JP2002077720A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire fixed iris variation regardless of an iris opening and closing direction. SOLUTION: This image pickup device is provided with an image pickup element 16 for image picking up an object 12, an optical lens system 14 having an auto-iris mechanism arranged in the front stage, a main signal processing part 20 for generating a video signal from an image pickup signal obtained from the image pickup element, and a control means 24 for detecting the level of the luminance signal of a video signal outputted from the main signal processing part. The control means is provided with a means for setting control characteristics for the auto-iris mechanism. The auto-iris mechanism is controlled based on the iris drive signal set by the setting means. The iris drive signal is generated by the setting means so that light quantity variation against a unit control time can be made equal at the time of controlling the iris to an opening direction and a closing direction. A conversion signal for generating the iris drive signal is obtained by the control means. At the time of controlling the iris to the opening direction and the closing direction, the characteristics are made the same so that operation convenience can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus having an auto iris function. Specifically, by making the amount of change in the amount of light per unit control time equal between the opening direction and the closing direction of the auto iris unit, even if the opening and closing control characteristics of the auto iris unit vary, the control characteristics can be leveled. It is like that.

[0002]

2. Description of the Related Art Some commercial or home-use image pickup apparatuses such as video cameras have an optical lens system equipped with an auto iris function. The auto iris function adjusts an iris (aperture) according to external light so that a subject image always having a constant light amount is formed on the image sensor.

A DC servo lens is usually used as an optical lens system having an auto iris means, and a servo lens drive signal is supplied from a driver (both not shown), and the iris is opened and closed according to the value. The servo lens drive signal is a luminance signal Y generated from the imaging signal.
It is common to generate more.

The relationship between the level of the obtained luminance signal Y of the subject image and the servo lens drive signal (DC level) for controlling the iris aperture state is given as a curve La in FIG. As in this example, the intermediate luminance level Yr
When the level (DC gain level) of the servo lens drive signal given to the driver at ef is intermediate (DCG center), and when the luminance level becomes larger than the reference level Yref, the level of the servo lens drive signal is changed to DCG.
Direction to narrow the iris by raising in the max direction (close direction)
To control. Conversely, when the luminance level falls below the reference level Yref, the level of the servo lens drive signal is lowered in the DCGmin direction to control the iris to open (opening direction).

[0005]

By the way, the relationship between the brightness level of the imaged subject and the servo lens drive signal is as follows.
FIG. 7 shows the opening and closing time of the iris when the curve La is as shown in FIG.

In FIG. 8, a curve Lb shows the relationship between the control time when the iris is controlled in the opening direction and the luminance level at that time. A curve Lc shows the relationship between the control time and the brightness level when the iris is controlled in the closing direction.

As is apparent from these curves Lb and Lc, in the DC servo lens used in this example, by controlling the iris in the opening direction, the luminance level Y is reduced to the minimum value Ymi.
The time Tb required to change from n to the maximum value Ymax is longer when the iris is controlled in the closing direction to change the luminance level Y from the maximum value Ymax to the minimum value Ymin.

That is, even when the same servo lens drive signal is applied, the time when the iris is narrowed is shorter than the time when the iris is opened, and the opening / closing time differs depending on the opening / closing direction. As described above, the iris change amount per unit time differs depending on the iris opening / closing direction, so that the usability is poor. If possible, it is preferable that the iris change amount is constant regardless of the iris opening / closing direction.

Also, the amount of iris change per unit time varies somewhat depending on the mounted auto iris mechanism and the optical lens system used, and the variation cannot be determined without actually operating it. In consideration of the variation, the control characteristic is set so as to have a control characteristic as shown by a curve La in FIG. Therefore, the actual control characteristics are not optimal for the mounted auto iris mechanism.

Furthermore, even when the imaging environment is dark,
Since the iris control characteristics are constant even when the brightness is high, that is, when the illuminance is low and the illuminance is high, the iris adjustment ends more quickly at the time of high illuminance. This is because the opening range (adjustment range) of the iris is much narrower at high illuminance than at low illuminance.

Therefore, the present invention has been made to solve such a conventional problem. In particular, by making the iris change amount constant regardless of the iris opening / closing direction,
It is an object of the present invention to propose an imaging device that can realize more stable iris control.

[0012]

In order to solve the above-mentioned problems, in the image pickup apparatus according to the present invention described in claim 1,
An image pickup device for picking up an image of a moving object, an optical lens system having an auto iris means provided at a preceding stage thereof, a signal processing unit for generating a video signal from an image pickup signal obtained from the image pickup device, and an output signal from the signal processing unit. Control means for detecting the level of a luminance signal in the video signal, and setting means for setting a control characteristic for the auto iris means based on the level of the luminance signal. The automatic iris means is controlled based on an iris drive signal set by the means.

According to the present invention, when the iris is controlled in the opening direction and when the iris is controlled in the closing direction,
The iris drive characteristics are selected so that the iris change amount (light amount change amount) with respect to the unit control time becomes equal. By doing so, the iris change amount becomes constant regardless of the iris opening / closing direction. Therefore, even if the auto iris mechanism used varies, more stable iris control can be realized and usability is improved.

By controlling the iris drive characteristic (controlling the inclination of the characteristic) by the brightness of the external light, it is possible to achieve the same amount of iris change per unit time even at high illuminance as at low illuminance.

[0015]

Next, an embodiment of an image pickup apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 shows an embodiment of an image pickup apparatus 10 according to the present invention. An object 12 is formed on an image pickup device 16 via a lens system 14, and an image pickup signal corresponding to the object image is obtained. As the lens system 14, an optical lens system equipped with an auto iris mechanism is used. Therefore, a DC servo lens is used as the optical lens system.

As the imaging device 16, a solid-state imaging device such as a CCD can be used. As the image sensor 16, a color image sensor is usually used. The imaging signal output from the imaging element 16 is subjected to correlated double sampling (CDS) processing of the obtained imaging signal in the pre-signal processing unit 18 and automatic gain adjustment of the correlated double sampling processed imaging signal. (AGC) processing is performed. Further, in this embodiment, an A / D conversion process is performed on the imaging signal whose gain has been adjusted, because the digital signal is processed in this embodiment.
It is converted into a digital signal of a predetermined number of bits.

In the main signal processing section 20, a video signal composed of a luminance signal Y and a color signal C is generated in the main signal processing section 20 from the digitally converted image pickup signal. A DSP (Digital Signal Processor) circuit is used as the main signal processing unit 20,
The above-described video signal conversion processing is performed by this DSP circuit. This video signal can be supplied to an external circuit via the output terminal 22.

Among the video signals, in this example, the luminance signal Y is supplied to a control means 24 constituted by a microcomputer. The control means 24 outputs a converted signal for generating an iris drive signal for performing auto iris from the obtained luminance signal Y, and the converted signal is supplied to an electronic volume circuit (EVR) 26 to be converted to a luminance level. FIG. 7 in response
An iris drive signal as shown in FIG.

The converted signal is a signal corresponding to the level of the luminance signal Y. As is clear from the curve La, the converted signal is output as a signal in which the luminance signal Ya and the luminance signal Yb are constant.

Therefore, in the electronic volume circuit 26, when the level of the luminance signal Y which is the conversion signal is equal to or lower than Ya, it is converted into the minimum iris drive signal DCGmin, and when the level is equal to or higher than Yb, it is converted into the maximum iris drive signal DCGmax. . The iris drive signal is supplied to the auto iris means 14 via the driver 28, and the iris is opened and closed according to the level of the iris drive signal.

When the level of the luminance signal Y becomes higher than the reference value Yref, for example, the iris drive signal is controlled to increase the level of the iris by the iris drive signal, and conversely when the level of the luminance signal Y becomes lower than the reference value Yref. The iris is controlled to open.

By the way, if the iris drive signal is as shown in FIG. 7, the amount of iris change per unit time of the iris at that time becomes a curve Lb or Lc in FIG. 8, and the iris change differs depending on the opening / closing direction of the iris. Resulting in.

Therefore, the present invention prevents the iris change amount from changing depending on the opening / closing direction of the iris. For example, as shown in FIG. 2, the iris change amount when the iris is controlled in the opening direction (curve Lb ′) is equal to the iris change amount when the iris is controlled in the closing direction (curve Lc ′). The iris change amount in the closing direction is made slow (curve Lc → Lc ′).

In this example, the time for controlling the iris in the opening direction is controlled to be slightly faster than in the conventional case (curve Lc → Lc ′). Therefore, the control time in the opening direction is slightly shorter from Tb to Tb ', and the control time in the closing direction is slightly longer as Tc to Tc'. In the control means 24, a conversion signal corresponding to the level of the input luminance signal Y is generated so as to have iris drive characteristics like the curves Lb 'and Lc' in FIG.

When such an iris control characteristic is selected, the level of the luminance signal Y and the iris drive signal (DC gain signal) added to the iris are lower than the reference value Yref of the luminance signal Y as shown by a curve La 'in FIG. The change amount of the iris drive signal in a high control range is suppressed as compared with the conventional case. That is, the amount of iris change per unit time when narrowing down the iris is reduced.

As a result, as shown in FIG. 2, the iris change amount when the iris is changed in the opening direction is substantially equal to the iris change amount when the iris is changed in the closing direction. Irrespective of the opening / closing direction, the iris change amount can be made uniform. Thereby, more stable iris adjustment can be realized. Usability is also improved. By making the iris control characteristics as shown in FIG. 2,
It can also absorb variations in the auto iris mechanism.

In the above-described embodiment, the iris change amount when the iris is opened is controlled so that the iris change amount when the iris is controlled in the closed direction is equal to the iris change amount when the iris is controlled in the open direction. And the iris change amount in the closing direction were both adjusted. Of course, if it is possible to match the iris change amount in the closing direction with the iris change amount in the opening direction, on the contrary, it is converted to match the iris change amount in the opening direction with the iris change amount in the closing direction. Characteristics can also be adjusted. In the former case, the iris can be adjusted accurately, and in the latter case, the iris can be adjusted quickly. FIG. 4 shows an example of the relationship between the level of the luminance signal Y and the iris drive signal when the latter is selected.

The driving characteristics of the iris shown in FIG.
Since it may be different depending on the auto iris mechanism used, it is important to adjust the driving characteristics so as to match the auto iris mechanism.

When the imaging device 10 is used indoors after being used indoors, or when the imaging device 10 is used outdoors or vice versa, the brightness of the external light changes significantly. When the brightness of the external light greatly changes, the iris adjustment range also changes.

For example, when the iris adjustment range (opening range) at low illuminance is Wa in FIG. 5 and the iris adjustment range at high illuminance is Wb, the iris change amount per unit time at low illuminance, that is, the light amount change It can be seen that the amount and the amount of change in the amount of light per unit time at high illuminance are significantly different. In other words, the amount of change in the amount of light is significantly larger at the time of high illuminance.
For this reason, the luminance level per unit time greatly changes due to the iris adjustment at the time of high illuminance.

In order to solve this problem, the control means 24 may generate a conversion signal that makes the change of the iris drive signal slow with respect to the change of the luminance level at the time of high illuminance. That is, when the relationship between the luminance level before adjustment and the iris drive signal is represented by the curve Ld in FIG. 6, the curve Ld is adjusted so as to have a gradual characteristic change like the curve Ld ′. Then, the change in the value of the iris drive signal with respect to the change in the luminance level is reduced, and the opening / closing amount of the iris is reduced accordingly. As a result, it is possible to suppress a sudden change in the luminance level due to a sharp opening and closing of the iris.

In order to realize the iris drive characteristic as shown in FIG. 6, a reference value for detecting a change in illuminance is determined for the luminance level Y supplied to the control means 24. And when the amount of light change per unit time exceeds this reference value, such as when going out from indoor to outdoor,
It is determined that the external light has changed from low illuminance to high illuminance, and the conversion characteristic for the luminance level at that time is changed as shown by the curve Ld ′ in FIG. If the conversion characteristic for obtaining the iris drive signal is also changed with such a change in illuminance,
Appropriate iris control can be realized even at high illumination.

[0033]

As described above, in the present invention, the amount of change in the amount of light per unit time is constant regardless of the iris opening / closing direction.

According to this, almost the same iris control characteristics are obtained when the iris is controlled in the opening direction and when the iris is controlled in the closing direction, so that the usability is improved. Of course, if the iris control characteristics are selected in this way, even if there is a variation in the iris control characteristics of the auto iris mechanism, this variation can be absorbed by appropriately selecting the iris control characteristics. In addition, when the camera is used in an environment with greatly different illuminance, the same iris control can be realized at low and high illuminance by adjusting the sensitivity of the iris control characteristic. Will be able to

[Brief description of the drawings]

FIG. 1 is a system diagram of a main part showing an embodiment of an imaging apparatus according to the present invention.

FIG. 2 is a characteristic diagram showing a relationship between an iris adjustment time and a luminance level.

FIG. 3 is a characteristic diagram illustrating a relationship between a luminance level and an iris drive signal (part 1).

FIG. 4 is a characteristic diagram illustrating a relationship between a luminance level and an iris drive signal (part 2).

FIG. 5 is a diagram showing an iris use area at low illuminance and at high illuminance.

FIG. 6 is a characteristic diagram showing a relationship between a luminance level and an iris drive signal at that time.

FIG. 7 is a characteristic diagram showing a relationship between a luminance level and an iris drive signal.

FIG. 8 is a characteristic diagram showing a relationship between an iris adjustment time and a luminance level.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Imaging device, 14 ... Optical lens system including an auto iris mechanism, 16 ... Image sensor, 20 ...
Main signal processing unit, 24 ... Control unit as detection means, 2
6 Electronic volume circuit, 28 Driver

Claims (3)

[Claims] 1. An image pickup device for picking up an image of an object, an optical lens system having an auto iris means provided at a preceding stage thereof, a signal processing unit for generating a video signal from an image pickup signal obtained from the image pickup device, Control means for detecting the level of a luminance signal among the video signals output from the section, and the control means includes setting means for setting a control characteristic for the auto iris means based on the level of the luminance signal. An image pickup apparatus, wherein the auto iris means is controlled based on an iris drive signal set by the setting means. 2. An iris drive signal in which the amount of change in the amount of light with respect to a unit control time is equal between when the iris is controlled in the opening direction and when the iris is controlled in the closing direction. The imaging device according to claim 1, wherein: 3. The control means detects illuminance of external light,
2. An image pickup apparatus according to claim 1, wherein the iris control characteristic of said setting means is controlled such that the iris change amount at high illuminance becomes slower than the iris change amount at low illuminance. apparatus.