JP2008015158A - Optical lens barrel, image forming optical system and photographing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical lens barrel capable of effectively preventing flare and ghost regardless of a photographing viewing angle, and an image forming optical system and a photographing device. <P>SOLUTION: The optical lens barrel in which a focal length variable optical system for forming an image with subject light is housed is equipped with a light shielding member which prevents the advance of external light other than the subject light with which the image is formed by the optical system, and which is arranged on an optical path and which changes a light transmissive effective diameter in accordance with the focal length of the optical system by the release of the application of voltage. When the focal distance is short (that means, the photographing viewing angle is wide), a bright photographic image is obtained by increasing the light transmissive effective diameter of the light shielding member, and when the focal distance is long (that means, the photographing viewing angle is narrow), the occurrence of an image defect is accurately avoided by decreasing the light transmissive effective diameter of the light shielding member. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical barrel that houses an optical system, an imaging optical system that forms an image of subject light, and a photographing apparatus that photographs the subject.

  In recent years, not only a normal size camera but also a small imaging device mounted on a mobile phone or the like has been equipped with a zoom function and an autofocus function, and the imaging device generally includes a plurality of lenses. It is becoming. In addition, an increase in the number of pixels of the image pickup device, an increase in zoom magnification, and the like have also led to an increase in the number of lenses provided in the image pickup apparatus.

  By the way, when shooting a subject under strong light such as outdoors in fine weather, when sunlight enters the lens from outside the field of view, the lens mirror that holds the lens surface and lens The image may be reflected by the trunk and reach the imaging surface, and an image defect such as ghost or flare may occur in the captured image. In particular, in an imaging apparatus equipped with a plurality of lenses as described above, light is reflected multiple times by a plurality of lenses, so harmful light that causes image defects also enters the imaging surface from multiple directions in a complicated manner. End up. As a result, ghosts and flares occur at various positions in the captured image, and there is a problem that it is difficult to correct image defects by image processing or the like.

  As a method for solving such a problem, there is known a method in which a flare prevention plate for blocking harmful light incident from outside the photographing field angle is provided in the photographing apparatus. However, if a flare prevention plate is installed at a position that matches the wide field of view during wide-angle shooting, unnecessary telephoto light is generated from outside the field of view when shooting with a narrow field of view. Such light becomes harmful light, and flare and ghost are generated in the photographed image. Conversely, if a flare prevention plate is installed at a position that matches the narrow shooting angle of view during telephoto shooting, the shooting angle of view will be blocked by the flare prevention plate during wide-angle shooting, and part of the shot image will become darker There is a problem.

In this regard, Patent Document 1 discloses a flare-preventing plate and a lens barrel that are composed of a plurality of wings surrounding an optical axis in a photographing apparatus equipped with a zoom function in which a lens barrel protrudes in accordance with a photographing field angle. Are connected by a cam mechanism, and the overlapping degree of a plurality of wings is changed according to the protruding position of the lens barrel, and the size of the opening formed by these wings is adjusted. No. 2 describes a technique in which a hood is provided in front of the lens, and the hood is moved in the front-rear direction by a motor or the like in accordance with the protruding position of the lens to adjust a region where light enters. According to the techniques described in Patent Document 1 and Patent Document 2, since the area that blocks light is adjusted according to the shooting angle of view, image defects can be reduced with high accuracy regardless of the shooting angle of view.
Japanese Patent Laid-Open No. 4-133011 Japanese Patent Laid-Open No. 9-15476

  However, in recent years, the downsizing of photographing apparatuses has been rapidly progressing, and in such a small photographing apparatus, the size, storage space, power consumption, and the like of components are greatly limited. It is difficult to provide a flare prevention plate using a motor or a cam mechanism.

  In view of the above circumstances, the present invention provides an optical barrel that can effectively prevent flare and ghost regardless of the angle of view, an imaging optical system that forms an image of subject light, and an imaging device that photographs the subject. The purpose is to provide.

The optical lens barrel of the present invention that achieves the above object is an optical lens barrel that contains an optical system with a variable focal length that forms an image of subject light.
A light-shielding member that is arranged on the optical path to prevent outside light from entering other than the subject imaged by the optical system and that changes the effective light transmission diameter by applying and releasing a voltage according to the focal length of the optical system. It is characterized by having.

  According to the optical barrel of the present invention, the light transmission effective diameter of the light-shielding member changes according to the focal length of the optical system in response to the applied voltage release without using a motor, a cam mechanism, etc. Both avoidance and downsizing of the apparatus can be achieved. In addition, when the optical lens barrel of the present invention is mounted on a small photographing apparatus or the like and the focal length is short (that is, the photographing field angle is wide), the light transmission effective diameter of the light shielding member is increased to increase the photographing field angle. This prevents the incident light from being blocked and a part of the photographed image becomes dark. When the focal length is long (that is, the photographing angle of view is narrow), the light-shielding member can transmit light effectively. By reducing the diameter, it is possible to block light incident from outside the shooting angle of view and avoid flare and ghosting with high accuracy.

  In the optical barrel of the present invention, it is preferable that the light shielding member is composed of an electrochromic element.

  The electrochromic element has a characteristic that the light transmittance changes according to the applied voltage, and further, the deformation amount thereof is large, so that the electrochromic element can be preferably applied as a light shielding member in the present invention.

  In the optical barrel of the present invention, it is also preferable that the light shielding member is composed of a liquid crystal element.

  The liquid crystal element also has a characteristic that the light transmittance changes according to the applied voltage, and can be used as a light shielding member in the present invention.

  Further, in the optical barrel of the present invention, the light shielding member includes a plurality of concentrically arranged segments that change transmittance by applying and releasing voltage so that the effective light transmission diameter is concentrically changed in a plurality of stages. It is preferable that it has.

  By changing the light transmittance of each of the plurality of segments and adjusting the light transmission effective diameter of the light shielding member in a plurality of stages concentrically, harmful light can be reliably prevented with a simple mechanism.

  In the optical barrel of the present invention, the light shielding member changes the effective light transmission diameter by applying and releasing a voltage, and flattens the light amount distribution between the center and the periphery on the imaging surface of the subject image by the optical system. It is suitable to be made.

  Usually, the light amount distribution on the imaging surface of the subject image by the optical system is often larger at the center and smaller at the periphery, and if the subject image is photographed in such a state, the peripheral portion of the photographed image becomes dark. There is a problem. According to the preferred optical lens barrel of the present invention, the light amount distribution between the center and the periphery on the imaging surface of the subject image is flattened, so that a high-quality captured image having uniform brightness can be obtained. .

In addition, the imaging optical system of the present invention that achieves the above object includes the above optical barrel,
Control means for controlling the light transmission effective diameter of the light shielding member to the light transmission effective diameter according to the focal length of the optical system by applying and releasing a voltage according to the focal length of the optical system in the light shielding member. Features.

  According to the imaging optical system of the present invention, it is possible to reliably prevent entry of harmful light by controlling the effective light transmission diameter of the light shielding member in accordance with the focal length to save power.

  It should be noted that the imaging optical system according to the present invention is only shown in its basic form here, but the imaging optical system according to the present invention is not limited to the above basic form, but includes the optical barrel described above. Various forms corresponding to these forms are included.

An imaging device of the present invention that achieves the above object includes the above-described imaging optical system,
And an imaging device arranged on the imaging surface of the subject image of the optical system.

  According to the photographing apparatus of the present invention, even in a small photographing apparatus having no power or internal space, it is possible to reliably avoid a problem that a ghost or flare occurs in a photographed image and to obtain a high-quality photographed image. it can.

  Note that only the basic form of the photographing apparatus according to the present invention is shown here, but the photographing apparatus according to the present invention includes not only the above basic form but also each form of the optical barrel described above. Various corresponding forms are included.

  According to the present invention, it is possible to provide an optical barrel, an imaging optical system, and a photographing apparatus that can effectively prevent flare and ghost regardless of a photographing field angle.

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

  1 and 2 are external perspective views of a digital camera to which an embodiment of the present invention is applied.

  FIG. 1 shows the retracted state of the lens barrel 10, and FIG. 2 shows the extended state of the lens barrel 10. The lens barrel 10 incorporates a photographing lens, and a front surface of the lens barrel 10 is provided with a flare prevention plate 70 (described later) that blocks harmful light incident from outside the photographing field angle. . The flare prevention plate 70 corresponds to an example of a light shielding member according to the present invention.

  An auxiliary light emission window 12 and a viewfinder objective window 13 are arranged on the front upper part of the digital camera 1 shown in FIGS. 1 and 2, and a shutter button 14 is provided on the upper part of the digital camera 1.

  The digital camera 1 is provided on the back surface (not shown) with various switches such as a zoom operation switch and a cross key, and an LCD (liquid crystal display) for displaying images and menu screens. Press and hold the zoom operation switch for a predetermined time to enter the zoom operation mode to adjust the shooting angle of view, and the photographic lens moves to the telephoto side (tele side) while pressing the “up” key of the cross key. Then, while the “down” key of the cross key is kept pressed, the photographing lens moves to the wide angle side (wide side).

  FIG. 3 is a cross-sectional view of the digital camera 1 in a retracted lens barrel 10 taken along the optical axis. FIG. 4 is a cross-sectional view of the digital camera 1 in which the photographing lens is in a wide state. Is a cross-sectional view taken along the optical axis, and FIG. 5 is a cross-sectional view taken along the optical axis of the lens barrel 10 of the digital camera 1 in which the photographing lens is in the telephoto state.

  In the inner space of the lens barrel 10, there are three groups of a front lens group (first lens group) 21, a rear lens group (second lens group) 22, and a focus lens (third lens group) 23 in order from the front. A photographic lens is arranged in which the optical axes are aligned. The photographing lens changes the field angle of view when the rear lens group 22 moves along the optical axis between the wide end shown in FIG. 4 and the telephoto end shown in FIG. 5, and the focus lens 23 follows the optical axis. By moving the camera, the focus is adjusted. The front group lens 21, the rear group lens 22, and the focus lens 23 correspond to an example of an optical system according to the present invention, and the lens barrel 10 corresponds to an example of an optical lens barrel according to the present invention.

  In front of the front lens group 21, a flare prevention plate 70 that blocks harmful light is disposed. Between the front lens group 21 and the rear lens group 22, a diaphragm unit 30 that adjusts the amount of subject light is disposed. A CCD 40 for reading subject light is disposed behind the photographing lens. The CCD 40 corresponds to an example of an image sensor according to the present invention.

  The flare prevention plate 70 is configured by concentrically fitting a plurality of electrochromic elements (which will be described later) whose light transmittance is changed by applying / releasing voltage to a plate having a through hole in the center portion, By adjusting the light transmittance of each of the plurality of electrochromic elements, the effective light transmission diameter of the flare prevention plate 70 is controlled, and an optical opening 70 ′ through which subject light passes is formed. The flare prevention plate 70 will be described in detail later.

  As shown in FIGS. 4 and 5, the diaphragm unit 30 includes an aperture plate 32 having a hole surrounding the optical axis of the photographic lens, and an aperture for closing the aperture of the aperture plate 32 to adjust the aperture amount. Feather 31 is provided. The diaphragm unit 30 is also provided with a guide lot 24 protruding rearward from the back surface thereof and a stopper 24a for closing the rear end of the guide lot 24. The guide lot 24 holds the rear group lens 22. The rear group lens holding frame 25 is slidably penetrated in the optical axis direction. Further, a coil spring 26 is mounted between the diaphragm unit 30 and the rear group lens holding frame 25, and the diaphragm unit 30 includes a rear group composed of the rear group lens 22 and the rear group lens holding frame 25. The lens unit 27 is held so as to be movable along the optical axis in a manner in which the lens unit 27 is spring-biased forward. When the lens barrel 10 is retracted, the diaphragm blades 31 shown in FIGS. 4 and 5 are opened, and the diaphragm unit 30 moves toward the rear group lens unit 27 while compressing the coil spring 26. The rear lens group unit 27 enters. Thereby, thickness reduction of the digital camera 1 is achieved.

  The lens barrel 10 is provided with a fixed cylinder 50 fixed to the camera body and a drive cylinder 52 that is rotatable with respect to the fixed cylinder 50. The drive cylinder 52 has a protrusion 50 a formed in the circumferential direction on the outer peripheral surface of the fixed cylinder 50 and is engaged with a groove provided on the inner peripheral surface of the drive cylinder 52. Therefore, movement in the optical axis direction is restricted. A gear 51 is provided on the outer peripheral surface of the driving cylinder 52, and a driving force from a motor (not shown) is transmitted to the gear 51 to rotate the driving cylinder 52.

  The drive cylinder 52 is further provided with a key groove 52a extending in the optical axis direction. A pin-like cam follower 54 fixed to the rotationally movable cylinder 53 is provided in the fixed cylinder 50 in the key groove 52a. It penetrates through the formed spiral cam groove. Accordingly, when the drive cylinder 52 rotates, the rotational movement cylinder 53 moves in the optical axis direction along the cam groove while rotating.

  A rectilinear movement frame 55 is provided inside the rotational movement cylinder 53. The rectilinearly moving frame 55 is engaged with the rotationally movable cylinder 53 so as to be freely rotatable relative thereto, and the rotation of the rectilinearly moving frame 55 is restricted by engaging with the key groove 50 b of the fixed cylinder 50. Therefore, when the rotationally movable cylinder 53 moves in the optical axis direction while rotating with the rotation of the drive cylinder 52, the rectilinear movement frame 55 moves linearly in the optical axis direction with the movement of the rotationally movable cylinder 53.

  A pin-shaped cam follower 63 is fixed to the rear group lens holding frame 25 that holds the rear group lens 22 described above. The cam follower 63 is engaged with the cam groove of the rotationally movable cylinder 53 and also is engaged with the key groove 55a extending in the optical axis direction of the rectilinearly moving frame 55, so that the drive cylinder 52 is rotated. When the rotationally moving barrel 53 rotates and moves in the optical axis direction, the rear lens group unit 27 moves straight in the optical axis direction along the shape of the cam groove of the rotationally movable barrel 53.

  Further, as described above, since the diaphragm unit 30 is attached to the lens unit 27 in a state of being biased forward by the coil spring 26, the diaphragm unit 30 moves in the optical axis direction together with the rear group lens unit 27. To do.

  Further, the lens barrel 10 is provided with a rectilinearly moving cylinder 56 that holds the front group lens 21. The straight movement cylinder 56 has a cam follower 57 fixed thereto engaged in a cam groove of the rotation movement cylinder 53 and also in a key groove 55a of the linear movement frame 55 extending in the optical axis direction. Yes. Accordingly, when the rotationally movable cylinder 53 moves in the optical axis direction as the drive cylinder 52 rotates, the rectilinearly movable cylinder 56 follows the shape of the cam groove of the rotationally movable cylinder 53 in which the cam follower 57 is engaged. And move straight in the direction of the optical axis.

  In this way, the lens barrel 10 is extended, and the lens barrel 10 is retracted by rotating the drive cylinder 52 in the reverse direction.

  Further, even after the feeding of the lens barrel 10 is completed, the rotationally movable cylinder 53 can be further rotated while maintaining the position of the front group lens 21, and at this time, the rear group lens unit 27 is rotated. It moves along the cam groove 53 in the direction of the optical axis, thereby adjusting the shooting angle of view (ie, focal length). FIG. 4 shows a state in which the feeding of the lens barrel 10 is completed. At this time, the photographing lens 20 is in the wide state. FIG. 5 shows a state in which the rear moving lens unit 27 is moved until the rotation moving cylinder 53 is further rotated after the feeding is completed and the photographing lens 20 is in the telephoto state.

  Further, the focus lens 23 of the photographic lens has a lead screw 61 rotated by a motor (not shown), and a focus lens holding frame 62 holding the focus lens 23 is screwed into the lead screw 61. As the lead screw 61 rotates, the focus lens 23 moves in the optical axis direction, and focus adjustment is performed.

  Next, the internal configuration of the digital camera 1 will be described.

  FIG. 6 is a schematic internal configuration diagram of the digital camera 1 shown in FIG.

  In the digital camera 1 of the present embodiment, all processes are controlled by the main CPU 110. The main CPU 110 includes various switches provided in the digital camera 1 (the various switches include the shutter button 14 shown in FIG. 1, the zoom operation switch, the cross key, and the like. Operation signals are supplied from the switch group 101). The main CPU 110 has an EEPROM 110a, and various programs necessary for executing various processes by the digital camera 1 are written in the EEPROM 110a. When a power switch (not shown) included in the switch group 101 is turned on, power is supplied from the power source 102 to various elements of the digital camera 1, and the digital camera 1 is programmed by the main CPU 110 according to the program procedure written in the EEPROM 110a. Overall operation is controlled centrally.

  First, the flow of an image signal will be described with reference to FIG.

  When the photographer instructs a shooting angle of view using a cross key (not shown) provided on the back of the digital camera 1, the designated shooting angle of view is transmitted from the switch group 101 to the main CPU 110. In the main CPU 110, a focal length corresponding to the instructed shooting angle of view is calculated, and the calculated focal length is transmitted to the optical control CPU 120. Note that data is not transmitted / received between the main CPU 110 and the optical control CPU 120 via the bus 140, but is transmitted / received at high speed by inter-CPU communication. The optical control CPU 120 controls a motor or the like (not shown) to extend the lens barrel 10 as shown in FIGS. 4 and 5 and further move the rear lens group 22 to a position corresponding to the transmitted focal length. . The optical control CPU 120 instructs the voltage application unit 70a to apply a voltage according to the focal length transmitted from the main CPU 110. The plurality of electrochromic elements constituting the anti-flare plate 70 have a property of developing color when a voltage is applied and decoloring when the application of the voltage is stopped. When the application / release of the voltage to the flare prevention plate 70 is controlled by the optical control CPU 120, the effective light transmission diameter of the flare prevention plate 70 is adjusted to form an optical opening 70 '. The subject light enters through the photographing lens. A combination of the optical control CPU 120 and the voltage application unit 70a corresponds to an example of a control unit according to the present invention.

  Further, the optical control CPU 120 controls a motor or the like (not shown) to move the focus lens 23 shown in FIGS. 3, 4, and 5 in a direction along the optical axis.

  The subject light is imaged on the CCD 40 through the opening 70 ′ of the flare prevention plate 70, the photographing lens, and the aperture unit 30, and an image signal representing the subject image is generated in the CCD 40. The generated image signal is roughly read out by the A / D unit 131, the analog signal is converted into a digital signal, and low resolution through image data is generated. The generated through image data is subjected to image processing such as white balance correction and γ correction in a white balance / γ processing unit 133.

  Here, a timing signal is supplied from the clock generator 132 to the CCD 40, and an image signal is generated at predetermined intervals in synchronization with the timing signal. The clock generator 132 outputs a timing signal based on an instruction from the main CPU 110 transmitted via the optical CPU 120. The timing signal is output from the CCD 40, the A / D unit 131 in the subsequent stage, the white balance The γ processing unit 133 is also supplied. Therefore, the CCD 40, the A / D unit 131, and the white balance / γ processing unit 133 perform image signal processing in order in synchronization with the timing signal generated from the clock generator 132.

  The image data subjected to the image processing in the white balance / γ processing unit 133 is temporarily stored in the buffer memory 134. The low-resolution through image data stored in the buffer memory 134 is supplied to the YC / RGB conversion unit 138 via the bus 140 first from the through image data stored at the old time. Since the through image data is an RGB signal, the YC / RGB conversion unit 138 does not perform processing, but directly transmits the image to the image display LCD 160 via the driver 139, and the through image represented by the through image data is displayed on the image display LCD 160. Is displayed. Here, in the CCD 40, subject light is read at every predetermined timing and an image signal is generated. Therefore, on the image display LCD 160, subject light in the direction in which the photographing lens is directed is always displayed as a subject image. to continue.

  The through image data stored in the buffer memory 134 is also supplied to the main CPU 110. Based on the through image data, the main CPU 110 detects the contrast of the subject image represented by the image signal repeatedly obtained by the CCD 40 while the focus lens 23 is moved along the optical axis, and the luminance of the subject. The detected contrast and brightness are transmitted to the optical control CPU 120.

  The optical control CPU 120 moves the focus lens 23 to a lens position where the contrast peak transmitted from the main CPU 110 is obtained (AF processing), and adjusts the aperture value of the aperture unit 30 according to the brightness transmitted from the main CPU 110. (AE processing).

  Here, when the photographer presses the shutter button 14 shown in FIG. 1 while confirming the through image displayed on the image display LCD 160, the main CPU 110 is notified that the shutter button 14 has been pressed, and further optical control is performed. This is transmitted to the CPU 120. When the subject is dark, a light emission instruction is transmitted from the optical control CPU 120 to the LED light emission control unit 150, and a flash is emitted from the LED 151 in synchronization with the pressing of the shutter button 14. Further, in accordance with an instruction from the optical control CPU 120, the image signal generated by the CCD 40 is finely read out by the A / D unit 131, and high-resolution captured image data is generated. The generated captured image data is subjected to image processing by the white balance / γ processing unit 133 and stored in the buffer memory 134.

  The captured image data stored in the buffer memory 134 is supplied to the YC processing unit 137 and converted from RGB signals to YC signals. The captured image data converted into the YC signal is subjected to compression processing in the compression / decompression unit 135, and the compressed captured image data is stored in the memory card 170 via the I / F 136.

  The captured image data stored in the memory card 170 is subjected to decompression processing in the compression / decompression unit 135, converted into RGB signals in the YC / RGB conversion unit 138, and then displayed on the image display LCD 160 via the driver 139. Reportedly. On the image display LCD 160, a captured image represented by the captured image data is displayed.

  The digital camera 1 is configured as described above.

  Here, in the digital camera 1 according to the present embodiment, the light transmission effective diameter of the flare prevention plate 70 is adjusted by applying / releasing the voltage according to the focal length to the flare prevention plate 70, and the optical opening 70. 'Is formed. First, the configuration of the flare prevention plate 70 and a method for adjusting the effective light transmission diameter of the flare prevention plate 70 will be described.

  FIG. 7 is a diagram for explaining the operation principle of the electrochromic element.

As shown in FIG. 7, the electrochromic element 200 applied to the present embodiment is an oxidation that develops color by depriving electrons between two transparent electrodes 211 and 212 (for example, ITO electrodes) and oxidizing them. A coloring layer 221 (for example, Irox) is sandwiched between a reducing coloring layer 222 (for example, WO _{3 and the} like) that develops color by being reduced by being given electrons, and further, an oxidation coloring layer 221 and a reducing coloring layer. A transparent insulating layer 230 (for example, Ta ₂ O ₅ or SiO ₂ ) is sandwiched between the layers 222.

  When no voltage is applied to the electrochromic element 200, as shown in FIG. 7A, the oxidation coloring layer 221 and the reduction coloring layer 222 are not colored, and the electrochromic element 200 has high light transmittance. Thus, the light L can pass through the electrochromic element 200.

  When a voltage with a polarity is applied from the voltage application unit 200 ′ to the electrochromic element 200, the polarity is such that the left transparent electrode 211 in contact with the oxidation coloring layer 221 is the anode and the right transparent electrode 212 in contact with the reduction coloring layer 222 is the cathode The left transparent electrode 211 removes electrons from the oxidation coloring layer 221 and discharges electrons from the right transparent electrode 212 to the reduction coloring layer 222. As shown in FIG. 7B, the oxidation coloring layer 221 and the reduction coloring layer 221 are reduced. Layer 222 develops color. As a result, the light transmittance of the electrochromic element 200 is reduced, and the light L is blocked by the electrochromic element 200.

  Further, when the voltage application from the voltage application unit 200 ′ is stopped, the oxidation reaction in the oxidation coloring layer 221 and the reduction reaction in the reduction coloring layer 222 disappear, and as shown in FIG. The color disappears and the light transmission is improved.

  The flare prevention plate 70 of the present embodiment uses an electrochromic element having the above-described characteristics.

  FIG. 8 is a schematic configuration diagram when the flare prevention plate 70 is viewed from the front.

  The flare prevention plate 70 includes a black plate 71 having a through-hole 71a and three electrochromic elements 72, 73, and 74 having the same configuration as the electrochromic element 200 shown in FIG. The electrochromic elements 72, 73, 74 have different through holes and are arranged concentrically inside the through holes 71 a of the plate 71. The electrochromic elements 72, 73, and 74 correspond to an example of a plurality of segments referred to in the present invention.

  The voltage application unit 70a is connected to each of the electrochromic elements 72, 73, and 74, and can individually control the application / release of the voltage to the electrochromic elements 72, 73, and 74. When no voltage is applied to all the electrochromic elements 72, 73, 74, the electrochromic elements 72, 73, 74 are decolored as shown in FIG. The opening 70 'is opened to the maximum. Further, when a voltage is applied in order from the outermost electrochromic element 72, the opening 70 'of the flare prevention plate 70 is reduced as the electrochromic element is colored, and all the electrochromic elements 72, 73,. In the state where the voltage is applied to 74, the opening 70 'of the flare prevention plate 70 is narrowed to the minimum as shown in FIG. In the present embodiment, the opening 70 ′ of the flare prevention plate 70 can be adjusted in four stages by individually controlling the application / release of voltage from the voltage application unit 70 a to the electrochromic elements 72, 73, 74. it can.

  The optical opening 70 ′ provided in the flare prevention plate 70 is adjusted as described above.

  Next, the focal length and the size of the optical opening 70 ′ of the flare prevention plate 70 will be described.

  FIG. 9 is a diagram illustrating the relationship between the effective lens diameter at the shortest focal length and the opening 70 ′ of the flare prevention plate 70.

  The photographing lens functions as a telephoto lens when the focal length (the distance between the rear lens group 22 and the CCD 40) is long, and functions as a wide-angle lens when the focal length is short.

  As shown in FIG. 9A, when the rear group lens 22 is moved away from the front group lens 21 and moved to the position of the shortest focal length, the shooting angle of view is wide and not only in front of the front group lens 21. All light incident from above or below the front lens group 21 is also read by the CCD 40 and used to generate photographed image data.

  When the shortest focal length is selected, the voltage application from the voltage application unit 70a shown in FIG. 8 to all the electrochromic elements 72, 73, 74 is stopped. As a result, as shown in FIG. 9B, the electrochromic elements 72, 73, and 74 are decolored, and the effective light transmission diameter W1 of the flare prevention plate 70 is adjusted according to a wide shooting angle of view, so that the optical Opening 70 'is formed. By taking a picture in this state, light incident from above or below the front lens group 21 is not blocked by the flare prevention plate 70, and a problem that a part of the photographed image becomes dark is avoided.

  FIG. 10 is a diagram illustrating the relationship between the effective lens diameter at the longest focal length and the opening 70 ′ of the flare prevention plate 70.

  As shown in FIG. 10A, when the rear group lens 22 is moved closer to the front group lens 21 and moved to the position of the longest focal length, the shooting angle of view narrows, and the upper and lower sides of the front group lens 21 are photographed. Out of angle of view. For this reason, light incident from above or below the front lens group 21 was used to generate a captured image at the shortest focal length shown in FIG. 9A, but the longest focal length shown in FIG. Sometimes it becomes unnecessary, and when this light becomes harmful light and reaches the CCD 40, a ghost or flare occurs in the photographed image.

  When the longest focal length is selected, a voltage is applied to all the electrochromic elements 72, 73, 74 from the voltage application unit 70a shown in FIG. As a result, as shown in FIG. 10B, the electrochromic elements 72, 73, and 74 are colored, and the light transmission effective diameter W2 of the flare prevention plate 70 (light transmission effective diameter W2 at the longest focal distance <shortest focal distance). The effective light transmission diameter W1) is adjusted to a size suitable for a narrow shooting angle of view, and an optical aperture 70 'is formed. When photographing is performed in this state, light incident from above or below the front lens group 21 is blocked by the flare prevention plate 70, and light incident from within the light transmission effective diameter W2 reaches the CCD 40. A problem that a ghost occurs in the captured image is avoided with high accuracy, and a problem that a part of the captured image becomes dark is also avoided.

  As described above, the shooting angle of view becomes narrower as the focal length becomes longer, and the shooting angle of view becomes wider as the focal length becomes shorter. In the digital camera 1 of the present embodiment, an electrochromic for adjusting the focal length and the effective light transmission diameter of the flare prevention plate 70 to a size corresponding to the shooting angle of view at the focal length is added to the EEPROM 110a shown in FIG. The voltage application / release state to each of the elements 72, 73, 74 is stored in association with each other.

  When the photographer changes the shooting angle of view using a cross key (not shown) provided in the digital camera 1, the main CPU 110 calculates a focal length corresponding to the changed shooting angle of view, and calculates from the EEPROM 110a. The voltage application / release state associated with the focal length is acquired, and the acquired voltage application / release state is transmitted to the optical control CPU 120.

  The optical control CPU 120 transmits an instruction to apply the voltage transmitted from the main CPU 110 to the voltage application unit 70 a, and the voltage application unit 70 a applies the instructed voltage to the flare prevention plate 70.

  The anti-flare plate 70 is optically adjusted by the electrochromic elements 72, 73, 74 depending on the applied voltage, adjusted to the size corresponding to the field angle of view at the focal length for which the light transmission effective diameter is calculated. An opening 70 'is formed. As a result, the light incident from outside the shooting angle of view is blocked by the flare prevention plate 70, and only the light incident from within the shooting angle of view reaches the CCD 40 and is used for generating the captured image data. Therefore, according to the digital camera 1 of the present embodiment, it is possible to avoid a ghost with high accuracy regardless of the focal length (shooting angle of view), and to acquire a high-quality shot image. Furthermore, since no motor or the like is used for the flare prevention plate 70, power consumption can be suppressed and the digital camera 1 can be miniaturized.

  Above, description of 1st Embodiment of this invention is complete | finished and 2nd Embodiment of this invention is described. In the second embodiment of the present invention, since the elements other than the flare prevention plate have substantially the same configuration as the first embodiment, the same elements are denoted by the same reference numerals, description thereof is omitted, and differences are noted. Only explained.

  Unlike the flare prevention plate 70 of the first embodiment, the flare prevention plate of this embodiment controls the light transmittance using a liquid crystal element instead of an electrochromic element. As light transmittance control using liquid crystal elements, holographic liquid crystal system, cholesteric liquid crystal selective reflection system, guest host system, polymer dispersed liquid crystal system (PDLC), etc. are known. The method will be described in detail.

  FIG. 11 is a diagram for explaining the principle of operation of the liquid crystal element.

  In the guest-host method, a liquid crystal element in which a nematic liquid crystal 301 having a property that the orientation of liquid crystal molecules 301a changes according to the frequency of an alternating voltage and a dichroic dye 302 that absorbs light are enclosed in a transparent container. 300 is applied.

  The liquid crystal molecules 301a have an almost ellipsoidal shape. When a low-frequency AC voltage is applied, the major axis of the ellipsoid is parallel to the direction of the electric field, and when the high-frequency AC voltage is applied, the major axis of the ellipsoid is It has the property of being orthogonal to the direction of the electric field.

  The dichroic dye 302 is dissolved in the nematic liquid crystal 301 and changes its arrangement in the same manner as the liquid crystal molecules 301a with respect to the change in the frequency of the alternating voltage. The dichroic dye 302 also has an approximately ellipsoidal shape, and absorbs light when the major axis of the ellipsoid and the incident direction of light are orthogonal to each other. However, the major axis of the ellipsoid and the incident direction of light are absorbed. When is parallel, it does not absorb light.

  When a low-frequency AC voltage is applied to the liquid crystal element 300, the liquid crystal molecules 301a and the dichroic dye 302 are aligned in a direction parallel to the incident direction of the light L, as shown in FIG. In this state, since the light L is not absorbed by the dichroic dye 302, the light L is transmitted through the liquid crystal element 300.

  When a high-frequency AC voltage is applied to the liquid crystal element 300, the liquid crystal molecules 301a and the dichroic dye 302 are aligned in a direction orthogonal to the incident direction of the light L as shown in FIG. As a result, the light L is absorbed by the dichroic dye 302, the transmittance of the liquid crystal element 300 is reduced, and the light L is blocked by the liquid crystal element 300.

  As described above, the liquid crystal element 300 can adjust the light transmittance by controlling the frequency of the applied AC voltage. In the present embodiment, a flare prevention plate 80 constituted by a liquid crystal element 300 is applied instead of the flare prevention plate 70 constituted by an electrochromic element shown in FIG.

  FIG. 12 is a schematic configuration diagram of the flare prevention plate 80 of the present embodiment.

  The flare prevention plate 80 of this embodiment includes a liquid crystal element 81 having the same configuration as the liquid crystal element 300 shown in FIG. 11 and a light-transmissive liquid crystal drive circuit 82 that applies an AC voltage to the liquid crystal element 81. Yes.

  Similarly to the liquid crystal element 300 shown in FIG. 11, the liquid crystal element 81 is configured by enclosing a nematic liquid crystal 301 in which liquid crystal molecules 301a and a dichroic dye 302 are dissolved in a transparent container, and an AC voltage is applied to the liquid crystal element 81. Then, the portion to which the AC voltage is applied is adjusted to a light transmittance corresponding to the frequency of the AC voltage.

  In the liquid crystal driving circuit 82, a set of transparent electrodes and transparent transistors is arranged in a two-dimensional matrix, and the AC voltage applied from each transparent electrode is individually controlled by each transparent transistor, whereby the liquid crystal element 81 is provided. The AC voltage applied to can be finely adjusted in a matrix. That is, according to the flare prevention plate 80, the distribution of light transmittance can be formed in a desired pattern by adjusting the AC voltage applied from the liquid crystal drive circuit 82 to the liquid crystal element 81.

  Here, the subject light L that has passed through the photographing lens 30 shown in FIG. 6 often has a smaller amount of light at the periphery of the imaging surface on which the CCD 40 is arranged, compared to the center, and the obtained photographing. The peripheral part of the image may be darker than the central part. In addition, since the light amount distribution on the imaging surface changes depending on the focal length, the aperture value (F value) of the stop, etc., there is a problem that it is difficult to correct the brightness of the captured image by image processing or the like. . The flare prevention plate 80 of the present embodiment is designed to avoid image defects such as ghosts and flares and to make the light quantity distribution uniform on the imaging plane.

  FIG. 13 is a diagram showing a light transmittance distribution when the flare prevention plate 80 is viewed from the front.

  In FIG. 13, the portion with a lower light transmittance is expressed darker and the portion with a higher light transmittance is expressed lighter.

  Also in the present embodiment, as in the case of the flare prevention plate 70 of the first embodiment described with reference to FIGS. 9 and 10, the light transmission effective diameter W <b> 3 is determined to be a size according to the shooting angle of view. When a high-frequency AC voltage is applied to the outer portion 801 of the light transmission effective diameter W3 of the flare prevention plate 80, the light transmittance of the outer portion 801 is reduced to form an optical opening 80 ′. That is, as the focal length is shorter (the shooting angle of view is wider), an opening 80 'having a larger aperture diameter (light transmission effective diameter W3) is formed, and as the focal length is longer (the shooting angle of view is narrower), An opening 80 'having a small transmission effective diameter W3) is formed.

  Further, an AC voltage having a higher frequency at the center and a lower frequency at the periphery is applied to the inner portion 802 of the light transmission effective diameter W3 of the liquid crystal element 81. As a result, the inner portion 802 of the effective light transmission diameter W3 has a light transmittance enough to allow light to pass therethrough, and a distribution of light transmittance that is lower at the center and higher at the periphery is formed.

  In the flare prevention plate 80, light incident from outside the shooting angle of view is absorbed by the outer portion 801, and only light incident from within the shooting angle of view passes through the inner portion 802. Normally, the light reaching the imaging plane has a larger amount of light at the center as compared with the periphery, but the light that has passed through the inner portion 802 of the light transmission effective diameter W3 is greatly attenuated at the center. A uniform light amount distribution is formed on the image plane. Therefore, according to the flare prevention plate 80 of the present embodiment, it is possible to avoid image defects such as ghosts and flares, and to obtain a high-quality captured image having uniform brightness.

  Here, in the above description, the example in which the stop is disposed between the front group lens and the rear group lens has been described. However, the light shielding member according to the present invention is disposed, for example, between the rear group lens and the focus lens. It may be used as an aperture.

  In the above description, an example in which the amount of light is uniformed using a liquid crystal element has been described. However, the light shielding member referred to in the present invention may be one in which the amount of light is uniformed using an electrochromic element.

  In the above description, an example in which the optical lens barrel according to the present invention is applied to a digital camera has been described. However, the optical lens barrel of the present invention is, for example, a mobile phone or a silver salt camera that forms an image of subject light on a film. You may apply to.

1 is an external perspective view of a digital camera to which an embodiment of the present invention is applied. 1 is an external perspective view of a digital camera to which an embodiment of the present invention is applied. It is sectional drawing which cut | disconnected the lens barrel in the retracted state of a digital camera along the optical axis. It is sectional drawing which cut | disconnected the lens barrel in which the imaging lens of a digital camera is a wide state along the optical axis. It is sectional drawing which cut | disconnected the lens barrel in which the imaging lens of a digital camera is in a tele state along the optical axis. It is a schematic internal block diagram of the digital camera shown in FIG. It is a figure for demonstrating the principle of operation of an electrochromic element. It is a schematic block diagram when a flare prevention board is seen from the front. It is a figure which shows the relationship between the lens effective diameter in shortest focal distance, and opening of a flare prevention board. It is a figure which shows the relationship between the lens effective diameter in the longest focal distance, and opening of a flare prevention board. It is a figure for demonstrating the principle of operation of a liquid crystal element. It is a schematic block diagram of the flare prevention board of 2nd Embodiment. It is a figure which shows distribution of the light transmittance when a flare prevention board is seen from the front.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Digital camera 10 Lens barrel 12 Auxiliary light emission window 13 Finder objective window 14 Shutter button 21 Front group lens 22 Rear group lens 23 Focus lens 24 Guide lot 24a Stopper 25 Rear group lens holding frame 26 Coil spring 27 Rear group lens unit 30 Diaphragm unit 31 Diaphragm blade 32 Aperture plate 40 CCD
50 fixed cylinder 50a protrusion 50b key groove 51 gear 52 drive cylinder 52a key groove 53 rotational movement cylinder 54 cam follower 55 rectilinear movement frame 55a key groove 56 rectilinear movement cylinder 61 lead screw 62 focus lens holding frame 63 cam follower 70, 80 flare prevention plate 70a Voltage application unit 70 ', 80' Opening 71 Plate 71a Through hole 72, 73, 74 Electrochromic element 81 Liquid crystal element 82 Liquid crystal drive circuit 101 Switch group 110 Main CPU
110a EEPROM
120 Optical control CPU
131 A / D unit 132 Clock generator 133 White balance / γ processing unit 134 Buffer memory 135 Compression / decompression unit 136 I / F
137 YC processing unit 138 YC / RGB conversion unit 139 driver 140 bus 150 LED light emission control unit 151 LED
160 Image display LCD
170 Memory Card 200 Electrochromic Element 200 ′ Voltage Application Section 211, 212 Transparent Electrode 221 Oxidation Coloring Layer 222 Reduction Coloring Layer 300 Liquid Crystal Element 301 Nematic Liquid Crystal 301a Liquid Crystal Molecule 302 Dichroic Dye

Claims (7)

In an optical barrel containing a variable focal length optical system that forms an image of subject light,
A light-shielding member that is arranged on the optical path to prevent outside light from entering other than the subject imaged by the optical system, and changes the effective light transmission diameter by applying and releasing a voltage according to the focal length of the optical system. And an optical lens barrel.   The optical barrel according to claim 1, wherein the light shielding member is composed of an electrochromic element.   The optical barrel according to claim 1, wherein the light shielding member is formed of a liquid crystal element.   The light shielding member has a plurality of concentrically arranged segments that change transmittance by applying and releasing voltage so that the effective light transmission diameter is concentrically changed in a plurality of stages. The optical barrel according to claim 1.   The light shielding member is configured to change a light transmission effective diameter by applying and releasing a voltage and to flatten a light amount distribution between a center and a periphery on an imaging surface of a subject image by the optical system. The optical barrel according to claim 1. An optical barrel according to claim 1;
Control means for controlling the effective light transmission diameter of the light shielding member to the effective light transmission diameter according to the focal length of the optical system by applying and releasing a voltage according to the focal length of the optical system to the light shielding member. An imaging optical system characterized by that. An imaging optical system according to claim 6;
An imaging device, comprising: an imaging device disposed on an imaging plane of the subject image of the optical system.

Images