The entire disclosure of Japanese Patent Application No. 2011-048739, filed Mar. 7, 2011 is incorporated by reference herein. The entire disclosure of Japanese Patent Application No. 2011-051445, filed Mar. 9, 2011 is incorporated by reference herein.
1. Technical Field
The present invention relates to a digital camera and a shutter operation estimating method.
2. Related Art
In general, an imaging apparatus applicable to a digital camera includes an imaging element that accumulates received light as charge and a focal-plane-type shutter that is traveled to block the imaging element from light. In the past, an imaging apparatus was suggested which adjusts an exposure period by controlling a start time of charge accumulation scanning of the imaging element corresponding to travel of an anterior curtain and a start time of shutter travel corresponding to travel of a posterior curtain, when a still image is photographed (for example, see Japanese Patent No. 3988215 (JP-A-11-41523).
Further, an electronic camera using an electronic shutter and a mechanical shutter together has been suggested. Such an electronic camera adjusts an exposure period deviation caused due to an individual difference of the mechanical delay from reception of an instruction of a closing operation of the mechanical shutter to start of the actual closing operation by executing previous and subsequent adjustment of a charge accumulation start timing or a shutter driving start timing of the electronic shutter while evaluating an exposure amount based on a signal integrated value corresponding to one-screen bright data (for example, JP-A-11-234574).
In digital cameras, adjusting an exposure period properly is one of the important tasks. In the method of adjusting the exposure period in the latter camera described above, however, it is necessary to photograph a light source determined under a given environment in order to adjust the exposure period deviation caused due to the individual difference of the mechanical shutters. Further, when the mechanical shutter changes over time, a user may not easily adjust the exposure period. Therefore, the user may not obtain a proper photographed image in some cases.
An advantage of some aspects of the invention is that it provides a digital camera and a shutter operation estimating method capable of adjusting an exposure period of an image sensor more properly.
According to an aspect of the invention, there is provided a digital camera including: an image sensor that generates an image signal based on an exposure amount; a shutter that is moved in a predetermined direction to block light arriving at the image sensor; a movement control unit that moves the shutter to block the light arriving at the image sensor at which the light has arrived; a movement detecting unit that detects the shutter moving by a predetermined amount from movement start; and an operation estimating unit that estimates the movement operation of the shutter based on a detection timing of the movement detecting unit.
In the digital camera according to the aspect of the invention, the shutter blocking the light arriving at the image sensor in the predetermined direction is moved to block the light arriving at the image sensor at which the light has arrived. It is detected that the shutter moves by the predetermined amount from the movement start and the movement operation of the shutter is estimated based on the detection timing of the movement of the shutter by the predetermined amount. Accordingly, when it is detected that the shutter moves by the predetermined amount from the movement start and the estimation result of the estimated movement operation of the shutter is used to control the exposure period of the image sensor, it is possible to adjust the exposure period of the image sensor. That is, it is possible to adjust the exposure period of the image sensor more properly. Here, the movement detecting unit may detect that the shutter moves and reaches a detection position between the end of the shutter in an open state on the side of the image sensor and the end of the image sensor on the side of the shutter. Further, when only a partial region (referred to as an effective pixel region) of an image sensor circuit is effective, the image sensor described here means the image sensor circuit of the effective pixel region.
The digital camera according to the aspect of the invention may further include a reset control unit that starts reset scanning of the exposure amount of the image sensor in the predetermined direction in response to the movement operation of the shutter estimated by the operation estimating unit until the previous time. Then, by adjusting a timing at which the exposure amount of the image sensor is reset, it is possible to adjust the exposure period of the image sensor more properly. In this case, the reset control unit may execute the reset scanning of the exposure amount of the image sensor in the predetermined direction in accordance with a change in a speed corresponding to the movement operation of the shutter estimated by the operation estimating unit until the previous time. Alternatively, the reset control unit may start the reset scanning of the exposure amount of the image sensor in the predetermined direction at a timing corresponding to the movement operation of the shutter estimated by the operation estimating unit until the previous time. Here, the reset scanning of the exposure amount in the predetermined direction is executed by executing the reset of the exposure amount of the image sensor in sequence in the predetermined direction. The reset of the exposure amount includes executing reset of the exposure amount in a state where the reset of the exposure amount is not executed, finishing the reset of the exposure amount in a state where the reset of the exposure amount continues to be executed and finishing the reset as the finishing result of a reading process or the like by executing the rest as the result of the reading process or the like.
In the digital camera according to the aspect of the invention, when the movement operation of the shutter estimated by the operation estimating unit until the previous time is later than a predetermined operation, the movement control unit may start moving the shutter at a timing earlier compared to a case where the estimated movement operation of the shutter is earlier than the predetermined operation. In order words, the movement control unit may start moving the shutter at a timing of a tendency in which the movement operation of the shutter is earlier as the estimated movement operation of the shutter is later (for example, a proportional or step-like (gradual) tendency in which the movement operation of the shutter is earlier as the estimated operation of the shutter is later). Thus, by adjusting the timing at which the movement of the shutter starts, it is possible to adjust the exposure period of the image sensor more properly.
In the digital camera according to the aspect of the invention, the operation estimating unit may estimate a current-time movement operation of the shutter based on the movement operation of the shutter estimated by the operation estimating unit until the previous time and a current-time detection timing of the movement detecting unit. Thus, it is possible to estimate the movement operation of the shutter more properly.
In the digital camera according to the aspect of the invention, the movement detecting unit may detect the movement of the shutter by detecting an operation of an interlocking member interlocking with the movement of the shutter.
In the digital camera according to the aspect of the invention, the movement detecting unit may detect movements of a plurality of amounts including movement of a first predetermined amount and movement of a second predetermined amount larger than the first predetermined amount. The operation estimating unit may estimate the movement operation of the shutter based on a plurality of detection timings for the movements of the plurality of amounts of the shutter. Thus, it is possible to estimate the movement operation of the shutter more properly.
In the digital camera according to the aspect of the invention, when the exposure period is shorter than a period threshold value, the reset control unit can start the reset scanning of the exposure amount of the image sensor in the predetermined direction at the timing which corresponds to the detection of the movement detecting unit after the movement start of the shutter and corresponds to the detection of the movement detecting unit after the movement start of the shutter before the previous time. When the exposure period is longer than the period threshold value, the reset control unit can start the reset scanning of the exposure amount of the image sensor in the predetermined direction at the timing which does not correspond to the detection of the movement detecting unit after the movement start of the shutter and corresponds to the detection of the movement detecting unit after the movement start of the shutter before the previous time.
According to another aspect of the invention, there is provided a shutter operation estimating method of a digital camera which includes an image sensor that generates an image signal based on an exposure amount and a shutter that is moved in a predetermined direction to block light arriving at the image sensor. The shutter operation estimating method includes: moving the shutter to block the light arriving at the image sensor at which the light has arrived; detecting the shutter moving by a predetermined amount from movement start; and estimating the movement operation of the shutter based on a detection timing in the detecting of the movement of the shutter.
When the estimation result of the movement operation of the shutter estimated by the shutter operation estimating method of the digital camera according to the aspect of the invention is used for the control of the exposure period of the image sensor, the exposure period of the image sensor can be adjusted. That is, it is possible to adjust the exposure period of the image sensor more properly. Further, in the shutter operation estimating method of the digital camera, the units of the above-described digital camera according to the aspect of the invention may be used and realizing each function of the above-described digital camera according to the aspect of the invention may be further included. According to a still another aspect of the invention, there is provided a computer program causing a camera to realize the above-mentioned functions and a recording medium of the program. Of course, a recording medium of the computer program may be a magnetic recording medium, a magneto-optical recording medium, or any recording medium developed in future.
The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Hereinafter, embodiments of the invention will be described with reference to the drawings.
The digital camera 10 according to the embodiment includes: an electronic imaging unit 20 that outputs a signal for a photographed image based on an image signal generated through photoelectric conversion of a subject; an image processing device 60 that inputs the signal output from the electronic imaging unit 20, executes predetermined image processing, and generates image data or an image file of the photographed image; a display control device 70 that displays the image data input from the image processing device 60 on an EVF (Electronic View Finder) 72 or a liquid crystal monitor 74; an operation button group 80 that includes various kinds of buttons operated by a user; a memory card 50 that is capable of storing the image file generated by the image processing device 60; a battery 55 that supplies power to each unit of the digital camera 10; and a main controller 40 that controls the entire apparatus.
The electronic imaging unit 20 includes a photographic lens 21 that is mounted on the body of the digital camera 10 so as to replaced through a lens mount (not shown), an image sensor 22 that converts light input via the photographic lens 21 into an electric signal through photoelectric conversion; a shutter mechanism 23 that is disposed between the photographic lens 21 and the image sensor 22, an analog front-end (AFE) 28 that converts the electric signal output from the image sensor 22 into a digital signal and outputs the digital signal; and a pulse generating circuit 30 that outputs a clock signal to the image sensor 22 or the image processing device 60.
The photographic lens 21 includes a group of a plurality of lenses configured by convex lenses and concave lenses and a diaphragm mechanism 21a that adjusts the amount of light incident on the image sensor 22 or an auto-focus mechanism 21b that executes focusing based on information from a range-finding sensor (not shown) or the photographic lens 21. The diaphragm mechanism 21a or the auto-focus mechanism 21b is controlled by driving a motor of each mechanism in accordance with a signal from a main controller 40.
The image sensor 22 is configured as a COMS image sensor that includes a plurality of photodiodes (not shown) arranged in a matrix form and forming an imaging surface 22a (see
The shutter mechanism 23 functions as a mechanical posterior curtain with respect to the electronic anterior curtain. As shown in
In the shutter mechanism 23, the shutter blades 25 travel to block an area broader than the opening 24a of the ground plate 24. Therefore, as shown in
The image processing device 60 include various kinds of image processing function blocks (not shown) that execute general image processing of a digital camera such as a color interpolation process or a white balance process of RGB pixels, a color reproduction process, re-size processing, a gamma correction process, or an image file generation process. The image processing device 60 inputs the digital signal output from the electronic imaging unit 20 and input the clock signal from the pulse generating circuit 30, and executes the image processing to generate a photographed image, or converts the generated photographed image into an image with a predetermined format and adds photograph information to generate an image file. The image processing device 60 sequentially inputs the digital signals output from the electronic imaging unit 20 at a predetermined period interval and generate a live-view display image.
The display control device 70 displays the photographed image generated by the image processing device 60 on the liquid crystal monitor 74 or executes a live-view display process of sequentially displaying the live-view display images generated by the image processing device 60 on the EVF 72 or the liquid crystal monitor 74.
The operation button group 80 includes a shutter button 80a that outputs an instruction to photograph a subject to the main controller 40 when the user presses down the shutter button, a plurality of setting buttons 80b that set various setting values for the photographing such as a shutter speed, a stop value, and an exposure value, and a power button 80c that gives an instruction of power-on or power-off.
The main controller 40 is configured by a microprocessor which includes the CPU 42 as a main unit. The main controller 40 includes a ROM 44 that stores processing programs and various tables, a RAM 46 that temporarily stores data, a flash memory 48 that is capable of writing data and keeps data even when power is turned off, and an input/output port (not shown). The main controller 40 is supplied with detection signals (ON and OFF signals) from the position sensor 25a that detects the shutter blades 25 traveling by a predetermined amount from the movement start of the shutter blades 25, various kinds of operation signals from the operation button group 80, information regarding the photographic lens 21, image files read from the memory card 50, various kinds of images from the image processing device 60, and the like. Further, the main controller 40 outputs a driving signal for the photographic lens 21, a control signal, which is used to control the motor (not shown) or control the conduction to the electromagnet, for the shutter mechanism 23, a control signal for the pulse generating circuit 30, a control signal for the vertical driving modulation circuit 32, an image file written into the memory card 50, an image processing instruction for the image processing device 60, a display control instruction for the display control device 70, and the like.
Various setting values such as a shutter speed are set in the digital camera 10 having the above-described configuration according to the embodiment. When a photograph instruction is output in response to an operation of the shutter button 80a, the main controller 40 executes various kinds of exposure controls to control the rest scanning of the exposure amount of the image sensor 22 or the travelling of the shutter blades 25 and read scanning of the image signal from the image sensor 22. Finally, an image file generated from the output signal of the electronic imaging unit 20 by the image processing device 60 is stored in the memory card 50. According to various kinds of exposure controls on the imaging surface 22a of the image sensor 22, as shown in
Next, an operation of the digital camera 10 having the above-described configuration, particularly, an exposure operation will be described according to this embodiment.
When the exposure processing routine is executed, the CPU 42 of the main controller 40 first inputs data necessary for an exposure process, such as a set exposure period Tex or a timing correction amount ΔT of a travel start timing of the travel (hereinafter, referred to as shutter travel) of the shutter blades 25 (step S100). Here, the exposure period Tex set as a shutter speed when the user operates the setting button 80b or set by an automatic exposure processing routine (not shown) may be input. The timing correction amount ΔT is calculated as an average value or a median value of the delay periods caused due to, for example, the temporal change in the shutter travel operation estimated at the previous three-time photograph times. The timing correction amount ΔT will be described in detail later.
Next, a reset timing of the reset scanning of the image sensor 22 and the a basic travel start timing, which is a basic value of the travel start timing of the shutter blades 25, are set based on the input exposure period Tex (step S110). A timing obtained by correcting the set basic travel start timing so as to be earlier by the timing correction amount ΔT is set as the travel start timing (step S120). In the embodiment, the reset timing is set to a time at each position (each line) of the imaging surface 22a in a vertical direction when the photograph instruction is input, and the basic travel start timing is set to a time after the photograph instruction is input. In the embodiment, the reset timing and the basic travel start timing are set by determining a relation between the exposure period Tex and the reset timing and the basic travel start timing, from which the exposure period Tex in the default state at the shipment of the digital camera 10 is obtained, in advance by an experiment or analysis, storing the relation as a timing set map in the ROM 44, and deriving the corresponding reset timing and the corresponding basic travel start timing from the timing set map when the exposure period Tex is given. When, the corresponding reset timing and the corresponding basic travel start timing are derived from the stored timing set map. Even when the basic travel start timing is corrected to be earlier only by the timing correction amount ΔT, the timing set map may be determined so that the travel start timing is not a timing earlier than the current timing. Alternatively, when the travel start timing is a timing earlier than the current timing, both the reset timing and the travel start timing may be made to be later by the earlier time.
In this way, when the reset timing of the reset scanning of the image sensor 22 and the travel start timing of the shutter blades 25 are set, it is determined whether the shutter travel starts earlier or the reset scanning of the image sensor 22 starts earlier based on the set values of the reset timing and the travel start timing (step S130). When it is determined that the shutter travel starts earlier, the reset scanning of the exposure amount of the image sensor 22 starts at the set reset timing (step S140), and then the shutter travel starts at the set the travel start timing (step S150). The reset scanning is executed by outputting the control signals to the pulse generating circuit 30 and the vertical driving modulation circuit 32, respectively. The shutter travel starts by outputting a control signal for instructing the start of the travel to the shutter mechanism 23.
In this way, the read scanning is executed from the line in which the shutter travel ends, and then when the read scanning ends for all of the lines (step S180), the exposure processing routine ends. When the reset scanning starts earlier than the shutter travel, that is, the exposure period Tex is relatively long (the shutter speed is relatively low), the exposure of the image sensor 22 can be executed through the above process for the set exposure period Tex.
When it is determined that the shutter travel starts earlier than the reset scanning in step S130, the shutter travel starts at the set travel start timing (step S160), and then the reset scanning starts at the set reset timing (step S170). Finally, the read scanning is executed (step S180) and the exposure processing routine ends.
Next, setting of the timing correction amount ΔT used to correct the basic travel start timing will be described.
When the correction amount setting routine is executed, the CPU 42 of the main controller 40 again stores a correction amount ΔT1 set at the time of executing the previous correction account setting routine and stored in a predetermined region of the flash memory 48 and a correction amount ΔT2 set at the time of executing the previous correction account setting routine and stored in a predetermined region of the flash memory 48, which are basis values of the calculation of all the timing correction amounts ΔT, as correction amounts ΔT2 and ΔT3, respectively, in the predetermined region of the flash memory 48 (step S200), and then input the correction amounts ΔT2 and ΔT3 stored again (step S210). Here, the correction amounts ΔT1, ΔT2, and ΔT3 are amounts estimated as a delay period caused due to the temporal change or the like of all the shutter travel operations. The correction amount ΔT1 is a value set by executing the correction amount setting routine at the current time. The correction amount ΔT2 is a value set by executing the correction amount setting routine at the previous time. The correction amount ΔT3 is a value set by executing the correction amount setting routine at the time before last. Of course, the number of correction amounts to be stored is not limited thereto, but one or three or more correction amounts may be stored.
Subsequently, the input of the detection signal transmitted from the position sensor 25a is waited (step S220). When the detection signal transmitted from the position sensor 25a is input, a necessary detection period Td is set as a period elapsed after the start of the shutter travel by the use of a period measured by a timer (not shown) (step S230). In the embodiment, a predetermined amount of movement of the shutter blades 25 to be detected by the position sensor 25a is a movement amount which is determined in advance by an experiment or the like and is necessary for grasping a change tendency in which the travel of the shutter blades 25 is delayed or advanced due to an individual difference or a temporal change of the shutter mechanism 23.
The correction amount ΔT1 set in the correction amount setting routine of the current time is set based on the necessary detection period Td of the set position sensor 25a and is stored in a predetermined region of the flash memory 48 (step S240). The average value of the correction amounts ΔT1, ΔT2, and ΔT3 is set as the timing correction amount ΔT and is stored in a predetermined region of the flash memory 48 (step S250), and then the correction amount setting routine ends. As the timing correction amount ΔT, the median value of the correction amounts ΔT1, ΔT2, and ΔT3 may be used, a weighted average value obtained by weighting the correction amount ΔT1 may be used, or a value obtained by another calculation may be used. In the embodiment, the correction amount ΔT1 is set by determining a relation between the necessary detection period Td of the position sensor 25a and the correction amount ΔT1 in advance by an experiment or analysis, storing the relation as a correction amount setting map in the ROM 44, and deriving the corresponding correction amount ΔT1 from the stored correction amount setting map when the necessary detection period Td is given. A setting example of the correction amount ΔT1 and the meaning of the timing correction amount ΔT will be described later.
Accordingly, the process of setting the correction amount ΔT1 based on the necessary detection period Td of the position sensor 25a in step S240 can be said to be a process of estimating that the shutter travel is later as the detection timing of the position sensor 25a is later. In the correction amount setting map, for example, the average value or the like of a delay period of the timing, at which the shutter blades 25 reach the lower end of the imaging surface 22a, from the basic state and a delay period of the timing, at which the shutter blades 25 reach the upper end of the imaging surface 22a, from the basic state can be set as the correction amount ΔT1. Further, the correction amount of the shutter travel start timing can be obtained more properly by setting, as the timing correction amount ΔT, the average value or the median value of the estimated correction amount ΔT1 and the correction amounts ΔT2 and ΔT3 estimated at the previous photograph time. In the digital camera 10 according to the embodiment, it is possible to determine the exposure period of the image sensor 22 more properly, since the shutter travel start timing is adjusted at the subsequent photograph time by the use of the calculated timing correction amount ΔT. Further, since the timing correction amount ΔT can be set with a positive value or a negative value, it is possible to adjust the exposure period of the image sensor 22 properly in accordance with a change in the shutter travel method due to the individual difference of the shutter mechanism 23 or the temporal change.
Here, a correspondence relation between the constituent elements of this embodiment and the constituent elements of the invention will be described. The image sensor 22 of this embodiment corresponds to an “image sensor” of the invention. The shutter blade 25 corresponds to a “shutter.” The main controller 40 that controls the shutter mechanism 23 to start traveling the shutter blades 25 at the set travel start timing and executes the processes of step S150 and step S160 of the exposure processing routine of
In the digital camera 10 described above in this embodiment, the shutter blades 25 travel to block the light arriving at the image sensor 22 at which the light has arrived. Then, the movement of the predetermined amount from the start of the shutter travel is detected, the movement operation of the shutter blades 25 is estimated based on the detection timing of the movement of the shutter blades 25 by the predetermined amount, and the correction amount ΔT1 is determined. Further, the shutter travel starts at the travel start timing earlier than the basic travel start timing by the timing correction amount ΔT based on the correction amount ΔT1 set until the previous time. Thus, it is possible to adjust the exposure period of the image sensor 22 more properly.
The invention is not limited to the above-described embodiment, but may be, of course, modified in various forms within the technical scope of the invention.
In the above-described embodiment, the correction amount ΔT is set to set the travel start timing of the shutter travel based on the detection timing of the position sensor 25a. Instead, a timing correction amount may be set to set the reset timing of the reset scanning of the image sensor 22. In this case, the exposure processing routine of
In the exposure processing routine of
In the correction amount setting routine of
Thus, the correction amount of the reset timing of the reset scanning of the image sensor 22 can be obtained more properly by setting, as the timing correction amount ΔT(y), the average value or the median value of the estimated correction amount ΔT1(y) and the correction amounts ΔT2(y) and ΔT3(y) estimated at the previous photograph time. By adjusting the reset timing at the next photograph time by the use of the calculated timing correction amount ΔT(y), it is possible to determine the exposure period of the image sensor 22 more properly.
In the above-described embodiment, the travel start timing of the shutter travel is adjusted by setting the timing correction amount ΔT based on the detection timing of the position sensor 25a. However, each timing may be adjusted by dividing the timing correction amount ΔT set in the same manner at a predetermined division ratio (for example, a value of ½) between adjustment by which the travel start timing of the shutter travel is made to be earlier and adjustment by which the reset timing of the image sensor 22 is made to be later.
In the above-described embodiment, the timing correction amount ΔT is set based on the correction amount ΔT1 set in the correction amount setting routine and the correction amounts ΔT2 and ΔT3 set in the correction amount setting routine until the previous time. However, the correction amount ΔT1 may be set as the timing correction amount ΔT without use of the correction amounts ΔT2 and ΔT3.
In the above-described embodiment, the position sensor 25a, which detects that the front end of the shutter blades 25 starts moving in the open state, travels upward by the predetermined amount, and reaches the detection position, is used as a sensor that detects the shutter blades 25 moving by the predetermined amount from the movement start. Instead, for example, a rotation position sensor or the like may be used which detect the rotation position of the driving arm 26a of the shutter mechanism 23.
In the above-described embodiment, one position sensor 25a is provided which detect the shutter blades 25 moving from the movement start by the predetermined amount. However, two or more position sensors may be provided. For example, as shown in
That is, the shutter mechanism may includes the position sensor 125b that detects the shutter blades 25 moving by the second predetermined amount, which is a movement amount of the shutter blades 25 from the movement start up to the position at which the light starts to be blocked in the imaging surface 22a, or the position sensor 125c that detects the shutter blades 25 moving by the third predetermined amount.
In the above-described embodiment, the larger correction amount ΔT1 is set as the detection timing of the position sensor 25a is later by the use of the correction amount setting map, that is, the correction amount ΔT1 is set to be larger proportionally as the detection timing of the position sensor 25a is later. Instead, the correction amount ΔT1 may be set to be larger stepwise (gradually) as the detection timing of the position sensor 25a is later.
In the above-described embodiment, the case has hitherto been described in which the photodiodes of the image sensor 22 are effective. However, all of the plurality of photodiodes may not be effective, but the photodiodes in a partial region (also referred to as an effective pixel region) may be effective. In this case, the photodiodes in a region other than the effective pixel region are covered to block light, are made not to read charge, or made to ignore the read charge or signal. Then, the shutter blades 25 are moved so that light arriving at the effective pixel region of the image sensor 22 at which the light has arrived is blocked, it is detected that the shutter blades 25 are moved from the movement start by a predetermined amount, and the movement operation of the shutter blades 25 may be estimated based on the detection timing of the movement of the shutter blades 25 by the predetermined amount.
In the above-described embodiment, the travel start timing of the shutter travel or the reset start timing is corrected based on the detection result of the position sensor. However, the forms indicated by the one-dot chain line in
In a digital camera 10 according to a second embodiment, shutter blades 25 travel to block light arriving at an image sensor 22 at which light has arrived. Before the shutter blades 25 start to block the light arriving at the image sensor 22, it is detected that the shutter blades 25 moves from the movement start by a predetermined amount. Before the shutter blades 25 start blocking the light arriving at the image sensor 22, the reset scanning of the exposure amount of the image sensor 22 in the vertical upward direction is started at a reset timing corresponding to a necessary detection period Td from the movement start of the shutter blades 25 to the detection of the movement by the predetermined amount and the above-described timing correction amount ΔT. In the digital camera 10 according to the second embodiment, an exposure processing routine of
When the exposure processing routine of
When it is determined that the exposure period Tex is longer than the period threshold value Tref, the shutter blades 25 start traveling (hereinafter, also referred to as shutter travel). Thereafter, when the reset scanning of the image sensor 22 starts, it is determined that the exposure period Tex is not ensured. The reset timing of the reset scanning of the image sensor 22 and the travel start timing of the shutter blades 25 are set based on the exposure period Tex (step s520). The reset timing of the reset scanning of the image sensor 22 and the travel start timing of the shutter blades 25 may be set based on both the exposure period Tex and the timing correction amount ΔT. In the embodiment, the reset timing is set to a time at each position (each line) of the imaging surface 22a in a vertical direction when the photograph instruction is input, and the basic travel start timing is set to a time after the photograph instruction is input. In the embodiment, the reset timing and the travel start timing are set by determining a relation between the exposure period Tex and the reset timing and the travel start timing, from which the exposure period Tex can be obtained, in advance by an experiment or analysis, storing the relation as a timing set map in the ROM 44, and deriving the corresponding reset timing and the corresponding travel start timing from the timing set map when the exposure period Tex is given.
In this way, when the reset timing of the reset scanning of the image sensor 22 and the travel start timing of the shutter blades 25 are set, the reset scanning of the exposure amount of the image sensor 22 at the set reset timing starts and the shutter travel starts at the set travel start timing (step S530). Then, the exposure processing routine ends. The reset scanning is executed by outputting the control signals to the pulse generating circuit 30 and the vertical driving modulation circuit 32, respectively. The shutter travel starts by outputting a control signal for instructing the start of the travel to the shutter mechanism 23.
In this way, the read scanning is executed from the line in which the shutter travel ends, and then when the read scanning ends for all of the lines (step S590), the exposure processing routine ends. When the exposure processing routine ends, the AFE 28 converts a signal read from the image sensor 22 into a digital signal, the image processing device 60 executes predetermined image processing, and an image file of the photographed images is finally stored in the memory card 50. When the exposure period Tex is longer than the period threshold value Tref, the exposure of the image sensor 22 can be executed through the above process for the set exposure period Tex.
When the exposure period Tex is equal to or less than the period threshold value Tref in step S510, the shutter travel first starts (step S540) and the input of the detection signal transmitted from the position sensor 25a is waited (step S550). When the detection signal transmitted from the position sensor 25a is input, a necessary detection period Td is set as a period elapsed after the start of the shutter travel by the use of a period measured by a timer (not shown) (step S560). In the embodiment, a predetermined amount of movement of the shutter blades 25 to be detected by the position sensor 25a is a movement amount which is determined in advance by an experiment or the like and is necessary for grasping a change tendency in which the travel of the shutter blades 25 is delayed or advanced due to an individual difference or a temporal change of the shutter mechanism 23.
Subsequently, the reset timing of the image sensor 22 corresponding to the timing correction amount ΔT and the necessary detection period Td is set based on the exposure period Tex (step S570). In the embodiment, as in the setting of the correction amount ΔT1 in step S240 of the correction amount setting routine of
The period threshold value Tref can be used to determine whether the reset scanning may start after the detection timing of the position sensor 25a.
When the reset timing is set in this way, the reset scanning starts at the set rest timing (step S580) and the read scanning is finally executed (step S590). Then, the exposure processing routine ends.
In the digital camera 10 described above in the second embodiment, the shutter blades 25 travel to block the light arriving at the image sensor 22 at which light has arrived. Before the shutter blades 25 starts blocking the light arriving at the image sensor 22, it is detected that the shutter blades 25 moves from the movement start by the predetermined amount. Further, before the shutter blades 25 starts blocking the light arriving at the image sensor 22, the reset scanning of the exposure amount of the image sensor 22 in the vertical upward direction is started at the reset timing corresponding to the above-described timing correction amount ΔT and the necessary detection period Td in which the shutter blades 25 starts moving and the movement of the predetermined amount is detected. In this way, the reset scanning of the exposure amount of the image sensor 22 is started at the timing corresponding to the period in which the shutter blades 25 starts moving and the movement of the predetermined amount is detected. Therefore, when a variation occurs in the travel method due to the individual difference of the shutter mechanism 23 or the travel method is changed due to the temporal change of the shutter mechanism 23, the exposure amount of the image sensor 22 can be reset at the timing corresponding to the shutter travel method of each camera. Accordingly, it is possible to set the exposure period of the image sensor 22.
In the above-described second embodiment, as the period threshold value, the shutter speed (the exposure period) is used which is determined in advance within the period necessary for traveling the shutter blades 25 until the shutter blades 25 start moving and then travel by the predetermined amount up to the detection position of the position sensor 25a and the light incident on the image sensor 22 starts to be blocked. However, the period necessary for traveling the shutter blades 25 may be used. A period slightly shorter than the shutter speed (the exposure period) determined in this way may be used.
In the above-described second embodiment, when the exposure period Tex is equal to or less than the period threshold value Tref, the reset timing of the image sensor 22 is set to be earlier as the exposure period Tex is longer, whereas the reset timing of the image sensor 22 is set to be later as the updated timing correction amount ΔT is larger. That is, the reset timing is set to be earlier proportionally as the exposure period Tex is longer, whereas the reset timing is set to be later proportionally as the timing correction amount ΔT is larger. However, the reset timing may be set to be earlier stepwise as the exposure period Tex is longer, whereas the reset timing may be set to be later in stepwise (gradually) as the updated timing correction amount ΔT is larger.
In the above-described second embodiment, the position sensor 25a, which detects that the front end of the shutter blades 25 starts moving in the open state, travels upward by the predetermined amount, and reaches the detection position, is used as a sensor that detects the shutter blades 25 moving by the predetermined amount from the movement start. Instead, another sensor such as a sensor detecting an operation of an interlocking member interlocking with the movement of the shutter may be used. As the interlocking member, for example, the driving arm 26a or the driven arm 26b of the shutter mechanism 23, the shaft 26c, the shaft 26d, or the spring operating the driving arm 26a can be used. As the sensor, a rotation position sensor or the like may be used which detect the rotation position of the driving arm 26a or the driven arm 26b of the shutter mechanism 23, the shaft 26c, or the shaft 26d. Further, a sensor may be used which detects deformation of the spring or the like operating the driving arm 26a. The number of position sensors is not limited to one, but a plurality of position sensors may be used to control the reset scanning based on the detection result. In this case, a position sensor may be also installed at a position on the movement end side (upper side of the upper end of the imaging surface 22a) of the shutter blades 25 and the detection result of the position sensor may be reflected on the control of the reset scanning at the subsequent photograph time.
In the above-described second embodiment, the case has hitherto been described in which the photodiodes of the image sensor 22 are effective. However, all of the plurality of photodiodes may not be effective, but the photodiodes in a partial region (also referred to as an effective pixel region) may be effective. In this case, the photodiodes in a region other than the effective pixel region are covered to block light, are made not to read charge, or made to ignore the read charge or signal. Before the shutter blades 25 starts blocking the light arriving at the effective pixel region of the image sensor 22, it is detected that the shutter blades 25 move from the movement start by the predetermined amount. Further, before the shutter blades 25 starts blocking the light arriving at the effective pixel region of the image sensor 22, the reset scanning of the exposure amount of the image sensor 22 in the vertical upward direction may be started at the reset timing corresponding to the above-described timing correction amount ΔT and the necessary detection period Td in which the shutter blades 25 starts moving and the movement of the predetermined amount is detected. Furthermore, after the shutter blades 25 start blocking the light arriving at the photodiodes in a region other than the effective pixel region, the detection of the position sensor or the reset scanning may start.
In the above-described second embodiment, the contents described as other examples of the first embodiment may be, of course, applied as long as the contents is applicable even when the contents are other examples of the second embodiment. For example, the timing correction amount ΔT(y) set in the correction amount setting routine of
In the above-described two embodiments, the shutter mechanism 23 has a so-called transverse structure in which the shutter blades 25 move transversely in the vertical direction. However, when the shutter blades are moved in a predetermined on the front side of the image surface 22a of the image sensor 22, shutter mechanism may have a longitudinal structure in which the shutter blades move in a horizontal direction. Further, shutter blades with other structure may be used. For example, shutter blades travel in a rotation direction. In this case, the type or mounting position may be selected appropriately according to the structure of the shutter.
In the above-described two embodiments, the invention is applied to the digital camera 10, but may be applied to a shutter operation estimating method of the digital camera. Further, one or a plurality of the above-described two embodiments and modifications thereof may be combined appropriately.
Number | Date | Country | Kind |
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2011-048739 | Mar 2011 | JP | national |
2011-051445 | Mar 2011 | JP | national |