JP5220545B2 - Imaging element driving unit and imaging apparatus - Google Patents

Description

  The present invention relates to an image sensor driving unit that reduces power consumption for sweeping out unnecessary charges accumulated in a charge transfer path for transferring charges like a CCD.

  Various types of image sensors that generate an image signal corresponding to an optical image of a subject have been disclosed. Among various types of image pickup devices, CCD image pickup devices to which various improvements are added in terms of downsizing, good S / N ratio, high sensitivity, and the like are widely used.

  The CCD imaging device reads signal charges corresponding to the amount of light received from a plurality of pixels arranged on the light receiving surface to the vertical CCD for each pixel, transfers the signal charges read to the vertical CCD to the horizontal CCD, and then transfers them to the horizontal CCD. By transferring the signal charges to the output amplifier, pixel signals corresponding to the signal charges generated by the respective pixels are sequentially output.

  In the vertical CCD, charges generated by the vertical CCD itself due to leaked light, charges leaked when transferring signal charges exceeding the transfer capacity, charges leaking from the pixels other than at the time of reading, and the like may be accumulated. . Such a charge becomes a noise with respect to the signal charge, and must be eliminated in order to display an accurate image.

  Therefore, it is disclosed that before the signal charge generated by the pixel is read and transferred to the vertical CCD, the vertical CCD is subjected to high-speed sweeping to eliminate the charge accumulated in the vertical CCD (see Patent Document 1). .

On the other hand, for high-speed sweeping of the vertical CCD, it is necessary to increase the frequency of the drive signal for driving the vertical CCD. In order to increase the frequency of the drive signal, the problem is that the power consumption increases.
JP-A-4-356879

  Accordingly, an object of the present invention is to provide an image sensor driving unit that reduces power consumption for sweeping out charges accumulated in a charge transfer path such as a CCD.

  The image sensor driving unit of the present invention includes a plurality of pixels that generate signal charges corresponding to the amount of received light, and a first charge that transfers signal charges read from the pixels at a speed corresponding to the frequency of the first transfer signal. An image sensor driving unit for driving an image sensor having a transfer path and a second charge transfer path for transferring a signal charge transferred from the first charge transfer path by a second transfer signal, and transferring the signal charge A normal transfer signal, which is a first transfer signal to be transferred, or a transfer signal for sweeping out charge remaining in the first charge transfer path, and a sweep signal having a frequency higher than that of the normal transfer signal and a second transfer signal. A signal generation unit that generates and transmits to the image sensor, and a second so that the sweep signal and the cumulative generation period are shorter than the sweep period in the signal generation unit during the sweep period for sweeping out the charge remaining in the first charge transfer path. Transfer signal It is characterized by comprising a first control unit to generate.

  Furthermore, a detection unit that detects an exposure time to the image sensor is provided, and the first control unit decreases the cumulative generation period of the second transfer signal during the sweeping period as the exposure time detected by the detection unit becomes shorter. Is preferred.

  Further, the first control unit stops generating the second transfer signal during the sweeping period when the exposure time is less than the threshold value, and outputs the second transfer signal during the sweeping period when the exposure time exceeds the threshold value. Preferably, it is generated.

  Further, it is preferable that the first controller stops the generation of the second transfer signal during the sweeping period.

  A second control unit configured to transfer the signal charge generated by exposing the optical image to the image sensor to each divided transfer timing obtained by dividing the transfer timing of the signal charge by the first and second charge transfer paths; The first control unit causes the signal generation unit to generate the second transfer signal so that the sweep signal and the cumulative generation period are shorter than the sweep period during the sweep period immediately before the first divided transfer time. It is preferable to cause the signal generator to execute generation of the sweep signal and stop generation of the second transfer signal during the sweep period immediately before the divided transfer timing.

  The imaging device of the present invention includes a plurality of pixels that generate signal charges according to the amount of received light, and a first charge transfer path that transfers signal charges read from the pixels at a speed according to the frequency of the first transfer signal. A first transfer signal for transferring the signal charge, and an image pickup device having a second charge transfer path for transferring the signal charge transferred from the first charge transfer path by the second transfer signal A signal generation unit for generating a transfer signal or a second transfer signal, which is a transfer signal for sweeping out the charge remaining in the first charge transfer path and having a frequency higher than that of the normal transfer signal, and transmits the second transfer signal to the image sensor And a first control unit that causes the signal generation unit to generate the second transfer signal so that the sweep signal and the cumulative generation period are shorter than the sweep period during the sweep period for sweeping out the charge remaining in the first charge transfer path. Characterized by comprising There.

  According to the present invention, it is possible to reduce power consumption when sweeping out charges accumulated in a charge transfer path such as a CCD.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram schematically showing an internal configuration of a single-lens reflex camera having an image sensor driving unit to which an embodiment of the present invention is applied.

  The single-lens reflex camera 10 includes an imaging optical system 11, an image sensor 30, a timing generator (TG) 12, a digital signal processor (DSP) 13, a CPU 14, and the like.

  The photographing optical system 11 is formed by a plurality of lenses including a focus lens (not shown) and a variable power lens (not shown). An image sensor 30 is arranged on the optical axis so as to be perpendicular to the optical axis of the photographing optical system 11. The photographing optical system 11 forms an optical image of the subject on the light receiving surface of the image sensor 30.

  A diaphragm 16, a mirror 17, and a shutter 18 are disposed between the photographing optical system 11 and the image sensor 30. By adjusting the aperture ratio of the diaphragm 16, the amount of light incident on the image sensor 30 is adjusted. At the time of shooting standby, the mirror 17 is closed, and the optical image of the subject is reflected toward the pentaprism 19 and transmitted to a viewfinder (not shown). When imaging is performed, the mirror 17 opens upward, and the optical image of the subject reaches the shutter 18. By opening and closing the shutter 18, the shielding and reaching of the optical image to the image sensor 30 are switched.

  The diaphragm 16, the mirror 17, and the shutter 18 are driven by an optical system driving circuit 20. The driving of each part by the optical system driving circuit 20 is controlled by the CPU 14. The single lens reflex camera 10 is provided with a photometric sensor (not shown). The amount of light around the subject is detected by the photometric sensor. Based on the detected light amount, exposure adjustment such as aperture ratio adjustment of the diaphragm 16, adjustment of the opening / closing timing of the mirror 17, and adjustment of the exposure time Tv is performed.

  The image pickup device 30 is driven based on the vertical transfer pulse ΦV generated by the TG 12, and an image signal corresponding to the optical image is generated. The driving of the image sensor 30 by the TG 12 is controlled by the DSP 13. The generated image signal is transmitted to the DSP 13 via the AFE 21.

  In the AFE 21, the image signal is subjected to CDS processing, AGC processing, and A / D conversion processing. In the DSP 13, predetermined signal processing is performed on the image signal. The image signal that has undergone predetermined signal processing is stored in the memory 22. Alternatively, the image is transmitted to the LCD 23 and the captured image is displayed on the LCD 23.

  The DSP 13 is connected to the CPU 14. The DSP 13 controls processing such as driving of the TG 12, signal processing for the image signal, and storage of the image signal based on data received from the CPU 14.

  As described above, the optical system driving circuit 20 and the DSP 13 are controlled by the CPU 14. The operation of each part of the single-lens reflex camera 10 is also controlled by the CPU 14. The CPU 14 is connected to an input unit 24 including a release button (not shown), a power button (not shown), a multi-function cross key (not shown), and the like. The CPU 14 controls each part of the single-lens reflex camera 10 according to various command inputs to the input unit 24 by the user.

  As described above, the adjustment of the aperture ratio of the diaphragm 16 and the adjustment of the exposure time Tv are controlled by the CPU 14 based on the light amount, but the exposure adjustment is performed by a command input to the input unit 24 by the user. Can also be set.

  Next, the configuration of the image sensor 30 and the operation of the image sensor 30 when performing imaging will be described in more detail.

  The image pickup device 30 is a CCD image pickup device, and includes a pixel 31, a vertical CCD 32, a horizontal CCD 33, an output amplifier 34, and the like as shown in FIG.

  A plurality of pixels 31 are two-dimensionally arranged on the light receiving surface of the image sensor 30. A vertical CCD 32 is arranged in each row in which the pixels 31 are arranged. Each pixel 31 is connected to an adjacent vertical CCD 32. Below the vertical CCD 32, a horizontal CCD 33 extending in the row direction of the pixels is provided. The all vertical CCDs 32 are connected to the horizontal CCD 33. An output amplifier 34 is connected to one end of the horizontal CCD 33.

  In each pixel 31, signal charge corresponding to the amount of received light is generated and accumulated. An electronic shutter terminal 35sub is connected to a substrate (not shown) on which the pixels 31 are arranged. By inputting the electronic shutter pulse ΦSUB to the electronic shutter terminal 35sub, the charges accumulated in all the pixels 31 are swept out and reset.

  A sensor gate (not shown) is arranged between the pixel 31 and the vertical CCD 32. A sensor gate (SG) terminal 35sg is connected to the sensor gate. When the SG pulse ΦSG is input to the SG terminal 35 sg, the signal charge accumulated in the pixel 31 is read out to the vertical CCD 32.

  As shown in FIG. 3, first to fourth electrodes 36 a to 36 d are arranged on the vertical CCD 32 so as to repeat in order along the column direction. By inputting a vertical transfer pulse ΦV whose phase is shifted to the first to fourth electrodes 36 a to 36 d, charges accumulated in the vertical CCD 32 are transferred to the horizontal CCD 33. The first to fourth electrodes 36a to 36d are connected to the first to fourth vertical transfer terminals 35v1 to 35v4 (see FIG. 2), respectively.

  The charge transfer rate in the vertical CCD 32 changes according to the frequency of the vertical transfer pulse ΦV. The transfer rate increases as the frequency increases, and the transfer rate decreases as the frequency decreases.

  Similar to the vertical CCD 32, the horizontal CCD 33 has fifth and sixth electrodes (not shown) arranged in order in the row direction. By inputting the horizontal transfer pulse ΦH whose phase is shifted to the fifth and sixth electrodes, the charge transferred to the horizontal CCD 33 is transferred to the output amplifier 34. The fifth and sixth electrodes are connected to the first and second horizontal transfer terminals 35h1 and 35h2, respectively.

  The electronic shutter pulse ΦSUB, the sensor gate pulse ΦSG, the vertical transfer pulse ΦV, and the horizontal transfer pulse ΦH are generated by the TG 12 and input to each terminal.

  The output amplifier 34 has a capacitor, converts the transferred signal charge into a signal voltage and outputs the signal voltage.

  Next, the release control that is started when the release button is fully pressed will be described with reference to FIGS. FIG. 4 is a timing chart for explaining the release control when the exposure time Tv is set short. FIG. 5 is a timing chart for explaining the release control when the exposure time Tv is set to be long.

  When the release button is fully pressed, the CPU 14 starts release control, which is sequence control. At timing t1 after detection of full release button release, the mirror 17 is opened upward.

  At the next timing t2, the input of the vertical transfer pulse ΦV which is the frequency for signal charge transfer to the first to fourth vertical transfer terminals 35v1 to 35v4, and the horizontal to the first and second horizontal transfer terminals 35h1 and 35h2. The input of the transfer pulse ΦH and the input of the electronic shutter pulse ΦSUB to the electronic shutter terminal 35sub are started, and the charges accumulated in the vertical CCD 32, the horizontal CCD 33, and the pixel 31 are swept out.

  At timing t3, the input of the electronic shutter pulse ΦSUB is stopped, and signal charges can be accumulated in the pixels 31. At timing t3, the shutter 18 is opened, and exposure of the optical image to the image sensor 30 is started. At timing t4 after the set exposure time Tv has elapsed, the shutter 18 is closed, and the exposure of the optical image onto the image sensor 30 is completed.

  The image sensor 30 is driven so as to perform an interlaced scan, and signal charges generated by one exposure are read out in two field periods of an even field and an odd field. In the even field, which is the first field period, the signal charges generated by the pixels 31 in the even rows are read from the image sensor 30. In the odd field, which is the next field period, the signal charges generated by the pixels 31 in the odd rows are read from the image sensor 30.

  Prior to the reading of the signal charge in the even field, a fast sweep of the vertical CCD 32 is performed. At the same timing t4 as the completion of exposure, the frequency of the vertical transfer pulse ΦV is switched to a high-speed sweeping frequency larger than the frequency for signal charge transfer, and the charge accumulated in the vertical CCD 32 is swept out at a high speed.

  The charge can be stored at any position of the vertical CCD 32. By transferring charges accumulated at respective positions from the position closest to the horizontal CCD 33 to the position farthest from the horizontal CCD 33 in order, one high-speed sweep of the vertical CCD 32 is executed. Before the signal charge reading in the even field, high-speed sweep is performed twice.

  Note that the drive pattern of the horizontal CCD 33 during high-speed sweeping of the vertical CCD 32 is changed by the set exposure time Tv. In order to determine the drive pattern of the horizontal CCD 32, a threshold value α to be compared with the exposure time Tv is determined. The exposure time Tv is compared with the threshold value α by the DSP 13. The threshold value α is stored in a ROM (not shown) connected to the DSP 13.

  When the set exposure time Tv is less than the threshold value α, the generation and transmission of the horizontal transfer pulse ΦH in the TG 12 is stopped during the high-speed sweep execution period of the vertical CCD 32, and the charge transfer in the horizontal CCD 33 is stopped ( (See FIG. 4). On the other hand, when the set exposure time Tv is equal to or greater than the threshold value α, the generation of the horizontal transfer pulse ΦH is not stopped and the transfer of charges in the horizontal CCD 33 is continued (see FIG. 5).

  At timing t5 when the second high-speed sweep ends, the frequency of the vertical transfer pulse ΦV is returned to the signal charge transfer frequency. By returning the frequency to the frequency for signal charge transfer, the signal charge can be transferred to the horizontal CCD 33 without causing a transfer failure. When the horizontal transfer pulse ΦH is stopped, generation of the horizontal transfer pulse ΦH and transmission to the image sensor 30 are resumed at timing t5.

  After the high-speed sweeping of the vertical CCD 32 is completed, the sensor gate pulse ΦSG is input to the sensor gate terminal 35sg (see timing t6). The vertical transfer pulse ΦV having a pattern for reading the signal charges of the pixels 31 in the even-numbered rows to the vertical CCD 32 is input to the first to fourth electrodes 35v1 to 35v4. With the input of the sensor gate pulse ΦSG and the vertical transfer pulse ΦV, the signal charges generated and accumulated in the pixels 31 in the even rows between the timing t3 and the timing t4 are read out to the vertical CCD 32.

  When the transfer of the signal charges of all the pixels 31 in the even-numbered rows by the vertical CCD 32 and the horizontal CCD 33 is completed, the reading in the even-numbered field is finished. After the reading of the even field is completed, the high-speed sweeping of the vertical CCD 32 and the reading of the signal charges of the pixels 31 in the odd rows are executed.

  After the reading in the even field is completed (timing t7), the frequency of the vertical transfer pulse ΦV is switched to the high-speed sweeping frequency, and the high-speed sweeping of the vertical CCD 32 is executed (timing t7 to timing t8). Further, unlike before reading out signal charges in the even field, high-speed sweeping is performed only once before reading out signal charges in the odd field.

  At the same timing t7, generation and transmission of the horizontal transfer pulse ΦH are stopped, and charge transfer in the horizontal CCD 33 is stopped. Unlike the high-speed sweep before reading in the even field, the amount of charge accumulated in the vertical CCD 32 is small, so that the charge transfer in the horizontal CCD 33 can be stopped regardless of the length of the exposure time Tv.

  At timing t8, which is the end of one high-speed sweep, the frequency of the vertical transfer pulse ΦV is returned to the signal charge transfer frequency, and the high-speed sweep is terminated. Further, generation and transmission of the horizontal transfer pulse ΦH are resumed at timing t8.

  After the high-speed sweeping of the vertical CCD 32 is completed, the sensor gate pulse ΦSG is input to the sensor gate terminal 35sg (see timing t9). The vertical transfer pulse ΦV having a pattern for reading the signal charges of the odd-numbered pixels 31 to the vertical CCD 32 is input to the first to fourth electrodes 35v1 to 35v4. By inputting the sensor gate pulse ΦSG and the vertical transfer pulse ΦV, the signal charges generated and accumulated in the pixels 31 in the odd-numbered rows during the timing t3 to the timing t4 are read out to the vertical CCD 32.

  When the transfer of the signal charges of all the pixels 31 in the odd-numbered rows by the vertical CCD 32 and the horizontal CCD 33 is completed (timing t10), the reading in the odd-numbered field is also finished, and the generation and reading of the image signal of one frame, that is, the first imaging is finished. . When the first imaging is completed, the input of the electronic shutter pulse ΦSUB to the electronic shutter terminal 35sub is resumed, and the electric charge accumulated in the pixels 31 is swept until the next release control is started.

  Next, the release control process executed by the CPU 14 in the first embodiment will be described with reference to the flowchart of FIG. The release control process is started when the CPU 14 detects that the release button is fully pressed.

  In step S100, the set exposure time Tv is detected. When the exposure time Tv is detected, the process proceeds to step S101 and normal transfer is started. In normal transfer, the CPU 14 controls the optical system drive circuit 20 so as to transmit a vertical transfer pulse ΦV, a horizontal transfer pulse ΦH, and an electronic shutter pulse ΦSUB, which are frequencies for signal charge transfer, to the image sensor 30. After the normal transfer is started, the process proceeds to step S102.

  In step S102, exposure processing is started. The mirror 17 is opened upward, the shutter 18 is opened for the set exposure time Tv, and the generation of the electronic shutter pulse ΦSUB is stopped to complete the exposure process. After the exposure process is completed, the process proceeds to step S103.

  In step S103, high-speed sweeping of the vertical CCD 32 is started. After execution of high-speed sweeping starts, the process proceeds to step S104. In step S104, it is determined whether or not the exposure time Tv detected in step S100 is less than the threshold value α. If the exposure time Tv is less than the threshold value α, the process proceeds to step S105. If the exposure time Tv is greater than or equal to the threshold value α, the process proceeds to step S107.

  In step S105, the generation of the horizontal transfer pulse ΦH is stopped, and the charge transfer in the horizontal CCD 33 is stopped. When the charge transfer is stopped and the high-speed sweeping of the vertical CCD 32 is completed, the process proceeds to step S106.

  In step S106, normal transfer is resumed to the vertical CCD 32 and the horizontal CCD 33. That is, the CPU 14 controls the TG 12 so as to transmit the vertical transfer pulse ΦV and the horizontal transfer pulse ΦH, which are frequencies for signal charge transfer, to the image sensor 30. After the normal transfer of the vertical CCD 32 and the horizontal CCD 33 is resumed, the process proceeds to step S108.

  In step S107, normal transfer of the vertical CCD 32 is resumed after the high-speed sweep of the vertical CCD 32 is completed. That is, the CPU 14 causes the DSP 13 to control the TG 12 so that the frequency of the vertical transfer pulse ΦV is returned to the frequency for signal charge transfer. After the normal transfer of the vertical CCD 32 is resumed, the process proceeds to step S108.

  In step S108, the signal charge transfer process in the even field is executed. As described above, the signal charges read from the pixels 31 arranged in the even-numbered rows are transferred to the output amplifier 34 via the vertical CCD 32 and the horizontal CCD 33. When the transfer of signal charges from all the pixels 31 in the even-numbered rows is completed, the process proceeds to step S109.

  In step S109, execution of high-speed sweeping of the vertical CCD 32 is started. Further, the transfer of charges in the horizontal CCD 33 is stopped. After completion of one high-speed sweep, the process proceeds to step S110.

  In step S110, the normal transfer is resumed to the vertical CCD 32 and the horizontal CCD 33 as in step S106. After the normal transfer is resumed, the process proceeds to step S111. In step S111, a signal charge transfer process in the odd field is executed. When the transfer of signal charges from all the pixels 31 in the odd-numbered rows is completed, the release control process is terminated.

  According to the image sensor driving unit to which the first embodiment as described above is applied, since the charge transfer of the horizontal CCD 33 is stopped during the high-speed sweep of the vertical CCD 32, it is possible to reduce power consumption. .

  Note that charges are accumulated in the horizontal CCD 33 by high-speed sweeping of the vertical CCD 32. However, since the charge transfer in the horizontal CCD 33 is resumed after the high-speed sweep is completed and before the signal charge is read from the pixel 31, the charge accumulated in the horizontal CCD 33 can be swept out.

  Further, since the transfer of the horizontal CCD 33 during the high-speed sweeping of the vertical CCD 32 is switched between the stop and the continuation according to the length of the exposure time Tv, the noise removal accuracy is improved. Hereinafter, the effect of switching between stopping and continuing transfer in the horizontal CCD 33 during high-speed sweeping will be described in more detail.

  In order to increase the speed of the imaging operation, it is desirable that the time from the completion of the high-speed sweep to the signal charge readout from the pixel 31 is kept constant. Therefore, the transfer period of charges accumulated in the horizontal CCD 33 after high-speed sweeping is also set to a certain period.

  If the charge accumulated in the horizontal CCD 33 is not sufficiently swept after the high-speed sweep of the vertical CCD 32, the charge remains in the horizontal CCD 33 and may be mixed as noise in the subsequent signal charge to be read. As the exposure time increases, the amount of charge generated in the vertical CCD 32 increases. Therefore, the amount of charge transferred to the horizontal CCD 33 increases as the exposure time increases. Therefore, when the exposure time is equal to or greater than the threshold value α, the noise removal accuracy is improved by continuing the transfer in the horizontal CCD 33 without stopping.

  Next, an image sensor driving unit to which the second embodiment of the present invention is applied will be described. The second embodiment is different from the first embodiment in the method of driving the horizontal CCD according to the exposure time. Hereinafter, the second embodiment will be described with a focus on portions different from the first embodiment. In addition, the same code | symbol is attached | subjected to the site | part which has the same function.

  In the second embodiment, the configuration other than the release control executed by the CPU is the same as that of the first embodiment. The release control started when the release button is fully pressed will be described with reference to FIGS. FIG. 7 is a timing chart for explaining the release control when the exposure time Tv is set to be long. FIG. 5 is a timing chart for explaining the release control when the exposure time Tv is set short.

  From the time when the release button is fully pressed until the exposure to the image sensor 30 is completed (timing t1 to timing t4), the same control as in the first embodiment is executed. Similar to the first embodiment, the high-speed sweep of the vertical CCD 32 is performed twice after the exposure is completed (timing t4 to timing t5).

  The drive pattern of the horizontal CCD 33 during high-speed sweeping of the vertical CCD 32 is changed according to the set exposure time Tv.

  When the set exposure time is less than the first threshold value α1, the generation and transmission of the horizontal transfer pulse ΦH are stopped during the high-speed sweep period, and the charge transfer in the horizontal CCD 33 is stopped. If the set exposure time is equal to or longer than the second threshold value α2 (> α1), the horizontal transfer pulse ΦH is not stopped, and the charges are continuously transferred in the horizontal CCD 33 after the exposure is completed. .

  When the set exposure time is not less than the first threshold value α1 and less than the second threshold value α2, the generation and transmission of the horizontal transfer pulse ΦH are stopped when the high-speed sweep is started. However, unlike the case where it is less than the first threshold value α1, the generation and transmission of the horizontal transfer pulse ΦH is started before the high-speed sweep is completed, and the charge transfer in the horizontal CCD 33 is resumed.

  As the exposure time becomes shorter in the range of the first threshold value α1 to the second threshold value α2, the resumption timing of charge transfer in the horizontal CCD 33 is delayed. Therefore, the transfer stop period in the horizontal CCD 33 is controlled to be shorter as the exposure time is longer.

  For example, as shown in FIG. 7, when the set exposure time Tv is P1, transfer of the horizontal CCD 33 is resumed after elapse of t1 ′ (ms) from the completion of exposure (timing t4), while FIG. Thus, when the set exposure time Tv is P2 shorter than P1, the transfer of the horizontal CCD 33 is resumed after t2 ′ (ms) further delayed from t1 ′ (ms).

  When the high-speed sweeping of the vertical CCD 32 is completed twice, the signal charges of the pixels 31 in the even-numbered rows are read and transferred as in the first embodiment (timing t6, timing t7). In the subsequent timing t7 to timing t10, the same control as in the first embodiment is executed.

  Next, release control processing executed by the CPU 14 in the second embodiment will be described with reference to the flowchart of FIG. The release control process is started when the CPU 14 detects that the release button is fully pressed.

  In step S200 to step S203, the same processing as in step S100 to step S103 in the first embodiment is executed. When execution of high-speed sweeping of the vertical CCD 32 is started in step S203, the process proceeds to step S204.

  In step S204, it is determined whether or not the exposure time Tv detected in step S200 is greater than or equal to the first threshold value α1. If the exposure time Tv is greater than or equal to the first threshold value α1, the process proceeds to step S205. If the exposure time Tv is less than the first threshold value α1, the process proceeds to step S209.

  In step S205, the generation of the horizontal transfer pulse ΦH is stopped, and the charge transfer in the horizontal CCD 33 is stopped. After stopping the transfer, the process proceeds to step 206, where it is determined whether or not the exposure time Tv detected in step S200 is equal to or greater than the second threshold value α2. If the exposure time Tv is greater than or equal to the second threshold value α2, the process proceeds to step S207. If the exposure time Tv is less than the second threshold value α2, the process proceeds to step S208.

  In step S207, normal transfer is resumed to the vertical CCD 32 and the horizontal CCD 33 after the high-speed sweep of the vertical CCD 32 is completed. After the normal transfer of the vertical CCD 32 and the horizontal CCD 33 is resumed, the process proceeds to step S210.

  In step S208, the normal transfer is restarted by the horizontal CCD 33 after the elapsed time determined according to the exposure time detected in step S200. After the normal transfer of the horizontal CCD 33 is resumed, the process proceeds to step S209.

  As described above, when the exposure time Tv is less than the first threshold value α1 in step S204 or when the normal transfer of the horizontal CCD 33 is resumed in step S208, the vertical CCD 32 is set after the high-speed sweep of the vertical CCD 32 is completed. Resume normal transfer. After the normal transfer of the vertical CCD 32 is resumed, the process proceeds to step S210.

  In subsequent steps S210 to S213, the same processing as in steps S108 to S111 in the first embodiment is executed to transfer the signal charges of the pixels 31 in the even rows, the high-speed sweep of the vertical CCDs 32, and the pixels in the odd rows. 31 signal charges are transferred. When the transfer of signal charges from all the pixels 31 in the odd-numbered rows is completed, the release control process is terminated.

  According to the image sensor driving unit to which the second embodiment as described above is applied, since the charge transfer of the horizontal CCD 33 is stopped during the high-speed sweep of the vertical CCD 32, it is possible to reduce power consumption. .

  In addition, according to the second embodiment, the resumption timing of the charge transfer of the horizontal CCD 33 during the high-speed sweeping of the vertical CCD 32 is adjusted according to the exposure time Tv, so that the power consumption can be further reduced as compared with the first embodiment. It is possible to reduce.

  When the exposure time is equal to or greater than the threshold value α in the first embodiment and when the exposure time is equal to or greater than the first threshold value α1 in the second embodiment, Although the structure is such that the charge transfer of the CCD is stopped, the power consumption can be reduced even if the charge transfer of the horizontal CCD is stopped during a part of the high-speed sweep.

  In the first and second embodiments, the drive pattern of the horizontal CCD is changed during high-speed sweeping of the vertical CCD according to the exposure time. For example, the charge transfer time of the horizontal CCD may be reduced or the charge transfer may be stopped during high-speed sweeping regardless of the exposure time. It is possible to reduce power consumption without changing the driving pattern of the horizontal CCD.

  In the second embodiment, the horizontal CCD transfer restart timing during the high-speed sweeping period of the vertical CCD is delayed as the exposure time becomes shorter. However, the horizontal CCD transfer during the high-speed sweeping period becomes shorter as the exposure time becomes shorter. The structure which shortens time may be sufficient. For example, even if the cumulative transfer time is shortened by reducing the generation frequency of the horizontal transfer pulse ΦH, the same effect as in the second embodiment can be obtained.

  In the first and second embodiments, the first to fourth electrodes 36a to 36d are arranged in the vertical CCD 32 so as to be repeated in order, but the number of electrodes is not limited to four. . Further, although the fifth and sixth electrodes are arranged on the horizontal CCD 33 so as to be repeated in order, the number of electrodes is not limited to two.

  In the first and second embodiments, the image pickup device 30 is configured to transfer the signal charge to the output amplifier 34 by two-time reading of the interlaced scan. It may be read separately. Furthermore, a configuration in which reading is performed once by progressive scan may be employed.

  In the first and second embodiments, the image pickup device 30 is a CCD image pickup device, but can be applied to other charge transfer type image pickup devices.

It is a block diagram which shows roughly the internal structure of the single-lens reflex camera which has an image pick-up element drive unit to which the 1st, 2nd embodiment of this invention is applied. It is a schematic block diagram of an image pick-up element. FIG. 6 is a layout view of first to fourth electrodes. 6 is a timing chart showing the timing of operations performed in the image sensor during release control when the exposure time is less than a threshold value in the first embodiment. 6 is a timing chart illustrating the timing of operations performed in the image sensor during release control when the exposure time is equal to or greater than a threshold value in the first embodiment. It is a flowchart which shows the process of release control in 1st Embodiment. 10 is a timing chart illustrating the timing of operations performed in the image sensor during release control when the exposure time is set to be long in the second embodiment. 9 is a timing chart illustrating the timing of operations performed in the image sensor during release control when the exposure time is set to be short in the second embodiment. It is a flowchart which shows the process of release control in 2nd Embodiment.

Explanation of symbols

10 SLR camera 12 Timing generator (TG)
13 Digital signal processor (DSP)
14 CPU
30 Image sensor 32 Vertical CCD
33 Horizontal CCD
35h1, 35h2 First and second horizontal transfer terminals 35v1 to 35v4 First to fourth vertical transfer terminals

Claims (5)

A plurality of pixels that generate signal charges according to the amount of received light; a first charge transfer path that transfers the signal charges read from the pixels at a speed according to the frequency of a first transfer signal; An image sensor driving unit for driving an image sensor having a second charge transfer path for transferring the signal charge transferred from one charge transfer path by a second transfer signal,
Sweeping a normal transfer signal that is the first transfer signal for transferring the signal charge or the transfer signal for sweeping out the charge remaining in the first charge transfer path, and having a frequency higher than that of the normal transfer signal A signal generation unit that generates a signal and the second transfer signal and transmits the signal to the image sensor;
During the sweep period in which the charge remaining in the first charge transfer path is swept, the signal generation unit generates the second transfer signal so that the sweep signal and the cumulative generation period are shorter than the sweep period. A first control unit ;
A detection unit for detecting an exposure time to the image sensor,
The higher the exposure time detected by the detection unit becomes short, the sweep is the first control unit during the imaging device drive unit, characterized in that Ru reduce the accumulated generation period of the second transfer signal. The first control unit stops generating the second transfer signal during the sweeping period when the exposure time is less than a threshold value, and during the sweeping period when the exposure time exceeds the threshold value. The image sensor driving unit according to claim 1 , wherein the second transfer signal is generated.   2. The image sensor driving unit according to claim 1, wherein the first control unit stops generating the second transfer signal during the sweeping period. Second control for transferring the signal charge generated by exposing the optical image to the image pickup device at each divided transfer timing obtained by dividing the transfer timing of the signal charge through the first and second charge transfer paths. Part
The first control unit sends the second transfer signal to the signal generator so that the sweep signal and the cumulative generation period are shorter than the sweep period during the sweep period immediately before the first divided transfer time. And generating the sweep signal and stopping the generation of the second transfer signal during the sweep period immediately before the second and subsequent divided transfer times. 2. The image sensor driving unit according to 1. A plurality of pixels that generate signal charges according to the amount of received light; a first charge transfer path that transfers the signal charges read from the pixels at a speed according to the frequency of a first transfer signal; An imaging device having a second charge transfer path for transferring the signal charge transferred from one charge transfer path by a second transfer signal;
Sweeping a normal transfer signal that is the first transfer signal for transferring the signal charge or the transfer signal for sweeping out the charge remaining in the first charge transfer path, and having a frequency higher than that of the normal transfer signal A signal generation unit that generates a signal and the second transfer signal and transmits the signal to the image sensor;
During the sweep period in which the charge remaining in the first charge transfer path is swept, the signal generation unit generates the second transfer signal so that the sweep signal and the cumulative generation period are shorter than the sweep period. A first control unit ;
A detection unit for detecting an exposure time to the image sensor,
The higher the exposure time detected by the detection unit becomes short, imaging said sweep the first control unit during the period is characterized in that Ru reduce the accumulated generation period of the second transfer signal device.

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