KR100338439B1 - Method and apparatus for automatic compensation for camera backlight - Google Patents

Abstract

The automatic backlight compensation apparatus of a camera according to the present invention is characterized in that the light luminance of the entire photographing screen is determined by the photometric unit, the luminance of the central portion of the photographing screen is determined by side rejection, the two luminance differences are obtained by comparing the two luminance, It is determined whether the difference is within the set range and whether or not the automatic backlight compensation is performed is determined. At this time, the passive AF module is used as the side rejection of the automatic backlight correction device of the camera according to the present invention, and the response time of the passive AF module is used to detect the brightness of the center of the photographing screen with the output of the passive AF module. That is, since the passive AF module has a characteristic that the response time varies depending on the brightness level of light, the present invention uses this.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an automatic backlight compensation apparatus,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure control apparatus and an exposure control method for a camera, and more particularly, to an automatic exposure control method and an exposure control method for a camera that achieve an automatic backlight correction using a cds (cadmium sulfide) element and a passive AF A correction device and a method thereof.

In general, the exposure meter of the camera system is composed of a reflective light meter and an incident light meter, and the incident light meter is a method of measuring light illuminating the subject. The reflected light meter is reflected on the subject at the actual photographing position, It is a method of measuring one light.

In the case of a reflective exposure meter, a photometry element for measuring the brightness of the subject is provided in the camera system in order to appropriately expose the subject in accordance with the brightness of the subject, and the output current The appropriate exposure amount is set according to the amount of the water.

In addition, in the light metering mode for proper exposure control, the center weighted average light metering for measuring the brightness around the center of the screen, the spot metering for only the minute portion of the screen, And a multi-divisional photometry method in which appropriate exposure is determined by analyzing each photometry data in the region where the photometry is performed.

The metering method using multi-segmented sensor, which is mainly used in high-end cameras, allows several divided and independent metering sensors to measure the brightness of the subject and its surroundings, thus making the exposure proper. The center-weighted average light-measuring method used mainly by an automatic camera is a light-measuring method using a cds element formed of a single light-measuring element. In this case, the cds element is a photoconductive element which is mainly composed of emulsified cadmium and applied to the flasher of the streetlight or the exposure system of the camera system. Since the internal resistance value is lowered when the incident light is incident, the cds element can be used as a function like a resistor in a circuit.

As described above, the cds element measures the average brightness of the entire screen determined by the lens and exposes the subject. Therefore, when the subject to be photographed is dark and the surrounding background is bright (backlight condition), the phenomenon of darkening have. In order to compensate for this, a separate function called a backlight compensation mode is added in most automatic cameras. This is because it is inconvenient for the consumer to operate according to the situation of the subject, and when the consumer does not use the backlight compensation function in the backlight condition The exposure of the photograph may not be appropriate.

The present invention provides an apparatus for automatically correcting backlight using a passive AF system and a cds photometry element, even if the user does not perform any other operation.

In addition, the present invention provides a method for allowing a backlight correction function to be performed automatically in response to a subject situation.

1 is a block diagram of an automatic backlight compensation apparatus for a camera according to an embodiment of the present invention.

FIG. 2 is a diagram showing a luminance detection area in an imaging screen according to an embodiment of the present invention. FIG.

FIG. 3 is a diagram illustrating conversion of the response time of the passive AF module of FIG. 1 into a linear function.

4 is a flowchart illustrating an operation of an automatic backlight compensation apparatus for a camera according to an embodiment of the present invention.

According to an aspect of the present invention, there is provided an apparatus for correcting a backlight of a camera, the apparatus comprising: a photometry unit for determining light luminance of the entire photographing screen; determining a luminance of the center of the photographing screen by side rejection; Determines whether or not the obtained difference in brightness is within the setting range, and determines whether to perform the automatic backlight compensation. At this time, the passive AF module is used as the side rejection of the automatic backlight correction device of the camera according to the present invention, and the response time of the passive AF module is used to detect the brightness of the center of the photographing screen with the output of the passive AF module. That is, since the passive AF module has a characteristic that the response time varies depending on the brightness level of light, the present invention uses this.

Accordingly, an automatic backlight compensation apparatus of a camera according to an embodiment of the present invention includes a release first stage and a release second stage switch, a photometric unit, a passive AF module, a control unit, a shutter driving unit, and a focus adjustment unit.

Here, the first-stage release and second-stage release switches generate a signal indicating the start of the shooting operation and the shooting operation.

The photometry part detects the brightness of light incident on the camera and outputs it as an electrical signal. At this time, it is preferable that the photometry unit detects the luminance of light using a cds element.

The passive AF module measures light intensity from the subject and outputs it as an electrical signal. The signal output from the passive AF module is a signal for the luminance phase of the subject light and shade.

The control unit judges the first brightness level at the central portion of the photographing screen with the output of the passive AF module, determines the second brightness level of the entire photographing screen with the output of the photometry unit, compares the first and second brightness levels, It is determined whether the difference in luminance level is within the setting range. If the difference between the two luminance levels is within the setting range, it is determined that the subject is in the forward lighting condition. If the difference between the first and second luminance levels is not within the setting range, the subject is determined to be the backlighting condition. The control unit controls photography in the initial setting mode when the subject state is a pure light condition, and switches backlight mode to perform backlight correction operation when the backlight condition is satisfied.

Here, the control unit stores a program for calculating the first brightness as the response time of the passive AF module, and the program is related to the following equations (1) and (2).

Here, the response time is the response time of the passive AF module, and Y is the conversion value of the response time.

Here, X1 and X2 are design values of the set brightness level as a reference, and Y1 and Y2 are converted values of the set brightness level based on the reference.

The shutter driving unit drives the shutter according to the control signal of the control unit to adjust the amount of light incident on the camera, and the focus adjusting unit performs the auto focus adjustment according to the control signal of the control unit.

According to another aspect of the present invention, there is provided a method of automatic backlight compensation of a camera,

A method of controlling a camera including a passive AF module for detecting a distance between a camera and a subject and a photometry part using a cds element,

A first step of driving the passive AF module and the photometry part in accordance with a release first signal; A second step of measuring a response time of the passive AF module and calculating the response time; A third step of comparing a first brightness calculated by the passive AF module with a second brightness calculated by the photometry part; A fourth step of determining whether a difference between the first and second brightness is within a set range; And a fifth step of performing automatic backlight correction when the difference between the first and second brightness is not within a set range and performing shooting in a first setting mode when the difference between the first and second brightness is within a set range do.

The second step may include the steps of obtaining a response time of the passive AF module by measuring the time from when the driving start time of the passive AF module starts to when the output occurs, Determining a subject luminance value corresponding to the first conversion value, determining an exposure amount, and determining a distance between the subject and the camera using output data of the passive AF module.

Hereinafter, an automatic backlight compensation apparatus for a camera according to an embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a block diagram of an automatic backlight compensation apparatus for a camera according to an embodiment of the present invention. The photographing apparatus of the camera shown in Fig. 1 includes a release first stage and release second stage switches S1 and S2, a photometric unit 10, a passive AF module 20, a control unit 30, a shutter driving unit 40, (50).

Here, the first and second stage switches S1 and S2 are operated by the photographer to output a signal to the control unit 30 notifying the start of the photographing operation and the photographing.

The light measuring unit 10 measures the luminance level of light incident on the camera using the cds element, and outputs the measured luminance level to the controller 30. At this time, the luminance area measured by the photometric unit 10 is the area A1 shown in Fig. 2, and is an area for detecting the luminance for the first half of the photographing screen (A). Those skilled in the art can easily make the area for measuring the brightness of the entire photographing screen in an area wider or narrower than the area A1.

The passive AF module 20 is composed of one AF device for automatic focus control of a passive type. The passive AF device is composed of two photometric sensors not shown internally, Detects a contrast phase difference, converts the phase difference into an electrical signal, and outputs the electrical signal to the controller 30. At this time, the luminance area measured by the passive AF module 20 is the area A2 in FIG. 2 and is an area for detecting the luminance with respect to the center of the photographing screen A.

Here, the passive AF module 20 varies its response time according to the brightness level of the light. That is, the response time of the passive AF module 20 becomes shorter as the brightness level of incident light becomes higher.

The control unit 30 drives the photometry unit 10 and the passive AF module 20 in accordance with the release 1 stage ON signal and judges the subject brightness with a signal output from the photometry unit 10 and the passive AF module 20 , Determines the brightness level of the entire image sensing screen with the output signal of the photometric unit 10, and determines the brightness level of the center of the sensing screen with the output signal of the passive AF module 20.

The control unit 30 drives the passive AF module 20 to determine the subject brightness level using the output signal of the passive AF module 20 and simultaneously drives a timer (not shown) to count the time ) Stops driving the timer when an output signal is input from the passive AF module 20, and measures the time at which the timer counts, that is, the response time of the passive AF module 20.

At this time, the response time of the passive AF module 20 is shown as a curve decreasing in log form according to the set brightness level as shown in FIG. 3A.

Fig. 3 is a diagram showing the conversion of the response time of the passive AF module of Fig. 1 into a linear function, which is obtained in the passive AF module test. 3, a represents the response time of the passive AF module 20 for each optical brightness level. The horizontal axis represents the brightness level set in the passive AF module test, and the vertical axis represents the response time. The horizontal axis represents the brightness level set at the time of passive AF module testing, and the vertical axis represents the conversion value corresponding to the response time. In the figure, b represents the response time of the passive AF module 20 converted to a linear function.

Referring to FIG. 3A, the passive AF module 20 has a non-linear response in which the response time becomes longer as the optical brightness level becomes lower, and the response time becomes shorter as the optical brightness level becomes higher. This nonlinearly changing response time makes it difficult to determine the brightness level, so that the nonlinear curve of FIG. 3 a is converted into a linear curve through Equation (1).

In Equation (1), Y is the conversion value of the response time of the passive AF module 20, and corresponds to the vertical axis in Fig. 3B. Therefore, the response time of the passive AF module 20 is converted into the conversion value Y linearly corresponding to the set brightness level.

Here, since the response time of the passive AF module 20 of the camera may be slightly different for each set, as shown in the following Table 1, the design value at one or more set brightness levels (arbitrarily settable) (X1, X2) and converted values (Y1, Y2) are measured.

Setup Luminance (LV) Measured value LV Designed (LV-5) × 8 Response Time The conversion value (Y) 7.0 X1 = 16 2.840 Y1 = 85 15.0 X2 = 80 0.013 Y2 = 15

The set values X1 and X2 and the converted values Y1 and Y2 are stored in a storage device of a camera not shown and the designed values X1 and X2 and the converted values Y1 and Y2 are calculated at the time of luminance calculation. And a conversion value (Y) corresponding to a variable input response time are used to obtain a luminance value as Equation (2).

The control unit 30 compares the luminance level of the passive AF module 20 and the luminance level obtained through the metering unit 10 and determines whether the difference between the two luminance values is greater than 0.5. If the difference between the two luminances is greater than 0.5, the subject is in the backlight condition, and if it is less than or equal to 0.5, Here, a person skilled in the art can arbitrarily change the subject backlight reference value.

In this case, the control unit 30 performs photography in a state in which the photographing mode originally set is maintained as it is when the subject is in a pure light condition, and in a backlight condition, the backlight correction operation is performed by switching the setting mode to the backlight mode.

On the other hand, the control unit 30 determines the contrast phase difference of the light incident on the camera from the signal output from the passive AF module 20, and determines the distance between the camera and the subject based on the contrast phase difference.

The shutter driving unit 40 and the focus adjusting unit 50 perform a shutter operation and an auto focus control corresponding to the control signals of the control unit 30. [

Hereinafter, a method capable of performing automatic backlight correction of a camera according to an embodiment of the present invention will be described with reference to FIG.

4 is a flowchart illustrating an operation of an automatic backlight compensation apparatus for a camera according to an embodiment of the present invention.

4, when the photographer turns on the first stage release switch S1 (S100), the control section 30 drives the photometry section 10 and the passive AF module 20 in accordance with the release first stage on signal , The output signals of the photometric unit 10 and the passive AF module 20 are received (S200).

At this time, the control unit 30 checks the response time of the passive AF module 20 (S310), and substitutes the response time as a variable value into the program for Equation 1 to calculate a first conversion value (S320) .

Subsequently, the control unit 30 substitutes the first conversion value into the program for Equation (2) to calculate the first luminance level of the central portion A2 of the photographing screen A (S330) The first brightness level is calculated as the response time of the passive AF module 20 and the second brightness level of the first half A1 of the photographing screen A is calculated by the output of the photometry section 10 at step S340.

The controller 30 compares the calculated two luminance levels as shown in Table 2. If the difference between the two luminance levels is greater than the set value 0.5, which is arbitrarily set, as shown in Table 2, Mode, and if it is less than or equal to 0.5, the current mode is maintained (S400, S410, S420).

Subject Measurement data (LV) Passive AF module data Comparison value Lightning / Backlighting Light source Street Response time Conversion value Luminance value Pure light 2M 13.875 0.302 -1.727 13.520 0.355 Sunlight 3M 14,000 0.250 -2,000 13.795 0.205 Sunlight 4M 14,000 0.148 -2.756 14.556 -0.556 Sunlight 5M 14,000 0.164 -2.608 14.407 -0.407 Sunlight 7M 14.125 0.160 -2.644 14.443 -0.318 Sunlight 10M 14.125 0.170 -2.556 14.355 -0.230 Sunlight Backlight 2M 14.125 0.600 -0.737 12.524 1.601 Backlight 3M 14,000 0.320 -1.644 13.436 0.564 Backlight 4M 14,000 0.310 -1.690 13.483 0.517 Backlight 5M 14,000 0.390 -1.358 13.149 0.851 Backlight 7M 14.125 0.450 -1.152 12.941 1.184 Backlight 10M 14.125 0.530 -0.916 12.704 1.421 Backlight

When the backlight mode is set, the control unit 30 calculates the exposure amount for backlight correction, and when the ON signal of the release second-stage switch S2 is input (S500), the control unit 30 outputs a control signal To the shutter driving unit (40). If the backlight mode is not set, the on-signal of the second-stage release switch S2 is input (S500) to the shutter drive section 40 with the exposure amount calculated from the first brightness level or the exposure level calculated from the second brightness level, And controls so that a shutter operation corresponding to the calculated exposure amount is performed (S600).

The control unit 30 calculates the distance between the camera and the subject as the phase difference of the subject lightness and darkness obtained from the output of the passive AF module 20 at the same time as driving the shutter driving unit 40 (S350) And controls the focus adjusting unit 50 to perform an auto focus adjustment corresponding to the determined focus adjustment amount.

Accordingly, if the difference between the first luminance at the center of the photographing screen and the second luminance at the front of the photographing screen is greater than 0.5, the camera determines that the subject is in the backlighting condition and performs photography in accordance with the automatic backlight correction, Is less than or equal to 0.5, it is judged that the light is in the condition of light forward, and the photographing is performed according to the set mode.

The above-described embodiments are only one of the most preferred embodiments for attaining the objects of the present invention, and the present invention is not limited to the above embodiments.

The present invention automatically performs backlight compensation operation without artificially setting the backlight correction mode, so that it is not necessary to install the backlight correction mode setting device, thereby reducing the cost.

In addition, it has the same effect as the multi-divisional light metering method applied to an advanced model of a camera, thereby enhancing the quality of the camera and improving the reliability of the camera.

Claims (8)

A passive AF module for detecting a distance of a subject, a photometry part, and a controller for controlling the passive AF module and the photometry part according to the operation of the switch, , A first step of driving the passive AF module and the photometry part according to the operation of the first-stage release switch; A second step of measuring a response time of the passive AF module, calculating a first converted value by the response time, and calculating a first luminance based on the first converted value; A third step of comparing a first brightness calculated by the passive AF module with a second brightness calculated by the photometry part; A fourth step of determining whether a difference between the first and second brightness is within a set range; And If the difference between the first brightness and the second brightness is not within the setting range, the photographing mode of the camera is set to the automatic backlight correction mode so that the backlight correction photographing is performed, And a fifth step of maintaining the photographing mode of the camera in a preset mode so as to perform photographing. (Correction) The method according to claim 1, The second step comprises: Measuring a response time of the passive AF module; converting a response time of the passive AF module, which varies nonlinearly according to a brightness level, into a first converted value linearly variable according to a brightness level; 1 conversion value to obtain a first luminance value. (Correction) The second step comprises: Wherein the response time of the corresponding passive AF module is nonlinearly determined according to a luminance level of incident light, and the first conversion value is obtained through the following equation. Y (first conversion value) = log (response time x 256) x 30. (Correction) The second step comprises: Wherein the brightness value is calculated by substituting the first conversion value into the following equation. Here, X1 and X2: the design value of the set brightness level based on the reference, Y1, Y2: conversion value of the set brightness level as a reference, Y is the first conversion value. A release first stage and a release second stage switch operated by a photographer to generate a signal indicating the start of the photographing operation and the photographing performance; A photometric unit for detecting a luminance of light incident on the camera and outputting the detected luminance as an electrical signal; A passive AF module for measuring lightness and darkness of light emitted from a subject and outputting the result as an electrical signal; And The first brightness of the center portion of the photographing screen judged from the response time of the passive AF module and the first conversion value calculated from the response time and the second brightness of the entire photographing screen judged by the output of the photometry portion, And determines that the subject is in the backlight condition, and switches the mode to the backlight mode so that the backlight correction operation is performed. If the difference between the levels of the two lights is within the setting range, And a controller for measuring the distance to the subject from the output of the AF module. 6. The method of claim 5, The light- wherein the brightness of the subject is measured using a cds element. 6. The method of claim 5, The control unit Wherein the first conversion value is calculated using the following equation. Y (first conversion value) = log (response time x 256) x 30. 6. The method of claim 5, Wherein, And calculates the first luminance from the first conversion value using the following equation: < EMI ID = Here, X1 and X2: the design value of the set brightness level based on the reference, Y1, Y2: Conversion value of the set brightness level as the reference.