JPS63304234A - Controller for depth of field to be photographed - Google Patents

Abstract

PURPOSE:To continuously adjust the depth of field to be photographed without altering an outputted video level by adjusting any one of the sensitivity of a pickup means, the light attenuation quantity of a variable density filter and the gain of a signal process part according to F value information from a diaphragm mechanism. CONSTITUTION:Light beam from an object condensed by a lens 4, after adjusting its light quantity by the diaphragm 5, is formed with an image on a pickup tube 6, where an optical image is converted into an electrical signal and outputted to a signal process part 7 in a poststage. In this case, the sensitivity of the pickup tube 6 is automatically adjusted with the output from a converter 8 so as not to alter the outputted video level by using the information of F value outputted from the diaphragm 5. Namely, any one of the light attenuation quantity of the variable density filter set on the front surface of the pickup tube 6, the sensitivity of the pickup tube 6 and the gain of the signal process part is automatically adjusted. Thus, the depth of the field to be photographed can be continuously controlled with the image level constant even if the F value is altered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Applicability Meter] The present invention relates to a depth of field control device for controlling the depth of field of an imaging device having an aperture mechanism, such as a television camera.

[Prior Art] Fig. 4 shows the positional relationship between a camera 1 such as a television camera and two subjects 2.3.As shown in this figure, the subjects 2.3 are on a straight line when viewed from the camera 1. If the depth of field of camera 1 is shallow and the distance is slightly different from that of subject 2 or 3, if you focus on either subject 2 or 3, the image obtained from camera 1 will be as shown in Figure 5. As shown in Figure 6, the other subject becomes blurred.In order to avoid this blur, the depth of field of camera 1 must be increased, and by increasing the depth of field, as shown in Figure 6. Both subjects 2 and 3 are in focus.

However, in order to perform this depth of field adjustment, the aperture of the lens of camera 1 must be closed down, and at the same time, the output level (brightness) of the image signal obtained from camera 1 must be adjusted to match the aperture. It is necessary to maintain the output level of the previous image signal. In this type of depth of field adjustment that is commonly performed with conventional devices, in order to deepen the depth of field, the F value of the aperture of camera 1 is increased, and the focus on subject 2.3 is adjusted. In order to brighten the lighting and reduce the depth of field under the same lighting conditions, there is a
An O filter (density filter) is often inserted to reduce the F number of the lens aperture.

[Problems to be Solved by the Invention] However, in such a conventional device, an NO filter corresponding to the amount of light attenuation due to aperture adjustment is selected from a plurality of ND filters prepared in advance and inserted into the optical path of the camera 1. Therefore, not only was the operation troublesome, but it was also impossible to continuously transition from the blurred state shown in FIG. 5 to the clearly focused state shown in FIG. 6.

The purpose of the present invention is to eliminate the above-mentioned drawbacks and to continuously increase the depth of field while keeping the output image level constant! ! An object of the present invention is to provide a depth of field control device for an imaging device that can control IJ.

[Means for Solving the Problems] In order to achieve the above object, the present invention adjusts the sensitivity of the imaging means,
(h) Automatically controlling at least one of the optical attenuation of a variable density filter disposed in the input optical path of the imaging means and the gain of a signal processing section subsequent to the imaging means so that the output video signal is at a constant level. It is characterized by comprising a control means.

[Function] In the present invention, information on the F number (aperture ratio) of the aperture is used to determine the amount of light attenuation of the variable density filter installed in front of the imaging means,
At least one of the sensitivity of the variable-sensitivity imaging means and the gain of the signal processing unit is automatically adjusted, so even if the F value is changed, the image level can be kept constant at automatic fishing. Moreover, the depth of field can be continuously controlled while keeping the image level constant.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of an embodiment of the present invention. In this figure, 4 is an imaging lens that condenses light from a subject, and 5 is a diaphragm (for example, an iris diaphragm) that limits the amount of light passing through the lens 4. ), 6 is an image pickup tube that converts the optical image formed by the lens 4 into an electrical signal by photoelectric conversion, and 7 is a signal processing section that processes the output signal of the image pickup tube 6 and outputs a video signal.

Further, 8 is a converter that converts information on the F value (F number) obtained from the aperture 5 into a sensitivity control signal (for example, target voltage control No. 48) for the image pickup tube 6. As the above-mentioned image pickup tube 6, for example, a known variable sensitivity type image pickup tube whose sensitivity can be adjusted by changing the target voltage applied to the target is used.

In the above configuration, the light from the subject is focused by the lens 4, and after the amount of light is adjusted by the diaphragm 5, an image is formed on the image pickup tube 6, and the optical image is converted into an electrical signal by the image pickup tube 6. , and is output to the subsequent signal processing section 7. that time,
As is well known, the depth of field is determined by the F value (aperture ratio) of the aperture 5, so in order to obtain the desired depth of field, the F value of the aperture 5 can be changed. However, if the F value is simply changed by adjusting the aperture 5, the amount of light of the optical image formed on the image pickup tube 6 will change, so the output level of the video signal output from the signal processing section 7 will change. It ends up.

In the case of normal shooting, it is preferable that the brightness of the output image does not change even if the depth of field is changed, so in order to avoid the output level of the output video signal changing according to the depth of field adjustment, In the example, the sensitivity of the image pickup tube 6 is automatically adjusted using the output of the converter 8 using information on the F number output from the aperture 5 so that the output video level does not change.

Next, the characteristics of the converter 8 will be explained.

The necessary F value can be obtained by driving and controlling the ribbon 5 using, for example, a motor. In this case, the control voltage Vm of the motor can be used as the F value information. in this case,
The relationship between the F value and Vn can be expressed as F = f (Vm). Further, the brightness Jlt of the optical image on the image pickup tube 6 is the original light amount β. Then, it is proportional to 1/2 of the F value.

Next, the relationship between the output signal level Is of the image pickup tube 6 and the sensitivity control voltage (target voltage) Vt of the image pickup tube 6 is expressed as Is=g (vt) ·x.

If it is expressed as Vt"g 1s/l1r), then vt becomes.The converter 8 provides the relationship between this vt and Vm.
The converter 8 is, for example, a square-law characteristic amplifier or an RO
It can be configured using an M (read-only memory) table or the like. Note that Is/42° is set in advance to a desired constant value.

In this way, since the sensitivity of the image pickup tube 6 is automatically adjusted according to the adjustment of the aperture 5, the depth of field can be continuously adjusted without changing the output level of the video signal from the signal processing section 7. Can be controlled. In this example, 6 is an image pickup tube, but the present invention is not limited to this, and for example, a solid-state image pickup device with adjustable sensitivity can also be used.

FIG. 2 shows the configuration of a second embodiment of the invention.

In this figure, 9 is a variable NO filter (variable concentration filter) whose light transmittance can be adjusted by the applied voltage input from the converter 8. The variable NO filter 9 is, for example, PLZT, which is a type of ferroelectric material. (PZT doped with La) is well known. This PLZT element can continuously adjust the light transmittance by changing the applied voltage.

Further, as the variable ND filter 9, any type of filter that can continuously change the concentration of transmitted light, such as one using liquid crystal, can be used.

This example is a case where an image sensor 61 whose imaging sensitivity cannot be made variable can be used, and instead of adjusting the sensitivity of the image sensor 61, a variable NO filter 9 is used to adjust the amount of light input to the image sensor 61 according to changes in the F value. It is controlled by a converter 8 to keep it constant. As the converter 8, one having characteristics determined by a method substantially similar to that of the embodiment shown in FIG. 1 can be used.

FIG. 3 shows the configuration of a third embodiment of the present invention.

This example is a case where an image sensor 61 whose imaging sensitivity cannot be varied is used and a variable N1) filter is not used. That is, instead of adjusting the sensitivity of the image sensor 61, the signal processing section 7
converter 8 so that the output video level does not change at
Adjust the video level using the control signal. In this case, the gain (amplification degree) of the signal processing section 7 may be changed according to the control signal of the converter 8. As the converter 8, one having characteristics determined by a method substantially similar to that of the embodiment shown in FIG. 1 can be used.

[Effects of the Invention] As explained above, according to the present invention, at least one of the sensitivity of the imaging means, the amount of light attenuation of the variable density filter, and the gain of the signal processing section is adjusted according to the F-number information obtained from the diaphragm mechanism. Since the depth of field can be adjusted continuously without changing the output video level, it is possible to adjust the blurring of the subject that is necessary for the production of images obtained from this device. In particular, when there are multiple subjects, the mutual blurring can be adjusted freely without deteriorating the image quality, and a great effect on the production can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of the second embodiment of the present invention, and FIG. 3 is the third embodiment of the present invention. Figure 4 is a plan view showing an example of the positional relationship between the camera and the subject, Figure 5 is a block diagram showing an example of the positional relationship between the camera and the subject, and Figure 5 is a block diagram showing an example of the positional relationship between the camera and the subject. Figure 6 is an explanatory diagram showing an example of an image obtained when the image is taken with only one object in focus. Figure 6 is an example of an image obtained when the subject in the positional relationship shown in Figure 4 is similarly imaged with a deep depth of field and both subjects are in focus. It is an explanatory diagram showing an example of an image obtained when doing so. 1... Camera, 2.3... Subject, 4... Lens, 5... Aperture, 6... Image pickup tube, 7... Signal processing section, 8... Converter, 9. ...Variable ND filter, 61...Image sensor. Ma imaging

Claims (1)

[Claims] 1) Depending on the F value (aperture ratio) information obtained from the diaphragm mechanism, the sensitivity of the imaging means, the amount of optical attenuation of a variable density filter placed in the input optical path of the imaging means, and the signal at the downstream stage of the imaging means 1. A depth of field control device for an imaging device, comprising a control means for automatically controlling at least one gain of a processing section so that an output video signal is at a constant level.