US 5,512,948 A · Negative-image signal processing apparatus

Abstract

The white peak level and black peak level of each of three types of color signals R, G and B obtained by picking up a negative image are detected. The amplitudes and levels of the signals are adjusted in such a manner that the white peak levels of the color signals R, G and B coincide as well as the black peak levels of these color signals. Signals representing the detected white peak and black peak levels are superimposed in first-half and second-half portions of a blanking interval of each of the color signals R, G and B. The signals that result can be utilized in subsequent signal processing. Also, the input/output characteristics of a gamma correction circuit are represented by an exponential function, which is for a gamma correction, up to a fixed input range, and by a KNEE curve, whose slope is smaller than that of the exponential curve, in a range beyond the fixed input range. Variable-gain amplifier circuits are provided in the front and in the back of the gamma correction circuit, and the range of the input/output characteristic curve used in the gamma correction circuit is adjusted. As a result, video signals having a variety of tone characteristics may be processed and in addition, it is possible to realize a variable gamma for obtaining tone characteristics suited to personal preferences.

Claims10

Dependent claims

A variable-gamma correction circuit for use in an image processing apparatus comprising:

a gamma correction circuit having an input/output characteristic which, up to a fixed input range, is represented by an exponential curve for a gamma correction, and which, in a range beyond the fixed input range, is represented by a KNEE curve having a slope smaller than that of the exponential curve;
and
variable-gain amplifier circuits connected in front of and in back of said gamma correction circuit for adjusting the used range of the input/output characteristic curve in said gamma correction circuit.

An image signal processing apparatus comprising:

a peak detector circuit for detecting a maximum level and a minimum level of each of three types of color signals obtained by imaging a subject;
first variable-gain amplifier circuits for adjusting the magnitudes of at least two types of color signals of the three types of color signals in such a manner that differences between the detected maximum levels and minimum levels attain a predetermined ratio in the three types of color signals;
a gamma correction circuit, which is connected in back of said first variable-gain amplifier circuits and to which the three types of color signals are inputted, and which has an input/output characteristic which, up to a fixed input range, is represented by an exponential curve for a gamma correction, and which, in a range beyond the fixed input range, is represented by a KNEE curve having a slope smaller than that of the exponential curve;
and
second variable-gain amplifier circuits connected in back of said gamma correction circuit, and provided for at least two types of the three types of color signals, for adjusting, for every corresponding color signal, a used range of the input/output characteristic curve in said gamma correction circuit in relation to said ratio of the three types of color signals.

2 more elements

An image signal processing apparatus comprising:

first variable-gain amplifier circuits provided for at least two types of color signals for adjusting white balance of three types of color signals obtained by imaging a subject;
a gamma correction circuit, which is connected in back of said first variable-gain amplifier circuits and to which the three types of color signals are inputted, and which has an input/output characteristic which, up to a fixed input range, is represented by an exponential curve for a gamma correction, and which, in a range beyond the fixed input range, is represented by a KNEE curve having a slope smaller than that of the exponential curve;
and
second variable-gain amplifier circuits connected in back of said gamma correction circuit, and provided for at least two types of the three types of color signals, for adjusting, for every corresponding color signal, a used range of the input/output characteristic curve in said gamma correction circuit, and for finely adjusting white balance of the color signals.

1 more element

Dependencies are inferred from the claim text.

Negative-image signal processing apparatus

Life of this patent

Negative-image signal processing apparatus

Life of this patent

Abstract

Claims10