JPS6350914B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a color mixture correction circuit used in a single-chip color camera or the like.

BACKGROUND ART In the field of home video cameras, single-chip color cameras that use solid-state imaging devices such as CCDs (charge-coupled devices) instead of image pickup tubes have become commercially available, and their future development is attracting attention. This type of single-chip color camera has many excellent features, such as low noise, high sensitivity, excellent color reproducibility, and uniform image quality. In particular, the color reproducibility depends on the overall spectral sensitivity characteristics of the solid-state imaging device and the color transmission filter used in front of it, so materials must be selected carefully.

FIG. 1 shows an example of the spectral sensitivity characteristics of a single-chip color camera. In the figure, the three peaks represent blue, green, and red in descending order of wavelength, but the overlap between the bases of the peaks, that is, the area of the diagonal line where the two colors are mixed, is as large as possible. Preferably small. However, in reality, a certain amount of overlap is unavoidable, and if this overlap in spectral characteristics is left uncorrected in the circuit, color mixture will occur, for example, a screen that should appear green may have a bluish or reddish tinge. This has the disadvantage of worsening color reproducibility.

DISCLOSURE OF THE INVENTION The present invention eliminates the above-mentioned drawbacks, and uses a differential amplifier to process color signals obtained by an imaging means including a color transmission filter, a solid-state imaging device, etc., before passing through a process amplifier circuit. It is an object of the present invention to provide a color mixture correction circuit that enables sufficient color mixture correction for a wide range of changes in the color temperature of an object by performing color mixture correction without the need for troublesome correction using a matrix circuit.

To achieve this object, the present invention comprises an imaging means for obtaining three primary color signals from an object, and a differential amplifier for amplifying each of the three primary color signals obtained by the imaging means, and at least one of the differential amplifiers. Color mixture correction is performed by supplying a different primary color signal regarding another color to the primary color signal regarding one color amplified by the differential amplifier at a predetermined ratio from a differential amplifier other than the one differential amplifier. The structure is as follows.

According to the present invention, the three primary color signals are extracted from the information regarding the object obtained from the solid-state image sensor through the color separation circuit, and the color mixture is corrected using the differential amplifier before the three primary color signals are passed through the process circuit amplifier. Because of this, accurate color mixture correction is possible without using complex matrix circuits, etc., and this allows sufficient correction for color temperature changes of a wide range of objects. Also, as a differential amplifier,
For example, by using a pair of common emitter transistors combined with an emitter follower type transistor, both input and output resistances can be reduced, resulting in low noise and easy connection to subsequent circuits. be effective.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to FIG. FIG. 2 is a circuit diagram showing an embodiment of the color mixture correction circuit of the present invention.

In FIG. 2, the color mixture correction circuit 1 is built into a single-chip color camera 2. As shown in FIG. The image of the subject 4 captured by the objective lens 3 of this single-panel color camera 2 is converted into time-series pixel signals by a solid-state image sensor 6 on which a mosaic-like color transmission filter 5 is pasted, and then color separation is performed. A circuit 7 separates the signal into three primary color signals.

The color mixture correction circuit 1 is connected to the color separation circuit 7, and includes three differential amplifiers 8, 9, and 10 corresponding to each separated primary color signal. Note that 11 is a low-pass filter that removes sampling noise generated in the color separation circuit 7.

Each differential amplifier 8, 9, 10 has a pair of transistors Q ₁ and Q ₂ for inverting input and non-inverting input whose emitters are commonly connected, and after amplifying the inverted output obtained from the collector of transistor Q ₁ . It consists of an emitter follower type transistor _Q3 which feeds back to the base of the same transistor _Q1 .
Therefore, the differential amplifiers 8, 9, and 10 all have low input resistance and low output resistance, and are therefore resistant to noise and easy to connect with subsequent circuits.

Note that the base of the transistor _Q1 serves as one input terminal of each of the differential amplifiers 8, 9, and 10, and is supplied with a color signal of negative polarity. Also, transistor Q ₂
The base of is the other input terminal of each differential amplifier 8, 9, 10, and a reference signal is supplied thereto.

Here, in this embodiment, a part of the green signal is applied to the bases of the transistors _Q2 of the differential amplifiers 9 and 10, respectively, and the reference signal level of the differential amplifiers 9 and 10 is changed by the amount necessary for color mixture correction. I try to let them do it. The amount of change required for this color mixture correction can be set to a desired value depending on the resistance values of variable resistors R ₉ and R ₁₀ in the green signal line connected to the base of transistor Q ₂ . It's summery.

In this way, the color mixture correction circuit 1 having the above configuration
In this method, the information regarding the subject obtained by the solid-state image sensor 6 is extracted through the color separation circuit 7 to extract the three primary color signals, and the three primary color signals are immediately subjected to color mixture correction. Compared to the conventional method in which color mixture correction is performed in a conventional method, sufficient color mixture correction can be performed for a wide range of color temperature changes of objects.

In the above embodiment, the green signal is subtracted from the other red and blue signals as the color mixture correction signal, but when color mixture is to be corrected, the red signal and the blue signal are used as the subtraction signals.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing an example of the spectral sensitivity characteristics of a single-chip color camera, and FIG. 2 is a circuit diagram showing an embodiment of the color mixture correction circuit of the present invention. 1... Color mixture correction circuit, 2... Single plate color camera, 3... Objective lens, 5... Color transmission filter,
6... Solid-state image sensor, 7... Color separation circuit, 8,
9,10...Differential amplifier.

Claims (1)

[Claims] 1. Consisting of an imaging means for obtaining three primary color signals from a subject, and a differential amplifier for amplifying each of the three primary color signals obtained by the imaging means, at least one of the differential amplifiers A color mixture correction is performed by supplying a primary color signal regarding another color different from the primary color signal regarding the one color to be amplified at a predetermined ratio from a differential amplifier other than the one differential amplifier. color mixture correction circuit. 2. The primary color signal regarding the different other color is green, and the green primary color signal is supplied to a differential amplifier that amplifies the red and blue primary color signals at a predetermined ratio, thereby performing color mixture correction. A color mixture correction circuit according to claim 1.