JPS58190164A - Method and device of control of cctv camera automatic diaphragm - Google Patents

Abstract

PURPOSE:To vary the photometry system from a state of initialization to an averaged overall photometry system or a peak light photometry system, by controlling the charging voltage of a voltage multiplying capacitor of a rectifying circuit. CONSTITUTION:An input terminal I is connected to an inverse amplifying circuit 1 having an operational amplifier A1 via a capacitor C1, and a signal VP1 containing no DC component is obtained at an output terminal P1. A photometry system varying circuit 3 having a voltage multiplying capacitor C3 and a voltage multiplying diode D3 is connected to the terminal P1. Thus an output signal VP2 is obtained at a point P2, and at the same time the Dc voltage VP3 is obtained at an output terminal P3 with rectification of a diode D2. The collector of a transistor TR is connected to the input side of the capacitor C3. Then the base voltage VB of the TR is varied to control the charging voltage of the capacitor C3. The voltage VP3 is compared with the reference voltage VP4 of a reference voltage circuit 4 through a comparator 2. Then a diaphragm control signal Vout is obtained at an output terminal O.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic aperture control method and apparatus for a CCTV camera lens configured to perform aperture control using a video output signal from a television camera.

Although there is room to improve the apparent sensitivity of a television camera by using an amplification processing system, etc., it is essentially determined by the brightness of the lens and the sensitivity of the camera tube. For this reason, the conditional force S for obtaining the optimum picture quality will differ depending on the camera. This is why automatic aperture control devices require sensitivity adjustment, and most conventional devices have J1 scale 1
rIIa Capacity S installation However, originally, sensitivity adjustment is to adjust the absolute brightness of a subject with a relatively narrow contrast range (about 3:1). In principle, it was impossible to adjust in such a wide case. In other words, in order to improve the optimum image quality, in addition to adjusting the absolute brightness of the subject, one of the important factors is adjustment corresponding to the ratio of bright parts to dark parts, that is, the contrast range. In the natural world, the range of contrast is several tens, ■, even if the size of a cloud is large, and in the case of Ukenin, it reaches several hundred = 1. On the other hand, the contrast display range of images reproduced on television television is approximately 30 to 40:1 [7. Therefore, if there are bright and dark areas on the same screen at the same time, it is necessary to decide whether the main subject should be the bright area or the dark area.

Principle [2. The side-lighting method that is suitable for photographing dark areas as the main subject is the average metering method, and the side-lighting method that is suitable for photographing bright areas as the main subject is the peak side-lighting method. Currently, the above-mentioned two types of photometry methods are being considered as video photometry methods that perform aperture control using the video output signal of a television camera. However, none of these methods are complete. In other words, when there are bright and dark areas on the same screen at the same time (as mentioned above), with the average side lighting method, the gradation of the bright areas may disappear due to white collapse. Also, with the peak metering method, dark areas that should be sufficiently visible due to the sensitivity of the camera often become invisible.For this reason, the conventional fixed metering method However, this method had the disadvantage that it was not possible to obtain the optimum image quality for subject conditions with a wide contrast range.

In order to eliminate the above-mentioned inconvenience, the present invention receives a video signal from a television camera using an inverting amplifier circuit, converts it to fC, and then doubles the voltage and rectifies it, and compares the resulting DC voltage with a separately provided reference voltage. In the automatic aperture control means for a CCTV camera which obtains a control signal, by making it possible to adjust the charging voltage of the voltage doubler capacitor of the rectifier circuit, it is possible to adjust the charging voltage of the voltage doubler capacitor of the rectifier circuit to the average side illumination method or to the peak photometry from the initial setting state. The system is equipped with a side light system variable circuit that is similar to the $111 optical system.

Figures 2 and 2b show the subject and video output signal waveform used when investigating the photometry method, and Figures 3a to 3c show the video output signal (Vin) and area ratio (Vin) in Figures 28 and 2b.
It is a characteristic curve showing the relationship between S, ). In FIG. 2b, 2 is a video signal, and 8 is a synchronization signal. Note that the area ratio in this case means the ratio of the bright portion to the entire screen, and is expressed as follows.

Sn = <-' 12x 100 (%) Figures 3A and 3b show how the characteristic curves described above change depending on the contrast, so Figure 3a shows the average -' in the case of the light system. Figure 3b relates to the case of the peak side light method. In the figure, ■ means high contrast, ■ means low contrast, and ■ means intermediate contrast between ■ and ■. From the figure, the average It can be seen that the effect of contrast is more pronounced in the photometry method, while the effect is less in the peak side light method.In addition, when the contrast is low in ■, both the average and peak photometry have a negative effect on the video output, which is the standard of the photometry method. Since the area ratio (So) to the signal (Vin) extends to a small point (S, ), it can be seen that it can be used in a considerable range regardless of the photometry method.Figure 3c shows the level of the reference voltage. It shows the change in the characteristic curve when changing the sensitivity and adjusting the sensitivity. ■ is for high level, ■ is for intermediate level, and ■ is for low level.
Shown.

The present invention has fully taken into account the above-mentioned characteristics, and has developed a contrast display range (30 to 40:1) that can be reproduced on a television.
), you can freely compress the contrast even when it exceeds In addition, the photometry method can be adjusted for high-contrast subjects such as those in the natural world, and these can be adjusted for each purpose mentioned above. It is made operable.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

1 is the input signal Vin for the video output signal from the TV camera.
The input terminal is connected to an inverting amplifier circuit 1 having an operational amplifier A1 via a capacitor c1, and
9. The configuration is such that an inverted and amplified signal (Vl), which does not include a DC component, is obtained at the output terminal P of A.

Spinning: A voltage doubler capacitor C4 is connected to the output terminal P1, and a voltage doubler diode D is connected in series to the zero voltage section.

The photometric method variable circuit 3 south of is connected, and the point P
, and obtain the output 4m P, and the diode D2 &
(Y-, 1 rectified, DC voltage vp at its output terminal P,
It is configured so that it can be obtained. The DC current HVP at the output terminal P3 is connected to the base*1 [Jv
p, and 1 by the comparator circuit 2 having the operational amplifier A2.
i: is compared, and as a result, the aperture control signal Vout is obtained at the output end OK.

Here, in the embodiment of the present invention, a Vc transistor T is connected to the capacitor C1 of the variable circuit 3.
The collector terminal of the transistor 1' is connected to the input end of the capacitor C8, and the emitter terminal is connected to the output end P3. A variable resistor VR is connected to the base terminal of the transistor Tr via a resistor, and by making the base voltage VB variable, the capacitor C
The charging voltage of 5 can be adjusted. Also, a fixed resistor R31 and a variable resistor VR, connected in series,
This is a variable photometry circuit that is used in parallel with the voltage doubler capacitor C1. Further, 6 is a variable resistor VR of the reference voltage vp4,
This is a reference voltage circuit for remote control which has the variable resistor VR4 instead of the variable resistor VR4.

In the embodiment of the present invention having the above configuration, the input terminal I
Assume that an input signal Vin having a waveform as shown in FIG. 4(,) is input from a television camera as a video output signal, corresponding to the test chart ()K in FIGS. 2a and 2b.

In this waveform, the rectangular portion on the positive side corresponds to the bright portion of the image. This input signal Vjn is inverted and amplified by the inverting amplifier circuit 1 as shown in FIG. Therefore, it has settled into a steady state in which the positive and negative areas are equal around the O-0 line in the figure. Here, when the variable resistor VR is adjusted to lower the base voltage vB of the transistor Tr below a predetermined range, the transistor Tr becomes saturated, and the signal VP at the output side of the voltage doubler capacitor C8 is
, i becomes equal to the signal VP, as shown in FIG. 4(e). Therefore, while the width of the waveform corresponding to the bright part of this waveform is wide, the baseline (0-Oi) changes as the amplitude changes.
However, as the width of the bright portion becomes narrower, it will no longer be affected by changes in amplitude, and as a result, the DC voltage vp at point P after rectification will remain unchanged. That is, when the base voltage vB is made small, the DC voltage (P) is determined by the average value of the entire video output signal, so it can be said that the average photometry method is suitable when a dark area is the main subject. Next, when the variable resistor VR3 is adjusted so that the base voltage -VB is above the above-mentioned required range,
The transistor Tr is in Hasumachi (state), and the signal at the output terminal P1 is connected to the voltage doubler diode D at the negative output of P1.
is in the ON state and Tsumugi Co/Capacitor C1 is not charged.
The diode D is turned off by the subsequent positive output, and a positive signal is added to the previously charged voltage, and the output signal vp at point P is shown in FIG. 4(d). Even if the width of the signal waveform corresponding to the bright part is narrow, changes in amplitude can be detected. Therefore, when the pace voltage VB is increased, it can be said that the peak photometry method is suitable when a bright area is the main subject. In addition, a group of resistors (resistor R5I and variable resistor VR, , ) connected in parallel to the voltage doubler capacitor C3.
is for suppressing the average photometry method, and determines the characteristic curve when it is set to the most average photometry side, and therefore determines the variable range of the photometry method. Since this circuit requires two control lines, it is usually installed inside the lens rather than being operated remotely.

Figures 5 to 8 show the Eirin signal level and area ratio (So
) is a diagram illustrating the operation of the device of the present invention, in which the relationship between the two is expressed as a graph.

In Fig. 5, ■ is the characteristic curve for average photometry, and if Bell Feng is obtained and the optimum video signal level is within the diagonal line, or if the area ratio becomes B, the level becomes high as B, and the so-called The amount of light becomes excessive. In such a case, the video signal level can be lowered to below by adjusting the sensitivity of the variable resistor VH2 of the reference voltage circuit 4 or 6 by VR. At this time, the characteristic curve changes as shown in Figure 3c, so it is good when the th product ratio is B, but it is A.
When the patient urinates in this condition, the video signal level becomes as low as a, resulting in overexcess and insufficient round lids.

In such a case, eC1 photometry method Machihen circuit 3 or 5 mouth 1
When the variable resistor VR or VR is operated and the photometry method is changed to the peak photometry power formula 1c, the characteristic curve becomes 9F in Figure 6.
] Since the area ratio changes, the optimum video signal level can be obtained both in the area ratio A state and in the B state.

The above is true even when the contrast changes.

Curve 2 in FIG. 7 is a characteristic curve in the average photometry method when the contrast range is relatively narrow. In such a contrast, the image signal level falls within the optimum range of a and bl, whether the area ratio is in the state A or in the state B. However, [7] When the contrast range is wide as in the natural world and exceeds several tens of ratios, the characteristic curve C changes as shown in ■, and the image signal level at the area ratio B becomes as high as b.

In this case, as in the previous example, the gIL adjustment is carried out to bring the Eirin signal level, and when it is lowered at t, the characteristic curve ■ changes as shown by ■, and as a result, when the area ratio returns to the state of A, the level,
This will result in too low a value of &.

1. In this case, as the contrast range narrows, the characteristic curve ■ changes as shown by the broken line ■, so even if the area ratio - is B and 1K, what will be the Eirin signal level when changing the bI& method to the peak metering method? It can be operated without any inconvenience.

In FIG. 8, curve (2) is a characteristic curve in the average side illumination method when the contrast range is relatively narrow.

In this case, as before, the Eirin signal level is a,
bI is within the optimal range. Here, as the contrast range widens, the characteristic curve (■) changes as shown in (■). In this situation, if you change the photometry method to peak metering method,
Even if the contrast range is wide, it is possible to obtain a curve extremely close to the characteristic curve (2) when the contrast range is narrow. Therefore, the area ratio A
, B, the optimum level can be obtained. In addition, in the photometry method where the characteristic curve (■) is obtained when the contrast range is wide, when the contrast range narrows, the characteristic curve becomes like the broken line (■), indicating that the optimum level can be obtained at which area ratio between dove and λ. /C becomes. Therefore, in this case, keep the sensitivity adjustment constant,
The optimal level of the video output signal can be selectively obtained simply by variably adjusting the photometry method.

In addition to the method using transistors as shown in FIG. 1, a circuit using a variable resistor and a photocoupler may also be adopted as an embodiment of the present invention. In this case, two control lines are required, which is inconvenient in terms of wiring when using a remote control system.

As described above, the present invention includes first and second means capable of adjusting the video output signal of the television camera in response to subject conditions with a narrow contrast range and subject conditions with a wide contrast range, respectively. Because of its configuration, the contrast display range that can be reproduced on TV screens (30 to 4
This has the effect of allowing you to freely adjust the video output signal to the optimal level for subject conditions that exceed 0:1), and if you configure the metering method to be remotely controllable, you can install the camera outdoors. Automatic aperture control for CCTV cameras is effective when the subject is the natural world. Further, by using a transistor, the number of control lines for varying the photometry method can be reduced to one, which has the effect of enabling remote control with a simple circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the main parts of an embodiment of the present invention, and FIG.
Figures 3 and 2b are explanatory diagrams showing the relationship between the subject and the video output signal waveform, Figure 3a is an explanatory diagram showing the relationship between the average photometry method and contrast, and Figure 3b is an explanatory diagram showing the relationship between the peak photometry method and contrast. , Fig. 3c is an explanatory diagram showing the difference in the side lighting method when changing the reference voltage level, Fig. 4 is an explanatory diagram showing the relationship between the input signal and the output signal waveform at each stage, and Figs. FIG. 8 is an explanatory view showing the operating mode of the apparatus of the present invention. to input terminal, O: output terminal, A, , A,: operational amplifier,
Tr: Transistor, C1 double tortoise pressure capacitor, D3
: Voltage doubler diode, ■8. VR4, VR,, VR6
: Variable resistance, Vin : Input signal (TV camera video output signal), VP, : Output signal of point Pt, VP
, : Output signal of point Pt, VP, : Point Pt
output signal, VP4: reference voltage, Vout: aperture 9 control signal, inverting amplifier circuit, 2: comparison circuit, 3.5: side light system variable circuit, 4, 6: reference voltage circuit. 5th (!l O35〇8 100S,
t%1 Fig. 7 δ0(γ・] ?!'S6!7I So Lγ・] Fig. 8 S, L/, J

Claims (6)

[Claims] (1) In an automatic aperture control method that performs aperture control using a DC voltage obtained by rectifying the video output signal of a television camera, the Eirin output signal is optimized for subject conditions with a relatively narrow contrast range. The first means of adjusting the level and adjusting the Eirin output signal to the optimal level for subject conditions with a wide contrast range iJ1! An automatic aperture control method for a CCTV camera, characterized in that the first and second means are adjustable according to subject conditions. (2) The method according to claim (1), characterized in that the second means is remotely operated.
Automatic aperture control method for CTV cameras. (3) An automatic aperture control method for a CCTV camera according to claim (1), characterized in that the first and second means are each remotely controlled. (4) An inverting amplifier circuit that receives and inverts and amplifies the video output signal of the television camera, a comparison circuit that obtains an aperture control signal by comparing the DC voltage obtained by rectifying the video output signal with a reference voltage, and the above-mentioned comparison circuit. A reference voltage circuit, which is the first means of adjusting the video output signal to the optimum level by varying the reference voltage of the circuit, and a photometry method that is located between the inverting amplifier circuit and the comparison circuit described in 1. An automatic aperture control device for a CCTV camera comprising a photometry method variable circuit serving as a second means for variably adjusting between an average photometry method and a peak photometry method. (5) The device odor control and photometry variable circuit according to claim (4) comprises a voltage doubler capacitor receiving the output of the inverting amplifier circuit, and a cathode connected to the output node 1 of the capacitor and connected to the ground side. It consists of a voltage doubler diode whose anode is grounded, and a transistor whose emitter is connected to the output side of the capacitor and whose collector is connected and a variable resistor is provided on the pace side. An automatic aperture control device for a CCTV camera, characterized by variable adjustment to make the photometry method variable. (6) An automatic aperture control device for a CCTV camera according to claim (5), which is configured to be adjustable by a remotely controlled variable resistance circuit such as a pace voltage of a transistor.