Image capturing apparatus, light metering method, luminance calculation method, and program

• US 7,916,209 B2
• Filed: 03/05/2008
• Issued: 03/29/2011
• Est. Priority Date: 03/19/2007
• Status: Expired due to Fees

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Asoma, Akira
• Primary Examiner(s): Tran; Sinh
• Assistant Examiner(s): BERARDESCA, PAUL M
• Application Number:
  US12/042,746
• Publication Number:
  US 20080231728A1
• Time in Patent Office: 1,119 Days
• Field of Search: 348/362
• US Class Current: 348/362
• CPC Class Codes: G03B 7/093 for control of exposure time
• CPC Class Codes: H04N 23/73 by influencing the exposure time
• CPC Class Codes: H04N 23/741 by increasing the dynamic range of the image compared to the dynamic range of the electronic image sensors

Abstract

An image capturing apparatus includes: an image capturing processing unit capable of selectively performing a normal image capturing process in a normal image capturing mode and a combined image capturing process in a combined image capturing mode, the normal image capturing process being a process of obtaining a single exposure image signal in a unit period and generating captured image data by performing signal processing upon the obtained signal, and the combined image capturing process being a process of obtaining a long-exposure image signal and a short-exposure image signal and generating captured image data by performing signal processing including signal combination upon these obtained signals; a detection unit for performing light metering upon the captured image data; and a control unit for controlling switching between light metering methods used in the detection unit in accordance with an image capturing mode used.

Claims

1. An image capturing apparatus comprising:

an image capturing processing unit configured to selectively perform

a normal image capturing process in a normal image capturing mode to obtain a single exposure image signal and to generate captured image data by performing signal processing upon the single exposure image signal, and

a combined image capturing process in a combined image capturing mode to obtain a long-exposure image signal by exposure for a long period and a short-exposure image signal by exposure for a short period and to generate captured image data by performing signal processing including signal combination processing upon the long-exposure image signal and the short-exposure image signal, the long exposure period being longer than the short exposure period;

a detection unit configured to perform one of center-weighted light metering, evaluative light metering, and averaging light metering on the captured image data generated by the image capturing processing unit; and

a control unit configured to cause the detection unit to perform one of center-weighted light metering and evaluative light metering when the image capturing processing unit is in the normal image capturing mode and to perform averaging light metering when the image capturing processing unit is in the combined image capturing mode.

2. The image capturing apparatus according to claim 1, wherein the control unit performs exposure control for the image capturing processing unit on the basis of a result of the light metering performed by the detection unit.

3. The image capturing apparatus according to claim 1, wherein, when an instruction for the use of a partial area metering method is received during performance of the normal image capturing process in the normal image capturing mode or performance of the combined image capturing process in the combined image capturing mode, the control unit causes the detection unit to use a partial area light metering method.

4. The image capturing apparatus according to claim 1, wherein, when an abnormal condition is detected during performance of the normal image capturing process in the normal image capturing mode or performance of the combined image capturing process in the combined image capturing mode, the control unit causes the detection unit to use a partial area metering method.

5. The image capturing apparatus according to claim 1, wherein the detection unit divides the captured image data into detection frames according to the light metering method selected by the control unit, and outputs to the control unit a luminance integrated value for each frame.

6. The image capturing apparatus according to claim 1, wherein the control unit receives from the detection unit luminance integrated values for detection frames corresponding to the selected light metering method, calculates an average luminance level per unit area of the captured image data, calculates a difference between the average luminance level per unit area of the captured image data and a target average luminance level per unit area, and performs exposure control based on the calculated difference.

7. The image capturing apparatus according to claim 1, wherein the detection unit performs averaging light metering by selecting the entire captured image data as a single detection frame, calculating a luminance integrated value of the detection frame, and outputting the calculated luminance integrated value to the control unit.

8. A light metering method for an image capturing apparatus including an image capturing processing unit configured to selectively perform a normal image capturing process in a normal image capturing mode to obtain a single exposure image signal to generate captured image data by performing signal processing upon the single exposure image signal, and a combined image capturing process in a combined image capturing mode to obtain a long-exposure image signal by exposure for a long period and a short-exposure image signal by exposure for a short period shorter than the long period and to generate captured image data by performing signal processing including signal combination processing upon the long-exposure image signal and the short-exposure image signal, the light metering method comprising:

selecting one of center-weighted light metering and evaluative light metering to be performed on the captured image data generated by the image capturing processing unit when the image capturing processing unit is in the normal image capturing mode; and

selecting averaging light metering to be performed on the captured image data generated by the image capturing processing unit when the image capturing processing unit is in the combined image capturing mode.

9. A luminance calculation method for an image capturing apparatus that includes,

an image capturing processing unit configured to selectively perform a normal image capturing process in a normal image capturing mode to obtain a single exposure image signal and to generate captured image data by performing signal processing upon the single exposure image signal, and a combined image capturing process in a combined image capturing mode to obtain a long-exposure image signal by exposure for a long period and a short-exposure image signal by exposure for a short period shorter than the long period and to generate captured image data by performing signal processing including signal combination processing upon the long-exposure image signal and the short-exposure image signal, and a detection unit configured to perform one of center-weighted light metering, evaluative light metering, or averaging light metering on the captured image data generated by the image capturing processing unit, the luminance calculation method comprising:

selecting one of center-weighted light metering and evaluative light metering to be performed by the detection unit when the image capturing processing unit is in the normal image capturing mode;

selecting averaging light metering to be performed by the detection unit when the image capturing processing unit is in the combined image capturing mode;

receiving a value obtained by light metering performed by the detection unit; and

performing computation using the received value based on the light metering method performed in the detection unit to calculate a luminance value per unit area of the captured image data.

10. A non-transitory computer readable storage medium storing computer readable instructions thereon which, when executed by a computer, cause the computer to perform a luminance calculation method for an image capturing apparatus that includes, an image capturing processing unit configured to selectively perform a normal image capturing process in a normal image capturing mode to obtain a single exposure image signal and to generate captured image data by performing signal processing upon the single exposure image signal, and a combined image capturing process in a combined image capturing mode to obtain a long-exposure image signal by exposure for a long period and a short-exposure image signal by exposure for a short period shorter than the long period and to generate captured image data by performing signal processing including signal combination processing upon the long-exposure image signal and the short-exposure image signal, and a detection unit configured to perform one of center-weighted light metering, evaluative light metering, and averaging light metering on the captured image data generated by the image capturing processing unit, the luminance calculation method comprising:

selecting one of center-weighted light metering and evaluative light metering to be performed by the detection unit when the image capturing processing unit is in the normal image capturing mode; and

selecting averaging light metering to be performed by the detection unit when the image capturing processing unit is in the combined image capturing mode;

receiving a value obtained by light metering performed by the detection unit; and

performing computation using the received value based on the light metering method performed in the detection unit to calculate a luminance value per unit area of the captured image data.