JP2885207B2 - High sensitivity TV camera device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-sensitivity television camera device using a solid-state image sensor.

[0002]

2. Description of the Related Art Hitherto, as this kind of high-sensitivity television camera device, there has been known a high-sensitivity television camera device disclosed in Japanese Patent Application Laid-Open No. Hei 6-165048 by the present applicant. explain. FIG. 3 is a block diagram showing a high-sensitivity television camera device according to a conventional example, and FIG. 4 is a timing chart showing input and output of electric charges at the time of transition from the standard imaging state to the accumulation imaging state. Note that, in FIG. 7, the standard imaging state is before time t2, and the accumulated imaging state is after time t2.

[0003] In FIG. 3, a CCD image pickup device 1 converts incident light into electric charge corresponding to the amount of light and accumulates the electric charge in an electric charge accumulating section (not shown). The accumulated charge (c) is read out by a charge readout pulse on which a transfer pulse for transferring the charge is superimposed, sequentially transferred to a CCD horizontal / vertical register (not shown), and converted to a predetermined synchronization signal (a). The signal is output to the video signal processing circuit 2 as a CCD output signal (d) based on the signal.

The charge readout pulse (b) is output through a readout pulse driver 8 described later, and its cycle is variable under the control of an accumulation time control circuit 7 described later. It has a period of 1/60 second.
That is, at the time of the standard imaging, the electric charge accumulated at a cycle of about 1/60 second is output as the CCD output signal (d).

[0005] The video signal processing circuit 2 removes noise from the CCD output signal (d), converts the CCD output signal into a time-series video signal, and performs nonlinear processing such as amplification to a specified level and gamma processing. , A / D converter 3. Then, the analog video signal is converted into a digital video signal (e) by the A / D converter 3 and stored in the video memory 4, and then output on a field basis.
The signal is again converted into an analog video signal (f) via the A converter 5 and output.

The video signal level comparator 6 compares the level of the analog video signal (f) output in this way with the level of a predetermined reference signal. Then, when the level of the analog video signal (f) becomes lower than the level of the reference signal, the storage time control circuit 7 is notified that the sensitivity has decreased.

When the accumulation time control circuit 7 receives this notification, it sends out a predetermined control signal to make a transition to the accumulation imaging state, and the readout pulse driver 8 which receives this signal sets the period of the charge readout pulse (b). Thin out in half. That is,
The period of the charge read pulse (b) is about 1/60 second to about 1/60.
It is changed to 30 seconds to extend the charge accumulation time. Then, the amount of accumulated charge increases in proportion to the increase of the charge accumulation time, and thereby the sensitivity is improved.

However, in such an accumulated imaging state,
The video signal is an intermittent signal in which only a video of one field from which electric charges are read is output and no video signal is output in all fields. Therefore, a memory control circuit (not shown) in the video memory 4 controls so as to repeatedly output the same image until the next charge reading, thereby maintaining the continuity of the image signal (f).

[0009]

The above-mentioned conventional high sensitivity television camera apparatus has the following problems. That is, when transitioning from the standard imaging state to the accumulation imaging state, the accumulation time is doubled at a stroke, so that the level of the output analog video signal (f) also doubles as shown in FIG. Of course, in a normal television camera, a negative feedback loop is applied by the auto iris function, such that when the video signal output from the camera increases, the lens iris is narrowed to reduce the video signal. However, when the level of the analog video signal changes at once as described above, the response is delayed because the auto iris function is mechanical, and a so-called bouncing phenomenon in which the reproduced image is momentarily bright occurs, and the image quality is significantly deteriorated. . In particular, when a subject having a different brightness is imaged using an auto pan or the like for surveillance use, this phenomenon appears in the neck.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a high-sensitivity television camera device capable of constantly outputting a stable image even under illuminance that changes every moment.

[0011]

In order to achieve the above object, according to the first aspect of the present invention, light is converted into electric charges using a solid-state image pickup device and stored, and the light is stored based on a predetermined charge reading pulse. Photoelectric conversion means for outputting the converted electric charges, video signal generating means for processing the electric charges output from the photoelectric conversion means to generate a video signal, and changing the cycle of the electric charge reading pulse to accumulate the electric charges in the photoelectric conversion means. and accumulated charge quantity increasing means for increasing the amount, and suppresses electrical charge suppressor means a charge accumulation in the photoelectric conversion means, the
When the video signal falls below a predetermined level, the charge reading is performed.
The period of the output pulse is thinned out in units of the field period.
Controlling the stored charge amount increasing means to increase the stored charge amount;
And the charge accumulation time
The excess charge is controlled by operating the charge accumulation suppression means.
Means for controlling the amount of charge stored so as not to store the load.
Wherein the stored charge amount control means outputs one charge readout pulse.
In the cycle, the charge accumulation suppression
In this configuration , control is performed to shorten the time for operating the control means .

That is, the photoelectric conversion means converts incident light into electric charges and accumulates the electric charges, and outputs the electric charges based on a predetermined electric charge readout pulse. And outputs as a video signal. The output level of the video signal is proportional to the amount of charge accumulated in the photoelectric conversion means, and the amount of accumulated charge is proportional to the charge accumulation time, that is, the cycle of the charge readout pulse. When the output level of the video signal changes due to a change in illuminance or the like of the image pickup, the accumulated charge amount control means controls the accumulated charge amount increasing means to change the cycle of the charge readout pulse. The amount of accumulated charge is increased, or the operation of the charge accumulation suppressing means is controlled, and the amount of accumulated charge in the photoelectric conversion means is controlled by suppressing charge accumulation in the photoelectric conversion means. Control.

[0013] Suppressing the accumulated electric charge in the electric charge accumulating means, as the wording implies, means not to accumulate the electric charge, but also means releasing a predetermined amount of electric charge from the accumulated electric charge. Including. Regarding this, for example, if a predetermined electronic shutter is provided in the photoelectric conversion means and the electronic shutter is operated at the same time as the start of the accumulation of the electric charge, the electric charge can be prevented from being accumulated during the operation of the electronic shutter. If the electronic shutter is operated after the electric charge is once accumulated, a predetermined amount of electric charge can be discharged according to the operation time.

On the other hand, the storage charge amount control means controls the storage
It is also possible to control only the means for increasing the accumulated charge,
It is also possible to control only the charge accumulation suppressing means.
Furthermore, both can be controlled simultaneously.

That is, when the amount of electric charge stored in the photoelectric conversion means decreases due to a decrease in the illuminance of the image pickup and the like, and the output level of the video signal becomes equal to or lower than a predetermined level, the amount of electric charge stored in the electric charge readout pulse is controlled. The accumulated charge amount increasing means is controlled so that the cycle is thinned out in field cycle units. As a result, the charge storage time is substantially extended, the stored charge amount is increased, and the output level of the video signal is also increased. The electric charge accumulation is controlled by operating the electric charge accumulation suppressing means by the amount. For this reason, while the output level of the video signal increases, a sudden level change is suppressed.

Further, the above-mentioned stored charge amount control means includes one charge
In the load readout pulse cycle, the above
The time for operating the load accumulation suppressing means is shortened. Do
And the charge storage time gradually increases, and the video signal
The output level of the signal also increases gradually.

By the way, when the charge readout pulse is thinned out as described above, an image of only one field from which the charge is read out is output, and an intermittent signal in which no image signal is output in all the fields is obtained. I can't keep her. Therefore, the invention according to claim 2, in the high-sensitivity television camera apparatus according to claim 1, the high-sensitivity television camera apparatus stores the video signal output from the video signal generating means, the charge read When the period of the pulse is thinned out, a video memory means for repeatedly outputting the stored video signal is provided.

That is, the video memory means stores the video signal output from the video signal generation means at the time of standard imaging, and sequentially outputs the video signal based on a predetermined synchronization signal. However, when the cycle of the charge readout pulse is thinned out as described above, the video memory means repeatedly outputs the stored video signal and maintains the continuity of the video signal.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a high-sensitivity television camera apparatus according to an embodiment of the present invention, and FIG. 2 is a timing chart showing input and output of electric charges at the time of transition from a standard imaging state to a storage imaging state. ing. Note that, in FIG. 6, the standard imaging state is before time t1, and the accumulated imaging state is after time t1.

In FIG. 1, the photoelectric conversion means comprises a CC
The D image sensor 10 corresponds to the image signal generating means, and the image signal generating means corresponds to the image signal processing circuit 20. CCD imaging device 10
Is a general vertical overflow drain structure (VOD
), And converts the incident light into electric charges corresponding to the amount of light and stores the charges in a photodiode (not shown) of the photoelectric conversion unit 11. The photoelectric conversion unit 11 includes, in addition to a photodiode, a CCD horizontal / vertical register (not shown) and a CCD horizontal / vertical register for generating a transfer pulse to each register.
And a vertical driver. The charge (d) accumulated in the photodiode is sequentially transferred to the CCD horizontal / vertical register by a charge reading pulse (b) described later on which the transfer pulse is superimposed, and a predetermined synchronization signal (a)
Is output to the video signal processing circuit 20 as a CCD output signal (e) via an output amplifier (not shown).

The video signal processing circuit 20 removes noise from the CCD output signal (e), converts the CCD output signal (e) into a time-series video signal, and performs non-linear processing such as amplification to a specified level and gamma processing. A / D converter 3 described later
0 to D / A converter 50 are sequentially transferred and output as a normal analog video signal (g). In the present embodiment, the read pulse driver 60 corresponds to the accumulated charge increasing means.

The read pulse driver 60 outputs the charge read pulse (b) to the CCD image sensor 10 as described above. This charge readout pulse (b) has a period of about 1/60 second in the standard imaging state, and
The imaging element 10 accumulates electric charges for about 1/60 second in the standard imaging state. However, as described later, the control signal from the accumulation time control circuit 90 is received and the time t1
In the transition from the standard imaging state to the accumulation imaging state, the pulse interval is reduced to two fields and the cycle is reduced to about 1/3.
Change to 0 seconds to extend the charge accumulation time.

In the present embodiment, when the read pulse driver 60 receives the control signal from the accumulation time control circuit 90, the pulse interval of the charge read pulse (b) is reduced to two fields. It is sufficient that the charge accumulation time can be increased by changing at least the pulse period. Needless to say, the pulse interval can be reduced to three or more fields, or the pulse interval may be varied according to the output level. .

The CCD image pickup device 10 has an electronic shutter (not shown). The electronic shutter and the shutter pulse driver 70 constitute the above-mentioned charge accumulation suppressing means. The electronic shutter operates with a shutter pulse (c) generated by a shutter pulse driver 70 described later.
A predetermined amount of charge is discharged from the charge stored in the photodiode. More specifically, it has a structure in which a substrate bias voltage is applied by the same shutter pulse (c), and unnecessary charges are swept toward the substrate.

When the shutter pulse driver 70 receives the control signal from the accumulation time control circuit 90 described later, the shutter pulse driver 70 performs the horizontal transfer blanking period in the first half of each frame of the charge readout pulse (b) modulated as described above. , A shutter pulse (c) having a predetermined duration superimposed on is generated, and the duration is converged by one horizontal transfer blanking period (64 μS) as each frame elapses. As a result, in the first half of each frame, the above-mentioned electronic shutter operates and no electric charge is accumulated, so that even if the electric charge accumulation time is prolonged, no excessive electric charge is generated, and the bouncing phenomenon can be suppressed. Can be gradually increased to increase the output without feeling uncomfortable.

In the present embodiment, the electronic shutter is operated by the shutter pulse (c) superimposed on the horizontal transfer blanking period, and the pulse duration of the shutter pulse (c) is changed by one horizontal line as the frame elapses. The convergence is performed for each transfer blanking period. However, the present invention is not necessarily limited to this configuration, and it is sufficient that at least excess charges can be discharged. Therefore, the electronic shutter may be operated for a predetermined period of time in each frame, or even if the operation time of the electronic shutter gradually converges, a period of time equal to or longer than a predetermined horizontal blanking period It may be converged at a time, or may be changed as appropriate.

The storage charge amount control means for controlling the operations of the read pulse driver 60 and the shutter pulse driver 70 includes a video signal level comparator 80 and a storage time control circuit 90. Video signal level comparator 80
Receives a reference signal of a predetermined level and an analog video signal (g) output from the D / A converter 50, compares the levels of the two, and determines that the level of the analog video signal (g) is equal to that of the reference signal. If the level falls below the level, this is notified to the accumulation time control circuit 90.

Upon receipt of this notification, the accumulation time control circuit 90 sends a predetermined control signal to the readout pulse driver 60 and the shutter pulse driver 70 to make a transition from the standard imaging state to the accumulation imaging state. The read pulse driver 60 modulates the charge read pulse, and the shutter pulse driver 70 sends the shutter pulse to make a transition to the accumulation imaging state.

By the way, in this accumulated imaging state,
The video signal is an intermittent signal in which only a video of one field from which electric charges are read is output and no video signal is output in all fields. Therefore, the A / D converter 30, the video memory 40, the D / A
The configuration includes a converter 50.

As described above, the output from the video signal processing circuit 20 is converted into a digital signal by the A / D converter 30 and stored in the video memory 40. In the standard imaging state, the digital video signal (f) stored in the video memory 40 is sequentially output based on the synchronization signal (a) under the control of a memory control circuit (not shown).
An analog video signal is generated via the A converter 50.
However, in the accumulated imaging state, as described above, the video signal is an intermittent signal, so that the memory control circuit controls the same video signal to be repeatedly output until the next charge readout to maintain the continuity of the video signal. . .

Next, the operation of the high sensitivity television camera device according to the present embodiment will be described. The CCD image pickup device 10 converts the incident light into electric charges corresponding to the amount of light and converts the incident light into a photoelectric conversion unit 11.
In a photodiode (not shown). Then, the charge (d) accumulated in the photodiode is read out in a standard state by a charge readout pulse (b) having a pulse period of about 1/60 second, and the CCD horizontal / vertical register and the output amplifier are read out. The signal is output to the video signal processing circuit 20 as a CCD output signal (e) through the section.

The video signal processing circuit 20 removes noise from the CCD output signal (e), converts it into a time-series video signal, and further performs non-linear processing such as amplification to a specified level and gamma processing. , A / D converter 30. After the video signal is converted into a digital signal by the A / D converter 30 and stored in the video memory 40, in a standard state, the D / A converter is sequentially turned on based on a predetermined synchronization signal (a). The D / A converter 50 converts the signal into a normal analog video signal (g).

Here, when the output level of the analog video signal (g) decreases and becomes lower than the level of the reference signal in the video signal level comparator 80, the video signal level comparator 80 determines this by an accumulation time control circuit. 90 is notified, and the camera enters the accumulation imaging state. Upon receiving this notification, the accumulation time control circuit 90 sends out a predetermined control signal to the read pulse driver 60 and the shutter pulse driver 70. Read pulse driver 60 receiving this control signal
Modulates the charge readout pulse (b) having a period of about 1/60 second in a standard time to a period of about 1/30 second, thereby extending the charge storage time and increasing the amount of stored charge.

On the other hand, the shutter pulse driver 70 sends a shutter pulse having a duration T1 in the first half of the first frame of the modulated charge readout pulse (b). That is, for the time T1 in the first half of the frame, the electronic shutter operates and no electric charge is accumulated, so that the bouncing phenomenon can be prevented without accumulating excessive electric charge.

Further, in the second frame of the modulated charge readout pulse (b), a shutter pulse having a duration T2 obtained by subtracting one horizontal blanking period from the duration T1 of the shutter pulse in the first frame is transmitted. .
In other words, the charge storage time in the second frame is slightly longer than the charge storage time in the first frame, and the amount of stored charge slightly increases accordingly. Thereafter, similarly, by gradually converging the duration of the shutter pulse every time a frame elapses, the accumulated charge amount gradually increases, and the level of the video signal (g) also improves.

By the way, in such an accumulated imaging state, the video signal is an intermittent signal in which only the video of one field from which the electric charge is read is output and the video signal is not output in all the fields. Therefore, the memory control circuit controls the output of the same video signal repeatedly until the next charge reading, thereby maintaining the continuity of the video signal (g).

As described above, when the CCD image pickup device 10 that converts light into electric charges and accumulates the accumulated charges based on the electric charge readout pulse generated by the readout pulse driver 60 to generate an image signal, the same image is generated. The amount of accumulated charge can be increased by modulating the same charge readout pulse in accordance with the output level of the signal, and a predetermined electronic shutter is operated by a shutter pulse generated by the shutter pulse driver 70 to suppress accumulation of excess charge. Since it is possible, it is possible to provide a high-sensitivity television camera device that can always output a stable video even under illuminance that changes every moment.

[0038]

As described above, according to the present invention, the power
When the camera sensitivity is reduced, while suppressing the bouncing phenomenon
Since the output level of the video signal is gradually improved,
It can output video without any.

According to the second aspect of the present invention, the continuity of the video signal can be always maintained even if the period of the charge readout pulse is thinned.

[Brief description of the drawings]

FIG. 1 is a block diagram of a high-sensitivity television camera device according to an embodiment.

FIG. 2 is a timing chart showing input and output of electric charges when the high-sensitivity television camera device according to the embodiment transitions from a standard imaging state to a storage imaging state.

FIG. 3 is a block diagram of a high-sensitivity television camera device according to a conventional example.

FIG. 4 is a timing chart showing input and output of electric charges when a high-sensitivity television camera device according to a conventional example transitions from a standard imaging state to an accumulation imaging state.

[Explanation of symbols]

 Reference Signs List 10 CCD image pickup device 11 Photoelectric conversion unit 20 Video signal processing circuit 30 A / D converter 40 Video memory 50 D / A converter 60 Readout pulse driver 70 Shutter pulse driver 80 Video signal level comparator 90 Storage time control circuit

Continuation of the front page (56) References JP-A-4-170175 (JP, A) JP-A-4-105478 (JP, A) JP-A-61-248670 (JP, A) JP-A-61-274470 (JP) , A) JP-A-64-64474 (JP, A) JP-A-4-95477 (JP, A) JP-A-4-177985 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB Name) H04N 5/30-5/335

Claims (2)

(57) [Claims] 1. A photoelectric conversion means for converting light into electric charges using a solid-state imaging device and storing the converted charges, and outputting the stored charges based on a predetermined charge readout pulse; Video signal generating means for processing to generate a video signal; storage charge increasing means for changing the period of the charge readout pulse to increase the storage charge quantity in the photoelectric conversion means; A charge accumulation suppressing means for suppressing the electric charge when the video signal falls below a predetermined level;
Decrease the cycle of load readout pulse in field cycle units
To increase the amount of accumulated charge
At the same time as this charge accumulation time
Control by operating the charge accumulation suppressing means.
Means for controlling the amount of accumulated charge to prevent accumulation of excess charge;
Comprising a, the accumulated charge amount controlling means, on one of the charge reading pulse period
In the above, the charge accumulation suppressing means
The feature is that control is performed to shorten the time for operating the
And the high-sensitivity TV camera device. 2. The high-sensitivity television camera device according to claim 1, wherein said high-sensitivity television camera device stores a video signal output from said video signal generating means and sets a period of said charge readout pulse to an interval. A high-sensitivity television camera device comprising: a video memory means for repeatedly outputting a stored video signal when pulled.