JPS6213189A - Signal processing device and image pickup device - Google Patents

Abstract

PURPOSE:To obtain a device formed easily with a point sequential signal level by providing a color system automatic gain control means applying automatic gain control to plura color signals before processing respectively and a luminance signal forming means using the said color system automatic gain control means so as to apply point sequential to the color signal thereby forming the luminance signal. CONSTITUTION:Since an AGC circuit for color signal is given to other system than a switch circuit 48, the deterioration in the frequency characteristic in the AGC circuits 45-47 does not give effect on a high frequency luminance signal of the switch circuit 48. Since the AGC circuit 49 for Y signal is provided before a KNEE circuit after the Y signal is synthesized by switching, the characteristic of the AGC circuit 49 can be at Y band (e.g., 6MHz) and the current of the AGC circuit 49 is suppressed lower and the circuit integration is facilitated. Further, since the KNEE circuit is provided after the clamp circuit is provided after the AGC circuit 49, the gain of the AGC circuit is fluctuated and the effect on the KNEE characteristic is less even with DC fluctuation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an imaging apparatus using a signal processing apparatus and an imaging device, and more particularly to a signal processing apparatus for reducing aliasing distortion and an imaging apparatus equipped with the same. It is something.

(Prior Art) A conventional example will be explained by taking as an example an imaging device using a CCD type imaging device, as shown in FIG.

The image sensor shown in FIG. 10 is a frame transfer type COD. First, the information charges photoelectrically converted in the imaging unit 1 corresponding to each color filter of the stripe filter are driven by a driving pulse φP.
By I and φPS, the data is transferred to the memory part 2 at high speed during the vertical retrace period of TV synchronization. Further, the information charges accumulated in the memory part 2 are transferred to each stripe filter per vertical transfer for one horizontal line, and the information applied to each stripe filter is transferred to the horizontal shift register SR.
It is distributed and transferred to I, SR2, and SR3.

That is, as shown in FIG.
3R3, horizontal shift register SRI,
R, G, and B signals are output from SR2 and SR3, respectively. Therefore, registers SRl, SR2, and SR3 constitute separation means for separating color signals.

FIG. 12 is a block diagram of a signal processing circuit for signals read out from the CCD. An imaging device 10 (for example, a CCD) driven by a clock IC 30 and a driver 20
), for example, a color filter as shown in the figure is pasted, and its output signals are separately obtained as R, G, and B signals corresponding to the color separation filters. This signal is subjected to DC regeneration in the clamp circuit 40 and guided to the next stage 50, where the R, G, and B signals are brought to the same level.

It is even better to use a feedback clamp circuit that feeds back the DC potential of the input signal of the switch circuit 6o to the clamper as the clamp circuit. Next, the output signal of this AGC circuit 50 is processed by a switch circuit 6°, which is a sequential means for forming a brightness signal in the next stage, and a circuit that processes signals such as normal gamma correction or white clip, and converts them into an NTSC signal. The encoder circuit 7o is connected to the encoder circuit 7o. Next, the operation of the switch circuit 6o will be explained based on FIG. 13. S3 is the output signal of the CCD shown in FIG. In this example, it is assumed that the drive pulse for the horizontal shift register is a three-phase drive pulse equivalent to the signal waveform shown in FIG.

These signals Sl, S2 . S3 is the switch circuit control signal 5
WR, 5W-G, 5W-Bt7) When the signals are extracted by switch+pulse and the extracted signals are added, a luminance signal shown as Y in the figure is obtained. That is, the same signal Y as the spatial sampling of the color separation filter is obtained, and the resolution is very good. If a luminance signal is generated by extracting and adding only the portions necessary as a luminance signal by switching in this way, noise will not be added and there will be no deterioration of the S/N ratio.

(Problems to be solved by the present invention) In the conventional example below-1], as shown in FIG.
(7) Three systems of output signals Sl, S2. The delay characteristics and frequency characteristics of the clamp circuit 40 and AGC circuit 5o are extremely important for S3.

That is, according to experiments, the delay characteristic must be within ±20 ns, and the cutoff of the frequency characteristic must be 10 MHz or higher.

However, these AGC circuits generally have extremely poor delay characteristics and frequency characteristics.

For this reason, there was a drawback that the MTF characteristics deteriorated, leading to a decrease in resolution.

Conversely, in order to improve the delay characteristics and frequency characteristics of this AGC circuit, a significant increase in circuit current or special ±
There is a drawback that the IC process requires a complicated IC circuit configuration.

Furthermore, if the AGC circuit is provided in the process circuit after, for example, the gamma correction circuit, there is a problem in that fluctuations in DC components caused by the AGC circuit cause clip level errors in white clips and dark clips.

SUMMARY OF THE INVENTION An object of the present invention is to overcome the drawbacks of the prior art and provide a signal processing device and an imaging device that can easily form point-sequential signal levels.

[Means for solving problems]

The signal processing device of the first invention of the present application includes a color system automatic gain control means that performs automatic gain control on each of a plurality of color signals before processing them, and a color system that converts the color signals into point sequence by the color system automatic gain control means. It has a luminance signal forming means for forming a luminance signal.

Further, the imaging device of the second invention of the present application includes an imaging means, a color system automatic gain control means for automatically controlling the gain of each of a plurality of color signals obtained from the imaging means, and an automatic gain control means for controlling the automatic gain by the color system automatic gain control means. a luminance signal forming means for dot-sequentializing the plurality of color signals before being controlled to form a luminance signal; processing the plurality of color signals via the color system automatic gain control means and the output of the luminance signal forming means; and processing means for processing.

[For production]

In the invention of the present application, each of the inputted color signals is automatically gain-controlled by the automatic control means so as to have an appropriate signal level. Since this is performed before the color signal processing, the automatic gain 1! is performed by the clamp processing performed first in the processing circuit. ! DC level fluctuations caused by control are canceled and will not have an adverse effect on subsequent γ correction, etc.

On the other hand, since the luminance signal is obtained by dot-sequentializing the color signal that does not go through this automatic gain control circuit, it is possible to obtain a high-frequency luminance signal without being affected by the deterioration of frequency characteristics that occurs in the automatic gain control. Can be done.

Also, when converting to an IC, it has a built-in colored yarn automatic gain control circuit as a signal processing device, so the LP can be used before the clamp circuit.
F etc. can be easily inserted.

(Examples) The present invention will be described below based on Examples. FIG. 1 is a diagram showing an example of the configuration of an imaging device according to the present invention.

In the figure, 3 is the first optical system, 4 is the aperture, 5 is the second optical system,
1O is a frame transfer type COD shown in FIG. 7 as an imaging means, and 20 and 30 are a clock driver and a clock generator, respectively. 31 is a sample and hold circuit, horizontal shift registers SRI, SR2, S
This is to increase the duty of the signal components of each output of R3.

32 is a color separation circuit as a signal processing device according to the present invention, which adjusts the gain of each color signal and adjusts the high-frequency luminance (Y
) for forming signals.

33 is a low pass filter (LPF) that passes components of 4 MHz or less for the Y signal, and passes components of 0.5 MHz or less for the RlG and B signals.

A process circuit 34 serves as a process means and applies various corrections such as clamping, gamma correction, white clipping, etc., and also forms a color difference signal.

35 is an encoder circuit, Y, (RY), (B-
Y) is modulated and multiplexed.

The output of the color separation circuit 32 is led to an ALC (automatic aperture) circuit 36, which performs servo control so that the amount of light input to CC1') falls within the dynamic range of the COD.

FIG. 2 is a diagram showing an example of the configuration of the color separation circuit 32 of this embodiment.

54-56 are transistors for inputting R, G, and B, respectively; 57-59 are bypass capacitors for removing high-frequency noise; 37-39 are clamp circuits; 41-43 are blanking circuits; 44a;

44b is a gain control circuit as a first gain control means, and 45 to 47 are A as color system automatic gain control means for automatic gain control of R1G and H signals, respectively.
GC circuit, 48 is gain controlled R, G, B
A switch circuit serves as a luminance signal forming means for forming point-sequential luminance signals by switching signals according to the arrangement of color filters, and 49 is a luminance system automatic gain control for automatically controlling the output gain of the Y signal. 51 is a clamp circuit for clamping the Y signal; 52 is a KNEE circuit as a non-linear conversion means for performing non-linear conversion such as level compression; 53 is an AGC circuit;
This is a detection circuit that controls the gains of circuits 45 to 47 and 49. 33a is a 4 MHz LPF, 33b
is 0.5MHz(7)LPF-v'.

Further, 61 is a NAM circuit that performs non-additive addition of the outputs of the blanking circuits 41 to 43;
The output is input to a high degree suppression circuit in the process circuit 34, and is configured so that the color signal is suppressed when at least one of the R, G, and H signals is saturated.

62 is an A/D converter which controls the R gain control circuit 44a and the B gain control circuit M44b by its output.

By doing so, the configuration of each gain control circuit becomes easy, and the driving power supply for the circuit becomes small.

63 is a control circuit, and the output of the control circuit is a digital signal.

Further, the output of the control circuit 63 and the output of the A/D converter 62 are connected by a wired-OR circuit. This will be discussed later.

In this embodiment, RGB AGC circuits 45 to 47 are provided at locations separated from the Y system.

Therefore, the characteristics of this AGC circuit are the color band (for example, I M
Hz). Therefore, since there is no need to increase the frequency of the AGC circuits 45 to 47, the manufacturing process does not become complicated when integrated into an IC.

Further, the circuit driving current can be reduced.

Furthermore, since the characteristics of the Y-system AGC circuit 49 and the R, G, and B-system AGC circuits 45 to 47 can be set independently as appropriate, functions such as automatic color suppression at low luminance can be provided by these AGC circuits. be able to.

Further, since the AGC circuit is provided in the color separation # circuit before the process circuit, the gamma correction, white clip, dark clip characteristics, etc. in the process circuit do not change even if the gain changes due to the AGC circuit.

This is because fluctuations in the DC level caused by the AGC circuit are canceled by the clamp circuit inserted at the beginning of the process circuit.

Therefore, when the AGC circuit is provided in front of the process circuit as in this embodiment, there is an advantage that the permissible value of DC level fluctuation due to the AGC circuit is increased.

In addition, in the embodiment, T and PF are inserted between the first-stage clamp circuit of the process circuit and the color #@ circuit, so if such an AGC circuit is inserted before the clamp circuit in the process circuit, the process circuit When converting into an IC, the capacitor for this LPF must be externally attached to the IC, which has the drawback of increasing the number of IC pins by 2 pins, but as in this example, All of these problems can be solved by inserting an AGC circuit for color signals into the color #IC in front of the process IC.

This point is also one of the features of this embodiment.

Furthermore, in this embodiment, the AGC circuit for color signals is included in a separate system from the switch circuit 48, so the AGC circuits 45 to 4
There is no vehicle in which the deterioration of the frequency characteristics in the switch circuit 48 adversely affects the high-frequency luminance signal in the switch circuit 48.

Further, according to this embodiment, after Y is synthesized by switching, the AGC circuit 49 for Y is provided before the KNEE circuit, so that the characteristics of the AGC circuit 49 are in the Y band (for example, 6
MHz), therefore, the current of the AGC circuit can be kept low, and integration into an IC is extremely easy. Nu, A
KNEE after installing a clamp circuit after the GC circuit 49
Since the circuit is provided, the gain of the AGC circuit fluctuates, and even if there is a DC fluctuation, the influence on the KNEE characteristics is small.

That is, the permissible value of the DC level fluctuation due to the AGC circuit is increased, and the bending point of the characteristic curve (broken line) of the KNEE circuit is stabilized.

FIG. 3 is a diagram showing an example of the configuration of the detection circuit 53 in this embodiment, which includes a smoothing circuit 531, a comparison amplification circuit 532, a reference power source 533, and a variable limiter circuit 534.

The input video signal is smoothed by the smoothing circuit 531, and this smoothed signal is compared with a reference level. The gains of AGC circuits 45 to 47.49 are controlled according to this comparison output,
The comparison output is controlled to be zero. Here, the limiter circuit 534 is for saturating the comparative output when it reaches a certain L limit, and the gain control range can be variably controlled by the exposure compensation circuit.

The exposure compensation circuit works to narrow the gain variable range of the AGC circuit during exposure compensation or manual aperture adjustment.

As a result, even if the aperture value is corrected during exposure correction or manual aperture, it will not be reversely corrected by AGC.
Exposure compensation effect is improved.

Moreover, compared to the one that completely fixes the gain of the AGC circuit, the aperture fa1 using normal ALC from the exposure compensation state
It has the effect of completely eliminating any discomfort when returning to the 1st state.

Furthermore, in addition to controlling the gain variable range of the limiter circuit 534 by the exposure compensation circuit 535 as in this embodiment,
Since the configuration is such that it can also be controlled by input from the terminal 536, the gain characteristics of the entire color separation process circuit can also be controlled by this terminal 536.

Also, one of the features of this embodiment is that the output of the detection circuit 53 is used to control the Y system AGC circuit 49 and the AGC circuits 45 to 47 for each color thread.
One of the characteristics of this is that the control of the gain variable range is performed in conjunction.

With this configuration, it is possible to eliminate infinitesimal variations in each AGC circuit, and it is possible to suppress the generation of false color signals.

FIG. 4(a) is a diagram showing an example of the configuration of the limiter circuit 534, in which Q1"Q3 is a transistor.

537 is a signal input terminal, 538 is a limit value control input terminal, and 539 is a signal output terminal.

FIG. 4(b) is a diagram showing the characteristics. The voltage output from the output terminal 539 changes almost linearly depending on the voltage input to the terminal 537, but this input voltage is the voltage input to the terminal 538. When the voltage exceeds the level, the output voltage at the terminal 539 becomes saturated.

Next, FIG. 5 shows the gain control circuit 44a.

This figure shows a configuration for controlling the gain of the gain control circuit 44b.
The gain of b is controlled by a digital signal, and a signal corresponding to the difference signal between the average value of the R-Y and B-Y color difference signals of the process circuit 34 and the reference value is used as a white balance circuit as a white balance control means. 540. Also, a gain control circuit 44a.

44b is used to reduce the difference signal, and this analog control signal is updated only when a white balance setting switch (not shown) is turned on when photographing a white subject, and when turned off, the previous value is held until the next time it is turned on. .

Incidentally, such a white balance circuit was developed, for example, by the
It is known as No. 8-14369.

Also, the output of the white balance circuit is R within the process cycle.
It also controls the gain of the and B channels.

The A/D converter 62 is connected to this white/<lance circuit 5.
40 outputs are A/D converted and the gain ratios of the R, G, and B channels are set to predetermined values. With this configuration, the R2G and B signals after gain adjustment are in accordance with the correct color temperature, and it is possible to form a high-frequency Y signal with less moiré even for an almost achromatic subject.

Furthermore, conventionally, the gain is varied by an analog control signal as a gain control circuit, but in order to form a high-frequency Y signal as in this embodiment, this gain control circuit 44a is used.

If a conventional analog type gain control circuit is used as 44b, the drive current must be increased in order to improve delay characteristics and frequency characteristics, and a special process must be used as an IC process.

Therefore, in this embodiment, the gain control circuit at the stage before the switch circuit 48 is controlled stepwise by a 2-bit digital control input, and the gain is adjusted discontinuously. Therefore, the circuit configuration is extremely simple, and the driving current can be extremely small.

Further, in this embodiment, the gain control circuits 44a, 4
The input end of the control signal of 4b is connected to the A/D converter 6.
Not only is it connected to the output of No. 2, but it is also led to the external terminal 63a through a wired-OR connection. Therefore, this external terminal 63
By connecting a bypass capacitor to a, switching noise in the output of the A/D converter can be removed.

Further, as shown in FIG. 5, a control circuit 63 is connected, and this control circuit 63 controls the gain control circuits 44a and 44b.
can also be controlled.

The control circuit 63 inputs the Y signal, detects its average level, and outputs a low illuminance detection signal LL when the average level falls below a predetermined value, thereby providing a signal between the white balance circuit and the A/D converter. The gate provided at the A/D converter is closed to set the input to the A/D converter to zero.

Also, at this time, the gain control circuit 44a.

The gain of 44b is made relatively low. This suppresses noise during low illumination, improves S/N, and increases resolution.

Therefore, when the subject is dark, it is possible to obtain a high-quality image with priority given to S/N over moiré and the like.

Next, FIG. 6 is a diagram showing a configuration example of the A/D converter 62 and the wired OR section 541.

543 to 545 are comparators, and the control input CI from the white balance circuit 540 is controlled by each comparator 543 to 545 to each reference value ■1 to 545 of the reference power source 542.
Each is compared with V3.

Here, V>V2>V3.

546.549.550 is inverter, 547 is ANT
) gate, 548 is an OR gate, and Q4 and Q5 are transistors. With this configuration, the levels of outputs 04 and 05 relative to the level of CI are as follows.

Therefore, as the level of CI decreases, 04°05 becomes 1.
The output changes in the order of 1, 10, 01, 00.

According to this 2-bit data, the gain control circuits 4.4a and 44b each switch the gain in four stages.

In this way, the frequency characteristics of the gain control circuits 44a and 44b before the switching circuit 48 are important;
The gain balance does not have to be so strict.

Therefore, by using a gain control circuit with a simple configuration as in the present embodiment, it is possible to easily obtain a substantially sufficiently high-frequency Y signal.

- Since the white balance of the old color signal system must be highly accurate, in this embodiment, it is performed in the process circuit separately from the white balance of the Y system.

Next, FIG. 7 is a block diagram of the process circuit, and 341
are Y and R input by the clamp circuit.

Adjust the DC levels of G and B signals to the reference level. 34
2 is a γ correction circuit that performs a predetermined nonlinear transformation. 343 is a white clip circuit which clips signals below a predetermined level. 344 is a dark clip circuit that clips signals below a predetermined level. 345 is a matrix circuit and Y
, R, G, and H signals to calculate Y, (RY), (
B-Y) is formed.

Further, reference numerals 541 and 542 are gain control circuits serving as second gain control means for color signals, and the gain is controlled by the output of the white balance circuit 540 described above.

As mentioned above, the output R- of the white balance circuit 540
The average values of Y and B-Y are compared with a predetermined reference value, and signals corresponding to the differences are output.

Each gain control circuit 541, 542 operates so that the signal corresponding to this difference becomes zero.

Figure 8 is a diagram showing an example of the configuration of this gain control l1111M541゜542, where Q6 to Qll are transistors, R1 to R5, RL are resistors, E is a power supply, and SIG
IN is the signal input terminal, SIG OUT is the signal output terminal,
C0NT IN is the control end.

Assuming that the SIG IN input is constant, QIO acts as a constant current source, and Q,6. The sum of the currents flowing through each Q7 flows through QIO.

Therefore, when the voltage on C0NT IN increases. The current in Q7 increases and the current in Q6 decreases. When the current in Q7 increases, the current flowing through RL increases and the gain increases.

On the other hand, when the current in Q7 increases, the current in Q8 also increases.

On the other hand, since the potential at the connection point of R2 and R3 is constant, Qll is a constant current source and 1. I'm working.

Therefore, as the current in Q8 increases, the current in Q9 decreases. As a result, even if the current of Q7 increases, the DC level of 5IGOUT is corrected to be constant.

With such a configuration, extremely accurate gain control is possible according to the level of C0NT IN.

1. On the contrary, in order to improve the frequency characteristics, a large current must be passed, and the Tc process is complicated.

Figure 9 shows the gain control) Iy times m 44. a.

44b, R6-R8 are resistors, Q, 1
2 to Q, l3 is a transistor, C0NTA.

C0NTB is a gain control input terminal. R
7, Q, 12 and R8, Q, 13 constitute a two-stage ladder connection.

In this case, the relationship between the C0NT A and C0NT Bcn inputs and the gain is as follows.

With such a configuration, a gain control circuit with sufficiently good frequency characteristics can be obtained.

In the embodiment, a two-stage ladder connection is used, but a three-stage ladder connection may also be used. If the number of stages is four or more, the frequency characteristics deteriorate, and therefore it is not suitable for the switch operation of the switch circuit 48.

The gain can be controlled in 4 ways in the case of 2 stages, and in 8 ways in the case of 3 stages.
Although it can only be done in a certain way, it has been confirmed that this is sufficient for practical use since gain control during moderation signal formation does not require particular precision.

〔Effect of the invention〕

- automatic gain control according to the present invention as explained above.

Since the luminance signal is obtained by dot-sequentializing the color signal without passing through the control circuit, it is possible to obtain a high-frequency luminance signal without being affected by the deterioration of frequency characteristics that occurs in the automatic gain control.

Furthermore, since each color signal is automatically gain controlled before being processed in a system different from the luminance signal system, the clamp processing performed first in the process processing circuit
DC level fluctuations caused by the automatic gain control are canceled and will not have an adverse effect on subsequent γ correction, etc.

Moreover, since the automatic gain control of the colored yarn is performed before processing, when the signal processing device is integrated into an IC, a low-pass filter can be easily provided between the process processing circuit and the signal processing device.

[Brief explanation of drawings]

Fig. 1 is a structural survey of the imaging device of the present invention, Fig. 2 is a structural survey of a color separation circuit, Fig. 3 is a structural survey of a detection circuit, Fig. 4 is a structural survey of a limiter circuit, and Fig. 5 is a white Figure 6 is a diagram showing the configuration for balance control, Figure 6 is a configuration diagram around the A/D converter circuit, Figure 7 is a survey of the configuration of the process circuit 34, Figure 8 is a survey of the configuration of the gain control circuit 541, 542, Figure 9 shows a gain controller)Iy circuit 44a. Figure 10 is a diagram showing an example of an image sensor, Figure 11 is a diagram showing the relationship between a color filter and a horizontal register, Figure 12 is a configuration diagram of a conventional imaging device, and Figure 13 is a diagram showing the formation of a luminance signal. It is an explanatory diagram of a method. 44a, 44b---gain control circuit. 45-47--AGC circuit, 48-m-switch circuit, 32-m-color separation circuit. 34-m-process circuit. 1shi8'B Explosionφ ri 0

Claims (2)

[Claims] (1) color system automatic gain control means for automatically controlling the gain of each of a plurality of color signals before processing them; a luminance signal forming means for dot-sequentializing the color signals to form a luminance signal using the color system automatic gain control means; A signal processing device having: (2) an imaging means, a color system automatic gain control means for automatically controlling the gain of each of the plurality of color signals obtained from the imaging means, and the plurality of color signals before being subjected to automatic gain control by the color system automatic gain control means. An imaging device comprising: a luminance signal forming means for dot-sequentializing a luminance signal to form a luminance signal; and a processing means for processing a plurality of color signals via the color system automatic gain control means and the output of the luminance signal forming means.