JPH0746912Y2 - Camera with zoom function - Google Patents

Description

[Detailed Description of the Invention] (a) Field of Industrial Application The present invention relates to a camera with a zoom function.

(B) Conventional technology In electronic still cameras, compact cameras, etc., an imaging lens system and a finder lens system are generally provided separately, and compared to a single-lens reflex camera that requires a mirror-up mechanism, etc. It is composed. With a camera with such a configuration, for metering to obtain an appropriate exposure value,
An external photometry method is often used to measure the light of the part that does not pass through the imaging lens system.

Regarding such a photometric method used for electronic still cameras, film cameras, etc.
It is described on pages 108 to 109 of the September 1986 issue of [Published by a photographer].

(C) Problems to be solved by the invention Some external photometric cameras have a zoom function. When the zoom ratio changes, the range to be imaged also changes, so the appropriate exposure value also changes, but these cameras generally require a mechanism that corrects the exposure value according to the change in the zoom ratio. If not provided, the exposure value obtained by photometry may deviate slightly from the optimum exposure value.
In an electronic still camera or the like that uses a CCD (solid-state image sensor), the influence of exposure deviation on a captured image becomes significant.

In a camera provided with an image pickup lens system and a viewfinder lens system separately, a camera having a zoom function usually has a configuration in which the zoom ratio of the viewfinder lens system also changes according to the change of the zoom ratio of the image pickup lens system. ing.
Therefore, in these cameras, when the zoom ratio changes, a half mirror etc. is provided in the viewfinder lens system so that the optimum exposure according to the change of the zoom ratio can be obtained.
It is conceivable that the configuration is such that the light passing through the finder lens system whose zoom ratio is changing is measured according to the change of the zoom ratio of the imaging lens system.

However, the zoom lens used in the image pickup lens system originally has a different zoom ratio. It is designed so that the F value does not change easily, but the finder lens system, like the image pickup lens system, also changes the F value depending on the zoom ratio so that more appropriate exposure can be obtained from light passing through the finder lens system. In order to make such a configuration, it is necessary to design the lens system according to it, which causes a problem that the lens system becomes complicated and the viewfinder diameter becomes large.

The present invention is a camera with a zoom function in which an image pickup lens system and a finder lens system are separately provided, and by measuring light passing through the finder lens system, an optimum exposure value according to a change in zoom ratio is obtained. Therefore, an object of the present invention is to provide a camera with a zoom function that does not need to optically correct the F value of the finder system.

When a half mirror or the like is provided in the image pickup lens system to measure light passing through the image pickup lens system, a mechanism for retracting the half mirror at the time of image pickup so that the half mirror does not affect the picked up image. There is a problem in that it becomes necessary and the configuration becomes complicated.

(D) Means for Solving the Problems The present invention provides an imaging lens system capable of changing an imaging zoom ratio, a finder lens system having a finder zoom ratio which changes in association with a change in the imaging zoom ratio, and A photometric unit that measures light passing through a finder lens system and derives a photometric value, a zoom ratio detection unit that detects the imaging zoom ratio, and an F value of the imaging lens system that changes according to the zoom ratio and the F value. A storage unit that stores in advance the relationship with the F value of the finder lens system, and the storage unit is referred to, and the photometric value is determined according to the imaging zoom ratio detected by the zoom light detection unit. And a correction unit that corrects the ratio of light passing therethrough to be substantially equal to that measured.

(E) Action Since the present invention is configured as described above, the finder lens system uses a lens system in which the F value changes according to the change of the finder zoom ratio, and further, the light passing through the finder lens system is Even in the case of the photometric configuration, the photometric value is corrected by the correction means, and a photometric value substantially equivalent to that of light passing through the image pickup lens system is obtained.

(F) Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a main portion relating to a photometric value correction function in the camera with a zoom function of the embodiment.

In the figure, (1) is an imaging lens system capable of changing the zoom ratio (imaging zoom ratio), and is designed so that the F value does not easily change even if the zoom ratio changes. The imaging lens system (1) is driven by a driving means (13) including a pulse motor (11) and a motor driver (12), and its zoom ratio is changed. (2) is a viewfinder lens system in which the zoom ratio (finder zoom ratio) changes in conjunction with the change in the zoom ratio of the imaging lens system (1). The zoom ratio of the finder lens system changes so that an image substantially equivalent to the image captured by the imaging lens system can be obtained as the field of view of the finder. The viewfinder lens system (2) is small and lightweight, but has no optical F value correction, so that the F value also changes according to the change in image size due to the change in zoom ratio. . (2
1) is a half mirror provided in the finder lens system, and guides a part of the light after passing through the zoom lens (22) to the photodiode (3). Therefore, it is possible to perform photometry on a range substantially equivalent to the image captured by the imaging lens system (1). The light incident on the photodiode (3) is converted into photometric data (photometric value) by the detection circuit (4) and the A / D converter (5) and supplied to the correction means (6) in the microcomputer (9). To be done. The half mirror (21), the photodiode (3), the detection circuit (4), and the A / D converter (5) constitute a photometric means.

Reference numeral (10) is a ROM (storage means) in which the relationship between the F value of the imaging lens system (1) and the F value of the finder lens system (2), which changes according to the zoom ratio, is stored in advance. As described above, since the F value of the image pickup lens system (1) hardly changes, the ROM (10) is used in this embodiment.
In order to correct the F value of the finder lens system (2), which changes according to the zoom ratio of the imaging lens system (1), to a value equivalent to the constant F value of the imaging lens system (1) at all times. Required correction values are stored as a table. The microcomputer (9) includes a drive control means (8), a zoom ratio detection means (7), a correction means (6) and the like. The drive control means (8) controls the drive of the drive means (13), and also controls the number of pulses sent to the pulse motor (11).
Information such as the rotation direction of the pulse motor (11) is supplied to the zoom ratio detecting means (7). Zoom ratio detecting means (7)
Detects the zoom ratio based on the supplied information and derives it to the correction means (6). The correction means (6) reads a correction value according to the zoom ratio from the ROM (10), and based on the correction value, the photometric data supplied from the A / D converter (5) is equivalent to that of the image pickup lens system (1). It is corrected to a photometric value obtained when photometry is performed at the F value, and is derived as corrected photometric data. As described above, photometry is performed through the finder lens system (2) for a range substantially equivalent to the image captured by the imaging lens system (1), and the F value of the finder lens system (2) relating to the photometry. Is always regarded as being equal to the F value of the image pickup lens system (1), and therefore, with the above-described configuration, a photometric value substantially equal to that for measuring light passing through the image pickup lens system (1) is used as the corrected photometry data. can get.

The image pickup lens system (1) and the finder lens system (2)
When the characteristics related to the photometry other than the F value are different, the configuration may be such that the corrected photometry data is further corrected as necessary.

Further, in the above example, the F number of the imaging lens system (1) is
It is necessary for ROM (10) to always correct the changing F value of finder lens system (2) to the same value as the constant F value of image pickup lens system (1), regardless of zoom ratio. Strictly speaking, since the F value of the image pickup lens example (1) slightly changes according to the zoom ratio, the correction value in consideration of this change is stored in the ROM (10). It may be configured to be stored.

Furthermore, if the characteristics related to photometry other than the F-number differ between the imaging lens system (1) and the finder lens system (2) described above, store the data required for correction in the ROM (10). The correction may be performed based on this data.

In the present embodiment, the finder lens system has been described as a structure in which the optical F value is not corrected with respect to the change of the zoom ratio, but the lens system with the corrected F value may be used. Of course.

(G) Effect of the Invention As described above, according to the present invention, in a camera with a zoom function in which an imaging lens system and a finder lens system are separately provided, by measuring light passing through the finder lens system. , You can get the optimum exposure value according to the change of zoom ratio.
Since it is not necessary to optically correct the value, the viewfinder lens system is not complicated and the viewfinder diameter is not increased, so that the size and weight can be reduced, and the effect is great.

[Brief description of drawings]

FIG. 1 is a block diagram of a camera with a zoom function according to an embodiment. (1) ... Imaging lens system, (2) ... Viewfinder lens system, (3) ... Photodiode (photometric means),
(4) ... Detection circuit (photometric means), (5) ... A / D converter (photometric means), (6) ... correction means, (7) ...
Zoom ratio detection means, (10) ... ROM (storage means), (2
1) …… Half mirror (photometric means).

Claims (1)

[Scope of utility model registration request] 1. An image pickup lens system capable of changing an image pickup zoom ratio, a viewfinder zoom ratio being changed in association with a change in the image pickup zoom ratio, and a change characteristic of an F value with respect to the image pickup zoom ratio being the image pickup lens. In a camera with a zoom function including a viewfinder lens system having a different F-number change characteristic with respect to the image pickup zoom ratio in the system, a photometric unit for deriving a photometric value obtained by photometry of light passing through the viewfinder lens system; A zoom ratio detecting means for detecting a ratio, and a relationship between an F value change characteristic of the image pickup lens system with respect to the image pickup zoom ratio and a F value change characteristic of the finder lens system with respect to the image pickup zoom ratio is stored in advance as a correction value. And a correction value from the storage unit according to the imaging zoom ratio. A camera with a zoom function, comprising a correction unit that corrects the photometric value so as to be substantially equal to the photometric value when light passing through the imaging lens system is measured.