Technique for backlight compensation by selecting most appropriate compensation area and controlling iris in accordance with luminance level thereof

A backlight compensation method for a camera, comprising the steps of:

• forming in an image input stage of a camera, a visual image of a scene comprised of a plurality of backlight compensation areas;
• reading from said image input stage, values indicative of luminance signal levels within each of said areas;
• determining whether a backlight compensation-area adjustment key has been operated;
• generating adjusted areas by adjusting the positions and sizes of said backlight compensation areas when said backlight compensation-area adjustment key has been operated;
• determining whether an automatic/manual backlight compensation mode keys been operated when said backlight compensation-area adjustment key has not been operated;
• detecting said luminance signal levels of said adjusted areas when an automatic backlight compensation mode key has been operated;
• calculating difference values between said detected luminance signal levels and reference luminance levels;
• selecting a backlight compensation area corresponding to the least of said calculated difference values;
• controlling an iris conveying said visual image to the camera in accordance with the luminance signal level of said backlight compensation area selected;
• automatically redesignating said adjusted in accordance with changes in illumination due to the passage of time and the movement of an object within said visual image by again detecting said luminance signal level of said adjusted areas after a predetermined period of time after performing said controlling of said iris;
• and
• alternatively manually selecting one of said adjusted backlight compensation areas when a manual backlight compensation mode key has been operated instead of said automatic backlight compensation mode key;
• and
• controlling said iris in accordance with the luminance signal level corresponding to said backlight compensation area selected.

A backlight compensation method in a camera for selecting the most appropriate backlight compensation area according to the movement of an object or changes in illumination, from among a plurality of backlight compensation areas and controlling the level of the luminance signal, which is read out from an image input means, of the selected backlight compensation area, the method comprising the steps of:

• (a") adjusting the positions and sizes of said backlight compensation areas by operating a backlight compensation-area adjustment key;
• (b") detecting the luminance signal levels of a plurality of predetermined backlight compensation areas when a mode for selecting a predetermined backlight compensation area in a backlight compensation automatic mode is designated by an operation of a key;
• (c") calculating the difference values between said luminance signal levels detected in step (b") and reference luminance signal levels;
• (d") selecting a backlight compensation area having the least of said difference values calculated in step (c");
• (e") controlling an iris according to the luminance signal level of said backlight compensation area selected in step (d");
• (f") automatically redesignating a backlight compensation area according to changes in illumination due to the passage of time and the movement of the object by returning to step (b") a predetermined period time after performing step (e");
• (g") detecting the luminance signal levels of said backlight compensation areas adjusted in step (a") when a mode for selecting an adjusted backlight compensation area in the backlight compensation automatic mode is designated by an operation of a key instead of said predetermined backlight compensation are;
• (h") calculating the difference values between said luminance signal levels detected in step (g") and reference luminance signal levels;
• (i") selecting a backlight compensation area having the least of said difference values calculated in step (h");
• (j") controlling said iris according to the luminance signal level of said backlight compensation area selected in step (I");
• (k") automatically redesignating a backlight compensation area according to changes in illumination due to the passage of time and the movement of the object by returning to step (g") a predetermined period of time after performing step (j");
• (l") alternatively manually selecting one of said predetermined backlight compensation areas when a mode for selecting a predetermined backlight compensation area in a backlight compensation manual mode is designated by an operation of a key instead of said backlight compensation automatic mode;
• (m") controlling said iris according to the luminance signal level of said backlight compensation area selected in step (l");
• (n") alternatively manually selecting one of said adjusted backlight compensation areas when a mode for selecting an adjusted backlight compensation area in the backlight compensation manual mode is designated by an operation of a key instead of said backlight compensation automatic mode;
• and
• (o") controlling said iris according to the luminance signal level of said backlight compensation area selected in step (n").

A backlight compensation apparatus, comprising:

• image input means having registers driven by driving pulses and corresponding to displays thereof, for converting optical information of an object into an electrical signal;
• detecting means for detecting a luminance signal from said electrical signal;
• a memory storing positional information of a plurality of predetermined backlight compensation areas and reference luminance signal level values of corresponding backlight compensation areas;
• a microcomputer for generating area control signals according to the positional information of the backlight compensation areas stored in said memory by recognizing an automatic backlight compensation mode designation key input, and selecting a backlight compensation area having the least of the difference values between the reference luminance signal levels stored in said memory and the luminance signal levels detected by said detecting means;
• area pulse generating means for generating backlight compensation-area pulses corresponding to said plurality of predetermined backlight compensation area according to said area control signals and outputting said backlight compensation-area pulses to said image input means;
• and
• level controlling means for controlling the luminance signal level of said selected backlight compensation area to be a predetermined level.

A backlight compensation apparatus, comprising:

• an image input means comprised of registers driven by a driving pulse and corresponding to displays thereof, for converting optical information of an object into an electrical signal;
• detecting means for detecting a luminance signal from said electrical signal;
• backlight compensation area adjusting means for adjusting the positions and sizes of backlight compensation areas;
• a memory storing positional information of a plurality of predetermined backlight compensation areas, reference luminance signal level values of corresponding backlight compensation areas, and the positional information and reference luminance signal level values of said backlight compensation areas adjusted by said backlight compensation-area adjusting means;
• key inputting means comprising a key for commanding storage of the positions and sizes of said backlight compensation areas adjusted by said backlight compensation area adjusting means, a key for designating one of an automatic mode and a manual mode, a menu key for controlling the reading-out of the positional information and reference luminance signal levels of one of said predetermined backlight compensation areas stored in said memory and said adjusted backlight compensation areas stored in said memory, and selecting keys for manually selecting said predetermined backlight compensation areas;
• a microcomputer generating area control signals corresponding to said positional information, calculating the difference values between the reference luminance signal levels of said predetermined backlight compensation areas and said detected luminance signal levels according to the input of said automatic backlight compensation mode designation key and said menu key and selecting a predetermined backlight compensation area having the least difference value, calculating the difference values between the reference luminance signal levels of said adjusted backlight compensation areas and said detected luminance signal levels, and selecting an adjusted backlight compensation area having the least difference value;
• area pulse generating means for generating backlight compensation-area pulses corresponding to said predetermined backlight compensation areas and said adjusted backlight compensation areas according to said area control signals and outputting said backlight compensation area pulses to said image input means;
• and
• level controlling means for controlling the luminance signal level of a backlight compensation area selected under the control of said microcomputer and a backlight compensation area selected by a manual mode key and a selecting key.