JP5708047B2 - Digital camera and exposure control method thereof - Google Patents

Description

  The present invention relates to a digital camera and an exposure control method thereof.

  Conventionally, as an image pickup apparatus applicable to this type of digital camera, an image pickup device that accumulates received light as an electric charge and a focal plane type shutter that travels so as to shield the image pickup device are used to shoot a still image. When adjusting the exposure time, it is proposed to control the start timing of charge accumulation scanning of the image sensor corresponding to the travel of the front curtain and the start timing of shutter travel corresponding to the travel of the rear curtain. (For example, refer to Patent Document 1).

  In addition, as an electronic camera that controls exposure using both an electronic shutter and a mechanical shutter, the exposure time caused by individual differences in mechanical delay from when the mechanical shutter closing operation is instructed until the actual closing operation is started. Proposal is also made for adjusting the displacement by adjusting the charge accumulation start timing and shutter drive start timing before and after the electronic shutter while evaluating the exposure amount using the integrated signal value corresponding to the brightness data for one screen. (For example, refer to Patent Document 2).

Japanese Patent No. 3988215 (Japanese Patent Laid-Open No. 11-41523) JP 11-234574 A

  However, in the latter camera described above, it is necessary to adjust the exposure time caused by the individual difference of the mechanical shutter for each individual, and it is necessary to photograph a fixed light source under a certain environment. A certain amount of time and equipment were required. In addition, when the mechanical shutter changes with time, the user may not be able to adjust the exposure time and may not be able to obtain a proper captured image.

  The main purpose of the digital camera and its exposure control method of the present invention is to make the time for exposing the image sensor more appropriate.

  The digital camera and its exposure control method of the present invention employ the following means in order to achieve the above-mentioned main object.

The digital camera of the present invention
An image sensor that generates an image signal based on the exposure amount;
A shutter that moves in a predetermined direction and blocks light hitting the image sensor;
A movement control unit that moves the shutter so that the light hitting the image sensor that is hit by light is blocked;
A movement detection unit that detects that the shutter has moved a predetermined amount from the start of movement before the shutter starts to block light hitting the image sensor;
Before the shutter starts to block the light hitting the image sensor, the exposure amount of the image sensor in the predetermined direction is determined at a timing corresponding to a detection required time from the start of movement of the shutter to detection by the movement detection unit. A reset control unit for starting reset scanning;
It is a summary to provide.

  In the digital camera of the present invention, the shutter that blocks the light hitting the image sensor is moved so that the light hitting the image sensor hitting the light is blocked. Then, before the shutter starts to block the light hitting the image sensor, it detects that the shutter has moved a predetermined amount from the start of movement, and further, the shutter starts moving before the shutter starts to block the light hitting the image sensor. The reset scanning in the predetermined direction of the exposure amount of the image sensor is started at a timing corresponding to the detection required time from when the movement is detected until the predetermined amount of movement is detected. That is, reset scanning of the exposure amount of the image sensor is started as the front curtain operation at a timing corresponding to the detection required time after the start of the shutter movement as the rear curtain operation. As described above, the reset scanning of the exposure amount of the image sensor is started at a timing corresponding to the time from the start of the movement of the shutter until the detection of the predetermined amount of movement. Therefore, the movement method varies depending on individual differences of the mechanism including the shutter. When there is an image sensor or when the movement method changes due to aging of the mechanism including the shutter, the exposure amount of the image sensor can be reset at a timing corresponding to the movement method of the shutter for each camera. As a result, the time for exposing the image sensor can be made more appropriate. Here, the reset scanning in the predetermined direction is performed by sequentially resetting the exposure amount of the image sensor in the predetermined direction. For the resetting of the exposure amount, the exposure amount is reset in a state where the exposure amount is not reset. Resetting and ending the resetting of the exposure amount in a state where the resetting of the exposure amount is continuously performed, the resetting being performed as a result of the reading process, and the reading process The reset is terminated as a result of the termination of. Note that when only a partial area (also referred to as an effective pixel area) of the image sensor circuit is effective, the image sensor referred to here means an image sensor circuit in the effective pixel area.

  In such a digital camera of the present invention, the reset control unit exposes the image sensor over the exposure time when the exposure time for exposing the image sensor is shorter than a predetermined time threshold. The reset scanning of the exposure amount of the image sensor in the predetermined direction is started at a timing according to the required detection time, and when the exposure time is longer than the time threshold, the image sensor is set to the exposure time. It is also possible to start reset scanning of the exposure amount of the image sensor in the predetermined direction regardless of the time required for detection so that the exposure is performed over the entire area. If the exposure time is relatively long, an attempt to start reset scanning of the exposure amount of the image sensor as the front curtain operation at a timing corresponding to the detection required time after the start of the shutter movement as the rear curtain operation, The exposure time may not be ensured. In addition, when the exposure time is relatively long, the influence of the individual difference of the mechanism including the shutter and the secular change on the actual exposure time is relatively small. For this reason, when the exposure time is longer than the time threshold, the image sensor is exposed by starting reset scanning of the exposure amount of the image sensor regardless of the detection time so that the image sensor is exposed over the exposure time. The time to do can be made more appropriate. In this case, the time threshold is a predetermined time within a time required for the movement of the shutter from the time when the shutter starts to move after the predetermined amount of movement until the light hitting the image sensor starts to be blocked. Can also be. In this case, when the exposure time is equal to the time threshold value, the reset control unit performs the image sensor at a timing according to the required detection time so that the image sensor is exposed over the exposure time. It is also possible to start a reset scan in the predetermined direction of the exposure amount of the image sensor, and the exposure amount of the image sensor regardless of the detection time so that the image sensor is exposed over the exposure time. The reset scanning in a predetermined direction may be started.

  In the digital camera according to the aspect of the invention in which the reset scanning of the exposure amount of the image sensor is started according to whether or not the exposure time is equal to or less than the time threshold, the reset control unit may be configured such that the exposure time is shorter than the time threshold. If the exposure time is longer than the predetermined exposure time, the detection time is faster than the exposure time shorter than the predetermined exposure time and the detection required time is longer than the predetermined required time. The reset scanning of the exposure amount of the image sensor in the predetermined direction may be started at a timing later than when the time is shorter than the predetermined required time. In other words, when the exposure time is shorter than the time threshold, the longer the exposure time, the faster the exposure time (for example, the longer the exposure time, the faster the proportional trend or stepwise (stepwise)) and the time required for detection. The reset scanning of the exposure amount of the image sensor in a predetermined direction may be started at a timing that tends to become slower as the time becomes longer (for example, the longer the time required for detection becomes a proportional trend or a stepwise (stepwise) time delay). It is. In this case, when the exposure time is longer than the time threshold, the reset control unit causes the movement control unit to start moving the shutter so that the image sensor is exposed for the exposure time. It is also possible to start reset scanning of the exposure amount of the image sensor in the predetermined direction at a reset timing set together with a power movement start timing.

  In the digital camera of the present invention, the movement detection unit moves the shutter to a detection position between the image sensor side end of the shutter in the open state and the shutter side end of the image sensor. It is also possible to detect reaching by.

An exposure control method for a digital camera of the present invention includes:
An exposure control method for a digital camera comprising: an image sensor that generates an image signal based on an exposure amount; and a shutter that moves in a predetermined direction and blocks light that hits the image sensor,
(A) moving the shutter so that light hitting the image sensor hit by light is blocked;
(B) detecting that the shutter has moved a predetermined amount from the start of movement before the shutter starts to block light hitting the image sensor;
(C) The exposure amount of the image sensor is determined at a timing corresponding to the detection time required from the start of the movement of the shutter to the detection in step (b) before the shutter starts to block the light hitting the image sensor. Starting reset scanning in a predetermined direction;
It is made to include.

  In the exposure control method of the digital camera according to the present invention, reset scanning of the exposure amount of the image sensor is started as the front curtain operation at a timing corresponding to the detection required time after the start of the shutter movement as the rear curtain operation. As described above, the reset scanning of the exposure amount of the image sensor is started at a timing corresponding to the time from the start of the movement of the shutter until the detection of the predetermined amount of movement. Therefore, the movement method varies depending on individual differences of the mechanism including the shutter. When there is an image sensor or when the movement method changes due to aging of the mechanism including the shutter, the exposure amount of the image sensor can be reset at a timing corresponding to the movement method of the shutter for each camera. As a result, the time for exposing the image sensor can be made more appropriate. Here, the reset scanning in the predetermined direction is performed by sequentially resetting the exposure amount of the image sensor in the predetermined direction. For the resetting of the exposure amount, the exposure amount is reset in a state where the exposure amount is not reset. It includes resetting and ending the resetting of the exposure amount while the resetting of the exposure amount is continuously performed. In this digital camera exposure control method, various aspects of the above-described digital camera may be adopted, and steps for realizing each function of the above-described digital camera may be added.

1 is a configuration diagram showing an outline of a configuration of a digital camera 10 according to an embodiment of the present invention. Explanatory drawing explaining a mode when the shutter mechanism 23 is seen from the incident direction of light. Explanatory drawing explaining a mode that the image sensor 22 is exposed. The flowchart which shows an example of an exposure process routine. Explanatory drawing which shows a mode when shutter driving | running | working is started after reset scanning start. Explanatory drawing which shows a mode when reset scanning is started after shutter driving | running | working start.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing an outline of the configuration of a digital camera 10 according to an embodiment of the present invention. FIG. 2 is an explanatory diagram for explaining a state when the shutter mechanism 23 is viewed from the incident direction of light. FIG. 3 is an explanatory diagram for explaining how the image sensor 22 is exposed as seen from the incident direction of light.

  The digital camera 10 according to the present embodiment inputs an electronic imaging unit 20 that outputs a signal for a captured image based on an image signal generated by photoelectrically converting a subject image, and a signal output from the electronic imaging unit 20. An image processing device 60 that performs predetermined image processing to generate image data and an image file of a captured image, and a display that displays image data input from the image processing device 60 on an EVF (Electronic View Finder) 72 or a liquid crystal monitor 74 A control device 70, various operation button groups 80 operated by a user, a memory card 50 capable of storing an image file generated by the image processing device 60, and a battery 55 for supplying power to each unit of the digital camera 10. And a main controller 40 for controlling the entire apparatus.

  The electronic imaging unit 20 includes a photographing lens 21 that is replaceably attached to the main body of the digital camera 10 via a lens mount (not shown), and an image sensor 22 that converts light input through the photographing lens 21 into an electrical signal by photoelectric conversion. A shutter mechanism 23 disposed between the photographic lens 21 and the image sensor 22, an analog front end (AFE) 28 that converts an electrical signal output from the image sensor 22 into a digital signal, and an image sensor. 22 and a pulse generation circuit 30 that outputs a clock signal to the image processing device 60.

  In addition to a plurality of lens groups configured by combining a convex lens and a concave lens, the photographing lens 21 includes information from a diaphragm mechanism 21 a that adjusts the amount of light incident on the image sensor 22, a distance measurement sensor (not shown), and the photographing lens 21. Is provided with an autofocus mechanism 21b for performing focusing based on the above. The aperture mechanism 21a and the autofocus mechanism 21b are controlled by driving the motors of the mechanisms by signals from the main controller 40.

  The image sensor 22 is configured as a CMOS image sensor including a plurality of photodiodes (not shown) arranged in a matrix and forming an imaging surface 22a (see FIG. 3) and a plurality of amplifiers (not shown) provided for each photodiode. Yes. A photodiode is a photoelectric conversion element that converts light when exposed to electric charge and accumulates it, and is provided for each pixel. This photodiode is designed to allow charges to escape to a substrate (not shown). The amplifier amplifies the charge accumulated in the photodiode so that it can be read out as a signal. In the image sensor 22, by using a color filter on the imaging surface 22a, a signal of any color of red (R), green (G), and blue (B) is output from each photodiode via an amplifier. It has become. A horizontal scanning clock (horizontal driving pulse) is supplied from the pulse generation circuit 30 to each photodiode of the image sensor 22, and the vertical scanning clock generated by the pulse generation circuit 30 and modulated in frequency by the vertical driving modulation circuit 32. (Vertical drive pulse) is supplied. In the embodiment, the clock supply by the pulse generation circuit 30 and the modulation of the clock frequency by the vertical drive modulation are controlled by a signal from the main controller 40, thereby resetting the exposure amount of the image sensor 22 that discharges the charge accumulated in the photodiode. The scanning of the image signal from the image sensor 22 generated based on the scanning and the exposure amount is executed with the adjustment of the scanning speed, and the reset scanning of the exposure amount of the image sensor 22 is performed as the operation of the electronic front curtain. It is functioning.

  The shutter mechanism 23 functions as a mechanical rear curtain for the electronic front curtain. As shown in FIG. 2, the shutter mechanism 23 is supported by the body of the digital camera 10 in front of the image sensor 22 in the optical axis direction to form a rectangular opening 24a. The base plate 24, a plurality of rectangular shutter blades 25, and a driving arm 26a and a driven arm 26b that are connected to one end of each shutter blade 25 and constitute a parallel link mechanism together with the shutter blade 25. The drive arm 26a and the driven arm 26b rotate around the shaft 26c and the shaft 26d at the end opposite to the end to which the shutter blade 25 is connected. The driven arm 26b is connected to the drive arm 26a by a connecting member (not shown), and rotates together with the drive arm 26a. The travel of the shutter blade 25 by the rotation of the drive arm 26a is performed as described below. When the shutter blades 25 are in the open state (the state shown in FIG. 2), the drive arm 26a is first held unrotatable by energization of an electromagnet (not shown), and further by releasing the locking member by driving a motor (not shown). If the energization of the electromagnet is released, it can be turned at any time. Subsequently, when the drive arm 26a starts to rotate by releasing the energization of the electromagnet, the shutter blade 25 travels from the vertically lower side of the digital camera 10 upward (in the direction of the thick arrow in FIG. 2) by the biasing force of a spring (not shown). . When the shutter blade 25 travels, the light incident on the image sensor 22 from the opening 24a of the base plate 24 is blocked, and the light is blocked. Thereafter, when the driving arm 26a is rotated again in the reverse direction by the driving of the motor, the shutter blade 25 returns to the original position (position in FIG. 2), and the driving arm 26a is further locked by the locking of the locking member by the driving of the motor. It cannot be turned.

  In this shutter mechanism 23, the shutter blade 25 travels so as to block a wider area than the opening 24a of the base plate 24. Therefore, as shown in FIG. A margin α1 is ensured between the tip) and the lower end of the opening 24a. In the light shielding state by the shutter blade 25, the tip of the shutter blade 25 is located above the upper end of the opening 24a by a margin α2. The digital camera 10 of the embodiment employs a mirrorless structure without a mirror on the light incident path of the image sensor 22, and can immediately irradiate the image sensor 22 with light when the shutter blades 25 are opened. It becomes. In FIG. 2, the position sensor 25 a is on the front side in the optical axis direction of the base plate 24, and the front end of the shutter blade 25 in the open state (the end of the shutter blade 25 on the image sensor 22 side) and the imaging surface 22 a of the image sensor 22. It is attached so that the position between the lower end (the end of the imaging surface 22a on the shutter blade 25 side) is the detection position, and before the tip of the shutter blade 25 starts light shielding at the lower end of the imaging surface 22a, It is detected that the tip of the shutter blade 25 starts moving from the open state, travels a predetermined amount upward, and reaches the detection position. As the position sensor 25a, for example, a non-contact sensor such as a proximity switch using an electric field or a magnetic field can be used. The meaning of the predetermined amount will be described again.

  Although not shown, the image processing apparatus 60 performs various types of well-known image processing in a digital camera, such as RGB pixel color interpolation processing, white balance processing, color reproduction processing, resizing processing, gamma correction processing, and image file generation processing. An image processing function block is provided. The image processing device 60 inputs a digital signal output from the electronic imaging unit 20 and also receives a clock signal from the pulse generation circuit 30 and executes image processing to generate a captured image, or the generated captured image Is converted into an image of a predetermined format and image information is added to generate an image file. In addition, the image processing device 60 sequentially inputs digital signals output from the electronic imaging unit 20 every predetermined time to generate an image for live view display.

  The display control device 70 displays a captured image generated by the image processing device 60 on the liquid crystal monitor 74, and sequentially displays live view display images generated by the image processing device 60 on the EVF 72 or the liquid crystal monitor 74. View display.

  The operation button group 80 is used for setting a shutter button 80a for outputting a shooting command for a subject to the main controller 40 when pressed by the user, and various setting values relating to shooting such as a shutter speed, an aperture value, and an exposure value. It includes a plurality of setting buttons 80b, a power button 80c for instructing power on / off, and the like.

  The main controller 40 is configured as a microprocessor centered on the CPU 42, and includes a ROM 44 for storing processing programs and various tables, a RAM 46 for temporarily storing data, a rewritable data, and data even when the power is turned off. And a flash memory 48 for holding the memory and an input / output port (not shown). The main controller 40 includes a detection signal (on / off signal) from the position sensor 25 a that detects that the shutter blade 25 has traveled a predetermined amount from the start of movement, various operation signals from the operation button group 80, Information, an image file read from the memory card 50, various images from the image processing device 60, and the like are input. Further, from the main controller 40, a drive signal to the photographing lens 21, a control signal to the shutter mechanism 23 for controlling a motor (not shown) or energizing the electromagnet, a control signal to the pulse generating circuit 30, A control signal for vertical drive modulation, an image file to be written to the memory card 50, an image processing command to the image processing device 60, a display control command to the display control device 70, and the like are output.

  In the digital camera 10 of the embodiment configured as described above, when various setting values such as the shutter speed are set and a shooting command is output according to the operation of the shutter button 80a, the exposure amount of the image sensor 22 is output by the main controller 40. Various controls for exposure, such as reset scanning of the shutter, travel control of the shutter blades 25, and readout scanning of the image signal from the image sensor 22, are finally performed by the image processing device 60 from the output signal of the electronic imaging unit 20. The generated image file is stored in the memory card 50. According to various controls for exposure on the imaging surface 22a of the image sensor 22, as shown in FIG. 3, first, the reset scanning position (line) is moved upward by the reset scanning of the image sensor 22, and the electronic front curtain is activated. Next, a position corresponding to the front end of the shutter blade 25 (hereinafter referred to as a shutter front end position) moves upward to block light by the mechanical rear curtain, and finally the reading scanning position (line) of the image sensor 22 moves upward. It will move sequentially. Accordingly, when attention is paid to one point of the image sensor 22, a shutter front end position corresponding to the front end of the mechanical rear curtain starts after the reset scanning position corresponding to the rear end of the electronic front curtain passes through that point and starts exposure. The time from passing through to being shielded corresponds to the shutter speed (exposure time). By adjusting this time, the time during which the subject image is irradiated onto the imaging surface 22a of the image sensor 22 is controlled. At this time, an area between the reset scanning position and the shutter tip position on the imaging surface 22a of the image sensor 22 (a hatched area in the figure) becomes the charge accumulation area of the image sensor 22, but this area is when the exposure time is short. It becomes a slit-like region. The reset scanning of the image sensor 22 with the exposure amount vertically upward is performed by sequentially resetting the exposure amount of the image sensor 22 vertically upward. In the embodiment, the resetting of the exposure amount is performed by resetting the exposure amount. The exposure amount may be reset instantaneously in a state where the exposure amount is not performed, or the exposure amount reset may be terminated in a state where the exposure amount reset is continuously performed. . Further, the exposure amount may be reset as a result of other processing such as readout scanning.

  Next, the operation of the digital camera 10 of this embodiment configured as described above, particularly the operation for exposure will be described. FIG. 4 is a flowchart showing an example of an exposure processing routine executed by the CPU 42 of the main controller 40. This routine is executed when the main controller 40 inputs a shooting command by operating the shutter button 80a. It is assumed that various setting values relating to shooting such as shutter speed, aperture value, and exposure value have been set before the main controller 40 inputs the shooting command.

  When the exposure processing routine is executed, the CPU 42 of the main controller 40 first inputs data necessary for the exposure processing such as the set exposure time Tex (step S100), and the input exposure time Tex is longer than the time threshold value Tref. The process which determines whether or not is performed (step S110). Here, as the exposure time Tex, a shutter speed set by the user operating the setting button 80b or set by an automatic exposure setting routine (not shown) can be input. Further, in the embodiment, the time threshold Tref is the shutter blade 25 from the timing when the shutter blade 25 travels a predetermined amount from the start of movement to the detection position of the position sensor 25a until the incident light to the image sensor 22 starts to be blocked. The time required to travel (the shortest considering individual differences and secular changes) is obtained in advance by experiments, etc., and the shutter speed (exposure time) determined in advance within the thus obtained time (for example, 1 / 4000th of a second) The one set as is used. When there are a plurality of such shutter speeds (exposure times), the larger one (for example, one of 4000 / second of 1 / 4000th and 1 / 8000th of a second) is used. The meaning of this time threshold value Tref will be described again.

  When it is determined that the exposure time Tex is longer than the time threshold value Tref, it is determined that the exposure time Tex cannot be secured if reset scanning of the image sensor 22 is started after the shutter blade 25 has started to travel (hereinafter also referred to as shutter travel). Based on the exposure time Tex, the reset timing of reset scanning of the image sensor 22 and the travel start timing of the shutter blades 25 are set (step S120). Here, in the embodiment, the reset timing is set as the time for each vertical position (for each line) of the imaging surface 22a after inputting the imaging command, and the travel start timing is set after the imaging command is input. It was supposed to be set as time. In this embodiment, the reset timing and the travel start timing are stored in the ROM 44 as a timing setting map by preliminarily determining the relationship between the exposure time Tex and the reset timing and the travel start timing at which the exposure time Tex is obtained by experiments and analysis. When the exposure time Tex is given, the corresponding reset timing and travel start timing are derived from the stored map and set.

  When the reset timing of the reset scanning of the image sensor 22 and the travel start timing of the shutter blades 25 are thus set, the reset scanning of the exposure amount of the image sensor 22 at the set reset timing is started and the shutter travel is performed at the set travel start timing. Start (step S130) and end the exposure processing routine. The reset scanning is performed by outputting control signals to the pulse generation circuit 30 and the vertical drive modulation circuit 32, respectively. The shutter travel is started by outputting a control signal instructing the shutter mechanism 23 to start travel. FIG. 5 shows an example of an exposure state when the shutter travel is started after the start of reset scanning when the exposure time Tex is longer than the time threshold value Tref. In the figure, the horizontal axis represents time, and the vertical axis represents the vertical position. The shutter front end position in the open state (rear curtain open position), the lower end of the imaging surface 22a, the upper end of the imaging surface 22a, and the shutter front end position in the light shielding state (rear curtain light shielding position) are shown on the vertical axis from the bottom. Yes. As shown in the figure, reset scanning is started at time t1 (see the alternate long and short dash line), and then when shutter start is instructed at time t2 (see solid line), the shutter tip position moves from the lower end to the upper end of the imaging surface 22a. In the meantime, the reset scanning is executed in accordance with the reset timing set so that the exposure time Tex is just secured with respect to the locus of the shutter tip position. Then, when reset scanning is completed for all lines at time t3, readout scanning of the image sensor 22 is started sequentially from the line where shutter travel is completed at time t4 (see the two-dot chain line).

  In this way, the readout scanning is performed from the line where the shutter travel is finished, and when the readout scanning is finished for all the lines (step S190), the exposure processing routine is finished. When the exposure processing routine is completed, the signal read from the image sensor 22 is digitally converted by the AFE 28, and predetermined image processing is performed by the image processing device 60. Finally, the image file of the photographed image is stored in the memory card 50. By such processing, when the exposure time Tex is longer than the time threshold value Tref, the image sensor 22 can be exposed with the set exposure time Tex.

  When it is determined in step S110 that the exposure time Tex is equal to or less than the time threshold value Tref, first, shutter travel is started (step S140), and a detection signal as an ON signal is input from the position sensor 25a (step S140). S150) When a detection signal as an ON signal is input from the position sensor 25a, the required detection time Td is set as an elapsed time since the start of shutter travel is instructed using a time measured by a timer (not shown) (step S150). S160). In the embodiment, the predetermined amount of movement of the shutter blades 25 to be detected by the position sensor 25a is a tendency of change such as delay or advance of the travel of the shutter blades 25 due to individual differences of the shutter mechanisms 23 or aging. As the amount of movement necessary for grasping the above, a predetermined amount is used.

  Subsequently, the reset timing of the image sensor 22 corresponding to the required detection time Td is set based on the exposure time Tex (step S170). In this embodiment, in this embodiment, the relationship between the exposure time Tex, the required detection time Td, and the reset timing at which this exposure time Tex is obtained is determined in advance by experiment and analysis and stored in the ROM 44 as a timing setting map. When the time Tex and the required detection time Td are given, the corresponding reset timing is derived from the stored map and set. In this timing setting map, the reset timing is set to an earlier timing as the exposure time Tex is longer, and is set to a later timing as the required detection time Td is longer (the detection timing is later).

  FIG. 6 shows an example of an exposure state when reset scanning is started after the start of shutter travel when the exposure time Tex is equal to or less than the time threshold value Tref. In the figure, with respect to the shutter tip position, a solid line indicates a locus when travel is delayed due to individual differences of the shutter mechanism 23 or aging (for example, individual differences or deterioration of electromagnets or springs not shown), and a broken line Indicates the trajectory of the reference example when there is no progress or delay in traveling in a basic state such as when the digital camera 10 is shipped. In the drawing, various times and times are shown by solid lines. For example, the start of shutter travel is instructed at time t5, and then reset scanning is started at time t7. As shown in the figure, when the exposure time Tex is equal to or less than the time threshold value Tref, the shutter mechanism 23 has a large proportion of the exposure time Tex of the delay time and advance time of the shutter travel due to individual differences and aging. The effect of 23 individual differences and secular changes on the actual exposure time is increased. Therefore, as the set exposure time Tex is longer, not only the earlier timing with respect to the locus of the shutter tip position is set as the reset timing, but the slower the detection timing of the shutter blade 25 at the detection position by the position sensor 25a, That is, the reset timing is adjusted to be delayed as the detection required time Td is longer. In the figure, as can be seen by comparing the reference example indicated by the broken line with the solid line, the time Td1 from the rear curtain opening position at time t5 when the shutter travel starts to the time t8 when the shutter tip position reaches the detection position, The time Td2 from the rear curtain opening position at time t5 to time t9 when the shutter tip position reaches the upper end of the imaging surface 22a tends to become longer as the required detection time Td from time t5 to time t6 is longer. In the embodiment, such a tendency is regarded as a shift in detection timing, and the exposure time is adjusted. Thus, the exact exposure time Tex can be ensured more reliably by setting the reset timing in accordance with the detection required time Td by the position sensor 25a. Note that setting the reset timing to a later timing as the detection required time Td is longer means that the reset timing is set to an earlier timing as the detection required time Td is shorter. Further, as can be seen from an example of the time threshold Tref shown in the drawing, when the exposure time Tex is longer than the time threshold Tref, the exposure time Tex cannot be ensured even if reset scanning is started after detection by the position sensor 25a. Therefore, it can be said that the time threshold value Tref is for determining whether or not the reset scanning may be started after the detection timing by the position sensor 25a.

  When the reset timing is set in this way, reset scanning at the set reset timing is started (step S180), and finally readout scanning is performed (step S190), and the exposure processing routine is ended.

  Here, the correspondence between the components of the present embodiment and the components of the present invention will be clarified. The image sensor 22 of the present embodiment corresponds to the “image sensor” of the present invention, the shutter blade 25 corresponds to the “shutter”, and the exposure mechanism of FIG. 4 controls the shutter mechanism 23 so that the shutter blade 25 starts to travel. The main controller 40 that executes the process of step S140 of the routine corresponds to a “movement control unit”, and a detection signal from the position sensor 25a and the position sensor 25a that detects that the shutter blade 25 has moved a predetermined amount from the start of movement. The main controller 40 that executes step S150 of the exposure processing routine in FIG. 4 corresponds to the “movement detection unit”, and reset scanning is performed by setting the reset timing according to the required detection time Td by the position sensor 25a. Steps S170 and S180 of the exposure processing routine of FIG. The main controller 40 to execute the process corresponds to "reset controller". In this embodiment, an example of the exposure control method for the digital camera of the present invention is also clarified by describing the operation of the digital camera.

  In the digital camera 10 according to the embodiment described above, the shutter blades 25 are caused to travel so that the light hitting the image sensor 22 hit by the light is blocked. Then, before the shutter blade 25 starts to block the light hitting the image sensor 22, it is detected that the shutter blade 25 has moved a predetermined amount from the start of movement, and further, the shutter blade 25 blocks the light hitting the image sensor 22. Before starting, reset scanning of the exposure amount of the image sensor 22 vertically upward is started at a reset timing corresponding to the detection required time Td from the start of the movement of the shutter blade 25 to the detection of a predetermined amount of movement. As described above, the reset scanning of the exposure amount of the image sensor 22 is started at a timing corresponding to the time from the start of the movement of the shutter blade 25 to the detection of the predetermined amount of movement. When there is a variation in the image, or when the travel method changes due to the secular change of the shutter mechanism 23, the exposure amount of the image sensor 22 can be reset at a timing according to the shutter travel method for each camera. The time for exposing 22 can be made more appropriate.

  It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

  In the above-described embodiment, as the time threshold Tref, the shutter blade 25 travels from a predetermined amount after the shutter blade 25 starts moving to the detection position of the position sensor 25a until light incident on the image sensor 22 begins to be blocked. The predetermined shutter speed (exposure time) is used within the time required for this, but the time required for the travel of the shutter blades 25 may be used as it is, or the shutter speed (exposure time) thus determined. A slightly shorter time may be used.

  In the above-described embodiment, when the exposure time Tex is equal to or less than the time threshold value Tref, the reset timing of the image sensor 22 is set to a timing that is earlier as the exposure time Tex is longer and is later as the required detection time Td is longer. In other words, the timing is set such that the longer the exposure time Tex is, the faster the proportional tendency is, and the longer the required detection time Td is, the slower the proportional trend is. However, the longer the exposure time Tex is, the stepwise (stepwise) is. It may be set to a timing that becomes earlier, or may be set to a timing that becomes slower stepwise (stepwise) as the required detection time Td becomes longer.

  In the above-described embodiment, as a sensor that detects that the shutter blade 25 has moved a predetermined amount from the start of movement, the tip of the shutter blade 25 starts moving from the open state, travels a predetermined amount upward, and reaches the detection position. However, instead of this, for example, a rotational position sensor that detects the rotational position of the drive arm 26a of the shutter mechanism 23 may be used. The position sensor is not limited to one, and reset scanning may be controlled based on the detection results using a plurality of position sensors. In this case, a position sensor is also provided at the position where the shutter blade 25 ends (upward from the upper end of the imaging surface 22a), and the detection result of the position sensor is reflected in the control of reset scanning at the next photographing. Also good.

  In the above-described embodiment, the shutter mechanism 23 is a so-called vertical run in which the shutter blades 25 run in the vertical direction. However, the shutter mechanism 23 has a predetermined direction so as to block a wider area than the image pickup surface 22a in front of the image pickup surface 22a of the image sensor 22. So long as the shutter blades travel in the horizontal direction, they may be so-called lateral running. Further, a shutter having another structure such as a shutter that travels in the rotation direction may be used. In this case, the type of the position sensor and the attachment position may be appropriately selected according to the shutter structure.

  In the embodiment described above, all the photodiodes of the image sensor 22 have been described as effective. However, it is not necessary to enable all of the plurality of photodiodes, and a photo of a partial region (also referred to as an effective pixel region) can be obtained. The diode may be effective. In this case, the photodiodes in the region excluding the effective pixel region are covered so as not to be exposed to light, the charges are not read out, or the read charges and signals are ignored. Then, before the shutter blade 25 starts to block the light hitting the effective pixel area of the image sensor 22, it is detected that the shutter blade 25 has moved a predetermined amount from the start of movement, and the shutter blade 25 further detects the image sensor 22. Before starting to block the light hitting the effective pixel region, the exposure amount of the image sensor 22 is increased vertically upward at a reset timing corresponding to the detection required time Td from the start of the movement of the shutter blade 25 to the detection of a predetermined amount of movement. A reset scan can be started. It should be noted that detection by the position sensor and reset scanning may be started after the shutter blade 25 starts to block light that strikes the photodiodes in the region other than the effective pixel region.

  In the above-described embodiment, the present invention is applied to the digital camera 10. However, an exposure control method for such a digital camera may be used.

  DESCRIPTION OF SYMBOLS 10 Digital camera, 20 Electronic imaging unit, 21 Shooting lens, 21a Aperture mechanism, 21b Autofocus mechanism, 22 Image sensor, 22a Imaging surface, 23 Shutter mechanism, 24 Ground plane, 24a Opening, 25 Shutter blade, 25a Position sensor, 26a Drive Arm, 26b Drive arm, 26c, 26d axis, 28 Analog front end (AFE), 30 Pulse generation circuit, 32 Vertical drive modulation circuit, 40 Main controller, 42 CPU, 44 ROM, 46 RAM, 48 Flash memory, 50 Memory card , 55 battery, 60 image processing device, 70 display control device, 72 EVF, 74 liquid crystal monitor, 80 operation button group, 80a shutter button, 80b setting button, 80c power button.

Claims (5)

An image sensor that generates an image signal based on the exposure amount;
A shutter that moves in a predetermined direction and blocks light hitting the image sensor;
A movement control unit that moves the shutter so that the light hitting the image sensor that is hit by light is blocked;
A first movement detection unit that detects that the shutter has moved a first amount from the start of movement before the shutter starts to block light hitting the image sensor;
A second movement detector for detecting that the shutter has moved a second amount from the start of movement after the shutter has finished blocking the light hitting the image sensor;
If the exposure time for the image sensor to be exposed is shorter than a predetermined time threshold, before the shutter begins to block light striking the image sensor so that the image sensor is exposed for the exposure time. The reset scanning of the exposure amount of the image sensor in the predetermined direction is started at a timing corresponding to a first detection required time from the start of movement of the shutter to detection by the first movement detection unit, and the exposure time is If longer than the time threshold, the image sensor is independent of the first detection time before the shutter begins to block light striking the image sensor so that the image sensor is exposed for the exposure time. A reset control unit for starting reset scanning of the exposure amount in the predetermined direction;
Equipped with a,
The reset control unit starts the reset scanning at a timing according to a second detection required time from the start of movement of the shutter at the time of previous photographing until detection by the second movement detection unit;
The time threshold is a predetermined time within a time required for the movement of the shutter from when the shutter starts to move after the first amount of movement until the light hitting the image sensor starts to be blocked.
Digital camera. The digital camera according to claim 1 ,
When the exposure time is shorter than the time threshold, the reset control unit is faster when the exposure time is longer than the predetermined exposure time than when the exposure time is shorter than the predetermined exposure time. and the first detection time required in the predetermined direction of the exposure amount of the image sensor at the timing when the first detection duration is longer than the predetermined duration is delayed compared to shorter than the predetermined duration To initiate a reset scan of
Digital camera. The digital camera according to claim 1 or 2 ,
The first movement detection unit detects that the shutter reaches a detection position between the end on the image sensor side of the shutter in the opened state and the end on the shutter side of the image sensor by movement. ,
Digital camera. A digital camera according to any one of claims 1 to 3,
  The shutter moves in the rotational direction;
  Digital camera. An exposure control method for a digital camera comprising: an image sensor that generates an image signal based on an exposure amount; and a shutter that moves in a predetermined direction and blocks light that hits the image sensor,
(A) moving the shutter so that light hitting the image sensor hit by light is blocked;
(B) detecting that the shutter has moved a first amount from the start of movement before the shutter begins to block light falling on the image sensor;
(C) When the exposure time for the image sensor to be exposed is shorter than a predetermined time threshold, the shutter blocks light that hits the image sensor so that the image sensor is exposed for the exposure time. Before starting to start, reset scanning of the exposure amount of the image sensor in the predetermined direction is started at a timing corresponding to the first detection required time from the start of the movement of the shutter to the detection by the step (b), and the exposure time Is longer than the time threshold, the shutter will begin to block light striking the image sensor so that the image sensor is exposed for the exposure time, regardless of the time required for the first detection. Starting reset scanning of the exposure amount of the image sensor in the predetermined direction;
(D) detecting that the shutter has moved a second amount from the start of movement after the shutter has stopped blocking the light hitting the image sensor;
Including
The step (c) starts the reset scanning at a timing according to a second detection required time from the start of movement of the shutter at the time of previous photographing until detection by the step (d),
The time threshold is a predetermined time within a time required for the movement of the shutter from when the shutter starts to move after the first amount of movement until the light hitting the image sensor starts to be blocked.
An exposure control method for a digital camera.

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