIG. 2 is a graphical representation that is suitable for understanding the optical characteristics. FIG. the near-infrared absorption filter used in the first embodiment,

  Figure 3 is a schematic longitudinal section

  tudinal of a second embodiment of the invention,

  Figure 4 is a schematic longitudinal section

  tudinal of a third embodiment of the invention,

  Figure 5 is a schematic longitudinal section

  4 is a diagram illustrating the operation of the embodiments of the invention; FIG. 7 is a diagram showing the path of the light rays in the optical block of FIG. 2, and,

  Figure 8 is a schematic longitudinal section

  tudinal of a fifth embodiment of the invention.

  In the different figures, similar or corresponding elements are designated by the same

numerical references.

  FIG. 1 schematically represents a first embodiment of the invention, in the form of a longitudinal section. In the following embodiments, the invention will be described with regard to a color television camera with a datalogger. Image

to a single tube.

  The image analyzer device of FIG. 1 comprises a reception objective 8 represented by a single lens and an image analyzer tube comprising a transparent front plate, a cylindrical tube 2, a target ring 3, an inorganic filter 4 color separator, a thin glass plate 5, a transparent signal electrode, such as a film

  of Nesa 6 and a photoelectric conversion layer 7.

  The separating filter 4, the thin glass plate 5, the elec-

  6 transparent signal trode and the photoelectric conversion layer 7 are stacked and are mounted in the tube

  cylindrical 2 whose interior is kept under vacuum.

  An electron gun, not shown, is also provided-

  in the cylindrical tube 2 to scan the photoelectric conversion coating 7 with an electron beam, the latter being deflected or concentrated by means of a set of windings, not shown, mounted around the cylindrical tube 2 It results from scanning electronic, that a color video signal is obtained at the signal electrode 6, this signal being taken as an output video signal from the color television camera The structure described above is substantially the same as that of any current image analyzer used

  in a color television camera.

  The first embodiment of an image analyzer of FIG. 1 comprises in addition to the

  described above, an optical block PB comprises

  An absorption type A filter which eliminates the near infrared More particularly the filter

  What is called hereinafter a filter of absorption of infra-

  red, or simply an IR filter, is stuck on the front surface of the plate 1 so as to be between the front plate 1 and the lens 8.

  description, the term "frontal" is used to describe

  the side closest to the subject while the word "backward" is used to designate the side

  is closest to the photoelectric conversion layer

  The filter A is made of a colored glass produced by adding phosphoric acid and copper oxide to glass. For example, a colored glass C-500 manufactured by Hoya Glass Co, may be suitable. the spectral characteristic of the near-infrared absorption filter A determines the upper transmission wavelength limit of the reproduced signal R, the half-width of the absorption filter A is designated as half of the value of the signal R , approximately 638 nm as shown in the curve of FIG.

  this embodiment, the half-width of the absorption filter

  Near-infrared A is set at about 610 nm to obtain the desired spectral sensitivity of the reproduced R signal. The infrared filter A is attached to the surface of the faceplate 2 by means of an adhesive

  transparent containing a material similar to glass.

  Although optical elements are generally

  Although this layer is not coated on the front surface of the optical block PB used according to the invention, the transmission power of the optical block PB is approximately 95% Sj. this anti-reflection layer was provided on the surface

  optical block PB, reflected light rays

  The objective lens 8 would be transmitted through the optical block PB. Since this layer is not provided according to the invention, most of the unwanted reflected light from the objective 8 is effectively reflected on the surface. front of the block

PB optics.

  The color separator filter 4 can be any known filter of a line structure, such as that described in US Pat. No. 4,041,528. The color separator filter 4 can be made by vapor deposition on the back surface of the

transparent front plate 1.

  FIGS. 3 and 4 illustrate a second and a third embodiment in which a crystal filter B is also used in addition to the infrared filter A of the embodiment so that the optical block PB comprises the near-infrared filter A and the filter In other words, in the second embodiment of FIG. 3, the crystal filter B is placed in front of the near infrared filter A which is fixed on the front plate 1 and in the third embodiment of FIG. , the crystal filter B is fixed on the front plate 1 and the infrared filter A is placed in front of the crystal filter B. In the second and third embodiments, the near-infrared filter A and the filter B crystal are superimposed and glued together by means of a suitable transparent adhesive The B crystal filter used in the second and third embodiments functions as a low pass optical filter which is gen It is usually necessary in an optical system for a color television camera of this kind using a filter

  stripe structure color separator.

  FIG. 5 illustrates a fourth embodiment in which the optical block PB comprises a single near-infrared absorption filter A, two crystal filters B and C and a quarter-wave plate D and the near infrared absorption filter A are superimposed and their set is interposed between the two crystal filters B and C. Since a fundamental wave and a second harmonic wave are used to reproduce colors in an image analyzer using a color separation line filter, the two low-pass filters, ie the crystal filters B and C and the quarter wave plate D are used to block two

wavelengths.

  In the four embodiments described above, it should be noted that the near-infrared absorption filter A is interposed between two elements.

  in the second and fourth modes of

  3 and 5 and that the two surfaces of the near-infrared absorption filter A are directly attached to the adjacent optical elements. As a result, the two surfaces of the infrared filter A are covered and therefore this structure is advantageous for the protection against moisture of the infrared filter A. In other words, since the near-infrared absorption filter A can be disturbed by a white cloud that occurs on the surface under the effect of the ambient humidity, the moisture-protective structure of the second and fourth embodiments is advantageous and therefore, long-lasting

of this filter A is assured.

  Although a filter or two crystal filters are used in the embodiments of Figures 3 to 5, diffraction grating filters may also be suitable as one or more low pass filters.

at will.

  As has been described above, thanks to the near-infrared absorption filter A provided in the optical path between the objective 8 and the front plate 1, the near-infrared light is remarkably attenuated.

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  by absorption before the light rays from a subject are received by the separator filter 4 By

  therefore, if the separating filter 4 is of an inor-

  The light rays which it reflects towards the front plate 1 of the optical block PB where the reflected light rays contain rays other than those transmitted by the block PB contain less infrared light, since The reflected light wave is limited to a range (see hatched portion in Figure 6) limited by the upper limit of green filter transmission wavelength and the cyan filter both being part of the separator filter 4, and by characteristics

  Near infrared filtered spectral spectra.

  In addition, since the infrared light

  red light among the light rays reflected by the separating filter 4 is attenuated by the near infrared absorption filter A when the reflected light rays propagate through the filter A after passing through the front plate 1, if the reflected light rays are again reflected by the objective 8-or the front surface of the optical block PB, the infrared component

  close that contain these light rays is weak.

  Among the light rays reflected by the separating filter

  4, those whose wavelength is shorter than that of the near infrared light rays are also attenuated by passing through the optical elements and when they are reflected by these elements, the degree of the rays reflected by the inorganic filter

  color separation 4 is greatly reduced.

  As described above, although the light rays returned to the objective through the front surface of the optical block PB are again reflected by the lens 8 to be transmitted to the optical block PB, part of the spokes incident on this optical block PB is reflected at the front surface of this block Therefore, although light rays that are not reflected by the front surface of the

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  Near-infrared absorption filter A may be applied to the photoelectric conversion layer 7 through the front plate 1, because these light rays necessarily pass through the infrared filter A, whose near infrared light is attenuated before

  to reach the photoelectric conversion layer 7.

  As described above, since the PB block is stuck to the front surface of the transparent face plate 1, any light beam

  reflected by the color separator filter 5 is

  turned towards the front plate 1 and is not reflected by the front surface of the latter Above "any light ray" designates the initial light rays of the image, through-the lens 8, and reflected light rays one or more times in the optical system In other words, the light rays reflected by the separator filter 4 propagate through the front plate 1 and the optical block PB Among these light rays returned to the optical block PB by the separating filter 4, some whose angle of incidence with respect to the plane of the separating filter 4 is greater

  at a predetermined value, are returned to the peripheral

  In addition, certain other light rays coming from the separating filter 4 are again reflected by the front surface of the optical block PB and, if the angle

  of incidence relative to the separating filter 4 is greater than

  at a predetermined value, its twice reflected light rays are also directed towards the periphery of the optical block PB (see dotted lines). These light rays inciding on the periphery of the block

  optical PB are considerably absorbed and consequently

  they are attenuated otherwise these light rays can be partially reflected at the

  periphery of the optical block PB to be re-applied

  4 to the separating filter 4 through the front plate 1 with their attenuated intensity. Thus, these light rays reflected at the periphery of the optical block PB have little chance of being applied.

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  to the photoelectric conversion layer 7 It appears

  as well as even if light rays reflected by the.

  separator filter 4 have a chance to be further reflected towards this filter 4, the amount of reflected light applied to the photoelectric conversion layer 7 is very small, so that this layer 7 produces an output video signal which -is hardly

  disturbed by reflections in the reproduced images.

  In FIG. 7 and FIG. 8, the indicative hatches

  when the cut is removed at the optical block PB and

  the transparent front plate 1 to simplify.

  Reference should now be made to FIG. 8 which shows a fifth embodiment of the invention. In this embodiment, the light rays propagating in the optical block PB and its periphery are effectively absorbed by a black piece. 9 This black piece 9 may be a black paint, for example Indian black, a black lacquer or the like, or a black film With this black piece 9 around the periphery of the optical block PB,

  most of the rays incident on the

  are absorbed, so that very little reflection takes place as a result of which the rays

  unwanted light towards the photo-conversion layer

  Electrical 7 are further reduced Although the fifth embodiment of Figure 8 is illustrated as an improvement of the second embodiment of Figure 3, this combination of the optical block PB and the black part 9 can also be adapted to n ' whatever

  embodiments of the invention.

  According to experiments, when the flame of a candle is received by an analyzer device

  images having the structure of the fourth embodiment of

  5, unwanted reflections are attenuated by about 10 d B in a reproduced image, displayed on a cathode ray tube, if the thickness of each of the optical elements of the PB block and the surface

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  effective scanning of the photo-conversion layer

electrical 7 are as follows.

  IR filter thickness A 1.6 mm Quarter plate thickness D 0.5 mm Crystal filter thickness B 3.244 mm Thickness of crystal filter C 1.632 mm Effective scanning surface 8.8 mm Although Embodiments above are described with respect to single-tube image analyzer devices, it is evident that the invention can also be adapted to a single-plate color television image analyzer device.

  using a semiconductor image receiver.

  Of course, various modifications can

  be brought by the person skilled in the art to the methods of

  described and illustrated by way of examples in no way

  limiting without departing from the scope of the invention.

Claims (4)

  A color television image analyzer device for a color television camera, characterized in that it comprises a lens (8), a photoelectric conversion part comprising a transparent front plate (1), a separating filter color-coded array (4) and a color television image-forming device (7) responsive to light rays applied thereto by said lens, through said front plate of said color separator filter, producing a color image signal and an optical block (PB) comprising a near infrared absorption filter (A), said optical block being placed between said objective and said front plate so that a surface of said optical block   is glued on the surface of said front plate.   2 Device according to claim 1, characterized   characterized in that said optical block also includes a crystal filter (B) adhered to said absorption filter near infrared.   3 Device according to claim 2, characterized   characterized in that said near infrared absorption filter is adhered to said front plate so as to be interposed between said front plate and said filter to crystal.   4 Device according to claim 1,   characterized in that said optical block has a power of. transmission which is about 95%.   Device-according to claim 1, characterized   characterized in that said optical block (PB) also comprises   first and second crystal filters (B, C) and a quarter-wave plate (D) adhered to said near-infrared absorption filter to form a stack, said stack of said absorption filter of near infrared and of said quarter-wave plate is interposed   between the first and the second crystal filters. 13 2536616   6 Device according to claim 1, characterized in that it further comprises a part   black (9) around the periphery of said optical block.