JPS58142684A - Automatic controlling method and controlling circuit for beam current - Google Patents

Abstract

PURPOSE:To prevent occurrence of ''oscillation'' and stabilize operation even when a subject having brightness range of above 8 is photographed by feeding back signal current obtained by the target of an image pickup tube to the grid electrode of the image pickup tube through a circuit having compressed characteristic. CONSTITUTION:Assuming the represent voltage of an input terminal of an amplifier that constitutes a beam current controlling circuit as Vin, and the represent voltage obtained at the output terminal as Vout. The grid electrode of the image pickup tube is controlled to become Vout=A.Vin<x>, x<=1/r (where r is an index when beam current of an image pickup tube is indicated by voltage between the grid and cathode) or using a beam current controlling amplifier having similar characteristics. That is, DC is cut off from the input terminal 41 of a beam current controlling amplifier 4 through a condenser 43, and led to a diode 45 restricting the current by a resistance 44. Voltage on both end of the diode 45 is amplified through a linear amplifier 46 and grid current of the image pickup tube 1 is controlled from an output terminal 42.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit that controls the current value of a video camera depending on the current value of a video signal.

It is.

The image...Irai 1. The phenomenon where the city has a tail (Komeno I/Tail) is +"'13 The beam current of the image tube is rising 1
A temple painting occurs. The line it+ without -7 is expressed by the fact that the beam current rn becomes smaller as the signal current 18 generated by the image pickup tube becomes smaller, that is, it is expressed by the following equation.

IB/■s・・−・・・・・・・・ 11) Conventionally, to prevent this phenomenon from rain, anticomeno{・tail (△CT) tube and 吋(rI rero imaging・1” water Illψ) were used.
1,Nreteii) or koneha! Samurai Senri/', C lif
t Hete Aro/γ・V)
f V)le>'I1teicii. A C T □i
7 /r・Ill The most practical way to control the beam so that it satisfies the first 2)t is to constantly flow a beam current larger than the maximum value of the signal current, but this method Due to the increased diameter, there are problems such as a decrease in image quality, an increase in power consumption, and the shortening of the life of the image pickup tube, so it cannot be adopted for a month.

It is desirable to control the beam current so that it always flows somewhat larger in response to changes in the signal current. Therefore, as a beef current optimum control circuit that performs such control, 11. Two methods are used:

1) Equivalent return beef, current control method 11) Signal current feedback control method 11) has the advantage of simplifying the two-circuit configuration compared to method 1), but as long as comet tails do not occur, The drawback is that the brightness ratio of the video signal cannot be maintained at -9. That is, in the conventional signal current feedback control system, the brightness/darkness IL of the video signal, which does not produce a comet tail, is at most 6 times as sharp. If the intensity is higher than this, unstable phenomena such as "oscillation" will occur.
It is desired that it will operate stably and stably in both directions.

Regarding stable phenomena such as "oscillation", Shinkyu-den 1I11
Let me explain using the Mi-Kei method as an example. Shinkyuden Mt, Return 7
, 17 heem amount control block diagram is shown in Figure 1.
In this figure, 1 is an image pickup tube, 2 is its target surface, 3 is a preamplifier, and 4 is a camera tube 1. City flow 11ilHf14
1 is an amplifier, 5 is a grid electrode of the image pickup tube 1, and 6 is a cathode electrode.

This circuit operates as follows.

In a portion where the brightness of the subject (not shown) changes from a low state to a high state, the signal current sent from the surface 2 of the image pickup tube 1 increases, and the output of the preamplifier 3 also increases. This output controls the grid electrode 5 of the image pickup tube 1 via the beam current control amplifier 4, which has a linear output relationship. l～However, the pressure between the glinode and the canode vG
K increases linearly with the signal current ■s. In other words, ■GK-to 1・■8 ・・・・・・・・・・・・・・・
...121-On the other hand, the beam current value of the image pickup tube 8
increases in proportion to the second to third power of the grid-cathode distance VGK.

In other words, this relationship can be expressed as an expression.

'B = K2・■G'K (r=2~3)--
...13) L, therefore, the target surface 2 of the image pickup tube 1
The relationship between the signal current (8) and the current IB can be expressed by the following equation.

■+1- to 3・I8r ・・・・・・・・・・・・
・・・・・・・・・・・・(4+ In other words, the beam current does not increase linearly with respect to the signal current, but increases in proportion to the second or third power. In this case, the beam current does not increase linearly with respect to the signal current. For this reason, a phenomenon called °°total oscillation occurs.In Figure 2, which shows the relationship between the signal current 8 and the beam current IB, it is set to signal current - beam current + 11, which is represented by the characteristic curve T1. In this case, the beam current value is larger than the signal current value, and there is no beam current shortage.

Under these setting conditions, when the illuminance of the target 2 is high (bright screen), the signal current 8 increases, and in response to this, the beam current 1-7 increases by 1 to quickly increase the beam diameter. becomes thicker. As a result, the scanning area of the target 2 increases, and the signal current 2 increases. As the signal type * I s increases, the inter-beam flow IB increases. As the beam current IB becomes larger and swirls, and the beam diameter increases, the beam will scan to the next scanning line or even to the next scanning line.

During the next scan, the signal current ■s is extremely small.1. [ru.

When the signal current Is becomes smaller, the characteristic curve T1 shown in FIG.
Accordingly, the beam current transport becomes smaller. Beam current■
Even if B becomes small and the beam diameter becomes <Yell.

In the range that has already been scanned, the signal current I
s is very small. As the scanning progresses further, it enters an area that has not been scanned with a thick beam. In the case of a bright screen, the signal current Is increases again.2. A situation comes around in which the beam current ①8 increases.

In the case of a bright screen, such an operation is repeated, so when viewed on a video monitor screen, a striped pattern consisting of repeated thick horizontal lines of white and black appears. This is the first normal shooting.
This is a phenomenon called ``.

In order to avoid such a situation, if the characteristic curves of the beam current 18 and the signal current I8 are set as T2 or T shown in FIG. 2, the "oscillation" phenomenon will disappear;
1) When the expression is full moon (the range of signal current becomes narrower).

When comet tails occur, the brightness ratio of the image cannot be maintained at a high level.

Conventionally, the output characteristics of the beam current control amplifier shown in Fig. 1 have a clipping characteristic of 1'l as shown in Fig. 3, and the maximum value of the 1st current is limited. A concrete example of this circuit is shown in Fig. 4. The signal current generated by the target surface 2 of the image pickup tube 1 ■ 8 digits, preamplifier;
After being amplified by
06.407) Rough emitter follower stage (408,
409), the final amplification stage (4]5,41.6,4
17.418) and then fed back to the grid electrode 5 of the image pickup tube 1.

The clip circuit 420 includes a diode 412 . connected to the base terminal of the final amplifier stage transistor 415 . Transistor 413. It is composed of a resistor 411 and a ril-variable resistor 414. This clip circuit 420 limits the maximum value of the emitter current of the output transistor I'I5. Base end of output transistor 415, 'r 423
+” E.

emitter ↓] power supply of resistor 416 (IllI terminal 12
This is achieved by limiting the electric current 1■= between 1 and −
2 3゜ In this circuit, terminal 421 - 123
Among? 1i) Below is the sliding terminal 422 of the variable resistor 414 and '
It is equal to the voltage vth between the power supply terminals 421.

The base-emitter saturation voltage of the clamp transistor 402 (■). F, s+ If the voltage at the output terminal 41 of the preamplifier 3 (input terminal of the beam current control amplifier 4) is .

The output characteristics of the beam current control amplifier 4 when

Dada L-9R406, R407, R4]6. R417 represents the resistance values of the resistors 406, 407, 416 and 417, respectively.

418 represents the voltage at terminal 418.

When will be clipped.

As explained above, in the conventional circuit, the output characteristics of the beam current control amplifier 11 have the characteristics shown in FIG. In this case, the relationship between signal current ■8 and beam current ■8 is, for example, T1 (solid line) and T1 of the characteristic curve shown in FIG.
, (dot-dash line), and the straight line (
A comet tail does not occur for video signals in a range smaller than the signal current ISI corresponding to the point where the broken line intersects with the dotted line.

This value ISI is at most about six times the reference signal current, and if a control range larger than this is attempted to be obtained, the above-mentioned "° oscillation" phenomenon occurs.

This invention solves the above problem and uses a signal current feedback control system with a simple configuration to photograph an object with a contrast ratio of 8 times or more. The purpose of this invention is to provide a circuit that is stable and operates smoothly.

In this invention, (the signal current obtained from the target I of the image tube is input to χ=i, and the output is linearly obtained without adding Vl.

1. Return to the grid electrode of the image pickup tube through a circuit with compressed characteristics. It controls the grid voltage.

That is, let the voltage at the input terminal of the amplifier constituting the current control @1 circuit be Vln.2. ■The voltage that is output to its output terminal. ut (where r is an index when the beam current of the image pickup tube is expressed as the voltage between the grid and cathode), or
Alternatively, this patent is characterized in that this characteristic is approximated by a polygonal line of the tool, and a beam current control amplifier having the characteristic is used to control the video signal, and then the grid electrode of the image pickup tube is controlled. A current control circuit is provided.

A circuit diagram of an embodiment of the present invention is shown in FIG. In this figure, the DC component is cut off from the input terminal 41 of the beam current control amplifier 40 via a capacitor 4:3, the current is limited by a 2° resistor 44, and then led to a diode 45. Dio-1...1
F on both ends of 50! Flτ is amplified via a linear amplifier 46, and the output terminal 42J controls the grid electrode 5 of the image pickup tube 1. By doing so, the beam current control amplifier 4 is reduced to a logarithm and the /ζ special condition is obtained, and it can be set so as to satisfy the condition of equation (8).

Another embodiment of the invention is shown in FIG.

The signal current that is omitted from the main plane 2 of the image pickup tube 1 is amplified by the preamplifier 3 and then sent from the input end of the beam current control amplifier 4 to the capacitor 401.

[- A clamp circuit composed of a transistor 402 passes through an emitter follower stage (403, 4071) and is led to an 11n width stage composed of a transistor 405 and resistors 406 and 407. This amplification stage (4f) 5,406,40
The output of 7) is the emitter follower stage m l1lE-1
408, but the
) and 411 rows are diode-1-7130 and -11---- variable resistor 431.
132. This I Karabaku Dan (4 (15, 40)
6, tI (17) Kushino J (Tsuchi Emi, Taforova Dan (4)
(18, 110411) -+lfl, 11 (anti-1
Trans/Sta old 5. via Tawo. Low resistance old 6 and 11
The width is 1 in the output 11N width stage consisting of 7, +lt
Connect the grid electrode 5 of the imaging tube 1 from the power terminal 42 to the ltl.
1 Sui).

The optical compression circuit 432 includes an amplifier stage (405, 406
, /+07) is used to approximate the voltage gain of two f-lines.

The characteristics of the circuit shown in the example 1 (+4) are Hino, Tonryu Sukei 1 amplifier 40 human power city 1'' 0 ■ 1n output voltage II - ■.

105. The collector-emitter saturation pressure of the clamp transistor 402 is determined by ■CES + the sliding terminal 422-tI6 of the variable resistor 431. Connect the L mo to 1 between the source side terminals 421 and vt
If we express the drop in the forward direction i- of h + diode/130 by Vl, J-j will be expressed as shown below.

In other words, 1) Human-powered type [13.

When.

2 Dada', R40fi, "4f17." Old 6. R71
17 are respectively Morimatsu, /106°4 ('17.4.16
and old 7's 1'' (the pile value, V418 is terminal -418
The voltage is high.

11) Furthermore, human power Ichikawa.

When.

3. Here, Rt indicates the resistance value of the variable resistor 4;

Assuming that the total resistance between the terminal 421 and the ground of the OT variable resistor 431 is R431, and the resistance between the sliding terminal 122 and the terminal 421 is t, T, 21 is given by the following equation.

Heem current, , , , 611 p,'t(II
Figure 8 shows the human output characteristics of IF; 1 device 4.

This 'Ichigoi Tomago''Ichiryu■8' and 'Heem''IchiryuTB'l'
The +54 thread is twisted (l;) in Fig. 9, and the signal '11L flow benefits -7, and the heel, thunder, flow is thick, and it depends on the angle.
7. Rainproofing the phenomenon of “°starting” and the maximum value of the signal current■8□
is a seventh grader in junior high school. "C-clip's attack house": You should be able to take a big shot. According to actual experiments, with this configuration and conditions, the phenomenon of "self-oscillation" does not occur, and comet tails occur stably even when used for video shooting with a contrast ratio of 8 times or more to 1-1. Another embodiment of the present invention is shown in FIG.

7. The signal current 8 from the target surface 2 of the image tube 1 is amplified by the preamplifier 3. This output is further connected to transistor 50:
Reversal at 3, Masuyuki Hatakeshi 2. Further, an inverting amplification 1-. Then, return the grid electrode 5 of the image pickup tube 1. This beam current control circuit 4 includes an l.
03 Koll/Kuta 1.゛3q value V1. Taioh 1・
5 (M.

Innovidance 505 Naro circuit and threshold V1. die 4-1
-'! ;(+7. Impeder> Z 5081 (parallel the circuit 'il p &'ii) -, t-ro. By doing this, the saturation flJN i'l- which is generated once by heat j, current control +1li 1 (signal in this case? i stream I8 and heeno, ′, -17. 1 of stream rB
94j is as shown in FIG.

The origin of the comet tail is IC! Itll nfll range can be wide. In addition, in 17, the specific circuit example of the uninvented beam current control method is in addition to the valley embodiment in 11i.

Existing gamma correction iE 11. It is easy to understand that even if an equivalent configuration is used, the same effect can be obtained.

According to the present invention, the beam current can be controlled without causing oscillation, and stable brightness and darkness can be achieved without sacrificing the simplicity of the circuit, which is a feature of the signal current feedback method. It is important to prevent comment tails from occurring in the 8-bit video.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventionally known signal current feedback system, Figure 2 is a characteristic diagram showing the relationship between the signal current and current of the conventional circuit, and Figure 3 is a diagram showing the relationship between signal current and current of the conventional circuit. Figure 4 shows the human output characteristics of a 4-inch width control device, No. +5-4: The figure is a circuit diagram of a conventionally used beam power section control beam increaser, and Figure 5 shows the beam current story 11 according to the present invention.
Figure 6 is a block diagram showing one embodiment of the present invention. Line 71 is a circuit diagram showing another embodiment of the present invention. Figure 8 is shown in Figure 7. Figure 9 shows the control of signal current ■8 and beam weighting ■8 when using a beam current control wholesale circuit with the human output characteristics shown in Figure 8. The characteristic diagram and FIG. 10 are circuit diagrams showing an embodiment of the invention. Figure 11: Foreign signal Daika-Gurino l'-Kasio isomorphism diagram,
FIG. 12 is a control characteristic diagram of signal type 7'MIH and beam current ■B when using a beam current control circuit having the human output characteristics shown in FIG. 1'i and FIG. 11. 1: Image pickup tube, 2: Target unit, 3: Preamplifier, 4
: beam current control amplifier, 44: resistor, 45: diode, 46 bilinear amplifier, 432: profit compression circuit. Agent Patent Attorney Susuki 1) Toshiyuki 161

Claims (1)

[Claims] ■) A signal current cutter from a target of an image pickup tube. Due to the above-mentioned image pickup tube grid canot dark time! tV
GK is a quadratic formula (approximation by two or more broken lines (including the v formula)
It's a relationship like that. (Exponent when the morbidity is caused by the voltage between the grid and the grid). An automatic beam current control method characterized by controlling the beam current so as to satisfy the following. 2) Signal current from the target of the image pickup tube. In the signal current feedback control system @+ circuit, which returns to the grid electrode of the Hiki image tube and controls the grid voltage, the signal current is fed back to the grid electrode of the image tube, and the input/output characteristics are close to each other.
1 number field reduction special 1'-1t ('-'' 1 piece,
Ryo i! Be L with the approximation reduction characteristic 111-)
'fit f+fi Feed back to the clid electrode of the previous quadrant tube via the control amplifier rJ17. and 1-, a beam current control circuit with one feature.