JP2660598B2 - Imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging apparatus having an inversion processing unit for imaging a color image and inverting a color to obtain a normal image.

[Conventional technology]

FIG. 5 is a diagram showing the relationship between the exposure amount and the density at the time of photographing of a color negative film, and FIG. 6 is a block diagram of a conventional imaging apparatus.

6, reference numeral 1 denotes an image sensor for converting an optical image of a subject or a negative film into an electric signal, 2 denotes a luminance signal processing circuit for processing an output signal from the image sensor to generate a luminance signal (Y _H ), Is a color signal processing circuit that produces R, G, B signals. Reference numerals 4 and 5 denote gain control circuits for controlling the white balance of the R and B signals, respectively. Reference numeral 6 denotes a white balance control volume, which is provided independently for R and B signals. Reference numeral 7 denotes a matrix circuit for generating R-Y _L and B-Y _L signals as color difference signals. Reference numeral 8 denotes a negative / positive inversion processing circuit for a luminance signal, which includes an inversion circuit and a blanking processing circuit for setting a pedestal level. Reference numeral 9 denotes a volume for setting the pedestal level. Reference numerals 10 and 11 denote screw-positive inversion processing circuits for color difference signals, which are constituted by inversion circuits and the like. Reference numeral 12 denotes a switch circuit, which is switched by a negative / positive switching control signal. Reference numeral 13 denotes an encoder circuit, which generates a composite video signal from a luminance signal and a color difference signal.

FIG. 5 shows the characteristic of the density (D) of each photosensitive layer with respect to a typical exposure amount (logH) when photographing a color negative film. Such a negative film is illuminated with an appropriate light source having good color rendering properties. When the transmitted light is imaged by the negative-positive reversal imaging device having the above-described configuration, for example, at a certain exposure amount (E _O ), the R, G, and B outputs of the color signal processing circuit 3 are added to FIG. Thus, signal levels corresponding to R _O , G _O , and B _O are obtained.

[Problems to be solved by the invention]

Thus, in the conventional example shown in FIG. 6, since a signal level proportional to the density of the negative film is obtained, the saturation exposure density level, that is, the R, G, B output signal from the black level of the image sensor output is obtained. The levels are not equal even if each photosensitive layer is exposed the same amount. Therefore, for example, the white balance control circuit is adjusted for a color signal obtained by imaging a film portion having an exposure amount of _EO at the time of shooting, and the gains of R and B are controlled so that the signal levels become equal. If this is attempted, there is a drawback that the white balance shift becomes extremely large in a portion where the density is low, that is, in a portion where the R, G and B signal levels are relatively large.

The present invention has been made in order to solve the above-described problems of the conventional example, and has as its object to provide an imaging apparatus having an inversion processing unit in which white balance can be accurately adjusted in any density region of a negative film. I have.

[Means for solving the problem]

Therefore, the imaging apparatus according to the present invention is a color imaging unit that converts an optical image into an electric signal and generates a plurality of color signals, an inversion processing unit that inverts the colors of the plurality of color signals, An image pickup apparatus comprising black level shift means for shifting the black levels of a plurality of color signals by a predetermined amount in accordance with the operation of the inversion processing means.

[Action]

With such a configuration, the black levels of the plurality of color signals are shifted by the black level shift means when the inversion processing means operates.

Therefore, the white balance can be accurately adjusted in any density region.

〔Example〕

(Embodiment 1) FIG. 1 is a block diagram of an image pickup apparatus according to a first embodiment of the present invention, and FIGS. 2 and 3 are a relationship between an exposure amount and an output signal level for explaining the present invention. FIG. Sixth
The same (corresponding) components as those in the conventional example shown in the figure are denoted by the same reference numerals, and redundant description will be omitted.

In the figure, reference numerals 14 to 16 denote clamp circuits,
Set the black level of each of the R, G, B signals. Reference numeral 17 denotes a switch for switching the clamp potential of the clamp circuits 14 to 16, which is a selection switch interlocked with the switch circuit 12, and which is switched by a negative / positive switching control signal. Reference numerals 18 to 20 denote clamp potentials serving as black level shift means. In the normal mode, that is, during normal photographing, the clamp potentials (V _ref ) are supplied to the clamp circuits 14 to 16 as well, and the luminance signal and the color signal are negative-positive inversion processing circuits. Encoder 1 without going through 8,11,12
Output to 3. Negamodo, or clamping potential to the clamp circuit 14 (V _R) is supplied at the time of negative film photographing,
A clamp potential (V _B ) is supplied to the clamp circuit 16.

 Next, the operation will be described.

2 and 3 show the relative values of the color R, G, and B signal outputs obtained from the outputs of the clamp circuits 14 to 16 (film) when a special negative film as shown in FIG. The signal level of G at the base portion is set to 100%) and the exposure amount (l
ogH). FIG. 2 shows the case of the normal mode, and FIG. 3 shows the case of the negative mode. Since the clamp potential in the normal mode is _Vref for R, G, and B,
When signal processing is performed on a negative film as a captured positive image in this mode, the R, G, and B output signal levels have a characteristic proportional to the film density as shown in FIG. The signal level at E _O ) is V _RO ,
It becomes V _GO and V _BO , and the white balance shift becomes extremely large.

However, the clamp potential of the R signal at the time of Negamodo in the embodiment of the present invention is V _R, the clamp potential of the B signal is supplied V _B, these _{example, V R = V ref + (} V GO -V RO), By setting V _B = V _ref + (v _GO −V _BO ), the black levels of the R signal and the B signal are shifted by (V _GO −V _RO ) and (V _GO −V _BO ), respectively.
Accordingly, as shown in FIG. 3, the output signal levels become equal in the exposure amount (E _O ), and the white balance shift does not occur.

In the gain control circuits 4 and 5, the gain is adjusted by the white balance control circuit 6 so as to reduce the white balance deviation in a portion where the exposure amount is low, that is, in a portion where the signal level is large. The deviation can be made very small.

(Embodiment 2) FIG. 4 is a block diagram of an imaging apparatus according to a second embodiment of the present invention, and shows a conventional example shown in FIG. 6 and a first embodiment shown in FIG.
The same (corresponding) components as those of the embodiment are represented by the same reference numerals,
Duplicate description is omitted.

In FIG. 4, reference numerals 21 to 23 denote low-peak level detection circuits as black level shift means for detecting the lowest levels of the R, G, and B signals obtained by imaging a negative film. 24 to 26 are peak hold circuits for holding the low peak levels obtained from the low peak level detection circuits 21 to 23. Reference numerals 27 and 28 are comparison circuits for comparing the outputs of the peak hold circuits 24 to 26.

For example, assuming that the exposure amount (E _O ) in FIG. 2 is the maximum exposure value of the negative film to be imaged, the lowest levels of the R, G, B signals obtained from the color signal processing circuit 3 are V _RO , V _GO and V _BO . Low peak level detection circuit 2
In levels 1 to 23, this level is detected and the peak hold circuit 24
Holds at ~ 26. These are compared in the comparison circuits 27 and 28, and the comparison circuits 27 and 28 respectively output V _GO −V _RO and V _GO −V
A level change corresponding to _BO occurs, lowering the clamp potential of the R signal and increasing the clamp potential of the B signal. Thus, the signal level at the maximum exposure (E _O ) is set to V _GO for all of R, G and B as shown in FIG.

As described above, in the present embodiment, the signal level of the maximum exposure amount (E _O ) is detected and adjusted so as to be equal.
The white balance shift is automatically minimized.

In the above, the white balance adjustment when inverting a general negative film to obtain a positive image has been described.However, it is also possible to obtain a negative image from a positive film using the negative mode of the selection switches 12 and 17. It is.

〔The invention's effect〕

As described above, when inverting a color signal obtained by imaging a negative film or the like, by shifting the black level of each color signal, the white balance of a plurality of color signals can be accurately adjusted in any density region of the negative film. It has the effect of being able to match well.

It should be noted that the apparatus can be simplified if the black level shift means is preset by setting a clamp potential and switched by a selection switch.

In addition, the black level shift means detects the lowest peak level of a plurality of color signals, particularly at the time of color inversion, and automatically adjusts the white balance with high accuracy by setting the amount of black level shift according to the output. it can.

[Brief description of the drawings]

FIG. 1 is a block diagram of an image pickup apparatus according to a first embodiment of the present invention. FIGS. 2 and 3 are views showing a relationship between an exposure amount and an output signal level for explaining the present invention. FIG. 5 is a block diagram of an image pickup apparatus according to a second embodiment of the present invention, FIG. 5 is a view showing the relationship between exposure amount and density of a color negative film, and FIG. 6 is a block diagram of a conventional image pickup apparatus. . In the drawings, the same reference numerals indicate the same (corresponding) components. DESCRIPTION OF SYMBOLS 1 ... Image sensor 3 ... Color signal processing circuit 4, 5 ... Row gain control circuit 6 ... White balance control circuit 8, 10, 11 ... Negative / positive inversion processing circuit 12, 17 ... Switch circuit 18, 19, 20 …… Clamp potential 21,22,23 …… Low peak level detection circuit

Claims (1)

(57) [Claims] 1. A color imaging means for converting an optical image into an electric signal to generate a plurality of color signals, an inversion processing means for inverting the colors of the plurality of color signals, respectively, An image pickup apparatus comprising: a black level shift unit that shifts a level by a predetermined amount according to an operation of the inversion processing unit.