JP2005156649A - Imaging unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging unit with which a high definition image is obtained while combining compact configuration and shock resistance. <P>SOLUTION: An interlace scanning system CCD is adopted as a solid state image pickup device 8 by providing a mechanical shutter device, thus, the imaging unit is miniaturized, a drive mechanism is miniaturized, power consumption is reduced and enhancement of the shock resistance by mass reduction of the imaging lens, etc. is expected by reducing mass of an imaging lens, etc. to be driven by the drive mechanism by fixing the mechanical shutter device to the side of a lens barrel 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a small imaging device that can be mounted on a portable terminal or the like.

  In recent years, along with the improvement in performance and size of solid-state imaging devices such as CCD (Charged Coupled Device) type image sensors or CMOS (Complementary Metal Oxide Semiconductor) type image sensors, PDA (Personal Digital Assistants) is becoming widespread. In addition, there is an increasing demand for further downsizing of imaging lenses mounted on these imaging apparatuses.

Here, the conventional small-sized imaging device does not have a mechanical shutter device or an AF mechanism used in a general consumer digital camera, and the number of pixels of the mounted solid-state imaging device. Since it is relatively low, there is no problem with the difficulty of miniaturization (see Non-Patent Document 1 and Patent Document 1).
"Optics", published by Japan Optical Society (Applied Physics Society), Vol31, No. 9 (2002), 687-689pp JP 2003-37758 A

  However, recently, in addition to the demand for downsizing of the imaging device, there is also a demand for higher image quality. Here, it is conceivable to first increase the number of pixels of the solid-state imaging device in response to a request for high image quality. However, in the case of a progressive scanning CCD that has been used in the past, the light receiving area of the solid-state imaging device is determined according to the number of pixels, although there is a feature that a mechanical shutter device is not required because signals of all pixels can be read at once. However, there is a problem that the image pickup apparatus cannot be reduced in size.

  On the other hand, there is an attempt to use an interlace scanning CCD for an imaging apparatus. Interlaced scanning CCDs read out the signals of all the pixels in two steps, and the light receiving area can be reduced with respect to the number of pixels of the output signal. There is a possibility that both can be realized. However, in order to read out the signals of all the pixels in two steps, it is necessary to block the light flux reaching the light receiving surface of the solid-state imaging device using a mechanical shutter device between the first reading and the subsequent reading. is there.

  On the other hand, when the number of pixels of the solid-state imaging device is increased, a focus shift that does not cause a problem in the conventional imaging device using the solid-state imaging device having a low pixel becomes apparent. On the other hand, if the imaging lens is moved in the optical axis direction by providing an AF mechanism, it is possible to focus on a subject within a range of several centimeters from an infinite distance. Compared with a conventional image pickup apparatus including the image pickup lens and the low-pixel solid-state image pickup device, it is possible to obtain a much higher quality image.

  However, in a general consumer digital camera, the shutter mechanism is moved together with the imaging lens for AF driving. However, if such a small imaging device is also moved together, It is necessary to use an actuator having a high driving force so that the AF driving time can be shortened in consideration of the mass, and there is a problem that the imaging apparatus cannot be reduced in size and power consumption cannot be reduced. When an imaging device is mounted on a mobile phone or the like that operates with a small battery, it is an important issue to reduce power consumption. Furthermore, when the imaging device is mounted on a mobile phone, it is expected that the user will drop the mobile phone. In that case, if the mechanical shutter device and the imaging lens are integrated, the AF device can withstand the impact of the drop. However, there is also a problem that the imaging apparatus cannot be reduced in size.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an imaging apparatus capable of obtaining a high-quality image while having a compact configuration and impact resistance.

  The imaging apparatus according to claim 1, wherein the imaging lens includes: a solid-state imaging device; a lens barrel; an imaging lens that is movably held in the lens barrel and includes an aperture stop that is disposed closest to the object; Since it has a drive mechanism for driving in the optical axis direction with respect to the lens barrel and a mechanical shutter device fixed to the lens barrel, the solid state can be obtained by using the mechanical shutter device. An interlaced scanning CCD can be adopted as the imaging device, thereby reducing the size of the imaging device, and fixing the mechanical shutter device to the lens barrel so that the imaging lens driven by the drive mechanism, etc. The mass can be reduced, whereby the drive mechanism can be reduced in size and power consumption, and the impact resistance can be improved by reducing the mass of the imaging lens and the like. In addition, by using an imaging lens having an aperture stop located closest to the object side, the entrance pupil position becomes the aperture stop position, so the aperture of the shutter can be reduced. Note that the aperture of the shutter depends on the angle of view and the amount of autofocus movement (which varies depending on the focal length), and also contributes to determining the size of the imaging apparatus in the direction perpendicular to the optical axis. Therefore, in order to obtain a compact imaging device, it is necessary to appropriately set specifications such as the angle of view and the focal length of the imaging lens.

  Note that there is AF driving as driving of the imaging lens. The AF drive is generally known as a conventional imaging lens focusing method, in which the entire imaging lens is moved integrally to the object side during short-distance shooting, but a focusing method using floating may be used. . Here, the floating method is a method in which the two lens groups move at different speeds in the optical axis direction during focusing. Although the AF mechanism is slightly more complicated in the floating method than in the entire payout method, it is possible to focus on the center of the image in the overall payout method, but the peripheral image area flows, so the peripheral part This method solves the problem that the image of the image deteriorates. Further, focusing may be performed by moving only one lens group out of the plurality of lens groups, which makes it possible to further reduce the size and weight of the AF mechanism. AF driving may be performed based on a signal from a separate distance measuring sensor, or may be performed based on a result of image processing of an image signal from a solid-state imaging device.

  The image pickup apparatus according to claim 2, wherein the mechanical shutter device moves adjacent to the aperture stop between an open position that allows passage of outside light and a shielding position that blocks passage of outside light. It has a free shutter blade.

  According to a third aspect of the present invention, there is provided the imaging apparatus according to the first or second aspect, further comprising: a light transmittance adjusting unit capable of inserting / removing a changing member that changes the light transmittance in the optical path of the imaging apparatus. Features.

  In the imaging apparatus, the mechanical shutter device is separate from the imaging lens, and the imaging lens moves in the optical axis direction. Therefore, there is a certain amount of space between the mechanical shutter device and the imaging lens. The interval of occurs. Accordingly, since the F-number cannot be changed by using the mechanical shutter device as a small aperture, the amount of light incident on the imaging lens cannot be suppressed, and the amount of light incident on the pixels of the solid-state imaging device. May become excessive. Therefore, in the present invention, when the subject brightness is high, appropriate exposure can be achieved by inserting the changing member into the optical path. The “change member” is not limited to the ND filter having a low light transmittance, but may be another filter, for example, an optical filter such as a UV cut filter, or a wide converter lens or a teleconverter lens that converts a focal length. .

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the imaging lens is characterized in that all the lenses are made of a plastic material.

If all the lenses constituting the imaging lens are made of, for example, plastic lenses manufactured by injection molding, mass production becomes possible, and lens performance can be improved because it is easy to add an aspherical surface. Further, the weight of the lens unit can be reduced, and the load applied to the AF actuator as the driving device can be reduced. On the other hand, there is a problem that the image point position fluctuates due to a change in the refractive index of the plastic material due to a change in the outside air temperature. It doesn't matter so much. Strictly speaking, in an imaging apparatus having a function such as a mode for fixing the focus at a focal distance or infinity even if the AF mechanism is mounted, another means for correcting the fluctuation of the image point position is required. . In such a case, a separate temperature sensor may be mounted and correction such as fine adjustment of the distance between the imaging lens and the imaging surface of the solid-state imaging device may be performed based on temperature information from the temperature sensor. Recently, it has been found that inorganic fine particles can be mixed in a plastic material to suppress the temperature change of the refractive index of the plastic material to a small value. To explain in detail, mixing fine particles with a transparent plastic material generally causes light scattering and decreases the transmittance, so that it was difficult to use as an optical material. By making it smaller than the wavelength, scattering can be substantially prevented. The refractive index of the plastic material decreases with increasing temperature, but the refractive index of inorganic particles increases with increasing temperature. Therefore, it is possible to make almost no change in the refractive index by using these temperature dependencies so as to cancel each other. Specifically, by dispersing inorganic particles having a maximum length of 20 nanometers or less in a plastic material as a base material, a plastic material with extremely low temperature dependency of the refractive index is obtained. For example, by dispersing fine particles of niobium oxide (Nb ₂ O ₅ ) in acrylic, the refractive index change due to temperature change can be reduced. By using such a plastic material in which inorganic particles are dispersed, it is possible to suppress the fluctuation of the image point position when the temperature of the entire imaging lens system changes. By using such a plastic material, it is not necessary to separately mount a temperature sensor, and the AF mechanism can be further simplified and reduced in size and weight. Here, “formed from a plastic material” includes a case where a plastic material is used as a base material and the surface thereof is coated for the purpose of preventing reflection and improving surface hardness.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of the imaging apparatus according to the present embodiment. In FIG. 1, in the center of a lens barrel 1, in order from the object side, a dustproof cover 2, a shutter blade 24, an aperture stop 4, a plastic positive lens 5, a plastic negative lens 6, an optical low-pass filter (object side surface) (7), an interlace scanning CCD solid-state imaging device 8 is disposed. An imaging lens composed of an aperture stop 4, a positive lens 5, and a negative lens 6 is fixed to a lens frame 9. In the lens frame 9, a screw shaft 10 a that is an output shaft of an AF motor (actuator) 10 fixed to the lens barrel 1 is screwed onto an arm 9 a that extends in the direction orthogonal to the optical axis from the outer peripheral surface thereof. When the AF motor 10 is driven and the screw shaft 10a rotates, the imaging lens can move in the optical axis direction integrally with the lens frame 9 according to the amount of rotation. The AF motor 10 and the lens frame 9 constitute a drive mechanism.

  A mechanical shutter device 20 (simply shown in FIG. 1) is disposed between the dust cover 2 and the aperture stop 4. Hereinafter, the mechanical shutter device 20 will be described.

  FIG. 2 is a plan view of the mechanical shutter device 20 as viewed from the subject side, and FIGS. 3 to 6 are plan views showing the blade chambers in each operation state. First, the configuration of the present embodiment will be described with reference to FIGS. In the present embodiment, a blade chamber is formed between a main ground plate 21 disposed on the subject side and an auxiliary ground plate 22 disposed on the imaging element side. The two ground planes 21 and 22 are both made of synthetic resin and have almost the same outer shape, and exposure openings (maximum apertures) are formed by circular openings 21a and 22a formed in the substantially central portions thereof. It is regulated. In addition, in FIG. 3, although the main external shape of the main ground plane 21 is shown with the dashed-two dotted line, this point is the same also in the case of FIGS.

  Next, the configuration of the front side of the main ground plate 21 will be described mainly using FIG. First, three attachment portions 21b, 21c, and 21d used for attachment to the lens barrel 1 (FIG. 1) are provided so as to surround the opening 21a. Two motors 23 and 24 are attached by hooks 21e and 21f formed integrally with the main base plate 21 and screws 25 and 26, respectively. These motors 23 and 24 are motors called moving magnet type motors described in JP 2000-60088 A and the like, and since their configurations are well known, a detailed description of the configuration is omitted. The permanent magnet rotor rotates only within a predetermined angle range, and the drive pins 23a and 24a provided in the portions projecting radially from the permanent magnets through the long holes 21g and 21h formed in the main base plate 21. It is inserted into the blade chamber.

  Furthermore, although the structure of the back side of the main ground plate 21 is demonstrated, first, the site | part which is shown by FIG. 2 but is not shown by FIG. 3 is demonstrated. The main ground plate 21 and the auxiliary ground plate 22 are attached to each other by hooking a hook portion 21 i provided on the main ground plate 21 to the edge of the auxiliary ground plate 22 and inserting a screw (not shown) from the back side of the auxiliary ground plate 22. 22 is inserted into the hole 22b (see FIG. 3) and screwed into the mounting portion 21j of the main base plate 21. The mounting portion 21j also serves as a spacer between the main base plate 21 and the auxiliary base plate 22. In addition, the main base plate 21 is provided with dedicated spacers 21k, 21m, 21n, and 21p. Yes.

  Moreover, in FIG. 3, the site | part provided in the back side of the main base plate 21 is shown with the cross section with the above-mentioned drive pins 23a and 24a. The main base plate 21 is provided with stoppers 21q, 21r, 21s, and 21t for each operation member described later. Further, shafts 21 u, 21 v, 21 w are provided on the back side of the main base plate 21. Among them, a shutter blade 27 is rotatably attached to the shaft 21u, and a shutter blade 28 is rotatably attached to the shaft 21v. The shutter blades 27 and 28 are arranged so that the shutter blade 27 is on the subject side, and the drive pins are fitted into the long holes 27a and 28a formed in the shutter blades 27 and 28, as is well known. Match.

  A diaphragm member 29 disposed on the auxiliary base plate 22 side of the shutter blade 28 is rotatably attached to the other shaft 21w. The diaphragm member 29, which is a light transmittance adjusting means, has a long hole 29a and a circular opening 29b having a diameter smaller than that of the exposure openings (openings 21a and 22a). The drive pin 24a is fitted. Further, a sheet-like ND filter (change member) 30 is attached to the rear side of the aperture member 29 and covers the opening 29b. The ND filter 30 operates in a recess 22c formed in the auxiliary ground plate 22 so as not to slide on the auxiliary ground plate 22 during operation of the throttle member 29.

  Next, the operation of the present embodiment will be described with reference to FIGS. FIG. 3 shows an initial state, that is, an open position. That is, this imaging apparatus is a normally open type, and when the power is on, the diaphragm member 29 is retracted from the exposure opening, and the shutter blades 27 and 28 are shown. The aperture stop 4 (FIG. 1) is fully opened. Therefore, the solid-state imaging device 8 is exposed to subject light, and the subject image can be observed with an external monitor (not shown). At this time, the motors 23 and 24 are not energized. However, with a well-known motor configuration, the rotor of the motor 23 is given a counterclockwise rotating force, and the rotor of the motor 24 rotates clockwise. The power to do is given. Therefore, the shutter blades 27 and 28 are brought into contact with the stoppers 21q and 21t, and the aperture member 29 is brought into contact with the stopper 21s.

  When the release button is pressed in this state, whether to shoot with or without reducing the light amount of the subject is determined based on the measurement result of the subject light. If it is decided to shoot with the light quantity of the subject reduced, the rotor of the motor 24 is rotated counterclockwise, and the diaphragm member 29 is rotated clockwise. Then, the diaphragm member 29 slides with respect to the shutter blade 28, and the tip of the diaphragm member 29 comes into contact with the stopper 21r and stops. That is, the slidable contact relationship between the diaphragm member 29 and the shutter blade 28 is always maintained from the start to the stop thereof. FIG. 4 shows the state stopped in this way, that is, the state where the ND filter 30 is inserted in the optical path. At this time, the power supply to the motor 24 may not be cut off, but even if it is cut off, this state is maintained by a known motor configuration. Depending on the specifications of the imaging apparatus, this state may not be obtained by a release, but may be automatically obtained according to subject light.

  In this way, when the state of FIG. 4 is obtained, a shooting start signal is then given to the imaging device. When a predetermined photographing time has elapsed, the motor 23 is energized from the control circuit, and the rotor is rotated clockwise. Therefore, the shutter blades 27 and 28 rotate in opposite directions. At this time, the shutter blades 28 slide with respect to the diaphragm member 29. And after closing the opening part 29b, it contacts and stops to the stoppers 21t and 21q. That is, the shutter blade 28 always maintains a sliding contact relationship with the aperture member 29 until the shutter blade 28 stops operating. The stop state, that is, the shielding position is shown in FIG.

  Thereafter, when the image signal is transferred to a storage device (not shown) in this closed state, the motors 23 and 24 are energized before and after. However, at this time, unlike the above case, since the current is supplied in the opposite direction, both the shutter blades 27 and 28 and the diaphragm member 29 are rotated in the opposite direction. The sliding contact relationship between the blades 28 and the diaphragm member 29 is maintained from the beginning to the end. The shutter blades 27 and 28 come into contact with the stoppers 21q and 21t, and the diaphragm member 29 comes into contact with the stopper 21s and is stopped. Immediately thereafter, the motors 23 and 24 are de-energized to the initial state shown in FIG. Return.

  In this embodiment, since the solid-state imaging device is an interlaced CCD, it is necessary to read out pixel signals corresponding to an image of one frame in two steps. Therefore, the mechanical shutter device 20 is operated at a predetermined timing after the focusing is completed, and the shutter blades 27 and 28 are driven to expose the aperture stop 4 for a predetermined period, and then shield and expose again. Thereby, an appropriate pixel signal can be obtained. By moving the shutter blades 27 and 28 in this manner, the imaging lens, the optical low-pass filter 7, and the cover glass (parallel plate) 8a of the solid-state imaging device 8 are passed through the imaging lens 8b with a predetermined exposure amount. The imaged optical image is photoelectrically converted by the solid-state imaging device 8 and further converted into an image signal by performing predetermined processing.

  Further, when the subject light is not relatively bright and the image is taken without using the opening 29b as described above, in the state shown in FIG. When a predetermined photographing time has elapsed, the motor 23 is energized from the control circuit, and the rotor is rotated in the clockwise direction. Therefore, the shutter blades 27 and 28 rotate in opposite directions. At this time, the shutter blades 28 slide with respect to the diaphragm member 29. Finally, the shutter blades 27 and 28 are stopped in the state shown in FIG. 6, that is, in the shielding position, as described above, but during that time, the sliding contact relationship between the shutter blades 28 and the diaphragm member 29 is maintained throughout. Maintained. Accordingly, the shutter blades 27 and 28 are thereafter returned to the state shown in FIG. 3 without needing to be described, but the sliding contact relationship between the shutter blades 28 and the diaphragm member 29 is maintained even at that time. .

  Thus, according to the present embodiment, in any operating state, a part of the shutter blade 28 and a part of the diaphragm member 29 are always kept in contact with each other, and their contact areas are continuously changed. Since the shutter blades 28 and the diaphragm member 29 are not engaged with each other, the shutter blades 28 and the part thereof are always in contact with each other. There is no possibility that the shutter blade 27 and the diaphragm member 29 are engaged with each other. Therefore, as described in the above publication, there is no need to partition the two blade chambers by a plate member (intermediate plate), so the area near the exposure opening is at least as thin as the plate member (intermediate plate). In addition, since such a plate member (intermediate plate) becomes unnecessary, the cost can be reduced.

  In this embodiment, an aperture 29b having a smaller diameter than the exposure aperture is formed in the diaphragm member 29 and covered with the ND filter 30. However, depending on the specifications of the imaging apparatus, the ND filter 30 is used. It is also possible to simply form the opening 29b without using. In this case, a plurality of openings having different apertures that are smaller than the exposure aperture may be formed in the aperture member 29 and rotated by a stepping motor so that a desired aperture can be selected. In addition, it is also possible to cover some of the openings with an ND filter, and in that case, when there are a plurality of openings to be covered with the ND filter, the openings having the same size may be covered with the concentration. It may be covered with a different ND filter.

  Further, as in this embodiment, the aperture member 29 may not be provided with the opening 29b, and the aperture member 29 may be manufactured only from the sheet material of the ND filter. However, in such a configuration, although it is a light quantity control member, it is no longer a diaphragm member. In addition, there is a known diaphragm mechanism whose aperture is controlled by a plurality of diaphragm blades. Even in this case, the diaphragm blade closest to the shutter blade is in any operating state. The object of the present invention can be achieved if the sliding contact relationship between the adjacent shutter blades is always maintained. In this embodiment, the two shutter blades 27 and 28 are employed. However, the present invention can be applied even when the number of the shutter blades is one.

  Further, the shape of the opening need not be circular, and may be rectangular as long as the angle of view in the short side direction, long side direction, and diagonal direction at the opening is ensured. By making the shape of the opening rectangular or the like, the retracted position of the shutter blade can be effectively ensured, leading to the downsizing of the imaging device. In addition, since unnecessary light incident on the outside of the effective diameter of the imaging lens can be removed, it is possible to suppress the occurrence of ghost and flare.

  According to the present embodiment, by providing a mechanical shutter device, an interlace scanning CCD can be adopted as the solid-state imaging device 8, whereby the imaging device can be reduced in size and the mechanical shutter device can be used as the lens barrel 1. By fixing to the side, the mass of the imaging lens driven by the drive mechanism is reduced, so that the drive mechanism is reduced in size and power consumption, and the imaging device is mounted by reducing the mass of the imaging lens etc. Even when the mobile terminal is apologized and dropped, application of an excessive load to the AF motor 10 or the like can be suppressed as much as possible.

  Furthermore, in the imaging device of the present embodiment, the mechanical shutter device is separate from the imaging lens, and the imaging lens moves in the optical axis direction, so that there is a gap between the mechanical shutter device and the imaging lens. Some spacing will occur. Accordingly, since the F-number cannot be changed with a small mechanical shutter device, the amount of light incident on the imaging lens cannot be suppressed, and the amount of light incident on the pixels of the solid-state image sensor 8 is excessive. There is a risk of becoming. Therefore, in the present invention, when the subject brightness is high, an appropriate exposure can be achieved by inserting the ND filter 30 attached to the aperture member 29 into the optical path on the image side of the aperture stop 4. .

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be changed or improved as appropriate. For example, the mechanical shutter device may be driven not by a motor but by an electromagnetic drive source such as a solenoid.

It is sectional drawing of the imaging device concerning this Embodiment. It is a top view of the mechanical shutter apparatus 20 seen from the to-be-photographed object side. It is the top view which showed the blade chamber in each operation state. It is the top view which showed the blade chamber in each operation state. It is the top view which showed the blade chamber in each operation state. It is the top view which showed the blade chamber in each operation state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens barrel 2 Dust-proof cover 4 Mirror frame 5 Positive lens 6 Negative lens 7 Low pass filter 8 Solid-state image sensor 9 Lens frame 10 AF motor 20 Mechanical shutter device 27, 28 Shutter blade 30 ND filter

Claims (4)

A solid-state image sensor;
A lens barrel,
An imaging lens including an aperture stop that is movably held in the lens barrel and is disposed closest to the object side;
A drive mechanism for driving the imaging lens in the optical axis direction with respect to the barrel;
An image pickup apparatus comprising: a mechanical shutter device fixed to the lens barrel.   The mechanical shutter device has a shutter blade that is movable between an open position that allows passage of outside light and a shielding position that blocks passage of outside light, adjacent to the aperture stop. The imaging device according to claim 1.   The imaging apparatus according to claim 1, further comprising a light transmittance adjusting unit capable of inserting and removing a changing member that changes the light transmittance in an optical path of the imaging apparatus. The imaging device according to claim 1, wherein all the lenses of the imaging lens are made of a plastic material.

Images