JPH03172081A - Camera - Google Patents

Abstract

PURPOSE:To obtain an optimum gradation characteristic corresponding to the distribution of objects by providing a photosensitive output characteristic varying means, which can select a first characteristic for photographing and a second characteristic different from the first characteristic, and selecting either the first or second characteristic based on a photographing condition. CONSTITUTION:An analog switch SW1 is turned ON/OFF by a system controller 4 and at first, when the switch is turned OFF, outputs are executed by characteristic lines O-Po. In such a case, this first characteristic is adopted for photographing not to use an illumination light source at 45 deg. inclination angle theta0 of the characteristic line. On the other hand, when the SW1 is set to an ON state based on the gradation compressing instruction of the system controller 4 and an output voltage exceeds Ea, a current flows through a voltage dividing resistor R2. The output characteristic becomes the characteristic of an inclination angle theta1 from a point Pa to a point P2 and a dynamic range to be detected is widened from an input voltage e1 to e2. This second characteristic is adopted for photographing to use the illumination light source.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a camera, and more particularly, to a camera that can improve the quality of photographed images when photographing using an illumination light source.

[Prior art] When photographing using an illumination light source such as a strobe in an electronic imaging system, it is necessary to determine the incident light intensity/photosensitivity level on the photosensitive recording system side, which is composed of an image sensor and a subsequent signal processing circuit, etc. If the ratio characteristics (gradation characteristics) are performed under the same conditions as when photographing using natural light, phenomena such as self-skipping are likely to occur. This phenomenon becomes particularly noticeable when photographing a subject with great depth. For example, FIG. 9 shows the relationship between the distance and the amount of reflected light during strobe light emission, and shows the relationship between A,
If the subjects at points B and C are photographed in one frame, even if you set the camera at point B in the center and give the proper exposure, it will be too bright for the subject at point A, resulting in ``overexposure''. It becomes a state. This is a particularly serious problem because the dynamic range of the photosensitive recording system is extremely narrow compared to conventional silver halide films. In order to solve this problem, a technique disclosed in Japanese Patent Application Laid-Open No. 196664/1983 is proposed. This technique is characterized by changing the γ characteristic, which is an important parameter representing gradation characteristics, in order to keep the output voltage within the above-mentioned narrow dynamic range, especially in strobe photography.

[Problems to be Solved by the Invention] However, since the method disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 196664/1989 provides γ correction to the entire range of imaging signals, the contrast of the main subject cannot be improved. This caused a problem in that it also lowered the amount of water.

A first object of the present invention is to provide a camera that can secure a dynamic range while maintaining contrast to the main subject when photographing using an illumination light source, in order to solve the above-mentioned problems. Similarly, it is an object of the present invention to provide a camera characterized in that optimum gradation characteristics can be obtained depending on the distribution of a subject when photographing using an illumination light source.

[Means and Effects for Solving the Problems] The camera of the present invention, when photographing using an illumination light source, compares the characteristics of the light-sensitive output level with respect to the incident light intensity on the light-sensitive recording system side to the first characteristic when no illumination light source is used. A camera having a photosensitive output characteristic variable means for setting a second characteristic different from the characteristic of the photosensitive output characteristic, wherein the second characteristic of the photosensitive output characteristic variable means substantially corresponds to the main subject. Regarding the part, see Part 1 above.
Another feature is that the characteristics of the image are substantially the same as the characteristics of the object, and the characteristics are different only in other parts. The photosensitive output characteristic variable means has a detection means, and the photosensitive output characteristic variable means has a plurality of the second characteristics, and changes one of the plurality of second characteristics according to the output of the detection means. It is characterized in that the characteristics can be selectively applied.

[Example of length] The invention will now be explained with reference to the illustrated embodiments.

FIG. 1 is a block configuration diagram of a camera showing one embodiment of the present invention, but only those related to the gist of the present invention are shown. A photographing light flux taken in through a photographing lens 1 is converted into an image signal by an image sensor 3 having an element shutter function via an aperture device 2. Then, it is processed by the imaging signal processing circuits below the S/H circuit 5 which are controlled by the system controller means 4. That is, S/
The signal is sampled and held by the H circuit 5 and separated into a luminance signal Y and color signals R, G, and B. Thereafter, after being limited to the northern region by the LPF circuit 6, a partial gradation compression circuit 7 and a gamma processing circuit 8, which are photoresponsive characteristic variable means to be described later, perform gradation compression processing according to each specified condition, which will be described later. and γ correction is performed. Note that this processing is performed on the luminance signal. This is done individually for each color signal. Then, the matrix circuit 9 generates color difference signals R-Y, B-Y.
This signal is output together with the luminance signal Y to the next-stage imaging circuit and recorded or reproduced as a video signal. The image sensor 3 and the image signal processing circuits below the S/H circuit 5 constitute a photosensitive recording system.

On the other hand, the aperture operation of the aperture device 2 is performed via the exposure control driver 10 controlled by the system controller 4, and the charge accumulation time of the image sensor 3 is further controlled. Further, the strobe light emitting means 11 serving as an illumination light source is controlled to emit light by the controller 4. Furthermore, the distance measurement signal from the distance measurement sensor 12, which is a detection means for detecting the positional distribution of the subject, is taken into the controller 4, and the gradation compression circuit 7 is controlled based on the distance measurement data. Ru. Further, the operation switch means 13 is used to select or designate a gradation compression compatible mode, a strobe photography mode, a multi distance measurement compatible mode, or the like.

The range sensor 12 is an active multi-beam sensor, and its details will be explained with reference to FIG. 2. ill
The g-giant sensor 12 is composed of a light projecting section and a light receiving section. The stage light section is an AI output from the system controller 4.
Driver circuit 2 controlled by distance control signal
3 causes the three light emitting elements LEDs 22a, 22b, and 22c to emit light at a predetermined timing. Then, the light is projected onto the subject 20 side through the projection lens 21 as a distance measuring beam.

The IfP+ distance beam is composed of three beams: a C beam in the center direction, an R beam in the right direction, and an L beam in the left direction. On the other hand, the light receiving section captures three reflected beams from the subject through the light receiving lens 24, and measures the distance D in the three directions above the PSD 25 of the optical position detector. , jibR. N
, and measure the respective subject distances. Note that the above aP1 distance sensor is a passive type l! using a one-dimensional linear sensor. −
It is also possible to use a one-range sensor.

Regarding the configuration and operation of the partial gradation compression circuit 7,
This will be explained using the circuit diagram shown in FIG. 3 and the characteristic diagram shown in FIG.

As shown in FIG. 3, the compression circuit 7 includes a resistor R1 having a resistance value r1 and a diode D connected in series.
A voltage dividing resistor R2 having a resistance value ``2'', an analog switch SWl, and a voltage Ea
It is composed of a DC power source Ba.

Further, e is an input voltage, and E is an output voltage. FIG. 5 is an output characteristic diagram of the compression circuit 7, in which the horizontal and vertical axes represent the input voltage e and the output voltage E, respectively. Note that since this input voltage e corresponds to the output signal of the image sensor 3, it has a value proportional to the brightness of the subject.

The analog switch SW1 is controlled ON and OFF by the system controller 4, and is first turned OFF.
In the case of F, the output voltage is always the same, and the output is according to the characteristic line 0-Po in FIG. In this case, the slope angle θ of the characteristic line. is 45@. Note that this characteristic is
This characteristic is applied when shooting without using an illumination light source.

On the other hand, based on the gradation compression instruction from the system controller 4, the control signal controls the analog switch SW.
1 is set to the ON state, the output characteristic line remains at the slope angle θ until the output voltage or input voltage reaches Ea or e. However, when the output voltage exceeds Ea, the partial voltage resistance R2
Current will flow through.

Then, the output characteristic will be the characteristic of the inclination angle θ1 between points Pa and P2, and the human power voltage ea and e2 will be 7 and the pressure E
It will be compressed into a-Ed and output. In other words, the detectable dynamic range has been expanded from the human power voltage e2 to e2.

l Note that this inclination angle θ1 is as follows. Therefore, when the switch SWl is ON, the characteristic exhibits a knee characteristic with a corner point Pa. Note that this characteristic is defined as a second characteristic and is applied when photographing using an illumination light source. Further, in the second characteristic, the inclination angle θ is common to the first characteristic. The input voltage range indicated by range M within the range approximately corresponds to the brightness from the area where the main subject exists.

A modification of the partial gradation compression circuit 7 will be explained with reference to FIGS. 4 and 6. In this modification, the characteristic line has one break point Pa in the case of the above embodiment, but there are two break points Pb and Pc.
It has the following.

In the circuit diagram of FIG. 4, only the parts that are different from the circuit diagram of FIG. 3 will be explained. When the analog switch SW2 is in the OFF state, A diode D1 is connected to the side. In the ON state, the diode DI is connected to the series circuit side of the DC power supply Be of the voltage Ec and the voltage dividing resistor R4 having the resistance value "4".

Its characteristics are shown in Fig. 6. First, when the analog switch SW2 is in the OFF state, the characteristic line has an inclination angle of θ0 (assumed to be 45° as described above) up to the output voltage Eb (equal to the human power voltage eb). In the region where the output voltage exceeds Eb, the characteristic line has an inclination angle θ2, and the input voltage e
, to e3 is the area where gradation is compressed. In this modification, such a characteristic is set as the first characteristic. Note that the inclination angle θ2 is reduced by the following.

When the analog switch SW2 is turned on based on the partial gradation compression instruction, the output voltage Ec
Similarly, the characteristic line until reaching C (equal to the input voltage e) has an inclination angle θ. However, when the output voltage Ec is exceeded, the inclination angle becomes θ3. Note that the slope θ3
is expressed by the following equation.

Therefore, the range of maximum input voltage increases from e3 to e4, and the input voltage e. The range -e4 is a region where gradation is strongly compressed. Such a characteristic is defined as a second characteristic in the case of this modification. In this second characteristic, the range of the input voltage in the range UM corresponds to the brightness from the area where the main subject is present. It is something.

Next, the tone compression characteristic selection operation by the camera of the embodiment shown in FIG. 1 will be explained with reference to the flowchart of the tone compression selection processing routine in FIG.

First, prior to the compression selection process, flags for each processing mode shown in Table 1 are set by the operation switch means 13. Thereafter, a gradation compression characteristic selection processing routine is called. Regarding the flag FB, the flag FB may be set to 1 even when strobe photography is automatically selected without depending on the operation switch means 13.

Table 1 First, in step S11, the gradation compression flag FA is checked. If the flag FA is O and the mode is the conventional mode in which gradation compression processing is not performed, step 5
The weak compression characteristic, which is the normal processing of No. 17, is selected, and the first characteristic, that is, the characteristic in which the compression circuit 7 performs no compression or only weak compression is selected.

Further, if the flag FA is set to 1 in step Sll, it is the gradation compression processing mode, and the process advances to step S12. Then, flag FB is used to check whether or not flash photography is being used. If flag FB is O, strobe light is not used, and the process jumps to step S17.

On the other hand, if the flag FB is set to 1, it is the strobe photography mode, and the process advances to step 31B, where the multi-distance measurement sensor 12 performs distance measurement.

Note that this distance measurement may use data if distance measurement has been performed immediately before this processing routine.

Subsequently, in step S14, it is determined whether multi-i11 distance data is to be used, and if the flag FC is 0 and the distance measurement data is not used,
Jump to step 516.

Then, flag FC is set to 1 and A? If it is specified to use j distance data, step S
15, the M1 distance sensor 12 determines object distances aP1 in three directions. Based on the data, the distribution of the subject in the front and back direction is determined, and if the distribution falls within the distribution range as described later, the process jumps to step S17 as gradation compression processing is unnecessary. If it is outside the range, the process advances to step S16 and processing is performed to select the strong compression characteristic. That is,
Turn on the switch SWl of the circuit 7 shown in FIG.
As described above, the second characteristic is selected in which the input/output relationship of the compression circuit 7 strongly compresses the gradation in a region where the amount of light is greater than a predetermined amount.

The range of subject distribution determination in step S15 will be described in detail. In this example, if the brightness of peripheral objects is within +IEv relative to the brightness of the central object, overexposure due to dynamic range overflow can occur even without strong compression correction using the second characteristic described above. The criterion for determining that the above phenomenon will not occur is set. Therefore, since the amount of illumination L for a subject is generally inversely proportional to the square of the subject distance ρ, the above brightness ratio condition can be converted to a subject distance condition. That is, if the following formula is satisfied, strong compression sleeve correction is not necessary.

Here g. ．． As described above, NR and 11L are M distances in the center direction, right direction, and left direction from the subject to be photographed, respectively, determined by AI using the distance measuring sensor 12. Then, in step S15, if the distribution of the subject satisfies the above equation (4) and is classified by 211, the process jumps to step S17, and if it is not satisfied and is classified by tq, the process proceeds to step S16 and the strong compression characteristic is selected. will be done.

Regarding the above-mentioned second characteristic for the compression characteristic, in this embodiment, one characteristic line was applied as each second characteristic line, as shown in FIGS. 5 and 6, but multiple characteristic lines were applied to this characteristic line. It is also possible to set one and select it according to the conditions.

Next, a case will be described in which the present invention is applied to tone compression characteristic selection during macro photography as another embodiment of the camera.

Compared to macro photography that does not use a strobe, or normal strobe photography that is not macro, macro photography that uses a strobe is particularly prone to overexposure. In this embodiment, the electronic imaging system has a partial tone compression circuit, and since macro photography is performed using a strobe, the strong compression characteristic, which is the second characteristic described above, is selected in the compression process. FIG. 8 shows a flowchart of the gradation compression characteristic selection processing routine. First, in step S21, it is determined whether macro photography using a strobe is set. If not, the process jumps to step 323, and if it is, the process proceeds to step S22. In step 323, strong compression is not required, but weak compression, i.e.
Normal compression properties are left. In step S22, the aforementioned second characteristic of the strong compression process is selected, and this routine ends.

[Effects of the Invention] As described above, the camera of the present invention has a photosensitive recording system that is capable of selecting a first characteristic for photographing without using an illumination light source and a second characteristic having different characteristics. It has an output characteristic variable means, in which the second characteristic is such that a portion substantially corresponding to the main subject matches the first characteristic, and the first or second characteristic is selected based on the photographing conditions. It is something that

Therefore, according to the present invention, when used with a bright light source, it is possible to perform photography that maintains the contrast for the main subject, that is, the gradation characteristics, and secures a wider dynamic range than during normal photography. Furthermore, it is possible to provide a camera that has remarkable effects such as being able to achieve optimum gradation characteristics depending on the distribution of the subject when used together with an illumination light source.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a camera showing an embodiment of the present invention, FIG. 2 is a diagram of a distance measuring sensor of the camera shown in FIG. 1, and FIG. 3 is a block diagram of the camera shown in FIG. Partial gradation compression circuit diagram; FIG. 4 is a partial gradation compression circuit diagram showing a modification of the compression circuit shown in FIG. 3 above; FIG. 5 is a characteristic diagram based on the compression circuit shown in FIG. 3 above. , FIG. 6 is a characteristic diagram based on the compression circuit shown in FIG. 4 above, FIG. 7 is a flow chart of tone compression characteristic selection processing in the camera shown in FIG. Flowchart of the macro photography step compression characteristic selection process in the camera showing the embodiment. FIG. 9 is a curve diagram of changes in light amount with respect to subject distance. 12... Distance sensor (detection means for detecting the positional distribution of subject separation)

Claims (2)

[Claims] (1) When photographing using an illumination light source, the characteristics of the photosensitive output level relative to the incident light intensity on the photosensitive recording system side are set to a second characteristic different from the first characteristic when no illumination light source is used. A camera having a light-sensitive output characteristic variable means, wherein the light-sensitive output characteristic variable means has a second characteristic that substantially corresponds to the first characteristic in a portion that substantially corresponds to the main subject. A camera characterized in that the camera is configured to be different only in other parts. (2) When photographing using an illumination light source, the characteristics of the photosensitive output level with respect to the incident light intensity on the photosensitive recording system side are set to a second characteristic different from the first characteristic when no illumination light source is used. A camera having a photosensitive output characteristic variable means, the camera having a detection means for detecting the positional distribution of a subject,
Further, the photosensitive output characteristic variable means has a plurality of the second characteristics, and one of the plurality of second characteristics can be selectively applied according to the output of the detection means. A camera characterized in that it is made as follows.