JP2921898B2 - Camera with zooming mode between exposures - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a camera provided with or capable of being mounted on a power zoom lens, and more specifically, to a camera provided with a during-exposure zoom mode capable of zooming between exposures.

“Prior art and its problems” Recent cameras have automated various photographing techniques. For example, there is zooming during exposure in which power zooming is performed during exposure.

However, in a normal zoom lens, the open F value (open aperture value) changes in proportion to the focal length. FIG. 4 shows the relationship between the focal length f and the open F value. The focal length f and the open F value are in a certain proportional relationship.

Since the open F value changes according to the focal length f in this manner, the amount of exposure to the film surface changes according to the F value, causing exposure unevenness.

OBJECT OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the related art. The purpose is to provide.

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a camera provided with a power zoom lens having an F value that fluctuates due to zooming, and has a during-exposure zooming mode for performing zooming during exposure. It is characterized in that it comprises a control means for adjusting the zooming speed in accordance with the F value which fluctuates due to zooming.

According to this configuration, even when zooming during exposure is performed by a zoom lens whose opening F-number fluctuates due to zooming, an image that changes due to zooming is exposed at a constant intensity, thereby eliminating exposure unevenness.

"Examples of the Invention" The present invention will be described below based on illustrated examples. FIG. 1 is a block diagram showing only a main configuration of a single-lens reflex camera having a during-exposure zoom mode of the present invention. This single-lens reflex camera includes a power zoom lens, an automatic focusing device, and an automatic exposure device.

The zoom lens 10 has two lens groups L1 and L2.
A plurality of roller pins 11 and 12 are fixed radially around the outer circumference of the first and second lens units L1, respectively. Each of the roller pins 11 and 12 is provided with a cam groove 13 formed in a cam ring 13.
a, 13b fits. Of the roller pins 11 and 12 in each group,
At least one of each group fits in a linear guide groove formed in the fixed lens barrel 14.

An annular gear 15 is fixed to an outer peripheral surface of the cam ring 13, and a pinion 16 a of a zoom motor 16 meshes with the gear 15. Therefore, the cam ring 13 is
To perform zooming by moving the first and second lens units L1 and L2 toward and away from each other in the optical axis direction. The relationship between the open aperture F value and the focal length f in the entire zooming area of the zoom lens 10 is the same as that shown in FIG.

On the outer peripheral surface of the cam ring 13, a decoder 17 for detecting the position of the cam ring 13 and obtaining the focal length f is provided. The signal read by the decoder 17 is output to the lens CPU 18. The lens CPU 18 calculates the focal length f and the corresponding open F value based on the output from the decoder 17 and outputs these to the control circuit 24 of the camera body 20.

Incidentally, reference numeral 19 in the drawing denotes a zoom operation ring for manually performing zooming.

The control circuit 24 is usually constituted by a microcomputer, and drives the zoom motor 16 according to a program stored in an internal ROM to perform zooming.

A part of the subject light beam passing through the lens groups L1 and L2 is transmitted through the half mirror portion of the main mirror 21, reflected by the sub mirror 22, and guided to the CCD distance measuring sensor. The CCD distance measuring sensor 23 is of a phase difference detection type, and outputs phase difference information of a subject image divided into two to a control circuit 24. The control circuit 24
Based on the phase difference information, a predictor calculation is performed to obtain a defocus amount and a focusing operation is performed, but the mechanical configuration is not shown.

The camera body 20 includes a distance measurement (photometry) switch SWS for starting photometry and automatic focusing operation, a mirror 21, a release switch SWR for driving a shutter and an aperture (not shown) to start exposure, and a zooming mode during exposure. Are provided, and these are connected to the input port of the control circuit 24.

In the present embodiment, the during-exposure zoom mode is provided as a photographing function, and the during-exposure zoom mode is selected by the mode selection switch SWM. In the during-exposure zoom mode, one of zooming to the telephoto side and zooming to the wide-angle side can be selected by the switch SWT or SWW. The zoom lens 10 may be zoomed to the wide-angle side when at the telephoto end, zoomed to the telephoto side when at the wide-angle end, or zoomed to the opposite side when the focal length at the start of exposure is at the wide-angle end or the telephoto end. Good.

Next, the during-exposure zoom mode of the present invention will be described. When zooming the zoom lens 10 from the focal length f ₀ to the focal length f _n, the open F value, as shown in FIG. 5 is changed from F ₀ to F _n. Therefore, in this embodiment, the zooming speed is increased on the wide-angle side where the open F value is small (bright), and the zooming speed is decreased on the telephoto side where the open F value is large (dark). Due to this speed change, the intensity of light incident on the film surface is constant in the entire zooming area, that is, the exposure amount is constant.

This change in the zooming speed can be achieved by changing the rotation speed of the zoom motor 16 or by changing the contour of the cam grooves 13a and 13b of the cam ring 13 while keeping the rotation speed of the zoom motor 16 constant.

The speed of the zoom motor 16 can be adjusted by changing the pulse period when the zoom motor 16 is constituted by a pulse motor, or by changing the voltage when the zoom motor 16 is constituted by a DC brush motor. In this case, the rotation speed R at each focal length f may be R = g (F) R ₀ .

Here, R ₀ is the rotation speed at the wide-angle end, g (F) = 1 /
2 ^{(logF-logF0) / log2} .

 This relationship is shown graphically in FIG.

When the rotation speed of the zoom motor 16 is kept constant, the zooming speed is made variable by changing the contours of the cam grooves 11a and 12b. In this case, the focal length scale width is H = h (f) H ₀ .

Here, H ₀ is the scale width near the wide-angle end, and h 0
(F) = 2 ^{(logF−logF0) / log2} .

FIG. 4 shows an example of the distance scale under this condition.
FIG. 6 shows a distance scale when the amount of change in the focal length with respect to the rotation angle of the zoom operation ring 13 is constant. The distances l _{1 to} l ₄ of the distance scale shown in FIG. Can be determined by:

As described above, according to the during-exposure zoom photographing camera of the present embodiment, since the zooming speed is changed according to the change in the F value,
Exposure can be performed at a constant exposure amount at any focal length during exposure.

[Effects of the Invention] As described above, according to the camera having the during-exposure zoom mode of the present invention, in a power zoom lens in which the F value changes due to zooming, the zooming speed changes according to the changing F value. Exposure is performed at a constant light intensity irrespective of the distance, and shooting without uneven exposure can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of an embodiment in which the present invention is applied to a single-lens reflex camera equipped with a power zoom lens, an automatic focusing device, and an automatic exposure device. FIG. 2 is a zoom diagram of the embodiment. FIG. 3 is a graph showing the relationship between the rotation speed R of the motor and the focal length f; FIG. 3 is a graph showing the relationship between the focal length scale width and the focal length f of the embodiment; FIG. FIG. 5 is a graph showing the relationship between the focal length f and the open F-number in the conventional zoom lens. FIG. 6 is a graph showing the relationship between the focal length f and the rotation angle of the zoom operation ring. This is a focal length scale when the amount of change is constant. 10 ... Zoom lens, 13 ... Cam ring, 16 ... Zoom motor, 17 ... Decoder, 18 ... Lens CPU, 20 ... Camera body, 24 ... Control circuit (microcomputer).

Claims (2)

(57) [Claims] 1. A camera provided with a power zoom lens whose F value changes by zooming, wherein the camera has a during-exposure zoom mode in which zooming is performed during exposure, and a zooming speed during exposure is changed to an F value which changes by zooming. A camera having a during-exposure zoom mode, comprising: a control unit that adjusts according to the condition. 2. The camera provided with the during-exposure zoom mode according to claim 1, wherein said control means increases the F value so that the during-exposure zoom speed increases as the F value decreases. A camera with an inter-exposure zoom mode that keeps the exposure constant by adjusting it sometimes to be slow.