JPH08334725A - Light shielding device for photographing lens part - Google Patents

Abstract

PURPOSE: To eliminate the harmful light entering from the outside of a photographing viewing angle and also to eliminate the unbalance of light quantities on a photographing surface without reducing effective diameters of lenses. CONSTITUTION: A diaphragm 5, a diaphragm driving part 11 and a position detector 12 are provided in the lens barrel 10 of photographing lenses and a mode selection switch 30 performing the changeover to a ghost eliminating mode, an auto iris part (18, 19, 21) including a first switch 20, a diaphragm control part (21, 22, 23) including a second switch 24 and a condition judging part (26, 27, 28, 29) are provided in this device. Then, when the device is changed over to the ghost eliminating mode, the harmful light becoming the cause of a ghost is eliminated by turning the first switch 20 OFF, turning the second switch 24 ON and by limiting the diaphragm 5 to a prescribed stop value smaller than an opened value. Thus, a light shielding body, etc., are not required to be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shading device for a photographing lens unit, and more particularly to control of a shading device for removing a ghost caused by harmful light from outside a photographing field angle in a photographing lens unit such as a television camera or a video camera.

[0002]

2. Description of the Related Art FIG. 4 shows an example of the construction of a photographing lens section in a conventional television camera or video camera. In the lens barrel of this photographing lens section, a first lens group 1,
A second lens group 2, a third lens group 3, and a fourth lens group 4 are provided, and a diaphragm 5 is arranged between the second lens group 2 and the third lens group 3. A CCD (Charge Coupled Device) 6 is arranged behind the fourth lens group 4, and light passing through each of the lens groups 1 to 4 and the diaphragm 5 forms an object on the imaging surface of the CCD 6. It will be a statue.

[0003]

By the way, in such an image pickup apparatus, when extremely strong light from the sun or the like enters from outside the photographing field angle set by the photographing lens unit, the light is reflected on the lens surface or the mirror. There is a problem in that the light is reflected by the inner wall of the body and reaches the image pickup surface of the CCD 6 to generate a ghost on the shooting screen. That is, when shooting outdoors on a sunny day, the aperture 5 is used with the aperture slightly reduced, but for example, in shooting on the telephoto side where the angle of view is narrow, when shooting dark trees or plants in the background, The iris opens and ghost occurs. Particularly, in a photographing lens unit configured by superposing lenses in multiple layers, sunlight or the like is multiply reflected, and a light flux that causes a ghost is complicatedly generated.

FIG. 5 shows light that causes a ghost in the first lens group 1. If the first lens group 1 is composed of three lenses 1A, 1B and 1C, For example, the sun rays 101 are totally reflected by the surface S3 of the lens 1C and travel toward the second lens group 2 and the diaphragm 5 in the locus shown. Further, the sun rays 102 are reflected by the surface S1 of the lens 1A and, although not shown, are also reflected by the surface S2 of the lens 1B and travel toward the second lens group 2. Such multiple reflection causes a ghost. .

Therefore, conventionally, as shown in FIG. 4, a light-shielding paper 7 and light-shielding bodies 8 and 9 are provided on the lower side inside the lens barrel, and as shown by a chain line incident path (chain line), For example, the sunlight rays (partial light rays) 103 that enter the first lens group 1 from above are blocked by the light shield 8 and are prevented from entering the lens barrel. The reason why the light shields 8 and 9 are provided on the lower side inside the lens barrel is that sunlight is incident from the upper side and a light flux that causes a ghost often passes through the lower side. is there.

However, since the light shields 8 and 9 as described above are arranged within the aperture diameter of the lens frame of each of the lens groups 1 to 4, the effective aperture of the lens is unnecessarily reduced, and the diaphragm 5 is used. There was a problem that the F number when opening was increased.

Moreover, even the above-mentioned light shields 8 and 9 have a problem in that the unnecessary light flux that causes a ghost cannot be sufficiently removed. For example, as shown in FIG. 4, the sun rays 101 (same for 102) shown in FIG.
Is not shielded by the light shields 8 and 9, and passes through the diaphragm 5 when opened. In particular, if the above-mentioned sun rays 101 are totally reflected by the lens surface S3, this is a major cause of ghosts. In order to prevent the incidence of such light rays 101, 102, it is necessary to increase the size of the light shields 8, 9. It will be good. However, in this case, since only the lower luminous flux is removed, there is an inconvenience that the amount of light on the image pickup surface is unbalanced. Further, when the light shield 8 is made large, there is a limit that the lens 2 interferes at the wide end. When the light shield 9 is made larger, the F number surely becomes larger.

The present invention has been made in view of the above problems, and an object thereof is to remove harmful light incident from outside the photographing field angle as needed without reducing the effective aperture of the lens, and An object of the present invention is to provide a light-shielding device for a photographing lens unit that does not cause an imbalance in the amount of light on the imaging surface.

[0009]

In order to achieve the above object, a light-shielding device according to the present invention includes a switch for selecting a ghost elimination mode and a switch for selecting a ghost elimination mode in a photographing lens unit having an aperture drive mechanism. When operated, the aperture of the aperture drive mechanism is limited to a predetermined aperture value smaller than the open value, and an aperture control circuit for removing harmful light causing ghost is provided.

[0010]

According to the above construction, normally, the aperture value is controlled by the auto iris control so that the aperture value becomes the optimum exposure value. However, when the mode selection switch is pressed by the photographer's judgment to switch to the ghost elimination mode. The iris control circuit limits the iris to a predetermined value before the maximum aperture value, thereby removing extra harmful rays caused by multiple reflections of the lens group. In this case, the harmful rays are removed not only in the lower region but also in all azimuth directions of the diaphragm, so that the imbalance of the light amount on the imaging surface does not occur.

On the other hand, when the mode selection switch is not pressed, the aperture is not limited. Therefore, by setting the effective aperture of the lens large, it is possible to reduce the F number when the aperture is opened.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of a light-shielding device for a photographing lens section according to an embodiment. In FIG. 1, a lens barrel 10 has a first lens group 1 and a second lens. A group 2, a third lens group 3 and a fourth lens group 4 are provided, and a diaphragm 5 is arranged between the second lens group 2 and the third lens group 3. The diaphragm 5 is provided with a diaphragm drive (motor) unit 11 and a position detector (Hall element) 12, and the position detector 12 detects the position of the diaphragm, that is, the diaphragm value.

2A and 2B show the configurations of the various diaphragms 5. In FIG. 2A, a square opening is formed by four blades 14 in the diaphragm opening (open state) 13. 6B, the hexagonal opening is formed by the six blades 14.
In the embodiment, the exposure is controlled by the diaphragm 5 as described above, but in the ghost removal mode of the embodiment, the aperture value is smaller than the opening value by 1/2 to 1 step (for example, the opening F number is 1. F number 2.
14 to 2.54), that is, the aperture value that can remove the ghost. An image pickup circuit 16 including a CCD as an image pickup device is connected to the lens system of the lens barrel 10 as described above, and a video signal processing circuit 17 is connected to the image pickup circuit 16. Thus, image processing for display on a monitor or the like is performed.

As an auto iris unit, a gain amplifier 18 for inputting the luminance signal output from the video signal processing circuit 17, and a difference between the luminance signal voltage V1 as an output of the gain amplifier 18 and the exposure level signal voltage V2 is amplified. A differential amplifier 19 for outputting, a first switch (analog switch) 20, and a drive amplifier 21 are provided. This auto iris unit is a circuit which has been conventionally used. The differential amplifier 19 amplifies the difference voltage between the exposure level signal voltage V2 and the luminance signal voltage V1, and when the first switch 20 is closed (when it is on). ), The diaphragm drive motor 11 is driven based on this difference voltage.

Further, as a diaphragm limiting (servo iris) section, a gain amplifier 22 for inputting the detection output of the position detector 12 and a difference voltage between an output voltage V4 of this gain amplifier 22 and a comparison voltage V5 corresponding to the limiting diaphragm value are provided. A differential amplifier 23 for amplification, a second switch (analog switch) 24, and the drive amplifier 21 described above are provided. This aperture limiting circuit is configured such that when the second switch 24 is closed and the first switch 20 is open (OFF), a predetermined aperture value is output by the output of the differential amplifier 23 based on the output of the position detector 12. The aperture will be limited so that the above is not exceeded.

Further, as a condition judging unit, a comparator 26 for judging the polarity of the output of the differential amplifier 19 and a predetermined diaphragm value (maximum value of restriction) which is a limit value (aperture value capable of removing ghost) are determined. A variable resistor (VR) device 27 for setting the comparison voltage V5, a comparator 28 for comparing the comparison voltage V5 set by the variable resistor 27 with the output of the gain amplifier 22, and these comparators 26, 28.
An AND circuit 29 is provided for inputting the outputs L1 and L3 of.

On the other hand, a mode selection switch 30 for switching to the ghost elimination mode is provided in the operation section or the like, and the output of this switch 30 is supplied to the AND circuit 29. Therefore, the AND circuit 29 supplies the High signal to the first switch 20 when the outputs of the selection switch 30 and the outputs of the comparators 26 and 28 are input (L1, L2, L3), and thereby the first switch 20 is supplied. The first switch 20 can be turned off and the second switch 24 can be turned on.

The embodiment is constructed as described above, and its operation will be described below. First, in normal photographing, since the mode selection switch 30 is not operated, the output of the AND circuit 29 in FIG. 1 is at the Low level regardless of the input states of the other inputs L1 and L3. The switch 24 is turned off and the first switch 20 is turned on. At this time, the above-mentioned auto iris section becomes effective. Therefore, the differential amplifier 19 amplifies the difference voltage between the exposure level signal voltage V2 and the luminance signal voltage V1 and supplies this difference voltage to the diaphragm drive motor 11 via the drive amplifier 21 to drive the diaphragm 5. To be done. Then, by performing feedback control so that the brightness signal voltage V1 becomes equal to the exposure level signal voltage V2, the aperture value of the diaphragm 5 is controlled to the value set by the exposure level signal.

On the other hand, when the photographer desires to switch to the ghost elimination mode depending on the shooting conditions and operates (turns on) the mode selection switch 30, the high-level input L2 from the switch 30 is the AND circuit of the condition judging section. 29
Supplied to In this AND circuit 29, this input L2
And the logical product of the input L1 which is the output of the comparator 26 and the input L3 which is the output of the comparator 28. As described above, the comparator 26 determines the polarity of the differential amplifier 19, and the brightness signal voltage V
If the difference voltage V3 between 1 and the exposure level signal voltage V2 has a positive (+) polarity, it has a high level, and if it has a negative (-) polarity, it has a low level. That is, when the difference voltage V3 has a positive polarity, the diaphragm blades 14 (15) are opened, and when the difference voltage V3 has a negative polarity, the diaphragm blades 14 (15) are closed. The comparator 26 determines whether or not the diaphragm blade 14 (15) is in the opening direction, and outputs a high level signal in the opening direction.

On the other hand, the comparator 28 has a comparison voltage V set by the variable resistor 27 as a predetermined limiting aperture value.
5 and the gain amplifier 2 as the detection value at the position detector 12
The output voltages V4 are compared with each other, and when the voltage V4 exceeds the voltage V5 (V4> V5), the level becomes High, and when the voltage V4 is smaller than the voltage V5 (V
4> V5), Low level. That is, the comparator 2
Reference numeral 8 determines whether or not the voltage V4 as the position detection value exceeds the comparison voltage V5 corresponding to the limit aperture value. When the current aperture value is a value on the open value side of the limit aperture value, the high level Output a signal.

Therefore, in the AND circuit 29, the mode selection switch 30 is turned on and the diaphragm blade 14 is turned on.
When (15) is controlled in the opening direction and the current aperture value is on the open value side of the limit aperture value, a high level output is produced. The output of the AND circuit 29 is supplied to the first switch 20 through the inverter, so that the first switch 20 is turned off and the second switch 24 is input as it is. Is turned on, which causes the diaphragm limiting unit including the differential amplifier 23 to operate.

In this aperture limiting section, the differential amplifier 23 amplifies the difference voltage between the comparison voltage V5 set by the variable resistor 27 and the voltage V4 detected by the position detector 12, and based on this difference voltage. The diaphragm 5 is driven. As a result, the aperture 5 is fixed to a predetermined limit value. In the embodiment, for example, in the case of FIG. 2A, the aperture amount is limited to the right side state by the aperture blade 14, and the aperture amount of FIG. )In the case of,
The aperture amount is limited to the right side by the diaphragm blade 15. Further, FIG. 3 shows a state of sunlight incident from outside the photographing field angle when the aperture amount is limited, and the sun ray 101 that causes a ghost is, as shown in FIG. It will be blocked by the blades 14, 15) 5.

After that, when the brightness of the subject changes, the exposure level signal voltage V2 decreases, and the output voltage V3 of the differential amplifier 19 turns to negative (V3 <0), the AND circuit 2
The input L1 of 9 becomes low level. Therefore, the output of the AND circuit 29 becomes low level, and the second switch 24
Is turned off, the first switch 20 is turned on, and as a result, the auto iris control is resumed.

As described above, in the embodiment, in normal shooting, good exposure control without restriction of the aperture value of the diaphragm 5 can be performed based on the auto iris control of the diaphragm 5,
It is also possible to set a small F number when opening the. Further, in shooting where a ghost occurs, by operating the mode selection switch 30 in advance by the photographer's judgment and selecting the ghost removal mode, harmful light can be removed and a good image can be obtained. Becomes

Further, the light-shielding device having such a restriction of the diaphragm has an advantage that harmful light incident from all azimuth directions can be removed. That is, since sunlight that causes a ghost enters the lens portion of the camera arranged at the regular position from the upper side, it may pass through the lower side as shown in FIGS. 3 and 4 in the lens barrel. Many, and therefore the light shields 8, 9 are arranged on the lower side. However, since such harmful light is incident from diagonally above as well, it passes through the lens barrel in the lower range of 180 degrees, and in the case of a video camera or a camera that projects on film, the camera itself is 90 degrees. I often rotate it for shooting. However, in the present invention, as shown in FIG. 2, since the diaphragm aperture 13 is entirely diaphragmed by the diaphragm blades 14 (15), it is possible to favorably remove harmful light passing through in all directions in the lens barrel. There is.

In the above embodiment, as shown in FIG. 3, the light shield 8 and the like may be provided within a range in which the effective diameter of the lens (opening value of the diaphragm) is not limited.

[0027]

As described above, according to the present invention,
A mode selection switch is provided, and when this switch is operated, the aperture of the aperture drive mechanism is limited to a predetermined aperture value.Therefore, it is possible to prevent harmful light entering from outside the shooting angle of view without reducing the effective aperture of the lens. Light can be removed as needed to ensure ghosting is eliminated. Moreover, there is no imbalance in the amount of light on the imaging surface, and good shooting is possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a light blocking device of a photographing lens unit according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration example of a diaphragm according to an embodiment.

FIG. 3 is a diagram showing a locus of sun rays incident on the taking lens unit of the embodiment from outside the photographing field angle.

FIG. 4 is a diagram showing a configuration of a conventional photographing lens unit and a locus of a sun ray incident on the photographing lens unit from outside a photographing angle of view.

FIG. 5 is a diagram showing multiple reflections of sun rays by the first lens group of FIG.

[Explanation of symbols]

 1, 2, 3, 4 ... Lens group, 5 ... Aperture, 12 ... Position detector, 14, 15 ... Aperture blade, 19, 23 ... Differential amplifier, 20 ... First switch, 24 ... Second switch, 26, 28 ... Comparator, 29 ... AND circuit.

Claims (1)

[Claims] 1. A photographing lens unit having an aperture drive mechanism, wherein a switch for selecting a ghost elimination mode and a predetermined aperture value smaller than an open value of the aperture of the aperture drive mechanism when the switch is operated. And a diaphragm control circuit for removing harmful light that causes ghosts, and a shading device for a photographing lens unit.