JPH0954242A - Optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve probability for enabling focus detecting operation. SOLUTION: When second illumination means 202, 212 illuminating outside world corresponding to plural regions in a screen are mounted in an optical device, the second illumination means 202, 212 are selected as auxiliary light at the time of detecting a focus even when either a first mode for detecting focusing states in at least two and more places in the plural regions or a second mode for detecting focusing state in a prescribed region in the plural regions is selected. When a third illuminating means illuminating an outside world corresponding to a prescribed region in the plural regions is mounted in the optical device, an auxiliary light selecting means 100, for selecting first illuminating means 102, 112 for illuminating the outside world corresponding to plural regions in the optical device in a first mode and a third illuminating means in a second mode, is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an optical device such as a camera equipped with an automatic focusing device.

[0002]

2. Description of the Related Art Conventionally, a so-called "multi-point AF (autofocus) camera" is known in which focus states of a plurality of areas on a screen are detected and the focus of a photographing lens is adjusted based on the results. The plurality of focus-detectable areas on the screen are also referred to as “distance measuring points”.

Many AF cameras before the multi-point AF camera have only one distance measuring point in the center of the screen (hereinafter, such a camera is referred to as "one-point AF camera").

A so-called "passive AF method" for performing focus detection based on a light flux from a subject illuminated by natural light.
Then, it often happens that focus detection becomes impossible under the illumination condition of natural light or the contrast condition of the subject. Therefore, a light source for illuminating the subject is provided in the camera body, and the subject is illuminated as necessary to enable focus detection that is impossible under natural light. Such a light source is called "auxiliary light". A light emitting diode, a strobe device, an incandescent lamp, or the like is used as the auxiliary light source.

For example, as shown in FIG. 2, an auxiliary light projecting portion 11 is provided near the upper left portion of the camera body 10, and when the focus cannot be detected by natural light, the auxiliary light is emitted from the light projecting portion 11. To illuminate the subject.

In the case of a one-point AF camera, focus detection is performed only in the center of the screen, so the auxiliary light is also configured to illuminate only the central portion of the subject. It is configured to illuminate all the subject positions corresponding to a plurality of focus detection points on the screen.

The auxiliary light is also provided to an external strobe device as shown in FIG. In most cases, natural light is dark and the brightness is low. This is because the provision of the means (auxiliary light projecting unit 21) is more advantageous in terms of the amount of light on the space, and a farther subject can be illuminated.

Further, as shown in FIG. 2, since the strobe is farther from the photographing optical axis than the auxiliary light projecting unit 11 of the camera, there is an advantage that vignetting due to the lens barrel of the photographing lens does not easily occur.

Normally, the auxiliary light projecting section 21 is arranged below the strobe light emitting section 22. AF of camera is 1 point AF
In the era, the auxiliary light provided to the strobe only illuminates the central part of the screen, but as the camera becomes multi-point AF, the auxiliary light on the strobe side also has multiple points A as well as the auxiliary light of the camera.
It has become compatible with F.

When a multi-point AF-compatible strobe is installed in a multi-point AF camera, the strobe-side fill light is used instead of the camera-side fill light for the reason described above.

The auxiliary light on the camera side is used only when a strobe that does not support the multipoint AF is installed.

[0012]

However, even with a multi-point AF camera, focus detection is not always performed at a plurality of focus points, and focus detection is performed at only one of the focus points. There is a situation where the camera does not work. For example, when the user arbitrarily sets a focus detection point for focus detection.

In particular, when only the central distance measuring point is selectively selected, the AF function is exactly the same as the conventional one-point AF.

However, even in such a case, if the attached strobe is not compatible with the multi-point AF, the supplementary light on the side of the camera should be used in spite of the fact that the supplementary light on the side of the strobe has the above-mentioned advantages. Is used.

(Object of the Invention) An object of the present invention is to provide an optical device capable of improving the probability of enabling the focus detection operation.

[0016]

In order to achieve the above object, the present invention according to claim 1 is such that an illuminating means for illuminating an outside world corresponding to a predetermined area of a plurality of areas is attached to the optical device. In this case, when detecting the focus state of a predetermined area in the plurality of areas, the illumination means is used as auxiliary light at the time of focus detection.

In order to achieve the above-mentioned object, the present invention according to claim 2 is such that when a second illuminating means for illuminating the outside world corresponding to a plurality of areas in the screen is attached to the optical device. Is the first mode for detecting the focus state of at least two or more locations in the plurality of areas and the second mode for detecting the focus state of a predetermined area in the plurality of areas, When the second illuminating means is selected as auxiliary light at the time of focus detection, and the third illuminating means for illuminating the outside world corresponding to a predetermined area of the plurality of areas is attached to the optical device, In the first mode, the first illuminating means for illuminating the outside world corresponding to a plurality of regions in the optical device is used, and in the second mode, the third illuminating means is used as auxiliary light for focus detection. A means for selecting auxiliary light for selection is provided, and The present invention according to claim 3 is concerned with the result of the area selecting means that selects the area based on the line-of-sight detection result when the second illuminating means for illuminating the outside world corresponding to the plurality of areas is attached to the optical device. When the second illuminating means is selected as the auxiliary light at the time of focus detection and the third illuminating means for illuminating the outside world corresponding to a predetermined area of the plurality of areas is attached to the optical device. Illuminating the third illuminating means when the area selecting means selects the predetermined area, and illuminating the outside world corresponding to a plurality of areas in the optical device when the area selecting means selects a portion other than the predetermined area. 1
Auxiliary light selecting means for selecting each of the illuminating means as auxiliary light at the time of focus detection, and a third illuminating means for illuminating the outside world corresponding to a predetermined area of the plurality of areas is attached to the optical device. When detecting the focus state of a predetermined area in the plurality of areas, the third
This illumination means is used as auxiliary light at the time of focus detection.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in detail based on the illustrated embodiments.

FIG. 1 is a block diagram showing a circuit configuration of a camera according to the first embodiment of the present invention.

Microcomputer for camera (hereinafter,
A signal input circuit 10 for detecting various operation switch groups 114 of the camera
4. Motor drive circuit 106 for driving film feeding motor 116, photometric sensor 107, shutter control circuit 108 for controlling shutter magnets 118a and 118b, focus detection sensor 101, auxiliary light LED
The LED drive circuit 102 and the like for driving 112 are connected.

A signal 115 is transmitted to a photographing lens (not shown) via a lens communication circuit 105 to control focus and diaphragm.

Further, the signal 113 is transmitted / received to / from the strobe CPU 200 via the strobe communication circuit 103.

The strobe CPU 200 is a camera CPU
According to the instruction of 100, the strobe control circuit 201 is controlled to emit strobe light, and the LED driving circuit 202 is used to drive the strobe side auxiliary light LED 212.

Switch group 1 is used to set various modes of the camera.
It is determined by 14 settings.

Photometric sensor 107, shutter control circuit 1
Details of 08, the motor drive circuit 106, and the lens communication circuit 105 are not directly related to the present invention, and therefore, further description will be omitted.

In the CPU 100, a ROM storing a program for controlling the camera operation, and an R for storing variables
It has a built-in EEPROM (electrically erasable and writable memory) for storing AM and various parameters.

FIG. 2 is an external view showing a state in which a strobe is attached to the camera of FIG. 1 as described above.

FIG. 3 is a block diagram of a finder optical system and a focus detection system of the camera having the above configuration.

Most of the light flux from the subject incident through the taking lens 60 is reflected upward by the quick return mirror 30 and forms an image on the finder screen 51.
The user of the camera will observe this image through the pentaprism 52 and the eyepiece lens 53.

When taking a picture, the quick return mirror 30 jumps upward, and the luminous flux is taken by the photographic film 50.
An image is formed on the upper surface, and the subject image is exposed.

A part of the photographing light flux passes through the quick return mirror 30 and is bent downward by the rear sub-mirror 31, so that the field mask 32, the infrared cut filter 33, the field lens 34, the diaphragm 38, and the secondary imaging lens. An image is formed on the focus detection sensor 101 via 39. By processing an image signal obtained by photoelectrically converting this image, the photographing lens 6
A focus state of 0 can be detected.

The focus detection device in this embodiment uses a well-known phase difference detection method, and can detect the focus states of three different areas in the screen.

The detailed structure of the focus detection system is shown in FIG.

The light flux from the subject reflected by the sub-mirror 31 once forms an image near the visual field mask 32 in FIG.
The field mask 32 is a light shielding member for determining a focus detection area (distance measuring point) in the screen, and has a cross-shaped opening in the center and two vertically elongated openings on both sides.

The three lenses forming the field lens 34 correspond to the three openings of the field mask 32, respectively. A diaphragm 38 is arranged behind the field lens 34, and a pair of upper and lower openings are provided in the central portion, for a total of four openings.
Further, a pair of two openings are provided in the left and right peripheral portions, respectively.

The field lens 34 has a function of forming an image of each aperture of the diaphragm 38 near the exit pupil of the photographing lens 60.

A secondary image forming lens 39 is provided behind the diaphragm 38, and is composed of a total of eight lenses in four pairs, and each lens corresponds to each opening of the diaphragm 38.

The field mask 32, the field lens 34,
Each light beam that has passed through the diaphragm 38 and the secondary imaging lens 39 forms an image on the 4 to 8 sensor array on the focus detection sensor 101.

The relationship between the sensor array and the distance measuring points on the screen will be described with reference to FIGS.

The pair of sensor rows 111a and 111b are arranged on the distance measuring frame 81a in the finder 80 and the sensor rows 111c and 111b.
The pair d and the pairs 111e and 111f correspond to the distance measuring frame 81b, and the sensor rows 111g and 111h correspond to the distance measuring frame 81c.

By photoelectrically converting the image on each pair of sensor lines and detecting the relative positional displacement of the four pairs of image signals, the distance between the central portion on the screen in two vertical and horizontal directions, two peripheral locations, and three total locations is measured. The focus state of the point can be detected.

In the present embodiment, the distance measuring frame 8 in the center will be described below.
The area 1b is the "central distance measuring point", and the distance measuring frames 81 at the two surrounding areas.
The areas c and 81a may be referred to as "right focus area" and "left focus area", respectively, and the two peripheral focus areas may be referred to as "peripheral focus area". The central distance measuring point is represented by the result of the more reliable detection result of the two vertical and horizontal directions.

Next, the auxiliary light projecting optical system will be described with reference to FIGS. 7 and 8.

A pattern as shown in FIG. 8 is formed on the light emitting portion 122 on the auxiliary light LED 112.

The patterns 122a, 122c and 122e do not transmit light, and the patterns 122b and 122d transmit light. This pattern is projected onto the subject by the auxiliary light lens 70.

By projecting such a pattern onto the subject, the effect can be obtained not only when the luminance is low, but also when the focus cannot be detected due to the low contrast.

The auxiliary light projecting lens 70 is composed of four lenses as shown in FIG. 7, and can project the auxiliary light corresponding to the plurality of distance measuring points.

The central projection lenses 70a and 70d project the pattern shown in FIG. 8 onto an object located at the central distance measuring point. The left projection lens 70b corresponds to the left focus point, and the right projection lens 70c corresponds to the right focus point.

Therefore, when the auxiliary light LED 112 emits light, a pattern appears on the subject on each distance measuring point in the screen as shown in FIG. 9 (A).

By the way, FIG. 9B shows a screen when the conventional strobe auxiliary light which is not compatible with multi-points is used. As shown in FIG. 9, the auxiliary light pattern is generated only on the central focus detection point. do not do.

This auxiliary light projecting optical system can be mounted in a camera or a strobe with a similar structure.

The operation of the camera having the above configuration is shown in FIG.
A description will be given based on the flowcharts after 0.

When the AF operation is started, first, in step (S1), accumulation of the focus detection sensor 101 is started.
As the focus detection sensor 101, an accumulation type sensor is usually used, and the accumulation time changes depending on the brightness. When the predetermined accumulation is completed, the CPU reads out the image signal.

In this case, in this embodiment, the image signals of the four pairs of sensor arrays, that is, the three distance measuring points can be obtained. If it is not necessary to detect the focus at all the focus detection points, it is not necessary to store the focus detection points that are not used and to read out the image signal.

In the next step (S2), focus detection calculation is performed on the read image signal, and the focus state (defocus amount) of the three focus detection points is obtained.

If focus detection is not possible in step (S3), that is, focus detection is possible, step (S3)
It branches to 9) and determines whether or not the focus detection result is in-focus. If it is not still in focus, step (S1)
In 0), the focus is adjusted according to the defocus amount. In the case of focusing, it is not necessary to drive the lens as a matter of course.
Then, in step (S11), one AF control ends.

If the subject is not in focus, this series of AF controls may be repeated.

If focus detection is impossible in step (S3), the process branches to step (S4) to determine whether the cause of focus detection is low luminance. This determination may be made by referring to the accumulation time of the sensor accumulation in step (S1). When the accumulation time is longer than the predetermined time, it is determined that the brightness is low.

When it is determined that the brightness is low in the next step (S4), the process branches to step (S5) to execute a control subroutine for using the auxiliary light.

FIG. 11 shows the flow of this subroutine.

When the "use of auxiliary light" subroutine is called, first in step (S21), it is checked whether or not a strobe is attached to the camera. If a strobe is not attached, the process proceeds to step (S22). The auxiliary light from the camera is projected. On the other hand, when the strobe is attached, it is determined in step (S23) whether or not the attached strobe is compatible with multipoint AF. This determination is made by the camera CPU
100 is executed by communicating with the flash CPU 200. That is, the flash CPU 200 follows the camera CPU 100 according to a predetermined promise,
All you have to do is notify that it is a compatible strobe.

If the attached strobe is compatible with multi-point AF, the camera CPU 100 communicates with the strobe CPU 200 in step S26 so as to project multi-point AF-compatible auxiliary light on the strobe side. If the attached strobe is not compatible with multiple points, the process proceeds to step (S24).

In step (S24), a preset distance measuring point mode of the camera is checked, and (1) focus detection is executed at all the distance measuring points.

(2) Focus detection is performed at the central focus detection point.

(3) Focus detection is performed at the right distance measuring point.

(4) Focus detection is performed at the left focus detection point. Check which mode it is in.

If the above-mentioned (2) "Execute focus detection at central focus detection point" mode is set, the central focus detection point should be illuminated with auxiliary light even with strobe auxiliary light that does not support conventional multipoint AF. Therefore, in order to take advantage of the above-mentioned advantages of the strobe-side auxiliary light, in step (S25), multiple points A on the strobe-side are obtained.
Communication is performed so as to project auxiliary light not compatible with F.

Steps (S22), (S25),
The auxiliary light is projected in any of (S26), and this subroutine is returned in step (S27).

Returning to the flow of FIG. 10, step (S
When the auxiliary light is projected in 5), accumulation and reading of the focus detection sensor are executed in the next step (S6) as in step (S1).

Although not particularly described in the flow, the auxiliary light projected in step (S5) may be turned off when the accumulation of the sensor is completed.

In the next step (S7), the step (S
Perform the focus detection calculation of the read image signal in the same manner as 2),
In the next step (S8), it is determined whether focus detection is possible. If focus detection is possible, the process branches to step (S9), the focus determination of step (S9), step (S10).
The lens driving is performed appropriately.

If the focus cannot be detected, the focus cannot be determined and the lens cannot be driven, so step (S11).
And the AF control ends.

(Second Embodiment) Second Embodiment of the Present Invention
12 shows the operation of the main part of the camera according to the embodiment of FIG.
13 and the flowchart of FIG.

The second embodiment is an example in which the present invention is applied to a multi-point AF camera which detects a user's line of sight and determines a distance measuring point based on the line-of-sight information.

Various cameras provided with a so-called line-of-sight detecting device for detecting which position on the finder surface of the camera the user is gazing have been proposed, for example, Japanese Patent Application Laid-Open No. 1-241511 by the applicant of the present application. Then, the anterior segment of the user's eyeball illuminated by the infrared light emitting diode is imaged using the area sensor, the image signal is processed to detect the line-of-sight coordinates on the finder of the user, and the result One of the multiple focus points and photometric areas of the multi-point AF camera based on
A camera for selecting one is disclosed.

Now, when the AF control is started, the visual axis detection is executed in step (S31). The line-of-sight information of the user is detected in the form of coordinates on the finder, and the distance measuring point is selected based on which distance measuring point coordinate the line-of-sight coordinate is closest to. That is, if the detected line-of-sight coordinates are closest to the coordinates of the central focus detection point, the focus detection point selected by the visual line is determined to be the central focus detection point.

Now, when the distance measuring point is determined in this way,
The sensor corresponding to the distance measuring point is stored / read out. For example, referring to FIG. 5, assuming that the focus detection point selected by the line of sight is the center focus detection point, only the sensor rows 111c and 111d and 111e and 111f are controlled. Similarly, if the selected focus detection point is the left focus detection point, the pair of sensor rows 111a and 111b is controlled, and if it is the right focus detection point, the pair of sensor rows 111g and 111h is controlled.

Returning to the flow of FIG. 12, the step (S3
When the accumulation / readout of the sensor is completed in 2), the focus state of the read image signal is calculated. Then, after that, the same processing as that of the step (S3) and thereafter in FIG. 10 is executed.

When the auxiliary light is used in step (S5) of FIG. 10, the "use auxiliary light" subroutine of the flow shown in FIG. 13 is executed in this embodiment.

When this subroutine is called, first in step (S41), it is checked whether or not a strobe is attached to the camera. If a strobe is not attached, the process proceeds to step (S42) and the camera side Emit the auxiliary light.

If a strobe is attached, it is determined in step (S43) whether or not the strobe is compatible with multipoint AF. If the mounted strobe is compatible with multi-point AF, communication is performed so that the strobe-side auxiliary light is projected in step (S46). If the mounted lens does not support multipoint AF, the process proceeds to step (S44).

If the focus detection point selected by performing the line-of-sight detection in step (S31) of FIG. 12 is the central focus detection point, the central focus detection point can be illuminated even by the strobe auxiliary light that does not support conventional multipoint AF. Therefore, as described in the first embodiment, communication is performed so as to project the auxiliary light on the strobe side in step (S45).

Steps (S42), (S45),
The auxiliary light is projected in any of (S46), and this subroutine is returned in step (S47).

AF control after projection of the auxiliary light is exactly the same as that in FIG. 10, and therefore the description thereof is omitted.

According to each of the above embodiments, when the auxiliary light of the strobe attached to the multi-point AF camera does not support multi-point AF, the AF control of the camera detects the focus only at the central focus detection point. In such a situation as described above, by using the strobe-side auxiliary light, which has more advantages, it is possible to improve the probability of enabling the focus detection operation using the auxiliary light.

(Correspondence between Invention and Embodiment) In each of the above embodiments, the LED drive circuit 102 and the LED 11 are provided.
2 corresponds to the first illuminating means of the present invention, and the LED drive circuit 202, the LED 212, and the auxiliary light projecting lens 70 correspond to the second illuminating means of the present invention. In addition, the LED drive circuit 20
2, a strobe device (not shown) having an LED 212 and a light projecting lens (not shown) that projects only the light from the LED 212 is an illuminating means (claim 1) or a third illuminating means (claim 1) of the present invention. 2 and 3).

The portion for processing the operations shown in FIGS. 11 and 13 of the camera CPU 100 corresponds to the fill light selecting means of the present invention.

The above is the correspondence between each configuration of the embodiments and each configuration of the present invention, but the present invention is not limited to the configurations of these embodiments, and the functions shown in the claims,
It goes without saying that any structure may be used as long as the functions of the embodiments can be achieved.

(Modification) In each of the embodiments, an LED (infrared light emitting diode) is used as the illuminating means, but the present invention is not limited to this, and a strobe device, an incandescent lamp or the like may be used. Good.

Further, in each of the embodiments, an example in which the LED as the illumination means is arranged in the strobe device and mounted on the camera is shown, but only the illumination means is configured as one external device. Alternatively, it may be detachable from the camera.

Although the present invention has been described as applied to a single-lens reflex camera, the present invention can also be applied to cameras such as a lens shutter camera and a video camera. Furthermore,
It can also be applied to other optical devices, other devices, and constituent units.

[0092]

As described above, according to the present invention,
When the third illumination means for illuminating the outside world corresponding to a predetermined area of the plurality of areas is attached to the optical device, when detecting the focus state of the predetermined area of the plurality of areas, The third illumination means, which has more advantages, is used as auxiliary light at the time of focus detection.

Therefore, the probability of enabling the focus detection operation can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of a camera according to a first embodiment of the present invention.

FIG. 2 is a diagram showing appearances of a camera and a strobe shown in FIG.

3 is a configuration diagram of a finder optical system and a focus detection system of the camera of FIG.

FIG. 4 is a perspective view showing details of the focus detection system of FIG.

5 is a diagram showing a focus detection sensor included in the camera of FIG.

FIG. 6 is a view showing the inside of a viewfinder of the camera of FIG.

FIG. 7 is a perspective view showing an auxiliary light projecting optical system provided in the strobe device of FIG.

8 is a diagram showing a light projection pattern of the auxiliary light LED of FIG.

9 is a diagram showing a relationship between a distance measuring frame of the camera of FIG. 1 and a fill light pattern.

10 is a flowchart showing an AF operation of the camera of FIG.

FIG. 11 is a flowchart showing the operation in step (S5) of FIG.

FIG. 12A of a camera according to a second embodiment of the present invention
It is a flow chart which shows F operation.

FIG. 13 is a flowchart showing an operation when using auxiliary light of the camera of the second embodiment of the present invention.

[Explanation of symbols]

70 Auxiliary Light Projecting Lens 81a, 81b, 81c Distance-measuring Frame in Viewfinder 100 CPU for Camera 101 Sensor for Focus Detection 102 Auxiliary Light LED Driving Circuit in Camera 103 Strobe Communication Circuit 112 Auxiliary Light LED in Camera 200 CPU for Flash 202 Auxiliary light LED drive circuit in strobe 212 Auxiliary light LED in strobe

Claims (12)

[Claims] 1. An optical device capable of detecting a focus state of a plurality of regions in a screen, wherein an illuminating means for illuminating an outside world corresponding to a predetermined region of the plurality of regions is attached to the optical device. In addition, when detecting the focus state of a predetermined area in the plurality of areas, the illumination device is used as auxiliary light at the time of focus detection. 2. A focus detecting means for detecting a focus state of a plurality of areas in a screen, a first illuminating means for illuminating an outside world corresponding to the plurality of areas, and at least two or more locations of the plurality of areas. An optical device having a first mode for detecting a focus state of a plurality of areas and a mode selection unit for selecting one of a second mode for detecting a focus state of a predetermined area in the plurality of areas. When the second illuminating means for illuminating the outside world corresponding to is attached to the optical device, the second illuminating means is selected as auxiliary light at the time of focus detection regardless of the mode, and the plurality of regions are selected. When a third illuminating means for illuminating the outside world corresponding to a predetermined area in the optical device is attached to the optical device, the first illuminating means is used in the first mode and the third illuminating means is used in the second mode. Focus the third illumination means respectively Optical apparatus is characterized in that an auxiliary light selecting means for selecting as an auxiliary light when. 3. A focus detecting means for detecting a focus state of a plurality of areas in a screen, a first illuminating means for illuminating an outside world corresponding to the plurality of areas, and a sight line detecting means for detecting a sight line of a user. And an area selection unit that selects one of the plurality of areas based on the line-of-sight detection result, in a second illumination unit that illuminates the outside world corresponding to the plurality of areas. Is attached to the optical device, the second illuminating means is selected as auxiliary light at the time of focus detection regardless of the result of the area selecting means and corresponds to a predetermined area of the plurality of areas. When a third illuminating means for illuminating the outside world is attached to the optical device, the third illuminating means is used when the area selecting means selects the predetermined area, and the area selecting means is other than the predetermined area. When you select the first Bright means, optical apparatus characterized by respectively providing the auxiliary light selecting means for selecting as the auxiliary light when the focus detection. 4. The optical device according to claim 1, wherein the illumination unit is a light emitting diode. 5. The optical device according to claim 1, wherein the illumination unit is a strobe device. 6. The optical device according to claim 1, wherein the lighting unit is an incandescent lamp. 7. The optical device according to claim 1, wherein the illuminating means is arranged in a strobe device. 8. The optical device according to claim 2, wherein the first illuminating means, the second illuminating means, and the third illuminating means are light emitting diodes. 9. The optical device according to claim 2, wherein the first illuminating unit, the second illuminating unit, and the third illuminating unit are strobe devices. 10. The optical device according to claim 2, wherein the first lighting unit, the second lighting unit, and the third lighting unit are incandescent lamps. 11. The optical device according to claim 2, wherein the second illuminating unit or the third illuminating unit is arranged in a strobe device. 12. The optical device according to claim 1, wherein the predetermined area is a central area in the screen.