JPS63189816A - Auto-focusing device - Google Patents

Abstract

PURPOSE:To always keep a focusing state while the titled device is in zooming without using a coupling member such as a cam ring by controlling the driving speed of a correction lens on the basis of the focal distance information and focus inspecting result of an image pickup lens in zooming. CONSTITUTION:A variable power lens 2 and the correction lens 3 are driven by depressing a zoom key 11. The lens 3 is driven at a reference speed read out from a ROM by a processor on the basis of focal distance information at the position and information for a zooming direction 11. As to the reference speed, a speed for keeping ideal focusing is considered when an object positioned on an intermediate distance between the shortest distance and an infinite distance is zoomed in a certain direction on the basis of the delivered distance of the correction lens, a means value in each focal distance area is set up as a reference speed for driving the correction lens in the zooming direction within the area and two reference speeds in the telephoto direction and the wide angle direction are prepared in one focal distance area. In such constitution, focusing can be always kept also in zooming without using a cam ring or the like and the weight and size of an image pickup lens can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an automatic focus adjustment device suitable for a video camera equipped with a zoom function.

(Prior Art) In conventional zoom lenses, the distance between the variator lens and the compensator lens is generally regulated by a cam ring so that the imaging position of the subject light remains constant regardless of zooming. In such zoom lenses, focusing is done using the front lens.

On the other hand, U.S. Patent No. 2.782.683 discloses a technology that uses sliding resistance to detect the positions of the variator lens and compensator lens, and regulates the positional relationship between the variator lens and the compensator lens without using a cam ring. Although disclosed, a sliding resistance for lens position detection is required instead of the cam ring.

In addition, Japanese Patent Publication No. 52-15226 discloses that when zooming is performed after manual focusing, imaging plane compensation is performed by controlling the position of the focus lens according to the absolute focal length information of the zoom lens. Although such a zoom lens is disclosed, since it is not associated with an automatic focus adjustment device, it is necessary to focus manually and then zoom, and furthermore, the absolute focus of the zoom lens cannot be adjusted manually. Since it requires distance information and controls the position of the focus lens instead of controlling its drive speed, focusing during zooming cannot always be guaranteed.

(Problem to be Solved by the Invention) As described above, in a zoom lens, the distance between the variator lens and the compensator lens is regulated by a cam ring so that the imaging position of the subject light remains constant regardless of zooming. However, in order to make the lens smaller and lighter, it is desirable to ensure a focused state during zooming without using this cam ring.

Therefore, in zoom lenses for single-lens reflex cameras, the cam ring is eliminated, and the position of the compensator lens is controlled based on the focus detection results to maintain the relative position with the variator lens, and the compensator lens also performs focusing. Proposed. In this type of single-lens reflex camera, it is only necessary for the camera to be in focus when the shutter is released, and there is no need to maintain focus while zooming, so it is only necessary to control the position of the compensator lens based on the focus detection results. However, since a video camera performs zooming while taking pictures, it is required to maintain a focused state at all times even during zooming.

The present invention has been made in view of these points, and its purpose is to control the driving speed of a compensator lens for image forming plane compensation without using a connecting member such as a cam ring. To provide an automatic focus adjustment device that maintains a focused state even during zooming.

(Means for Solving the Problems) In order to achieve the above object, the automatic focusing device according to the present invention includes a variator lens for zooming and a compensator lens for compensating the imaging plane. A photographing lens that is included without a connecting member, a focus detection means that detects the focal state of the photographic lens by subject light that has passed through the photographic lens, and a focus detection means that drives a variator lens to change the focal length of the photographic lens during zooming. , control means for controlling the drive speed of the compensator lens based on the focal length information of the photographic lens and the focus detection result by the focus detection means.

(Function) In the present invention, during zooming to change the focal length of the photographic lens by driving the variator lens for variable magnification, the imaging plane compensation is performed based on the focal length information of the photographic lens and the focus detection result. Since the drive speed of the compensator lens is controlled, there is no need to use a connecting member such as a cam ring.
It is possible to always maintain a focused state even during zooming.

(Example) Examples of the present invention will be described below.

FIG. 1 is a diagram showing the overall configuration of an automatic focus adjustment device according to an embodiment of the present invention. In FIG. 0, lens groups 1 to 4 constitute a photographing zoom lens having a variable power function; Of these, 2 is a variator lens for variable power, and 3 is a compensator lens for focusing. 5 is a zoom encoder that reads the position of the variator lens 2;
The entire movement range of the variator lens 2 is divided into five focal length zones, and it is detected in which zone the variator lens 2 is located. 6 is a zoom motor for driving the variator lens 2, and 7 is an AF motor for driving the compensator lens 3. 8 is a focus detection unit, which performs focus detection using the subject light that has passed through the photographic lenses 1 to 4; 9 is a drive circuit, which controls the zoom motor 6 and AF by signals from the microprocessor 10;
Drive Momo-7. 11 is a zoom key (switch) operated for zooming.

Next, the configuration of the focus detection section 8 will be explained.

FIG. 2 shows the configuration of the focus detection unit 8 including the optical system, where 30 is a photographing lens, 31 is a relay lens, and 3
2 is a re-imaging lens, 33 is a COD line sensor, 34
is an aperture mask. The incident light that has passed through the photographic lens 30 is divided into two light beams by the aperture mask 34, and is imaged by the re-imaging lens 32 onto two areas, a standard part and a reference part, set on the CCD line sensor 33. As shown in Fig. 3, the distance between the two images formed on the CCD line sensor 33 is smaller than 1o in the case of the front focus, and larger than io in the case of the back focus, assuming that it is 10 when in focus. Become. Then, this image interval is approximately proportional to the amount of defrost debris. Therefore, by detecting this image interval,
It is possible to know whether the camera is in focus or out of focus, and if it is out of focus, it is possible to know the amount and direction of defocus. Therefore, for focusing when not zooming, the microprocessor 10 calculates the defocus amount based on the information from the focus detection section 8, and the AF momo-7 is moved to move the compensator lens 3 by a distance corresponding to the defocus amount. This is done by driving (see Figure 1).

Next, a method for maintaining a focused state during zooming will be described.

Figure 4 shows the variator lens 2 (hereinafter referred to as
The figure shows the relationship between the amount of movement of the variator (hereinafter referred to as a "variator") and the amount of movement of the compensator lens 3 (hereinafter referred to as a "convencator") for keeping the image plane position constant. However, regarding the subject distance, only the cases of 1 seagull and infinity are shown. Therefore, if the compensator can be driven and controlled so as to follow the curve in the figure, the in-focus state can be maintained even during zooming.

In FIG. 5, the curved line represents the ideal movement of the compensator to maintain focus during zooming, and the polygonal line represents an example of the actual movement of the compensator. If this polygonal line falls within a range close to the curve, a practical in-focus state will be maintained. Information for driving and controlling the compensator during zooming includes focal length, zooming direction, and focus detection result (defocus amount).

By the way, in the focus detection section 8, the COD line sensor 33
charge is accumulated (CCD integration) according to the amount of received light, and the microprocessor 10 performs focus detection calculation based on the result, so the zoom key 11 is turned on (time t=
to), the focus detection result is first obtained (
Time 1 in FIG. 5 = 1. ) will take some time. During this time, if only the variator is driven and the convencator is stopped, the focus will be greatly blurred.

Then, turn on the zoom key 11 (time t=to in Fig. 5).
), and at the same time as starting the driving of the variator, the driving of the compensator is also started. The driving speed of the compensator at that time is the basic speed read from the ROM of the microprocessor 10 based on the information from the zoom encoder 5 (focal length zone where the variator is located) and the information from the zoom key 11 (zooming direction). (Prepared for each focal length zone and zoom direction)
8 For example, when zooming in the wide direction, if the variator is in the third zone (see Figure 4), the ROM
From wide direction, basic speed of 3rd zone (+0.18+
++mm/5ee) is read as the drive speed of the compensator, and if the variator is in the 5th zone, read the basic speed (0, 25mm/5ee) of the 5th zone in the wide direction from the ROM.
5ee) is read and taken as the drive speed of the compensator. However, the sign indicates that the direction in which the compensator edges out is positive.

Here, to explain the value of the basic speed, the compensator extension amount in the 0 focus state is an intermediate value between the compensator extension amount at the shortest shooting distance and the compensator extension amount at the infinite shooting distance. When zooming in a certain direction to a subject at a distance, consider the ideal speed of the compensator to maintain ideal focus, and calculate the average value within each focal length zone for each It is taken as the basic speed of the compensator in its zooming direction in the focal length zone. Two basic speeds are prepared for one focal length zone: one for zooming in the tele direction and one for zooming in the wide direction.

Depending on the focal length zone, not only the sign of the basic speed of the compensator (compensator driving direction) but also the absolute value change depending on the zooming direction.
Since there is no further zooming in the telephoto direction from the telephoto end in the zone, the basic speed for zooming in the telephoto direction in the first zone is set close to the ideal compensator speed near the wide side in the first zone. The absolute value is different from the basic speed for wide direction zooming.

As can be seen from FIG. 4, the curve of the amount of movement of the compensator differs depending on the distance to the subject, so if the compensator continues to be driven at only the basic speed, it may go out of focus. Therefore, once focus detection results are obtained after zooming starts, the in-focus state is maintained by controlling the drive speed of the compensator based on the zooming direction, focal length zone, and focus detection results (defocus amount). do it like this. At this time, since the compensator continues to be driven during the CCD integration period, the CCD
If the defocus amount DI at the center time of the integration period is taken as a representative, the defocus amount D obtained at time 1=1+ is
I is time 1 corresponding to the time required for CCD integration and focus detection calculation.
= defocus amount at a time point before 11.

Since the variator continues to move during zooming, this defocus amount DI can be calculated from the lens position at time 1-11.
If you move the compensator by only 1, it will not be in focus. Here, the focus detection results are the defocus amount DI obtained at time 1=11 and the defocus amount DI-1 obtained at time 1=jl-. is used to control the drive speed of the compensator to maintain focus during zooming.

For example, speed control of the compensator will be explained by taking as an example a case where zooming is performed in the wide direction in the third zone. In Fig. 5, the curve represents the temporal change in the amount of compensator extension such that the light from the subject at a distance of 2 m from the photographic lens continues to form an image on the imaging surface during zooming, and the polygonal line represents the change in the amount of the compensator's movement over time such that the light from the subject at a distance of 2 m from the photographic lens continues to form an image on the imaging surface. It represents the change over time in the received amount of payout of the compensator.

When the zoom key (wide side) is pressed at time t=to,
At the same time as the variator starts to be driven in the wide direction, the compensator starts to be driven at the basic speed (0.18 m/5ee) for zooming in the third zone in the wide direction. Also,
The CCD line sensor 33 starts charge accumulation (CCD integration). After a time period corresponding to the subject brightness has passed, CCD integration is completed, and focus detection calculation is performed based on the data. At time t = t +, the focus detection result (defocus amount DI) is obtained.
Once obtained, the speed of the compensator is changed based on this defocus amount and the defocus amount D0 just before the start of zooming, and the time 1=1. when the next focus detection result is obtained. Drive the compensator at that speed until 0 time 1 = 1. When the defocus amount D2 is obtained as the focus detection result, the defocus amount D2 and time 1=
The speed of the compensator is varied based on the defocus value obtained in 1+. Continue the same procedure thereafter.

The above defocus amount Dt (i=o, 1.2...) is an amount converted to the amount of payout of the compensator, so
If the variator is at rest, the compensator can be moved out by DI to achieve complete focus. However, D
If I is within ±35μ, it can be considered as practical focus, so in reality, the compensator is not moved.In Figure 5, the defocus amount D0 just before starting zooming is +7μM, so it is possible to focus It performs zooming from a certain point and maintains focus while zooming.

The speed of the compensator is first determined by the microprocessor 1 depending on the zooming direction and focal length zone.
Select a data table like Table 1 from the ROM of 0, and calculate the latest defocus amount DI and the difference between this defocus amount DI and the defocus amount DI-1 obtained in the previous focus detection. (DI DI-+) reads the value in the table and sets the compensator speed.
For example, time t=1. The speed of the compensator between time t=t3 is selected by D2 and (D2 DI), that is, D+=+9 μm and D2=+13 μm, so the speed of the compensator is +〇, 25 v*va/
sec.

Table 2 shows compensator speed data when zooming in the telephoto direction in the third zone, under the same conditions as above (i.e., D I = +9 μm, Dz = +13
μ−), set the speed of the compensator to 0, 13 a
m/see. Tables 1 and 2 show the 3rd zone, but in other zones as well, the speed is determined based on the zooming direction, the current defocus amount, and the difference between the current and previous defocus amounts. is decided.

The values in the data table will be explained.

As shown in FIG. 5, in zooming in the third zone and wide direction, the ideal curve for the amount of payout of the compensator is upward sloping to the right. At times like this, (DI
If D +-+) = O, the line is nearly parallel to the curve; if (DI DI-+) > 0, the slope of the line is smaller than the curve; (D ID +-
+)<O, the slope of the polygonal line is greater than that of the curve. So on the data table,
For the same DI, the larger (DI DI-3) (on the right side in Table 1), the larger the compensator speed becomes. Also, if DI>O, it indicates that the actual compensator delivery amount is smaller than the ideal compensator delivery amount, and if DI is 0, the actual compensator delivery amount is smaller than the ideal compensator delivery amount. This indicates that the amount is larger than the amount of feed. Therefore, if the values of (DI DI-+) are the same on the data table, the larger the DI (in Table 1, the higher the value), the thicker the compensator speed value.

As mentioned above, (DI DI-+) indicates whether the slope of the polygonal line is larger or smaller than the slope of the curve, but even if (DI Dt-+) is the same, if the time interval of focus detection is short, the slope The difference will be large, and the longer the time interval, the smaller the difference in slope. Therefore, it is easier to control the speed of the compensator if the focus detection time interval is constant.
The time required for the amount of charge accumulated in the line sensor 33 to reach a sufficient amount to perform focus detection calculation becomes longer as the subject brightness is lower. Therefore, the time interval of focus detection during zooming is made constant as follows.

(i) During zooming, even when the subject brightness is low, 5O-
CCD integration is stopped at sec.

(ii> Subject brightness is high and C within 5 Q m5ec
When the CD integration is finished, a waiting time is provided for a length shorter than 5 Q 5 seconds.

The time required to perform focus detection calculations based on the results of CCD integration is approximately 5 Q m5e, including data transfer time, etc.
c, the focus detection cycle will be constant at about 100 m5ec if the above is done.

Since the angle of view changes during zooming, the subject light hitting the light receiving element also changes. Furthermore, when the aforementioned polygonal line is not substantially parallel to the curve, the amount of defocus also continues to change. Therefore, focus detection accuracy becomes lower than usual during zooming. Moreover, this tendency becomes stronger as the CCD integration time becomes longer. Therefore, if the CCD integration time during zooming is regulated to be short, there is an advantage that deterioration in focus detection accuracy due to the above-mentioned causes can be suppressed.

Although the subject brightness is low, there are cases where the CCD integration is stopped at 50 m5ec, making it impossible to detect the focus.
In such a case, drive the compensator at the basic speed to prevent it from deviating too much from the in-focus state. Even when the contrast of the subject is low and focus cannot be detected, the compensator is driven at the basic speed.

The overall operation will be explained using the flowchart shown in FIG. Hereinafter, the symbol "#" shall mean a step of the program. First, in #0, a focus detection calculation is performed based on CCD integration and its output. Next, in #1, the state of the zoom key is read, and the position of the variator is read in with the zoom encoder. In #2, it is determined whether the zoom key is pressed (ON).

If the zoom key is not pressed in #2, the variator and compensator are not driven (#12), focus detection is performed (#18), and the compensator is driven by the obtained defocus amount (#19). ), focus, and return to #O. This doesn't zoom.

This is the behavior in this case.

If the zoom key is pressed in #2, proceed to #3. If the zoom key is pressed for the first time, proceed to #4, and read from the ROM based on the focal length zone where the variator is located and the zooming direction. Set the basic speed.

Then, proceeding to #5, the variator is started to be driven at a predetermined speed, and at the same time, the compensator is started to be driven at the basic speed set in #4. Proceeding to #13, it is determined whether or not the focus result is possible based on the result of the focus comparison calculation in #0. If the focus can be detected, the process proceeds to #15, where focus detection is performed and the focal length zone and zooming direction are determined. The speed read from the data table on the ROM is set based on the defocus amount (#16).

If the focus cannot be detected due to low contrast of the subject, etc., the basic speed is set (#14). #17
Proceed to #16 or #14, drive the convencator at the speed set in #14, and return to #0. In #1, the zoom key and zoom encoder are sensed, and the zoom key is turned on.
If so (#2), this is the second time, so proceed from #3 to #6. If the zooming direction is the same as last time and the focal length zone where the variator is located is also the same as last time (#7),
Proceed to #13. If the zooming direction is opposite to the previous time in #6, proceed to #10 to read and set the basic speed corresponding to the current focal length zone and zooming direction from the ROM. Proceed to #11, drive the variator in the opposite direction to the previous time, and drive the convencator at the basic speed set in #10. Then, proceed to #13. If the zooming direction is the same as last time in #6 and the focal length zone is different from the previous time in #7, proceed to #8, and read the basic speed corresponding to the current focal length zone from the ROM. set.

Proceed to #9 and drive the convencator at the speed set in #8. Then, the process advances to #13, and the steps after #13 are the same as the previous time, and the above-described processing is continued.

Next, according to the flowchart in FIG. 7, #0 in FIG.
We will explain the time regulation for focus detection in . #21
At this point, charge accumulation in the CCD line sensor is started, and time counting of focus detection time is started.

When the subject brightness is high and the amount of charge accumulation exceeds the reference level within 50 tasec (#22, #23), charge accumulation is terminated at that point (#28).

Figure 8 is a diagram showing the change in the amount of charge accumulation over time, and as the subject brightness decreases, the 0 curve ■, which draws curves like ■, ■, ■, becomes 50 m5ec as described above.
This is an example of a case where charge accumulation is completed within a certain period of time.

If the amount of charge accumulation does not exceed the reference level even after 50m5ec has elapsed, proceed to #24, and if zooming is in progress,
Terminates charge accumulation regardless of the amount of charge accumulation (#28 >
, if zooming is not in progress, proceed to #25 and multiply the amount of accumulated charge by a predetermined value S. When it exceeds the reference level, that is, if the COD output is amplified by an amplifier circuit (not shown), focus detection calculation is performed. When sufficient information is obtained, charge accumulation is terminated. FIG. 8 shows an example of the case where the curve ■ is shown above.

If the amount of charge accumulation is insufficient to the reference level even after amplification, proceed to #26 and continue charge accumulation until 200 m5ec has passed (#27). In Fig. 8, the curve ■
is an example in this case. However, if it is determined in #26 that the amount of charge accumulation has exceeded the reference level before 200 ssec has elapsed, charge accumulation is terminated at that point.

After completing the charge accumulation (#28), proceed to #29 and perform focus detection calculation. After the focus detection result is obtained, the time is set at 4RBF-Jl, HL Gi, Kinbushi-Omon or IH Pu-Utsu 1. One focus detection is completed when 100 m5ec has passed from the start of counting #30, #31
), if zooming is not in progress, one focus detection is completed.

(Effects of the Invention) As described above, the present invention provides the following advantages:
Since the driving speed of the compensator lens for image plane compensation is controlled based on the focal length information of the photographing lens and the focus detection results, the driving speed of the compensator lens for image forming plane compensation is controlled at all times even during zooming without using a connecting member such as a cam ring. The in-focus state can be maintained, which has the effect that a photographic lens having a zoom function can be made lighter and smaller.

As described in the description of the embodiment, the integration time of the focus detection COD is regulated short during zooming, and
By aligning the focus detection cycles to a constant time, focusing accuracy can be improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the overall configuration of an automatic focus adjustment device according to an embodiment of the present invention, FIG. 2 is a diagram showing the configuration of a focus detection section used in the same, and FIG. 3 is a diagram showing the focus by the focus detection section same as the above. An explanatory diagram of the detection state; FIG. 4 is an explanatory diagram showing the relative positions of the variator and compensator in the photographic lens used in the above; FIG. 5 is an explanatory diagram of drive control of the compensator;
FIGS. 6 and 7 are flowcharts showing the operation of the automatic focus adjustment device as described above, and FIG. 8 is a diagram showing temporal changes in the amount of charge accumulated in the light receiving element used in the focus detection section as described above. 2 is a variator lens, 3 is a compensator lens, 8
is a focus detection section.

Claims (8)

[Claims] (1) A photographic lens that includes a variator lens for variable magnification and a compensator lens for image plane compensation without a connecting member, and a focal point that detects the focal state of the photographic lens based on the subject light that has passed through the photographic lens. A control means for controlling the driving speed of the compensator lens based on the focal length information of the photographing lens and the focus detection result by the focus detection means during zooming which changes the focal length of the photographic lens by driving the detection means and the variator lens. An automatic focus adjustment device comprising: (2) The automatic focus adjustment device according to claim 1, wherein the current defocus amount by the focus detection means is used as the focus detection result. (3) The automatic focus adjustment device according to claim 2, wherein the current and previous defocus amounts by the focus detection means are used as the focus detection results. (4) The automatic focus adjustment device according to claim 2, wherein the current defocus amount by the focus detection means and the difference between the current and previous defocus amounts are used as the focus detection result. (5) A photographic lens that includes a variator lens for zooming and a compensator lens for image plane compensation without a connecting member, and a focal point that detects the focal state of the photographic lens based on the subject light that has passed through the photographic lens. During zooming, the driving speed of the compensator lens is determined based on the focal length information of the photographing lens, the zooming direction, and the focus detection result by the focus detection means. An automatic focus adjustment device comprising: control means for controlling. (6) The automatic focus adjustment device according to claim 5, wherein current focus detection data and previous focus detection data by the focus detection means are used as focus detection results. (7) The focus detection means has a charge accumulation type light receiving element for focus detection, and is configured to regulate the charge accumulation time of the light receiving element to be shorter than in normal times during zooming. An automatic focus adjustment device according to claim 5. (8) The automatic focus adjustment device according to claim 7, wherein the focus detection means is configured to obtain focus detection data at regular intervals during zooming.