Color image pickup apparatus

Abstract: A color image pickup apparatus for correcting the sharpness of the luminance signal in a color image pickup system for taking out as different color signals for each of the horizontal lines the color information from the objects to be photographed with the use of a color iamge sensor having a color filter arrangement, whereby it is capable of correcting it even when the signals are saturated in the image sensor and the signal level between the adjacent two horizontal lines has been different in spite of the photographing the object which is the same in the signal level between two adjacent horizontal lines.

Description: BACKGROUND OF THE INVENTION The present invention generally relates to a color image pickup apparatus for correcting the sharpness of the luminance signal in a color image pickup system for taking out as different color signals for each of the horizontal lines the color information from the objects to be photographed with the use of a color image sensor having a color filter arrangement face. In recent years, color image pickup apparatuses with the use of a color image sensor are being popularized quickly by the best use of the characteristics of the smaller size and the lighter weight, and by the advancement in the higher performance. Image pickup apparatuses which are capable of coping with any objects to be photographed are expected. By the proper adjustment of the sharpness thereof even in the image quality, the resolution feelings of the finishing screen are improved. Therefore, the automatic adjustment of the sharpness becomes important in the color image pickup apparatuses. An example of the color filters of a color image sensor for taking out the color information from the photographed objects as different color signals for each of the horizontal lines with the mosaic shaped color filters being arranged on the front face is shown in Fig. 3. The conventional construction example of the luminance signal processing portion of the color image pickup apparatus is shown in Fig. 1. In Fig. 1, the construction and operation thereof will be described. The signal obtained from the color image sensor 1 is guided into a luminance signal separating circuit 4 and a vertical sharpness correcting signal generating circuit 3. The outputs of both the circuits are added by an adding circuit 6 and the luminance signal with the sharpness of the vertical direction being emphasized therein is obtained. The vertical sharpness correcting signal generating circuit 3 is composed of, for example, one horizontal scanning period delaying circuit (hereinafter 1H delaying circuit) 81, a subtracter 82 for getting the difference signal between the 1H delaying circuit output and the signal not delayed by 1H, a low-pass filter (hereinafter referred to as LPF) 83 and an amplifier 84. A further conventional construction example of the picture signal processing portion of the color image pick up apparatus is shown in figure 2. In this construction, the output signal of the color image sensor 1 is guided into a vertical sharpness correcting signal generating circuit 3 and a luminance signal separating circuit 4 and is further guided into a signal level detecting circuit 2 so as to detect the signal level for each picture element. The output signal of the signal level detecting circuit 2 controls the signal from the vertical sharpness correcting signal generating circuit 3 by a control circuit 5, and the output signal of the control circuit 5 is added to the output signal of the luminance signal separating circuit 4 by an adding circuit 6. The details of the signal to be obtained from the color image sensor 1 and the processing of the luminance signal processing circuit will be described with the use of Fig. 4 and Fig. 7 with the color filters shown in Fig. 3 being arranged as in the color image sensor 1. When the nH line of an odd number field or the n'H line of an even number field is scanned in Fig. 3, the signal to be changed for each of such picture elements as shown in Fig. 4 (a), (c) is outputted from the color image sensor 1. Also, when the (n+1)H line of the even number field or the (n+1)'H of the odd number field is scanned, the signal to be changed for each of such picture elements as shown in Fig. 4 (b), (d) is outputted from the color image sensor 1. From the nH line or the n'H line, the luminance signal of 2R + 3G + 2B is obtained as the low-pass signal, the color difference signal of 2B-G is obtained as the high frequency modulating signal. From the (n+1)H line or the (n+1)'H line, the luminance signal of the 2R + 3G + 2B is obtained as the low-pass signal, the color difference signal of 2R - G is obtained as the high frequency modulating signal. The characteristic graph of Fig. 5 shows the relationship between the output level (signal level) of these signals and the size (input light level) of the input light of the color image sensor 1. The straight lines (a) and (b) of Fig. 5 respectively show the signals of the picture elements Ye and Mg of the (n + 1)H line or the (n + 1)'H line and the signals of the picture elements of Cy and G. One dot chain line (e) shows the average value of both the picture elements, namely, the low-pass signal (luminance signal). Also, the dot lines (c) and (d) of Fig. 5 respectively show the signals of the picture elements of the nH line or n'H line Cy and Mg and the signals of the picture elements of Ye and G. Also, one dot chain line (f) shows the average value of both the picture elements, namely, the low-pass signal (luminance signal). Therefore, the processing of the luminance signal separating circuit 4 basically becomes the processing for removing the high-pass modulating signal through the low-pass filter in the output signal of the color image sensor. As shown in the wave form chart in Fig. 7, the processing of the vertical sharpness correcting signal generating circuit 3 becomes the processing for removing the high frequency modulating signal so as to amplify the proper magnification through the LPF 83 in the difference signal (Fig. 7, the wave form (c)) between the output signal (Fig. 7, the wave form (a)) of the color image sensor 1 and the output signal (Fig. 7, the wave form (b)) of the color image sensor 1 delayed by one horizontal scanning period. Accordingly, the luminance signal with such vertical sharpness shown in Fig. 7, the wave form (d), being corrected therein is obtained into the output of the adding circuit 6. But the conventional color image pickup apparatus of such construction as described hereinabove has the following problem points. The luminance signal obtained from the color image sensor 1 is an average signal of two picture elements in adjacent horizontal lines, the value thereof becoming equal in each horizontal line in principle (unless the object to be photographed changes). For example, as the incident light quantity becomes large, the signal from the picture element for generating the large signal level out of the respective picture elements of the color image sensor begins its saturation, with a problem that the luminance signal level of the adjacent two horizontal lines does not conform to each other before all the signals of the other picture elements are saturated. This situation will be described in detail with the use of Fig. 5, Fig. 6, Fig. 8. In the characteristics graph of the above described Fig. 5, the luminance signal level (shown in one dot chain lines (e), (f) in Fig. 5) of the adjacent two horizontal lines agrees with each other from the saturation level S sat of the color image sensor 1 to the incident light quantity L1 where the signal level of each picture element is small. When the incident light quantity exceeds L1, the signals of the picture elements of the (n+1)H line or the (n+1)'H line Ye and Mg shown in the straight line (a) of Fig. 5 are saturated at S sat. On the other hand, the signals of the picture elements of the Cy and the G in the (n+1)H line or the (n+1)'H line of the straight line (b) of Fig. 5, and the signals of the picture elements of the Cy and the Mg of the nH line or n'H line shown in the dotted lines (c) and (d) of Fig. 5 and the signals of the picture elements of the Ye and the G are not saturated yet so as to increase the signal level as the light quantity is added. The nH line or n'H line luminance signal does not change in the addition of the signal level accompanied by the incident light quantity increase like a straight line (f) in Fig. 5, while the (n+1)H line or the (n+1)'H line luminance signal becomes smaller in the signal level increase accompanied by the incident light quantity increase like a straight line (e) in Fig. 5, thus causing the difference in the luminance signal level of two horizontal lines. Fig. 6 shows a signal wave form chart for each picture element of the respective horizontal lines. Fig. 6 (a) shows the signal level for each of the (n+1)H line or the (n+1)'H line picture elements, with the larger one showing the signal of the picture elements of the Ye and the Mg. Fig. 6 (b) shows the signal level of each picture element of the nH line or the n'H line. When the signals different at the average signal level in the adjacent two horizontal lines as described hereinabove are processed by the signal processing circuit of the conventional color image pickup apparatus, further the signal level difference of two lines is emphasized as shown in Fig. 8. The wave form (a) of Fig. 8 is the output signal from the color image sensor 1, which has the signal level difference of dS between the adjacent lines. The wave form (b) of Fig. 8 is a signal thereof delayed by 1H. The wave form (c) of Fig. 8 is a difference signal between the wave form (a) and the wave form (b), and becomes a vertical sharpness correcting signal. The signal level difference dS' between two lines of the output luminance signal corrected in the vertical sharpness shown in the wave form (d) of figure 8 becomes larger than the level difference dS in the input signal. From JP-A-63269873 defining the closest prior art from which the invention proceeds, a further circuit for processing solid-state image pickup element output is known. In this known circuit, the output of a CCD is subjected to sample-and-hold in two phase sampling timings of the alternation of a picture element in sample-and-hold circuits and added in an adder. The luminance signal of an addition output is added to the contour correction signal of a contour correcting circuit in an adder and guided out to an encoder as a luminance signal output. The luminance signal of the adder is supplied to a comparator and compared with a reference voltage. This reference voltage is set by considering the dynamic range of a processing circuit system. When it is detected that the output of the comparator goes to a high level and exceeds the dynamic range, the signal of the contour correcting circuit is set to 0 at a detecting output to substantially prohibit the contour correction. Therefore, the contour of the stripe pattern is not emphasized, but the deterioration in the picture is reduced. In a further known image pickup apparatus according to EP-A-0 291 354 having an image pickup device, an amplifier, a vertical contour compensation circuit, a gamma correction circuit, a horizontal contour compensation circuit, a color operation circuit and an encoder, pixel compensation circuits are provided for reducing modulation components caused by a color filter during saturation in an image pickup device. Horizontal low-pass circuits combined with clippers are provided in the vertical contour compensation circuit to reduce modulation components caused by such compensation in the pixel compensation circuits. Although it is explained that the signal is saturated by the color image sensor, these circuits may be saturated earlier than the color image sensor 1 in, for example, the construction where the amplification circuit and the A/D converting circuit have been arranged immediately after the color image sensor without restriction to this example. Even in these cases, the same problem as described hereinabove occurs. SUMMARY OF THE INVENTION Accordingly, the present invention has been developed with a view to substantially eliminating the above discussed drawbacks inherent in the prior art, and has for its essential object to provide an improved color image pickup apparatus. Another important object of the present invention is to provide an improved color image pickup apparatus, which does not emphasize the above drawbacks, and is capable of correcting the above drawbacks even when the signals are saturated in the image sensor and the signal level between the adjacent two horizontal lines has been different in spite of the photographing the object which is the same in the signal level between two adjacent horizontal lines. Still another important object of the present invention is to provide a color image pickup apparatus which has correction and vertical sharpness emphasis. In accomplishing these and other objects, according to the invention, there is provided a color image pick-up apparatus of a weighted average luminance signal type in which a luminance signal is obtained from a weighted average signal of signals from adjacent horizontal lines, comprising solid state color imaging sensor means comprised of a plurality of photoelectric elements arranged in a two-dimensional pattern having a plurality of horizontal lines for picking up color image data of an object to be photographed, signal level detecting means for detecting a signal level for each of the picture elements of said color imaging sensor means and generating a control signal for controlling a gain of a vertical edge correction signal for vertical sharpness correction when the detected signal level is larger than a specified reference level, luminance signal seperating means for separating a luminance signal thereby to generate a main luminance signal, and gain control means for controlling the gain of the vertical edge correction signal for vertikal sharpness correction in accordance with the control signal fed from said signal level detecting means, said color imaging sensor means having a color filter arrangement disposed substantially in front of said color imaging sensor means, characterized by first delay means for delaying an output signal of said color imaging sensor means by one horizontal scanning period, second delay means for delaying an output signal of said first delay means by one horizontal scanning period, averaging means for taking an average of the output signal of said color imaging sensor means and the output signal of said second delay means, first adding means for adding the output signal of said first delay means and an output signal of said averaging means to produce a combined signal of three adjacent horizontal lines, subtracting means for subtracting the output signal of said averaging means from the output signal of said first delay means to produce a difference signal which serves as a vertical edge correction signal for correcting sharpness in the vertical direction among the adjacent three horizontal lines, said luminance signal separating means separating the luminance signal from the output signal of said first adding means, and second adding means for adding the gain-controlled signal derived from said gain control means to the main luminance signal supplied from said luminance signal separating means, thereby producing a luminance signal corrected in vertical sharpness with respect to the three adjacent horizontal lines. Further advantageous embodiments are defined in the dependent claims. According to the invention, the luminance signal is obtained from the weighted average signal of three adjacent horizontal lines, the signal level for each of the picture elements of the color image sensor is detected by the signal level detecting circuit. When the signal level is larger than the reference level, the signal level of the vertical sharpness correcting signal is made smaller, so that it is corrected even when the signal from the image sensor is saturated and the signal levels in the two adjacent horizontal lines are different, and also, the vertical sharpness emphasis is normally effected. BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and features of the present invention will become apparent from the following description taken in conjunction with the preferred embodiment thereof with reference to the accompanying drawings, in which: Figures 1 and 2 are block diagrams showing the construction of conventional color image pickup apparatus; Fig. 3 is an example of a construction view of color filters arranged on the front face of the color image sensor to be used for the color image pickup apparatus of the present invention and the conventional embodiment; Fig. 4 and Fig. 6 are models of signals to be obtained from the color image sensor with the color filters of Fig. 3 being arranged on them; Fig. 5 is a characteristics chart showing the input, output characteristics of the signals to be obtained from the color image sensor with the color filters being arranged on them; Fig. 7 is a wave form chart for explaining the processing of obtaining the luminance signal emphasizing the vertical sharpness from the signal to be obtained from the color image sensor with the color filters of Fig. 3 being arranged on them; Fig. 8 is a wave form chart for explaining the characteristics of the conventional embodiment; Fig. 9 is a block diagram showing a preferred embodiment of a color image pick apparatus of the present invention; Figures 10, 12, 13, 15 and 16 are block diagrams showing detailed circuit embodiment of the signal level detecting circuit to be used in the present invention; Fig. 10 is a block diagram of a signal level detecting circuit for generating the control signal when the signal level of at least one picture element is larger than the reference level with the adjacent two pictures in the horizontal direction being provided as one unit; Fig. 11 is a wave form chart for explaining the operation of the signal level detecting circuit; Fig. 12 is a block diagram of a signal level detecting circuit for generating the control signals when the signal level of at least one picture element is larger than the reference level with four picture elements, two picture elements adjacent in the horizontal direction and two picture elements adjacent in the vertical direction, being provided as one unit; Fig. 13 is a block diagram of a signal level detecting circuit for generating a control signal corresponding to the signal level of the smaller picture element of the signal level from between two picture elements of the above described one unit when the signal level of at least one picture element is larger than the reference level with two picture elements adjacent in the horizontal direction being provided as one unit; Fig. 14 is a characteristics graph of the input, output characteristics of the color image pickup element showing the relationship between the input light level and the output signal level; Fig. 15 is a block diagram of a signal level detecting circuit for generating the control signal corresponding to the signal level of the smaller picture element of the signal level from between two picture elements of one unit of the horizontal line to which the picture element where the signal level is larger than the reference level belongs when the signal level of at least one picture element is larger than the reference level with four picture elements, two picture elements adjacent in the horizontal direction and two picture elements adjacent in the vertical direction, being provided as one unit; Fig. 16 is a block diagram of a signal level detecting circuit for generating the control signal corresponding to the signal level of the picture element smaller at the signal level from between two picture elements of one unit of the horizontal line to which the picture element where the signal level is larger than the reference level belongs when the signal level of at least one picture element is larger than the reference level with four picture elements, two picture elements adjacent in the horizontal direction and two picture elements adjacent in the vertical direction, being provided as one unit; Fig. 17 is a wave form chart for illustrating the operation of a preferred embodiment of the invention, in an example where the vertical sharpness correcting signal is adapted to be controlled to stop the vertical sharpness correcting signal when the signal of each of the picture elements of the color image sensor detected by the signal level detecting circuit is larger than the reference level; and Fig. 18 is a wave form chart for explaining the operation of a preferred embodiment of the invention, in an example where the polarity and the gain of the vertical sharpness correcting signal are controlled when the signal level for each of the picture elements of the color image sensor detected by the signal level detecting circuit is larger than the reference level. DETAILED DESCRIPTION OF THE INVENTION Before the description of the present invention proceeds, it is to be noted that like parts are designated by like reference numerals throughout the accompanying drawings. A color image pickup apparatus in the embodiment of the present invention will be described hereinafter with reference to the drawings. Fig. 9 is a block diagram showing an embodiment of the present invention. In Fig. 9, reference numeral 1 is a color image sensor with color filters shown in Fig. 3 being arranged on them. The signals to be obtained from the color image sensor 1 and the processing of obtaining the luminance signals from the signals will be described in detail hereinafter. When the odd number field of nH line or the even number field of n'H line is scanned in Fig. 3, the signals to be changed for each of the picture elements as shown in Fig. 4 (a), (c) are outputted from the color image sensor 1. Also, when the odd number field of (n+1)H line or the even number field of (n+1)'H is scanned, the signals to be changed for each of the picture elements as shown in Fig. 4 (b), (d) are outputted from the color image sensor 1. The luminance signals of 2R + 3G + 2B are obtained as low-pass signals, the color difference signals of 2B - G are obtained as the high frequency modulating signals from the nH line or the n'H line. The luminance signals of 2R + 3G + 2B are obtained as the low-pass signals, the color difference signal of 2R - G are obtained as the high frequency modulating signals from the (n+1)H line or the (n+1)'H line. The characteristics chart of Fig. 5 shows the relationship between the output level (signal level) of these signals and the size (input light level) of the input light of the color image sensor 1. Namely, the straight lines (a) and (b) of Fig. 5 respectively show the signals of the picture elements of the (n+1)H line or the (n +1)'H line of Ye and Mg and the signals of the picture elements of the Cy and G, the one dot chain line (e) thereof shows the average value of both the picture elements, namely, the low-pass signal (luminance signal), also, the dot lines (c) and (d) of Fig. 5 show respectively the signals of the picture elements of the nH line or n'H line of Cy and Mg, and the signals of the picture elements of the Ye and the G, also one dot chain line (f) shows the average value of both the picture elements, namely, the low-pass signal (luminance signal). Therefore, the luminance signal separation processing basically removes the high-pass modulating signal through the low-pass filter in the output signal of the color image sensor. The vertical sharpness correcting signal generating processing removes the high frequency modulating signal through the low-pass filter (LPF) in the difference signal (Fig. 7, the wave form (c)) between the output signal (Fig. 7, the wave form (a) of the color image sensor 1 and the output signal (Fig. 7, the wave form (b)) of the color image sensor 1 delayed by one horizontal scanning period so as to effect the amplification of the proper multiplying factor. By the addition of the above described luminance signal and the vertical sharpness correcting signal, the brilliance signal whose vertical sharpness is corrected as shown in Fig. 7, the wave form (d) is obtained. In the embodiment shown in Fig. 9, the output signal of the color image sensor 1 is guided into a signal level detecting circuit 2 so as to detect the signal level for each picture element. The construction and the function of the different embodiments of the signal level detecting circuit 2 are described below in detail. Furthermore, a first signal is generated by delaying the output signal of the color image sensor 1 by 1H by a first 1H delaying circuit 71, and a second signal is generated by averaging the output signal of the color image sensor 1 and the output signal of a second 1H delaying circuit 72 by an adding circuit 73 and an x 1/2 circuit 74. The output signal of the second 1H delaying circuit 20 is generated by delaying the output signal of the 1H delaying circuit 71. Both the first and second signals each are guided to an adding circuit 76 and a substracting circuit 75. The output signal of the adding circuit 76 is guided into a luminance signal separating circuit 4, so that the main luminance signal is obtained. The signal is not caused in the signal level difference between the lines even when the signal has been saturated, but is not normally good in the vertical sharpness. The output signal of the subtracting circuit 75 is the difference signal, namely, the vertical edge signal of adjacent two lines, and therefore, becomes the signal for vertical sharpness correcting use. The output signal of the subtracting circuit 75 is gain controlled with the control signal from the signal level detecting circuit 2 by a gain control circuit 77. The output of the gain control circuit 77 is added, to the main luminance signal from the luminance signal separating circuit 4 by an adding circuit 6. The gain control circuit 77 controls the gain of the vertical sharpness correcting signal so that the vertical sharpness may be established into the desired value when the signal has not been saturated, and so that the gain of the vertical sharpness correcting signal may be controlled in accordance with the saturation level when the saturation of the signal is caused. Therefore, in the output of the adding circuit 6, the luminance signal good in the vertical resolution for each of the respective horizontal lines when the saturation of the signal has not been caused is obtained. The signal corrected in the signal level difference between the lines is obtained when the saturation of the signal has been caused. By such construction, the luminance signal and the vertical sharpness correcting signal may be fundamentally obtained from the adjacent three lines, further the vertical sharpness correcting signal may be controlled by all the three line signal condition, and the continuous control may be effected more correctly for each of the lines, so that the luminance signal which is gentle, smaller in the deterioration of the vertical sharpness, and smaller in the signal level difference caused among the lines. When the signal of the two adjacent horizontal lines from the color image sensor 1 is saturated in the signal of the picture element on one side of the one horizontal line as shown in the wave forms (a) and (b) of Fig. 4 or the wave forms (a) and (b) of Fig. 11, the wave form expressing for each horizontal period (hereinafter referred to as 1H period) the output signal of the color image sensor becomes a signal having the level difference for each 1H in the wave form (a) of Fig. 17. Accordingly, the difference signal between the signal and the signal delayed by 1H (Fig. 17, the wave form (b)) becomes the wave form (c) of Fig. 17. The construction shown in, for example, Fig. 10 (a) is considered as the first example of the signal level detecting circuit 2. The signal of the color image sensor 1 is guided into the input terminal 7 so as to be compared for each picture element with the reference level from the reference level generator 9 by the comparator 8. The output of the comparator 8 is guided into the 1 picture element delaying circuit 11, and also, the "or" with respect to the output of the 1 picture element delaying circuit 11 is provided by the "or" circuit 12. Assume that the signal inputted into the input terminal 7 is such a wave form signal as shown in Fig. 11 (a), and the reference level is a value a little smaller than the saturation level of Fig. 17, and the output of the comparator 8 becomes a signal high at level at the timing of the picture element saturated at the signal level as shown in Fig. 11 (c), and becomes a signal low at level at the timing of the picture element not saturated at the signal level. Therefore, the output of the 1 picture element delaying circuit 11 becomes the wave form (d) of Fig. 11, the output of the "or" circuit 12, namely, the output of the signal level detecting circuit 2 becomes a signal shown in the wave form (e) in Fig. 11. The clock which is in conformity with the picture element period is guided into the comparator 8 and 1 picture element delaying circuit 11 and is capable of comparison and 1 clock of delaying for each picture element. In Fig. 11, the wave form (e) is provided as the wave form (d) of Fig. 17 when it is expressed for each 1H period. This shows that the signal level detecting circuit 2 outputs the high level signal only for the horizontal line period during which the saturation is being caused. During the period, the control circuit 77 controls the stopping of the input signal. Therefore, the controlled vertical sharpness correcting signal becomes a signal having the wave form (e) of Fig. 17. The output signal to be obtained from the adding circuit 6 has the wave form (f) of Fig. 17. The signal level difference for each 1H period becomes dS'' and becomes larger than the level difference dS of the original signal, but becomes smaller than the level difference dS' in the conventional example of Fig. 8 (d), thus resulting in effects in the present embodiment. Fig. 10 (b) is a second example of a signal level detecting circuit 2). In this example, the "or" circuit 12 in a first example shown in Fig. 10 (a) is provided as an exclusive or circuit 14, and the saturation detecting signal is adapted not to be outputted when both the two picture elements adjacent in the horizontal direction have been saturated. In such a case, the deterioration of the vertical sharpness of the vertical edge portion is effected no more. This is because the saturation may be detected from the line with at least one picture element of the line on the single side of the two horizontal lines adjacent in the vertical direction being saturated when both the two picture elements adjacent in the horizontal direction as clear from Fig. 5 are saturated. Fig. 12 (a) is a third example of the signal level detecting circuit 2. As the like parts are designated by like reference numerals throughout the same portions as the first example of Fig. 10 (a) in the example, the 1H delaying circuit 20, the second comparator 21, the second 1 picture element delaying circuit 23, the second "or" circuit 25 are added to the first example. The input signal 1H delayed at the signal level is also detected and the "or" with respect to the signal for detecting the level of the signal not delayed by the third "or"- circuit 27 is provided, so that the signal level detecting circuit is adapted to generate the control signal when the saturation of the signal has been caused even in the either single line of the two adjacent horizontal lines. A signal having the wave form (a) of Fig. 17 is outputted from the color image sensor 1, the signal to be outputted from the level detecting circuit 2 becomes a signal having the wave form (d)' of Fig. 17, the signal to be outputted from the control circuit 77 is provided as a signal having the wave form (e)' of Fig. 17, and the output signal to be obtained from the adding circuit 6 is a signal having the wave form (f)' of Fig. 17. The signal level difference for each of 1H periods becomes dS, and becomes the same as the level difference dS of the original signal, so that the level difference increase by passing through the vertical sharpness correcting signal generating circuit is removed, thus resulting in large effect in the present embodiment. Fig. 12 (b) is a fourth example of the signal level detecting circuit 2. In the example, the "or" circuit 12 in the third example of Fig. 12 (a) and the second "or" circuit 25 are the exclusive or circuits 14, 28. In a third example as shown in the second example of the above described signal level detecting circuit 2, the deterioration of the vertical sharpness of the vertical edge portion in such a case is effected no more in such construction where the saturation detecting signal is adapted not to be outputted when both the adjacent two picture elements in the horizontal direction have been saturated. The description is omitted, because the operation of the circuit and the effect are apparent from the example from Fig. 10 (b) and the Fig. 12 (a). When the level detecting circuit 2 is in a first or a second example of the above described Fig. 10 (a) or (b), the signal from the level detecting circuit 2 becomes a signal having the wave form (e) of Fig. 18. As the control circuit 77 is adapted to amplify the input signal with a proper scale factor and the signal is adapted to effect the reversing control operation of the polarity of the input signal when the signal is high at level, the output signal of the control circuit 77 becomes a signal having the wave form (d) of Fig. 18. Therefore, the output signal to be obtained from the adding circuit 6 is provided as a signal having the wave form (f) of Fig.18. The signal level difference for each of 1H periods becomes dS, and becomes the same as the level difference dS of the original signal, the level difference increase is provided no more by passing through the vertical sharpness correcting signal generating circuit, thus resulting in effects even in the present embodiment. When the level detecting circuit 2 in the present embodiment is in the third, fourth examples of the above described Fig. 12 (a) or (b), the signal from the level detecting circuit 2 becomes a signal having the wave form (e)' of Fig.18. As described hereinabove, the control circuit 77 amplifies the input signal with a proper scale factor and also, the signal effects the reversing control of the polarity of the input signal when the signal is high at a level, so that the output signal of the control circuit 77 becomes a signal having the wave form (d)' of Fig. 18, and therefore, the output signal to be obtained form the adding circuit 6 is a signal having the wave form (f)' of Fig. 18. The signal level difference for each of 1H periods is provided no more, the vertical sharpness emphasis and the correction of the signal level difference between the lines are effected, thus resulting the effects in the present embodiment. Fig. 13 is a fifth example of the signal level detecting circuit 2, the difference with respect to the example up to the above description is that in the above described example, the output signal of the color image sensor 1 is saturated, and all the uniform control signals are adapted to be generated, while in the present embodiment, the control signal corresponding to the condition of the saturation signal is adapted to be generated. The signal from the color image sensor 1 is inputted to an input terminal 7 as shown in Fig. 13, and the signal is detected as to whether or not the saturation of the signal from the color image sensor 1 exists by the saturation detecting circuit 36 using the construction the same as the circuit shown in Fig. 10 (a). The signal to be inputted to the input terminal 7 is guided even into a third 1 picture element delaying circuit 31 and is delayed by one picture element, and the smaller signal of the signal not delayed or the signal delayed by one picture lement is selected by a selecting circuit 32. The output signal of the selecting circuit 32 is guided into a switching circuit 33. The vertical sharpness setting control signal for setting the vertical sharpness emphasis when the signal of the color image sensor 1 is not saturated is inputted into another input terminal 34 of the switching circuit 33. The two input signals are switched with the control signal from a saturation detecting circuit 36 and are outputted into an output terminal 35. When the saturation detecting circuit 36 does not detect the saturation of the signal, the vertical sharpness setting control signal is outputted into the output terminal 35. When the saturation detecting circuit 36 detects the saturation of the signal, the output signal of the selecting circuit 32 is outputted to the output terminal 35. The output signal of the output terminal 35 will be described further with the use of Fig. 14. The solid straight lines (a) and (b) of Fig. 14 show the straight lines (a) and (b) of Fig. 7 and show the output signal level with respect to the incident light amount of two picture elements of one horizontal line of the color image sensor 1. The curve line (c) of Fig. 14 shows the output signal of the output terminal 35, namely, the vertical sharpness controlling signal. It is the value of the vertical sharpness setting control signal level while the incident light quantity where signal of the color image sensor 1 is not saturated is smaller than L1, the level becomes the signal level corresponding to the signal (Fig. 14, the curve line (b)) of the picture element not saturated when the signal of the color image sensor 1 starts its saturation. Namely, when the signal has been saturated, the value of the vertical sharpness control signal is made smaller when the signal level of the picture element not saturated is smaller, and the value of the vertical sharpness control signal is made larger when the signal level of the picture element not saturated is larger so as to effect the controlling operation of respectively decreasing or increasing the emphasis of the vertical sharpness. By such controlling operation, the signal level difference between the horizontal lines when the signal has been saturated is also large when the signal level difference between the picture elements are generally large. On the other hand, when the signal level difference between the picture elements is small, the signal level difference between the horizontal lines when the signal has been saturated is also small, with an advantage that the conventional problem points may be reduced without making the signal level difference between the horizontal lines conspicuous or without the unnecessary deterioration of the vertical sharpness. The saturation detecting circuit 36 to be used in the above described example is not necessary to be restricted to the above described circuit example. It is clear that the circuit construction of the Fig. 10 (b), Fig. 12 (a), (b) which are in the above described second, third, fourth examples of the above described signal level detecting circuit 2 may be used. The signal of the line to be saturated is required to be guided into the selecting circuit 32 when the example where the saturation detecting signal is adapted to be caused when the signal is saturated even in either line of adjacent two lines with the use of the 1H delaying circuit as in the example of Fig. 12 (a), (b). Such example is shown in Fig. 15 and Fig. 16. Fig. 15 is a first detailed construction example of the fifth signal level detecting circuit, where the circuit of Fig. 12 (a) is used in the signal level detecting circuit 2 of the example of Fig. 13 so as to effect small modifications. In Fig. 15, the saturation detecting signal of two signals, the signal through the 1H delaying circuit and the signal not delayed by the 1H delaying circuit are fed into control terminals a, b independently as the control signal into a selecting circuit 51 from the saturation detecting circuit 36. The signal passing through the 1H delaying circuit, the signal not passing through the 1H delaying circuit, the vertical sharpness setting control signal are respectively guided into three input terminals c, d, e of the selecting circuit 51. The selecting circuit 51 selects the signal of the input terminal d when the control input of the control terminal b is high at level, the signal of the input terminal c when the control input of the control terminal a is high at level, the signal of the input terminal e when the control input of the control terminals a and b are both low at level, the input terminal c or d (although the smaller signal of the input terminals c, d may be ideally selected, either of two signals may be selected) when the control inputs of the control terminals a and b are both high at level. The output signal of the selecting circuit 51 is guided into a 1 picture element delaying circuit 53 and a small signal selecting circuit 54. The signal corresponding to the signal level of the picture element not saturated of the saturated horizontal line or (when the signal is not saturated) the vertical sharpness setting control signal is outputted into an output terminal 55, with effects the same as in the example of Fig. 7 being obtained. By the above described construction, the 1 picture element delaying circuit and the small signal selecting circuit may be omitted by one respectively by the application of the circuit of Fig. 12 (a) as it is into Fig. 13. Fig. 16 is a second detailed construction example of the fifth signal level detecting circuit, where the circuit of Fig. 12 (b) is used in the signal level detecting circuit 2 of Fig. 13, further the output signal of the 1H delaying circuit 20, and the signal, where the signal delayed further by a second 1H delaying circuit 42, and the original input signal (signal not delayed) are averaged by an adding circuit 43 and an X 1/2 circuit 44, are used as input signals. As the example is used, and further the output signal of the 1H delaying circuit 20 is used for the luminance signal separating circuit 4, the vertical sharpness correcting signal may be controlled by the signal condition of all the adjacent three lines including the line of the horizontal lines for obtaining the luminance signal, so that the control operation may be effected more correctly and the signal level difference caused between the lines may be controlled to minimum. Although the analog processing digital processing has not been referred to as the signal processing system in the description of the embodiment of the above described present invention, it is clear that the present invention may be achieved even in any processing system. As the signal level detection circuit in the above described embodiment is proper to detect the signal level for each of the picture elements, the digital processing is easier to realize. In the case of the digital processing, the processing for converting the output signal of the color image sensor 1 into the digital signal by the A/D converting circuit becomes necessary in all the above described embodiments. The present invention is not restricted to the color image sensor 1 with the color filters shown in Fig. 17 being arranged. It is clear that the present invention may be applied to the general color image sensor on which the color filters are arranged, which are adapted to output the information from the object to be photographed as the different color signals for each of the horizontal lines.

Claims: A color image pick-up apparatus of a weighted average luminance signal type in which a luminance signal is obtained from a weighted average signal of signals from adjacent horizontal lines, comprising: solid state color imaging sensor means (1) comprised of a plurality of photoelectric elements arranged in a two-dimensional pattern having a plurality of horizontal lines for picking up color image data of an object to be photographed; signal level detecting means (2) for detecting a signal level for each of the picture elements of said color imaging sensor means (1) and generating a control signal for controlling a gain of a vertical edge correction signal for vertical sharpness correction when the detected signal level is larger than a specified reference level; luminance signal seperating means (4) for separating a luminance signal thereby to generate a main luminance signal; and gain control means (77) for controlling the gain of the vertical edge correction signal for vertical sharpness correction in accordance with the control signal fed from said signal level detecting means (2); said color imaging sensor means (1) having a color filter arrangement disposed substantially in front of said color imaging sensor means (1); characterized by first delay means (71) for delaying an output signal of said color imaging sensor means (1) by one horizontal scanning period (1H); second delay means (72) for delaying an output signal of said first delay means (71) by one horizontal scanning period; averaging means (73, 74) for taking an average of the output signal of said color imaging sensor means (1) and the output signal of said second delay means (72); first adding means (76) for adding the output signal of said first delay means (71) and an output signal of said averaging means (73, 74) to produce a combined signal of three adjacent horizontal lines; subtracting means (75) for subtracting the output signal of said averaging means (73, 74) from the output signal of said first delay means (71) to produce a difference signal which serves as a vertical edge correction signal for correcting sharpness in the vertical direction among the adjacent three horizontal lines; said luminance signal separating means (4) separating the luminance signal from the output signal of said first adding means (76); and second adding means (6) for adding the gain-controlled signal derived from said gain control means (77) to the main luminance signal supplied from said luminance signal separating means (4), thereby producing a luminance signal corrected in vertical sharpness with respect to the three adjacent horizontal lines. The color image pick-up apparatus as claimed in claim 1, wherein the signals of corresponding picture elements in adjacent horizontal lines of an odd or an even field are different from one another. The color image pickup apparatus as claimed in claim 1, wherein said gain control means (77) controls the gain applied to the vertical sharpness correction signal in such a manner that the vertical sharpness is established at a desired value when the picture element signal of said color imaging sensor means (1) is in a non-saturated state, while the gain applied to the vertical sharpness correcting signal is controlled in accordance with a saturation level of the signal when said picture element signal is in a saturated state. The color image pick-up apparatus as claimed in claim 1, wherein said averaging means comprises: third adding means (73) for adding the output signal of said color imaging sensor means (1) and the output signal of said second delay means (72); and multiplying means (74) for multiplying an output signal of said third adding means (73) by 0.5. The color image pickup apparatus according to claim 1, wherein the signal level detecting means (2) generates the control signal when the signal level of at least one of two horizontally adjacent picture elements of said color imaging sensor means (1) is larger than the reference level. The color image pickup apparatus according to claim 1, wherein the signal level detecting means (2) generates the control signal when the signal level of at least one picture element of a group of four picture elements is larger than the reference level, two of said group of four picture elements being adjacent in a first horizontal line, and the other two being horizontally adjacent in a second line and also being vertically adjacent to the two picture elements in the first line. The color image pickup apparatus according to claim 1, wherein the signal level detecting means (2) generates the control signal corresponding to the signal level of the picture element of said color imaging sensor means (1) whose signal level is smaller of two horizontally adjacent picture elements when the signal level of at least one of said two horizontally adjacent picture elements is larger than the reference level. The color image pickup apparatus according to claim 1, wherein the signal level detecting means (2) generates the control signals corresponding to the signal level of the picture elements of said color imaging sensor means (1) whose signal level is smaller of the two horizontally adjacent picture elements, when the signal level of at least one picture element of a group of four picture elements is larger than the reference level, said group of four picture elements comprising said two horizontally adjacent picture elements in a first line and another two pixels which are horizontally adjacent in a second line and are also vertically adjacent to the two picture elements in the first line.

Inventors: KITAMURA YOSHINORI, NAKAYAMA MASAAKI, KITAMURA, YOSHINORI, NAKAYAMA, MASAAKI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1991
Main classification: H04N5
IPC codes: H04N9, H04N5