Imaging unit

The present invention relates to an imaging unit including an imaging device for performing photoelectric conversion. There is provided an imaging unit with which the mechanical strength of an imaging device can be ensured while allowing light to pass through the imaging device so as to improve the usability in various operations using the imaging device. An imaging unit (1) includes a substrate (11a), a light-receiving portion (11b) provided on the substrate (11a), an imaging device (10) configured to photoelectrically convert light received by the light-receiving portion (11b) into an electric signal while light is allowed to pass through the imaging device (10), and a glass substrate (19) bonded to the imaging device (10) and allowing light to pass therethrough.

TECHNICAL FIELD

The present invention relates to an imaging unit including an imaging device for performing photoelectric conversion.

BACKGROUND ART

In recent years, digital cameras have been widespread for converting an object image into an electric signal by using an imaging device such as a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal-Oxide Semiconductor) image sensor, and digitizing and recording the electric signal.

A digital single-lens reflex camera includes a phase difference detection section for detecting the phase difference of the object image, and has a phase difference detection-type AF function of performing autofocus (hereinafter also referred to simply as “AF”). With the phase difference detection-type AF function, since it is possible to detect the direction of defocus and the amount of defocus, it is possible to shorten the amount of time required for moving the focus lens and focus quickly (e.g., Patent Document 1). For guiding light from an object onto the phase difference detection section, a conventional digital single-lens reflex camera includes a movable mirror that can be moved into/out of the optical path from the lens barrel to the imaging device.

A so-called compact digital camera employs an autofocus function by video AF using an imaging device (e.g., Patent Document 2). Thus, a compact digital camera realizes a small size by eliminating the mirror for guiding light from the object to the phase difference detection section. With such a compact digital camera, it is possible to autofocus while exposing the imaging device. That is, various operations using the imaging device, e.g., obtaining an image signal from the object image formed on the imaging device to display it on the image display section provided on the back of the camera or to record it in the recording section, can be performed while performing autofocus. The autofocus function by video AF is advantageous in that the precision is typically higher than phase difference detection-type AF.

Citation List

Patent Document

PATENT DOCUMENT 1: Japanese Published Patent Application No. 2007-163545

PATENT DOCUMENT 2: Japanese Published Patent Application No. 2007-135140

SUMMARY OF THE INVENTION

Technical Problem

However, the direction of defocus cannot be detected instantaneously by video AF as in the digital camera of Patent Document 2. For example, while contrast detection-type AF detects the focus by detecting the contrast peak, the direction of contract peak, i.e., the direction of defocus, cannot be detected unless the focus lens is moved forward/backward from the current position. Therefore, the focus detection takes a long time.

That is, in order to shorten the amount of time required for the focus detection, phase difference detection-type AF is more advantageous. However, in an imaging apparatus employing phase difference detection-type AF such as the digital single-lens reflex camera of Patent Document 1, the movable mirror needs to be moved into the optical path from the lens barrel to the imaging device in order to guide light from the object onto the phase difference detection section. Therefore, various operations using the imaging device cannot be performed while performing phase difference detection-type AF. In order to switch the path of the incident light between a path toward the phase difference detection section and another path toward the imaging device, the movable mirror needs to be moved, and the movement of the movable mirror results in a time lag or noise.

That is, a conventional imaging apparatus performing phase difference detection-type AF has poor usability in terms of various operations using the imaging device.

The present invention has been made in view of this, and has an object to improve the usability in various operations using the imaging device and the phase difference detection using the phase difference detection section.

Solution to the Problem

The present applicant has made in-depth researches in an attempt to solve the above problems, arriving at using light that has passed through the imaging device. That is, by performing phase difference detection-type focus detection using light that has passed through the imaging device, it is possible to eliminate the movable mirror, and it is also possible to perform an operation by the imaging device and the phase difference detection at the same time. Moreover, by allowing light to pass through the imaging device, it is possible to improve the usability not only in performing the phase difference detection but also in performing various operations.

However, in order to allow light to pass through the imaging device, the imaging device needs to be thin, which lowers the mechanical strength of the imaging device. Thus, an object of the present invention is to provide an imaging unit which allows light to pass through an imaging device while ensuring the mechanical strength of the imaging device.

Therefore, in the present invention, an optically transparent substrate is bonded to a substrate of an imaging device so as to reinforce the imaging device. Specifically, an imaging unit of the present invention includes: an imaging device including a semiconductor substrate and a light-receiving portion provided on the semiconductor substrate for photoelectrically converting light received by the light-receiving portion into an electric signal while light is allowed to pass through the imaging device; and an optically transparent substrate bonded to the imaging device, the optically transparent substrate allowing light to pass therethrough.

Advantages of the Invention

According to the present invention, an optically transparent substrate is bonded to an imaging device, whereby the imaging device can be reinforced even if the imaging device is made so thin that light is allowed to pass therethrough. Since the reinforcing substrate is provided as an optically transparent substrate, and therefore the optically transparent substrate can also allow light to pass therethrough, the optically transparent substrate does not hinder light from being incident upon the imaging device or exiting the imaging device.

DESCRIPTION OF EMBODIMENTS

A camera including an imaging unit1according to Embodiment 1 of the present invention will be described.

As shown inFIG. 2, a camera100of Embodiment 1 is an interchangeable lens-type single-lens reflex digital camera formed primarily by a camera body4responsible for main functions of the camera system, and an interchangeable lens7detatchably attached to the camera body4. The interchangeable lens7is attached to a body mount41provided on the front surface of the camera body4. The body mount41is provided with an electric segment41a.

—Configuration of Camera Body—

The camera body4includes the imaging unit1for obtaining an object image as a shooting image, a shutter unit42for adjusting the exposure of the imaging unit1, an IR-cut/OLPF (Optical Low Pass Filter)43for removing infrared light and reducing the moire phenomenon of the object image incident upon the imaging unit1, an image display section44, which is an LCD monitor, for displaying a shooting image, a live-view image and various information, and a body control section5. The camera body4forms an imaging apparatus main body.

The camera body4includes a power switch40afor turning ON/OFF the power of the camera system, and a release button40boperated by the photographer when adjusting the focus and when releasing the shutter.

When the power is turned ON by the power switch40a,the power is supplied to various sections of the camera body4and the interchangeable lens7.

The release button40bis a two-stage switch, which can be pressed halfway down for autofocus to be described later, AE, etc., and can be pressed all the way down for releasing the shutter.

The imaging unit1converts an object image into an electric signal by photoelectric conversion, the details of which will be described later. The imaging unit1can be moved by a blur correcting unit45in a plane that is orthogonal to the optical axis X.

The body control section5includes a body microcomputer50, a non-volatile memory50a,a shutter control section51for controlling the operation of the shutter unit42, an imaging unit control section52for controlling the operation of the imaging unit1and A/D-converting an electric signal from the imaging unit1to output the converted signal to the body microcomputer50, an image reading/recording section53for reading out image data from an image storing section58, e.g., a card-type recording medium or an internal memory, and recording the image data to the image storing section58, an image recording control section54for controlling the image reading/recording section53, an image display control section55for controlling the display of the image display section44, a blur detection section56for detecting the amount of image blur caused by the shaking of the camera body4, and a correction unit control section57for controlling the blur correcting unit45. The body control section5forms a control section.

The body microcomputer50is a control device responsible for a central control of the camera body4, and controls various sequences. The body microcomputer50includes a CPU, a ROM and a RAM, for example. The body microcomputer50can realize various functions as the CPU reads programs stored in the ROM.

The body microcomputer50receives input signals from the power switch40aand the release button40b,and outputs control signals to the shutter control section51, the imaging unit control section52, the image reading/recording section53, the image recording control section54, the correction unit control section57, etc., instructing the shutter control section51, the imaging unit control section52, the image reading/recording section53, the image recording control section54, the correction unit control section57, etc., to perform their controls. The body microcomputer50performs microcomputer-to-microcomputer communications with a lens microcomputer80to be described later.

For example, in response to an instruction from the body microcomputer50, the imaging unit control section52A/D-converts an electric signal from the imaging unit1and outputs the converted signal to the body microcomputer50. The body microcomputer50performs a predetermined image process on the received electric signal to thereby produce an image signal. Then, the body microcomputer50transmits an image signal to the image reading/recording section53, and instructs the image recording control section54to record and display the image so that the image recording control section54saves the image signal in the image storing section58and transmits the image signal to the image display control section55. The image display control section55controls the image display section44based on the transmitted image signal so as to display the image on the image display section44.

The non-volatile memory50astores various information regarding the camera body4(unit information). The unit information includes, for example, information regarding the model for identifying the camera body4(unit identification information) such as the name of the manufacturer, the date of manufacture, the model number of the camera body4, and information regarding the version of the software installed on the body microcomputer50and firmware updates, information regarding whether the camera body4is provided with means for correcting an image blur such as the blur correcting unit45and the blur detection section56, information regarding the detection capability such as the model number of the blur detection section56and the sensitivity thereof, the error history, etc. Note that these information may be stored in a memory section in the body microcomputer50instead of in the non-volatile memory50a.

The blur detection section56includes an angular velocity sensor for detecting the movement of the camera body4caused by the camera shake, etc. The angular velocity sensor outputs a positive or negative angular velocity signal depending on the direction in which the camera body4moves, based on the output resulting when the camera body4stays still. Note that in the present embodiment, two angular velocity sensors are provided for the detection in two directions, i.e., the yawing direction and the pitching direction. The output angular velocity signal undergoes a filtering operation, an amplification operation, etc., and is converted by an A/D conversion section into a digital signal, which is given to the body microcomputer50.

The interchangeable lens7forms an imaging optical system for forming an object image on the imaging unit1in the camera body4, and primarily includes a focus adjustment section7A for adjusting the focus, an aperture adjustment section7B for adjusting the aperture, a lens image blur correction section7C for correcting the image blur by adjusting the optical path, and a lens control section8for controlling the operation of the interchangeable lens7.

The interchangeable lens7is attached to the body mount41of the camera body4with a lens mount71therebetween. The lens mount71includes an electric segment71a to be electrically connected with the electric segment41aof the body mount41when the interchangeable lens7is attached to the camera body4.

The focus adjustment section7A is formed by a focus lens group72for adjusting the focus. The focus lens group72can be moved in the optical axis X over a section from the closest focus position to the infinite focus position, which are determined as standard specifications of the interchangeable lens7. In the case of a contrast detection-type focus position detection to be described later, it is necessary that the focus lens group72can be moved forward and backward in the optical axis X from the focus position, and therefore there is a lens shift margin section in which the focus lens group72can be moved forward and backward in the optical axis X beyond the above-described section from the closest focus position to the infinite focus position. Note that the focus lens group72does not always need to include a plurality of lenses, and may include a single lens.

The aperture adjustment section7B is formed by a stop portion73for adjusting the aperture to be stopped down or opened up. The stop portion73forms a light amount adjustment section.

The lens image blur correction section7C includes a blur correcting lens74, and a blur correction lens driving section74a for moving the blur correcting lens74in a plane that is orthogonal to the optical axis X.

The lens control section8includes the lens microcomputer80, a non-volatile memory80a,a focus lens group control section81for controlling the operation of the focus lens group72, a focus driving section82for receiving a control signal from the focus lens group control section81to drive the focus lens group72, a stop control section83for controlling the operation of the stop portion73, a blur detection section84for detecting the blur of the interchangeable lens7, and a blur correction lens unit control section85for controlling the blur correction lens driving section74a.

The lens microcomputer80is a control device responsible for a central control of the interchangeable lens7, and is connected to various sections provided in the interchangeable lens7. Specifically, the lens microcomputer80includes a CPU, a ROM and a RAM, and can realize various functions as the CPU reads programs stored in the ROM. For example, the lens microcomputer80has a function of setting the lens image blur correcting devices (the blur correction lens driving section74a,etc.) to a correction-enabled state or a correction-disabled state based on the signal from the body microcomputer50. The body microcomputer50and the lens microcomputer80are electrically connected together via the contact between the electric segment71aprovided on the lens mount71and the electric segment41aprovided on the body mount41so that information can be exchanged therebetween.

The non-volatile memory80astores various information (lens information) regarding the interchangeable lens7. The lens information includes, for example, information regarding the model for identifying the interchangeable lens7(lens identification information) such as the name of the manufacturer, the date of manufacture, the model number of the interchangeable lens7, and information regarding the version of the software installed on the lens microcomputer80and firmware updates, information regarding whether the interchangeable lens7is provided with means for correcting an image blur such as the blur correction lens driving section74aand the blur detection section84. If the interchangeable lens7is provided with means for correcting the image blur, the lens information includes information regarding the detection capability such as the model number of the blur detection section84and the sensitivity thereof, information regarding the correction capability such as the model number of the blur correction lens driving section74aand the maximum correctable angle (lens-side correction capability information), the version of the software for performing the image blur correction, etc. Moreover, the lens information also includes information regarding the power consumption required for driving the blur correction lens driving section74a(lens-side power consumption information), and information regarding the driving scheme of the blur correction lens driving section74a(lens-side driving scheme information). Note that the non-volatile memory80acan store information transmitted from the body microcomputer50. Note that these information may be stored in the memory section in the lens microcomputer80instead of in the non-volatile memory80a.

The focus lens group control section81includes an absolute position detection section81afor detecting the absolute position of the focus lens group72in the optical axis direction, and a relative position detection section81bfor detecting the relative position of the focus lens group72in the optical axis direction. The absolute position detection section81adetects the absolute position of the focus lens group72in the casing of the interchangeable lens7. For example, the absolute position detection section81ais formed by a several-bit contact-type encoder substrate and a brush, and is configured so that the absolute position can be detected. Although the relative position detection section81bcannot, by itself, detect the absolute position of the focus lens group72, it can detect the direction of movement of the focus lens group72, and it uses a two-phase encoder, for example. As two-phase encoders, two of those that alternately output binary signals with an equal pitch, such as rotary pulse encoders, MR elements and Hall devices, depending on the position in the optical axis direction of the focus lens group72are provided so that the phases of the pitches thereof are shifted from each other. The lens microcomputer80calculates the relative position of the focus lens group72in the optical axis direction based on the output from the relative position detection section81b.

The blur detection section84includes an angular velocity sensor for detecting the movement of the interchangeable lens7caused by camera shake, etc. The angular velocity sensor outputs a positive or negative angular velocity signal depending on the direction in which the interchangeable lens7moves, based on the output resulting when the interchangeable lens7stays still. Note that in the present embodiment, two angular velocity sensors are provided for the detection in two directions, i.e., the yawing direction and the pitching direction. The output angular velocity signal undergoes a filtering operation, an amplification operation, etc., and is converted by an A/D conversion section into a digital signal, which is given to the lens microcomputer80.

The blur correction lens unit control section85includes a movement amount detection section (not shown). The movement amount detection section is a detection section for detecting the actual amount of movement of the blur correcting lens74. The blur correction lens unit control section85feedback-controls the blur correcting lens74based on the output from the movement amount detection section.

Note that while the camera body4and the interchangeable lens7are both provided with the blur detection sections56and84and the blur correcting devices45and74a,either the camera body4or the interchangeable lens7may be provided with a blur detection section and a blur correcting device, and neither of them may be provided with a blur detection section and a blur correcting device (in such a case, the above-described blur correction-related sequence can be omitted).

As shown inFIG. 3, the imaging unit1includes an imaging device10for converting an object image into an electric signal, a glass substrate19bonded to the imaging device10, a package31for holding the imaging device10, and a phase difference detection unit20for performing phase difference detection-type focus detection.

The imaging device10is a back side-illuminated interline CCD image sensor, and includes a photoelectric conversion section11formed by a semiconductor material, vertical registers12, transfer paths13, masks14, and color filters15, as shown inFIG. 1.

The photoelectric conversion section11includes a substrate11a,and a plurality of light-receiving portions (also referred to as “pixels”)11b,11b,. . . , arranged on the substrate11a.

The substrate11ais an Si (silicon)-based semiconductor substrate. Specifically, the substrate11ais formed by an Si single crystal substrate or an SOI (Silicon On Insulator wafer). Particularly, an SOI substrate has a sandwich structure of an Si thin film and an SiO2thin film, and the reaction can be stopped at the SiO2layer in an etching process, or the like, which is advantageous for stable substrate processing.

The light-receiving portion11bis formed by a photodiode, and absorbs light and generates electrical charge. The light-receiving portions11b,11b,. . . , are each provided in one of minute square pixel regions arranged in a matrix pattern on the surface of the substrate11a(the lower surface inFIG. 1) (seeFIG. 4).

As described above, the imaging device10is a back side-illuminated device, in which light from the object is incident upon a surface (hereinafter referred to also as the “back surface”) of the substrate11athat is opposite to another surface (hereinafter referred to also as “front surface”) on which the light-receiving portions11b,11b,. . . , are provided.

The vertical register12is provided on the front surface of the substrate11afor each light-receiving portion11b,and serves to temporarily store the electrical charge stored in the light-receiving portion11b.That is, the electrical charge stored in the light-receiving portion11bis transferred to the vertical register12. The electrical charge transferred to the vertical register12is transferred to a horizontal register (not shown) via the transfer path13, and is sent to an amplifier (not shown). The electrical charge sent to the amplifier is amplified and taken out as an electric signal.

The mask14includes an incident-side mask14aprovided on the front surface of the substrate11a,and an exit-side mask14bprovided so as to cover the light-receiving portion11b,the vertical register12and the transfer path13from the opposite side to the substrate11a.The incident-side mask14ais provided between the light-receiving portions11band11bon the front surface of the substrate11a.The vertical register12and the transfer path13are provided so as to overlap the incident-side mask14a.Thus, the incident-side mask14aprevents light having passed through the substrate11afrom being incident upon the vertical register12and the transfer path13. The exit-side mask14breflects light, which has passed through the light-receiving portions11b,11b,. . . , without being absorbed by the light-receiving portions11b,11b,. . . , so that the light is again incident upon the light-receiving portions11b,11b,. . . . The exit-side mask14bincludes a plurality of through holes14c(only one shown inFIG. 1) for allowing light which has passed through the light-receiving portion11bto exit to the back surface side of the imaging device10(the opposite side to the glass substrate19in the present embodiment). Note that the exit-side mask14bmay be omitted.

A protection layer18formed by an optically transparent resin is provided on the front surface of the substrate11aso as to cover the light-receiving portion11b,the vertical register12, the transfer path13and the mask14.

The color filter15is provided on the back surface side of the substrate11afor each of minute square pixel regions corresponding to the light-receiving portion11b.The color filter15allows only a particular color to pass therethrough, and is a thin-film interference filter formed by a dielectric. The present embodiment employs a so-called Bayer-type primary color filter as shown inFIG. 4. That is, the imaging device10includes repeated units, each including four adjacent color filters15,15, . . . , (or four pixel regions) arranged in a 2-by-2 array, wherein each repeated unit includes two green color filters (i.e., color filters having a higher transmittance for a visible wavelength range for green than for visible wavelength ranges for other colors)15garranged at one of two pairs of opposing corners, with a red color filter (i.e., a color filter having a higher transmittance for a visible wavelength range for red than for visible wavelength ranges for other colors)15rand a blue color filter (i.e., a color filter having a higher transmittance for a visible wavelength range for blue than for visible wavelength ranges for other colors)15barranged at the other pair of opposing corners. As a whole, the green color filters15g,15g,. . . , are arranged at every other positions in the vertical direction and in the horizontal direction. Note that the color filters15may be complementary color-type filters each allowing one of colors CyMYG to pass therethrough. The color filter15is vapor-deposited on the junction surface of the glass substrate19on which the imaging device10is bonded.

The glass substrate19is formed by a borosilicate glass substrate. The glass substrate19corresponds to an optically transparent substrate. The glass substrate19is anodically-bonded to the substrate11a.Here, since borosilicate glass contains a lot of mobile ions, if the glass substrate19is formed by borosilicate glass, it can be anodically-bonded to the substrate11a.While the color filter15is vapor-deposited on the surface of the glass substrate19that is bonded to the substrate11aas described above, the glass substrate19can be anodically-bonded to the substrate11asince the color filter15is a dielectric.

Note that the material of the glass substrate19may be, for example, Pyrex (registered trademark) from Corning Incorporated or Tempax/Duran from Schott AG. The bond between the glass substrate19and the substrate1la is not limited to an anodic bond, but may be a bond with an adhesive, etc.

Here, the substrate11aanodically-bonded to the glass substrate19may be obtained by anodic-bonding the substrate11awhich has been polished to a desired thickness (e.g., 1-5 μm) to the glass substrate19, or by anodic-bonding the substrate11awhich is thicker than the desired thickness and then polishing the substrate11ato the desired thickness by etching, etc. In a case where the substrate11awhich is thicker than the desired thickness is used, the anodically-bonded substrate11ais subjected to a heat treatment so that an SiO2layer is formed on the surface of the substrate11athat is opposite to the glass substrate19. Then, by dissolving only the SiO2layer with hydrofluoric acid, a thin (e.g., 1-2 μm) Si layer is formed, and the light-receiving portion11b,the vertical register12, the transfer path13, etc., are formed on the Si layer by a semiconductor process.

Light is incident upon the imaging device10having such a configuration from the side of the glass substrate19. Specifically, light which has passed through the glass substrate19is incident upon each color filter15r,15g,15b,and only light of the color corresponding to the color filter15passes through the color filter15to be incident upon the back surface of the substrate11a.Since the substrate11ais very thin (i.e., since it is formed to such a thickness that light passes through the substrate11a), light incident upon the substrate11apasses through the substrate11ato reach the light-receiving portions11b,11b,. . . , arranged on the front surface of the substrate11a.Here, since the incident-side masks14aare provided in areas of the front surface of the substrate11awhere the light-receiving portions11b,11b,. . . , are absent, no light is incident upon the vertical register12or the transfer path13. Since the light-receiving portions11b,11b,. . . , are each opened across the entire surface thereof toward the side from which light is incident (the side of the substrate11a), unlike an imaging device410of Embodiment 2 to be described later, the quantum yield is very high. Each light-receiving portion11babsorbs light to generate electrical charge. Here, since the exit-side mask14bis provided on one side of the light-receiving portion11bthat is opposite to the substrate11a,light that has passed through the light-receiving portion11bwithout being absorbed by the light-receiving portion11bis reflected by the exit-side mask14b,and the light is again incident upon the light-receiving portion11b.This further improves the quantum yield. The electrical charge generated by each light-receiving portion11bis sent to the amplifier via the vertical register12and the transfer path13, and is output as an electric signal. Since light of a particular color which has passed through one of the color filters15r,15gand15bis incident upon each of the light-receiving portions11b,11b,. . . , the amount of received light of the color corresponding to the color filter15is obtained as an output from the light-receiving portion11b.

Thus, the imaging device10performs photoelectric conversion by the light-receiving portions11b,11b,. . . , across the entire imaging surface, thereby converting an object image formed on the imaging surface into an electric signal.

The imaging device10having such a configuration is held by the package31(seeFIG. 3). The package31forms a holding section.

Specifically, the package31includes a flat plate-shaped bottom plate31a,a circuit substrate32provided thereon, and side walls31b,31b,. . . , along the four sides thereof. The imaging device10is mounted on the circuit substrate32while being surrounded from four sides by the side wall31b,31b, . . . .

Specifically, in the peripheral portion of the substrate11aof the imaging device10, the light-receiving portion11b,the vertical register12, the transfer path13, the mask14, the protection layer18, etc., are absent, with an interconnect which enables electrical connection with the transfer path13, the vertical register12, etc., exposed thereon, as shown inFIG. 5.

On the other hand, the circuit substrate32includes a substrate base32a,and a circuit pattern32bprovided on the front surface (the surface closer to the object) of the substrate base32aand located so as to face the interconnect of the substrate11aof the imaging device10. Then, the peripheral portion of the substrate11aof the imaging device10is laid over the circuit substrate32from the object side, and they are bonded together through thermal fusion, thereby electrically connecting the interconnect of the substrate11aof the imaging device10with the circuit pattern32b.

A cover glass33is attached at the tip of the side walls31b,31b,. . . , of the package31so as to cover the imaging surface (back surface) of the imaging device10. The cover glass33protects the imaging surface of the imaging device10from dust, etc.

An equal number of (three in the present embodiment) openings31c,31c,. . . , to the number of the through holes14c,14c,. . . , of the exit-side mask14bof the imaging device10are formed running through the bottom plate31aof the package31at positions corresponding to the through holes14c,14c,. . . . With the openings31c,31c,. . . , light which has passed through the imaging device10reaches the phase difference detection unit20to be described later.

Note that it is not always necessary that the openings31care formed running through the bottom plate31aof the package31. That is, transparent portions or semi-transparent portions may be formed, for example, in the bottom plate31a,as long as light which has passed through the imaging device10reaches the phase difference detection unit20.

The phase difference detection unit20is provided on the back surface side (the side opposite to the object) of the imaging device10for receiving transmitted light from the imaging device10to perform phase difference detection-type focus detection. Specifically, the phase difference detection unit20converts the received transmitted light into an electric signal for range finding. The phase difference detection unit20forms a phase difference detection section.

As shown inFIGS. 3 and 6, the phase difference detection unit20includes a condenser lens unit21, a mask member22, a separator lens unit23, a line sensor unit24, and a module frame25for the attachment of the condenser lens unit21, the mask member22, the separator lens unit23and the line sensor unit24. The condenser lens unit21, the mask member22, the separator lens unit23and the line sensor unit24are arranged in this order from the side of the imaging device10in the thickness direction of the imaging device10.

The condenser lens unit21is obtained by making a plurality of condenser lenses21a,21a,. . . , into a single unit. There are an equal number of condenser lenses21a,21a,. . . , to the number of the through holes14c,14c,. . . , of the exit-side mask14b.Each condenser lens21a,a lens for condensing the incident light, condenses light that has passed through the imaging device10and started to diverge so as to guide the light onto a separator lens23a,to be described later, of the separator lens unit23. Each condenser lens21ahas a convex-shaped incident surface21band is shaped in a cylindrical shape around the incident surface21b.

With the provision of the condenser lens21a,the light incident upon the separator lens23ais raised (the angle of incidence is decreased), and it is therefore possible to reduce the aberration of the separator lens23aand to decrease the object image interval on a line sensor24ato be described later. As a result, it is possible to reduce the sizes of the separator lens23aand the line sensor24a.If the focus position of the object image from the imaging optical system greatly diverges from the imaging unit1(specifically, if it greatly diverges from the imaging device10of the imaging unit1), the contrast of the image decreases significantly. In the present embodiment, the decrease in contrast is reduced because of the size-reduction effect by the condenser lens21aand the separator lens23a,and to increase the focus detection range. Note that the condenser lens unit21may be absent in cases where a high-precision phase difference detection near the focus position is realized, the sizes of the separator lens23a,the line sensor24a,etc., have some margin, for example.

The mask member22is arranged between the condenser lens unit21and the separator lens unit23. The mask member22includes two mask openings22aand22aat each position corresponding to the separator lens23a.That is, the mask member22divides the lens surface of the separator lens23ainto two areas, thus allowing only the two areas to be exposed to the side of the condenser lens21a.That is, the mask member22performs pupil-division to split light which has been condensed by the condenser lens21ainto two beams, which are incident upon the separator lens23a.With the mask member22, it is possible to prevent detrimental light from one separator lens23afrom being incident upon another, adjacent separator lens23a.Note that the mask member22is optional.

The separator lens unit23includes a plurality of separator lenses23a,23a,. . . , made into a single unit. As with the condenser lenses21a,21a,. . . , there are an equal number of separator lenses23a,23a,. . . , to the number of the through holes14c,14c,. . . , of the exit-side mask14b.With each separator lens23a,two beams which have passed through the mask member22to be incident upon the separator lens23aare formed as two identical object images on the line sensor24a.

The line sensor unit24includes a plurality of line sensors24a,24a,. . . , and a base portion24bon which the line sensors24a,24a,. . . , are placed. As with the condenser lenses21a,21a,. . . , there are an equal number of line sensors24a,24a,. . . , to the number of the through holes14c,14c,. . . , of the exit-side mask14b.Each line sensor24areceives an image formed on the imaging surface and converts the received image into an electric signal. That is, it is possible to detect the interval between two object images based on the output from the line sensor24a,and it is possible, based on the interval, to obtain the amount of shift of the focal point (i.e., the amount of defocus (Df amount)) of the object image formed on the imaging device10and to obtain the direction toward which the focal point is off (i.e., the direction of defocus) (hereinafter the Df amount, the direction of defocus, etc., will also be referred to as “defocus information”).

The condenser lens unit21, the mask member22, the separator lens unit23and the line sensor unit24having such a configuration are arranged in the module frame25.

The module frame25is a member formed in a frame shape, with an attachment portion25aprovided on the inner circumference thereof and protruding inwardly. A first attachment portion25band a second attachment portion25care formed in a terraced shape on one side of the attachment portion25athat is closer to the imaging device10. A third attachment portion25dis formed on the side of the attachment portion25athat is opposite to the imaging device10.

The mask member22is attached to the second attachment portion25cof the module frame25, and the condenser lens unit21is attached to the first attachment portion25bfrom the side of the imaging device10. The condenser lens unit21and the mask member22are formed so that when they are attached to the first attachment portion25band the second attachment portion25c,respectively, the peripheral portions thereof are fitted into the module frame25, as shown inFIGS. 3 and 6, thereby being positioned with respect to the module frame25.

On the other hand, from the opposite side to the imaging device10, the separator lens unit23is attached to the third attachment portion25dof the module frame25. A positioning pin25eand a direction reference pin25f,protruding to the opposite side to the condenser lens unit21, are provided on the third attachment portion25d.On the other hand, a positioning hole23band a direction reference hole23c,corresponding to the positioning pin25eand the direction reference pin25f,respectively, are formed on the separator lens unit23. The positioning pin25eand the positioning hole23bhave their diameters determined so that they fit together. On the other hand, the direction reference pin25fand the direction reference hole23chave their diameters determined so that they loosely fit together. That is, the orientation, such as the direction, of the separator lens unit23for the attachment to the third attachment portion25dis defined by inserting the positioning hole23band the direction reference hole23cinto the positioning pin25eand the direction reference pin25f,respectively, of the third attachment portion25d,and the separator lens unit23is positioned with respect to the third attachment portion25dby fitting together the positioning hole23band the positioning pin25e.When the separator lens unit23is attached with its orientation and position fixed, the lens surfaces of the separator lenses23a,23a,. . . , face toward the condenser lens unit21while opposing the mask openings22aand22a.

The condenser lens unit21, the mask member22and the separator lens unit23are attached to the module frame25while being positioned with respect to the module frame25. That is, the condenser lens unit21, the mask member22and the separator lens unit23are positioned with respect to one another by the module frame25.

Then, the line sensor unit24is attached to the module frame25from the back surface side (the opposite side to the condenser lens unit21) of the separator lens unit23. The line sensor unit24is attached to the module frame25in a state where it is positioned so that light which has passed through each separator lens23ais incident upon one line sensor24a.

Therefore, when the condenser lens unit21, the mask member22, the separator lens unit23and the line sensor unit24are attached to the module frame25, the condenser lenses21a,21a,. . . , the mask member22, the separator lenses23a,23a,. . . , and the line sensors24a,24a,. . . , are positioned so that light incident upon the condenser lenses21a,21a,. . . , passes through the condenser lenses21a,21a,. . . , to be incident upon the separator lenses23a,23a,. . . , through the mask member22, and light which has passed through the separator lenses23a,23a,. . . , forms an image on the line sensors24a,24a, . . . .

The imaging device10and the phase difference detection unit20having such a configuration are bonded to each other. Specifically, the imaging device10and the phase difference detection unit20are configured such that the opening31cof the package31of the imaging device10and the condenser lens21aof the phase difference detection unit20fit together. That is, the module frame25is bonded to the package31with the condenser lenses21a,21a,. . . , of the phase difference detection unit20fitted into the openings31c,31c,. . . , of the package31of the imaging device10. Thus, the imaging device10and the phase difference detection unit20can be adhesively bonded together while being positioned with respect to each other. Thus, the condenser lenses21a,21a,. . . , the separator lenses23a,23a,. . . , and the line sensors24a,24a,. . . , are made into a single unit, and are attached to the package31as a unit.

Here, the configuration may be such that all the openings31c,31c,. . . , and all the condenser lenses21a,21a,. . . , are fitted together. Alternatively, the configuration may be such that only some of the openings31c,31c,. . . , are fitted together with the corresponding condenser lenses21a,21a,. . . , with the remaining openings31c,31c,. . . , loosely fitted together with the corresponding condenser lenses21a,21a,. . . . In the latter case, it is preferred that the condenser lens21aand the opening31cwhich are closest to the center of the imaging surface are fitted together for realizing the positioning in the imaging surface, and the condenser lens21aand the opening31cwhich are farthest away from the center of the imaging surface are fitted together for realizing the positioning around the condenser lens21aand the opening31cat the center of the imaging surface (i.e., positioning of the rotation angle).

As a result of bonding together the imaging device10and the phase difference detection unit20as described above, the condenser lens21a,a pair of mask openings22aand22aof the mask member22, the separator lens23aand the line sensor24aare arranged for each through hole14cof the exit-side mask14bon the back surface side of the imaging device10.

Thus, light which has passed through the imaging device10can easily reach the back surface side of the package31by providing the openings31c,31c,. . . , in the bottom plate31aof the package31accommodating the imaging device10which is configured so as to allow light to pass therethrough, and it is possible to easily realize a configuration where light which has passed through the imaging device10is received by the phase difference detection unit20by arranging the phase difference detection unit20on the back surface side of the package31.

Although the openings31c,31c,. . . , formed in the bottom plate31aof the package31may employ any configuration as long as light which has passed through the imaging device10is passed to the back surface side of the package31, light which has passed through the imaging device10can reach, without being attenuated, the back surface side of the package31by forming the openings31c,31c,. . . , which are through holes.

By fitting the condenser lenses21a,21a,. . . , into the openings31c,31c,. . . , it is possible to position the phase difference detection unit20with respect to the imaging device10by using the openings31c,31c,. . . . Note that in a case where the condenser lenses21a,21a,. . . , are not provided, the phase difference detection unit20can similarly be positioned with respect to the imaging device10by employing a configuration such that the separator lenses23a,23a,. . . , are fitted into the openings31c,31c, . . . .

Moreover, since the condenser lenses21a,21a,. . . , can be arranged close to the substrate11awhile penetrating the bottom plate31aof the package31, the imaging unit1can be made compact.

Three through holes14care formed in the exit-side mask14bof the imaging device10, with three sets of the condenser lens21a,the separator lens23aand the line sensor24aprovided corresponding to the through holes14c,14cand14c,but the present invention is not limited to this. These numbers are not limited to three, but may be set to any other number. For example, there may be nine through holes14c,14c,. . . , and nine sets of the condenser lens21a,the separator lens23aand the line sensor24a,as shown inFIG. 7.

An operation of the imaging unit1having such a configuration will now be described.

When light from the object is incident upon the imaging unit1, the light passes through the cover glass33to be incident upon the glass substrate19. The light passes through the glass substrate19to be incident upon the back surface of the substrate11aof the imaging device10. At this point, each portion of the light passes through one of the color filters15r,15gand15bso that only light of the color corresponding to the color filter15is incident upon the substrate11a.The light incident upon the substrate11apasses through the substrate11ato reach the light-receiving portions11b,11b,. . . , on the front surface of the substrate11a.Since the incident-side mask14ais provided on the front surface of the substrate11a,no light is incident upon the vertical register12or the transfer path13, and light is incident only upon the light-receiving portions11b,11b,. . . . Each light-receiving portion11babsorbs light to generate electrical charge. Here, not all of the light incident upon the light-receiving portion11bis absorbed by the light-receiving portion11b,but a portion thereof passes through the light-receiving portion11b.However, since the exit-side mask14bis provided at a position reached by light passing through the light-receiving portion11b,light which has passed through the light-receiving portion11bis reflected by the exit-side mask14b,and the light is again incident upon the light-receiving portion11b.The electrical charge generated by each light-receiving portion11bis sent to the amplifier via the vertical register12and the transfer path13, and is output as an electric signal. Thus, the light-receiving portions11bconvert light into an electric signal across the entire imaging surface of the imaging device10, and thus the imaging device10converts an object image formed on the imaging surface into an electric signal for producing an image signal.

Note however that in the through holes14c,14c,. . . , of the exit-side mask14b,light which has passed through the light-receiving portions11b,11b,. . . , of the imaging device10exits to the back surface side of the imaging device10. Then, light which has passed through the imaging device10is incident upon the condenser lenses21a,21a,. . . , which are fitted into the openings31c,31c,. . . , of the package31. Light which has been condensed together by passing through the condenser lenses21ais divided into two light beams while passing through each pair of mask openings22aand22aformed in the mask member22, and the divided light beams are incident upon the separator lens23a.The light, which has been split in pupil-division, passes through the separator lens23ato form an identical object image at two locations on the line sensor24a.The line sensor24aproduces and outputs an electric signal from the object image through photoelectric conversion.

Then, how electric signals obtained by conversion by the imaging device10are processed in the body microcomputer50will be described.

The electric signal output from the imaging device10is input to the body microcomputer50via the imaging unit control section52. Then, the body microcomputer50obtains the position information of each light-receiving portion11band output data corresponding to the amount of light received by the light-receiving portion11bfrom the entire imaging surface of the imaging device10, thereby obtaining the object image formed on the imaging surface as an electric signal.

Here, in the light-receiving portions11b,11b,. . . , even when the same amount of light is received, the amounts of accumulated electrical charge differ among different wavelengths of light. Therefore, the outputs from the light-receiving portions11b,11b,. . . , of the imaging device10are each corrected according to the kind of the color filter15r,15g,15bprovided therefor. For example, the amount of correction is determined for each pixel so that when the R pixel11bprovided with the red color filter15r,the G pixel11bprovided with the green color filter15g,and the B pixel11bprovided with the blue color filter15breceive the same amount of different colors of light corresponding to the color of each color filter, the output from the R pixel11b,the output from the G pixel11band the output from the B pixel11bare at the same level.

In addition, in the present embodiment, with the provision of the through holes14c,14c,. . . , of the exit-side mask14b,the amount of received light is smaller in areas of the imaging device10corresponding to the through holes14c,14c,. . . , as compared with that in other areas thereof As a result, portions of the image corresponding to the through holes14c,14c,. . . , may not be captured appropriately (e.g., a shooting image might be dark), if output data from the pixels11b,11b,. . . , provided in areas corresponding to the through holes14c,14c,. . . , are subjected to the same image processing as that for output data from the pixels11b,11b,. . . , provided in other areas. Therefore, outputs from the pixels11bin the through holes14c,14c,. . . , are corrected so as to eliminate the influence of the through holes14c,14c,. . . , (e.g., by amplifying the outputs from the pixels11bin the through holes14c,14c,. . . ).

The decrease in output also differs depending on the wavelength of the light. Specifically, as the wavelength is longer, the transmittance of the substrate11ais higher, and the decrease in output due to the through hole14cis greater. Therefore, the decrease in output due to the through hole14cdiffers depending on the kind of the color filter15r,15g,15b.In view of this, the amount of correction to be made for each pixel11bcorresponding to a through hole14cfor eliminating the influence of the through hole14cis varied depending on the wavelength of light received by the pixel11b.Specifically, for each pixel11bcorresponding to a through hole14c,the amount of correction is set larger as the wavelength of light received by the pixel11bis longer.

Here, the amount of correction for eliminating the difference in the amount of stored electrical charge depending on the color of light received is determined for each pixel11bas described above, and the correction for eliminating the influence of the through hole14cis performed in addition to this correction for eliminating the difference in the amount of stored electrical charge depending on the color. That is, the amount of correction for eliminating the influence of the through hole14cis equal to the difference between the amount of correction for a pixel11bcorresponding to a through hole14cand the amount of correction for another pixel11bnot corresponding to a through hole14cbut receiving light of the same color as the pixel11b.In the present embodiment, the amount of correction is varied from color to color based on the relationship shown below. This realizes a stable image output.
Rk>Gk>Bk   (1)

where

Rk: correction amount for R pixel corresponding to through hole14c—correction amount for R pixel not corresponding to through hole14c

Gk: correction amount for G pixel corresponding to through hole14c—correction amount for G pixel not corresponding to through hole14c

Bk: correction amount for B pixel corresponding to through hole14c—correction amount for B pixel not corresponding to through hole14c

That is, since red, having the longest wavelength of the three colors (red, green and blue), has the highest transmittance, the difference in the amount of correction is largest for a red pixel. Since blue, having the shortest wavelength of the three colors, has the lowest transmittance, the difference in the amount of correction is smallest for a blue pixel.

That is, the amount of correction for the output of each pixel11bof the imaging device10is determined based on whether the pixel11bis located at a position corresponding to a through hole14cand on the color of the color filter15corresponding to the pixel11b.The amounts of correction are determined, for example, so that the white balance and/or brightness of the image displayed based on the output from a pixel11bcorresponding to a through hole14care equal to those of the image displayed based on the output from another pixel11bnot corresponding to a through hole14c.

After correcting the output data from the light-receiving portions11b,11b,. . . , as described above, the body microcomputer50produces an image signal containing the position information, the color information and the brightness information for each light-receiving portion, i.e., each pixel11b,based on the output data. Thus, there is obtained an image signal of the object image formed on the imaging surface of the imaging device10.

By correcting the outputs from the imaging device10as described above, the object image can be captured appropriately even with the imaging device10provided with the through holes14c,14c, . . . .

On the other hand, the electric signal output from the line sensor unit24is also input to the body microcomputer50. Then, the body microcomputer50obtains the interval between two object images formed on the line sensor24abased on the output from the line sensor unit24, and can detect the focus state of the object image formed on the imaging device10based on the obtained interval. For example, two object images formed on the line sensor24aare positioned at predetermined reference positions with a predetermined reference interval therebetween when the object images are correctly formed (focused) on the imaging device10through the imaging lens. In contrast, when the object image is formed before the imaging device10in the optical axis direction (front focus), the interval between the two object images is smaller than the reference interval realized when the object is focused. On the other hand, when the object image is formed behind the imaging device10in the optical axis direction (back focus), the interval between the two object images is larger than the reference interval realized when the object is focused. That is, after amplifying the output from the line sensor24aand then subjecting the output to arithmetic operations in an arithmetic circuit, it is possible to know if the object is in focus or out of focus, if the object is in front focus or in back focus, and the Df amount.

—Description of Operation of Camera—

An operation of the camera100having such a configuration will be described with reference toFIGS. 8 and 9.FIG. 8is a flow chart showing an operation of the camera100up to when a release button is pressed all the way down, andFIG. 9is a flow chart showing an operation of the camera100after the release button is pressed all the way down.

Operations to be described below are controlled primarily by the body microcomputer50.

First, when the power switch40ais turned ON (step St1), communications are made between the camera body4and the interchangeable lens7(step St2). Specifically, the power is supplied to the body microcomputer50and various units in the camera body4, thus starting up the body microcomputer50. At the same time, the power is supplied to the lens microcomputer80and various units in the interchangeable lens7via the electric segments41aand71a,thus starting up the lens microcomputer80. The body microcomputer50and the lens microcomputer80are programmed so that information is exchanged therebetween upon start-up. For example, lens information regarding the interchangeable lens7is transmitted from the memory section of the lens microcomputer80to the body microcomputer50, and the lens information is stored in the memory section of the body microcomputer50.

Then, the body microcomputer50positions the focus lens group72at a predetermined reference position via the lens microcomputer80(step St3), and at the same time brings the shutter unit42to an open state (step St4). Then, the process proceeds to step St5, where the process stands by until the release button40bis pressed halfway down by the photographer.

Thus, light, which has passed through the interchangeable lens7and entered the camera body4, passes through the shutter unit42and further through the IR-cut/OLPF43to be incident upon the imaging unit1. Then, the object image formed on the imaging unit1is displayed on the image display section44, and the photographer can observe an erect image of the object on the image display section44. Specifically, the body microcomputer50reads the electric signal from the imaging device10via the imaging unit control section52at a predetermined cycle, performs a predetermined image process on the read-out electric signal, and then produces an image signal, based on which the body microcomputer50controls the image display control section55to display a live-view image on the image display section44.

A portion of light that has been incident upon the imaging unit1passes through the imaging device10to be incident upon the phase difference detection unit20.

Here, when the release button40bis pressed halfway down (i.e., when the51switch (not shown) is turned ON) by the photographer (step St5), the body microcomputer50amplifies the output from the line sensor24aof the phase difference detection unit20, and subjects the output to arithmetic operations in an arithmetic circuit to determine whether the object is in focus or out of focus (step St6). Moreover, the body microcomputer50obtains defocus information by determining whether the object is in front focus or in back focus and determining the amount of defocus (step St7). Then, the process proceeds to step St10. Here, the phase difference detection unit20of the present embodiment includes three sets of the condenser lens21a,the mask openings22aand22a,the separator lens23aand the line sensor24a,i.e., three distance measurement points at which to perform phase difference detection-type focus detection. Then, in a phase difference detection, the focus lens group72is driven based on the output from the line sensor24aof a set that corresponds to one of the distance measurement points selected by the photographer.

Alternatively, an automatic optimization algorithm may be programmed in the body microcomputer50so that the body microcomputer50selects one of the distance measurement points at which the camera and the object are closest to each other to drive the focus lens group72. In such a case, it is possible to reduce the probability of producing a picture focused on the background of an object.

On the other hand, in parallel to steps St6and St7, photometry is performed (step St8) and the image blur detection is started (step St9).

That is, in step St8, the amount of light incident upon the imaging device10is measured by the imaging device10. That is, in the present embodiment, the phase difference detection described above is performed by using light that has been incident upon and passed through the imaging device10, and it is therefore possible to perform photometry using the imaging device10in parallel to the phase difference detection.

Specifically, the body microcomputer50performs the photometry by receiving the electric signal from the imaging device10via the imaging unit control section52, and measuring the intensity of the object light based on the electric signal. Then, based on the results of the photometry, the body microcomputer50determines the shutter speed and the aperture value during exposure corresponding to a shooting mode according to a predetermined algorithm.

Then, when the photometry is completed in step St8, the image blur detection is started in step St9. Note that step St8and step St9may be performed in parallel.

Then, the process proceeds to step St10. Note that after step St9, the process may proceed to step St12instead of step St10.

In the present embodiment, the above focus detection based on the phase difference is performed by using light that has been incident upon and passed through the imaging device10as described above. Therefore, the photometry can be performed by using the imaging device10in parallel with the focus detection.

In step St10, the body microcomputer50drives the focus lens group72based on the defocus information obtained in step St7.

Then, the body microcomputer50determines whether the contrast peak has been detected (step St11). If the contrast peak has not been detected (NO), the process continues to drive the focus lens group72(step St10), and if the contrast peak has been detected (YES), driving the focus lens group72is halted and the focus lens group72is moved to the position at which the contrast value peaked, and the process proceeds to step St11.

Specifically, the body microcomputer50drives the focus lens group72at a high speed to a position that is spaced apart in the front or rear direction from the position that is estimated as the focus position based on the amount of defocus calculated in step St7. Then, the body microcomputer50detects the contrast peak while driving the focus lens group72at a low speed toward the position estimated as the focus position.

When the release button40bis pressed halfway down by the photographer, the shooting image and various information regarding the shooting operation are displayed on the image display section44, and the photographer can check the various information on the image display section44.

In step St12, the process stands by until the release button40bis pressed all the way down by photographer (i.e., until the S2switch (not shown) is turned ON). When the release button40bis pressed all the way down by the photographer, the body microcomputer50once brings the shutter unit42to a closed state (step St13). While the shutter unit42is in a closed state, the electrical charge stored in the light-receiving portions11b,11b,. . . , of the imaging device10is transferred in preparation for the exposure to be described later.

Then, the body microcomputer50starts correcting the image blur based on communication information between the camera body4and the interchangeable lens7or information specified by the photographer (step St14). Specifically, the body microcomputer50drives the blur correction lens driving section74ain the interchangeable lens7based on the information of the blur detection section56in the camera body4. Depending on the intention of the photographer, the photographer can select one of (i) using the blur detection section84and the blur correction lens driving section74ain the interchangeable lens7, (ii) using the blur detection section56and the blur correcting unit45in the camera body4, and (iii) using the blur detection section84in the interchangeable lens7and the blur correcting unit45in the camera body4.

Note that by starting driving the image blur correcting means at a point in time when the release button40bis pressed halfway down, it is possible to reduce the movement of the object to be focused and to more accurately perform AF.

In parallel to the start of the correction of the image blur, the body microcomputer50stops down the stop portion73via the lens microcomputer80to an aperture value as obtained from the results of the photometry in step St8(step St15).

When the correction of the image blur is started and the stop-down is completed, the body microcomputer50brings the shutter unit42to an open state based on the shutter speed obtained from the results of the photometry in step St8(step St16). Thus, by bringing the shutter unit42to an open state, light from the object is incident upon the imaging device10, and the imaging device10stores electrical charge for a predetermined amount of time (step St17).

Then, the body microcomputer50brings the shutter unit42to a closed state based on the shutter speed, and ends the exposure (step St18). After the completion of the exposure, the body microcomputer50reads out the image data from the imaging unit1via the imaging unit control section52, and outputs the image data to the image display control section55via the image reading/recording section53, after a predetermined image process. Thus, the shooting image is displayed on the image display section44. The body microcomputer50stores the image data in the image storing section58via the image recording control section54, as necessary.

Then, the body microcomputer50ends the image blur correction (step St19) and opens up the stop portion73(step St20). Then, the body microcomputer50brings the shutter unit42to an open state (step St21).

When the reset is complete, the lens microcomputer80notifies the body microcomputer50of the completion of the reset. The body microcomputer50waits for the reset completion information from the lens microcomputer80and the completion of a series of post-exposure processes and then ends the shooting sequence after checking the release button40bis not being pressed. Then, the process returns to step St5and stands by until the release button40bis pressed halfway down.

Note that when the power switch40ais turned OFF (step St22), the body microcomputer50moves the focus lens group72to a predetermined reference position (step St23) and brings the shutter unit42to a closed state (step St24). Then, the body microcomputer50and various units in the camera body4and the lens microcomputer80and various units in the interchangeable lens7are shut down.

Thus, in the AF operation of the present embodiment, defocus information is obtained by means of the phase difference detection unit20, and the focus lens group72is driven based on these defocus information. Then, the position of the focus lens group72at which the contrast value peaks as calculated based on the output from the imaging device10is detected, and the focus lens group72is moved to the position. Thus, the defocus information can be detected before driving the focus lens group72, and it is therefore not necessary to perform the step of tentatively driving the focus lens group72as with the conventional contrast detection-type AF, thereby shortening the amount of time for the autofocus process. Since the focal point is determined eventually by contrast detection-type AF, it is possible to directly obtain the contrast peak, and it is possible to realize high-precision focusing ability because various correction arithmetic operations such as the opening back correction (defocusing by the degree of opening of the stop) are not necessary unlike the phase difference detection-type AF. Particularly, it is possible to determine a focal point with a better precision than the conventional phase difference detection-type AF with respect to an object having a repetitive pattern or an object having a very low contrast.

Even though the AF operation of the present embodiment includes a phase difference detection, it obtains defocus information by means of the phase difference detection unit20using light which has passed through the imaging device10, and therefore it is possible to simultaneously perform the photometry by the imaging device10and obtain defocus information by means of the phase difference detection unit20. That is, since the phase difference detection unit20obtains defocus information by receiving light which has passed through the imaging device10, the imaging device10is always irradiated with light from the object when obtaining the defocus information. In view of this, the photometry is performed using light passing through the imaging device10when autofocusing. Then, it is no longer necessary to separately provide a sensor for the photometry, and it is possible to perform the photometry before the release button40bis pressed all the way down. Therefore, it is possible to shorten the amount of time (hereinafter referred to also as the “release time lag”) until the exposure is completed from when the release button40bis pressed all the way down.

Even with a configuration where the photometry is performed before the release button40bis pressed all the way down, the photometry may be performed in parallel with autofocus, thereby preventing the process time after the release button40bis pressed halfway down from becoming long. In this case, it is not necessary to provide a mirror for guiding light from the object to a photometry sensor or a phase difference detection unit.

In a conventional configuration, a portion of light guided to the imaging apparatus from the object is guided by means of a mirror, etc., to a phase difference detection unit provided outside the imaging apparatus. In contrast, light guided to the imaging unit1can be used as it is to detect the focus state by means of the phase difference detection unit20, and it is therefore possible to obtain the defocus information with a high precision.

Note that while the above embodiment employs a so-called hybrid-type AF in which contrast-type AF is performed after phase difference detection, the present invention is not limited to this. For example, the present invention may use phase difference detection-type AF in which AF is performed based on the defocus information obtained by the phase difference detection. Alternatively, the present invention may selectively perform one of the hybrid-type AF, the phase difference detection-type AF, and a contrast detection-type AF for determining a focus based only on the contrast value without performing phase difference detection.

Therefore, according to Embodiment 1, the imaging device10is configured so that light can pass therethrough, and the phase difference detection unit20is provided for performing phase difference detection-type focus detection by receiving light which has passed through the imaging device10, wherein the focus adjustment is performed as the body control section5controls the imaging device10, and the focus lens group72is driven and controlled based on at least the detection results of the phase difference detection unit20. Thus, various operations using the imaging device10and autofocus using the phase difference detection unit20can be performed in parallel, thus shortening the process time.

Even if various operations using the imaging device10and autofocus using the phase difference detection unit20are not performed in parallel, when light is incident upon the imaging device10, light is also incident upon the phase difference detection unit20with a configuration described above, and therefore the various operations using the imaging device10and the autofocus using the phase difference detection unit20can easily be switched from one to another by changing the control of the body control section5. That is, as compared with a conventional configuration where the direction in which light travels from the object is switched between the imaging device and the phase difference detection unit by moving a movable mirror back and forth, it is not necessary to move the movable mirror back and forth, and it is therefore possible to quickly switch the various operations using the imaging device10and the autofocus using the phase difference detection unit20from one to another, and it is possible to quietly switch the various operations using the imaging device10and the autofocus using the phase difference detection unit20from one to another because there cannot be a sound caused by moving the movable mirror back and forth.

Thus, it is possible to improve the usability of the camera100.

Specifically, the imaging device10is configured so that light can pass therethrough, and the phase difference detection unit20is provided for performing phase difference detection-type focus detection by receiving light which has passed through the imaging device10, so that AF using the phase difference detection unit20as in the phase difference detection-type AF described above and the photometry using the imaging device10can be performed in parallel. Thus, it is no longer necessary to perform the photometry after the release button40bis pressed all the way down, thereby reducing the release time lag. Even with a configuration where the photometry is performed before the release button40bis pressed all the way down, the photometry may be performed in parallel with autofocus, thereby preventing the process time after the release button40bis pressed halfway down from becoming long. Moreover, it is not necessary to separately provide a photometry sensor because the photometry is performed by using the imaging device10. Moreover, it is not necessary to provide a movable mirror for guiding light from the object to the photometry sensor or the phase difference detection unit. Thus, it is possible to reduce the power consumption.

Even with the hybrid-type AF described above, switching from the phase difference detection by the phase difference detection unit20to the contrast detection using the imaging device10can be made immediately by a control in the body control section5without the conventional switching of optical paths using a movable mirror, etc., and it is therefore possible to shorten the amount of time required for the hybrid-type AF. Since there is no need for the movable mirror, there is no noise from the movable mirror, and it is possible to perform the hybrid-type AF quietly.

Moreover, with a conventional configuration in which light traveling toward the imaging device10from the object is made to travel toward the phase difference detection unit which is provided in a different place than the back surface side of the imaging device10by using a movable mirror, or the like, the precision of the focus adjustment is not high because the optical path during exposure is different from that during the phase difference detection, and due to the placement error of the movable mirror, etc. In the present embodiment, since the phase difference detection-type focus detection can be performed with the same optical path as that during exposure because the phase difference detection unit20performs phase difference detection-type focus detection by receiving light which has passed through the imaging device10, and since there is no member such as a movable mirror that can cause errors, it is possible to obtain the amount of defocus based on the phase difference detection with a high precision.

Also in a case where the imaging device10is configured so that light can pass therethrough, the imaging device10can be reinforced by bonding the glass substrate19to the imaging device10. That is, if the imaging device10is configured so that light can pass therethrough, the imaging device10becomes very thin, thus lowering the mechanical strength thereof. In view of this, the imaging device10can be reinforced by bonding the glass substrate19to the imaging device10. In the present embodiment, while the glass substrate19is bonded to the back surface of the substrate11ain the back side-illuminated imaging device10, the glass substrate19is optically transparent and can allow light to pass therethrough, and it is therefore possible to prevent the glass substrate19from hindering light from being incident upon the imaging device10. That is, by using the glass substrate19, the imaging device10can be reinforced without influencing the entrance or exit of light to/from the imaging device10.

A variation of the present embodiment will now be described.FIG. 10is a cross-sectional view of an imaging unit210according to Variation 1.

While the imaging unit1is formed by bonding the imaging device10and the phase difference detection unit20together via the package31, an imaging unit201of Variation 1 is obtained by producing these components by a semiconductor process. The basic configurations of the imaging device10and the glass substrate19of the imaging unit201are similar to those of the imaging unit1. Note however that the protection layer18is absent on the front surface of the substrate11aof the imaging device10and, instead, a first low-refractive index layer225, a condenser lens layer221, a second low-refractive index layer226, a third low-refractive index layer227, a separator lens layer223, a fourth low-refractive index layer228and a protection layer229are layered in this order from the front surface of the substrate11a.

The first, second, third and fourth low-refractive index layers225,226,227and228are formed by a transparent material having a relatively low refractive index. On the other hand, the condenser lens layer221and the separator lens layer223are formed by a transparent material having a relatively high refractive index. Note that the first, second, third and fourth low-refractive index layers225,226,227and228may be of the same material or different materials. Similarly, the condenser lens layer221and the separator lens layer223may be of the same material or different materials.

A portion of the junction surface of the first low-refractive index layer225with the condenser lens layer221corresponding to the through hole14cof the exit-side mask14bprovided on the substrate11ais depressed in a concave shape toward the substrate11a.On the other hand, a portion of the junction surface of the condenser lens layer221with the first low-refractive index layer225corresponding to the through hole14cis protruding in a convex shape toward the substrate11a.That is, a portion of the junction surface of the first low-refractive index layer225with the condenser lens layer221corresponding to the through hole14cforms a lens surface, and the condenser lens layer221functions as a condenser lens.

A mask member222is provided at the junction surface between the second low-refractive index layer226and the third low-refractive index layer227. The mask member222includes two mask openings222aand222aat positions corresponding to the through hole14c.

Moreover, a portion of the junction surface of the third low-refractive index layer227with the separator lens layer223corresponding to the through hole14cis depressed in a concave shape toward the substrate11a.Specifically, the concave-shaped portion has a shape obtained by placing two concave surfaces next to each other. On the other hand, a portion of the junction surface of the separator lens layer223with the third low-refractive index layer227corresponding to the through hole14cis protruding in a convex shape toward the substrate11ain conformity with the third low-refractive index layer227. Specifically, this convex-shaped portion has a shape obtained by placing two convex surfaces next to each other. That is, a portion of the junction surface between the third low-refractive index layer227and the separator lens layer223corresponding to the through hole14cforms two lens surfaces, and the separator lens layer223functions as a separator lens.

Moreover, a line sensor224is provided at the junction surface between the fourth low-refractive index layer228and the protection layer229at positions corresponding to the through hole14c.

The first low-refractive index layer225, the condenser lens layer221, the second low-refractive index layer226, the third low-refractive index layer227, the separator lens layer223, the fourth low-refractive index layer228and the protection layer229together form a phase difference detection unit220. The glass substrate19, the imaging device10and the phase difference detection unit220may be produced by a semiconductor process as described above.

Next, an imaging device310according to Variation 2 will be described with reference toFIG. 11.FIG. 11is a cross-sectional view of the imaging device310.

The imaging device310is a CMOS image sensor, unlike the imaging device10which is a CCD image sensor. Specifically, the imaging device310includes a photoelectric conversion section311formed by a semiconductor material, a transistor312, a signal line313, a mask314, and a color filter315.

The photoelectric conversion section311includes a substrate311a,and light-receiving portions311b,311b,. . . , each formed by a photodiode. The transistor312is provided for each light-receiving portion311b.The electrical charge stored in the light-receiving portion311bis amplified through the transistor312and is output to the outside through the signal line313.

The mask314is formed by an incident-side mask314aand an exit-side mask314b,as is the mask14. The incident-side mask314ais provided adjacent to the light-receiving portion311b,and prevents light from being incident upon the transistor312and the signal line313. The exit-side mask314bincludes a plurality of through holes314cfor allowing light which has passed through the light-receiving portion311bto exit to the back surface side of the imaging device310.

The color filter315has a similar configuration to that of the color filter15.

Since the amplification factor of the transistor312can be set for each light-receiving portion311bin a CMOS image sensor, the amplification factor of each transistor312may be determined depending on whether the light-receiving portion311bis located at a position corresponding to the through hole314cand based on the color of the color filter315corresponding to the light-receiving portion311bso that it is possible to prevent portions of an image corresponding to the through holes314c,314c,. . . , from being shot inappropriately.

Now, an imaging unit401according to Variation 3 will be described with reference toFIGS. 12 and 13.FIG. 12is a cross-sectional view of the imaging device410of the imaging unit401, andFIG. 13is a cross-sectional view showing how the imaging device410is attached to a circuit substrate432.

The imaging unit401differs from the imaging unit1in that light from the object is incident upon the front surface, rather than the back surface, of the substrate of the imaging device. Like elements to those of the imaging unit1will be denoted by like reference numerals and will not be described below. The description below will focus on the differences therebetween.

The imaging unit401includes the imaging device410for converting an object image into an electric signal, the glass substrate19bonded to the imaging device410, a package for holding the imaging device410, and a phase difference detection unit for performing phase difference detection-type focus detection. The package and the phase difference detection unit have a similar configuration to that of the imaging unit1and are not shown in the figure.

The imaging device410is a back side-illuminated interline CCD image sensor, and includes the photoelectric conversion section11formed by a semiconductor material, the vertical register12, the transfer path13, a mask414, the color filter15, and a microlens416, as shown inFIG. 12.

The light-receiving portions11b,11b,. . . , are each provided in one of minute square pixel regions arranged in a matrix pattern on the front surface of the substrate11a.The vertical register12is provided adjacent to each light-receiving portion11bon the front surface of the substrate11a.Moreover, the transfer path13is provided so as to overlap the vertical register12. The mask414is provided so as to cover the vertical register12and the transfer path13.

Unlike the mask14of the imaging unit1, the mask414is provided only on the side on which light from the object is incident. Specifically, the mask414is provided so as to cover the vertical register12and the transfer path13from the side opposite to the substrate11a.Thus, the mask414prevents light from the object side from being incident upon the vertical register12and the transfer path13.

Moreover, the protection layer18of an optically transparent resin is provided on the front surface of the substrate11aso as to cover the light-receiving portion11b,the vertical register12, the transfer path13and the mask414.

The color filter15is layered on the front surface of the protection layer18(i.e., the surface of the protection layer18that is opposite to the substrate11a). The color filter15is a color filter containing a dye-based or pigment-based coloring matter.

The microlens416is formed by an optically transparent resin for condensing light to be incident upon the light-receiving portion11b,and is layered on the color filter15. Specifically, the microlens416is provided for each light-receiving portion11b,i.e., for each color filter15, and is a convex lens protruding in a convex shape toward the object side (i.e., the side opposite to the substrate11a). With the microlens416, the light-receiving portion11bcan be irradiated efficiently.

Moreover, a protection layer17of an optically transparent resin is layered on the front surface (the convex surface) of the microlens416.

The glass substrate19is anodically-bonded to the back surface of the substrate11a.

In the imaging device10having such a configuration, light which has been condensed by the microlens416,416, . . . , is incident upon color filters15r,15g,15b,and only light of the color corresponding to the color filters15pass through the color filters15to reach the front surface of the substrate11a.On the substrate11a,only the light-receiving portions11b,11b,. . . , are exposed, with the vertical register12, the transfer path13, etc., being covered by the mask414, and therefore light which has reached the substrate11ais incident only upon the light-receiving portions11b,11b,. . . . Each light-receiving portion11babsorbs light to generate electrical charge. The electrical charge generated by each light-receiving portion11bis sent to the amplifier via the vertical register12and the transfer path13, and is output as an electric signal. Since light of a particular color which has passed through one of the color filters15r,15gand15bis incident upon each of the light-receiving portions11b,11b,. . . , the amount of received light of the color corresponding to the color filter15is obtained as an output from the light-receiving portion11b.Thus, the imaging device410performs photoelectric conversion by the light-receiving portions11b,11b,. . . , across the entire imaging surface, thereby converting an object image formed on the imaging surface into an electric signal.

On the other hand, a portion of light incident upon the light-receiving portion11bis not absorbed by the light-receiving portion11bbut passes through the light-receiving portion11b.Since the substrate11ais very thin (i.e., since it is formed to such a thickness that light passes through the substrate11a), light which has passed through the light-receiving portion11bpasses through the substrate11aand then through the glass substrate19to exit toward the back surface side of the imaging device410.

As with the imaging unit1, a phase difference detection unit is provided on the back surface side of the imaging device410, and the phase difference detection unit performs phase difference detection-type focus detection by using light which has passed through the imaging device410.

The imaging device410having such a configuration is mounted on the circuit substrate432of the package.

Specifically, in the peripheral portion of the substrate11aof the imaging device410, the light-receiving portion11b,the vertical register12, the transfer path13, the mask414, the color filter15, the microlens416, the protection layers17and18, etc., are absent, with an interconnect which enables electrical connection with the transfer path13, the vertical register12, etc., exposed thereon. On the other hand, a circuit pattern is provided on the back surface (the surface opposite to the object) of the circuit substrate432and located so as to face the interconnect of the substrate11aof the imaging device410. Then, the peripheral portion of the substrate11aof the imaging device410is laid over the circuit substrate432from the side opposite to the object, and they are bonded together through thermal fusion, thereby electrically connecting the interconnect of the substrate11aof the imaging device410with the circuit pattern of the circuit substrate432, as shown inFIG. 13.

Therefore, also in a case where the imaging device410is configured so that light can pass therethrough, the imaging device410can be reinforced by bonding the glass substrate19to the imaging device410. That is, if the imaging device410is configured so that light can pass therethrough, the imaging device410becomes very thin, thus lowering the mechanical strength thereof In view of this, the imaging device410can be reinforced by bonding the glass substrate19to the imaging device410. While the glass substrate19is bonded to the back surface of the substrate11ain a configuration where light is allowed to be incident from the front surface of the substrate11a,as opposed to a back side-illuminated configuration, since the glass substrate19is optically transparent and allows light to pass therethrough, it is possible to prevent the glass substrate19from hindering light from exiting the imaging device410. That is, by using the glass substrate19, it is possible to reinforce the imaging device410without influencing the exit of light from the imaging device410.

Other effects and advantages similar to those of the imaging unit1will also be obtained.

Next, an imaging unit501according to Embodiment 2 of the present invention will be described with reference toFIG. 14.FIG. 14is a cross-sectional view of an imaging device510of the imaging unit501.

The imaging unit501of Embodiment 2 differs from Embodiment 1 in that the phase difference detection unit is absent. Like elements to those of Embodiment 1 will be denoted by like reference numerals and will not be described below. The description below will focus on the differences therebetween.

The imaging unit501includes the imaging device510for converting an object image into an electric signal, and the glass substrate19bonded to the imaging device510.

The configuration of the imaging device510is similar to Embodiment 1 except for the configuration of an exit-side mask514b.That is, a mask514includes an incident-side mask514aprovided on the front surface of the substrate11a,and the exit-side mask514bprovided so as to cover the light-receiving portion11b,the vertical register12and the transfer path13from the side opposite to the substrate11a.The exit-side mask514bis not provided with through holes, and completely covers the light-receiving portion11b,the vertical register12and the transfer path13from the side opposite to the substrate11a.

In the imaging device510having such a configuration, light which has passed through the light-receiving portions11b,11b,. . . , is all reflected by the exit-side mask514bto be again incident upon the light-receiving portions11b,11b,. . . , and the light is not allowed to exit to the back surface side of the imaging device510.

That is, the imaging device510of Embodiment 2 is a back side-illuminated imaging device without phase difference detection. Thus, irrespective of whether or not phase difference detection-type focus detection is performed, it is necessary to allow light to pass through the substrate11aas long as it is a back side-illuminated imaging device. While it is necessary to form the substrate11ato such a thickness that light passes therethrough in a configuration where light is allowed to pass through the substrate11a,it is possible to reinforce the imaging device510without influencing the incidence of light upon the imaging device510by bonding the glass substrate19to the imaging device510as described above.

The present invention may have the following configurations for the embodiments above.

For example, the configuration of the imaging device is not limited to the above configuration, but may be any configuration as long as it is a configuration where light passes through the imaging device. The phase difference detection unit is also not limited to the above configuration.

The bonding between the imaging device and the optically transparent substrate may be realized by, for example, forming the imaging device on the optically transparent substrate.

While the above embodiments are directed to a configuration where the imaging unit1is provided in a camera, the present invention is not limited to this. For example, the imaging unit1may be provided in a video camera.

While the description above has been directed to a configuration where AF is started when the release button40bis pressed halfway down by the photographer (i.e., when the S1switch is turned ON), AF may be started before the release button40bis pressed halfway down. While the description above has been directed to a configuration where AF is ended when it is determined that a focus has been reached, the process may continue to perform AF even after such determination or may continuously perform AF without making such determination.

In the above embodiment, the substrate11amay be removed completely by polishing, etching, etc. In such a case, the glass substrate19may be directly bonded to the light-receiving portion11b.The light-receiving portion11bmay be formed directly on the glass substrate19.

Note that the embodiments described above are essentially preferred embodiments, and are not intended to limit the scope of the present invention, the applications thereof, or the uses thereof.

Industrial Applicability

As described above, the present invention is useful for an imaging unit including an imaging device for performing photoelectric conversion.

Description Of Reference Characters

20,220Phase difference detection unit (phase difference detection section)