JP2601257B2 - Imaging device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an imaging device having an automatic tracking type white balance device.

(Prior art)

For a video camera having a conventional automatic tracking type white balance device, for example, an external colorimetric sensor adapted to the spectral sensitivity characteristics of an image sensor is used, and color temperature information is calculated by performing an output from the external sensor. And controlling the gain of the color signal at the color temperature to adjust the white balance (hereinafter referred to as “white balance”).

However, when the color temperature greatly deviates from the set value, it is conceivable to place a color temperature correction filter such as CCA or CCB in front of the imaging sensor because the dynamic range and SN ratio of the gain control amplifier are severe.

However, in this case, since the color temperature information from the external colorimetric sensor is intact, there is a disadvantage that the output signal causes a color shift such that the output signal becomes blue or red.

〔Purpose〕

The present invention has been made in view of the above-described drawbacks, and provides an imaging apparatus capable of appropriately controlling the gain of a color signal system by an external colorimetric sensor when a color temperature correction filter is inserted into an imaging optical system. The purpose is.

〔Example〕

Hereinafter, the principle of the present invention will be described with reference to FIG. 1 and FIG.

First, referring to the block diagram shown in FIG. 1, 1R and 1B are colorimetric sensors (light-receiving sensors for colorimetry) of R signal and B signal, respectively, and color filters Rf and Bf and photodiodes F and F are connected to each other. From 2 is a division circuit, 3 is a gain control signal generation circuit, 4f is a color separation filter of an optical system,
4C is a CCD integrated with the filter 4f, 5 is a sample holder (hereinafter referred to as "S / H"), and 6R, 6G and 6B are S / H for color separation.

7R, 7G, 7B are color signal LPFs (low-pass filters), 8R, 8B are R signal and B signal system gain control amplifiers, 9 is γ (average slope of photoelectric conversion characteristic curve) correction process, etc. Circuit, 10 is NTSC encoder, Ks, Kr, Kb is CC
The B filter driving device, fs, fr, fb, is a CCB filter for color temperature correction. SW is a switch.

 Next, the operation will be described.

Through the color separation filter 4f of the optical system in the imaging system
The image information obtained from the CCD 4C is sampled and held by the S / H 5 and the R, G, and B signals by 6R, 6G, and 6B, respectively, and passes through the color signals LPF 7R, 7G, and 7B to become an electric signal of a desired band. . Of these, the R and B signals pass through gain control amplifiers 8R and 8B to adjust the white balance, perform non-linear signal processing such as γ correction in the process circuit 9, and pass through the NTSC encoder 10
It is sent out as an NTSC signal.

On the other hand, the R and B signals obtained by the colorimetric sensors 1R and 1B are:
An R / B signal is generated by the division circuit 2, and a gain control signal is generated in the gain control signal generation circuit 3 in accordance with the color temperature correction curve shown in FIG. 2 to control the gains of the gain control amplifiers 8R and 8B. The actual gains of R / G and B / G are inverse values of the curve shown in FIG.

Now, when the switch SW is closed, the signal is transmitted to the CCB driving devices Ks, Kr, Kb, and the CCB filters fs, fr, fb are provided before the color separation filters 4f and Rf, Bf of the optical system. It is inserted by electromagnetic drive, spring drive, or the like. Incidentally, since the CCB filters fs, fr, and fb all have the same spectral characteristics, the color temperature can be corrected without providing a special correction circuit.

Therefore, in this embodiment, the dynamic range of the gain control amplifier for white balance may be small, and therefore, there is an effect that the SN ratio of the color signal is also improved.

Next, an embodiment of the present invention will be described with reference to FIG. 3 and FIG.

In this embodiment, the CCB filter is inserted into both the imaging system and the colorimetric system in the examples of FIGS. 1 and 2, but the number of movable parts is reduced to improve reliability. In order to increase the size and reduce the size of the apparatus, the CCB filter is inserted only in the image pickup system, and the colorimetric system is electrically corrected. That is, the CCB filters fr and fb and the driving device K
r, Kb and switch SW are removed, and a dividing circuit 2
From the CCB filter driving device Ks via a newly provided comparator 11.

Next, the feature of the operation will be described. The image information obtained from the CCD 4C through the color separation filter 4f of the optical system in the imaging system operates almost in the same manner as in the case of the example of FIGS.
The signal is sent out as an NTSC signal. On the other hand, in the colorimetric system, as shown in the color temperature correction curve graph of FIG. 4, when the temperature falls below the set color temperature T (゜ K), that is, R / B When the signal exceeds the relative value a, a signal is output from the comparator 11, and the CCB filter driving device Ks operates to be inserted before the color separation filter 4f, and at the same time, the gain control amplifier 8
The R and 8B control signals are switched in the gain control signal generation circuit 3. The gains of the amplifiers 8R and 8B are R / G and B in FIG.
The gain may be such that the reciprocal of the / G curve can be obtained.

Therefore, in this implementation order, not only the same effects as in the examples of FIGS. 1 and 2 can be obtained, but also because the CCB filter for color temperature correction is inserted only in the imaging system, the number of movable parts is small. Thus, the size of the apparatus could be reduced.

In addition, color temperature correction is performed based on the output from the colorimetric sensor.
Since the CCB filter is inserted into the imaging system and the profit control amplifier is controlled at the same time, all operations are performed automatically, so that the photographer does not need to perform any special operation.

(Effect)

As described above, the present invention provides a color temperature correction filter for an optical system based on a color temperature detection signal from a colorimetric sensor instead of inserting a color temperature correction filter having the same characteristics into an optical system and a colorimetric system of an imaging system. Since the gain control signal of the color signal system can be switched with the insertion of the color signal, the dynamic range of the gain control amplifier for white balance may be small, and the SN ratio of the color signal is also improved. This has the effect.

[Brief description of the drawings]

FIG. 1 is a block diagram of the principle of the present invention, FIG. 2 is a graph of a color temperature correction curve, FIG. 3 is a block diagram of an embodiment, and FIG. is there. 1R ... Colorimetric sensor for R signal 1B ... Colorimetric sensor for B signal 3 ... Gain control signal generation circuit 4f ... Color separation filter for optical system fs, fr, fb ... CCB filter 11 ... Comparator

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masao Suzuki 770 Shimonoge, Takatsu-ku, Kawasaki Canon Inc. Tamagawa Plant (72) Inventor Akihiko Tojo 770 Shimonoge Takatsu-ku, Kawasaki Canon Inc. Tamagawa Plant (56) References JP-A-59-163994 (JP, A)

Claims (1)

(57) [Claims] 1. An optical system for forming an optical image, a color imager for converting an optical image formed by the optical system into an electric signal, and a gain of a plurality of color signals obtained from the color imager. Gain control means for controlling the colorimetric light-receiving sensor different from the imaging means; detecting means for detecting that the output of the colorimetric light-receiving sensor has exceeded a predetermined color temperature range; A color temperature correction filter driving unit that inserts a color temperature correction filter into the optical system based on the output of the unit; and adjusting the white balance by varying the gain of the gain control unit according to the output of the colorimetric light receiving sensor. The gain of the gain control unit is changed by inserting the color temperature correction filter into the optical system by the color temperature correction filter driving unit based on the output of the detection unit. An imaging apparatus having a gain control signal generating means for switching previously with different gains to insert a degree correction filter, the.