JP2802946B2 - Still video camera - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a still video camera capable of preventing generation of smear.

"Prior art and its problems" In recent years, a still video camera has been developed which converts a subject image into a large number of electric signal charges by an image sensor and records these as electric signals on a recording medium (magnetic disk).
It is commercially available. Many of such conventional still video cameras use, as an image sensor, a CCD image pickup unit similar to that used in a movie camera in terms of cost.

However, when an electronic shutter is realized using a conventional CCD imaging unit, there is a problem that smear is generated. The outline of the CCD image sensor 11 used in the conventional CCD image pickup unit is shown in FIG. 4 and FIG. In the CCD image sensor 11, each element and circuit are formed on one semiconductor substrate 13. On the light-receiving surface, a row of photoelectric conversion elements composed of a large number of photodiodes 15 as photoelectric conversion elements are formed in a vertical direction, and a vertical transfer CCD 17 is formed in close proximity to each of the photodiodes 15. A large number of photodiodes 15 and vertical transfer CCDs 17 are arranged side by side at predetermined intervals in the horizontal direction.

In addition, 15 rows of photodiodes and vertical transfer CCD 17
Above the vertical transfer CCD 17, a sweep drain 19 extending horizontally in the vicinity of the end of the vertical transfer CCD 17 is formed, and below the horizontal transfer (read) CCD 21 extending horizontally in the vicinity of the vertical transfer CCD 17 is formed. I have.

A conventional imaging operation by the CCD imaging device 11 will be described. The subject image formed on the photodiodes 15 is photoelectrically converted by each of the photodiodes 15 and stored as electrical signal charges.

When a predetermined exposure time T _V is completed, each of the photodiodes
The signal charges accumulated in 15 are simultaneously transferred to the vertical transfer CCD 17 by the periodic transfer signal CTG. And vertical transfer C
The CD 17 is transferred stepwise toward the horizontal transfer CCD 21 and is read sequentially from one end of the horizontal transfer CCD 21 for each line in the horizontal direction.

Here, for example, the photodiode 15a and the vertical transfer CCD 17
When light much more intense than the other areas is incident on a (high-brightness subject is imaged), the area of the vertical transfer CCD 17 becomes
Unnecessary charges accumulate in the vertical transfer CCD 17 due to charges overflowing from the adjacent photodiode 15, sneaking around from the edge of the shield member 23 of the vertical transfer CCD 17, and light passing through the shield member 23, which transfer the vertical transfer CCD 17 Smearing occurs in the image below the photodiode 15a, causing a bright line in the vertical direction to enter the image signal below the photodiode 15a (see FIGS. 6A and 7A).

One means of preventing this smear, is used to adjust the exposure time T _V with opening and closing of the shutter.

However, when the shutter is provided, there is a problem in that the number of members is increased, the lightness and compactness are impaired, and further, extra control is required, so that the circuit configuration becomes complicated.

As another smear preventing means, there is an invention (Japanese Patent Application No. 63-317904) previously filed by the present applicant. In the present invention, the reading of the signal charge is performed after the aperture is closed. In this case, the aperture must be closed at a high speed in consideration of continuous shooting. If the aperture is always closed at high speed like a shutter, power consumption increases, and furthermore, there is a risk of malfunction of other electronic circuits due to voltage fluctuation and noise at the time of startup,
Also, the current consumption was large.

[Object of the Invention] The present invention has been made in view of the problem of the above-described still video camera, and has as its object to provide a still video camera which prevents smear with a simple configuration and consumes low power.

[Summary of the Invention] The present invention focuses on the fact that the frequency of occurrence of smear is relatively low, and a photoelectric conversion element array including a large number of photoelectric conversion elements and a vertical transfer CCD close to the photoelectric conversion element array An imaging device having a light receiving surface in which a large number of light receiving surfaces are juxtaposed, an imaging lens for forming a subject image on the light receiving surface of the imaging device, and a normally closed diaphragm device for adjusting the amount of light incident on the light receiving surface Exposure calculation means for calculating an aperture value and an exposure time based on the subject brightness; and after starting the release operation, after the aperture is opened to a predetermined aperture value, each vertical transfer CC
Smear detection means that reads the charge stored in D, adds the charge for each vertical transfer CCD, and compares the level with a predetermined level, and detects a level higher than the predetermined level by the smear detection means If not performed, the aperture device is closed at a normal speed after the exposure is completed, and when the smear detection means detects a level larger than a predetermined level, the aperture device is closed at a high speed after the exposure is completed, and reading is performed. And a control means for starting.

According to this configuration, the presence or absence of a possibility of occurrence of smear is detected immediately before exposure, and when there is a possibility, reading is started after closing the aperture at a high speed after the end of the exposure, so that the occurrence of smear is eliminated. When there is no exposure, the aperture is closed at a normal speed after the exposure and reading is started, so that power consumption can be reduced.

"Examples of the Invention" The present invention will be described below based on illustrated examples.

First, a configuration of an embodiment in which the imaging device driving device of the present invention is mounted on a still video camera will be described with reference to FIG.

The light beam incident on the imaging lens 31 from the subject passes through the stop 33 and forms an image on the light receiving surface of the CCD image sensor 11. The CCD image sensor 11 converts the formed subject image into a pixel signal,
The transfer signal and the read signal output from the V driver 35 are output to the recording / reproducing unit 37. The recording / reproducing unit 37 converts the pixel signal into a predetermined luminance signal and a predetermined color difference signal, and further records FM modulation and a predetermined DPSK signal on the magnetic disk 39. These operations are performed by MPU (Microcomputer Processing
Unit) 41.

A transfer signal, a sweep signal, and a read signal for operating the CCD image sensor 11 are generated by the MPU 41 and the clock generator 43 for driving the CCD. Clock generator 43
Is a periodic readout pulse CT at a fixed period (1/60 second interval)
G and four-phase periodic transfer pulses C _{V1 to} C _V4 are output. Further, when the sweep-out pulse PHV output from the MPU 41 is at a high level, the clock generator 43 outputs a periodic transfer pulse after outputting a periodic transfer pulse.
Before outputting G, output a four-phase sweep pulse.
The periodic read pulse CTG is a signal for simultaneously transferring the signal charges accumulated in the photodiode 15 to the vertical transfer CCD 17, and the periodic transfer pulse is a stepwise transfer of the charge transferred to the vertical transfer CCD 17 to the horizontal transfer CCD 19. And the readout pulse from the horizontal transfer CCD 21. The sweep pulse is a signal for sweeping out the charge of the vertical transfer CCD 17 to the drain 19.

On the other hand, the MPU 41 outputs the read pulse P at an arbitrary timing.
TG, sweeping the four-phase pulse P _V1 to P _V4, and outputs a switching pulse PS and sweep-pulse.

The MPU 41 and the clock generator 43 output a read pulse PTG and a periodic read pulse CTG to a four-channel multiplexer (MPX) 45, respectively. The multiplexer 45 selectively outputs the pulse output from the MPU 41 or the clock generator 43 to the V driver 35 according to the level of the switching pulse PS output from the MPU 41.

Further, the MPU 41 and the clock generator 43 output read pulses PTG and CTG to the electronic switch circuit 47, respectively. The changeover switch circuit 47 reads the readout pulses PTG, CTG output from the MPU 41 or the clock generator 43 in accordance with the switching pulse PS output from the MPU 41.
TG is alternatively output to the V driver 35.

The circuit configuration relating to the driving of the CCD imaging device 11 has been described above. Next, a circuit configuration related to exposure control will be described.

A release switch 49 is input to the MPU 41.
The release switch 49 is a well-known two-stage switch. The photometry switch is turned on when the switch is pressed halfway, and the release switch is turned on when pressed fully.

The light receiving element 51 receives the subject light and outputs a signal to the photometry unit 53 according to the luminance. The photometric unit 53 outputs a photometric signal obtained by subjecting the signal to predetermined processing such as logarithmic compression to the MPU 41. The MPU 41 executes a predetermined exposure calculation based on the photometric signal, and calculates an aperture value A _V and an exposure time T _V (charge accumulation time). The above operation is executed when the release switch 49 is half-pressed.

When the release switch 49 is fully pressed here, the MPU 41
Based on the calculated aperture value A _V actuates the driving circuit 55 down, opening the aperture 33 to a predetermined aperture value A _V. And MPU41
The CCD image sensor 11 is driven by a predetermined signal and a predetermined timing to read out the signal of the subject image converted into the electric signal, performs predetermined processing in the recording / reproducing section 37, and then performs the magnetic disk 39
To record.

Further, in this embodiment, an A / D converter 57 for smear detection is connected to the output of the CCD image sensor 11 via a low-pass filter 56. This A / D converter 57 is a CCD image sensor 11
Is converted into a digital signal in pixel units or a plurality of pixel units and output to the MPU 41.

The MPU 41 stores digital signals in pixel units or a plurality of pixel units in column units, and adds them in column units. Then, after the signals for one screen are added and stored, it is checked whether or not there is a value (level) larger than a predetermined value (level) determined in advance, thereby detecting the presence or absence of smear.

The above is the basic operation. Next, the imaging operation of this embodiment will be described with reference to the operation timing charts of FIGS. 1 and 2 and the operation flowchart of FIG. This imaging operation is executed by the MPU 41 based on a program stored in the MPU 41.

When the release switch 49 is half-pressed, the routine starts and external photometry using the photometric element 51 is started (S6).
1). That is, the MPU 41 calculates the aperture value A _V and the exposure time T _V by performing an exposure calculation based on the photometric signal output by the photometric unit 53 based on the output of the photometric element 51 that has received the subject light (S63).

When the release switch 49 is half-pressed, the MPU 41 rotates the magnetic disk 39 at a predetermined speed, activates the clock generator 43, and starts a normal image sensor driving operation. That is, the clock generator 43 periodically outputs the periodic read pulse CTG, the periodic transfer pulse, the periodic read pulse CTG.

The MPU 41 checks whether the release switch 49 is half-pressed, and when the half-press is released, exits this routine (S64-1), stops the rotation of the magnetic disk 39, and turns off the power of the clock generator 43. I do. The half-press of the release switch 49 has not been released,
If the switch is not fully pressed, the release switch above
The checking process of 49 is repeated (S64-2).

When the release switch 49 changes from half-press to full-press
The MPU 41 outputs the calculated aperture value A _V via the aperture drive circuit 55.
The aperture 33 is opened until (S65). Thereby, the CCD image sensor 11
On each of the photodiodes 15, a subject that enters the imaging lens 31 and passes through the aperture 33 is imaged.

After opening aperture to a predetermined aperture value A _V MPU 41, the multiplexer 45 dropped switching pulses PS at a low level, to switch the changeover switch circuit 47 to the MPU 41. Further, a readout pulse PTG1 is output to transfer the charge accumulated by the photodiode 15 to the vertical transfer CCD 17, and thereafter, the switching pulse P
Return S to high level. Thus CCD imaging device 11, begin receiving at a given aperture value A _V.

The MPU 41 sets the sweep-out on-pulse PHV to a high level, and causes the clock generator 43 to periodically output a sweep-out pulse. As a result, the charges transferred to the vertical transfer CCD 17 are swept out to the drain 19.

After the discharge is completed, the charges accumulated in the vertical transfer CCD 17 are read by the periodic transfer pulse output from the clock generator 43. The MPU 41 converts the signal read out here into a digital signal by the A / D converter 57 and then takes it in. The signal is integrated for each vertical column, that is, for each vertical transfer CCD 17, and stored.

When all reading and memory operations are completed, it is checked for each vertical transfer CCD 17 whether the level exceeds a predetermined level (S67). Here, for example, in FIG.
When a high-luminance subject is incident in the vicinity, unnecessary charges leak to the region 17a of the adjacent vertical transfer CCD 17. Therefore, unnecessary charges are mixed in the upper portion read through the region 17a. And this is 6A on screen 24
As shown in the figure, the area 17a is a part indicated by reference numeral 25,
The portion above 7a appears as smear below portion 25, as shown at 26.

The level of each vertical transfer CCD 17 is as shown in FIG. 6B. As shown in this figure, it is understood that there is a possibility of generation of smear if there is any exceeding a certain level, and it is understood that there is no risk of generation of smear if it does not exceed a certain level.

Further, in this embodiment, smear reading is performed twice consecutively. Here, in the region of the vertical transfer CCD 17 below the region 17a, the charge that has passed through the region 17a at the time of the first reading is held. That is, unnecessary charges are mixed when passing through the region 17a. Therefore, smear also occurs in a region below the region 17a. This is because, as shown in FIG. 7A, on the playback screen 24, the image of the area 17a appears at the portion indicated by reference numeral 25, and the portion below the area 17a is smeared on the upper portion of the portion 25 as indicated by reference numeral 27. Appears as

The portion above the area 17a of the vertical transfer CCD 17 is 1
It appears as a smear in the portion 26 below the portion 25 in the same manner as the first reading. Therefore, in the second read, the area
Unnecessary charges are mixed into all regions above and below 17a.
When this is reproduced, smears 26 and 27 appear above and below part 25 as shown in FIG. 7A. And each added vertical transfer
The level of each CCD 17 is as shown in FIG. 7B.

Therefore, if the reading is executed twice, even if the area 17a
Even if the image is below, smear can be reliably detected.
Moreover, since the amount of collection of the mixed charges increases by performing the reading twice, the possibility of the occurrence of smear can be detected more precisely.

When there is a possibility of occurrence of smear, after the exposure is completed, the aperture 33 is closed at a high speed, and reading is started.
If there is no possibility of occurrence of smear, reading is performed while the aperture 33 is closed at a normal speed after the exposure is completed (see FIG. 2). That is, the possibility of occurrence of smear is detected, and if smear occurs, the process proceeds to step 71, and if smear does not occur, the process proceeds to step 81 (S6).
9).

In step 71, the switching pulse PS is lowered to a low level, the read pulse PTG2 is output, and the unnecessary charges accumulated in the photodiode 15 are transferred to the vertical transfer CCD 17. After that, the switching pulse PS is returned to the high level, and the charge transferred to the vertical transfer CCD 17 is swept out by the sweep signal periodically output from the clock generator 43.
Sweep to 9, then drop the switching pulse PS to low level.

Then, the exposure is started by transferring the next periodic read pulses CTG5 is stored unnecessary charges in the photodiode 15 outputs a readout pulse PTG3 before exposure time T _V which is calculated back from the time of output to the vertical transfer CCD17 . Read pulse P
After the output of TG3, the switching pulse PS is returned to the high level, and the unnecessary charges transferred to the vertical transfer CCD 17 are swept out to the sweeping drain 19 by the sweeping signal output periodically.

Periodically read pulse CTG5 is output during the exposure time T _V elapsed, signal charges accumulated in the photodiode 15 are transferred to the vertical transfer CCD17 to the exposure time T _V.

After the regular reading pulse CTG5 is output (exposure time T _V
After elapse), the MPU 41 lowers the switching pulse PS to a low level and closes the diaphragm 33 at high speed. Then, after the periodic read pulse CTG5 is output and the aperture 33 is completely closed, the switching pulse PS returns to the high level before the periodic transfer pulse is output. Thereby, the signal charges transferred to the vertical transfer CCD 17 are read out by the periodic transfer pulse.

The MPU 41 converts the signal charges read in this manner into
After a predetermined process is performed by the recording / reproducing unit 37, the data is recorded on the magnetic disk 39.

As described above, when there is a possibility of occurrence of smear, the occurrence of smear is prevented by holding the signal charges in the vertical transfer CCD 17 until the stop 33 is completely closed after the exposure.

The above is the exposure and recording operation in the case where there is smear. If there is no smear, the process proceeds from step 69 to step 81.

First, the MPU 41 drops the switching pulse PS to low level and
The PU 41 is connected to the CCD image sensor 11. Then, the read pulse PTG2 is output to transfer all unnecessary charges stored in the photodiode 15 to the vertical transfer CCD 17. When the unnecessary charges of the photodiode 15 are transferred to the vertical transfer CCD 17, the MPU 41 returns the switching pulse PS to the high level and connects the clock generator 43 to the CCD image sensor 11. Thereby, unnecessary charges of the vertical transfer CCD 17 are swept out to the drain 19 by the sweeping pulse periodically output from the clock generator 43.

After the output of the sweep pulse, the MPU 41 outputs the switching pulse P.
S is dropped to a low level to connect the MPU 41 to the CCD image sensor 11.

And MPU41 reads pulse when calculated back exposure time T _V from when the next periodic read pulses CTG5 is output
The PTG 3 is output to transfer the unnecessary charges accumulated in the photodiode 15 to the vertical transfer CCD 17 to start exposure.

After the exposure is started and before the sweep signal is output from the clock generator 43, the MPU 41 returns the switching pulse PS to the high level to connect the clock generator 43 to the CCD image sensor 11. As a result, unnecessary charges transferred to the vertical transfer CCD 17 by the sweeping pulse output from the clock generator 43 are swept out to the drain 19.

And, at the time of exposure time T _V elapsed, the clock generator
The signal charge accumulated in the photodiode 15 by the periodic read pulse CTG5 output from 43 is transferred to the vertical transfer CCD17.
And the exposure ends.

After the exposure, the MPU 41 starts to stop down the diaphragm 33 at a normal slow speed. In parallel with the narrowing down of the aperture 33,
The signal charge transferred to the vertical transfer CCD 17 is read by a periodic transfer pulse output from the clock generator 43. The read signal charges are recorded on the magnetic disk 39 after being subjected to predetermined processing by the recording / reproducing section 37.

As described above, according to the present embodiment, after the aperture is opened to a predetermined value, the charges accumulated in the vertical transfer CCD 17 are read immediately before the start of exposure, and the level integrated for each vertical transfer CCD 17 is checked to generate smear. If there is a possibility of occurrence of smear, and if there is a possibility of occurrence of smear, signal charges are read out after the aperture is closed at a high speed, so that unnecessary charges are not mixed in during reading and smear can be prevented.
If there is no risk of smearing, normal exposure and readout operations are performed, that is, reading is performed while the aperture is closed at a low speed. Therefore, power consumption when driving the aperture down is small, and voltage change is small, so that other operations are performed. The electronic circuit does not malfunction.

In this embodiment, the vertical transfer CCD is used for smear detection.
The reading of the electric charge stored in the memory is performed twice, but the number of times is not limited thereto.

Further, the present invention is not limited to the illustrated CCD image sensor, but can be applied to an image sensor having another structure as long as it is an interline CCD image sensor.

[Effects of the Invention] As described above, in the present invention, in a still camera provided with an imaging device having a vertical transfer CCD, a signal stored in the vertical transfer CCD is read out before exposure to detect the possibility of smearing. When there is a possibility that smear may occur, the aperture is closed at a high speed after the end of the exposure, and the signal charges are read out. Therefore, no smear is generated. Therefore, the change in voltage is small and there is no risk of causing malfunction of other electronic circuits, and power consumption can be reduced. In addition, since it can be easily configured by changing the control software using a conventional CCD imaging unit, compactness is maintained and the cost is low.

[Brief description of the drawings]

FIGS. 1 and 2 are timing charts for explaining an embodiment of the release operation of the still video camera according to the present invention. FIG. 1 shows a case where a smear may occur.
FIG. 2 is a timing chart when there is no fear of occurrence of smear, FIG. 3 is a block diagram showing an embodiment of a circuit configuration of the still video camera, and FIG. 4 is an image pickup device used in the embodiment. 5 is a sectional view taken along the line V in FIG.
FIG. 6A, FIG. 6B, FIG. 7A and FIG. 7B are enlarged cross-sectional views of the -V portion, and FIG.
5 is an operation flowchart of the embodiment. 11 CCD image sensor, 15 Photodiode (photoelectric conversion element), 17 Vertical transfer CCD, 19 Sweep drain, 21 Horizontal transfer CCD, 33 Aperture (aperture device), 39 Magnetic disk, 41 ... MPU (smear detection means, exposure calculation means, control means), 43 ... Clock generator.

Claims (2)

(57) [Claims] An image pickup device having a photoelectric conversion element array including a large number of photoelectric conversion elements and a large number of vertical transfer CCDs adjacent to the photoelectric conversion element array arranged on a light receiving surface, and an object on a light receiving surface of the image pickup element. A photographing lens for forming an image, a normally-closed aperture device for adjusting the amount of light incident on the light receiving surface, an exposure calculating means for calculating an aperture value and an exposure time based on subject brightness, and a release operation start After that, the smear detecting means for reading out the electric charges stored in each vertical transfer CCD after the aperture is opened to a predetermined aperture value, adding the electric charge for each vertical transfer CCD, and comparing the level with a predetermined level predetermined. When the smear detecting means does not detect a level higher than the predetermined level, the exposure device is closed at a normal speed after the exposure is completed, and Still video camera, characterized in that it comprises a control unit to start reading after to close at high speed the throttle device after completion of exposure when it detects a level greater than the level. 2. The device according to claim 1, wherein said smear detecting means reads out the charge stored in each of the vertical transfer CCDs twice at a predetermined time interval, and adds the charge for each of the vertical transfer CCDs to output a signal having a predetermined value or more. A still video camera characterized by detecting