Observation instrument and a video imager arrangement therefor

Abstract

An observation instrument has a shaft and an imaging unit, the imaging unit comprising an objective lens system and an electronic image sensor arranged for picking up an image generated by the objective lens system, the imaging unit being pivotably arranged in a distal end section of the shaft, a pivot axis of the imaging unit being transverse to a longitudinal axis of the distal end section of the shaft, wherein the image sensor is arranged substantially parallel to an optical axis of the objective lens system and the imaging unit comprises a deflection element for deflecting light exiting from an image end of the objective lens system to an image pick-up surface of the image sensor. The invention also relates to a video imager arrangement for an observation instrument.

Claims

1. An observation instrument comprising a shaft and an imaging unit, the imaging unit comprising an objective lens system and an electronic image sensor arranged for picking up an image generated by the objective lens system, the imaging unit being pivotably arranged in a distal end section of the shaft, a pivot axis of the imaging unit being transverse to a longitudinal axis of the distal end section of the shaft, wherein the image sensor is arranged substantially parallel to an optical axis of the objective lens system, wherein the imaging unit comprises a deflection prism, fixed to an image pick-up surface or a cover glass of the image sensor, for deflecting light exiting from an image end of the objective lens system to the image pick-up surface of the image sensor, wherein the objective lens system and the electronic image sensor are pivotable as a unit with respect to the shaft between a first end position in which the optical axis of the objective lens system is approximately parallel to a longitudinal axis of the distal end section of the shaft and a second end position in which the optical axis of the objective lens system forms a maximal angle, α, to the longitudinal axis of the distal end section of the shaft, where α is between approximately 25° and approximately 75° , and wherein a length, L, of the objective lens system is
L≤h/sin α−d/tan α where h is an inner diameter of the distal end section of the shaft and d is a diameter of the objective lens system.

2. The observation instrument of claim 1, wherein the imaging unit comprises a sleeve holding the objective lens system, and wherein the deflection prism is fixed to an image end of the sleeve.

3. The observation instrument of claim 1, wherein the optical axis of the objective lens system is offset to the image pick-up surface of the image sensor.

4. The observation instrument of claim 1, wherein the pivot axis is arranged at a distal edge of the image sensor.

5. The observation instrument of claim 1, wherein the pivot axis is arranged at a location defined by the intersection of the optical axis of the objective lens system with an entrance face of the deflection prism, the pivot axis being parallel to the image pick-up surface of the image sensor.

6. The observation instrument of claim 1 wherein the pivot axis is arranged at the image end of the objective lens system.

7. The observation instrument of claim 2, wherein the pivot axis is arranged at the image end of the objective lens system.

8. The observation instrument of claim 1, wherein the image sensor has a diagonal having a length exceeding the inner diameter h of the distal end section of the shaft.

9. The observation instrument of claim 2, wherein the image sensor has a diagonal having a length exceeding the inner diameter h of the distal end section of the shaft.

10. The observation instrument of claim 1, wherein the shaft is distally closed by a curved cover glass.

11. The observation instrument of claim 1, wherein the observation instrument is an endoscope, an exoscope or an endoscopic capsule.

12. A video imager arrangement for an observation instrument having a shaft, wherein the video imager arrangement comprises an imaging unit, the imaging unit comprising an objective lens system and an electronic image sensor arranged for picking up an image generated by the objective lens system, the imaging unit being pivotably arrangeable in a distal end section of the shaft, a pivot axis of the imaging unit being transverse to a longitudinal axis of the distal end section of the shaft, characterized in that the image sensor is arranged substantially parallel to an optical axis of the objective lens system and that the imaging unit comprises a deflection prism, fixed to an image pick-up surface or a cover glass of the image sensor, for deflecting light exiting from an image end of the objective lens system to the image pick-up surface of the image sensor, wherein the objective lens system and the electronic image sensor are pivotable as a unit with respect to the shaft between a first end position in which the optical axis of the objective lens system is approximately parallel to a longitudinal axis of the distal end section of the shaft and a second end position in which the optical axis of the objective lens system forms a maximal angle, α, to the longitudinal axis of the distal end section of the shaft, where α is between approximately 25° and approximately 75° , and wherein a length, L, of the objective lens system is
L≤h/sin α−d/tan α where h is an inner diameter of the distal end section of the shaft and d is a diameter of the objective lens system.

13. The video imager arrangement of claim 12, wherein the light deflection element is a deflection prism fixed to the image pick-up surface or cover-glass of the image sensor.

14. The video imager arrangement of claim 13, wherein the imaging unit comprises a sleeve holding the objective lens system, and wherein the deflection prism is fixed to an image end of the sleeve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further aspects of the present invention will be apparent from the figures and from the description of particular embodiments that follows. The figures are given by way of illustration only, and thus are not limitative of the present invention. The index numbers used throughout attempt to convey uniformity as much as possible, while also permitting distinct reference thereto. Therefore, the numbering system employed is for the sake of simplicity and clarity and should not be considered limiting.

(2) FIG. 1 shows an observation instrument in a schematic view.

(3) FIGS. 2a-2c show a distal end section of the observation instrument of FIG. 1 in accordance with a first embodiment of the invention in a perspective view, in a frontal view and in a sectional view, respectively.

(4) FIG. 3 shows the imager arrangement according to the first embodiment of the invention in a schematic view.

(5) FIGS. 4a and 4b show the imager arrangement of FIG. 3 in its end positions.

(6) FIGS. 5a and 5b show an imager arrangement according to a second embodiment of the invention in its end positions.

(7) FIGS. 6a and 6b show an imager arrangement according to a third embodiment of the invention in its end positions.

(8) FIGS. 7a and 7b show a variation of the third embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

(9) As shown in FIG. 1, an observation instrument according to the invention may be embodied as a video endoscope 1. The video endoscope 1 comprises an elongate shaft 2 having a rigid tube 3 in the example shown; alternatively, the shaft could be semi-flexible or flexible. The distal end section of the shaft 2 is denoted with reference 4 in FIG. 1. The endoscope 1 further comprises a handpiece 5 arranged at a proximal end of the shaft 2. The handpiece 5 may comprise control elements 6 for controlling various functions of the endoscope 1, for example for controlling the viewing angle, and may comprise connections to electrical supply, image processing, display and/or storage means, as well as to an external light source (not shown).

(10) The distal end section 4 of the shaft 2 is shown in FIG. 2a in an enlarged perspective view, in FIG. 2b in an axial view seen from the distal side, and in FIG. 2c in a longitudinal sectional view. The shaft 2 has an oblique distal end 8. The distal end section 4 of the shaft 2 may have three internal compartments 9, 9′, 9″ separated by longitudinal walls 10, 10′ inside the tube 3. In the side compartments 9, 9′ light guides 11, 11′ may be arranged for transmitting illumination light to the distal end 8 of the endoscope 1 and to illuminate an object field to be observed. The light guides 11, 11′ may consist of a multiplicity of optical fibers that may be embedded at the distal end 8 in a suitable resin to form a hermetic seal.

(11) The central compartment 9″ comprises an imaging unit 12, which comprises an objective lens system 13 and an electronic image sensor 14 (see FIG. 2c). The sectional view shown in FIG. 2c is a section along line B-B in FIG. 2b in a longitudinal plane 15 of the distal end section 4 of the shaft 2. As described below, the imaging unit 12 is pivotably held in the distal end section 4. The central compartment 9″ is hermetically sealed by a cover glass 16, which is transparent or is transparent at least in such sections which may be crossed by light rays that are imaged on the image sensor 14.

(12) In the example shown the objective lens system 13 comprises at its distal end a negative front lens 17, and two further optical elements 18, 19, which may be imaging lenses. Typically the objective lens system 13 comprises one or more aperture stops (not shown). The lens 17 may be a single lens or a lens group, for example a cemented doublet or triplet. The further optical elements 18, 19 may be lenses and/or glass blocks, which in turn may be single optical elements or cemented doublets or triplets, for example. In the proximal direction following the objective lens system 13, the imaging unit 12 comprises a deflection prism 20 which is mounted on the image sensor 14. The deflection prism serves to deflect light rays exiting from the objective lens system 13 at its image end towards the image pick-up surface of the image sensor 14. The lens 17 of the objective lens system is indicated symbolically also in FIGS. 2a and 2b.

(13) The imager arrangement according to a first embodiment of the present invention is shown in a schematic sectional view in FIG. 3. The imaging unit 12 is configured as shown in FIG. 2c and described above, while FIG. 3 shows further details. As indicated by dashed lines, the lens 17 and the further optical elements 18, 19 of the objective lens system are held in their respective positions by a sleeve 21 which is fixedly connected to the deflection prism 20 and the image sensor 14. The lens 17, the optical elements 18, 19, and the deflection prism 20 are configured such that rays entering the imaging unit 12 from an object field along or close to an optical axis 22, pass through the lens 17 and the optical elements 18, 19, enter into the deflection prism 20 at a right angle to an entrance face 23, are deflected by 90° at the deflection face 24 and exit from the deflection prism 20 at a right angle to an exit face 25. The deflection prism 20 is held on the image sensor 14 such that the exit face 25 is adjacent to an image pick-up surface 26 of the image sensor 14. For example, the deflection prism 20 may be fixed or glued with its exit face 25 to a cover glass of the image sensor 14 (not shown). The objective lens system 13 is configured to focus an image of an object field on the image pick-up surface 26, i.e. on the light-sensitive area of the image sensor 14, or at least on a part of the light-sensitive area. Due to the deflection at the deflection face 24 forming an angle of 45° to the image pick-up surface 26 of the image sensor 14, the optical axis 22 of the objective lens system 13 is substantially parallel to a sensor plane of the image sensor 14. The exit face 26 has a side length which at least equals the diameter of a circular image generated by the objective lens system 13 on the image pick-up surface 26, and preferably is less than about 150% of the image diameter.

(14) Further, a pivot axis A of the imaging unit 12 is shown in FIG. 3, which may be, for example, configured as a bolt which is rotatably held in corresponding bearings in the walls 10, 10′ (see FIG. 2b). The pivot axis A is substantially perpendicular to a longitudinal axis 27 of the distal end section 4. Thus, the imaging unit 12, comprising the objective lens system 13, the deflection prism 20 and the image sensor 14, is pivotably held in the distal end section 4 of the shaft 2, forming a substantially rigid unit pivotable about pivot axis A. The cover glass 16 is depicted only symbolically in FIG. 3. The imaging unit 12 may comprise further elements, such as one or more diaphragms and/or spacers (not shown). Moreover, one or more actuation elements may be provided for actuating the pivoting motion, such as a control wire connected to the control elements 6 of the handpiece 5 (see FIG. 1), which actuation elements are not shown in FIG. 3.

(15) In the example depicted in FIG. 3, the pivot axis A is located at a distal edge of the approximately rectangular image sensor 14. As indicated in FIG. 3, the sleeve 21 holding the objective lens system 13 has a length L and a width d. This means that the imaging unit 12 can be pivoted up to a tilting angle α, in which position the relation is satisfied
L sin α+d cos α≤h
wherein h is the inner width of the tube 3 in the distal end section 4 of the shaft 2 (see FIG. 1). As is indicated in FIG. 3, the total height h may not be completely exploited due to the curvature of a cross-section of the tube 3 in the central compartment 9″ (see FIG. 2b). Thus, generally
L sin α+d cos α≤h
If, on the other hand, the maximal tilting angle α is pre-defined, the maximal allowable length L of the objective lens system 13 is
L≤h/sin α−d/tan α
the maximal tilting angle α is the maximal angular deviation of the optical axis 22 of the objective lens system 13 from the longitudinal axis 27 of the distal end section 4 of the shaft 2, and thus the maximal viewing angle of the endoscope 1. The cover glass 16 is inclined correspondingly at an angle α with respect to a direction perpendicular to the longitudinal axis 27. The cover glass 16 may be substantially flat, as shown in FIGS. 2a, 2c, and 3, or the cover glass may be curved (see below).

(16) Further, as can be seen in FIG. 3, the length of the longer side, or at least a length of a diagonal of the image sensor 14, can be larger than h, i.e. larger than the inner width of the tube 3, and may be larger than shown in FIG. 3. In standard image sensors, the dimensions of the image sensor 14 exceed the respective dimensions of the light-sensitive surface, and thus of the image pick-up surface 26, the image sensor 14 comprising margins for electrical connections and/or due to packaging. In FIG. 3 such margins 28, 29 are those parts of the surface of the image sensor that exceed the image pick-up surface 26. The exit face 25 of the deflection prism 20 substantially covers the image pick-up surface 26 and extends only over a small faction part of the margins 28, 29. A width of the image sensor 14, as well as the diameter of the sleeve 21 and the width of the deflection prism 20 are slightly less than a width of the central compartment 9″ (see FIGS. 2a-2c).

(17) As can also be seen in FIG. 3, in a shaft 2 of given inner height h the maximal achievable tilting angle α may be larger if L and/or the length of the image sensor 14 is smaller. Further, the smaller the image pick-up surface 26 is, the smaller the size of the deflection prism 20 can be chosen, which in turn permits choosing a smaller diameter d of the objective lens system 13 and thus permitting a larger maximal viewing angle α. Thus, if h is pre-defined, there may be a trade-off between L and/or d on the one hand and a on the other hand.

(18) The imager arrangement of FIG. 3 is shown in its end positions in FIGS. 4a and 4b. The end position that corresponds to the maximal viewing angle or tilting angle α is shown in FIG. 4a, which is a simplified depiction of the situation of FIG. 3. FIG. 4b shows the minimal viewing angle, which is approximately 0°, i.e. a viewing direction parallel to the longitudinal axis 27 of the distal end section 4.

(19) FIGS. 5a and 5b, as well as FIGS. 6a and 6b, show two alternative embodiments, which are distinguished from the arrangement of FIGS. 3 and 4a and 4b in differing locations of the pivot axis A. According to the embodiment of FIGS. 5a and 5b, the pivot axis A is located at the distal edge of the image pick-up surface 26, which approximately coincides with the intersection line of the entrance face 23 and the exit face 25 of the deflection prism 20. In the embodiment of FIGS. 6a and 6b, the pivot axis A is placed at a location that is defined by the intersection of the optical axis 22 of the objective lens system 13 with the entrance face 23 of the deflection prism 20, the pivot axis A being parallel to the image pick-up surface 26.

(20) In a variation of the embodiment of FIGS. 6a and 6b and as depicted in FIGS. 7a and 7b, the tube 3 or at least the central compartment 9″ may be sealed by a curved cover glass 30. The cover glass 30 may be curved in a circular arc about the pivot axis A, such that it is intersected perpendicularly by the optical axis 22 of the objective lens system at the end positions of the imaging unit 12 as shown in FIGS. 7a and 7b, and preferably at all possible viewing angles. The curved cover glass 30, on the other hand, may be embodied as a section of a sphere having its center of curvature on the pivot axis A, or may be curved in a shape that is not symmetrical with respect to the pivot axis A. Although a curved cover glass 30 is shown only in a variation of the third embodiment, a curved cover glass may be provided in corresponding variations of the other embodiments.

(21) The three embodiments described differ in the maximal allowable length of the image sensor 14, which may exceed the length shown in the Figures on a distal and/or proximal side. In FIGS. 4a-6b the components of the imaging unit 12 and of the distal end section 4 of the shaft 2 are shown only symbolically.

(22) According to the embodiments described, for example, a full HD sensor having 1.4 μm pixel size, and an objective lens system 13 having a corresponding diameter d of about 3 mm may be employed in a variable-direction-of-view endoscope having a shaft inner height h of about 5 mm, while the direction of view may be freely chosen in a total range of viewing angles up to a maximal viewing angle α of at least 25°.

(23) For clarity not all reference numerals are displayed in all figures. If a reference numeral is not explicitly mentioned in the description of a figure, it has the same meaning as in the other figures.

REFERENCE NUMERALS

(24) 1 Endoscope 2 Shaft 3 Tube 4 Distal end section 5 Handpiece 6 Control element 8 Distal end 9, 9′, 9″ Compartment 10, 10′ Wall 11, 11′ Light guide 12 Imaging unit 13 Objective lens system 14 Image sensor 15 Plane 16 Cover glass 17 Lens 18 Optical element 19 Optical element 20 Deflection prism 21 Sleeve 22 Optical axis 23 Entrance face 24 Deflection face 25 Exit face 26 Image pick-up surface 27 Longitudinal axis 28 Margin 29 Margin 30 Cover glass A Pivot axis