Optical assembly for a camera having an image sensor

Abstract: The invention relates to an optical assembly for a camera comprising a colour-separation system 1 having three exit windows 3, 4 and 5. A solid-state image sensor 6, 7 and 8 is fixed in a desired position to each exit window 3, 4 and 5 by means of a holder 9, 10 and 11. Each holder 9, 10 and 11 comprises a first holder plate 12, 13, 14 having an aperture 45, 46, 47 and a second holder plate 15, 16, 17 having an aperture 48, 49, 50 and an elastically deformable element 18, 19, 20 which surrounds the apertures of a holder.

Description: The invention relates to an optical assembly for a camera comprising a colour separation system having an entrance window and at least one exit window, a solid state image sensor being fixed to the or each exit window, which solid state image sensor comprises an image-receiving surface accomodated in an envelope, the image-receiving surface being arranged relative to the corresponding exit window in a predetermined position, said position being determined by at least one element of elastically deformable material. An optical assembly of the type mentioned above is known from GB-A-2.078.935. The image-receiving surface of the solid-state image sensor of an optical assembly as mentioned in the opening paragraph is accommodated in an envelope and often the exact position of the image-receiving surface relative to the envelope is unknown. Consequently, also the position of the image-receiving surface relative to the exit window in question is not known. To obtain a properly functioning camera for television, film and photographic recordings, it is desirable for the image-receiving surface of the image sensor to be secured to the relevant exit window in this aligned position. In GB-A-2.078.935 this is obtained by inserting a flexible gasket between a detector unit and the corresponding exit face of a prism. The detector unit is then accurately positioned with respect to the exit face and the exit path axis. After positioning the gasket is impregnated to obtain a rigid bond for maintaining the predetermined proper positions of the detector unit and the prism with respect to each other. It is an object of the invention to provide an optical assembly for a camera, which enables the image sensor to be secured in advance to the corresponding exit window in an aligned position, in a simple and accurate manner. To this end, an optical assembly of the type mentioned in the opening paragraph is characterized in accordance with the invention in that the or each solid-state image sensor is fixed to the corresponding exit window by means of a holder which comprises a first holder plate having along its edges slotted elements projecting from the first holder plate, the slots of which are bounded by at least one first stop surface at the end of the slot which is farthest from the plate, and a second holder plate having along its edges second stop surfaces movable in the slots of the slotted elements, said holder plates having facing apertures, said first and second holder plates being fixed to the corresponding exit window and the solid-state image sensor respectively, and being secured to one another to maintain the predeterrmined position, the holder further comprising the element of elastically deformable material in a position in which it coöperates with and acts between the two holder plates. The invention is based on the insight that due to the use of two holder plates and an elastically deformable element which form an integrated entity and, in addition, coöperate with each other so as to enable the two holder plates to be positioned relative to one another, the image sensor can be positioned relative to the exit window and supported during the positioning operation. During positioning an initial holder assembly is used in which the holder plates are coupled loosely together. Due to the element of elastically deformation and the stop faces which coöperate in this assembly positioning of the holder plates is possible in any position wanted. After the holder assembly has been inserted between the exit window and the solid-state image sensor an image-receiving surface is oriented parallel to the exit window after which the holder plates are rigidly secured. Securing of the holder plates can be carried out rapidly. The invention is based on the insight that due to the use of two holder plates and an elastically deformable element which form an integrated entity and, in addition, cooperate with each other so as to enable the two holder plates to be positioned relative to one another, the image sensor can be positioned relative to the exit window and supported during the positioning operation. From EP-A-0231382 it is known per se to secure a holder of iron or a similar material to both the image sensor and the relevant exit window, and solder both holders to one another in an aligned position. However, during the positioning of the holders described in the said Application they do not form an integrated entity which supports the image sensor, and cooperation between the holders, enabling them to be positioned relative to each other, is not suggested. A preferred embodiment of an optical assembly in accordance with the invention is characterized in that the elastically deformable element, when viewed in directions perpendicular to the holder plates, surrounds the apertures in the holder plates of the associated holder. Since the elastically deformable element surrounds the apertures, the holder plates can be tilted in any desired position relative to one another in a simple, defined manner, so that the image-receiving surface of the image sensor can be placed in any desired position relative to the relevant exit window. Alternative embodiments of an optical assembly in accordance with the invention are characterized in that the elastically deformable element comprises separate segments which, when viewed in directions perpendicular to the holder plates, at least partly surround the apertures in the holder plates of the associated holder, or in that the elastically deformable element comprises four separate segments which, when viewed in directions perpendicular to the holder plates, define the vertices of an imaginary rectangle which surrounds the apertures in the holder plates of the associated holder. A further preferred embodiment of an optical assembly in accordance with the invention is characterized in that the first and second holder plates are secured to one another by UV-light curable adhesive. If a UV-light curable adhesive is used, the two holder plates of the solid-state image sensor can be rapidly secured to one another in the desired position, such that during the fixation any variation in the adjusted position is minimal. A further preferred embodiment of an optical assembly in accordance with the invention is characterized in that the image-receiving surface of the solid-state image sensor is substantially parallel to the exit window. Consequently, the image-receiving surface of each solid-state image sensor is sufficiently accurately positioned relative to the relevant exit window, and a camera can optimally record an image to be picked up. A method of manufacturing an optical assembly having a colour separation system for a camera, in which, during a process step, a solid-state image sensor is fixed opposite an exit window in an aligned position, is characterized in accordance with the invention in that before the solid-state image sensor is fixed opposite the exit window, a holder is formed from a first and a second holder plate and an elastically deformable element provided between the holder plates, the holder plates being tiltable relative to one another by virtue of the elastically deformable element, the solid-state image sensor is fixed to the second holder plate, the holder with the solid-state image sensor is arranged over the exit window, a test pattern is imaged on the entrance window of the colour separation system, the first and the second holder plates are tilted relative to one another until the image sensor records a desired test pattern, and in that the two holder plates are secured to one another in an aligned position by means of a fixation element. On account of this, the solid-state image sensor can be rapidly and accurately fixed in a desired position opposite the relevant exit window. A few exemplary embodiments of an optical assembly in accordance with the invention will now be described with reference to the drawings, in which Figure 1 is a diagrammatic, sectional view of an optical assembly in accordance with the invention, Figure 2 is a diagrammatic, perspective view of an embodiment of a holder for an image sensor of an optical assembly in accordance with the invention, Figure 3 is a diagrammatic, perspective view of an alternative embodiment of a holder for an optical assembly in accordance with the invention, Figure 4 is a diagrammatic, perspective view of a further alternative embodiment of a holder for an optical assembly in accordance with the invention, Figure 5 is a diagrammatic, sectional view of the holder for an optical assembly, taken on the line V-V in Figure 4, Figure 6 is a diagrammatic side view of the holder for an optical assembly, viewed in the direction of the arrow VI shown in Figure 4, and Figures 7 and 8 are diagrammatic, sectional views of a solid-state image sensor fixed to an exit window. By way of example, the invention will be described by means of an optical assembly for a colour television camera having a colour separation system 1 with one entrance window 2 and three exit windows 3, 4 and 5, as schematically shown in Figure 1. A solid-state image sensor 6, 7, 8 is fixed to each exit window 3, 4, 5 by means of an associated holder 9, 10, 11. A solid-state image sensor (for example 6) generally comprises an envelope 40 containing an image-receiving surface 41 and to which connection pins 42 are secured for providing an output according to an image to be recorded. Each solid-state image sensor 6, 7, 8 is fixed to its corresponding exit window 3, 4, 5 in such a way that the image-receiving surfaces 41, 43, 44 are parallel to the exit windows. For clarity, the individual parts of the holder 9 are separately shown in Figure 1. Each holder 9, 10, 11 comprises a first holder plate 12, 13, 14 having an aperture 45, 46, 47 and is secured to the relevant exit window 3, 4, 5, and a second holder plate 15, 16, 17 having an aperture 48, 49, 50, to which plate the associated solid-state image sensor 6, 7, 8 is fixed. An elastically deformable element 18, 19, 20 is provided between each first holder plate 12, 13, 14 and each second holder plate 15, 16, 17. In the assembled state of the holder, the image sensor is brought into a desired position relative to the corresponding exit window by virtue of the cooperation of the elastically deformable element with the two holder plates of each holder. This desired position is fixed by securing the two holder plates to each other by means of a fixation element, for example an adhesive. Figure 2 is a diagrammatic view of an embodiment of a holder 51 for an optical assembly in accordance with the invention, in which an elastically deformable element 52 surrounds apertures 53 and 54 of holder plates 55 and 56. In this embodiment, the elastically deformable element 52 is a spiral-shaped spring. For clarity, the individual parts of the holder 51 are shown separately. Since the elastically deformable element 52 surrounds the apertures the holder plates 55 and 56 can be tilted relative to one another into any desired position in a simple and defined manner, as will be described hereinafter. Alternative embodiments of a holder for an optical assembly, in which the holder plates of the holder can be placed in any desired position relative to one another are shown in Figures 3 and 4. In Figure 3, the elastically deformable element 52 comprises three separate segments 57, 58 and 59 which surround the apertures 53 and 54 of the holder plates 55 and 56. In this embodiment, the separate segments 57, 58, 59 are rubber tubes. Figure 4 shows an alternative embodiment of a holder 21 for an optical assembly in accordance with the invention, in which the elastically deformable element comprises four cylindrical elements 22, 23, 24 and 25 which define the vertices of an imaginary rectangle 60 surrounding apertures 61, 62 of holder plates 26, 27. For clarity, the individual parts of the holder 21 are shown separately. The function of the elastically deformable element of the holder will be explained by means of the method of manufacturing an optical assembly for a television camera in accordance with the invention, and will be described, by way of example, with reference to the Figures 4 up to and including 8. As is shown in Figure 4, the holder 21 is formed by assembling the first holder plate 26 and the second holder plate 27 together the rubber elements 22, 23, 24, 25 being inserted between them. The holder plates 26 and 27 are loosely coupled together and are provided with respective cooperating stop surfaces 28 and 29 which, in the assembled condition, are urged against one another by the rubber elements as the diagrammatic, sectional view of Figure 5 shows. In this assembled condition the spacing between the first holder plate 26 and the second holder plate 27 is substantially constant throughout the entire surface of the holder plates. The two holder plates 26, 27 can be tilted relative to one another, for example, by pressing the holder plates towards one another at the location of the rubber element 22, as is shown in the schematic front view of Figure 6. On account of the cooperation of the rubber elements 22, 23, 24, 25 with the holder plates the distance between the holder plates can be varied from, for example, d₁ , at the location of the rubber element 22, to d₂, at the location of the rubber element 23. If the pressure is removed at the location of the rubber element 22, the rubber elements will again urge the holder plates to a position in which their stop surfaces abut. Due to the fact that the rubber elements are elastically deformable it is clear that the holder plates can be tilted relative to one another in any desired position. In order to avoid a variation in the position of the rubber elements when pressure is applied, the first holder plate 26 and the second holder plate 27 are provided with projections 30 and apertures 31 respectively which locate opposite ends of the rubber elements. The solid-state image sensor 70 is fixed to the second holder plate 27, for example, by means of an adhesive (Figure 7). An image-receiving surface 72 of the solid-state image sensor 70 is accommodated in an envelope 73 of the image sensor 70 and it is assumed that its exact position relative to the envelope 73 is unknown. To place the solid-state image sensor 70, or more precisely the image-receiving surface 72, into a desired position relative to the exit window 71 opposite which the said image sensor is arranged, a test pattern is displayed on the entrance window of the colour-separation system, the test pattern being incident on the image-receiving surface 72 (see arrows in Figure 7) via the exit window 71 and passing through apertures 61, 62 of the holder 21. This test pattern is recorded by connecting the image sensor to a monitor (not shown in Figure 7). As is schematically shown in Figure 8, the image-receiving surface 72 can be oriented parallel to the exit window 71 by tilting the image sensor 70 until a desired test pattern is recorded. Subsequently, the two holder plates are rigidly secured to one another in this desired relative position. This can be carried out, for example, by means of an adhesive. Since an adhesive needs some time to cure the image sensor has to be held in the desired position during the curing time. Preferably, a UV-curable adhesive is used so that the fixation can be carried out rapidly and in a defined manner. If, in order to obtain a properly functioning camera, it is additionally required that the central axis extending perpendicularly to the image-receiving surface coincides substantially with the optical axis of the relevant exit window, the image sensor is displaced over the exit window until a desired test pattern is displayed, after which the first holder plate 26 is secured to the exit window. If this displacement is not necessary the first holder plate 26 can be secured to the exit window at an earlier stage.

Claims: An optical assembly for a camera comprising a colour separation system (1) having an entrance window (2) and at least one exit window (3, 4, 5, 71) a solid state image sensor (6, 7, 8, 70) being fixed to the or each exit window (3, 4, 5, 71), which solid state sensor comprises an image-receiving surface (72) accomodated in an envelope (73), the image-receiving surface (72) being arranged relative to the corresponding exit window (3, 4, 5, 71) in a predetermined position, said position being determined by at least one element (52, 57, 58, 59, 22, 23, 24, 25) of elastically deformable material characterized in that the or each solid-state image sensor (6, 7, 8, 70) is fixed to the corresponding exit window (3, 4, 5, 71) by means of a holder (9, 10, 11, 51, 21) which comprises a first holder plate (12, 13, 14, 55, 26) having along its edges slotted elements projecting from the first holder plate, the slots of which are bounded by at least one first stop surface (28) at the end of the slot which is farthest from the plate, and a second holder plate (15, 16, 17, 56, 27) having along its edges second stop surfaces (29) movable in the slots of the slotted elements, said holder plates having facing apertures, ( 45, 46, 47, 53, 61; 48, 49, 50, 54, 62) said first and second holder plates being fixed to the corresponding exit window (3, 4, 5, 71) and the solid-state image sensor (6, 7, 8, 70) respectively, and being secured to one another to maintain the predetermined position, the holder further comprising the element (52, 57, 58, 59, 22, 23, 24, 25) of elastically deformable material in a position in which it coöperates with and acts between the two holder plates. An optical assembly as claimed in Claim 1, characterized in that the elastically deformable element, when viewed in directions perpendicular to the holder plates, surrounds the apertures of the holder plates. An optical assembly as claimed in Claim 1 or 2, characterized in that the elastically deformable element comprises separate segments which, when viewed in directions perpendicular to the holder plates, at least partly surround the apertures in the holder plates. An optical assembly as claimed in Claim 1, 2 or 3, characterized in that the elastically deformable element comprises four separate segments which, when viewed in directions perpendicular to the holder plates, define the vertices of an imaginary rectangle which surrounds the apertures in the holder plates. An optical assembly as claimed in Claim 1, 2, 3 or 4, characterized in that the first and second holder plates are secured to one another by UV-light curable adhesive.

Inventors: DE ROOIJ JACOBUS ADRIANUS GERA, DE ROOIJ, JACOBUS ADRIANUS GERARDUS
Applicants: PHILIPS NV, N.V. PHILIPS' GLOEILAMPENFABRIEKEN
Application year: 1989
Main classification: H04N9
IPC codes: H04N9, H04N5