JP2008193390A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a lens barrel retracting length by closing a gap around a low-pass filter and to easily manage dust on the low-pass filter.
An optical system having at least one lens group movable to a photographing position and a storage position, an image sensor for converting optical image information from the optical system into an electrical signal, and an optical system disposed in the optical system. In the imaging apparatus including the optical filter, the optical filter is integrally held on the back surface of the lens holding frame that holds the lens group disposed on the front surface of the imaging element among the lens groups of the optical system. Thus, the lens barrel retracting length is shortened to the gap between the lens unit and the low-pass filter, and the dust-proof effect on the low-pass filter can be enhanced by holding the low-pass filter integrally with the lens holding frame.
[Selection] Figure 1

Description

  The present invention relates to a technique of an imaging apparatus having an optical system that can be moved to a photographing position and a storage position.

  An example of an imaging apparatus having an optical system that can be moved to a conventional shooting position and a storage position is disclosed in Patent Document 1, for example. FIG. 5 is a cross-sectional view of a zoom lens barrel included in an imaging apparatus in a conventional example, and FIG. 6 is an enlarged cross-sectional view of a low-pass filter holding unit in the conventional example.

  A low-pass filter 37 disposed in front of the CCD 40 is held by a low-pass filter holder 35, and a space between the CCD 40 and the low-pass filter 37 is sealed by a CCD rubber 38. The low-pass filter holder 35 has a base 35b substantially parallel to the optical axis of the photographic lens, and extends from one end of the base 35b in a direction perpendicular to the optical axis of the photographic lens and away from the optical axis of the photographic lens. The first extending portion 35d is provided. Further, the second base portion 35c includes a second extending portion 35c extending from the other end of the base portion 35b in a direction perpendicular to the optical axis of the photographing lens and extending in the optical axis direction of the photographing lens. The first extending portion 35 d comes into contact with the opening edge portion 30 b of the CCD holder 30, and the second extending portion 35 c comes into contact with the diaphragm 36 disposed on the low-pass filter 37.

With the above configuration, the retractable length of the zoom lens barrel can be shortened as compared with the case where the low-pass filter holder 35 is integrally formed with the CCD holder 30 which is a resin member. This is because the low-pass filter holder 35, which is a plate-like metal member whose section is thinner than that of the resin member, is used as a fixing member for fixing the low-pass filter 37.
JP 2006-67356 A

  However, in the conventional example, it is necessary to provide a design clearance so as not to interfere with the lens unit that is closest to the low-pass filter when retracted (in the conventional example, it is a two-group lens unit). In this gap, the low-pass filter is held by the resin member. Alternatively, it is always necessary regardless of being held by a plate-like metal member. Therefore, there remains a problem that the lens barrel retractable length cannot be shortened for the gap between the lens unit and the low-pass filter.

  In addition, dust on the low-pass filter is an important management item in manufacturing because it appears on the shooting screen. The influence of dust reflection increases as the low-pass filter is closer to the imaging surface. However, the conventional example has a problem in that it is difficult to manage dust on the low-pass filter because the low-pass filter is disposed as close to the CCD as possible in order to shorten the lens barrel retractable length.

  Therefore, in the present invention, it is possible to shorten the lens barrel retracting length even to the gap between the lens unit and the low-pass filter. It is another object of the present invention to provide an imaging apparatus that can enhance the dustproof effect on the low-pass filter by integrally holding the low-pass filter on the lens holding frame.

  According to a first aspect of the present invention, there is provided an optical system (1, 2, 3) having at least one lens group movable to a photographing position and a storage position. In an imaging device comprising an imaging device (4) for converting optical image information from an optical system into an electrical signal, and an optical filter (5) disposed in the optical system, among the lens groups of the optical system, In the imaging apparatus, the optical filter is integrally held on a back surface of a lens holding frame (13) that holds a lens group (3) disposed in front of the imaging element.

  As described above, according to the present invention, the lens barrel retracting length is shortened even to the gap between the lens unit and the low-pass filter, and further, the dust-proof effect on the low-pass filter is enhanced by holding the low-pass filter integrally with the lens holding frame. There is an effect that can.

  Embodiments of the present invention will be described below with reference to the drawings.

  First, the overall configuration of the zoom lens barrel included in the imaging apparatus of the present invention will be described. In FIG. 1, reference numerals 1 and 2 denote a first group lens having a zooming action, a second group lens, 3 a third group lens for controlling focus and image plane correction, and 4 a CCD as an image sensor. The CCD 4 is an element that converts optical image information from the optical system into an electrical signal. The lens group 3 is disposed in front of the CCD 4. Reference numerals 11, 12, and 13 denote holding frames that hold the respective group lenses so as to be movable in the optical axis direction. Each is a first group barrel, a second group barrel, a third group barrel, and the first and second group barrels are held by a movable cam ring 21 having a cam groove on the inner periphery. A low-pass filter 5 for reducing false signals generated in the CCD 4 is integrally held on the rear surface of the third group barrel 13. The low-pass filter 5 optically separates incident light from the optical system. Reference numeral 14 denotes a known aperture shutter unit, which is fixed to the second group barrel 12 and moves integrally with the second group barrel 12 in the optical axis direction. Reference numeral 22 denotes a fixed cylinder, and a movable cam ring is movably held by a cam groove provided on the inner periphery. Reference numeral 23 denotes a CCD holder, to which a fixed cylinder 22 is fixed. A CCD plate 25 holds the CCD 4 and is fixed to the CCD holder 23. Reference numeral 6 denotes a dust-proof rubber for sealing dust between the third group lens barrel 13 and the CCD 4. Reference numeral 24 denotes a rectilinear guide ring that moves straight while suppressing rotation of the first group barrel 11 and the second group barrel 12.

  The operation of the zoom lens barrel configured as described above will be described in detail. The rotation of the zoom motor (not shown) meshes with an outer gear (not shown) formed on the moving cam ring 21 by a gear system (not shown) to rotate the moving cam ring 21. Three follower pins 21 a that fit into the three inner surface cam grooves 22 a of the fixed cylinder 22 are planted on the outer periphery of the movable cam ring 21, and the movable cam ring 21 rotates along the cam groove 22 a of the fixed cylinder 22. However, it moves in the optical axis direction. The front protrusion 24 a on the outer periphery of the rectilinear guide ring 24 is in contact with a groove 21 b provided on the inner periphery of the movable cam ring 21. Further, the flange portion 24 b at the rear end portion of the linear guide ring 24 is in contact with the rear end portion of the movable cam ring 21. As a result, the linear guide ring 24 is restricted from moving relative to the movable cam ring 21 in the optical axis direction. The rectilinear guide ring 24 is fitted in a rectilinear guide (not shown) provided on the inner peripheral side surface of the fixed cylinder 22 so that the rectilinear guide ring 24 can advance linearly, thereby restricting movement of the rectilinear guide ring 24 in the rotational direction. Therefore, when the movable cam ring 21 rotates and moves along the cam groove 22a of the fixed cylinder 22, the rectilinear guide ring 24 follows only the movement of the movable cam ring 21 in the optical axis direction and moves only in the optical axis direction. Three cam followers (not shown) of the first group barrel 11 and three cam followers (not shown) of the second group barrel 12 are fitted in the inner surface cam grooves 21c and 21d of the movable cam ring 21, respectively. A rectilinear guide groove (not shown) having a constant width is provided on the side surface of the rectilinear guide ring in parallel with the optical axis. The straight movement of each group barrel is suppressed by this straight guide groove. Therefore, when the movable cam ring 21 moves, each group barrel does not rotate but moves in the optical axis direction along each inner surface cam groove, and it is possible to arrange lenses according to a desired focal length. It is.

  Next, the configuration and driving of the third group barrel will be described in detail with reference to FIG. The third group lens 3 is fixed to the third group lens barrel 13 by heat caulking or bonding. On the back surface of the third group barrel 13, there are provided attachment surfaces 3a as attachment portions at locations corresponding to the four corners in the diagonal direction where the circular third group lens 3 and the square low-pass filter 5 do not overlap in projection. The attachment surface 3a is held in a substantially diagonal phase. The low-pass filter 5 is adhered and fixed to the mounting surface 3a so as to sandwich a mask 7 that blocks unnecessary light from the optical system (see FIG. 2b). Thus, the third group barrel 13 is integrally held. The third group barrel 13 is slidably held by a main guide bar 31 fixed to the CCD holder 23 in parallel with the optical axis. A sub guide bar (not shown) parallel to the optical axis (not shown) is provided on the CCD holder 23 on the substantially opposite side of the main guide bar 31 across the optical axis so that the detent 13b of the third group barrel 13 can slide. It is mated. Further, the third group lens barrel 13 has a nut receiving portion 13c, and a nut (not shown) screwed to a feed screw of a focus motor (not shown) is disposed in the nut receiving portion 13c. Since it is configured in this way, the third group lens barrel 13 advances and retreats along the main guide bar 31 in the optical axis direction when the focus motor rotates together with the low-pass filter 5 that is integrally held. That is, the lens groups 1, 2, and 3 are movable between the photographing position and the storage position.

  The effects of the configuration of the present invention will be described with reference to the retracted lens barrel cross-sectional view of FIG. 3 (the components having the same functions in FIGS. 3a, b, and c are given the same numbers). 3a is a configuration of the present invention, FIG. 3b is a configuration of a conventional example, and FIG. 3c is an enlarged view around a low-pass filter 5 in the conventional example. In the conventional example in FIG. 3b, the attachment portion thickness A for holding the low-pass filter 5 and the air interval B generated between the third group lens barrel 13 and the CCD holder 23 holding the low-pass filter because they are separate. Is absolutely necessary (see FIG. 3c). However, in the present invention shown in FIG. 3a, the lens barrel retracting length can be shortened by C obtained by adding A and B by integrally holding the low pass filter 5 in the third group barrel 13 which is the last group of the optical system. .

  The reason why the low pass filter is integrally held on the back surface of the lens group (the back surface of the third group barrel 13 in the embodiment) which is the last group of the optical system according to the present invention is as follows.

  FIG. 4 is an explanatory diagram showing the operation of the low-pass filter. Light rays incident on the low-pass filter from the left side of the figure are separated and emitted with a certain separation width due to anomalous dispersion due to birefringence. It is the action of the low-pass filter that blurs high-frequency components on the imaging surface by adjusting the separation width. Therefore, the separation width needs to be unchanged regardless of the zoom position of the optical system. For example, when the zoom position changes between the first group and the second group or between the second group and the third group, the angle of the light beam incident on the low-pass filter changes depending on the zoom position. Be realistic. On the other hand, once the light passes through the optical system, the angle of light incident on the low-pass filter does not change. Therefore, if the low-pass filter is arranged between the optical system and the imaging surface, there is no problem even if the distance changes. Therefore, it can be realized by a) holding the low pass filter on the back of the last lens group of the optical system or on the front of the imaging surface in terms of shortening the lens barrel retractable length corresponding to the thickness A of the attachment part and the air gap B. It is.

  Moreover, the dust on the low-pass filter is an item that needs to be particularly managed in the manufacturing process. Since the influence of dust on the captured image increases as the low-pass filter is closer to the imaging surface, it is better to keep the low-pass filter as far as possible from the imaging surface. Therefore, b) The configuration in which the low-pass filter is integrally held on the back surface of the last lens group of the optical system is a configuration of the present invention, rather than the configuration in which the low-pass filter is integrally held on the front surface on the imaging surface. This is effective. Further, as apparent from a comparison between FIGS. 1 and 3, the low-pass filter 5 is fixed in front of the CCD 4 in FIG. On the other hand, in the present invention, the low-pass filter 5 is moved away from the CCD 4 in the lens barrel extension state (FIG. 1) at the time of photographing from the simultaneous lens barrel sink (FIG. 3A). This is advantageous for dust on the low-pass filter.

  As described above, in the configuration of the present invention, the lens barrel retracted length is shortened even to the air gap between the low-pass filter 5 and the CCD 4 by integrally holding the low-pass filter 5 on the back surface of the third group lens barrel 13 disposed on the front surface of the CCD 4. Furthermore, since the low-pass filter 5 moves away from the CCD 4 when the lens barrel is extended, the dust on the low-pass filter can be easily managed.

Zoom lens barrel cross section (WIDE position) Configuration perspective view of third group barrel Retractable lens barrel sectional view showing the effects of the present invention (a present invention, b conventional example, c enlarged view) Explanatory diagram showing the action of the low-pass filter Cross section of zoom lens barrel in the conventional example (collapsed position) Sectional drawing which expanded the low-pass filter holding part in a conventional example

Explanation of symbols

1 1st group lens 2 2nd group lens 3 3rd group lens 4 CCD
5 Low-pass filter 6 Dust-proof rubber 11 1st group barrel 12 2nd group barrel 13 3rd group barrel 14 Aperture shutter unit 21 Moving cam ring 22 Fixed cylinder 23 CCD holder 24 Straight guide ring 25 CCD plate

Claims (3)

  In an imaging apparatus comprising: an optical system having a lens group movable to an imaging position and a storage position; an imaging element that converts optical image information from the optical system into an electrical signal; and an optical filter disposed in the optical system. An image pickup apparatus, wherein the optical filter is integrally held on a back surface of a lens holding frame that holds a lens group disposed on a front surface of the image pickup element among the lens groups of the optical system.   The image pickup apparatus according to claim 1, wherein the optical filter is a low-pass filter for optically separating incident light from the optical system and reducing a false signal generated in the image pickup device.   The imaging apparatus according to claim 1, wherein the lens holding frame is provided with a mounting portion of the optical filter at a substantially diagonal phase in the imaging device.

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