JPH07123293B2 - Imaging device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image pickup apparatus capable of appropriately detecting a high-intensity part or the like on a subject.

[Prior art]

Conventionally, the following methods have been considered as methods for controlling the amount of light to the solid-state image sensor. That is, it is a method of obtaining an appropriate aperture value using an electric signal output from the image sensor, or a method of providing an element for photometry (for example, SPC) separately from the image sensor and controlling the aperture by this SPC output. .

Among them, the former method is not suitable for a system that emphasizes the rising characteristics after release, such as a still video camera.

That is, since the dynamic range of the image sensor itself is generally extremely narrow, it takes a very long time to control the diaphragm so that the amount of incident light falls within this range.

On the other hand, in the latter method, the image sensor and the SPC do not always capture the same subject, so that the amount of incident light is difficult to enter the dynamic range of the image sensor.

The following method can be considered in order to eliminate such drawbacks of the conventional technique. That is, before recording the image signal from the solid-state image sensor, first, with a photometric element such as SPC, calculate the aperture value based on, for example, the average amount of light from the subject and open the aperture, and then perform the recording operation. Along with the start, the aperture mechanism is stopped according to the aperture value, and the amount of light applied to the solid-state image sensor via the aperture mechanism is measured by the solid-state image sensor. Then, the aperture value is recalculated based on this measured value, and the aperture mechanism is re-apertured to control the amount of light with which the solid-state image sensor is irradiated with high accuracy.

However, when there is a high-intensity part such as a light source or a regular reflection part of the light source on the subject, the information signal output from the solid-state image sensor shows an abnormally high value, and the exposure of other parts is also appropriate. Nevertheless, the exposure may be judged to be incorrect. Further, it has been impossible to determine the presence or absence of blooming due to the high-intensity part of the subject from the information signal from the solid-state image sensor.

〔Purpose〕

The present invention has been made in view of such conventional problems, and an object thereof is to provide an imaging device capable of appropriately detecting a high-luminance portion or the like on a subject.

〔Example〕

An embodiment of the present invention will be described with reference to FIG. In the figure, reference numeral 1 denotes an optical system including an imaging lens 1a, an aperture mechanism 1b, a half mirror unit 1c, and a CCD (charge-coupled device).
And a solid-state image pickup device 1d as an image pickup means and a measuring device 1e for measuring the brightness of a subject. The light from the subject incident on the half mirror unit 1c through the taking lens 1a and the aperture unit 1b is divided into two parts, one is guided to the solid-state image sensor 1d, and the other is guided to the photometric device 1e. There is. The solid-state image pickup device 1d converts incident light into signal charges, and controls an accumulation time of the signal charges by an accumulation time control circuit 2 as image forming condition control means to obtain an information signal and an amplifier 3 and a process circuit. It is input to a known recording circuit 5 via 4. Reference numerals 6 and 7 are storage time setting circuits for setting the first and second storage times respectively for the storage time control circuit 2, so that the second set time is, for example, 1/2 of the first set time. It is set. 8
Is an average value calculation circuit for calculating the average luminance according to the information signal from the solid-state image pickup device 1d input through the amplifier 3 and the process circuit 4, and 9 and 10 are signals from the average value calculation circuit 8, respectively. Sample-hold circuit (S / H) that performs sample-hold, where S / H9 is mono multivibrator (MM ₁ ) 11 and sample pulse generator circuit (SP ₁ ) 12
Also, the S / H10 is a mono multivibrator (MM ₂ )
It operates with the pulse formed by 13 and the sample pulse generation circuit (SP ₂ ) 14. 15 is a doubling circuit for doubling the signal level from S / H10, 18 is a signal level from S / H9 and doubling circuit 15 is compared and discriminated, and image characteristics such as presence or absence of a high-luminance portion in the subject are displayed. A high-level signal (H) and a low-level signal (L) are input to the storage time setting circuit 6 and the inverter 19, respectively, by a window comparator as a determining means for determining. Reference numeral 20 denotes an aperture value calculation circuit that calculates the aperture value based on the information signals from the photometric element 1e and the storage time control circuit 6, and 21 drives the aperture mechanism 1b according to the aperture value calculated by the aperture value calculation circuit 19. A diaphragm control circuit, 22 is a drive circuit for driving the solid-state imaging device 1d, 23 is a clock generator for outputting the CP ₇ signal and signals such as CP ₁ to CP ₆ having the timing shown in FIG.
The CP ₁ signal is to the photometric element 1e and the aperture value calculation circuit 20, the CP ₂ signal is to the aperture control circuit 21, the CP ₃ and CP ₄ signals are to the storage time setting circuits 7 and 6, respectively, and the CP ₅ signal is the storage time control circuit. 2, CP ₆ signal to mono multivibrator 11,13, CP ₇
The signals are respectively input to the drive circuit 22.

The accumulation time setting circuits 6 and 7 constitute exposure control means for variably controlling the combination of the incident light amount (aperture value) and the imaging time (accumulation time) in the solid-state imaging device 1d which is the imaging means, and the window comparator 18 is A first signal output from the solid-state imaging device 1d as a first exposure state by setting the incident light amount and the imaging time as a first combination;
The input light amount and the image pickup time are set to a second combination different from the above, thereby forming a comparison unit for comparing the second signal output from the solid-state image pickup device 1d as the second exposure state. In addition, when the first signal and the second signal are not in a predetermined relationship based on the output of the comparison result,
A window comparator 18 constitutes a signal forming means for forming a signal indicating this.

Next, the operation will be described with reference to FIG.

(1) Section T ₁ (Here, one section indicates one field.) Now, when the start switch (not shown) is operated, the light from the subject is taken by the photographing lens 1a and the aperture mechanism in the open state.
The light is guided to the half mirror unit 1c via 1b, and a part of the incident light is reflected by the half mirror unit 1e, and the photometric element 1e
Is incident on. On the other hand, the photometric element 1e and the aperture calculation circuit 20
Is synchronized with the vertical sync signal (V _D )
It operates by the clock pulse CP ₁ output from 23.

By the photometric element 1e operated by the clock pulse CP ₁ ,
The brightness of the subject is measured, and in the aperture value calculation circuit 20,
The first accumulation time (T _V ′) output from the accumulation time setting circuit 6 is calculated from the measured brightness and CP ₄ to obtain the aperture value. Then, the diaphragm mechanism 1b is narrowed down in the section T ₁ by the diaphragm control circuit 21 according to the calculated diaphragm value.

(2) Light from the subject is irradiated onto the section T ₂ solid-state image sensor 1d through the taking lens 1a, the diaphragm mechanism 1b narrowed down in the section T ₁ and the half mirror unit 1e, and the solid-state image sensor 1d receives a signal. Generate an electric charge.

On the other hand, a storage time setting signal is input from the storage time setting circuit 6 to the storage time control circuit 2. Therefore, the signal charge is substantially accumulated for the time T _V ′.

Incidentally, various methods have been conventionally known as a method for controlling the accumulation time, and therefore will not be described in detail here.

(3) Section T ₃ Similar to the section T ₂ , the light from the subject is irradiated and the signal charge is generated in the solid-state image sensor 1d.

On the other hand, the clock pulse CP ₃ from the clock generator 23
Is input to the accumulation time setting circuit 7, and the accumulation time setting circuit 7
The storage time control signal is input to the storage time control circuit 2. Then, the signal charge is accumulated for the time T _V ″.
On the other hand, the image information accumulated in the T ₂ section is transferred by the drive circuit 22 in this T ₃ section by a known method and output as an image information signal by the amplifier 3 and the process circuit 4.
Is input to the average value calculation circuit 8 via.

The average value calculation circuit 8 calculates the average luminance from this image information signal and outputs the average luminance information signal (signal level: V _L ′) to S / H.
Enter in 9. On the other hand, CP ₆ is output at the beginning of the T ₃ section and MM ₁ 1
A pulse is output from SP ₁ 12 at a timing delayed by time t ₁ from clock pulse CP ₆ by ₁ . S / H9 performs sampling in synchronization with this pulse, and the average value of the image in section T ₂ is bolded and the window comparator 18
Entered in.

The image signal accumulated in the section T ₃ is transferred to T ₄ by the drive circuit 22.
The solid-state image sensor 1d is transferred to the section and used as an image information signal.
Is output from the output terminal and is input to the average value calculation circuit 8 via the amplifier 3 and the process circuit 4.

The average value calculation circuit 8 calculates the average luminance from this image information signal and outputs the average luminance information signal (signal level: V _L ″) to the S / H.
Enter in 10. The S / H 10 delays the clock pulse CP ₆ at MM ₂ 13 by the time t ₂ and performs sampling by the pulse output from SP ₂ 14. The signal obtained by this sampling has its signal level doubled by the doubling circuit 15 and then input to the window comparator 18.

This window comparator 18 has an S / H9 and a doubling circuit.
From 15, the signals with the levels V _a and V _b are simultaneously input, and when | V _a −V _b | ≦ S (S: predetermined value), the H signal is output, and the H signal is output. Storage time setting circuit 6
To enter. Then, the T _V ′ signal is input from the accumulation time setting circuit 6 to the accumulation time control circuit 2, and imaging and recording are possible under the condition of T _V ′.

On the other hand, when | V _a −V _b |> S, the L signal is inverted by the inverter 19 and then input to the warning display device 17 to issue a warning.

As described above, in the embodiment of the present invention, image pickup is performed under the image forming condition having a predetermined relationship of T _V ′ and T _V ″ (T _V ′ = 2T _V ″), and the image signal formed by this image pickup is obtained. By comparing, the characteristics of the image such as whether or not the image is smeared are determined. This is because when T _V ′ and T _V ″ have a predetermined relationship and the output of the image sensor complies with this relationship, the image formed on the image sensor is in accordance with the image forming conditions. This means that the change has been made properly, that is, the change range of the image forming conditions is
It is within the dynamic range of the image sensor.

On the other hand, if the output of the image pickup device does not change or the change does not occur according to a predetermined rule despite the change in the image forming condition, it means that the change range is outside the dynamic range.

According to the present invention, it is possible to determine what kind of image characteristics the image pickup means has in this way by changing the image forming condition. In the embodiment, the example of the accumulation time control is shown as the image forming condition. However, the exposure time may be changed by the shutter or the aperture may be changed. Alternatively, it may be a change in sensitivity.

Further, the comparison method is not limited to the discrimination by the window comparator, and any discrimination may be performed by various calculations.

[Effect]

As described above, the present invention has an effect that the characteristics such as the presence or absence of the high-luminance portion in the subject can be easily discriminated.

[Brief description of drawings]

FIG. 1 is a view showing an embodiment of the present invention, and FIG. 2 CP _{1 to} C
P ₆ and (a) to (d) are diagrams showing the waveforms of the respective parts in FIG. 1. 1d: solid-state image sensor (imaging means) 2 ... storage time control circuit (image forming condition control means) 18: window comparator (discrimination means)

Claims (1)

[Claims] 1. An image pickup unit, an exposure control unit for variably controlling a combination of an incident light amount and an image pickup time in the image pickup unit, and a first combination of the incident light amount and the image pickup time set by the exposure control unit. The second signal output from the image pickup means as the second exposure state by setting the first signal output from the image pickup means as the second exposure state and the second combination of the incident light amount and the image pickup time by the exposure control means. Comparing means for comparing the signal and a first exposure state based on an output of the comparing means.
Signal forming means for forming a signal indicating this when the first signal and the second signal are not in a proportional relationship with the ratio of the exposure amount of the second exposure amount to the second exposure amount according to the second exposure state, An imaging device having a.